To learn the attitudes and concerns of the local community on participating in research, infant feeding practices, and maternal nutrition in order to inform the design of a clinical trial in Lilongwe, Malawi on the safety and efficacy of antiretroviral and nutrition interventions to reduce postnatal transmission of HIV.
Formative research methods were used, including semi-structured interviews, focus group discussions, home observations, and taste trials. Data were collected, analyzed, and incorporated into the protocol within three months.
Participants were supportive of the clinical trial, although their overall understanding of research was limited. Mothers agreed that infants’ blood could be drawn by venipuncture, yet concern was raised about the amount of blood proposed to be collected from both infants and mothers. Data demonstrated that rapid breastfeeding cessation would be difficult and malnutrition could be a risk if infants were weaned early. Mothers selected a maternal supplement suitable for use in the clinical trial.
The protocol was rapidly modified to achieve cultural acceptability while maintaining study objectives. Without the formative research, several significant areas would have been undetected and may have jeopardized the implementation of the trial. Additional research was carried out to develop a meaningful informed consent process, the amount of blood collected was reduced to acceptable levels, and the protocol was modified to reduce the risk of malnutrition. Researchers who conduct clinical trials are encouraged to incorporate formative research into their protocol design to ensure participant understanding of the research, to safeguard participants, and to increase feasibility and acceptance of the clinical research in the community.
Qualitative research; ethics; clinical trial; HIV; Africa
Background. The Step Study tested whether an adenovirus serotype 5 (Ad5)–vectored human immunodeficiency virus (HIV) vaccine could prevent HIV acquisition and/or reduce viral load set-point after infection. At the first interim analysis, nonefficacy criteria were met. Vaccinations were halted; participants were unblinded. In post hoc analyses, more HIV infections occurred in vaccinees vs placebo recipients in men who had Ad5-neutralizing antibodies and/or were uncircumcised. Follow-up was extended to assess relative risk of HIV acquisition in vaccinees vs placebo recipients over time.
Methods. We used Cox proportional hazard models for analyses of vaccine effect on HIV acquisition and vaccine effect modifiers, and nonparametric and semiparametric methods for analysis of constancy of relative risk over time.
Results. One hundred seventy-two of 1836 men were infected. The adjusted vaccinees vs placebo recipients hazard ratio (HR) for all follow-up time was 1.40 (95% confidence interval [CI], 1.03–1.92; P = .03). Vaccine effect differed by baseline Ad5 or circumcision status during first 18 months, but neither was significant for all follow-up time. The HR among uncircumcised and/or Ad5-seropositive men waned with time since vaccination. No significant vaccine-associated risk was seen among circumcised, Ad5-negative men (HR, 0.97; P = 1.0) over all follow-up time.
Conclusions. The vaccine-associated risk seen in interim analysis was confirmed but waned with time from vaccination.
Clinical Trials Registration. NCT00095576.
The safety and immunogenicity of the MRK adenovirus type 5 (Ad5) HIV-1 clade B gag vaccine was assessed in an international Phase I trial. Three-hundred and sixty healthy HIV-uninfected adults were enrolled on five continents. Subjects received placebo or 1 × 109 or 1 × 1010 viral particles (vp) per dose of the MRKAd5 HIV-1 gag vaccine at day 1, week 4, and week 26. Immunogenicity was evaluated using an IFN-γ ELISPOT gag 15-mer assay with positive responses defined as ≥55 SFC/106 PBMCs and ≥4-fold over mock control. The vaccine was well tolerated. The most common adverse events were injection site reactions, headache, pyrexia, diarrhea, fatigue, and myalgia. At week 30, geometric mean ELISPOT responses were 24, 114, and 226 SFC/106 PBMCs in the placebo, 1 × 109 vp/dose, and 1 × 1010 vp/dose groups, respectively. Overall, responses to 1 × 1010 vp were 85% and 68% in subjects with low (≤200) and high (>200) baseline Ad5 titers, respectively. The MRKAd5 HIV-1 gag vaccine was immunogenic in diverse geographic regions. Gag ELISPOT responses were greater in the 1 × 1010 vp/dose groups than in the 1 × 109 vp/dose groups. Data from this first international study indicate that adenovirus-vectored vaccines are well tolerated and may be immunogenic in subjects from regions with high prevalence of preexisting Ad5 immunity.
Adenoviruses are among the most promising vectors for the development of an HIV vaccine. The results of the phase IIB study of the adenovirus serotype 5-based Merck Trivalent HIV vaccine have raised the concern that serological immunity to Ad5 could be linked to HIV acquisition risk in high-risk individuals. We examined the association between adenovirus serostatus and the rate of incident HIV infection in populations at elevated risk of HIV acquisition.
We performed a nested case-control study of Ad5 serostatus among 299 HIV-infected and 590 matched HIV-uninfected persons participating in MACS and in HPTN 039, a study of HSV-2 suppression among adults in the U.S., South America and Africa. Appropriate HIV cases and controls were identified in each cohort, and Ad5 neutralizing antibody titers were compared in these two groups.
In MACS and HPTN 039, the relative risks of incident HIV infection among Ad5 seropositive vs. Ad5 seronegative individuals were 1.1 (95% CI 0.8–1.5, p = 0.57) and 1.0 (95% CI 0.4 – 2.3, p = 0.99) respectively. HIV-1 acquisition rates did not vary significantly by Ad5 neutralizing antibody titer.
The presence of Ad5 neutralizing antibodies is not linked to the risk of HIV acquisition among populations at elevated risk of HIV infection.
Adenovirus; serology; MSM; HIV; acquisition risk; vaccine
Recombinant viruses hold promise as vectors for vaccines to prevent infectious diseases with significant global health impacts. One of their major limitations is that preexisting anti-vector neutralizing antibodies can reduce T cell responses to the insert antigens; however, the impact of vector-specific cellular immunity on subsequent insert-specific T cell responses has not been assessed in humans. Here, we have identified and compared adenovirus-specific and HIV-specific T cell responses in subjects participating in two HIV-1 vaccine trials using a vaccine vectored by adenovirus serotype 5 (Ad5). Higher frequencies of pre-immunization adenovirus-specific CD4+ T cells were associated with substantially decreased magnitude of HIV-specific CD4+ T cell responses and decreased breadth of HIV-specific CD8+ T cell responses in vaccine recipients, independent of type-specific preexisting Ad5-specific neutralizing antibody titers. Further, epitopes recognized by adenovirus-specific T cells were commonly conserved across many adenovirus serotypes, suggesting that cross-reactivity of preexisting adenovirus-specific T cells can extend to adenovirus vectors derived from rare serotypes. These findings provide what we believe to be a new understanding of how preexisting viral immunity may impact the efficacy of vaccines under current evaluation for prevention of HIV, tuberculosis, and malaria.
As more US HIV surveillance programs routinely use late HIV diagnosis to monitor and characterize HIV testing patterns, there is an increasing need to standardize how late HIV diagnosis is measured. In this study, we compared two measures of late HIV diagnosis, one based on time between HIV and AIDS, the other based on initial CD4+ results. Using data from Washington's HIV/AIDS Reporting System, we used multivariate logistic regression to identify predictors of late HIV diagnosis. We also conducted tests for trend to determine whether the proportion of cases diagnosed late has changed over time. Both measures lead us to similar conclusions about late HIV diagnosis, suggesting that being male, older, foreign-born, or heterosexual increase the likelihood of late HIV diagnosis. Our findings reaffirm the validity of a time-based definition of late HIV diagnosis, while at the same time demonstrating the potential value of a lab-based measure.
Purpose of review
Two phase IIb test of concept studies evaluated the replication-defective adenovirus type 5 vaccine MRK gag/pol/nef HIV vaccine to prevent infection or decrease early plasma viral load in disparate populations. The Step study enrolled men and women in the Americas, Caribbean and Australia; the Phambili trial enrolled men and women in South Africa, where the modes of sexual transmission and HIV-1 risk, sub-types of HIV-1, and background Ad5 seroprevalence differed.
Vaccination in both studies were stopped, after the first interim efficacy analysis of the Step study crossed pre-determined non-efficacy boundaries. Neither trial demonstrated a decrease in HIV acquisition nor decreased early plasma viral load in vaccinees compared to placebo recipients. Post-hoc analyses of men enrolled in the Step study showed a larger number of HIV infections in the sub-group of vaccinated men who were Ad5 seropositive and uncircumcised compared to a comparable placebo group. This was not demonstrated in the Phambili study, where most men were heterosexual, while most in Step were homosexual/bisexual. Further analysis of the Step study has yet to explain the effect of Ad5 seroprevalence on increased HIV-1 susceptibility in men receiving the vaccine. However, promising vaccine effects on early viral control were seen, and the possibility of effects on early viral load setpoint in women in Phambili was seen.
These trials have provided a number of lessons about the importance of clinical trials in the HIV vaccine discovery process, and insight into the type and level of immune response that will be required for control of viral replication.
Phase IIb test of concept trials; HIV vaccines; ad5 vaccines
We analyzed HIV-1 genome sequences from 68 newly-infected volunteers in the Step HIV-1 vaccine trial. To determine whether the vaccine exerted selective T-cell pressure on breakthrough viruses, we identified potential T-cell epitopes in the founder sequences and compared them to epitopes in the vaccine. We found greater distances for sequences from vaccine recipients than from placebo recipients (p-values ranging from < 0.0001 to 0.09). The most significant signature site distinguishing vaccine from placebo recipients was Gag-84, a site encompassed by several epitopes contained in the vaccine and restricted by HLA alleles common in the cohort. Moreover, the extended divergence was confined to the vaccine components of the virus (Gag, Pol, Nef) and not found in other HIV-1 proteins. These results represent the first evidence of selective pressure from vaccine-induced T-cell responses on HIV-1 infection.
If future HIV vaccine design strategies are to succeed, improved understanding of the mechanisms underlying protection from infection or immune control over HIV replication remains essential. Increased cytotoxic capacity of HIV-specific CD8+ T-cells associated with efficient elimination of HIV-infected CD4+ T-cell targets has been shown to distinguish long-term nonprogressors (LTNP), patients with durable control over HIV replication, from those experiencing progressive disease. Here, measurements of granzyme B target cell activity and HIV-1-infected CD4+ T-cell elimination were applied for the first time to identify antiviral activities in recipients of a replication incompetent adenovirus serotype 5 (Ad5) HIV-1 recombinant vaccine and were compared with HIV-negative individuals and chronically infected patients, including a group of LTNP. We observed readily detectable HIV-specific CD8+ T-cell recall cytotoxic responses in vaccinees at a median of 331 days following the last immunization. The magnitude of these responses was not related to the number of vaccinations, nor did it correlate with the percentages of cytokine-secreting T-cells determined by ICS assays. Although the recall cytotoxic capacity of the CD8+ T-cells of the vaccinee group was significantly less than that of LTNP and overlapped with that of progressors, we observed significantly higher cytotoxic responses in vaccine recipients carrying the HLA class I alleles B*27, B*57 or B*58, which have been associated with immune control over HIV replication in chronic infection. These findings suggest protective HLA class I alleles might lead to better outcomes in both chronic infection and following immunization due to more efficient priming of HIV-specific CD8+ T-cell cytotoxic responses.
Unique HIV-infected individuals have remained healthy with stable CD4 counts and HIV RNA levels below the detection threshold in sensitive assays without antiretroviral therapy for 20 years. These nonprogressors have been intensively studied in order to identify mechanisms that could inform the design of an efficacious HIV/AIDS vaccine. In addition to strong associations with certain host genes like HLA B*57, nonprogressors are distinguished from progressors by the superior ability of their HIV-specific CD8+ T-cells to proliferate and to efficiently kill HIV-infected CD4+ T-cell targets via perforin and granzyme B, the major proteins contained within killing granules. Here, for the first time, we apply sensitive measurements of CD8+ T-cell proliferation and perforin expression, granzyme B target cell activity and infected CD4+ T-cell elimination to samples derived from recipients of the Merck adenovirus serotype 5-HIV vaccine. We demonstrate readily detectable CD8+ T-cell-mediated killing in these vaccinees. Although the killing responses were less than those of nonprogressors, vaccinees expressing the protective HLA alleles B*27, B*57 or B*58 exhibited greater killing than those not possessing these alleles. These findings suggest protective HLA alleles lead to better outcomes in both chronic infection and following immunization through early interactions that induce superior antiviral CD8+ T-cell killing responses.
Successful conduct of HIV vaccine efficacy trials entails identification and enrollment of at-risk populations, assessment of appropriate endpoints as measures of vaccine efficacy for prevention of HIV acquisition and amelioration of disease course among infected vaccinees, as well as identification of potential confounders or effect modifiers. While not invariably useful and bringing their own cost in terms of measurement and validation, a variety of biomarkers may aid at each stage of trial conduct.
A review of selected articles, chosen based on quality, relevance of the biomarker to HIV vaccine trials, and availability of the publication, was conducted. The authors also drew experience from current trials and other planned or ongoing trials.
Biomarkers are available to assess HIV incidence in potential study populations but care is needed in interpreting results of these assays. During trial conduct, STIs such as HSV-2 may act as effect modifiers on primary and secondary endpoints, including HIV incidence and set point viral load. The utility of STI biomarkers will likely depend heavily on local epidemiology at clinical trial sites. Analyses from recent large HIV vaccine efficacy trials point to the complexities in interpreting trial results and underscore the potential utility of biomarkers in evaluating confounding and effect modification.
HIV vaccine trials; HIV incidence; biomarkers; randomized controlled trials; STIs; hepatitis
A peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA).
Low-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, 51Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens.
24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions.
The severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events.
A recent clinical trial of a T-cell-based AIDS vaccine delivered with recombinant adenovirus type 5 (rAd5) vectors showed no efficacy in lowering viral load and was associated with increased risk of human immunodeficiency virus type 1 (HIV-1) infection. Preexisting immunity to Ad5 in humans could therefore affect both immunogenicity and vaccine efficacy. We hypothesized that vaccine-induced immunity is differentially affected, depending on whether subjects were exposed to Ad5 by natural infection or by vaccination. Serum samples from vaccine trial subjects receiving a DNA/rAd5 AIDS vaccine with or without prior immunity to Ad5 were examined for the specificity of their Ad5 neutralizing antibodies and their effect on HIV-1 immune responses. Here, we report that rAd5 neutralizing antibodies were directed to different components of the virion, depending on whether they were elicited by natural infection or vaccination in HIV vaccine trial subjects. Neutralizing antibodies elicited by natural infection were directed largely to the Ad5 fiber, while exposure to rAd5 through vaccination elicited antibodies primarily to capsid proteins other than fiber. Notably, preexisting immunity to Ad5 fiber from natural infection significantly reduced the CD4 and CD8 cell responses to HIV Gag after DNA/rAd5 vaccination. The specificity of Ad5 neutralizing antibodies therefore differs depending on the route of exposure, and natural Ad5 infection compromises Ad5 vaccine-induced immunity to weak immunogens, such as HIV-1 Gag. These results have implications for future AIDS vaccine trials and the design of next-generation gene-based vaccine vectors.
In order to evaluate strategies to reduce HIV transmission through breast milk and optimize both maternal and infant health among HIV-infected women and their infants, we designed and implemented a large, randomized clinical trial in Lilongwe, Malawi. The development of protocols for large, randomized clinical trials is a complicated and lengthy process often requiring alterations to the original research design. Many factors lead to delays and changes, including study site-specific priorities, new scientific information becoming available, the involvement of national and international human subject committees and monitoring boards, and alterations in medical practice and guidance at local, national, and international levels. When planning and implementing a clinical study in a resource-limited setting, additional factors must be taken into account, including local customs and program needs, language and socio-cultural barriers, high background rates of malnutrition and endemic diseases, extreme poverty, lack of personnel, and limited infrastructure. Investigators must be prepared to modify the protocol as necessary in order to ensure participant safety and successful implementation of study procedures. This paper describes the process of designing, implementing, and subsequently modifying the Breastfeeding, Antiretrovirals, and Nutrition, (BAN) study, a large, ongoing, randomized breastfeeding intervention trial of HIV-infected women and their infants conducted at a single site in Lilongwe, Malawi. We highlight some of the successes, challenges, and lessons learned at different stages during the conduct of the trial.
Mother-to-child transmission of HIV; breastfeeding; HIV/AIDS; nutrition; study design and management; antiretroviral drugs
Observational data and non-human primate challenge studies suggest that cell-mediated immune (CMI) responses may provide control of HIV replication. The Step Study is the first direct assessment of the efficacy of a CMI vaccine to protect against HIV infection or alter early plasma HIV levels in humans.
HIV-seronegative participants (3000) were randomized (1:1) to receive 3 injections of MRKAd5 HIV-1 gag/pol/nef vaccine or placebo. Randomization was pre-stratified by gender, baseline adenovirus type 5 (Ad5) titer, and study site. Participants were tested ~every 6 months for HIV acquisition; early plasma HIV RNA was measured ~3 months post-HIV diagnosis.
The vaccine elicited IFN-γ ELISPOT responses in 75% of vaccinees. In a pre-specified interim analysis among participants with baseline Ad5 ≤200, 24 of 741 vaccinees became HIV infected, versus 21 of 762 placebo recipients. All but one infection occurred in men. The early geometric mean plasma HIV RNA was comparable in infected vaccine and placebo recipients. In exploratory multivariate analyses, HIV incidence was higher in vaccinees versus placebo recipients among Ad5 seropositive men (5.1% versus 2.2% per year, respectively) and uncircumcised men (5.2% versus 1.4% per year, respectively). HIV incidence was similar in vaccinees versus placebo recipients among Ad5 seronegative men and circumcised men.
This CMI vaccine did not prevent HIV infection or lower early viral level. Mechanisms for failure of the vaccine to protect and for the increased HIV infection rates in subgroups of vaccinees are being explored. Additional follow-up will determine if elevated HIV incidence in vaccinee subgroups persists.
HIV vaccine; efficacy; adenovirus; HIV acquisition; viral load; male circumcision; test of concept
A successful HIV vaccine would have a substantial impact on acquisition of infection, progression of disease among the infected, or infectiousness of the infected. Current vaccine candidates are anticipated to have their major effect on viremia, however, with the expectation that this would induce or be concordant with a reduced rate of AIDS, death, or infectiousness. Although direct assessment of disease progression or infectiousness may be impractical, available potential surrogates for these endpoints may be misleading. This article summarizes the proceedings of a National Institute of Allergy and Infectious Disease–sponsored workshop to explore the use of surrogate endpoints for licensure of an HIV vaccine. Early, medium, and late endpoints were discussed, along with challenges such as surrogate validity, the confounding effect of antiretroviral therapy initiation, and potential selection bias in the vaccine and placebo recipients who become infected. Results from 5 hypothetic HIV vaccine clinical trials with ambiguously successful results were presented to an expert panel for interpretation and discussion of next steps. Key recommendations included assessing magnitude and durability of surrogate effects, generalization across populations, and directed improvement of vaccines. Use of acquisition and a postinfection surrogate as coprimary endpoints was supported, along with use of composite endpoints and exploration of heterogeneity in vaccine efficacy by characteristics of the host and virus.
Clinical trials; epidemiology; HIV vaccine; surrogate endpoint
Cecilia Morgan and colleagues outline a two-stage nonhuman primate screening strategy for T cell-based HIV-1 vaccines.
Specific morphotypic profiles of normal and abnormal vaginal flora, including bacterial vaginosis (BV), were characterized. A prospective study of 350 women yielded concurrent Gram-stain data and clinical assessment (n = 3455 visits). Microbiological profiles were constructed by Gram stain. Eight profile definitions were based on dichotomizing the levels of Lactobacillus, Gardnerella, and curved, Gram-negative bacillus (Mobiluncus) morphotypes. Of these, two were rare, and the other six demonstrated a graded association with the clinical components of BV. The proposed profiles from the Gram stain reflect the morphotypic categories describing vaginal flora that may enable clearer elucidation of gynecologic and obstetric outcomes in various populations.
Background: Bacterial vaginosis is a common gynecologic infection that has been associated with a variety of
gynecologic and obstetric complications, including pelvic inflammatory disease, postabortal infection and premature
delivery. Recent studies suggest that bacterial vaginosis may increase a woman’s risk for human immunodeficiency
virus (HIV). We undertook this study to assess whether the prevalence and characteristics of bacterial
vaginosis differed according to HIV status in high-risk US women.
Methods: Prevalence of bacterial vaginosis was assessed by Gram’s stain and clinical criteria for 854 HIV-infected
and 434 HIV-uninfected women enrolled in the HIV Epidemiology Research (HER) Study.Multiple logistic regression
techniques were used to determine whether HIV infection independently predicted bacterial vaginosis.
Results: Almost half (46%) the women had bacterial vaginosis by Gram’s stain. The prevalence of bacterial
vaginosis was 47% in the HIV-positive women compared with 44% in the HIV-negativewomen; this difference was
not statistically significant (p = 0.36). After adjustment for other covariates, HIV-positive women were more likely
than HIV-negative women to have bacterial vaginosis (odds ratio (OR) 1.31; 95% confidence interval (CI)
1.01-1.70) by Gram's stain but not by clinical criteria (OR 1.16; CI 0.87-1.55). Among HIV-positive women, use of
antiretroviral drugs was associated with a lower prevalence of bacterial vaginosis (adjusted OR 0.54; Cl
Conclusions: In this cross-sectional analysis of high-risk US women, HIV infection was positively correlated with
bacterial vaginosis diagnosed by Gram’s stain.