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1.  Implications of HIV PrEP Trials Results 
Abstract
Six randomized clinical trials have been implemented to examine the efficacy of tenofovir disoproxil fumarate (TDF) and/or TDF/emtricitabine (TDF/FTC) as preexposure prophylaxis for HIV-1 infection (PrEP). Although largely complementary, the six trials have many similar features. As the earliest results become available, an urgent question may arise regarding whether changes should be made in the conduct of the other trials. To consider this in advance, a Consultation on the Implications of HIV Pre-Exposure Prophylaxis (PrEP) Trials Results sponsored by the Division of AIDS (DAIDS) of the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and the Bill and Melinda Gates Foundation (BMGF) was held on January 29, 2010, at the Natcher Conference Center, NIH, Bethesda, MD. Participants included basic scientists, clinical researchers (including investigators performing the current PrEP trials), and representatives from the U.S. Food and Drug Administration (FDA) and the agencies sponsoring the trials: the U.S. Centers for Disease Control and Prevention (CDC), the U.S. Agency for International Development (USAID), the BMGF, and the U.S. NIH. We report here a summary of the presentations and highlights of salient discussion topics from this workshop.
doi:10.1089/aid.2010.0226
PMCID: PMC3014767  PMID: 20969483
2.  The Cost and Impact of Scaling Up Pre-exposure Prophylaxis for HIV Prevention: A Systematic Review of Cost-Effectiveness Modelling Studies 
PLoS Medicine  2013;10(3):e1001401.
Gabriela Gomez and colleagues systematically review cost-effectiveness modeling studies of pre-exposure prophylaxis (PrEP) for preventing HIV transmission and identify the main considerations to address when considering the introduction of PrEP to HIV prevention programs.
Background
Cost-effectiveness studies inform resource allocation, strategy, and policy development. However, due to their complexity, dependence on assumptions made, and inherent uncertainty, synthesising, and generalising the results can be difficult. We assess cost-effectiveness models evaluating expected health gains and costs of HIV pre-exposure prophylaxis (PrEP) interventions.
Methods and Findings
We conducted a systematic review comparing epidemiological and economic assumptions of cost-effectiveness studies using various modelling approaches. The following databases were searched (until January 2013): PubMed/Medline, ISI Web of Knowledge, Centre for Reviews and Dissemination databases, EconLIT, and region-specific databases. We included modelling studies reporting both cost and expected impact of a PrEP roll-out. We explored five issues: prioritisation strategies, adherence, behaviour change, toxicity, and resistance. Of 961 studies retrieved, 13 were included. Studies modelled populations (heterosexual couples, men who have sex with men, people who inject drugs) in generalised and concentrated epidemics from Southern Africa (including South Africa), Ukraine, USA, and Peru. PrEP was found to have the potential to be a cost-effective addition to HIV prevention programmes in specific settings. The extent of the impact of PrEP depended upon assumptions made concerning cost, epidemic context, programme coverage, prioritisation strategies, and individual-level adherence. Delivery of PrEP to key populations at highest risk of HIV exposure appears the most cost-effective strategy. Limitations of this review include the partial geographical coverage, our inability to perform a meta-analysis, and the paucity of information available exploring trade-offs between early treatment and PrEP.
Conclusions
Our review identifies the main considerations to address in assessing cost-effectiveness analyses of a PrEP intervention—cost, epidemic context, individual adherence level, PrEP programme coverage, and prioritisation strategy. Cost-effectiveness studies indicating where resources can be applied for greatest impact are essential to guide resource allocation decisions; however, the results of such analyses must be considered within the context of the underlying assumptions made.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every year approximately 2.5 million people are infected with HIV, the virus that causes AIDS. Behavioral strategies like condom use and reduction of sexual partners have been the hallmarks of HIV prevention efforts. However, biological prevention measures have also recently been shown to be effective. These include male circumcision, treatment as prevention (treating HIV-infected people with antiretroviral drugs to reduce transmission), and pre-exposure prophylaxis (PrEP), where people not infected with HIV take antiretroviral drugs to reduce the probability of transmission. Strategies such as PrEP may be viable prevention measure for couples in long-term relationships where one partner is HIV-positive and the other is HIV-negative (HIV serodiscordant couples) or groups at higher risk of HIV infection, such as men who have sex with men, and injection drug users.
Why Was This Study Done?
The findings from recent clinical trials that demonstrate PrEP can reduce HIV transmission have led to important policy discussions and in the US, Southern Africa, and the UK new clinical guidelines have been developed on the use of PrEP for the prevention of HIV infection. For those countries that are considering whether to introduce PrEP into HIV prevention programs, national policy and decision makers need to determine potential costs and health outcomes. Cost-effectiveness models—mathematical models that simulate cost and health effects of different interventions—can help inform such decisions. However, the cost-effectiveness estimates that could provide guidance for PrEP programs are dependent on, and limited by, the assumptions included in the models, which can make their findings difficult to generalize. A systematic comparison of published cost-effectiveness models of HIV PrEP interventions would be useful for policy makers who are considering introducing PrEP intervention programs.
What Did the Researchers Do and Find?
The researchers performed a systematic review to identify published cost-effectiveness models that evaluated the health gains and costs of HIV PrEP interventions. Systematic reviews attempt to identify, appraise, and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question by using explicit methods aimed at minimizing bias. By searching databases the authors identified 13 published studies that evaluated the impact of PrEP in different populations (heterosexual couples, men who have sex with men, and injection drug users) in different geographic settings, which included Southern Africa, Ukraine, US, and Peru.
The authors identified seven studies that assessed the introduction of PrEP into generalized HIV epidemics in Southern Africa. These studies suggest that PrEP may be a cost effective intervention to prevent heterosexual transmission. However, the authors note that funding PrEP while other cost-effective HIV prevention methods are underfunded in this setting may have high opportunity costs. The authors identified five studies where PrEP was introduced for concentrated epidemics among men who have sex with men (four studies in the US and one in Peru). These studies suggest that PrEP may have a substantial impact on the HIV epidemic but may not be affordable at current drug prices. The authors also identified a single study that modeled the introduction of PrEP for people who inject drugs in the Ukraine, which found PrEP not to be cost effective.
In all settings the price of antiretroviral drugs was found to be a limiting factor in terms of affordability of PrEP programs. Behavioral changes and adherence to PrEP were estimated to have potentially significant impacts on program effectiveness but the emergence of drug resistance or PrEP-related toxicity did not significantly affect cost-effectiveness estimates. Several PrEP prioritization strategies were explored in included studies and delivering PrEP to populations at highest risk of HIV exposure was shown to improve cost-effectiveness estimates. However, the extra costs of identifying and engaging with high-risk populations were not taken into consideration. The authors note that the geographic coverage of identified studies was limited and that the findings are very dependent on the setting which limits generalizability.
What Do these Findings Mean?
These findings suggest that PrEP could be a cost-effective tool to reduce new HIV infections in some settings. However, the cost-effectiveness of PrEP is dependent upon cost, the epidemic context, program coverage and prioritization strategies, participants' adherence to the drug regimen, and PrEP efficacy estimates. These findings will aid decision makers quantify and compare the reductions in HIV incidence that could be achieved by implementing a PrEP program.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001401.
The US National Institute of Allergy and Infectious Diseases has information on HIV/AIDS
aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and has a section on PrEP
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including HIV prevention
AVAC Global Advocacy for HIV Prevention provides information on HIV prevention, including PrEP
The US Centers for Disease Control and Prevention also has information on PrEP
The World Health Organization has a page on its WHO-CHOICE criteria for cost-effectiveness
doi:10.1371/journal.pmed.1001401
PMCID: PMC3595225  PMID: 23554579
3.  Male Circumcision at Different Ages in Rwanda: A Cost-Effectiveness Study 
PLoS Medicine  2010;7(1):e1000211.
Agnes Binagwaho and colleagues predict that circumcision of newborn boys would be effective and cost-saving as a long-term strategy to prevent HIV in Rwanda.
Background
There is strong evidence showing that male circumcision (MC) reduces HIV infection and other sexually transmitted infections (STIs). In Rwanda, where adult HIV prevalence is 3%, MC is not a traditional practice. The Rwanda National AIDS Commission modelled cost and effects of MC at different ages to inform policy and programmatic decisions in relation to introducing MC. This study was necessary because the MC debate in Southern Africa has focused primarily on MC for adults. Further, this is the first time, to our knowledge, that a cost-effectiveness study on MC has been carried out in a country where HIV prevalence is below 5%.
Methods and Findings
A cost-effectiveness model was developed and applied to three hypothetical cohorts in Rwanda: newborns, adolescents, and adult men. Effectiveness was defined as the number of HIV infections averted, and was calculated as the product of the number of people susceptible to HIV infection in the cohort, the HIV incidence rate at different ages, and the protective effect of MC; discounted back to the year of circumcision and summed over the life expectancy of the circumcised person. Direct costs were based on interviews with experienced health care providers to determine inputs involved in the procedure (from consumables to staff time) and related prices. Other costs included training, patient counselling, treatment of adverse events, and promotion campaigns, and they were adjusted for the averted lifetime cost of health care (antiretroviral therapy [ART], opportunistic infection [OI], laboratory tests). One-way sensitivity analysis was performed by varying the main inputs of the model, and thresholds were calculated at which each intervention is no longer cost-saving and at which an intervention costs more than one gross domestic product (GDP) per capita per life-year gained. Results: Neonatal MC is less expensive than adolescent and adult MC (US$15 instead of US$59 per procedure) and is cost-saving (the cost-effectiveness ratio is negative), even though savings from infant circumcision will be realized later in time. The cost per infection averted is US$3,932 for adolescent MC and US$4,949 for adult MC. Results for infant MC appear robust. Infant MC remains highly cost-effective across a reasonable range of variation in the base case scenario. Adolescent MC is highly cost-effective for the base case scenario but this high cost-effectiveness is not robust to small changes in the input variables. Adult MC is neither cost-saving nor highly cost-effective when considering only the direct benefit for the circumcised man.
Conclusions
The study suggests that Rwanda should be simultaneously scaling up circumcision across a broad range of age groups, with high priority to the very young. Infant MC can be integrated into existing health services (i.e., neonatal visits and vaccination sessions) and over time has better potential than adolescent and adult circumcision to achieve the very high coverage of the population required for maximal reduction of HIV incidence. In the presence of infant MC, adolescent and adult MC would evolve into a “catch-up” campaign that would be needed at the start of the program but would eventually become superfluous.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Acquired immunodeficiency syndrome (AIDS) has killed more than 25 million people since 1981 and more than 31 million people (22 million in sub-Saharan Africa alone) are now infected with the human immunodeficiency virus (HIV), which causes AIDS. There is no cure for HIV/AIDS and no vaccine against HIV infection. Consequently, prevention of HIV transmission is extremely important. HIV is most often spread through unprotected sex with an infected partner. Individuals can reduce their risk of HIV infection, therefore, by abstaining from sex, by having one or a few sexual partners, and by always using a male or female condom. In addition, male circumcision—the removal of the foreskin, the loose fold of skin that covers the head of penis—can halve HIV transmission rates to men resulting from sex with women. Thus, as part of its HIV prevention strategy, the World Health Organization (WHO) recommends that male circumcision programs be scaled up in countries where there is a generalized HIV epidemic and where few men are circumcised.
Why Was This Study Done?
One such country is Rwanda. Here, 3% of the adult population is infected with HIV but only 15% of men are circumcised—worldwide, about 30% of men are circumcised. Demand for circumcision is increasing in Rwanda but, before policy makers introduce a country-wide male circumcision program, they need to identify the most cost-effective way to increase circumcision rates. In particular, they need to decide the age at which circumcision should be offered. Circumcision soon after birth (neonatal circumcision) is quick and simple and rarely causes any complications. Circumcision of adolescents and adults is more complex and has a higher complication rate. Although several studies have investigated the cost-effectiveness (the balance between the clinical and financial costs of a medical intervention and its benefits) of circumcision in adult men, little is known about its cost-effectiveness in newborn boys. In this study, which is one of several studies on male circumcision being organized by the National AIDS Control Commission in Rwanda, the researchers model the cost-effectiveness of circumcision at different ages.
What Did the Researchers Do and Find?
The researchers developed a simple cost-effectiveness model and applied it to three hypothetical groups of Rwandans: newborn boys, adolescent boys, and adult men. For their model, the researchers calculated the effectiveness of male circumcision (the number of HIV infections averted) by estimating the reduction in the annual number of new HIV infections over time. They obtained estimates of the costs of circumcision (including the costs of consumables, staff time, and treatment of complications) from health care providers and adjusted these costs for the money saved through not needing to treat HIV in males in whom circumcision prevented infection. Using their model, the researchers estimate that each neonatal male circumcision would cost US$15 whereas each adolescent or adult male circumcision would cost US$59. Neonatal male circumcision, they report, would be cost-saving. That is, over a lifetime, neonatal male circumcision would save more money than it costs. Finally, using the WHO definition of cost-effectiveness (for a cost-effective intervention, the additional cost incurred to gain one year of life must be less than a country's per capita gross domestic product), the researchers estimate that, although adolescent circumcision would be highly cost-effective, circumcision of adult men would only be potentially cost-effective (but would likely prove cost-effective if the additional infections that would occur from men to their partners without a circumcision program were also taken into account).
What Do These Findings Mean?
As with all modeling studies, the accuracy of these findings depends on the many assumptions included in the model. However, the findings suggest that male circumcision for infants for the prevention of HIV infection later in life is highly cost-effective and likely to be cost-saving and that circumcision for adolescents is cost-effective. The researchers suggest, therefore, that policy makers in Rwanda and in countries with similar HIV infection and circumcision rates should scale up male circumcision programs across all age groups, with high priority being given to the very young. If infants are routinely circumcised, they suggest, circumcision of adolescent and adult males would become a “catch-up” campaign that would be needed at the start of the program but that would become superfluous over time. Such an approach would represent a switch from managing the HIV epidemic as an emergency towards focusing on sustainable, long-term solutions to this major public-health problem.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000211.
This study is further discussed in a PLoS Medicine Perspective by Seth Kalichman
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
Information is available from the Joint United Nations Programme on HIV/AIDS (UNAIDS) on HIV infection and AIDS and on male circumcision in relation to HIV and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV and AIDS in Africa, and on circumcision and HIV (some information in English and Spanish)
More information about male circumcision is available from the Clearinghouse on Male Circumcision
The National AIDS Control Commission of Rwanda provides detailed information about HIV/AIDS in Rwanda (in English and French)
doi:10.1371/journal.pmed.1000211
PMCID: PMC2808207  PMID: 20098721
4.  The NIAID Division of AIDS enterprise information system: integrated decision support for global clinical research programs 
The National Institute of Allergy and Infectious Diseases (NIAID) Division of AIDS (DAIDS) Enterprise Information System (DAIDS-ES) is a web-based system that supports NIAID in the scientific, strategic, and tactical management of its global clinical research programs for HIV/AIDS vaccines, prevention, and therapeutics. Different from most commercial clinical trials information systems, which are typically protocol-driven, the DAIDS-ES was built to exchange information with those types of systems and integrate it in ways that help scientific program directors lead the research effort and keep pace with the complex and ever-changing global HIV/AIDS pandemic. Whereas commercially available clinical trials support systems are not usually disease-focused, DAIDS-ES was specifically designed to capture and incorporate unique scientific, demographic, and logistical aspects of HIV/AIDS treatment, prevention, and vaccine research in order to provide a rich source of information to guide informed decision-making. Sharing data across its internal components and with external systems, using defined vocabularies, open standards and flexible interfaces, the DAIDS-ES enables NIAID, its global collaborators and stakeholders, access to timely, quality information about NIAID-supported clinical trials which is utilized to: (1) analyze the research portfolio, assess capacity, identify opportunities, and avoid redundancies; (2) help support study safety, quality, ethics, and regulatory compliance; (3) conduct evidence-based policy analysis and business process re-engineering for improved efficiency. This report summarizes how the DAIDS-ES was conceptualized, how it differs from typical clinical trial support systems, the rationale for key design choices, and examples of how it is being used to advance the efficiency and effectiveness of NIAID's HIV/AIDS clinical research programs.
doi:10.1136/amiajnl-2011-000114
PMCID: PMC3241160  PMID: 21816958
Clinical trials management; medical informatics; enterprise architecture; web services; NIH, clinical research informatics
5.  HIV-1 Transmission during Early Infection in Men Who Have Sex with Men: A Phylodynamic Analysis 
PLoS Medicine  2013;10(12):e1001568.
Erik Volz and colleagues use HIV genetic information from a cohort of men who have sex with men in Detroit, USA to dissect the timing of onward transmission during HIV infection.
Please see later in the article for the Editors' Summary
Background
Conventional epidemiological surveillance of infectious diseases is focused on characterization of incident infections and estimation of the number of prevalent infections. Advances in methods for the analysis of the population-level genetic variation of viruses can potentially provide information about donors, not just recipients, of infection. Genetic sequences from many viruses are increasingly abundant, especially HIV, which is routinely sequenced for surveillance of drug resistance mutations. We conducted a phylodynamic analysis of HIV genetic sequence data and surveillance data from a US population of men who have sex with men (MSM) and estimated incidence and transmission rates by stage of infection.
Methods and Findings
We analyzed 662 HIV-1 subtype B sequences collected between October 14, 2004, and February 24, 2012, from MSM in the Detroit metropolitan area, Michigan. These sequences were cross-referenced with a database of 30,200 patients diagnosed with HIV infection in the state of Michigan, which includes clinical information that is informative about the recency of infection at the time of diagnosis. These data were analyzed using recently developed population genetic methods that have enabled the estimation of transmission rates from the population-level genetic diversity of the virus. We found that genetic data are highly informative about HIV donors in ways that standard surveillance data are not. Genetic data are especially informative about the stage of infection of donors at the point of transmission. We estimate that 44.7% (95% CI, 42.2%–46.4%) of transmissions occur during the first year of infection.
Conclusions
In this study, almost half of transmissions occurred within the first year of HIV infection in MSM. Our conclusions may be sensitive to un-modeled intra-host evolutionary dynamics, un-modeled sexual risk behavior, and uncertainty in the stage of infected hosts at the time of sampling. The intensity of transmission during early infection may have significance for public health interventions based on early treatment of newly diagnosed individuals.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Since the first recorded case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, has risen steadily. About 34 million people are currently HIV-positive, and about 2.5 million people become newly infected with HIV every year. Because HIV is usually transmitted through unprotected sex with an infected partner, individuals can reduce their risk of infection by abstaining from sex, by having only one or a few partners, and by always using condoms. Most people do not become ill immediately after infection with HIV, although some develop a short flu-like illness. The next stage of HIV infection, which may last more than ten years, also has no major symptoms, but during this stage, HIV slowly destroys immune system cells. Eventually, the immune system can no longer fight off infections by other disease-causing organisms, and HIV-positive people then develop one or more life-threatening AIDS-defining conditions, including unusual infections and specific types of cancer. HIV infection can be controlled, but not cured, by taking a daily cocktail of antiretroviral drugs.
Why Was This Study Done?
The design of effective programs to prevent the spread of HIV/AIDS depends on knowing how HIV transmissibility varies over the course of HIV infection. Consider, for example, a prevention strategy that focuses on increasing treatment rates: antiretroviral drugs, in addition to reducing illness and death among HIV-positive people, reduce HIV transmission from HIV-positive individuals. “Treatment as prevention” can only block transmissions that occur after diagnosis and entry into care. However, the transmissibility of HIV per sexual contact depends on a person's viral load, which peaks during early HIV infection, when people are often unaware of their HIV status and may still be following the high-risk patterns of sexual behavior that caused their own infection. Epidemiological surveillance data (information on HIV infections within populations) can be used to estimate how many new HIV infections occur within a population annually (HIV incidence) and the proportion of the population that is HIV-positive (HIV prevalence), but cannot be used to estimate the timing of transmission events. In this study, the researchers use “phylodynamic analysis” to estimate HIV incidence and prevalence and the timing of HIV transmission during infection. HIV, like many other viruses, rapidly accumulates genetic changes. The timing of transmission influences the pattern of these changes. Viral phylodynamic analysis—the quantitative study of how epidemiological, immunological, and evolutionary processes shape viral phylogenies (evolutionary trees)—can therefore provide estimates of transmission dynamics.
What Did the Researchers Do and Find?
The researchers obtained HIV sequence data (collected for routine surveillance of antiretroviral resistance mutations) and epidemiological surveillance data (including information on the stage of infection at diagnosis) for 662 HIV-positive men who have sex with men living in the Detroit metropolitan area of Michigan. They constructed a phylogenetic tree from the sequences using a “relaxed clock” approach and then fitted an epidemiological model (a mathematical model that represents the progress of individual patients through various stages of HIV infection) to the sequence data. Their approach, which integrates surveillance data and genetic data, yielded estimates of HIV incidence and prevalence among the study population similar to those obtained from surveillance data alone. However, it also provided information about HIV transmission that could not be obtained from surveillance data alone. In particular, it allowed the researchers to estimate that, in the current HIV epidemic among men who have sex with men in Detroit, 44.7% of HIV transmissions occur during the first year of infection.
What Do These Findings Mean?
The robustness of these findings depends on the validity of the assumptions included in the researchers' population genetic model and on the accuracy of the data fed into the model, and may not be generalizable to other cities or to other risk groups. Nevertheless, the findings of this analysis, which can be repeated in any setting where HIV sequence data for individual patients can be linked to patient-specific clinical and behavioral information, have important implications for HIV control strategies based on the early treatment of newly diagnosed individuals. Because relatively few infected individuals are diagnosed during early HIV infection, when the HIV transmission rate is high, it is unlikely, suggest the researchers, that the “treatment as prevention” strategy will effectively control the spread of HIV unless there are very high rates of HIV testing and treatment.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001568.
This study is further discussed in a PLOS Medicine Perspective by Timothy Hallett
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV treatment as prevention (in English and Spanish)
The PLOS Medicine Collection Investigating the Impact of Treatment on New HIV Infections provides more information about HIV treatment as prevention
A PLOS Computational Biology Topic Page (a review article that is a published copy of record of a dynamic version of the article as found in Wikipedia) about viral phylodynamics is available
The US National Institute of Health–funded HIV Sequence Database contains HIV sequences and tools to analyze these sequences
Patient stories about living with HIV/AIDS are available through Avert; the charity website Healthtalkonline also provides personal stories about living with HIV
doi:10.1371/journal.pmed.1001568
PMCID: PMC3858227  PMID: 24339751
6.  Changes in HIV Incidence among People Who Inject Drugs in Taiwan following Introduction of a Harm Reduction Program: A Study of Two Cohorts 
PLoS Medicine  2014;11(4):e1001625.
Kenrad Nelson and colleagues report on the association between HIV incidence and exposure to a national harm-reduction program among people who inject drugs in Taiwan.
Please see later in the article for the Editors' Summary
Background
Harm reduction strategies for combating HIV epidemics among people who inject drugs (PWID) have been implemented in several countries. However, large-scale studies using sensitive measurements of HIV incidence and intervention exposures in defined cohorts are rare. The aim of this study was to determine the association between harm reduction programs and HIV incidence among PWID.
Methods and Findings
The study included two populations. For 3,851 PWID who entered prison between 2004 and 2010 and tested HIV positive upon incarceration, we tested their sera using a BED HIV-1 capture enzyme immunoassay to estimate HIV incidence. Also, we enrolled in a prospective study a cohort of 4,357 individuals who were released from prison via an amnesty on July 16, 2007. We followed them with interviews at intervals of 6–12 mo and by linking several databases. A total of 2,473 participants who were HIV negative in January 2006 had interviews between then and 2010 to evaluate the association between use of harm reduction programs and HIV incidence. We used survival methods with attendance at methadone clinics as a time-varying covariate to measure the association with HIV incidence. We used a Poisson regression model and calculated the HIV incidence rate to evaluate the association between needle/syringe program use and HIV incidence. Among the population of PWID who were imprisoned, the implementation of comprehensive harm reduction programs and a lower mean community HIV viral load were associated with a reduced HIV incidence among PWID. The HIV incidence in this population of PWID decreased from 18.2% in 2005 to 0.3% in 2010. In an individual-level analysis of the amnesty cohort, attendance at methadone clinics was associated with a significantly lower HIV incidence (adjusted hazard ratio: 0.20, 95% CI: 0.06–0.67), and frequent users of needle/syringe program services had lower HIV incidence (0% in high NSP users, 0.5% in non NSP users). In addition, no HIV seroconversions were detected among prison inmates.
Conclusions
Although our data are affected by participation bias, they strongly suggest that comprehensive harm- reduction services and free treatment were associated with reversal of a rapidly emerging epidemic of HIV among PWID.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 35 million people worldwide are currently infected with HIV, the virus that causes AIDS, and about 2.3 million people become newly infected every year. HIV is mainly transmitted through unprotected sex with an infected partner. However, people who inject drugs (PWID) have a particularly high risk of HIV infection because blood transfer through needle and syringe sharing can transmit the virus. It is estimated that 5%–10% of all people living with HIV are PWID. Indeed, in some regions of the world the primary route of HIV transmission is through shared drug injection equipment and the prevalence (the proportion of a population that has a specific disease) of HIV infection among PWID is very high. In Asia, for example, more than a quarter of PWID are HIV positive. Because the high prevalence of HIV among PWID poses a global health challenge, bodies such as the Joint United Nations Programme on HIV/AIDS endorse harm reduction strategies to prevent risky injection behaviors among PWID. These strategies include the provision of clean needles and syringes, opioid substitution therapy such as methadone maintenance treatment, and antiretroviral treatment for HIV-positive PWID.
Why Was This Study Done?
Although harm reduction strategies for combating HIV epidemics among PWID have been implemented in several countries, few large-scale studies have examined the association between HIV incidence (the proportion of new cases of HIV in a population per year) and exposure to harm reduction programs among PWID. In this cohort study (an investigation that determines the characteristics of a group of people and then follows them over time), the researchers determine the association between harm reduction programs and HIV incidence among PWID in Taiwan. HIV infections used to be rare among the 60,000 PWID living in Taiwan, but after the introduction of a new HIV strain into the country in 2003, an HIV epidemic spread rapidly. In response, the Taiwanese government introduced a pilot program of harm reduction that included the provision of clean needles and syringes and health education in July 2005. The program was expanded to include methadone maintenance treatment in early 2006 and implemented nationwide in June 2006.
What Did the Researchers Do and Find?
The researchers enrolled two study populations. The first cohort comprised 3,851 PWID who were incarcerated for illicit drug use between 2004 and 2010 and who tested positive for HIV upon admission into prison. By using the BED assay, which indicates whether an HIV infection is recent, the researchers were able to determine the HIV incidence among the prisoners. In 2004, the estimated HIV incidence among prisoners with a history of drug injection was 6.44%. The incidence peaked in 2005 at 18.2%, but fell to 0.3% in 2010.
The second study population comprised 2,473 individuals who were HIV negative on January 1, 2006, and who had been incarcerated for drug use crimes but were released on July 16, 2007, during an amnesty. The researchers regularly interviewed these participants between their release and 2010 about their use of harm reduction interventions, and obtained other data about them (for example, diagnosis of HIV infection) from official databases. Analysis of all these data indicated that, in this cohort, attendance at methadone maintenance treatment clinics and frequent use of needle and syringe services were both associated with a significantly lower HIV incidence.
What Do These Findings Mean?
These findings suggest that the introduction of a comprehensive harm reduction program in Taiwan was associated with a significant reduction in the HIV incidence rate among PWID. These findings must be interpreted with caution, however. First, because the participants in the study were selected from PWID with histories of incarceration, the findings may not be representative of all PWID in Taiwan or of PWID in other countries. Second, PWID who chose to use needle and syringe services or methadone maintenance treatment clinics might have shared other unknown characteristics that affected their risk of HIV infection. Finally, some of the reduction in HIV incidence seen during the study is likely to be associated with the availability of free treatment, which has been offered to all HIV-positive individuals in Taiwan since 1997. Despite these limitations, these findings suggest that countries with a high prevalence and incidence of HIV among PWID should provide comprehensive harm reduction services to their populations to reduce risky drug injection behaviors.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001625.
Information is available from the US National Institute of Allergy and Infectious diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on injecting drug users and HIV/AIDS and on harm reduction and HIV prevention (in English and Spanish)
The US National Institute on Drug Abuse also provides information about drug abuse and HIV/AIDS (in English and Spanish)
The 2013 UNAIDS World AIDS Day report provides up-to-date information about the AIDS epidemic and efforts to halt it
Personal stories about living with HIV/AIDS are available through Avert, Nam/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001625
PMCID: PMC3979649  PMID: 24714449
7.  Incident HIV during Pregnancy and Postpartum and Risk of Mother-to-Child HIV Transmission: A Systematic Review and Meta-Analysis 
PLoS Medicine  2014;11(2):e1001608.
Alison Drake and colleagues conduct a systematic review and meta-analysis to estimate maternal HIV incidence during pregnancy and the postpartum period and to compare mother-to-child HIV transmission risk among women with incident versus chronic infection.
Please see later in the article for the Editors' Summary
Background
Women may have persistent risk of HIV acquisition during pregnancy and postpartum. Estimating risk of HIV during these periods is important to inform optimal prevention approaches. We performed a systematic review and meta-analysis to estimate maternal HIV incidence during pregnancy/postpartum and to compare mother-to-child HIV transmission (MTCT) risk among women with incident versus chronic infection.
Methods and Findings
We searched PubMed, Embase, and AIDS-related conference abstracts between January 1, 1980, and October 31, 2013, for articles and abstracts describing HIV acquisition during pregnancy/postpartum. The inclusion criterion was studies with data on recent HIV during pregnancy/postpartum. Random effects models were constructed to pool HIV incidence rates, cumulative HIV incidence, hazard ratios (HRs), or odds ratios (ORs) summarizing the association between pregnancy/postpartum status and HIV incidence, and MTCT risk and rates. Overall, 1,176 studies met the search criteria, of which 78 met the inclusion criterion, and 47 contributed data. Using data from 19 cohorts representing 22,803 total person-years, the pooled HIV incidence rate during pregnancy/postpartum was 3.8/100 person-years (95% CI 3.0–4.6): 4.7/100 person-years during pregnancy and 2.9/100 person-years postpartum (p = 0.18). Pooled cumulative HIV incidence was significantly higher in African than non-African countries (3.6% versus 0.3%, respectively; p<0.001). Risk of HIV was not significantly higher among pregnant (HR 1.3, 95% CI 0.5–2.1) or postpartum women (HR 1.1, 95% CI 0.6–1.6) than among non-pregnant/non-postpartum women in five studies with available data. In African cohorts, MTCT risk was significantly higher among women with incident versus chronic HIV infection in the postpartum period (OR 2.9, 95% CI 2.2–3.9) or in pregnancy/postpartum periods combined (OR 2.3, 95% CI 1.2–4.4). However, the small number of studies limited power to detect associations and sources of heterogeneity.
Conclusions
Pregnancy and the postpartum period are times of persistent HIV risk, at rates similar to “high risk” cohorts. MTCT risk was elevated among women with incident infections. Detection and prevention of incident HIV in pregnancy/postpartum should be prioritized, and is critical to decrease MTCT.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Worldwide, about 3.4 million children younger than 15 years old (mostly living in sub-Saharan Africa) are infected with HIV, the virus that causes AIDS by gradually destroying immune system cells, thereby leaving infected individuals susceptible to other serious infections. In 2012 alone, 230,000 children (more than 700 every day) were newly infected with HIV. Most HIV infections among children are the result of mother-to-child HIV transmission (MTCT) during pregnancy, delivery, or breastfeeding. The rate of MTCT (and deaths among HIV-positive pregnant women from complications related to HIV infection) can be greatly reduced by testing women for HIV infection during pregnancy (antenatal HIV testing), treating HIV-positive women with antiretroviral drugs (ARVs, powerful drugs that control HIV replication and allow the immune system to recover) during pregnancy, delivery, and breastfeeding, and giving ARVs to their newborn babies.
Why Was This Study Done?
The World Health Organization and the Joint United Nations Programme on HIV/AIDS (UNAIDS) have developed a global plan that aims to move towards eliminating new HIV infections among children by 2015 and towards keeping their mothers alive. To ensure the plan's success, the incidence of HIV (the number of new infections) among women and the rate of MTCT must be reduced by increasing ARV uptake by mothers and their infants for the prevention of MTCT. However, the risk of HIV infection among pregnant women and among women who have recently given birth (postpartum women) is poorly understood because, although guidelines recommend repeat HIV testing during late pregnancy or at delivery in settings where HIV infection is common, pregnant women are often tested only once for HIV infection. The lack of retesting represents a missed opportunity to identify pregnant and postpartum women who have recently acquired HIV and to prevent MTCT by initiating ARV therapy. In this systematic review (a study that uses predefined criteria to identify all the research on a given topic) and meta-analysis (a study that uses statistical methods to combine the results of several studies), the researchers estimate maternal HIV incidence during pregnancy and the postpartum period, and compare the risk of MTCT among women with incident (new) and chronic (long-standing) HIV infection.
What Did the Researchers Do and Find?
The researchers identified 47 studies (35 undertaken in Africa) that examined recent HIV acquisition by women during pregnancy and the 12-month postpartum period. They used random effects statistical models to estimate the pooled HIV incidence rate and cumulative HIV incidence (the number of new infections per number of people at risk), and the association between pregnancy/postpartum status and HIV incidence and MTCT risk and rates. The pooled HIV incidence rate among pregnant/postpartum women estimated from 19 studies (all from sub-Saharan Africa) that reported HIV incidence rates was 3.8/100 person-years. The pooled cumulative HIV incidence was significantly higher in African countries than in non-African countries (3.6% and 0.3%, respectively; a “significant” difference is one that is unlikely to arise by chance). In the five studies that provided suitable data, the risk of HIV acquisition was similar in pregnant, postpartum, and non-pregnant/non-postpartum women. Finally, among African women, the risk of MTCT was 2.9-fold higher during the postpartum period among those who had recently acquired HIV than among those with chronic HIV infection, and 2.3-fold higher during the pregnancy/postpartum periods combined.
What Do These Findings Mean?
These results suggest that women living in regions where HIV infection is common are at high risk of acquiring HIV infection during pregnancy and the postpartum period and that mothers who acquire HIV during pregnancy or postpartum are more likely to pass the infection on to their offspring than mothers with chronic HIV infections. However, the small number of studies included in this meta-analysis and the use of heterogeneous research methodologies in these studies may limit the accuracy of these findings. Nevertheless, these findings have important implications for the global plan to eliminate HIV infections in children. First, they suggest that women living in regions where HIV infection is common should be offered repeat HIV testing (using sensitive methods to enhance early detection of infection) during pregnancy and in the postpartum period to detect incident HIV infections, and should be promptly referred to HIV care and treatment. Second, they suggest that prevention of HIV transmission during pregnancy and postpartum should be prioritized, for example, by counseling women about the need to use condoms to prevent transmission during this period of their lives.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001608.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on children and HIV/AIDS and on the prevention of mother-to-child transmission of HIV (in English and Spanish)
The 2013 UNAIDS World AIDS Day Report provides information about the AIDS epidemic and efforts to halt it; the 2013 UNAIDS Progress Report on the Global Plan provides information on progress towards eliminating new HIV infections among children; the UNAIDS Believe it. Do it website provides information about the campaign to support the UNAIDS global plan
Personal stories about living with HIV/AIDS, including stories from young people infected with HIV, are available through Avert, NAM/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001608
PMCID: PMC3934828  PMID: 24586123
8.  Summary of presentations at the NIH/NIAID New Humanized Rodent Models 2007 Workshop 
It has long been recognized that a small animal model susceptible to HIV-1 infection with a functional immune system would be extremely useful in the study of HIV/AIDS pathogenesis and for the evaluation of vaccine and therapeutic strategies to combat this disease. By early 2007, a number of reports on various rodent models capable of being infected by and responding to HIV including some with a humanized immune system were published. The New Humanized Rodent Model Workshop, organized by the Division of AIDS (DAIDS), National Institute Allergy and Infection Diseases (NIAID), NIH, was held on September 24, 2007 at Bethesda for the purpose of bringing together key model developers and potential users. This report provides a synopsis of the presentations that discusses the current status of development and use of rodent models to evaluate the pathogenesis of HIV infection and to assess the efficacy of vaccine and therapeutic strategies including microbicides to prevent and/or treat HIVinfection.
doi:10.1186/1742-6405-5-3
PMCID: PMC2276217  PMID: 18237418
9.  Impact of Round-the-Clock, Rapid Oral Fluid HIV Testing of Women in Labor in Rural India 
PLoS Medicine  2008;5(5):e92.
Background
Testing pregnant women for HIV at the time of labor and delivery is the last opportunity for prevention of mother-to-child HIV transmission (PMTCT) measures, particularly in settings where women do not receive adequate antenatal care. However, HIV testing and counseling of pregnant women in labor is a challenge, especially in resource-constrained settings. In India, many rural women present for delivery without any prior antenatal care. Those who do get antenatal care are not always tested for HIV, because of deficiencies in the provision of HIV testing and counseling services. In this context, we investigated the impact of introducing round-the-clock, rapid, point-of-care HIV testing and counseling in a busy labor ward at a tertiary care hospital in rural India.
Methods and Findings
After they provided written informed consent, women admitted to the labor ward of a rural teaching hospital in India were offered two rapid tests on oral fluid and finger-stick specimens (OraQuick Rapid HIV-1/HIV-2 tests, OraSure Technologies). Simultaneously, venous blood was drawn for conventional HIV ELISA testing. Western blot tests were performed for confirmatory testing if women were positive by both rapid tests and dual ELISA, or where test results were discordant. Round-the-clock (24 h, 7 d/wk) abbreviated prepartum and extended postpartum counseling sessions were offered as part of the testing strategy. HIV-positive women were administered PMTCT interventions. Of 1,252 eligible women (age range 18 y to 38 y) approached for consent over a 9 mo period in 2006, 1,222 (98%) accepted HIV testing in the labor ward. Of these, 1,003 (82%) women presented with either no reports or incomplete reports of prior HIV testing results at the time of admission to the labor ward. Of 1,222 women, 15 were diagnosed as HIV-positive (on the basis of two rapid tests, dual ELISA and Western blot), yielding a seroprevalence of 1.23% (95% confidence interval [CI] 0.61%–1.8%). Of the 15 HIV test–positive women, four (27%) had presented with reported HIV status, and 11 (73%) new cases of HIV infection were detected due to rapid testing in the labor room. Thus, 11 HIV-positive women received PMTCT interventions on account of round-the-clock rapid HIV testing and counseling in the labor room. While both OraQuick tests (oral and finger-stick) were 100% specific, one false-negative result was documented (with both oral fluid and finger-stick specimens). Of the 15 HIV-infected women who delivered, 13 infants were HIV seronegative at birth and at 1 and 4 mo after delivery; two HIV-positive infants died within a month of delivery.
Conclusions
In a busy rural labor ward setting in India, we demonstrated that it is feasible to introduce a program of round-the-clock rapid HIV testing, including prepartum and extended postpartum counseling sessions. Our data suggest that the availability of round-the-clock rapid HIV testing resulted in successful documentation of HIV serostatus in a large proportion (82%) of rural women who were unaware of their HIV status when admitted to the labor room. In addition, 11 (73%) of a total of 15 HIV-positive women received PMTCT interventions because of round-the-clock rapid testing in the labor ward. These findings are relevant for PMTCT programs in developing countries.
Nitika Pant Pai and colleagues report the results of offering a round-the-clock rapid HIV testing program in a rural labor ward setting in India.
Editors' Summary
Background.
Since the first reported case of AIDS (acquired immunodeficiency syndrome) in 1981, the number of people infected with the human immunodeficiency virus (HIV), which causes AIDS, has risen steadily. Now, more than 33 million people are infected, almost half of them women. HIV is most often spread through unprotected sex with an infected partner, but mother-to-child transmission (MTCT) of HIV is also an important transmission route. HIV-positive women often pass the virus to their babies during pregnancy, labor and delivery, and breastfeeding, if nothing is done to prevent viral transmission. In developed countries, interventions such as voluntary testing and counseling, safe delivery practices (for example, offering cesarean delivery to HIV-positive women), and antiretroviral treatment of the mother during pregnancy and labor and of her newborn baby have minimized the risk of MTCT. In developing countries, the prevention of MTCT (PMTCT) is much less effective, in part because pregnant women often do not know their HIV status. Consequently, in 2007, nearly half a million children became infected with HIV mainly through MTCT.
Why Was This Study Done?
In many developing countries, women do not receive adequate antenatal care. In India, for example, nearly half the women living in rural areas do not receive any antenatal care until they are in labor. This gives health care providers very little time in which to counsel women about HIV infection, test them for the virus, and start interventions to prevent MTCT. Furthermore, testing pregnant women in labor for HIV and counseling them is a challenge, particularly where resources are limited. In this study, therefore, the researchers investigate the feasibility and impact of introducing round-the-clock, rapid HIV testing and counseling in a busy labor ward in a rural teaching hospital in Sevagram, India.
What Did the Researchers Do and Find?
Women admitted to the labor ward between January and September 2006 were offered two rapid HIV tests—one that used a saliva sample and the other that used blood taken from a finger prick. Blood was also taken from a vein for conventional HIV testing. All the women were given a 15-minute counseling session about how HIV is transmitted, the importance of HIV testing, and information on PMTCT before their child was born (prepartum counseling), and a longer postpartum counseling session. HIV-positive women were given a cesarean delivery where possible and antiretroviral drug treatment to reduce MTCT. 1,222 women admitted to the labor ward during the study period (1,003 of whom did not know their HIV status) accepted HIV testing. Of 15 study participants who were HIV positive, 11 learnt of their HIV status in the labor room. Two babies born to these HIV-positive women were HIV positive and died within a month of delivery; the other 13 babies were HIV negative at birth and at 1 and 4 months after delivery. Finally, the rapid HIV tests missed only one HIV-positive woman (no false-positive results were given), and the time from enrolling a woman into the study through referring her for PMTCT intervention where necessary averaged 40–60 minutes.
What Do These Findings Mean?
These findings show the feasibility and positive impact of the introduction of round-the-clock pre- and postpartum HIV counseling and rapid HIV testing into a busy rural Indian labor ward. Few of the women entering this ward knew their HIV status previously but the introduction of these facilities in this setting successfully informed these women of their HIV status. In addition, the round-the-clock counseling and testing led to 11 women and their babies receiving PMTCT interventions who would otherwise have been missed. These findings need to be confirmed in other settings and the cost-effectiveness and sustainability of this approach for the improvement of PMTCT in developing countries needs to be investigated. Nevertheless, these findings suggest that round-the-clock rapid HIV testing might be an effective and acceptable way to reduce MTCT of HIV in many developing countries.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050092.
Read a related PLoS Medicine Perspective article
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS and on HIV infection in women
HIV InSite has comprehensive information on all aspects of HIV/AIDS
Women, Children, and HIV provides extensive information on the prevention of mother-to-child transmission of HIV in developing countries
Information is available from Avert, an international AIDS charity, on HIV and AIDS in India, on women, HIV, and AIDS, and on HIV and AIDS prevention, including the prevention of mother-to-child transmission
AIDSinfo, a service of the US Department of Health and Human Services provides health information for HIV-positive pregnant women (in English and Spanish)
doi:10.1371/journal.pmed.0050092
PMCID: PMC2365974  PMID: 18462011
10.  Elimination of HIV in South Africa through Expanded Access to Antiretroviral Therapy: A Model Comparison Study 
PLoS Medicine  2013;10(10):e1001534.
Using nine structurally different models, Jan Hontelez and colleagues investigate timeframes for HIV elimination in South Africa using a universal test and treat strategy.
Please see later in the article for the Editors' Summary
Background
Expanded access to antiretroviral therapy (ART) using universal test and treat (UTT) has been suggested as a strategy to eliminate HIV in South Africa within 7 y based on an influential mathematical modeling study. However, the underlying deterministic model was criticized widely, and other modeling studies did not always confirm the study's finding. The objective of our study is to better understand the implications of different model structures and assumptions, so as to arrive at the best possible predictions of the long-term impact of UTT and the possibility of elimination of HIV.
Methods and Findings
We developed nine structurally different mathematical models of the South African HIV epidemic in a stepwise approach of increasing complexity and realism. The simplest model resembles the initial deterministic model, while the most comprehensive model is the stochastic microsimulation model STDSIM, which includes sexual networks and HIV stages with different degrees of infectiousness. We defined UTT as annual screening and immediate ART for all HIV-infected adults, starting at 13% in January 2012 and scaled up to 90% coverage by January 2019. All models predict elimination, yet those that capture more processes underlying the HIV transmission dynamics predict elimination at a later point in time, after 20 to 25 y. Importantly, the most comprehensive model predicts that the current strategy of ART at CD4 count ≤350 cells/µl will also lead to elimination, albeit 10 y later compared to UTT. Still, UTT remains cost-effective, as many additional life-years would be saved. The study's major limitations are that elimination was defined as incidence below 1/1,000 person-years rather than 0% prevalence, and drug resistance was not modeled.
Conclusions
Our results confirm previous predictions that the HIV epidemic in South Africa can be eliminated through universal testing and immediate treatment at 90% coverage. However, more realistic models show that elimination is likely to occur at a much later point in time than the initial model suggested. Also, UTT is a cost-effective intervention, but less cost-effective than previously predicted because the current South African ART treatment policy alone could already drive HIV into elimination.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 34 million people (mostly in low- and middle-income countries) are currently infected with HIV, the virus that causes AIDS, and every year another 2.5 million people become infected. HIV, which is usually transmitted through unprotected sex with an infected partner, gradually destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, people infected with HIV often died within ten years of infection. Then, in 1996, antiretroviral therapy (ART) became available, and, for people living in affluent countries, HIV/AIDS became a chronic condition. However, ART was expensive, so HIV/AIDS remained a fatal condition for people living in resource-limited countries. In 2006, the international community set a target of achieving universal ART coverage by 2010, and ART programs were initiated in many resource-limited countries. Although universal ART coverage has still not been achieved in South Africa, where nearly 6 million people are HIV-positive, 80% of people in need of ART were receiving a World Health Organization–recommended ART regimen by October 2012.
Why Was This Study Done?
ART is usually started when a person's CD4 count falls below 350 cells/µl blood, but it is thought that treatment of all HIV-positive individuals, regardless of their CD4 count, could reduce HIV transmission by reducing the infectiousness of HIV-positive individuals (“treatment as prevention”). Might it be possible, therefore, to eliminate HIV by screening everyone annually for infection and treating all HIV-positive individuals immediately? In 2009, a mathematical modeling study suggested that seven years of universal test and treat (UTT) could eliminate HIV in South Africa. The deterministic (nonrandom) model used in that study has been widely criticized, however, and some subsequent modeling studies have reached different conclusions, probably because of differences in the models' structures and in the assumptions built into them. A better understanding of the reasons for the discrepancies between models would help policy-makers decide whether to introduce UTT, so, here, the researchers developed several increasingly complex and realistic models of the South African HIV epidemic and used these models to predict the long-term impact of UTT in South Africa.
What Did the Researchers Do and Find?
The researchers developed nine structurally different mathematical models of the South African HIV epidemic based on the STDSIM framework, a stochastic microsimulation model that simulates the life course of individuals in a dynamic network of sexual contacts and in which events such as HIV infection are random processes. The simplest model, which resembled the original deterministic model, was extended by sequentially adding in factors such as different HIV transmission rates at different stages of HIV infection and up-to-date assumptions regarding the ability of ART to reduce HIV infectiousness. All the models replicated the prevalence of HIV in South Africa (the proportion of the population that was HIV-positive) between 1990 and 2010, and all predicted that UTT (defined as annual screening of individuals age 15+ years and immediate ART for all HIV-infected adults starting in 2012 and scaled up to 90% coverage by 2019) would result in HIV elimination (less than one new infection per 1,000 person-years). However, whereas the simplest model predicted that UTT would eliminate HIV after seven years, the more complex, realistic models predicted elimination at much later time points. Importantly, the most comprehensive model predicted that, although elimination would be reached after about 17 years of UTT, the current strategy of ART initiation for HIV-positive individuals at a CD4 cell count at or below 350 cells/µl would also lead to HIV elimination, albeit ten years later than UTT.
What Do These Findings Mean?
These findings confirm previous predictions that UTT could eliminate HIV in South Africa, but the development of more realistic models than those used in the past suggests that HIV elimination would occur substantially later than originally predicted. Importantly, the most comprehensive model suggests that HIV could be eliminated in South Africa using the current strategy for ART treatment alone. As with all modeling studies, the accuracy of these findings depends on the assumptions built into the models and on the structure of the models. Thus, although these findings support the use of UTT as an intervention to eliminate HIV, more research with comprehensive models that incorporate factors such as data from ongoing trials of treatment as prevention is needed to determine the population-level impact and overall cost-effectiveness of UTT.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001534.
This study is further discussed in a PLOS Medicine Perspective by Ford and Hirnschall
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV and AIDS in South Africa, on HIV treatment as prevention and the possibility of HIV elimination (in English and Spanish)
The 2012 UNAIDS World AIDS Day Report provides up-to-date information about the AIDS epidemic and efforts to halt it
The World Health Organization provides information about universal access to AIDS treatment (in several languages); its 2010 ART guidelines can be downloaded
The PLOS Medicine Collection Investigating the Impact of Treatment on New HIV Infections provides more information about HIV treatment as prevention
Personal stories about living with HIV/AIDS are available through Avert, through NAM/aidsmap, and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001534
PMCID: PMC3805487  PMID: 24167449
11.  Bacterial Vaginosis Associated with Increased Risk of Female-to-Male HIV-1 Transmission: A Prospective Cohort Analysis among African Couples 
PLoS Medicine  2012;9(6):e1001251.
In a prospective study, Craig Cohen and colleagues investigate the association between bacterial vaginosis and the risk of female-to-male HIV-1 transmission.
Background
Bacterial vaginosis (BV), a disruption of the normal vaginal flora, has been associated with a 60% increased risk of HIV-1 acquisition in women and higher concentration of HIV-1 RNA in the genital tract of HIV-1–infected women. However, whether BV, which is present in up to half of African HIV-1–infected women, is associated with an increase in HIV-1 transmission to male partners has not been assessed in previous studies.
Methods and Findings
We assessed the association between BV on female-to-male HIV-1 transmission risk in a prospective study of 2,236 HIV-1–seropositive women and their HIV-1 uninfected male partners from seven African countries from a randomized placebo-controlled trial that enrolled heterosexual African adults who were seropositive for both HIV-1 and herpes simplex virus (HSV)-2, and their HIV-1–seronegative partners. Participants were followed for up to 24 months; every three months, vaginal swabs were obtained from female partners for Gram stain and male partners were tested for HIV-1. BV and normal vaginal flora were defined as a Nugent score of 7–10 and 0–3, respectively. To reduce misclassification, HIV-1 sequence analysis of viruses from seroconverters and their partners was performed to determine linkage of HIV-1 transmissions. Overall, 50 incident HIV-1 infections occurred in men in which the HIV-1–infected female partner had an evaluable vaginal Gram stain. HIV-1 incidence in men whose HIV-1–infected female partners had BV was 2.91 versus 0.76 per 100 person-years in men whose female partners had normal vaginal flora (hazard ratio 3.62, 95% CI 1.74–7.52). After controlling for sociodemographic factors, sexual behavior, male circumcision, sexually transmitted infections, pregnancy, and plasma HIV-1 RNA levels in female partners, BV was associated with a greater than 3-fold increased risk of female-to-male HIV-1 transmission (adjusted hazard ratio 3.17, 95% CI 1.37–7.33).
Conclusions
This study identified an association between BV and increased risk of HIV-1 transmission to male partners. Several limitations may affect the generalizability of our results including: all participants underwent couples HIV counseling and testing and enrolled in an HIV-1 prevention trial, and index participants had a baseline CD4 count ≥250 cells/mm3 and were HSV-2 seropositive. Given the high prevalence of BV and the association of BV with increased risk of both female HIV-1 acquisition and transmission found in our study, if this association proves to be causal, BV could be responsible for a substantial proportion of new HIV-1 infections in Africa. Normalization of vaginal flora in HIV-1–infected women could mitigate female-to-male HIV-1 transmission.
Trial Registration: ClinicalTrials.com NCT00194519
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Since the first reported case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, has risen steadily. By the end of 2010, 34 million people were living with HIV/AIDS. At the beginning of the epidemic more men than women were infected with HIV. Now, however, 50% of all adults infected with HIV are women and in sub-Saharan Africa, where two-thirds of HIV-positive people live, women account for 59% of people living with HIV. Moreover, among 15–24 year-olds, women are eight times more likely than men to be HIV-positive. This pattern of infection has developed because most people in sub-Saharan Africa contract HIV through unprotected heterosexual sex. The risk of HIV transmission for both men and women in Africa and elsewhere can be reduced by abstaining from sex, by only having one or a few partners, by always using condoms, and by male circumcision. In addition, several studies suggest that antiretroviral therapy (ART) greatly reduces HIV transmission.
Why Was This Study Done?
Unfortunately, in sub-Saharan Africa, only about a fifth of HIV-positive people are currently receiving ART, which means that there is an urgent need to find other effective ways to reduce HIV transmission in this region. In this prospective cohort study (a type of study that follows a group of people for some time to see which personal characteristics are associated with disease development), the researchers investigate whether bacterial vaginosis—a condition in which harmful bacteria disrupt the normal vaginal flora—increases the risk of female-to-male HIV transmission among African couples. Bacterial vaginosis, which is extremely common in sub-Saharan Africa, has been associated with an increased risk of HIV acquisition in women and induces viral replication and shedding in the vagina in HIV-positive women, which may mean that HIV-positive women with bacterial vaginosis are more likely to transmit HIV to their male partners than women without this condition. If this is the case, then interventions that reduce the incidence of bacterial vaginosis might be valuable HIV prevention strategies.
What Did the Researchers Do and Find?
The researchers analyzed data collected from 2,236 heterosexual African couples enrolled in a clinical trial (the Partners in Prevention HSV/HIV Transmission Study) whose primary aim was to investigate whether suppression of herpes simplex virus infection could prevent HIV transmission. In all the couples, the woman was HIV-positive and the man was initially HIV-negative. The female partners were examined every three months for the presence of bacterial vaginosis and the male partners were tested regularly for HIV infection. The researchers also determined whether the men who became HIV-positive were infected with the same HIV strain as their partner to check that their infection had been acquired from this partner. The HIV incidence in men whose partners had bacterial vaginosis was 2.9 per 100 person-years (that is, 2.9 out of every 100 men became HIV-positive per year) whereas the HIV incidence in men whose partners had a normal vaginal flora was 0.76 per 100 person-years. After controlling for factors that might affect the risk of HIV transmission such as male circumcision and viral levels in female partner's blood, the researchers estimated that bacterial vaginosis was associated with a 3.17-fold increased risk of female-to-male HIV transmission in their study population.
What Do These Findings Mean?
These findings suggest that HIV-positive African women with bacterial vaginosis are more than three times as likely to transmit HIV to their male partners as those with a normal vaginal flora. It is possible that some unknown characteristic of the men in this study might have increased both their own risk of HIV infection and their partner's risk of bacterial vaginosis. Nevertheless, because bacterial vaginosis is so common in Africa (half of the women in this study had bacterial vaginosis at least once during follow-up) and because this condition is associated with both female HIV acquisition and transmission, these findings suggest that bacterial vaginosis could be responsible for a substantial proportion of new HIV infections in Africa. Normalization of vaginal flora in HIV-infected women by frequent presumptive treatment with antimicrobials (treatment with a curative dose of antibiotics without testing for bacterial vaginosis) or possibly by treatment with probiotics (live “good” bacteria) might, therefore, reduce female-to-male HIV transmission in sub-Saharan Africa.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001251.
Information is available from the US National Institute of Allergy and infectious diseases on all aspects of HIV infection and AIDS and on bacterial vaginosis
The US Centers for Disease Control and Prevention has information on all aspects of HIV/AIDS, including specific information about HIV/AIDS and women; it also has information on bacterial vaginosis (in English and Spanish)
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment, and information on bacterial vaginosis and HIV transmission (in several languages)
Information is available from Avert, an international AIDS nonprofit group on many aspects of HIV/AIDS, including detailed information on HIV and AIDS prevention, on women, HIV and AIDS and on HIV/AIDS in Africa (in English and Spanish); personal stories of women living with HIV are available; the website Healthtalkonline also provides personal stories about living with HIV
More information about the Partners in Prevention HSV/HIV Transmission Study is available
doi:10.1371/journal.pmed.1001251
PMCID: PMC3383741  PMID: 22745608
12.  HIV Treatment as Prevention: Systematic Comparison of Mathematical Models of the Potential Impact of Antiretroviral Therapy on HIV Incidence in South Africa 
PLoS Medicine  2012;9(7):e1001245.
Background
Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART) on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART.
Methods and Findings
Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/µl and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y) reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results.
Conclusions
Mathematical models evaluating the impact of ART vary substantially in structure, complexity, and parameter choices, but all suggest that ART, at high levels of access and with high adherence, has the potential to substantially reduce new HIV infections. There was broad agreement regarding the short-term epidemiologic impact of ambitious treatment scale-up, but more variation in longer term projections and in the efficiency with which treatment can reduce new infections. Differences between model predictions could not be explained by differences in model structure or parameterization that were hypothesized to affect intervention impact.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Following the first reported case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, increased rapidly. In recent years, the number of people becoming newly infected has declined slightly, but the virus continues to spread at unacceptably high levels. In 2010 alone, 2.7 million people became HIV-positive. HIV, which is usually transmitted through unprotected sex, destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, half of HIV-infected people died within eleven years of infection. Then, in 1996, antiretroviral therapy (ART) became available, and, for people living in affluent countries, HIV/AIDS gradually became considered a chronic condition. But because ART was expensive, for people living in developing countries HIV/AIDS remained a fatal condition. Roll-out of ART in developing countries first started in the early 2000s. In 2006, the international community set a target of achieving universal ART coverage by 2010. Although this target has still not been reached, by the end of 2010, 6.6 million of the estimated 15 million people in need of ART in developing countries were receiving ART.
Why Was This Study Done?
Several studies suggest that ART, in addition to reducing illness and death among HIV-positive people, reduces HIV transmission. Consequently, there is interest in expanding the provision of ART as a strategy for reducing the spread of HIV (“HIV treatment as prevention"), particularly in sub-Saharan Africa, where one in 20 adults is HIV-positive. It is important to understand exactly how ART might contribute to averting HIV transmission. Several mathematical models that simulate HIV infection and disease progression have been developed to investigate the impact of expanding access to ART on the incidence of HIV (the number of new infections occurring in a population over a year). But, although all these models predict that increased ART coverage will have epidemiologic (population) benefits, they vary widely in their estimates of the magnitude of these benefits. In this study, the researchers systematically compare the predictions of 12 mathematical models of the HIV epidemic in South Africa, simulating the same ART intervention programs to determine the extent to which different models agree about the impact of expanded ART.
What Did the Researchers Do and Find?
The researchers invited groups who had previously developed mathematical models of the epidemiological impact of expanded access to ART in South Africa to participate in a systematic comparison exercise in which their models were used to simulate ART scale-up scenarios in which the CD4 count threshold for treatment eligibility, access to treatment, and retention on treatment were systematically varied. To exclude variation resulting from different model assumptions about the past and current ART program, it was assumed that ART is introduced into the population in the year 2012, with no treatment provision prior to this, and interventions were evaluated in comparison to an artificial counterfactual scenario in which no treatment is provided. A standard scenario based on the World Health Organization's recommended threshold for initiation of ART, although unrepresentative of current provision in South Africa, was used to compare the models. In this scenario, 80% of HIV-infected individuals received treatment, they started treatment on average a year after their CD4 count dropped below 350 cells per microliter of blood, and 85% remained on treatment after three years. The models predicted that, with a start point of 2012, the HIV incidence would be 35%–54% lower in 2020 and 32%–74% lower in 2050 compared to a counterfactual scenario where there was no ART. Estimates of the number of person-years of ART needed per infection averted (the efficiency with which ART reduced new infections) ranged from 6.3–18.7 and from 4.5–20.2 over the periods 2012–2020 and 2012–2050, respectively. Finally, estimates of the impact of ambitious interventions (for example, immediate treatment of all HIV-positive individuals) varied widely across the models.
What Do These Findings Mean?
Although the mathematical models used in this study had different characteristics, all 12 predict that ART, at high levels of access and adherence, has the potential to reduce new HIV infections. However, although the models broadly agree about the short-term epidemiologic impact of treatment scale-up, their longer-term projections (including whether ART alone can eliminate HIV infection) and their estimates of the efficiency with which ART can reduce new infections vary widely. Importantly, it is possible that all these predictions will be wrong—all the models may have excluded some aspect of HIV transmission that will be found in the future to be crucial. Finally, these findings do not aim to indicate which specific ART interventions should be used to reduce the incidence of HIV. Rather, by comparing the models that are being used to investigate the feasibility of “HIV treatment as prevention," these findings should help modelers and policy-makers think critically about how the assumptions underlying these models affect the models' predictions.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001245.
This study is part of the July 2012 PLoS Medicine Collection, Investigating the Impact of Treatment on New HIV Infections
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV/AIDS treatment and care, on HIV treatment as prevention, and on HIV/AIDS in South Africa (in English and Spanish)
The World Health Organization provides information about universal access to AIDS treatment (in English, French, and Spanish); its 2010 ART guidelines can be downloaded
The HIV Modelling Consortium aims to improve scientific support for decision-making by coordinating mathematical modeling of the HIV epidemic
Patient stories about living with HIV/AIDS are available through Avert; the charity website Healthtalkonline also provides personal stories about living with HIV, including stories about taking anti-HIV drugs and the challenges of anti-HIV drugs
doi:10.1371/journal.pmed.1001245
PMCID: PMC3393664  PMID: 22802730
13.  Antiretroviral Therapy for Prevention of Tuberculosis in Adults with HIV: A Systematic Review and Meta-Analysis 
PLoS Medicine  2012;9(7):e1001270.
In a systematic review and meta-analysis, Amitabh Suthar and colleagues investigate the association between antiretroviral therapy and the reduction in the incidence of tuberculosis in adults with HIV infection.
Background
Human immunodeficiency virus (HIV) infection is the strongest risk factor for developing tuberculosis and has fuelled its resurgence, especially in sub-Saharan Africa. In 2010, there were an estimated 1.1 million incident cases of tuberculosis among the 34 million people living with HIV worldwide. Antiretroviral therapy has substantial potential to prevent HIV-associated tuberculosis. We conducted a systematic review of studies that analysed the impact of antiretroviral therapy on the incidence of tuberculosis in adults with HIV infection.
Methods and Findings
PubMed, Embase, African Index Medicus, LILACS, and clinical trial registries were systematically searched. Randomised controlled trials, prospective cohort studies, and retrospective cohort studies were included if they compared tuberculosis incidence by antiretroviral therapy status in HIV-infected adults for a median of over 6 mo in developing countries. For the meta-analyses there were four categories based on CD4 counts at antiretroviral therapy initiation: (1) less than 200 cells/µl, (2) 200 to 350 cells/µl, (3) greater than 350 cells/µl, and (4) any CD4 count.
Eleven studies met the inclusion criteria. Antiretroviral therapy is strongly associated with a reduction in the incidence of tuberculosis in all baseline CD4 count categories: (1) less than 200 cells/µl (hazard ratio [HR] 0.16, 95% confidence interval [CI] 0.07 to 0.36), (2) 200 to 350 cells/µl (HR 0.34, 95% CI 0.19 to 0.60), (3) greater than 350 cells/µl (HR 0.43, 95% CI 0.30 to 0.63), and (4) any CD4 count (HR 0.35, 95% CI 0.28 to 0.44). There was no evidence of hazard ratio modification with respect to baseline CD4 count category (p = 0.20).
Conclusions
Antiretroviral therapy is strongly associated with a reduction in the incidence of tuberculosis across all CD4 count strata. Earlier initiation of antiretroviral therapy may be a key component of global and national strategies to control the HIV-associated tuberculosis syndemic.
Review Registration
International Prospective Register of Systematic Reviews CRD42011001209
Please see later in the article for the Editors' Summary.
Editors' Summary
Background
Tuberculosis—a contagious bacterial infection— is a global public-health problem. In 2010, 8.8 million people developed active tuberculosis and 1.4 million people died from the disease. Tuberculosis can be cured by taking powerful antibiotics regularly for several months, and between 1995 and 2010, 46 million people with tuberculosis were successfully treated using DOTS—a directly observed antibiotic regimen designed by the World Health Organization (WHO). Now, though, the HIV epidemic is compromising global tuberculosis control efforts. HIV-positive people are very susceptible to tuberculosis because HIV, the virus that causes AIDS, destroys the immune system cells (including CD4 lymphocytes) that normally combat tuberculosis. In 2010, 1.1 million of the new (incident) cases of tuberculosis were among the 34 million people living with HIV, and 350,000 people died of HIV-associated tuberculosis, making tuberculosis the leading cause of death among HIV-positive people. To tackle HIV-associated tuberculosis, which occurs mainly in developing countries, WHO now recommends that HIV and tuberculosis programs use collaborative approaches such as the Three I's for HIV/TB strategy—intensified tuberculosis case-finding among HIV-positive people, isoniazid preventative therapy for HIV-positive people without active tuberculosis, and (tuberculosis) infection control in healthcare facilities, social settings, and households.
Why Was This Study Done?
Despite progress in scaling up the Three I's for HIV/TB strategy, complementary interventions are still needed to prevent tuberculosis in HIV-positive people. Antiretroviral therapy (ART) lowers the viral load of people infected with HIV and restores their immune system function and could, therefore, prevent HIVassociated tuberculosis, in addition to treating HIV infection. WHO recommends ART for all HIV-positive adults with a CD4 count of less than 350 cells/μl of blood and for all HIVpositive, tuberculosis-positive individuals irrespective of their CD4 count. However, the evidence for ART's preventative impact on tuberculosis has not been systematically examined. Here, the researchers undertake a systematic review (a search that uses predefined criteria to identify all the research on a given topic) and a meta-analysis (a statistical method for combining the results of studies) to investigate the impact of ART initiated at various CD4 counts on the development of tuberculosis in HIV-positive adults in developing countries.
What Did the Researchers Do and Find?
The researchers found 11 studies that compared tuberculosis incidence by ART status in HIV-infected adults over periods longer than six months on average in developing countries and undertook meta-analyses of these studies based on four categories of CD4 count at ART initiation (less than 200 cells/μl, 200–350 cells/μl, greater than 350 cells/μl, and any CD4 count). For all these categories, ART was strongly associated with a reduction in the incidence of tuberculosis. For example, the meta-analysis of the two studies that reported on participants in whom ART was initiated at a CD4 count less than 200 cells/μl yielded a hazard ratio (HR) of 0.16. That is, study participants starting ART when their CD4 count was below 200 cells/μl were about one-sixth as likely to develop tuberculosis as participants not receiving ART. In the metaanalysis of all 11 studies, study participants receiving ART were about one-third as likely to develop tuberculosis as study participants receiving no ART, irrespective of their CD4 count (HR 0.35). Importantly, the CD4 count at which ART was initiated did not significantly alter the magnitude of ART's preventive effect on tuberculosis development.
What Do These Findings Mean?
These findings suggest that ART is strongly associated with a reduction in the incidence of tuberculosis in HIV-positive adults in developing countries, whatever the CD4 count at ART initiation. Because most of the studies in this meta-analysis were observational, these results do not show that ART causes a reduction in tuberculosis incidence—other unknown factors shared by the study participants who received ART may be responsible for their lower tuberculosis incidence. Moreover, factors such as variations in diagnostic methods among the studies included in this meta-analysis may have affected the accuracy of these findings. Nevertheless, the key finding that ART is associated with a significant reduction in tuberculosis cases among adults with CD4 counts greater than 350 cells//μl should be considered by healthcare providers, policymakers, and people living with HIV when weighing the benefits and risks of early ART initiation. It also suggests that early ART initiation (in combination with expanded HIV testing) could be a key component of future global and national strategies to control HIV-associated tuberculosis.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001270.
WHO provides information on all aspects of tuberculosis, including information on tuberculosis and HIV, on the Three I's for HIV/TB, and on ART for tuberculosis prevention (some information is in several languages)
The TB/HIV Working Group is part of the Stop TB Partnership, which is working toward tuberculosis elimination; patient stories about tuberculosis/HIV co-infection are also available on their site
The US Centers for Disease Control and Prevention has information about tuberculosis and about tuberculosis and HIV co-infection
The US National Institute of Allergy and Infectious Diseases also has detailed information on all aspects of tuberculosis including HIV-associated tuberculosis
Information is available from Avert, an international AIDS charity, on HIV-related tuberculosis (in English and Spanish), and from Aidsmap, a non-governmental organization, on HIV-associated tuberculosis
doi:10.1371/journal.pmed.1001270
PMCID: PMC3404110  PMID: 22911011
14.  Estimating Incidence from Prevalence in Generalised HIV Epidemics: Methods and Validation 
PLoS Medicine  2008;5(4):e80.
Background
HIV surveillance of generalised epidemics in Africa primarily relies on prevalence at antenatal clinics, but estimates of incidence in the general population would be more useful. Repeated cross-sectional measures of HIV prevalence are now becoming available for general populations in many countries, and we aim to develop and validate methods that use these data to estimate HIV incidence.
Methods and Findings
Two methods were developed that decompose observed changes in prevalence between two serosurveys into the contributions of new infections and mortality. Method 1 uses cohort mortality rates, and method 2 uses information on survival after infection. The performance of these two methods was assessed using simulated data from a mathematical model and actual data from three community-based cohort studies in Africa. Comparison with simulated data indicated that these methods can accurately estimates incidence rates and changes in incidence in a variety of epidemic conditions. Method 1 is simple to implement but relies on locally appropriate mortality data, whilst method 2 can make use of the same survival distribution in a wide range of scenarios. The estimates from both methods are within the 95% confidence intervals of almost all actual measurements of HIV incidence in adults and young people, and the patterns of incidence over age are correctly captured.
Conclusions
It is possible to estimate incidence from cross-sectional prevalence data with sufficient accuracy to monitor the HIV epidemic. Although these methods will theoretically work in any context, we have able to test them only in southern and eastern Africa, where HIV epidemics are mature and generalised. The choice of method will depend on the local availability of HIV mortality data.
Timothy Hallett and colleagues develop and test two user-friendly methods to estimate HIV incidence based on changes in cross-sectional prevalence, using either mortality rates or survival after infection.
Editors' Summary
Background.
More than 25 million people have died from AIDS and about 33 million people are currently infected with human immunodeficiency virus (HIV, the virus that causes AIDS). Faced with this threat to human health, governments and international agencies are working together to halt the AIDS epidemic. An important part of this effort is HIV surveillance. The spread of HIV needs to be monitored to assess the impact of interventions (for example, the provision of antiretroviral drugs) and to plan for current and future health care needs. HIV surveillance in countries where the epidemic has spread beyond specific groups into the whole population (a generalized epidemic) has mainly relied on determining the prevalence of HIV infection (the fraction of the population that is infected) among women attending antenatal clinics. Recently, however, household health surveys (for example, the Demographic and Health Surveys) have begun to use blood testing for antibodies to the AIDS virus (serological testing) to provide more accurate estimates of HIV prevalence in the general adult population.
Why Was This Study Done?
Although prevalence estimates provide useful information about the HIV epidemic, another important indicator is incidence—the number of new infections occurring during a specific time period. Incidence measurements provide more information about temporal changes in the epidemic and transmission patterns and allow public-health experts to make better predictions of future health care needs. But, whereas prevalence can be measured with anonymized serological surveys, individuals would have to be identified and followed up in repeat serological surveys to provide a direct measurement of incidence. This is expensive and hard to achieve in many settings. In this study, therefore, the researchers develop and validate two mathematical methods to estimate HIV incidence in generalized HIV epidemics from prevalence data.
What Did the Researchers Do and Find?
Changes in the fraction of the population living with HIV (prevalence) can occur not only because of changes in the rate of new infections (incidence), but also because mortality rates are much higher for infected individuals than others. The researchers' methods disentangle the contributions to HIV prevalence (as measured in serological surveys) made by new infections from those due to deaths from AIDS and other causes. Their first method incorporates information on death rates collected in cohort studies of HIV infection (cohort studies investigate outcomes in groups of people); their second method uses information on survival after HIV infection, also collected in long-running cohort studies. The accuracy of both methods was assessed using computer-simulated data and actual data on HIV prevalence and incidence collected in three community-based cohort studies in Zimbabwe and Uganda (countries with generalized but declining HIV epidemics) and Tanzania (a country with a generalized, stable epidemic). Both methods provided accurate estimates of HIV incidence from the simulated data. Using the data collected in Africa, the mean difference between actual measurements of incidence and the estimate provided by method 1 was 19%; for method 2 it was 14%. In addition, the measured and estimated incidences were in good agreement for all age groups.
What Do These Findings Mean?
These findings suggest HIV incidence rates can be estimated from repeat surveys of prevalence with sufficient accuracy to monitor the HIV epidemic. The accuracy of the estimates across all age groups is particularly important because knowledge of the age-related risk pattern provides the information on transmission patterns that is needed to design effective intervention programs. Because these methods were tested using data only from southern and eastern Africa where the HIV epidemic is mature and generalized, they may not work as well in regions where the epidemic is restricted to subsets of the population. Other factors that might affect their accuracy include the amount of international migration and the uptake of antiretroviral therapies. Nevertheless, with the increased availability of serial measurements of serological prevalence, these new methods for estimating HIV incidence from HIV prevalence could prove extremely useful for monitoring the progress of national HIV epidemics and for guiding HIV control programs. The authors include spreadsheets that can be used to calculate incidence by either method from consecutive survey data.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050080.
The US National Institute of Allergy and Infectious Diseases provides information on HIV infection and AIDS
The US Centers for Disease Control and Prevention provides information on global HIV/AIDS topics (in English and Spanish)
The HIV InSite provides comprehensive and up-to-date information on all aspects of HIV/AIDS from the University of California San Francisco, including country reports on the AIDS epidemic in 195 countries, including Uganda, Zimbabwe, and Tanzania
Avert, an international AIDS charity, provides information on all aspects of HIV/AIDS, including fact sheets on understanding HIV and AIDS statistics, and on HIV and AIDS in Africa
The Demographic and Health Surveys program collects, analyzes, and disseminates information on health and population trends in countries around the world
doi:10.1371/journal.pmed.0050080
PMCID: PMC2288620  PMID: 18590346
15.  Supervised and Unsupervised Self-Testing for HIV in High- and Low-Risk Populations: A Systematic Review 
PLoS Medicine  2013;10(4):e1001414.
By systematically reviewing the literature, Nitika Pant Pai and colleagues assess the evidence base for HIV self tests both with and without supervision.
Background
Stigma, discrimination, lack of privacy, and long waiting times partly explain why six out of ten individuals living with HIV do not access facility-based testing. By circumventing these barriers, self-testing offers potential for more people to know their sero-status. Recent approval of an in-home HIV self test in the US has sparked self-testing initiatives, yet data on acceptability, feasibility, and linkages to care are limited. We systematically reviewed evidence on supervised (self-testing and counselling aided by a health care professional) and unsupervised (performed by self-tester with access to phone/internet counselling) self-testing strategies.
Methods and Findings
Seven databases (Medline [via PubMed], Biosis, PsycINFO, Cinahl, African Medicus, LILACS, and EMBASE) and conference abstracts of six major HIV/sexually transmitted infections conferences were searched from 1st January 2000–30th October 2012. 1,221 citations were identified and 21 studies included for review. Seven studies evaluated an unsupervised strategy and 14 evaluated a supervised strategy. For both strategies, data on acceptability (range: 74%–96%), preference (range: 61%–91%), and partner self-testing (range: 80%–97%) were high. A high specificity (range: 99.8%–100%) was observed for both strategies, while a lower sensitivity was reported in the unsupervised (range: 92.9%–100%; one study) versus supervised (range: 97.4%–97.9%; three studies) strategy. Regarding feasibility of linkage to counselling and care, 96% (n = 102/106) of individuals testing positive for HIV stated they would seek post-test counselling (unsupervised strategy, one study). No extreme adverse events were noted. The majority of data (n = 11,019/12,402 individuals, 89%) were from high-income settings and 71% (n = 15/21) of studies were cross-sectional in design, thus limiting our analysis.
Conclusions
Both supervised and unsupervised testing strategies were highly acceptable, preferred, and more likely to result in partner self-testing. However, no studies evaluated post-test linkage with counselling and treatment outcomes and reporting quality was poor. Thus, controlled trials of high quality from diverse settings are warranted to confirm and extend these findings.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 34 million people (most living in resource-limited countries) are currently infected with HIV, the virus that causes AIDS, and about 2.5 million people become infected with HIV every year. HIV is usually transmitted through unprotected sex with an infected partner. HIV infection is usually diagnosed by looking for antibodies to HIV in blood or saliva. Early during infection, the immune system responds to HIV by beginning to make antibodies that recognize the virus and target it for destruction. “Seroconversion”—the presence of detectable amounts of antibody in the blood or saliva—usually takes 6–12 weeks. Rapid antibody-based tests, which do not require laboratory facilities, can provide a preliminary result about an individual's HIV status from a simple oral swab or finger stick sample within 20 minutes. However preliminary rapid positive results have to be confirmed in a laboratory, which may take a few days or weeks. If positive, HIV infection can be controlled but not cured by taking a daily cocktail of powerful antiretroviral drugs throughout life.
Why Was This Study Done?
To reduce the spread of HIV, it is essential that HIV-positive individuals get tested, change behaviors avoid transmitting the virus to other people by, for example, always using a condom during sex, and if positive get on to treatment that is available worldwide. Treatment also reduces transmission of virus to the partner and controls the virus in the community. However, only half the people currently living with HIV know their HIV status, a state of affairs that increases the possibility of further HIV transmission to their partners and children. HIV positive individuals are diagnosed late with advanced HIV infection that costs health care services. Although health care facility-based HIV testing has been available for decades, people worry about stigma, visibility, and social discrimination. They also dislike the lack of privacy and do not like having to wait for their test results. Self-testing (i.e., self-test conduct and interpretation) might alleviate some of these barriers to testing by allowing individuals to determine their HIV status in the privacy of their home and could, therefore, increase the number of individuals aware of their HIV status. This could possibly reduce transmission and, through seeking linkages to care, bring HIV under control in communities. In some communities and countries, stigma of HIV prevents people from taking action about their HIV status. Indeed, an oral (saliva-based) HIV self-test kit is now available in the US. But how acceptable, feasible, and accurate is self-testing by lay people, and will people who find themselves self-test positive seek counseling and treatment? In this systematic review (a study that uses pre-defined criteria to identify all the research on a given topic), the researchers examine these issues by analyzing data from studies that have evaluated supervised self-testing (self-testing and counseling aided by a health-care professional) and unsupervised self-testing (self-testing performed without any help but with counseling available by phone or internet).
What Did the Researchers Do and Find?
The researchers identified 21 eligible studies, two-thirds of which evaluated oral self-testing and a third of which evaluated blood-based self-testing. Seven studies evaluated an unsupervised self-testing strategy and 14 evaluated a supervised strategy. Most of the data (89%) came from studies undertaken in high-income settings. The study populations varied from those at high risk of HIV infection to low-risk general populations. Across the studies, acceptability (defined as the number of people who actually self-tested divided by the number who consented to self-test) ranged from 74% to 96%. With both strategies, the specificity of self-testing (the chance of an HIV-negative person receiving a negative test result is true negative) was high but the sensitivity of self-testing (the chance of an HIV-positive person receiving a positive test result is indeed a true positive) was higher for supervised than for unsupervised testing. The researchers also found evidence that people preferred self-testing to facility-based testing and oral self-testing to blood-based self testing and, in one study, 96% of participants who self-tested positive sought post-testing counseling.
What Do These Findings Mean?
These findings provide new but limited information about the feasibility, acceptability, and accuracy of HIV self-testing. They suggest that it is feasible to implement both supervised and unsupervised self-testing, that both strategies are preferred to facility-based testing, but that the accuracy of self-testing is variable. However, most of the evidence considered by the researchers came from high-income countries and from observational studies of varying quality, and data on whether people self-testing positive sought post-testing counseling (linkage to care) were only available from one evaluation of unsupervised self-testing in the US. Consequently, although these findings suggest that self-testing could engage individuals in finding our their HIV status and thereby help modify behavior thus, reduce HIV transmission in the community, by increasing the proportion of people living with HIV who know their HIV status. The researchers suggested that more data from diverse settings and preferably from controlled randomized trials must be collected before any initiatives for global scale-up of self-testing for HIV infection are implemented.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001414.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV testing, and on HIV transmission and testing (in English and Spanish)
The UK National Health Service Choices website provides information about all aspects of HIV and AIDS; a “behind the headlines” article provides details about the 2012 US approval for an over-the-counter HIV home-use test
The 2012 World AIDS Day Report provides information about the percentage of people living with HIV who are aware of their HIV status in various African countries, as well as up-to-date information about the AIDS epidemic
Patient stories about living with HIV/AIDS are available through Avert; the nonprofit website Healthtalkonline also provides personal stories about living with HIV, including stories about getting a diagnosis
doi:10.1371/journal.pmed.1001414
PMCID: PMC3614510  PMID: 23565066
16.  HIV, Gender, Race, Sexual Orientation, and Sex Work: A Qualitative Study of Intersectional Stigma Experienced by HIV-Positive Women in Ontario, Canada 
PLoS Medicine  2011;8(11):e1001124.
Mona Loutfy and colleagues used focus groups to examine experiences of stigma and coping strategies among HIV-positive women in Ontario, Canada.
Background
HIV infection rates are increasing among marginalized women in Ontario, Canada. HIV-related stigma, a principal factor contributing to the global HIV epidemic, interacts with structural inequities such as racism, sexism, and homophobia. The study objective was to explore experiences of stigma and coping strategies among HIV-positive women in Ontario, Canada.
Methods and Findings
We conducted a community-based qualitative investigation using focus groups to understand experiences of stigma and discrimination and coping methods among HIV-positive women from marginalized communities. We conducted 15 focus groups with HIV-positive women in five cities across Ontario, Canada. Data were analyzed using thematic analysis to enhance understanding of the lived experiences of diverse HIV-positive women. Focus group participants (n = 104; mean age = 38 years; 69% ethnic minority; 23% lesbian/bisexual; 22% transgender) described stigma/discrimination and coping across micro (intra/interpersonal), meso (social/community), and macro (organizational/political) realms. Participants across focus groups attributed experiences of stigma and discrimination to: HIV-related stigma, sexism and gender discrimination, racism, homophobia and transphobia, and involvement in sex work. Coping strategies included resilience (micro), social networks and support groups (meso), and challenging stigma (macro).
Conclusions
HIV-positive women described interdependent and mutually constitutive relationships between marginalized social identities and inequities such as HIV-related stigma, sexism, racism, and homo/transphobia. These overlapping, multilevel forms of stigma and discrimination are representative of an intersectional model of stigma and discrimination. The present findings also suggest that micro, meso, and macro level factors simultaneously present barriers to health and well being—as well as opportunities for coping—in HIV-positive women's lives. Understanding the deleterious effects of stigma and discrimination on HIV risk, mental health, and access to care among HIV-positive women can inform health care provision, stigma reduction interventions, and public health policy.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
HIV-related stigma and discrimination—prejudice, negative attitudes, abuse, and maltreatment directed at people living with HIV—is a major factor contributing to the global HIV epidemic. HIV-related stigma, which devalues and stereotypes people living with HIV, increases vulnerability to HIV infection by reducing access to HIV prevention, testing, treatment, and support. At the personal (micro) level, HIV-related stigma can make it hard for people to take tests to determine their HIV status or to tell other people that they are HIV positive. At the social/community (meso) level, it can mean that HIV-positive people are ostracized from their communities. At the organizational/political (macro) level, it can mean that health-care workers treat HIV-positive people differently and that governments are deterred from taking fast, effective action against the HIV epidemic. In addition, HIV-related stigma is negatively associated with well-being among people living with HIV. Thus, among HIV-positive people, those who have experienced HIV-related stigma have higher levels of mental and physical illness.
Why Was This Study Done?
Racism (oppression and inequity founded on ethno-racial differences), sexism and gender discrimination (oppression and inequity based on gender bias in attitudes), and homophobia and transphobia (discrimination, fear, hostility, and violence towards nonheterosexual and transgender people, respectively) can also affect access to HIV services. However, little is known about how these different forms of stigma and discrimination interact (intersect). A better understanding of the effect of intersecting stigmas on people living with HIV could help in the development of stigma reduction interventions and HIV prevention, treatment and care programs, and could help to control global HIV infection rates. In this qualitative study (an analysis of people's attitudes and experiences rather than numerical data), the researchers investigate the intersection of HIV-related stigma, racism, sexism and gender discrimination, homophobia and transphobia among marginalized HIV-positive women in Ontario, Canada. As elsewhere in the world, HIV infection rates are increasing among women in Canada. Nearly 25% of people living with HIV in Canada are women and about a quarter of all new infections are in women. Moreover, there is a disproportionately high infection rate among marginalized women in Canada such as sex workers and lesbian, bisexual, and queer women.
What Did the Researchers Do and Find?
The researchers held 15 focus groups with 104 marginalized HIV-positive women who were recruited by word-of-mouth and through flyers circulated in community agencies serving women of diverse ethno-cultural origins. Each focus group explored topics that included challenges in daily life, medical issues and needs, and issues that were silenced within the participants' communities. The researchers analyzed the data from these focus groups using thematic analysis, an approach that identifies, analyzes, and reports themes in qualitative data. They found that women living with HIV in Ontario experienced multiple types of stigma at different levels. So, for example, women experienced HIV-related stigma at the micro (“If you're HIV-positive, you feel shameful”), meso (“The thing I hate most for people that test positive for HIV is that society ostracizes them”), and macro (“A lot of women are not getting employed because they have to disclose their status”) levels. The women also attributed their experiences of stigma and discrimination to sexism and gender discrimination, racism, homophobia and transphobia, and involvement in sex work at all three levels and described coping strategies at the micro (resilience; “I always live with hope”), meso (participation in social networks), and macro (challenging stigma) levels.
What Do These Findings Mean?
These findings indicate that marginalized HIV-positive women living in Ontario experience overlapping forms of stigma and discrimination and that these forms of stigma operate over micro, meso, and macro levels, as do the coping strategies adopted by the women. Together, these results support an intersectional model of stigma and discrimination that should help to inform discussions about the complexity of stigma and coping strategies. However, because only a small sample of nonrandomly selected women was involved in this study, these findings need to be confirmed in other groups of HIV-positive women. If confirmed, the complex system of interplay of different forms of stigma revealed here should help to inform health-care provision, stigma reduction interventions, and public-health policy, and could, ultimately, help to bring the global HIV epidemic under control.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001124.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment; its publication HIV and stigma deals with HIV-related stigma in the UK
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on women, HIV, and AIDS, on HIV and AIDS stigma and discrimination, and on HIV/AIDS statistics for Canada (in English and Spanish)
The People Living with Stigma Index to address stigma relating to HIV and advocate on key barriers and issues perpetuating stigma; it has recently published Piecing it together for women and girls, the gender dimensions of HIV-related stigma; its website will soon include a selection of individual stories about HIV-related stigma
Patient stories about living with HIV/AIDS are available through Avert and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001124
PMCID: PMC3222645  PMID: 22131907
17.  Cost-Effectiveness of Pooled Nucleic Acid Amplification Testing for Acute HIV Infection after Third-Generation HIV Antibody Screening and Rapid Testing in the United States: A Comparison of Three Public Health Settings 
PLoS Medicine  2010;7(9):e1000342.
Angela Hutchinson and colleagues conducted a cost-effectiveness analysis of pooled nucleic acid amplification testing following HIV testing and show that it is not cost-effective at recommended antibody testing intervals for high-risk persons except in very high-incidence settings.
Background
Detection of acute HIV infection (AHI) with pooled nucleic acid amplification testing (NAAT) following HIV testing is feasible. However, cost-effectiveness analyses to guide policy around AHI screening are lacking; particularly after more sensitive third-generation antibody screening and rapid testing.
Methods and Findings
We conducted a cost-effectiveness analysis of pooled NAAT screening that assessed the prevention benefits of identification and notification of persons with AHI and cases averted compared with repeat antibody testing at different intervals. Effectiveness data were derived from a Centers for Disease Control and Prevention AHI study conducted in three settings: municipal sexually transmitted disease (STD) clinics, a community clinic serving a population of men who have sex with men, and HIV counseling and testing sites. Our analysis included a micro-costing study of NAAT and a mathematical model of HIV transmission. Cost-effectiveness ratios are reported as costs per quality-adjusted life year (QALY) gained in US dollars from the societal perspective. Sensitivity analyses were conducted on key variables, including AHI positivity rates, antibody testing frequency, symptomatic detection of AHI, and costs. Pooled NAAT for AHI screening following annual antibody testing had cost-effectiveness ratios exceeding US$200,000 per QALY gained for the municipal STD clinics and HIV counseling and testing sites and was cost saving for the community clinic. Cost-effectiveness ratios increased substantially if the antibody testing interval decreased to every 6 months and decreased to cost-saving if the testing interval increased to every 5 years. NAAT was cost saving in the community clinic in all situations. Results were particularly sensitive to AHI screening yield.
Conclusions
Pooled NAAT screening for AHI following negative third-generation antibody or rapid tests is not cost-effective at recommended antibody testing intervals for high-risk persons except in very high-incidence settings.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Since 1981, acquired immunodeficiency syndrome (AIDS) has killed about 25 million people and about 30 million people are now infected with the human immunodeficiency virus (HIV), which causes AIDS. HIV, which is most often transmitted through unprotected sex with an infected partner or injection drug use, infects and kills immune system cells, leaving infected individuals susceptible to other infectious diseases. The first, often undiagnosed stage of HIV infection—acute HIV infection (AHI)—lasts a few weeks and sometimes involves a flu-like illness. During AHI, the immune system responds to HIV by beginning to make antibodies that recognize the virus but seroconversion—the appearance of detectable amounts of antibody in the blood—takes 6–12 weeks. During the second, symptom-free stage of HIV infection, which can last many years, the virus gradually destroys the immune system so that by the third stage of infection unusual infections (for example, persistent yeast infections) begin to occur. The final stage of infection (AIDS) is characterized by multiple severe infections and by the development of unusual cancers.
Why Was This Study Done?
Antiretroviral drugs control HIV infections but don't cure them. It is very important, therefore, to prevent HIV transmission by avoiding HIV risk behaviors that increase the risk of HIV infection such as having sex without a condom or with many partners. Individuals with AHI in particular need to avoid high-risk behaviors because these people are extremely infectious. However, routine tests for HIV infection that measure antibodies in the blood often give false-negative results in people with AHI because of the time lag between infection and seroconversion. Nucleic acid amplification testing (NAAT), which detects HIV genetic material in the blood, is a more accurate way to diagnose AHI but is expensive. In this study, the researchers investigate whether pooled NAAT screening (specimens are pooled before testing to reduce costs) for AHI in clinic settings after third-generation antibody testing is a cost-effective HIV prevention strategy. That is, does the gain in quality-adjusted life years (QALY, a measure of the quantity and quality of life generated by healthcare interventions) achieved by averting new HIV infections outweigh the costs of pooled NAAT screening?
What Did the Researchers Do and Find?
The researchers combined effectiveness data from a US study in which AHI was detected using pooled NAAT in three settings (sexually transmitted disease [STD] clinics, a community clinic serving men who have sex with men [MSM], and HIV counseling/testing sites) with a “micro-costing” study of NAAT and a mathematical model of HIV transmission. They then calculated the costs per QALY gained (the cost-effectiveness ratio) as a result of HIV prevention by identification and notification of people with AHI through pooled NAAT screening compared with repeat antibody testing. Pooled NAAT for AHI screening following annual antibody testing (the recommended testing interval for high-risk individuals), they estimate, would cost US$372,300 and US$484,400 per QALY gained for the counseling/testing sites and STD clinics, respectively, whereas pooled NAAT for AHI screening was cost-saving for the community clinic serving MSM. The cost-effectiveness ratio increased for the counseling/testing sites and STD clinics when the antibody testing interval was decreased to 6 months but remained cost-saving for the community clinic. With an antibody testing interval of 5 years, pooled NAAT was cost-saving in all three settings.
What Do These Findings Mean?
Cost-effectiveness ratios of US$100,000–US$200,000 are considered acceptable in the US. These results suggest therefore, that the cost of pooled NAAT screening for AHI following negative third-generation antibody testing is not acceptable at the recommended testing interval for high-risk individuals except in settings where HIV infection is very common such as clinics serving MSM. The researchers reach a similar conclusion in a separate cost-effectiveness analysis of pooled NAAT screening following a negative rapid HIV test. Although the accuracy of these results depends on numerous assumptions made in the cost-effectiveness analyses (for example, the degree to which awareness of HIV status affects the behavior of people with AHI), sensitivity analyses (investigations of the effect of altering key assumptions) show that these findings are not greatly affected by changes in many of these assumptions. Thus, the researchers conclude, NAAT screening should be reserved for settings that serve populations in which there are very high levels of new HIV infection.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000342.
The US Centers for Disease Control and Prevention provides information on HIV infection and AIDS and on HIV testing and diagnosis
HIV InSite has information on all aspects of HIV/AIDS
Information is available from Avert, an international AIDS nonprofit organization on many aspects of HIV/AIDS, including HIV testing (in English and Spanish)
MedlinePlus has links to further resources on AIDS (in English and Spanish)
The UK National Institute of Health and Clinical Excellence has a page on measuring effectiveness and cost-effectiveness
doi:10.1371/journal.pmed.1000342
PMCID: PMC2946951  PMID: 20927354
18.  Optimal Uses of Antiretrovirals for Prevention in HIV-1 Serodiscordant Heterosexual Couples in South Africa: A Modelling Study 
PLoS Medicine  2011;8(11):e1001123.
Hallett et al use a mathematical model to examine the long-term impact and cost-effectiveness of different pre-exposure prophylaxis (PrEP) strategies for HIV prevention in serodiscordant couples.
Background
Antiretrovirals have substantial promise for HIV-1 prevention, either as antiretroviral treatment (ART) for HIV-1–infected persons to reduce infectiousness, or as pre-exposure prophylaxis (PrEP) for HIV-1–uninfected persons to reduce the possibility of infection with HIV-1. HIV-1 serodiscordant couples in long-term partnerships (one member is infected and the other is uninfected) are a priority for prevention interventions. Earlier ART and PrEP might both reduce HIV-1 transmission in this group, but the merits and synergies of these different approaches have not been analyzed.
Methods and Findings
We constructed a mathematical model to examine the impact and cost-effectiveness of different strategies, including earlier initiation of ART and/or PrEP, for HIV-1 prevention for serodiscordant couples. Although the cost of PrEP is high, the cost per infection averted is significantly offset by future savings in lifelong treatment, especially among couples with multiple partners, low condom use, and a high risk of transmission. In some situations, highly effective PrEP could be cost-saving overall. To keep couples alive and without a new infection, providing PrEP to the uninfected partner could be at least as cost-effective as initiating ART earlier in the infected partner, if the annual cost of PrEP is <40% of the annual cost of ART and PrEP is >70% effective.
Conclusions
Strategic use of PrEP and ART could substantially and cost-effectively reduce HIV-1 transmission in HIV-1 serodiscordant couples. New and forthcoming data on the efficacy of PrEP, the cost of delivery of ART and PrEP, and couples behaviours and preferences will be critical for optimizing the use of antiretrovirals for HIV-1 prevention.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every year, about 2.5 million people become infected with HIV, the virus that causes AIDS. HIV is usually transmitted through unprotected sex with an HIV-infected partner. It destroys immune system cells (including CD4 cells, a type of lymphocyte), leaving infected individuals susceptible to other infections. There is no cure for AIDS, although HIV can be held in check with antiretroviral therapy (ART), and there is no vaccine that protects against HIV infection. So, to halt the AIDS epidemic, other ways of preventing the spread of HIV are needed. Antiretroviral drugs could potentially be used in two ways to reduce HIV transmission. First, ART could be given to HIV-infected people before they need it for their own health to reduce their infectiousness; the World Health Organization currently recommends that HIV-positive people initiate ART when their CD4 count drops below 350 cells/µl blood but in many African countries ART is only initiated when CD4 counts fall below 200 cells/µl. Second, ART could be given to HIV-uninfected people to reduce acquisition of the virus. This approach—preexposure prophylaxis (PrEP)—has provided protection against HIV transmission in some but not all clinical trials.
Why Was This Study Done?
Couples in long-term relationships where one partner is HIV-positive and the other is HIV-negative (HIV serodiscordant couples) are a priority group for prevention interventions. In sub-Saharan Africa, where most new HIV infections occur, 10%–20% of stable partnerships are serodiscordant and condom use is often low, not least because such couples may want children. Earlier ART or PrEP might reduce HIV transmission in this group but the merits of different approaches have not been analyzed. In this study, the researchers use a mathematical model to examine the long-term impact and cost-effectiveness of different PrEP and ART strategies for HIV prevention in serodiscordant couples.
What Did the Researchers Do and Find?
The researchers constructed a model to simulate HIV infection and disease progression among hypothetical HIV serodiscordant stable heterosexual couples. The model incorporated data from South Africa on couple characteristics, disease progression, ART use, pregnancies, frequency of sex, and contact with other sexual partners, as well as estimates of the effectiveness of PrEP from clinical trials. The researchers used the model to compare the impact on HIV transmission, survival and quality of life, and the cost-effectiveness of no PrEP with four PrEP strategies—always use PrEP after diagnosis of HIV serodiscordancy, use PrEP up to and for a year after ART initiation by the HIV-infected partner (at a CD4 count of ≤200 cells/µl or ≤350 cells/µl), use PrEP only up to ART initiation by the infected partner, and use PrEP only while trying for a baby and during pregnancy. The model predicts, for example, that the cost per infection averted of PrEP used before ART initiation will be offset by future savings in lifelong treatment, particularly among couples with multiple partners, low condom use, and a high risk of transmission. To keep couples alive without the HIV-uninfected partner becoming infected, it could be more cost-effective to provide PrEP to the uninfected partner than to initiate ART earlier in the infected partner, provided the annual cost of PrEP is less than 40% of the annual cost of ART and PrEP is more than 70% effective. Finally, if PREP is 30%–60% effective, the most cost-effective strategy for couples could be to use PrEP in the uninfected partner prior to ART initiation in the infected partner at a CD4 count ≤350 cells/µl.
What Do These Findings Mean?
These findings suggest that the strategic use of PrEP and ART could cost-effectively reduce HIV transmission in HIV serodiscordant stable heterosexual couples in sub-Saharan Africa. The accuracy of these findings depends on the assumptions included in the mathematical model and on the data fed into it. In particular, the interpretation of these results is complicated by uncertainties in the likely cost of PrEP and the “real-world” effectiveness of PrEP. Nevertheless, these findings suggest that PrEP may become a valuable addition in some settings to existing approaches for HIV prevention such as condom promotion and male circumcision programs. Moreover, additional simulations with this mathematical model using more accurate information on the costs and effectiveness of PrEP could assist in future policy making decisions.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001123.
Information is available from the US National Institute of Allergy and infectious diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and a section on PrEP
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on all aspects of HIV prevention, and on HIV/AIDS in Africa (in English and Spanish)
AVAC Global Advocacy for HIV Prevention provides up-to-date information on all aspects of HIV prevention, including PrEP
The US Centers for Disease Control and Prevention also has information on PrEP
WHO provides information about antiretroviral therapy
Patient stories about living with HIV/AIDS are available through Avert and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001123
PMCID: PMC3217021  PMID: 22110407
19.  Assessment of Recent HIV-1 Infection by a Line Immunoassay for HIV-1/2 Confirmation 
PLoS Medicine  2007;4(12):e343.
Background
Knowledge of the number of recent HIV infections is important for epidemiologic surveillance. Over the past decade approaches have been developed to estimate this number by testing HIV-seropositive specimens with assays that discriminate the lower concentration and avidity of HIV antibodies in early infection. We have investigated whether this “recency” information can also be gained from an HIV confirmatory assay.
Methods and Findings
The ability of a line immunoassay (INNO-LIA HIV I/II Score, Innogenetics) to distinguish recent from older HIV-1 infection was evaluated in comparison with the Calypte HIV-1 BED Incidence enzyme immunoassay (BED-EIA). Both tests were conducted prospectively in all HIV infections newly diagnosed in Switzerland from July 2005 to June 2006. Clinical and laboratory information indicative of recent or older infection was obtained from physicians at the time of HIV diagnosis and used as the reference standard. BED-EIA and various recency algorithms utilizing the antibody reaction to INNO-LIA's five HIV-1 antigen bands were evaluated by logistic regression analysis. A total of 765 HIV-1 infections, 748 (97.8%) with complete test results, were newly diagnosed during the study. A negative or indeterminate HIV antibody assay at diagnosis, symptoms of primary HIV infection, or a negative HIV test during the past 12 mo classified 195 infections (26.1%) as recent (≤ 12 mo). Symptoms of CDC stages B or C classified 161 infections as older (21.5%), and 392 patients with no symptoms remained unclassified. BED-EIA ruled 65% of the 195 recent infections as recent and 80% of the 161 older infections as older. Two INNO-LIA algorithms showed 50% and 40% sensitivity combined with 95% and 99% specificity, respectively. Estimation of recent infection in the entire study population, based on actual results of the three tests and adjusted for a test's sensitivity and specificity, yielded 37% for BED-EIA compared to 35% and 33% for the two INNO-LIA algorithms. Window-based estimation with BED-EIA yielded 41% (95% confidence interval 36%–46%).
Conclusions
Recency information can be extracted from INNO-LIA-based confirmatory testing at no additional costs. This method should improve epidemiologic surveillance in countries that routinely use INNO-LIA for HIV confirmation.
Jörg Schüpbach and colleagues show that a second-generation Western blot antibody test used to confirm HIV infection can also be used to determine rates of recent HIV infection.
Editors' Summary
Background.
Since the first diagnosed cases of AIDS (acquired immunodeficiency syndrome) in 1981, the AIDS epidemic has spread rapidly. Now, 40 million people are infected with HIV (human immunodeficiency virus), the cause of AIDS. HIV infects and kills immune system cells, leaving infected individuals susceptible to other infectious diseases and tumors. The first, often undiagnosed, stage of HIV infection (primary HIV infection) lasts a few weeks and often involves a flu-like illness. During this stage, the immune system begins to respond to HIV by producing antibodies (proteins that recognize viral molecules called antigens). The time needed for these antibodies to appear on testing “seroconversion” (usually 6–12 weeks) is called the window period of the test; HIV antibody tests done during this period give false negative results. During the second, symptom-free stage of HIV infection, which can last many years, the virus gradually destroys the immune system so that by the third stage of infection unusual infections (for example, persistant yeast infections of the mouth) begin to occur. The fourth stage is characterized by multiple AIDS-indicator conditions such as severe bacterial, fungal, or viral infections, and cancers such as Kaposi sarcoma.
Why Was This Study Done?
To monitor the AIDS/HIV epidemic and HIV prevention programs, it is necessary to know how many people in a population have been recently infected with HIV. Serologic testing algorithms for recent HIV seroconversion (STARHS) provide a way to get this information. Early during seroconversion, low levels of antibodies that bind only weakly to their viral antigens (low-affinity antibodies) are made. Later on, antibody concentrations and tightness of binding increase. STARHS calculate the number of recently infected people by analyzing data from special “detuned” HIV antibody assays (for example, a commercially available test called the BED-EIA) that preferentially detect low-concentration, low-avidity antibodies. This type of test cannot, however, be used to determine whether an individual has an HIV infection, because it will miss a substantial fraction of infected people. Diagnosing HIV in an individual person requires more sensitive tests for antibody detection. In this study, the researchers have investigated whether a test called INNO-LIA, which is already being used in some countries to diagnose HIV infection, can also provide information about the recency (newness) of HIV infections.
What Did the Researchers Do and Find?
Between July 2005 and June 2006, 765 HIV infections were newly diagnosed in Switzerland. Using clinical and laboratory information collected at diagnosis, the researchers classified 195 of these infections as recent infections (occurring within the past year) and 161 as older infections. (The remaining infections could not be classified based on the available medical infomation.) The researchers then compared the ability of INNO-LIA (which measures antibodies to five HIV-1 antigens) and BED-EIA to distinguish recent from older HIV infections. BED-EIA correctly identified as recent 65% of the infections classified as recent based on the clinical information, and identified as older 80% of the infections classified as older based on the clinical information. In other words, this test was 65% sensitive (able to detect 65% of the truly recent infections as defined in this study) and was 80% specific (80% accurate in eliminating non-recent infections.) The two best algorithms (mathematical procedures) for converting INNO-LIA data into estimates of recent HV infections had sensitivities of 50% and 40% and specificities of 95% and 99%, respectively. Using actual test results and taking into account these sensitivities and specificities gave estimates of 35% and 33% for the proportion of the whole study population that had been recently infected. BED-EIA gave an estimate of 37%. Finally, a widely used window-based algorithm for recency estimation that uses the numbers of cases that are defined as recent by BED-EIA and the length of the window period for BED-EIA to calculate the annual number of new infections in populations indicated that 41% of the whole study population had been recently infected.
What Do These Findings Mean?
These findings indicate that numbers of recent HIV infections can be extracted from the INNO-LIA HIV diagnostic test and are comparable to those obtained using a window-based algorithm. The test could, therefore, provide a cost-effective means to improve HIV surveillance in countries like Switzerland that already use it for HIV diagnosis. However, because this approach relies on knowing the sensitivity and specificity of the INNO-LIA algorithms, which may vary between populations, the use of these algorithms to estimate numbers of recent HIV infections must be preceded by an assessment of their sensitivity and specificity in each new setting.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040343.
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including fact sheets on the symptoms of HIV infection, HIV testing, and a chapter on laboratory tests for HIV antibodies
NAM, a UK registered charity, provides information about all aspects of HIV and AIDS, including fact sheets on the stages of HIV infection and HIV testing
The US Centers for Disease Control and Prevention (CDC) provides information on HIV/AIDS, including information on HIV testing and on HIV surveillance by the CDC (in English and Spanish)
Information is available from Avert, an international AIDS charity, on the stages of HIV infection and on HIV testing
Details on the US Centers for Disease Control and Prevention and the World Health Organiztion HIV classification systems are available from the US Department of Veterans Affairs
doi:10.1371/journal.pmed.0040343
PMCID: PMC2100138  PMID: 18052604
20.  Voluntary Medical Male Circumcision: Modeling the Impact and Cost of Expanding Male Circumcision for HIV Prevention in Eastern and Southern Africa 
PLoS Medicine  2011;8(11):e1001132.
Emmanuel Njeuhmeli and colleagues estimate the impact and cost of scaling up adult medical male circumcision in 13 priority countries in eastern and southern Africa, finding that reaching 80% coverage and maintaining it until 2025 would avert 3.36 million new HIV infections.
Background
There is strong evidence showing that voluntary medical male circumcision (VMMC) reduces HIV incidence in men. To inform the VMMC policies and goals of 13 priority countries in eastern and southern Africa, we estimate the impact and cost of scaling up adult VMMC using updated, country-specific data.
Methods and Findings
We use the Decision Makers' Program Planning Tool (DMPPT) to model the impact and cost of scaling up adult VMMC in Botswana, Lesotho, Malawi, Mozambique, Namibia, Rwanda, South Africa, Swaziland, Tanzania, Uganda, Zambia, Zimbabwe, and Nyanza Province in Kenya. We use epidemiologic and demographic data from recent household surveys for each country. The cost of VMMC ranges from US$65.85 to US$95.15 per VMMC performed, based on a cost assessment of VMMC services aligned with the World Health Organization's considerations of models for optimizing volume and efficiencies. Results from the DMPPT models suggest that scaling up adult VMMC to reach 80% coverage in the 13 countries by 2015 would entail performing 20.34 million circumcisions between 2011 and 2015 and an additional 8.42 million between 2016 and 2025 (to maintain the 80% coverage). Such a scale-up would result in averting 3.36 million new HIV infections through 2025. In addition, while the model shows that this scale-up would cost a total of US$2 billion between 2011 and 2025, it would result in net savings (due to averted treatment and care costs) amounting to US$16.51 billion.
Conclusions
This study suggests that rapid scale-up of VMMC in eastern and southern Africa is warranted based on the likely impact on the region's HIV epidemics and net savings. Scaling up of safe VMMC in eastern and southern Africa will lead to a substantial reduction in HIV infections in the countries and lower health system costs through averted HIV care costs.
Please see later in the article for the Editors' Summary.
Editors' Summary
Background
Every year, about 2.5 million people (mainly in sub-Saharan Africa) become infected with HIV, the virus that causes AIDS. There is no cure for HIV/AIDS. Consequently, prevention of HIV transmission is very important. Because the most common HIV transmission route is through unprotected sex with an infected partner, individuals can reduce their risk of HIV infection by abstaining from sex, by having only one or a few partners, and by using male or female condoms. There is also strong evidence that voluntary medical male circumcision (VMMC)—the removal of the foreskin, the loose fold of skin that covers the head of the penis—reduces the heterosexual acquisition of HIV in men by about 60%. In 2007, the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) recommended that VMMC should be offered to men as part of comprehensive HIV risk reduction programs in settings with generalized HIV epidemics and low levels of male circumcision. They also prioritized 13 countries in eastern and southern Africa for VMMC program scale-up.
Why Was This Study Done?
The impact of VMMC scale-up in terms of HIV infections and AIDS deaths averted (epidemiologic impact) is expected to be large, and the intervention should also reduce the costs associated with the treatment, care, and support of infected individuals. However, VMMC scale-up will require substantial funding and considerable effort by countries—many of which have weak health systems and limited resources—to train personnel, equip facilities, and provide the necessary commodities. To support planning for VMMC scale-up, the United States Agency for International Development Health Policy Initiative has collaborated with UNAIDS to develop the Decision Makers' Program Planning Tool (DMPPT), a mathematical model that allows analysts and decision makers to estimate the epidemiologic impact and cost of alternative VMMC scale-up programs. In this study, the researchers use DMPPT to estimate the impact and cost of scaling up adult VMMC in the 13 priority countries in eastern and southern Africa.
What Did the Researchers Do and Find?
The researchers derived VMMC unit costs for each priority country based on a cost assessment undertaken in Zimbabwe, one of the first countries to scale up VMMC services using WHO's “Models for Optimizing Volume and Efficiencies” (MOVE) guidelines. They fed these costs and recent epidemiologic data (including HIV infection rates and the effectiveness of VMMC in preventing HIV transmission) and demographic data (including the adult population size and pre-scale-up male circumcision prevalence) collected in each country into the DMPPT, together with information on the lifetime costs of HIV treatment. Results from running the DMPPT model suggest that scaling up adult VMMC to reach 80% coverage in the 13 priority countries by 2015 would require 20.33 million circumcisions to be completed between 2011 and 2015. To maintain this coverage, a further 8.42 million circumcisions would be required between 2016 and 2025. Such a scale-up would avert 3.36 million new HIV infections through 2025 and would cost US$2,000,000,000 between 2011 and 2025. However, it would result in net savings (because of averted treatment and care costs) of US$16,510,000,000.
What Do These Findings Mean?
These findings suggest that rapid VMMC scale-up in eastern and southern Africa is warranted, given its likely impact on the region's HIV epidemics and the resultant cost savings. However, the accuracy of these findings depends on the assumptions built into the DMPPT and on the data fed into it. For example, there could be risk behavior changes after circumcision. That is, risky sexual behaviors may increase in men who have been circumcised. However, the researchers show that, except in Rwanda, post-circumcision risk behavior change is unlikely to completely reverse the benefits of VMMC. These modeling results also assume that men seeking out VMMC services are typical of the general male population, but if they are actually at unusually low risk of HIV infection, then the benefits of VMMC reported here are likely to be overestimated. Finally, these findings assume 80% VMMC coverage. This may be optimistic, although results from Kenya indicate that this target is achievable. Thus, countries and their international partners must allocate sufficient resources to VMMC scale-up to achieve high coverage rates if they are to take full advantage of the benefits predicted here for VMMC scale-up.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001132.
This study is part of a PLoS Collection of articles on http://www.ploscollections.org/VMMC2011 and is further discussed in a PLoS Medicine Review Article by Hankins et al. (http://dx.doi.org/10.1371/journal.pmed.1001127)
Information is available from WHO, UNAIDS, and PEPFAR on all aspects of HIV/AIDS; the 2011WHO/UNAIDS progress report on VMMC scale-up in the 13 priority countries is available
NAM/aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and information on male circumcision for the prevention of HIV transmission
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on all aspects of HIV prevention, and on HIV/AIDS in Africa (in English and Spanish)
The Clearinghouse on Male Circumcision, a resource provided by WHO, UNAIDS, and other international bodies, provides information and tools for VMMC policy development and program implementation, including information on the DMPPT and the MOVE guidance
Personal stories about living with HIV/AIDS are available through Avert, through NAM/aidsmap, and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001132
PMCID: PMC3226464  PMID: 22140367
21.  Episodic Sexual Transmission of HIV Revealed by Molecular Phylodynamics 
PLoS Medicine  2008;5(3):e50.
Background
The structure of sexual contact networks plays a key role in the epidemiology of sexually transmitted infections, and their reconstruction from interview data has provided valuable insights into the spread of infection. For HIV, the long period of infectivity has made the interpretation of contact networks more difficult, and major discrepancies have been observed between the contact network and the transmission network revealed by viral phylogenetics. The high rate of HIV evolution in principle allows for detailed reconstruction of links between virus from different individuals, but often sampling has been too sparse to describe the structure of the transmission network. The aim of this study was to analyze a high-density sample of an HIV-infected population using recently developed techniques in phylogenetics to infer the short-term dynamics of the epidemic among men who have sex with men (MSM).
Methods and Findings
Sequences of the protease and reverse transcriptase coding regions from 2,126 patients, predominantly MSM, from London were compared: 402 of these showed a close match to at least one other subtype B sequence. Nine large clusters were identified on the basis of genetic distance; all were confirmed by Bayesian Monte Carlo Markov chain (MCMC) phylogenetic analysis. Overall, 25% of individuals with a close match with one sequence are linked to 10 or more others. Dated phylogenies of the clusters using a relaxed clock indicated that 65% of the transmissions within clusters took place between 1995 and 2000, and 25% occurred within 6 mo after infection. The likelihood that not all members of the clusters have been identified renders the latter observation conservative.
Conclusions
Reconstruction of the HIV transmission network using a dated phylogeny approach has revealed the HIV epidemic among MSM in London to have been episodic, with evidence of multiple clusters of transmissions dating to the late 1990s, a period when HIV prevalence is known to have doubled in this population. The quantitative description of the transmission dynamics among MSM will be important for parameterization of epidemiological models and in designing intervention strategies.
Using viral genotype data from HIV drug resistance testing at a London clinic, Andrew Leigh Brown and colleagues derive the structure of the transmission network through phylogenetic analysis.
Editors' Summary
Background.
Human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS), is mainly spread through unprotected sex with an infected partner. Like other sexually transmitted diseases, HIV/AIDS spreads through networks of sexual contacts. The characteristics of these complex networks (which include people who have serial sexual relationships with single partners and people who have concurrent sexual relationships with several partners) affect how quickly diseases spread in the short term and how common the disease is in the long term. For many sexually transmitted diseases, sexual contact networks can be reconstructed from interview data. The information gained in this way can be used for partner notification so that transmitters of the disease and people who may have been unknowingly infected can be identified, treated, and advised about disease prevention. It can also be used to develop effective community-based prevention strategies.
Why Was This Study Done?
Although sexual contact networks have provided valuable information about the spread of many sexually transmitted diseases, they cannot easily be used to understand HIV transmission patterns. This is because the period of infectivity with HIV is long and the risk of infection from a single sexual contact with an infected person is low. Another way to understand the spread of HIV is through phylogenetics, which examines the genetic relatedness of viruses obtained from different individuals. Frequent small changes in the genetic blueprint of HIV allow the virus to avoid the human immune response and to become resistant to antiretroviral drugs. In this study, the researchers use recently developed analytical methods, viral sequences from a large proportion of a specific HIV-infected population, and information on when each sample was taken, to learn about transmission of HIV/AIDS in London among men who have sex with men (MSM; a term that encompasses gay, bisexual, and transgendered men and heterosexual men who sometimes have sex with men). This new approach, which combines information on viral genetic variation and viral population dynamics, is called “molecular phylodynamics.”
What Did the Researchers Do and Find?
The researchers compared the sequences of the genes encoding the HIV-1 protease and reverse transcriptase from more than 2,000 patients, mainly MSM, attending a large London HIV clinic between 1997 and 2003. 402 of these sequences closely matched at least one other subtype B sequence (the HIV/AIDS epidemic among MSM in the UK primarily involves HIV subtype B). Further analysis showed that the patients from whom this subset of sequences came formed six clusters of ten or more individuals, as well as many smaller clusters, based on the genetic relatedness of their HIV viruses. The researchers then used information on the date when each sample was collected and a “relaxed clock” approach (which accounts for the possibility that different sequences evolve at different rates) to determine dated phylogenies (patterns of genetic relatedness that indicate when gene sequences change) for the clusters. These phylogenies indicated that at least in one in four transmissions between the individuals in the large clusters occurred within 6 months of infection, and that most of the transmissions within each cluster occurred over periods of 3–4 years during the late 1990s.
What Do These Findings Mean?
This phylodynamic reconstruction of the HIV transmission network among MSM in a London clinic indicates that the HIV epidemic in this population has been episodic with multiple clusters of transmission occurring during the late 1990s, a time when the number of HIV infections in this population doubled. It also suggests that transmission of the virus during the early stages of HIV infection is likely to be an important driver of the epidemic. Whether these results apply more generally to the MSM population at risk for transmitting or acquiring HIV depends on whether the patients in this study are representative of that group. Additional studies are needed to determine this, but if the patterns revealed here are generalizable, then this quantitative description of HIV transmission dynamics should help in the design of strategies to strengthen HIV prevention among MSM.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050050.
Read a related PLoS Medicine Perspective article
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including a list of organizations that provide information for gay men and MSM
The US Centers for Disease Control and Prevention provides information on HIV/AIDS and on HIV/AIDS among MSM (in English and Spanish)
Information is available from Avert, an international AIDS charity, on HIV, AIDS, and men who have sex with men
The Center for AIDS Prevention Studies (University of California, San Francisco) provides information on sexual networks and HIV prevention
The US National Center for Biotechnology Information provides a science primer on molecular phylogenetics
UK Collaborative Group on HIV Drug Resistance maintains a database of resistance tests
HIV i-Base offers HIV treatment information for health-care professionals and HIV-positive people
The NIH-funded HIV Sequence Database contains data on genetic sequences, resistance, immunology, and vaccine trials
doi:10.1371/journal.pmed.0050050
PMCID: PMC2267814  PMID: 18351795
22.  Effects of Genital Ulcer Disease and Herpes Simplex Virus Type 2 on the Efficacy of Male Circumcision for HIV Prevention: Analyses from the Rakai Trials 
PLoS Medicine  2009;6(11):e1000187.
Ron Gray and colleagues analyze data from two circumcision trials in Uganda to assess how HSV-2 status and genital ulcer disease affect the procedure's ability to reduce HIV infection.
Background
Randomized trials show that male circumcision (MC) reduces the incidence of HIV and herpes simplex virus type 2 (HSV-2) infections, and symptomatic genital ulcer disease (GUD). We assessed the role of GUD and HSV-2 in the protection against HIV afforded by MC.
Methods and Findings
HIV-uninfected men were randomized to immediate (n = 2,756) or delayed MC (n = 2,775) in two randomized trials in Rakai, Uganda. GUD symptoms, HSV-2 status, and HIV acquisition were determined at enrollment and at 6, 12, and 24 mo of follow up. Ulcer etiology was assessed by PCR. We estimated the prevalence and prevalence risk ratios (PRRs) of GUD in circumcised versus uncircumcised men and assessed the effects of HSV-2 serostatus as a risk-modifying factor for GUD. We estimated the proportion of the effect of MC on HIV acquisition that was mediated by symptomatic GUD, and by HSV-2 infection. Circumcision significantly reduced symptomatic GUD in HSV-2-seronegative men (PRR = 0.51, 95% [confidence interval] CI 0.43–0.74), HSV-2-seropositive men (PRR = 0.66, 95% CI 0.51–0.69), and in HSV-2 seroconverters (PRR = 0.48, 95% CI 0.30–0.79). The proportion of acute ulcers due to HSV-2 detected by PCR was 48.0% in circumcised men and 39.3% in uncircumcised men (χ2 p = 0.62). Circumcision reduced the risk of HIV acquisition in HSV-2 seronegative men (incidence rate ratio [IRR] = 0.34, 95% CI 0.15–0.81), and potentially in HSV-2 seroconverters (IRR = 0.56, 95% CI 0.19–1.57; not significant), but not in men with prevalent HSV-2 at enrollment (IRR = 0.89, 95% CI 0.49–1.60). The proportion of reduced HIV acquisition in circumcised men mediated by reductions in symptomatic GUD was 11.2% (95% CI 5.0–38.0), and the proportion mediated by reduced HSV-2 incidence was 8.6% (95% CI −1.2 to 77.1).
Conclusions
Circumcision reduced GUD irrespective of HSV-2 status, but this reduction played only a modest role in the protective effect of circumcision on HIV acquisition.
NIH Trial registration
ClinicalTrials.gov NCT00425984
Gates Foundation Trial registration
ClinicalTrials.gov NCT00124878
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Acquired immunodeficiency syndrome (AIDS) has killed more than 25 million people since 1981, and more than 30 million people (22 million in sub-Saharan Africa alone) are now infected with the human immunodeficiency virus (HIV), which causes AIDS. There is no cure for HIV/AIDS. Consequently, prevention of HIV transmission is extremely important. Because HIV is most often spread through unprotected sex with an infected partner, individuals can reduce their risk of becoming infected with HIV by abstaining from sex, by having one or a few partners, and by always using a male or female condom. In addition, three large trials in sub-Saharan Africa (including one in Rakai, Uganda) recently reported that male circumcision—the removal of the foreskin, a loose fold of skin that covers the head of the penis—can halve HIV transmission rates in men. Thus, as part of its HIV prevention strategy, the World Health Organization now recommends that male circumcision programs be scaled up in countries where there is a generalized HIV epidemic and where few men are circumcised.
Why Was This Study Done?
It is still not clear why male circumcision reduces HIV acquisition in men. Certainly, the foreskin contains many cells that HIV can infect and the foreskin's delicate lining is thought to be particularly vulnerable to HIV infection partly because intercourse can cause small tears in it through which HIV can enter the body. But male circumcision also reduces genital ulcer disease—sores on the penis and other genital organs caused by infection with several sexually transmitted organisms including the herpes simplex virus type 2 (HSV-2). Genital ulcer disease, particularly when caused by HSV-2, is thought to increase a person's risk of acquiring HIV, so could male circumcision reduce HIV transmission rates because of its beneficial effects on genital ulcer disease rather than through its removal of foreskin tissue with its rich source of HIV target cells? In this study, the researchers investigate this question by re-analyzing data collected in two Ugandan trials of male circumcision for HIV prevention.
What Did the Researchers Do and Find?
In the Ugandan trials, the researchers randomly assigned about 5,500 HIV-uninfected men to immediate circumcision or to circumcision 24 months later. At enrollment, they asked the men whether they had any symptoms of genital ulcer disease (for example, a painful penile sore or genital itching), examined the men's genital areas, and took blood samples to test for HSV-2 infection. The researchers repeated these examinations and tests at 6 months, 12 months, and 24 months and tested the study participants for HIV infection. The researchers' statistical analysis of these data shows that circumcision approximately halved symptomatic genital ulcer disease in the study participants irrespective of their HSV-2 infection status. Circumcision reduced the risk of HIV acquisition in men without HSV-2 infection by two-thirds but did not affect HIV acquisition among men infected with HSV-2 at enrollment. Among the men who became infected with HSV-2 during the study, circumcision reduced the risk of HIV acquisition but this reduction in risk was not statistically significant. That is, it could have happened by chance. Finally, the researchers calculated that 11.2% of the observed reduction in HIV acquisition associated with circumcision was mediated by reductions in symptomatic genital ulcer disease and 8.6% was mediated by reductions in HSV-2 infections.
What Do These Findings Mean?
The findings of this study are limited by the small number of people in some of the subgroups analyzed and by genital ulcer disease being self-reported. Furthermore, the validity of some of the findings may be compromised because the analysis described here was not specified in the original trial protocol. Nevertheless, these findings suggest that the reduction of genital ulceration following circumcision plays only a minor part in the ability of male circumcision to reduce HIV acquisition in men. They also suggest that circumcision reduces genital ulcer disease primarily by reducing the rate of nonherpetic ulceration, including sores caused by mild trauma during intercourse. Thus, the researchers conclude, most of the reduction in HIV acquisition provided by male circumcision may be attributable to the removal of vulnerable foreskin tissue containing HIV target cells.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000187.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV and AIDS in Uganda, and on circumcision and HIV (in English and Spanish)
More information about male circumcision is available from the Clearinghouse on Male Circumcision
Information on the Rakai HIV prevention trial is available
The MedlinePlus Encyclopedia has a page on male genital sores (in English and Spanish)
The US National Institute of Allergy and Infectious Diseases provides information about genital herpes
The US Centers for Disease Control and Prevention also provides information on genital herpes (in English and Spanish)
doi:10.1371/journal.pmed.1000187
PMCID: PMC2771764  PMID: 19936044
23.  Prioritizing CD4 Count Monitoring in Response to ART in Resource-Constrained Settings: A Retrospective Application of Prediction-Based Classification 
PLoS Medicine  2012;9(4):e1001207.
Luis Montaner and colleagues retrospectively apply a potential capacity-saving CD4 count prediction tool to a cohort of HIV patients on antiretroviral therapy.
Background
Global programs of anti-HIV treatment depend on sustained laboratory capacity to assess treatment initiation thresholds and treatment response over time. Currently, there is no valid alternative to CD4 count testing for monitoring immunologic responses to treatment, but laboratory cost and capacity limit access to CD4 testing in resource-constrained settings. Thus, methods to prioritize patients for CD4 count testing could improve treatment monitoring by optimizing resource allocation.
Methods and Findings
Using a prospective cohort of HIV-infected patients (n = 1,956) monitored upon antiretroviral therapy initiation in seven clinical sites with distinct geographical and socio-economic settings, we retrospectively apply a novel prediction-based classification (PBC) modeling method. The model uses repeatedly measured biomarkers (white blood cell count and lymphocyte percent) to predict CD4+ T cell outcome through first-stage modeling and subsequent classification based on clinically relevant thresholds (CD4+ T cell count of 200 or 350 cells/µl). The algorithm correctly classified 90% (cross-validation estimate = 91.5%, standard deviation [SD] = 4.5%) of CD4 count measurements <200 cells/µl in the first year of follow-up; if laboratory testing is applied only to patients predicted to be below the 200-cells/µl threshold, we estimate a potential savings of 54.3% (SD = 4.2%) in CD4 testing capacity. A capacity savings of 34% (SD = 3.9%) is predicted using a CD4 threshold of 350 cells/µl. Similar results were obtained over the 3 y of follow-up available (n = 619). Limitations include a need for future economic healthcare outcome analysis, a need for assessment of extensibility beyond the 3-y observation time, and the need to assign a false positive threshold.
Conclusions
Our results support the use of PBC modeling as a triage point at the laboratory, lessening the need for laboratory-based CD4+ T cell count testing; implementation of this tool could help optimize the use of laboratory resources, directing CD4 testing towards higher-risk patients. However, further prospective studies and economic analyses are needed to demonstrate that the PBC model can be effectively applied in clinical settings.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
AIDS has killed nearly 30 million people since 1981, and about 34 million people (most of them living in low- and middle-income countries) are now infected with HIV, the virus that causes AIDS. HIV destroys immune system cells (including CD4 cells, a type of lymphocyte and one of the body's white blood cell types), leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, most HIV-infected people died within ten years of infection. Then, in 1996, antiretroviral therapy (ART) became available, and for people living in affluent countries, HIV/AIDS became a chronic condition. However, ART was expensive, and for people living in developing countries, HIV/AIDS remained a fatal illness. In 2003, HIV was declared a global health emergency, and in 2006, the international community set itself the target of achieving universal access to ART by 2010. By the end of 2010, only 6.6 million of the estimated 15 million people in need of ART in developing countries were receiving ART.
Why Was This Study Done?
One factor that has impeded progress towards universal ART coverage has been the limited availability of trained personnel and laboratory facilities in many developing countries. These resources are needed to determine when individuals should start ART—the World Health Organization currently recommends that people start ART when their CD4 count drops below 350 cells/µl—and to monitor treatment responses over time so that viral resistance to ART is quickly detected. Although a total lymphocyte count can be used as a surrogate measure to decide when to start treatment, repeated CD4 cell counts are the only way to monitor immunologic responses to treatment, a level of monitoring that is rarely sustainable in resource-constrained settings. A method that optimizes resource allocation by prioritizing who gets tested might be one way to improve treatment monitoring. In this study, the researchers applied a new tool for prioritizing laboratory-based CD4 cell count testing in resource-constrained settings to patient data that had been previously collected.
What Did the Researchers Do and Find?
The researchers fitted a mixed-effects statistical model to repeated CD4 count measurements from HIV-infected individuals from seven sites around the world (including some resource-limited sites). They then used model-derived estimates to apply a mathematical tool for predicting—from a CD4 count taken at the start of treatment, and white blood cell counts and lymphocyte percentage measurements taken later—whether CD4 counts would be above 200 cells/µl (the original threshold recommended for ART initiation) and 350 cells/µl (the current recommended threshold) for up to three years after ART initiation. The tool correctly classified 91.5% of the CD4 cell counts that were below 200 cells/µl in the first year of ART. With this threshold, the potential savings in CD4 testing capacity was 54.3%. With a CD4 count threshold of 350 cells/µl, the potential savings in testing capacity was 34%. The results over a three-year follow-up were similar. When applied to six representative HIV-positive individuals, the tool correctly predicted all the CD4 counts above 200 cells/µl, although some individuals who had a predicted CD4 count of less than 200 cells/µl actually had a CD4 count above this threshold. Thus, none of these individuals would have been exposed to an undetected dangerous CD4 count, but the application of the tool would have saved 57% of the CD4 laboratory tests done during the first year of ART.
What Do These Findings Mean?
These findings support the use of this new tool—the prediction-based classification (PBC) algorithm—for predicting a drop in CD4 count below a clinically meaningful threshold in HIV-infected individuals receiving ART. Further studies are now needed to demonstrate the feasibility, clinical effectiveness, and cost-effectiveness of this approach, to find out whether the tool can be used over extended periods of time, and to investigate whether the accuracy of its predictions can be improved by, for example, adding in periodic CD4 testing. Provided these studies confirm its early promise, the researchers suggest that the PBC algorithm could be used as a “triage” tool to direct available laboratory testing capacity to high-priority individuals (those likely to have a dangerously low CD4 count). By optimizing the use of limited laboratory resources in this and other ways, the PBC algorithm could therefore help to maintain and expand ART programs in low- and middle-income countries.
Additional Information
Please access these web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001207.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV/AIDS treatment and care and on universal access to AIDS treatment (in English and Spanish)
The World Health Organization provides information about universal access to AIDS treatment (in several languages)
More information about universal access to HIV treatment, prevention, care, and support is available from UNAIDS
Patient stories about living with HIV/AIDS are available through Avert and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001207
PMCID: PMC3328436  PMID: 22529752
24.  Uptake of Workplace HIV Counselling and Testing: A Cluster-Randomised Trial in Zimbabwe 
PLoS Medicine  2006;3(7):e238.
Background
HIV counselling and testing is a key component of both HIV care and HIV prevention, but uptake is currently low. We investigated the impact of rapid HIV testing at the workplace on uptake of voluntary counselling and testing (VCT).
Methods and Findings
The study was a cluster-randomised trial of two VCT strategies, with business occupational health clinics as the unit of randomisation. VCT was directly offered to all employees, followed by 2 y of open access to VCT and basic HIV care. Businesses were randomised to either on-site rapid HIV testing at their occupational clinic (11 businesses) or to vouchers for off-site VCT at a chain of free-standing centres also using rapid tests (11 businesses). Baseline anonymised HIV serology was requested from all employees.
HIV prevalence was 19.8% and 18.4%, respectively, at businesses randomised to on-site and off-site VCT. In total, 1,957 of 3,950 employees at clinics randomised to on-site testing had VCT (mean uptake by site 51.1%) compared to 586 of 3,532 employees taking vouchers at clinics randomised to off-site testing (mean uptake by site 19.2%). The risk ratio for on-site VCT compared to voucher uptake was 2.8 (95% confidence interval 1.8 to 3.8) after adjustment for potential confounders. Only 125 employees (mean uptake by site 4.3%) reported using their voucher, so that the true adjusted risk ratio for on-site compared to off-site VCT may have been as high as 12.5 (95% confidence interval 8.2 to 16.8).
Conclusions
High-impact VCT strategies are urgently needed to maximise HIV prevention and access to care in Africa. VCT at the workplace offers the potential for high uptake when offered on-site and linked to basic HIV care. Convenience and accessibility appear to have critical roles in the acceptability of community-based VCT.
Editors' Summary
Background.
Since the first case of AIDS (acquired immunodeficiency syndrome) was reported 25 years ago, AIDS has become a major worldwide epidemic, with 3 million people dying from it in 2005. AIDS is caused by the human immunodeficiency virus (HIV), which is usually spread through unprotected sex with an infected partner. HIV damages the immune system, leaving infected individuals unable to fight off other viruses and bacteria. HIV infections can be treated with drugs know as “antiretrovirals,” and in an effort to deal with the global epidemic, world leaders have committed themselves to providing universal access to these drugs for everyone who needs them by 2010. Unfortunately, although access to antiretrovirals is rapidly increasing, so is the number of people infected with HIV. Last year, there were about 5 million new HIV infections, suggesting that more emphasis on prevention will be needed to halt or reverse the spread of HIV and AIDS. An important part of prevention is testing for HIV infection, but globally only 10% of people who need testing can access it. And even where such services are available, few people use them because of the stigma attached to HIV infection and fear of discrimination.
Why Was This Study Done?
There is limited understanding about the factors that determine whether an individual will decide to have an HIV test. Yet, to reduce HIV spread, as many people at risk of infection must be tested as possible. Previous studies on VCT—a combination of voluntary testing and counseling about the implications of HIV infection and how to avoid transmitting the virus—have indicated that the convenience of getting the test, whether the test is directly offered, and the attitude of staff supplying it are all very important. In this study, the researchers asked whether providing VCT in the workplace could improve the “uptake” of HIV testing in Africa, where the HIV/AIDS epidemic is most widespread.
What Did the Researchers Do and Find?
The researchers identified businesses with occupational health clinics in Zimbabwe, a country where 25% of adults carry HIV, and divided them into two “intervention” groups. Employees at half the businesses were offered “on-site VCT”—pre-test counseling followed by same-day on-site rapid testing, results, and post-test counseling. Employees at the other businesses had the same pre-test counseling but were offered a voucher for an HIV test at an off-site testing center and a later appointment to discuss the results—so-called off-site VCT. Everyone had the same access to limited HIV care should they need it. Although half of the employees at the on-site VCT businesses took up the option of HIV testing, only a fifth of employees at the off-site VCT businesses accepted vouchers for testing, and only one in five of these people actually used their voucher. This means that on-site VCT resulted in about 12 times as many HIV tests as off-site VCT. In both interventions, most of the people who accepted testing did so soon after entering the study and very few people were tested more than once. Finally, people 25 years old or younger, manual workers, and single people were most likely to accept testing in both interventions.
What Do These Findings Mean?
These results suggest that on-site VCT in the workplace might be one way to improve uptake of HIV testing in Africa from its current low level and that providing VCT intermittently might be as effective as continuous provision. Importantly, say the researchers, the results of their study show that a relatively minor change in accessibility to testing can translate into a major difference in test uptake. This may hold true in non-occupational settings. However, these observations need to be repeated in more businesses and other settings, including those where there is no linked HIV care, before they can be generalized. Also, this study reports on the acceptability of this approach to providing VCT, but not on its impact on HIV prevention. As such the results do not indicate whether workplace VCT prevents HIV spread as effectively as other ways of delivering VCT. This will require research investigating how HIV incidence among HIV-negative employees and the partners of HIV-positive employees are affected by different VCT strategies.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030238.
• United States National Institute of Allergy and Infectious Diseases factsheet on HIV infection and AIDS
• United States Department of Health and Human Services information on HIV/AIDS treatment, prevention, and research
• US Centers for Disease Control and Prevention information on HIV/AIDS
• UNAIDS (Joint United Nations Programme on HIV/AIDS) information on political issues related to the HIV/AIDS epidemic and the 2004 UNAIDS/World Health Organization policy statement on HIV testing
•  Aidsmap: information on HIV and AIDS provided by the charity NAM, which includes the latest scientific and political news
• MedlinePlus encyclopedia entry on HIV/AIDS
Voluntary counseling and testing for HIV has the potential for high uptake when it is offered on-site at the workplace and linked to basic HIV care.
doi:10.1371/journal.pmed.0030238
PMCID: PMC1483908  PMID: 16796402
25.  A Novel Substrate-Based HIV-1 Protease Inhibitor Drug Resistance Mechanism 
PLoS Medicine  2007;4(1):e36.
Background
HIV protease inhibitor (PI) therapy results in the rapid selection of drug resistant viral variants harbouring one or two substitutions in the viral protease. To combat PI resistance development, two approaches have been developed. The first is to increase the level of PI in the plasma of the patient, and the second is to develop novel PI with high potency against the known PI-resistant HIV protease variants. Both approaches share the requirement for a considerable increase in the number of protease mutations to lead to clinical resistance, thereby increasing the genetic barrier. We investigated whether HIV could yet again find a way to become less susceptible to these novel inhibitors.
Methods and Findings
We have performed in vitro selection experiments using a novel PI with an increased genetic barrier (RO033-4649) and demonstrated selection of three viruses 4- to 8-fold resistant to all PI compared to wild type. These PI-resistant viruses did not have a single substitution in the viral protease. Full genomic sequencing revealed the presence of NC/p1 cleavage site substitutions in the viral Gag polyprotein (K436E and/or I437T/V) in all three resistant viruses. These changes, when introduced in a reference strain, conferred PI resistance. The mechanism leading to PI resistance is enhancement of the processing efficiency of the altered substrate by wild-type protease. Analysis of genotypic and phenotypic resistance profiles of 28,000 clinical isolates demonstrated the presence of these NC/p1 cleavage site mutations in some clinical samples (codon 431 substitutions in 13%, codon 436 substitutions in 8%, and codon 437 substitutions in 10%). Moreover, these cleavage site substitutions were highly significantly associated with reduced susceptibility to PI in clinical isolates lacking primary protease mutations. Furthermore, we used data from a clinical trial (NARVAL, ANRS 088) to demonstrate that these NC/p1 cleavage site changes are associated with virological failure during PI therapy.
Conclusions
HIV can use an alternative mechanism to become resistant to PI by changing the substrate instead of the protease. Further studies are required to determine to what extent cleavage site mutations may explain virological failure during PI therapy.
Changes in the cleavage site of the Gag substrate for the HIV protease can convey resistance to protease inhibitors and might contribute to virologic failure during therapy that includes these drugs.
Editors' Summary
Background.
Twenty-five years ago, infection with the human immunodeficiency virus (HIV)—the causative agent of AIDS—was a death sentence. However, drugs that attack various stages of the HIV life cycle were soon developed that, although not curing the infection, kept it in check when used in combination and greatly increased the life expectancy of people infected with HIV. Unfortunately, viruses resistant to these drugs have rapidly emerged and antiviral therapy now fails in many patients. The use of HIV protease inhibitors (PIs) in combination therapies, for example, has led to the stepwise selection of viral variants resistant to these drugs. Resistance is first acquired when the viral protease changes so that PIs no longer bind to it and inhibit it efficiently. These changes often reduce the efficiency with which the protease binds its substrates—polyproteins called Gag and GagPol that it chops up into smaller proteins to make new viral particles. So the next step is the accumulation of changes elsewhere in the protease that make it work better, and sometimes changes in its substrate that make it easier to cut; these compensatory changes do not directly affect viral resistance to PIs.
Why Was This Study Done?
To prevent viruses with resistance to PIs emerging, drug doses are kept high in patients and new PIs are being developed with high potency against known PI-resistant HIV variants. Both approaches set a “high genetic barrier” to the development of PI resistance by ensuring that HIV has to incorporate many changes in its protease to become resistant. But, the HIV genome naturally changes—mutates—very rapidly, so novel HIV variants could emerge that are less susceptible to the new potent PIs without the virus having to leap this high genetic barrier. In this study, the researchers have investigated whether HIV can find an alternative route to PI resistance that does not involve the introduction of multiple changes into its protease.
What Did the Researchers Do and Find?
The researchers took wild-type HIV and treated it in the laboratory with a new PI regimen that has a high genetic barrier. By gradually increasing its concentration, the researchers selected three viral populations that were able to grow in 4- to 8-fold higher concentrations of the PI than wild-type virus. None of these populations had mutations in the viral protease. Instead, they all had mutations near one of the sites—the NC/p1 site—where the protease normally cuts the Gag polyprotein. These mutations, the researchers report, enhanced the overall efficiency with which the wild-type protease cleaved the polyprotein, and a selection experiment with another PI showed that the development of PI resistance through alterations near the NC/p1 cleavage site was not unique to one PI. The researchers also investigated the potential clinical significance of this new drug resistance mechanism by looking for the same mutations in nearly 30,000 patient samples. Many of the samples did indeed have these mutations. Finally, they showed that mutations at the NC/p1 cleavage site were associated with virological failure (increased viral replication) during PI therapy in an ongoing clinical trial.
What Do These Findings Mean?
These results suggest that increased polyprotein processing because of mutations in the natural substrate of the HIV protease might be a new mechanism by which HIV can become resistant to PIs. This strategy, which occurs in the laboratory and in patients, allows HIV to develop PI resistance without the need for multiple changes in its protease and so avoids the high genetic barrier to resistance that new PIs provide. Clinical studies are now needed to test which of the mutations seen in this study contribute to virological failure, whether the degree of this failure is clinically relevant, and whether these substrate mutations enhance the effect of protease mutations. If the clinical importance of the new mechanism is confirmed, genetic examination of both the polyprotein and the protease will be needed when trying to figure out why a PI-containing therapy is failing in individual patients. Furthermore, it will be necessary to test whether this mechanism can contribute to the development of resistance when evaluating new drugs.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040036.
US National Institute of Allergy and Infectious Diseases factsheet on HIV infection and AIDS
US Department of Health and Human Services information on AIDS
US Centers for Disease Control and Prevention information on HIV/AIDS
Aidsmap information on HIV and AIDS provided by the charity NAM
BioAfrica, Bioinformatics for HIV Research, information on HIV-1 protease cleavage sites
doi:10.1371/journal.pmed.0040036
PMCID: PMC1769415  PMID: 17227139

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