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1.  Sequence Analysis of the Dimerization Initiation Site of Concordant and Discordant Viral Variants Superinfecting HIV Type 1 Patients 
AIDS Research and Human Retroviruses  2011;27(11):1231-1235.
For HIV recombination to occur, the RNAs from two infecting strains within a cell must dimerize at the dimerization initiation site (DIS). We examined the sequence identity at the DIS (697–731 bp, Hxb2 numbering engine) in patients superinfected with concordant HIV-1 strains and compared them to those with discordant strains. Viral RNA in sequential plasma from four subjects superinfected with subtype-discordant and two subjects superinfected with subtype-concordant HIV-1 strains was extracted, amplified (5′ LTR-early gag: 526–1200 bp, Hxb2 numbering engine), sequenced, and analyzed to determine their compatibility for dimerization in vivo. The concordant viruses infecting the two subjects exhibited identical sequences in the 35-bp-long DIS region while sequences from the discordant viruses revealed single nucleotide changes that were located in the DIS loop (715 bp), its flanking nucleotides (710 bp and 717 bp), and the DIS stem (719 bp). Evidence from in vitro experiments demonstrates that these in vivo changes identified can abolish dimerization and reduce recombination frequency. Therefore, these results revealing differences in the DIS of discordant strains versus the similarity noted for the concordant strains may contribute to the differences in the frequency of recombination in patients superinfected with such HIV-1 variants.
PMCID: PMC3206772  PMID: 21453132
2.  Retention in an antiretroviral therapy programme during an era of decreasing drug cost in Limbe, Cameroon 
In 2002, Cameroon initiated scale up of antiretroviral therapy (ART); on 1 October 2004, a substantial reduction in ART cost occurred. We assessed the impact of this event and other factors on enrolment and retention in care among HIV-infected patients initiating ART from February 2002 to December 2005 at the single ART clinic serving the Southwest Region in Limbe, Cameroon.
We retrospectively analyzed clinical and pharmacy payment records of HIV-infected patients initiating ART according to national guidelines. We compared two cohorts of patients, enrolled before and after 1 October 2004, to determine if price reduction was associated with enhanced enrolment. We assessed factors associated with retention and survival by Cox proportional hazards models. Retention in care implied patients who had contact with the healthcare system as of 31 December 2005 (including those who were transferred to continue care in other ART centres), although these patients may have interrupted therapy at some time. A patient who was not retained in care may have dropped out (lost to follow up) or died.
Mean enrolment rates for 2920 patients who initiated ART before and after the price reduction were 46.5 and 95.5 persons/month, respectively (p < 0.001). The probabilities of remaining alive and in care were 0.66 (95% CI 0.64-0.68) at six months, 0.58 (95% CI 0.56-0.60) at one year, 0.47 (95% CI 0.45-0.49) at two years and 0.35 (95% CI 0.32-0.38) at three years; they were not significantly different between the two cohorts of patients enrolled before and after the price reduction over the first 15 months of comparable follow up (hazard ratio 1.1; 95% CI 0.9-1.2, p = 0.27). In multivariable analysis using multiple imputations to compensate for missing values, factors associated with dropping out of care or dying were male gender (HR 1.33 [1.18-1.50], p = 0.003), treatment paid by self, family or partly by other (HR 3.05 [1.99-4.67], p < 0.001), and, compared with residents of Limbe, living more than 150 km from Limbe (HR 1.41 [1.18-1.69], p < 0.001), or being residents of Douala (HR 1.51 [1.16-1.98], p < 0.001).
Reducing the cost of ART increased enrolment of clients in the programme, but did not change retention in care. In a system where most clients pay for ART, an accessible clinic location may be more important than the cost of medication for retention in care. Decentralizing ART clinics might improve retention and survival among patients on ART.
PMCID: PMC3143073  PMID: 21679416
3.  Longitudinal Quasispecies Analysis of Viral Variants in HIV Type 1 Dually Infected Individuals Highlights the Importance of Sequence Identity in Viral Recombination 
Little is known regarding the likelihood of recombination between any given pair of nonidentical HIV-1 viruses in vivo. The present study analyzes the HIV-1 quasispecies in the C1C2 region of env, the vif-vpr-vpu accessory gene region, and the reverse transcriptase region of pol. These sequences were amplified from samples obtained sequentially over a 12- to 33-month period from five dually HIV-1-infected subjects. Analysis of an average of 248 clones amplified from each subject revealed no recombinants within the three loci studied of the subtype-discordant infecting strains, whose genetic diversity was >11% in env. In contrast, two subjects who were initially coinfected by two subtype-concordant variants with genetic diversity of 7.4% in env were found to harbor 10 unique recombinants of these strains, as exhibited by analysis of the env gene. The frequent recombination observed among the subtype-concordant strains studied herein correlates with prior sequence analyses that have commonly found higher rates of recombination at loci bearing the most conserved sequences, demonstrating an important role for sequence identity in HIV-1 recombination. Viral load analysis revealed that the samples studied contained an average of 8125 virus copies/ml (range, 882–31,626 copies/ml), signifying that the amount of viral RNA in the samples was not limiting for studying virus diversity. These data reveal that recombination between genetically distant strains may not be an immediate or common outcome to dual infection in vivo and suggest critical roles for viral and host factors such as viral fitness, virus diversity, and host immune responses that may contribute to limiting the frequency of intersubtype recombination during in vivo dual infection.
PMCID: PMC2864053  PMID: 20334562
4.  Infection by Discordant Strains of HIV-1 Markedly Enhances the Neutralizing Antibody Response against Heterologous Virus▿  
Journal of Virology  2010;84(18):9415-9426.
High-risk cohorts in East Africa and the United States show rates of dual HIV-1 infection—the concomitant or sequential infection by two HIV-1 strains—of 50% to 100% of those of primary infection, and our normal-risk HIV-positive cohort in Cameroon exhibits a rate of dual infection of 11% per year, signifying that these infections are not exceptional. Little is known regarding the effect of dual infections on host immunity, despite the fact that they provide unique opportunities to investigate how the immune response is affected when challenged with diverse HIV-1 antigens. Using heterologous primary isolates, we have shown here that dual HIV-1 infection by genetically distant strains correlates with significantly increased potency and breadth of the anti-HIV-1 neutralizing antibody response. When the neutralization capacities of sequential plasma obtained before and after the dual infection of 4 subjects were compared to those of matched plasma obtained from 23 singly infected control subjects, a significant increase in the neutralization capacity of the sequential sample was found for 16/28 dually infected plasma/virus pairs, while only 4/159 such combinations for the control subjects exhibited a significant increase (P < 0.0001). Similarly, there was a significant increase in the plasma dilution capable of neutralizing 50% of virus (IC50) for 18/24 dually infected plasma/virus pairs, while 0/36 controls exhibited such an increase (P < 0.0001). These results demonstrate that dual HIV-1 infection broadens and strengthens the anti-HIV-1 immune response, suggesting that vaccination schemes that include polyvalent, genetically divergent immunogens may generate highly protective immunity against any HIV-1 challenge strain.
PMCID: PMC2937625  PMID: 20631143
5.  HIV-1 Reverse Transcriptase Drug-Resistance Mutations in Chronically Infected Individuals Receiving or Naïve to HAART in Cameroon 
Journal of medical virology  2010;82(2):187-196.
The most common first-line, highly active anti-retroviral therapy (HAART) received by individuals infected with HIV-1 in Cameroon is the combination therapy Triomune, comprised of two nucleoside reverse transcriptase inhibitors (NRTI) and one non-NRTI (NNRTI). To examine the efficacy of these drugs in Cameroon, where diverse non-B HIV-1 subtypes and recombinant viruses predominate, the reverse transcriptase (RT) viral sequences in patient plasma were analyzed for the presence of mutations that confer drug resistance. Forty-nine HIV-1-positive individuals were randomly selected from those receiving care in HIV/AIDS outpatient clinics in the South-West and North-West Regions of Cameroon. Among the 28 patients receiving HAART, 39% (11/28) had resistance to NRTIs, and 46% (13/28) to NNRTIs after a median of 12 months from the start of therapy. Among those with drug-resistance mutations, there was a median of 14 months from the start of HAART, versus 9 months for those without; no difference was observed in the average viral load (10,997 copies/ml vs. 8,056 copies/ml). In contrast, drug-naïve individuals had a significantly higher average viral load (27,929 copies/ml) than those receiving HAART (9,527 copies/ml). Strikingly, among the 21 drug-naïve individuals, 24% harbored viruses with drug-resistance mutations, suggesting that HIV-1 drug-resistant variants are being transmitted in Cameroon. Given the high frequency of resistance mutations among those on first-line HAART, coupled with the high prevalence of HIV-1 variants with drug-resistance mutations among drug-naïve individuals, this study emphasizes the need for extensive monitoring of resistance mutations and the introduction of a second-line HAART strategy in Cameroon.
PMCID: PMC2958705  PMID: 20029816
drug-resistance mutations; HIV-1; NRTI; NNRTI; HAART; drug naïve

Results 1-5 (5)