Search

Current serological assays that are used for cross-sectional HIV incidence estimation have been shown to misclassify individuals with chronic infection. Limited information exists on the performance of cross-sectional incidence assays in Central Africa. HIV-positive individuals from Cameroon who were infected for at least 1 or 2 years were evaluated to determine the false recent ratio (FRR) of a two-assay algorithm, which includes the Limiting Antigen Avidity (LAg-Avidity) assay (normalized optical density units, ODn 1000 copies/ml). The subject-level FRR was 5.3% (95% confidence interval [CI], 2.1–10.5) for individuals infected for ≥1 year and 3.9% (95% CI, 0.8–11.0) for individuals infected for ≥2 years. These data suggest that the LAg-Avidity plus viral load incidence algorithm may overestimate HIV incidence rates in Central Africa.

HIV superinfection describes the sequential infection of an individual with two or more unrelated HIV strains. Intersubtype superinfection has been shown to cause a broader and more potent heterologous neutralizing antibody response when compared to singly infected controls, yet the effects of intrasubtype superinfection remain controversial. Longitudinal samples were analyzed phylogenetically for pol and env regions using Next-Generation Sequencing and envelope cloning. The impact of CRF02_AG intrasubtype superinfection was assessed for heterologous neutralization and antibody binding responses. We compared two cases of CRF02_AG intrasubtype superinfection that revealed complete replacement of the initial virus by superinfecting CRF02_AG variants with signs of recombination. NYU6564, who became superinfected at an early time point, exhibited greater changes in antibody binding profiles and generated a more potent neutralizing antibody response post-superinfection compared to NYU6501. In contrast, superinfection occurred at a later time point in NYU6501 with strains harboring significantly longer V1V2 regions with no observable changes in neutralization patterns. Here we show that CRF02_AG intrasubtype superinfection can induce a cross-subtype neutralizing antibody response, and our data suggest timing and/or superinfecting viral envelope characteristics as contributing factors. These results highlight differential outcomes in intrasubtype superinfection and provide the first insight into cases with CRF02_AG, the fourth most prevalent HIV-1 strain worldwide.

Near full genome sequencing (NFGS) of HIV-1 is required to assess the genetic composition of HIV-1 strains comprehensively. Population-wide, it enables a determination of the heterogeneity of HIV-1 and the emergence of novel/recombinant strains, while for each individual it constitutes a diagnostic instrument to assist targeted therapeutic measures against viral components. There is still a lack of robust and adaptable techniques for efficient NFGS from miscellaneous HIV-1 subtypes. Using rational primer design, a broad primer set was developed for the amplification and sequencing of diverse HIV-1 group M variants from plasma. Using pure subtypes as well as diverse, unique recombinant forms (URF), variable amplicon approaches were developed for NFGS comprising all functional genes. Twenty-three different genomes composed of subtypes A (A1), B, F (F2), G, CRF01_AE, CRF02_AG, and CRF22_01A1 were successfully determined. The NFGS approach was robust irrespective of viral loads (&ge, 306 copies/mL) and amplification method. Third-generation sequencing (TGS), single genome amplification (SGA), cloning, and bulk sequencing yielded similar outcomes concerning subtype composition and recombinant breakpoint patterns. The introduction of a simple and versatile near full genome amplification, sequencing, and cloning method enables broad application in phylogenetic studies of diverse HIV-1 subtypes and can contribute to personalized HIV therapy and diagnosis.

Cameroon is a West African country where high genetic diversity of HIV-1 has been reported. The predominant CRF02_AG is involved in the emergence of more complex intersubtype recombinants. In this study, we sequenced the full-length genome of a novel unique recombinant form (URF) of HIV-1, 02CAMLT04 isolated in blood donors in urban Cameroon. Phylogenetic tree and bootscan analysis showed that 02CAMLT04 was complex and appeared to be a secondary recombinant derived from CRF02_AG and CRF22_01A1. The genomic composition of 02CAMLT04 strain showed that it is composed of three segments; twenty four percent of the genome is classified as CRF02_AG, spanning most of the envelope gene. The remaining seventy six percent of the genome is classified as CRF22_01A1. In addition, the sequence analysis of 13 full-length sequences from HIV-1 positive specimens received from Cameroon between 2002 and 2010 indicated that five specimens are pure CRF22_01A1 viruses, and six others have homology with CRF22_01A1 sequences in either gag, pol or env region where as 6% of strains contain portions of CRF22_01A1. Further study demonstrated that CRF22_01A1 is a primary prevalence strain co-circulating in Cameroon and is involved in complex intersubtype recombination events with subtypes (D or F), subsubtypes (A1 or F2) and CRFs (CRF01_AE or CRF02_AG). Our studies show that novel recombinants between CRF22_01A1 and other clades and recombinant forms may be emerging in Cameroon that could contribute to the future global diversity of HIV-1 in this region and world wide.

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.

Objectives To determine the frequency of dual inter- and intra-subtype HIV-1 infection among a cohort of 64 longitudinally-studied, HIV-1-positive individuals in Yaounde, Cameroon. Methods Blood was collected every 3-6 months for up to 36 months and RNA was extracted from plasma. Gag fragment (HxB2 location 1577-2040) was amplified by nested RT-PCR, and mixed-time-point Heteroduplex Assays (HDAs) were performed. As heteroduplexes in this assay indicate >or=5% genetic discordance in the gag fragment, their presence reveals dual infection. Results were confirmed by phylogenetic analysis. Results Heteroduplexes were generated by specimens of 10 subjects (15.6%). Kaplan-Meier nonparametric estimate of maintenance of single infection was calculated; the rate/year of a 2 infection was found to be approximately 11%. Dual infection was identified in the final specimens of five subjects, after as much as 18 months follow-up, while for the remaining five subjects, dual infection was identified in interim specimens within an average of 10 months follow-up. Analysis of samples obtained after dual infection from each of these latter five subjects revealed two patterns: reversion to initial strain, or replacement of initial strain. Four subjects were dually-infected with HIV-1 strains of the same subtype, while 6 were infected with different subtypes. Conclusions The high prevalence of recombinant HIV-1 strains in Cameroon may in part be explained by the high frequency of dual infection. In this genetically-diverse HIV-1 milieu, dual infections and the recombinant viruses they generate are strongly driving viral evolution, complicating vaccine strategies.

Broad HIV-1 genetic diversity in Cameroon provides a unique opportunity to monitor HIV-1 evolution and allows the detection of novel strains. We have genetically characterized the HIV-1 subtypes found in 156 samples from 90 drug-naive subjects in Yaounde, Cameroon collected from 2011 to 2013, using phylogenetic analysis of regions in gag and pol. We identified subtypes CRF02_AG (64.9%), CRF22_01A1 (7.1%), D (4.5%), F2 (3.9%), G (3.2%), CRF18_cpx (3.2%), CRF37_cpx (3.2%), CRF11_cpx (2.6%), CRF13_cpx (1.9%), A1 (1.3%), CRF01_AE (1.3%), CRF09_cpx (1.3%), A2 (0.6%), and H (0.6%). Sequence data for both the gag and pol regions were obtained from 62 subjects; for 59 of these subjects the two regions were identified as the same viral subtype while three subjects were discordant, A1/CRF02_AG (subject MDC006), CRF02_AG/F2 (subject MDC179), and a dual infection with CRF02_AG/F2 (subject MDC131). Longitudinal sequence data were obtained for 28 of these 62 subjects and confirmed the cross-sectional results. These data update subtype information for this area and highlight the necessity of such studies due to the numerous circulating subtypes, the ongoing superinfection, and the risk of emerging novel recombinant viruses.

Limited information is available on the prevalence among rural Africans of host genetic polymorphisms conferring resistance to HIV-1 infection or slowing HIV disease progression. We report the allelic frequencies of the AIDS-related polymorphisms CCR2-64I, SDF1-3'A, and CCR5-Delta32 in 321 volunteers from 7 ethnic groups in Cameroon. Allelic frequencies differed among the 7 ethnic groups, ranging from 10.8% to 31.3% for CCR2-64I and 0.0% to 7.1% for SDF1-3'A. No CCR5-Delta32 alleles were found. HIV seroprevalence was 6.9% in the total population and peaked at younger ages in girls and women than in boys and men. Among 15- to 54-year-olds, HIV seroprevalence varied from 2.0% to 11.1% among the village populations. Conditional logistic regression analysis using data from boys and men aged 15 to 54 years showed the number of CCR2-64I alleles to be a significant risk factor for HIV seropositivity (odds ratio per allele adjusted for age and matched on ethnic group = 6.3, 95% confidence interval: 1.3-30.3); this association was not found in women. The findings are consistent with the hypothesis that CCR2-64I alleles may delay HIV disease progression without affecting susceptibility to infection among men. We did not observe this relation among women, and other factors, such as multiple pregnancies or maternal stressors (eg, breastfeeding), may have masked any protective effect of CCR2-64I alleles. Further study of this issue among women is warranted. SDF1-3'A did not differ between HIV-seropositive and HIV-seronegative individuals but was associated with increasing age among HIV-seronegative women, suggesting a protective effect against HIV-1 infection.

Both polyclonal and monoclonal human antibodies (Abs) to the V3 domain of HIV-1 gp120 display cross-clade neutralizing activity against primary isolates and T cell-adapted virus strains. The most broadly neutralizing of the human anti-V3 monoclonal Abs (mAbs), 447-52D, recognizes 14 amino acids, including the GPxR core epitope at the tip of the V3 loop. Monoclonal Ab 447-52D neutralized 92% of 38 primary isolates carrying the GPGR V3 motif regardless of whether the viruses belonged to clades A, B, F, or H; in contrast, none of 19 viruses with the GPGQ and other non-GPGR/Q sequences at the tip of the V3 loop was sensitive to mAb 447-52D. These data are consistent with the crystallographic resolution of a complex of the Fab fragment of mAb 447-52D with a V3 peptide that shows that the binding specificity of the mAb is due to recognition of the GPGR motif at the tip of the loop. The critical role of the Arg residue in this motif was determined using viruses pseudotyped with the envelope of primary isolate CA1 containing the GPGR motif or with a mutated envelope with a Gln (Q) replacing the Arg (R) at the tip of the loop. While the wild-type pseudovirus was neutralized by mAb 447-52D, the pseudovirus carrying the point mutation was resistant to neutralization. These data illuminate the structural basis for both the breadth and specificity of a broadly neutralizing human mAb and contribute to our understanding of the epitopes recognized by Abs that protect against infection with HIV-1.

Objective: To document infection with HIV type 1 (HIV-1) group M non-B subtypes in individuals living in New York City. Design: From October 1999 through April 2003, HIV-1-seropositive individuals were selected from 3 clinics in New York City based on having risk factors for infection with HIV-1 non-B subtypes. Methods: HIV-1 RNA was extracted from plasma samples, and partial gag, pol, or env genes were amplified by PCR analysis. The infecting HIV- 1 group M subtype was determined based on results of either heteroduplex mobility assay or sequencing and phylogenetic analysis. Results: Ninety-seven subjects were enrolled in the study. Of the 97 subjects, 91 (94%) were selected based on having emigrated from a non-European country, while 6 (6%) were native United States citizens. Subtypes were successfully determined in 53 (55%) of the 97 plasma samples tested. The subtypes in 2 plasma samples were unclassifiable. HIV-1 infections were classified as those due to the following group M subtypes: A (n = 4; 7%), B (n = 12; 22%), C (n = 8; 15%), F (n = 2; 4%), CRF01―AE-like (n = 7; 13%), CRF02―AG-like (n = 19; 34%), an intersubtype recombinant form G gag /A env (n = 1; 2%), and unclassifiable viruses (n = 2; 4%). Conclusion: This study reveals infection with a broad variety of HIV-1 group M subtypes mostly in the immigrant population of New York City as well as how several non-B subtypes are being introduced into the United States.

Objective: To investigate the genetic diversity of the HIV-1 circulating in Shanghai and to analyze the mutations in the protease (PR) gene associated with resistance to protease inhibitors (PIs). Design: The genetic diversity of HIV-1 and PI resistance–associated mutations was studied in 40 Shanghai HIV-1-seropositive treatment-naive residents. The patients studied were exposed to the infection mainly through contaminated blood products (hemophiliacs) (n = 17) and sexual contacts (n = 19). Samples from 2 injecting drug users (IDUs) and 2 children born to HIV-1 infected mothers were also analyzed. Methods: HIV-1 partial gag pol and env genes in infected plasma samples were amplified by reverse transcriptase polymerase chain reaction sequenced and phylogenetically analyzed. Analysis of PI resistance –associated amino acid substitution in PR was performed. Results: HIV-1 genes in 38 of the 40 plasma samples were successfully amplified and analyzed. Polymerase chain reaction amplification was successful for 16/17 hemophilia patients and 18/19 sexually infected individuals. While all the 16 hemophilia patients infected through contaminated blood products were infected with subtype B’ the 18 patients infected through sexual contact were infected with several subtypes including subtype A (n = 2) B (n = 4) B’ (n = 1) C (n = 2) CRF08_BC (n = 1) CRF01_AE (n = 7) and intersubtype recombinant CRF01_AE/B (n = 1). The 2 IDUs were infected with CRF08_BC and the 2 children born to HIV-1 infected mothers were infected with subtype B’ and CRF01_AE. PI resistance–associated amino acid substitutions were found at 1 codon in primary and 7 codons in secondary regions of the PR gene. Amino acid substitutions were more frequently found in the B/B’ sequences (69%) than in the non-B sequences (31%). Substitutions characteristic with the subtype B/B’ sequences mainly among hemophiliacs included L63P (87%) A71V/T (27%) and V77I (93%) while those that characterized the non-B sequences mainly found among heterosexuals included M36I (69%) and K20R (19%). Conclusion: This study reveals the presence of multiple HIV-1 subtypes and recombinants infecting Shanghai residents. The broad HIV-1 diversity is being introduced into this city through heterosexual contacts. This study also reveals that viruses infecting these treatment- naive patients have acquired both primary or secondary mutations in their PR genes. These studies should provide the basis for further epidemiologic surveys of HIV-1 subtypes and set strategies for treatment intervention and vaccine programs. (authors)

Background: The use of CCR5 antagonists involves determination of HIV-1 tropism prior to initiation of treatment. HIV-1 tropism can be assessed either by phenotypic or genotypic methods. Genotypic methods are extensively used for tropism prediction. However, their validation in predicting tropism of viral isolates belonging to group M non-B subtypes remains challenging. In Cameroon, the genetic diversity of HIV-1 strains is the broadest reported worldwide. To facilitate the integration of CCR5 antagonists into clinical practice in this region, there is a need to evaluate the performance of genotypic methods for predicting tropism of highly diverse group M HIV-1 strains. Methods: Tropism of diverse HIV-1 strains isolated from PBMCs from Cameroon was determined using the GHOST cell assay. Prediction, based on V3 sequences from matched plasma samples, was determined using bioinformatics algorithms and rules based on position 11/25 and net charge applied independently or combined according to Delobel’s and Garrido’s rules. Performance of genotypic methods was evaluated by comparing prediction generated with tropism assigned by the phenotypic assay. Results: Specificity for predicting R5-tropic virus was high, ranging from 83.7% to 97.7% depending on the genotypic methods used. Sensitivity for X4-tropic viruses was fairly low, ranging from 33.3% to 50%. In our study, overall, genotypic methods were less able to accurately predict X4-tropic virus belonging to subtype CRF02_AG. In addition, it was found that of the methods we used the Garrido rule has the highest sensitivity rate of over 50% with a specificity of 93%. Conclusion: Our study demonstrated that overall, genotypic methods were less sensitive for accurate prediction of HIV-1 tropism in settings where diverse HIV-1 strains co-circulate. Our data suggest that further optimization of genotypic methods is needed and that larger studies to determine their utility for tropism prediction of diverse HIV-1 strains may be warranted.

To be successful with strategies involving passive immunization or the generation of neutralizing antibodies against HIV, it is crucial that we improve our understanding of the process of antibody-mediated HIV neutralization. We have used a neutralization assay based on polymerase chain reaction (PCR) that is more rapid and sensitive than the conventional p24 neutralization assay based on enzyme-linked immunosorbent assay (ELISA). PCR assays permit measurement of the number of infectious events and can detect small amounts of HIV-1 only a few days postinfection. In these studies, the human anti-V3 monoclonal antibody 694/98-D was used to neutralize the infectivity of the laboratory isolate HIVIIIB for CEM-SS cells. 8E5/LAV cells, which contain a single integrated copy of proviral DNA per cell, served as a standard to determine the amount of HIV-1 copies in infected CEM-SS cells. Evaluation of antibody-mediated neutralization was possible at 2 to 3 days postinfection, at a time when p24 readouts were not conclusive. We achieved >95% neutralization of HIVIIIB, and of its molecular clone HXB2, using the monoclonal antibody 694/98-D. This degree of neutralization is probably highly significant in vivo. Nevertheless, a small amount of both HIVIIIB and HXB2 ( approximately 5%) escapes neutralization and can consistently be detected after a few days by this sensitive assay. Experiments with different anti-HIV monoclonal antibodies and viruses showed that the assay could be applied to anti-V3 as well as anti-CD4 binding domain antibodies as well as HIV laboratory strains or primary isolates.

A previous study on cross-clade neutralization activity, identified three key isolates, MNlab (envB/gagB; X4 coreceptor), VI525 (envG/gagH, envA/gagA; R5X4) and CA9 (Group O; R5), that allowed discrimination of sera, likely or unlikely to neutralize primary HIV-1 isolates belonging to Group M (env clades A–H) and Group O. The prognostic ability of these three isolates was verified by means of an external validation on a different and larger set of sera. A total of 79 different sera (66 HIV-1, 10 HIV-2, 1 HIV-1+2 and 2 SIVcpz) were examined first for their capacity to neutralize the three key isolates, next sera were challenged against 12 other primary HIV-1 isolates of Group M (env A–H) and 2 isolates of Group O. Sera that neutralized all three isolates with an ID50 titer of ≥1/40, also neutralized the 14 other primary isolates belonging to different genetic groups and clades. Sera that did not neutralize all three isolates did not exert broad cross-neutralizing activity. The neutralizing activity was antibody-mediated because it was absorbed and eluted from a Prot-G column. Competition-neutralization experiments using recombinant gp120 (HIV-1 MNlab) reduced the neutralizing capacity, suggesting that the neutralizing antibodies were directed against the Env protein. Remarkably, the broad cross-neutralization activity was found primarily in African female patients. In conclusion, this study confirms that three isolates are sufficient to allow identification of broad cross-neutralizing sera. J. Med. Virol. 61:14–24, 2000. © 2000 Wiley-Liss, Inc.

The HIV epidemic in Cameroon is marked by a broad genetic diversity dominated by circulating recombinant forms (CRFs). Studies performed more than a decade ago in urban settings of Southern Cameroon revealed a dominance of the CRF02_AG and clade A variants in >90% of the infected subjects; however, little is known about the evolving viral variants circulating in this region. To document circulating HIV viral diversity, four regions of the viral genome (gag, PR, reverse transcriptase, env) in 116 HIV-1 positive individuals in Limbe, Southern Cameroon, were PCR-amplified. Sequences obtained at the RT and protease regions were analyzed for mutations that conferred drug resistance using the Stanford Drug Resistance Database. The present study reveals a broad genetic diversity characterized by several unique recombinant forms (URF) accounting for 36% of infections, 48.6% of patients infected with CRF02_AG, and the emergence of CRF22_01A1 in 7.2% of patients. Three out of 15 (20%) treated patients and 13 out of 93 (13.9%) drug naive patients harbor drug resistance mutations to RT inhibitors, while 3.2% of drug naive patients harbor drug resistance mutations associated with protease inhibitors. The high proportion (13.9%) of drug resistance mutations among the drug naive patients reveals the ongoing transmission of these viruses in this region of Cameroon and highlights the need for drug resistance testing before starting treatment for patients infected with HIV-1. J. Med. Virol. 86:385–393, 2014. © 2013 The Authors. Journal of Medical Virology Published by Wiley Periodicals, Inc.

The global scale-up of antiretroviral (ARV) therapy has dramatically reduced human immunodeficiency virus (HIV) morbidity and mortality. Stavudine (d4T) has been among the most commonly used ARVs in resource-limited settings because of its efficacy, short-term tolerability, low cost, and availability in coformulated form. However, many countries are transitioning away from d4T, mainly because of mitochondrial toxicities associated with long-term d4T use. In 2010, the World Health Organization (WHO) recommended phasing out d4T even in patients without documented virological failure [1]. There are two distinct mutational pathways of d4T resistance with different implications for zidovudine (AZT) and tenofovir (TDF) cross-resistance, the primary candidates for replacing d4T [2–4]. However, genotypic resistance testing is usually not available in the resource-limited settings where d4T-containing regimens are most commonly used. It is therefore important to determine the extent of nucleoside reverse-transcriptase inhibitor (NRTI) cross-resistance in viruses from individuals with virological failure on d4T-containing first-line therapy undergoing genotypic resistance testing. In this study, we combined genetic sequence data from 35 different studies to characterize the patterns of NRTI resistance mutations in viruses from individuals with virological failure on the 2 widely used d4T-containing ARV regimens: d4T/lamivudine(3TC)/nevirapine(NVP) and d4T/3TC/efavirenz(EFV). We also examine the effects of HIV-1 subtype, duration of therapy, and concomitant nonnucleoside reverse-transcriptase inhibitor (NNRTI) on the selection of specific mutations. We focused our analysis on NRTI resistance mutations with differential effects on the residual activity of AZT compared with TDF. The implications of these data for optimal replacement of d4T and subsequent NRTI options are discussed.

Background Cameroon is a country in West Central Africa with a population of about 20 million inhabitants, with an estimated HIV prevalence of 5.1% in the general population. The HIV epidemic in this region is marked by a broad genetic diversity dominated by Circulating Recombinant Forms (CRFs). Methods To characterize HIV-1 genotypes circulating in HIV positive individuals in Limbe, Cameroon, we phylogenetically analyzed blood samples from 116 HIV positive patients. Of 116 samples tested, 110 were amplified by nested PCR at the Gag, Pol and Env genes. Sequences obtained were phylogenetically analyzed with reference sequences from the Los Alamos database. The RT region of samples was also amplified to identify mutations that conferred resistance to Reverse Transcriptase inhibitors (RTIs) using the Stanford University Drug resistance database. Results

Background Recent studies have demonstrated that both the potency and breadth of the humoral anti-HIV-1 immune response in generating neutralizing antibodies (nAbs) against heterologous viruses are significantly enhanced after superinfection by discordant HIV-1 subtypes, suggesting that repeated exposure of the immune system to highly diverse HIV-1 antigens can significantly improve anti-HIV-1 immunity. We investigated whether sequential plasma from subjects superinfected with discordant HIV-1 subtypes, who exhibit broad nAbs against heterologous viruses, also neutralize either or both of their discordant early autologous viruses with increasing potency.

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.

Preferential usage of immunoglobulin (Ig) genes that encode antibodies (Abs) against various pathogens is rarely observed and the nature of their dominance is unclear in the context of stochastic recombination of Ig genes. The hypothesis that restricted usage of Ig genes predetermines the antibody specificity was tested in this study of 18 human anti-V3 monoclonal Abs (mAbs) generated from unrelated individuals infected with various subtypes of HIV-1, all of which preferentially used pairing of the VH5-51 and VL lambda genes. Crystallographic analysis of five VH5-51/VL lambda-encoded Fabs complexed with various V3 peptides revealed a common three dimensional (3D) shape of the antigen-binding sites primarily determined by the four complementarity determining regions (CDR) for the heavy (H) and light (L) chains: specifically, the H1, H2, L1 and L2 domains. The CDR H3 domain did not contribute to the shape of the binding pocket, as it had different lengths, sequences and conformations for each mAb. The same shape of the binding site was further confirmed by the identical backbone conformation exhibited by V3 peptides in complex with Fabs which fully adapted to the binding pocket and the same key contact residues, mainly germline-encoded in the heavy and light chains of five Fabs. Finally, the VH5-51 anti-V3 mAbs recognized an epitope with an identical 3D structure which is mimicked by a single mimotope recognized by the majority of VH5-51-derived mAbs but not by other V3 mAbs. These data suggest that the identification of preferentially used Ig genes by neutralizing mAbs may define conserved epitopes in the diverse virus envelopes. This will be useful information for designing vaccine immunogen inducing cross-neutralizing Abs.

Background The HIV epidemic in Cameroon is characterized by a high degree of viral genetic diversity with circulating recombinant forms (CRFs) being predominant. The goal of our study was to determine recent trends in virus evolution and emergence of drug resistance in blood donors and HIV positive patients. Methodology Blood specimens of 73 individuals were collected from three cities and a few villages in Cameroon and viruses were isolated by co-cultivation with PBMCs. Nested PCR was performed for gag p17 (670 bp) pol (840 bp) and Env gp41 (461 bp) genes. Sequences were phylogenetically analyzed using a reference set of sequences from the Los Alamos database. Results Phylogenetic analysis based on partial sequences revealed that 65% (n = 48) of strains were CRF02_AG, 4% (n = 3) subtype F2, 1% each belonged to CRF06 (n = 1), CRF11 (n = 1), subtype G (n = 1), subtype D (n = 1), CRF22_01A1 (n = 1), and 26% (n = 18) were Unique Recombinant Forms (URFs). Most URFs contained CRF02_AG in one or two HIV gene fragments analyzed. Furthermore, pol sequences of 61 viruses revealed drug resistance in 55.5% of patients on therapy and 44% of drug naïve individuals in the RT and protease regions. Overall URFs that had a primary HIV subtype designation in the pol region showed higher HIV-1 p24 levels than other recombinant forms in cell culture based replication kinetics studies. Conclusions Our results indicate that although CRF02_AG continues to be the predominant strain in Cameroon, phylogenetically the HIV epidemic is continuing to evolve as multiple recombinants of CRF02_AG and URFs were identified in the individuals studied. CRF02_AG recombinants that contained the pol region of a primary subtype showed higher replicative advantage than other variants. Identification of drug resistant strains in drug-naïve patients suggests that these viruses are being transmitted in the population studied. Our findings support the need for continued molecular surveillance in this region of West Central Africa and investigating impact of variants on diagnostics, viral load and drug resistance assays on an ongoing basis.

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.

Background Antibodies induced by a vaccine that will protect against infection by HIV-1 will be heterologous, yet, little is known on how virus evolution affects neutralization sensitivity to heterologous antibodies. Therefore, experiments were performed to test the sensitivity of sequential HIV-1 primary isolates to anti-HIV-1 monoclonal antibodies (mAbs) and to analyze changes in the neutralization epitopes.

To design a vaccine that will remain potent against HIV-1, the immunogenic regions in the viral envelope that tend to change as well as those that remain constant over time must be identified. To determine the neutralization profiles of sequential viruses over time and study whether neutralization patterns correlate with sequence evolution, 12 broadly neutralizing plasmas from HIV-1 subtype B-infected individuals were tested for their ability to neutralize sequential primary HIV-1 subtype B viruses from four individuals. Three patterns of neutralization were observed, including a loss of neutralization sensitivity by viruses over time, an increase in neutralization sensitivity by sequential viruses, or a similarity in the sensitivity of sequential viruses to neutralization. Seven to 11 gp160 clones from each sequential virus sample were sequenced and analyzed to identify mutational patterns. Analysis of the envelope sequences of the sequential viruses revealed changes characteristic of the neutralization patterns. Viruses that evolved to become resistant to neutralizing antibodies also evolved with diverse sequences, with most of the changes being due to nonsynonymous mutations occurring in the V1/V2, as well as in the constant regions (C2, C3, C4), the most changes occurring in the C3. Viruses from the patient that evolved to become more sensitive to neutralization exhibited less sequence diversity with fewer nonsynonymous changes that occurred mainly in the V1/V2 region. The V3 region remained constant over time for all the viruses tested. This study demonstrates that as viruses evolve in their host, they either become sensitive or resistant to neutralization by antibodies in heterologous plasma and mutations in different envelope regions account for these changes in their neutralization profiles.

The predominance of unique recombinant forms (URFs) of HIV-1 in Cameroon suggests that dual infection, the concomitant or sequential infection with genetically distinct HIV-1 strains, occurs frequently in this region; yet, identifying dual infection among large HIV cohorts in local, resource-limited settings is uncommon, since this generally relies on labor-intensive and costly sequencing methods. Consequently, there is a need to develop an effective, cost-efficient method appropriate to the developing world to identify these infections. In the present study, the heteroduplex assay (HDA) was used to verify dual or single infection status, as shown by traditional sequence analysis, for 15 longitudinally sampled study subjects from Cameroon. Heteroduplex formation, indicative of a dual infection, was identified for all five study subjects shown by sequence analysis to be dually infected. Conversely, heteroduplex formation was not detectable for all 10 HDA reactions of the singly infected study subjects. These results suggest that the HDA is a simple yet powerful and inexpensive tool for the detection of both intersubtype and intrasubtype dual infections, and that the HDA harbors significant potential for reliable, high-throughput screening for dual infection. As these infections and the recombinants they generate facilitate leaps in HIV-1 evolution, and may present major challenges for treatment and vaccine design, this assay will be critical for monitoring the continuing pandemic in regions of the world where HIV-1 viral diversity is broad.

An array of CRFs have been identified in Cameroon, the most notable being CRF02_AG. HIV-1 in the East Province of Cameroon is particularly diverse: in a recent study, we found a high proportion of unique recombinant forms (URFs). Herein we describe the analysis of the full-length sequences of two of these URFs, which, after preliminary analysis of gag, pol, and env fragments, appeared to be a novel CRF. This novel strain, CRF36_cpx, contains fragments that can be assigned to the CRF01_AE, CRF02_AG, and subtype A and G radiations. Forty percent of the genome can be classified as CRF02_AG, including regions in gag, pol, env, and the accessory genes. Twenty-seven percent is CRF01_AE, comprising the majority of gag, the beginning of env, and the end of env into the 3' LTR. Twenty percent of the genome can be assigned to subtype A, with segments in pol and env. The remaining 13% of the sequence is classifiable as subtype G, in pol and vpu. The subtype A and G lineages formed by the CRF36_cpx sequences are unique and appear ancestral in nature. CRF36_cpx is both the first to combine more than one CRF and the first to include fragments of CRF02_AG. The ancestral sequences present in CRF36_cpx represent a link to extinct strains, and, potentially, insight into the evolution of HIV-1.

HIV-1 in Cameroon is genetically diverse, but is predominated by the circulating recombinant form (CRF) 02_AG, which cocirculates among an array of other CRFs, unique recombinant forms (URFs), and all group M subtypes. In particular, our studies of HIV-1 diversity in the East Province found a high proportion of URFs and second generation recombinants (SGRs), suggesting this region of Cameroon may be a breading ground for new CRFs. Herein we present the full-length sequence analysis of one such CRF, composed primarily (66%) of unique, distant lineages of subtypes A and G in alternating regions throughout the genome. This CRF also combines segments in pol and env genes possessing intrasubtype distance (

HIV-1 circulating recombinant form (CRF) 02_AG is responsible for greater than 65% of HIV-1 infections in Cameroon and is widespread across West and West-Central Africa. The parental subtypes A1 and G cocirculate in this part of Africa, and high rates of infection predispose to the generation of AG unique recombinant forms (URFs). Little is known as to whether A1 and G can recombine and thrive in vivo with breakpoints other than those characteristic of CRF02_AG. In this study, six unique recombinant viruses of subtypes A1 and G were identified in two individuals in Cameroon. A 1.5 kb fragment of the reverse transcriptase (RT) region of pol (HXB2 location 2,612–4,159) and the entire env gene (HXB2 location 6,202–9,096) were evaluated by phylogenetic and breakpoint analyses. Each URF was found to have breakpoints different than CRF02_AG, indicating that A and G gene segments are functionally compatible with more than one pattern of recombination. Furthermore, contemporaneous, cultured viruses from these individuals were analyzed, revealing different proportions of URFs compared to those found in plasma, possibly indicating compart mentalization and/or phenotypic variation among the URFs. CRF02_AG emerged from West-Central Africa to become a highly successful viral strain. As such, monitoring the spread of newly emerging AG recombinants is critical not only for understanding the epidemiology of HIV-1, but also in the design of future therapeutics and vaccines appropriate to this part of Africa, and globally. J. Med. Virol. 79:1270–1285, 2007. © Wiley-Liss, Inc.

Human immunodeficiency virus type 1 (HIV-1) circulating recombinant form (CRF) 02_AG is the predominant subtype in Cameroon, even more prevalent than the parental subtypes A and G. An important question that needs to be addressed is whether recombination in HIV-1 infection can lead to the emergence of viruses with biological advantages. The replicative capacity was investigated in peripheral blood mononuclear cells (PBMCs) of 13 R5-tropic primary HIV-1 isolates, including 5 CRF02_AG, 4 subtype A, and 4 subtype G viruses. HIV-1 subtype identity was defined by phylogeny either of the full-length genome or analysis of a combination of segments of the gag, pro, pol, and env genes followed by recombination breakpoint analysis. All viruses were grown on PBMCs for 11 days and culture supernatant was analyzed for reverse transcriptase (RT) activity and p24 production. On day 11 post-infection, CRF02_AG strains had a 1.4-1.9 times higher RT activity and reached a significantly higher level of p24 production than the parental subtypes A and G. Furthermore, the replication rate as measured by p24 production was 1.4 times higher for CRF02_AG strains compared to the subtypes A and G. This study suggests that the recombination event that led to CRF02_AG resulted in a variant with a better replicative capacity than its progenitors. This adaptation could contribute to the broader spread of HIV-1 CRF02_AG leading to its predominance in West Central Africa compared to the lower prevalence of its parental subtypes A and G.

This study describes the HIV-1 genetic diversity that currently circulates in Bamenda, the provincial capital of the North West province of Cameroon. Phylogenetic analysis of the protease (pro) gene of 20 HIV-1-seropositive individuals identified 11 (55%) CRF02_AG, one D, one F2, one J, and four (20%) unclassifiable strains. Interestingly, the remaining two (10%) samples, 02CMNYU3072 and 03CMNYU3224, originating from epidemiologically unlinked individuals, were classified as CRF09_cpx, representing the first reported cases of this complex circulating recombinant form (CRF) in Cameroon. Additional analysis of the C2V5 portion of the envelope (env) gene confirmed the CRF09_cpx identity of these isolates and classified the remaining isolates as CRF02_AG (n = 12, 63%), subtype D (n = 2, 11%), subtype F2 (n = 2, 11%), and subtype A1 (n = 1). In combination, the pro and env subtyping results revealed three (16%) isolates with discordant subtypes including J( pro )CRF02_AG( env ), CRF02_AG( pro )D( env ), and CRF02_AG( pro )F2( env ). In conclusion, this study highlights the presence of HIV-1 CRF09_cpx in Cameroon and identifies three possible intersubtype recombinants (ISRs) containing CRF02_AG in a town where CRF02_AG infections predominate, and stresses the commonness of HIV-1 recombinant strains in a region where broad genetic diversity exists.

We describe the resistance-associated substitutions that are present in the reverse transcriptase (RT) genes of HIV-1 CRF02_AG strains infecting drug-naive villagers of Cameroon. The 11 sequences analyzed were previously subtyped as CRF02_AG in the gag, pro, and env genes, and this work revealed that most (10/11) had a concordant subtype (CRF02_AG) in the pol gene, while one sequence had discordant subtype (A1) in the pol gene. Classification of the CRF02_AG sequences was further confirmed by recombination breakpoint analysis, which revealed a mosaic composition similar to the reference strain IbNG. Analysis of the RT genes for resistance-associated substitutions revealed two sequences containing a V118I substitution. Even though no other resistance-associated substitutions were found, the presence of V118I, which is implicated in resistance to reverse transcriptase inhibitors, in CRF02_AG strains infecting drug-naive individuals should be considered when introducing these antiretrovirals in areas where CRF02_AG is the predominant subtype, such as Cameroon.

To describe the presence of protease inhibitor (PI) resistance-associated mutations and subtype distribution in drug-naive villagers of six provinces of Cameroon, we sequenced the protease (PR) gene (297 bp) of 128 viruses. Secondary PI resistance-associated mutations were identified at five sites: L10I/V (16%), K20R (8%), M36I (98%), L63P (13%), and V77I (6%). No primary mutation in the PR was identified. Of the 128 specimens analyzed, subtypes A (11%), C(2%), D (6%), F2 (3%), G (6%), H (0.8%), J (6%), and CRF02_AG (60%) were identified. The mutations identified were not characteristic to any particular subtype. The absence of primary mutations, in addition to the few secondary mutations, gives good perspectives for PI treatment interventions in these rural areas.

Though the HIV-1 subtypes infecting patients living in urban and semi-urban areas in Cameroon have been reported, information on the subtypes infecting patients in rural villages is lacking. To begin to understand the diversity of the HIV-1 group M subtypes infecting persons living in rural villages in the equatorial rain forest regions of Cameroon, 49 plasma samples from 14 rural villages in four provinces of Cameroon were analyzed using heteroduplex mobility analysis (HMA), DNA sequencing, and phylogenetic tree analysis on the basis of env C2V5, gag, or pol regions. Sixty-one percent of the group M infections were clade A or CRF02_AG-like as subtyped by env and gag. Of the remaining group M infections, 12% were either A or CRF02_AG-like or CRF01_AE-like in recombination with other clades; 25% were infections that were entirely non-A or non-CRF02_AG-like; and 2% were CRF11_cpx. The HIV-1 group M clades identified included A, D, F (F2), G, and H. The CRF strains identified were CRF02_AG-like, CRF01_AE-like, and CRF11_cpx. Two new intersubtype recombinant infections, H/G and A/F2, were identified. This study suggests that the HIV-1 diversity in rural villages in the equatorial rain forest of Cameroon is at least as broad as has been observed in major cities of Cameroon and that multiple HIV-1 group M subtypes are infecting persons living in the countryside of Cameroon.

Objective: To evaluate HIV-1 antibody seroprevalence and risk factors for HIV seropositivity in rural areas of Cameroon. Method: The prevalences of HIV antibodies in 53 villages in rural Cameroon visited during May–October 2000 were determined with an HIV1/2 rapid assay standard ELISA and western blot. Demographic data and risk factors were elicited via face-to-face interviews with a structured questionnaire. Results: HIV seroprevalence was 5.8% (243/4156 95% confidence interval [CI]=5.1–6.6) overall 6.3% (151/2394 95% CI=5.4–7.4) among females and 5.2% (92/1762 95% CI=4.3–6.4) among males. HIV seroprevalence among persons aged 15–70 years did not differ significantly by province (5.6% in Center 4.5% in East 6.9% in South and 5.8% in South-West) (p=.10). Analysis of age- and genderstandardized prevalence by village across provinces indicated a near-significant difference (nonparametric Wilcoxon signed rank test p=.06) with highest prevalence in South-West followed by South Center and East. Multivariate analysis revealed that single women were significantly more likely to be HIV seropositive than were married or widowed women. Women with a history of sexual relations while traveling were at significantly increased risk of HIV seropositivity (OR adjusted for age and marital status= 2.4 95% CI=1.4–9.7). Among men those who reported ever having a sexually transmitted disease were at significantly increased risk of HIVseropositivity (OR adjusted for age=1.8 95% CI=1.1–2.8). Conclusion: We have documented a wide range of HIV prevalences among rural villages of Cameroon. Age marital status (in women) and sexual risk factors appear to be associated with HIV infection in this setting. (author’s)

P34.11 LB Background: Superinfected HIV patients provide the unique opportunity to investigate the immune response after challenge with diverse HIV antigens and remain the major source for recombinant strain production. The competition and/or coexistence of two or more viral strains drive viral evolution and diversity, eventually triggering the generation of more broad and potent neutralizing antibodies (Abs) as compared to singly infected patients. The objective of this study was to analyze the genetic evolution of the viruses found within a superinfected Cameroonian patient, and to determine the neutralization sensitivity of the recombinant viruses to both autologous and heterologous neutralizing Abs. Methods: Longitudinal plasma samples from an HIV-1 superinfected Cameroonian patient were analyzed for their Env diversity, evolution, and recombination events. Pseudoviruses were generated from timepoints before, during, and after superinfection, and were then tested for sensitivity to homologous plasma and to heterologous neutralizing mAbs. Results: Env sequence analysis indicated that the CRF02_AG infected subject became superinfected with an F2 strain resulting in a massive increase in viral diversity. Later, the patient's viral repertoire was narrowed to quasispecies closely clustering with the initial strain. The highest neutralization was observed with autologous plasma from timepoints after superinfection but before the intiation of ART. Of interest, the superinfecting F2 strain was resistant to neutralization with most known broadly neutralizing antibodies (bnAbs) including PG09 and VRC01 while the original infecting CRF02_AG strain was sensitive to these bnAbs. Conclusions: The resistance of the F2 strain to known bnAbs urges the need to generate nAbs from such patients and to monitor the emerging recombinant strains. HIV-1 superinfected patients may serve for the generation of new bnAbs covering multiple subtypes and deliver important knowledge for future vaccine design.

P16.03 Background: A hallmark of HIV is its variability, which within group M viruses includes 9 subtypes and over 50 circulating recombinant forms (CRF)s. Cameroon is an epicenter of the disease known for circulation of many subtypes and CRFs, which provides a unique setting to study the immune response to HIV. It is crucial for a successful vaccine to elicit an adaptive immune response against a broad range of viral subtypes. Methods: We have performed subtype analysis of viral RNA isolated from the plasma of 63 HIV-1 infected Cameroonian subjects to verify non-B subtype infection and to monitor for recombination. From the non-B, drug naive cohort, we have isolated IgG (N=264) to screen for neutralization using a tier 2, pseudovirus panel including subtypes A1, B, C, and 01_AE. Samples capable of neutralizing multiple pseudoviruses at high potency were selected for further study to determine neutralization capacity against an extended panel and their ability to bind gp160 envelope peptides. Results: Subtypes A, D, F, G, and K were identified as well as many recombinant forms including the predominant subtype CRF02_AG. The neutralization screen concluded that 9.5% of the IgG samples were able to neutralize at least 2 pseudoviruses at low IgG concentrations. Neutralization of the extended panel revealed that these IgG samples were also able to neutralize 02_AG,G, and AC subtypes. We found that all of the broadly neutralizing IgG samples bound envelope protein gp41, over 80% bound gp120 proteins, 79% bound a scaffolded V1V2 peptide, and 100% of the samples bound cyclic V3 constructs. Conclusions: We have taken the first look at broad neutralization in a cohort infected with non-B subtype viruses and numerous CRFs. IgG from these patients is capable of neutralizing pseudoviruses across clades with high breadth and potency. We have shown that these samples bind strongly to envelope peptides and hope to continue to elucidate how these antibodies are conferring neutralization in order to guide future vaccine design.

Information is lacking on the prevalence of hepatitis C virus (HCV) infection in most African countries. An algorithm based on a combination of enzyme immunoassays (EIAs) with different formats (a commercial test, an HCV antibody [Ab] III test, and an HCV core Ab EIA) was used to estimate the prevalence of HCV infection in different population groups from southern Cameroon. An overall high prevalence was observed, with a significant increasing trend for both sexes with respect to age. A high proportion (67.4%) of HCV-positive sera were viremic as demonstrated by the reverse transcription-polymerase chain reaction. We conclude that the prevalence of HCV is high in southern Cameroon and increases linearly with age.

Recent studies have demonstrated that both the potency and breadth of the humoral anti-HIV-1 immune response in generating neutralizing antibodies (nAbs) against heterologous viruses are significantly enhanced after superinfection by discordant HIV-1 subtypes, suggesting that repeated exposure of the immune system to highly diverse HIV-1 antigens can significantly improve anti-HIV-1 immunity. Thus, we investigated whether sequential plasma from these subjects superinfected with discordant HIV-1 subtypes, who exhibit broad nAbs against heterologous viruses, also neutralize their discordant early autologous viruses with increasing potency. Comparing the neutralization capacities of sequential plasma obtained before and after superinfection of 4 subjects to those of matched plasma obtained from 4 singly infected control subjects, no difference in the increase in neutralization capacity was observed between the two groups (p = 0.328). Overall, a higher increase in neutralization over time was detected in the singly infected patients (mean change in IC(50) titer from first to last plasma sample: 183.4) compared to the superinfected study subjects (mean change in IC(50) titer from first to last plasma sample: 66.5). Analysis of the Breadth-Potency Scores confirmed that there was no significant difference in the increase in superinfected and singly infected study subjects (p = 0.234). These studies suggest that while superinfection by discordant subtypes induces antibodies with enhanced neutralizing breadth and potency against heterologous viruses, the potency to neutralize their autologous viruses is not better than those seen in singly infected patients.

Our observations add to previous results on molecular epidemiology in different provinces in Cameroon demonstrating a high prevalence of CRF02_AG and subtype A accounting for 90% of circulating HIV-1 strains. The country-wide high prevalence of HIV-1 CRF02_AG in Cameroon compared with the relatively low prevalence of CRF02_AG in the Democratic Republic of Congo suggest an early founder effect of this AG recombinant in West Central Africa initiating major CRF02 epidemics. (excerpt)

To study how virus evolution affects neutralization sensitivity and to determine changes that occur in and around epitopes, we tested the ability of 13 anti-HIV-1 gp120 (anti-V2, anti-V3, anti-CD4bd and anti-carbohydrate) human monoclonal antibodies (mAbs) to neutralize sequential viruses obtained from five HIV-1 chronically infected drug naïve individuals. Overall, primary viruses collected from patients at first visit were resistant to neutralization by all anti-HIV-1 mAbs with the exception of one virus sensitive to IgG1b12. Four of the five patients' viruses evolved increased sensitivity to neutralization by anti-V3 mAbs. Virus collected from a patient obtained 31 months later, evolved increased sensitivity to anti-V2, anti-V3, and anti-CD4bd mAbs. Furthermore, the anti-V2 and anti-CD4bd mAbs also exhibited increased neutralization capacities against virus collected from a patient 29 months later. Of the seven anti-V3 mAbs, five showed increased potency to neutralize the evolved virus from a patient collected after 11 months, and three exhibited increased potency against viruses from two patients collected 29 and 36 months later. Anti-V3 mAbs exhibited the most breadth and potency in neutralizing the evolving viruses. Sequence analysis of the envelope regions revealed amino acid conservation within the V3 loop, while most of the changes identified occurred outside the core epitopes and in particular within the C3 region; these may account for increased neutralization sensitivity. These studies demonstrate that in vivo, HIV-1 can evolve increased neutralization sensitivity to mAbs and that the spectrum of neutralization capacities by mAbs can be broader when studied in longitudinal analysis.