gp120 sequences from HIV type 1 subtype C early seroconverters in India

Broadly Neutralizing Antibody Responses in a Subset of HIV-1-Infected Individuals in Chennai, India

Identification of broadly neutralizing antibodies (NAbs) generated during the course of HIV-1 infection is essential for effective HIV-1 vaccine design. The magnitude and breadth of neutralizing activity in the sera from 46 antiretroviral treatment-naive HIV-1 clade C-infected individuals was measured in a single round infection assay using TZM-bl cells and multisubtype panel of env-pseudotyped viruses. Higher levels of NAb response (NAb titer 500 to >40 000) were measured in these patients against tier 1 and tier 2 viruses. The average magnitude of the NAb responses of chronically infected individuals against heterologous viruses was consistently higher than the response observed from individuals with long-term nonprogressor ( P = .086). To conclude, high titers of HIV-1 cross-neutralizing activity were observed in the sera from a subset of HIV-1-infected individuals in Chennai, India. Additional studies of the epitopes recognized by these antibodies may facilitate the discovery of an effective vaccine immunogen.

Global analysis of sequence diversity within HIV-1 subtypes across geographic regions

AIMS: HIV-1 sequence diversity can affect host immune responses and phenotypic characteristics such as antiretroviral drug resistance. Current HIV-1 sequence diversity classification uses phylogeny-based methods to identify subtypes and recombinants, which may overlook distinct subpopulations within subtypes. While local epidemic studies have characterized sequence-level clustering within subtypes using phylogeny, identification of new genotype - phenotype associations are based on mutational correlations at individual sequence positions. We perform a systematic, global analysis of position-specific pol gene sequence variation across geographic regions within HIV-1 subtypes to characterize subpopulation differences that may be missed by standard subtyping methods and sequence-level phylogenetic clustering analyses. MATERIALS #ENTITYSTARTX00026; METHODS: Analysis was performed on a large, globally diverse, cross-sectional pol sequence dataset. Sequences were partitioned into subtypes and geographic subpopulations within subtypes. For each subtype, we identified positions that varied according to geography using VESPA (viral epidemiology signature pattern analysis) to identify sequence signature differences and a likelihood ratio test adjusted for multiple comparisons to characterize differences in amino acid (AA) frequencies, including minority mutations. Synonymous nonsynonymous analysis program (SNAP) was used to explore the role of evolutionary selection witihin subtype C. RESULTS: In 7693 protease (PR) and reverse transcriptase (RT) sequences from untreated patients in multiple geographic regions, 11 PR and 11 RT positions exhibited sequence signature differences within subtypes. Thirty six PR and 80 RT positions exhibited within-subtype geography-dependent differences in AA distributions, including minority mutations, at both conserved and variable loci. Among subtype C samples from India and South Africa, nine PR and nine RT positions had significantly different AA distributions, including one PR and five RT positions that differed in consensus AA between regions. A selection analysis of subtype C using SNAP demonstrated that estimated rates of nonsynonymous and synonymous mutations are consistent with the possibility of positive selection across geographic subpopulations within subtypes. CONCLUSION: We characterized systematic genotypic pol differences across geographic regions within subtypes that are not captured by the subtyping nomenclature. Awareness of such differences may improve the interpretation of future studies determining the phenotypic consequences of genetic backgrounds.

Variations in autologous neutralization and CD4 dependence of b12 resistant HIV-1 clade C env clones obtained at different time points from antiretroviral naïve Indian patients with recent infection

Background

Limited information is available on HIV-1 Indian clade C sensitivities to autologous antibodies during the course of natural infection. In the present study, a total of 37 complete envelope clones (Env) were amplified at different time points predominantly from the plasma of five Indian patients with recent HIV-1 infection and envelope-pseudotyped viruses were examined for their magnitude of sensitivity to autologous plasma antibodies during natural course of infection.

Results

Variable low levels of neutralization were consistently detected with contemporaneous autologous plasma. In contrast to clade B and African clade C HIV-1 envelopes, Env clones obtained from four patients were found to be resistant to IgG1b12. The majority of the Env clones were resistant to 2G12 and 2F5 due to the absence of the minimal motifs required for antibody recognition, but were sensitive to 4E10. Nonetheless, Env clones from one patient were found to be sensitive to 2G12, atypical for clade C, and one Env clone exhibited unusual sensitivity to 17b, suggesting spontaneous exposure of CD4i epitopes. Phylogenetic analysis revealed that Env clones were closely clustered within patients. Variation in the potential N-linked glycosylation pattern also appeared to be different in patients over the course of infection. Interestingly, we found that the sensitivity of Envs to contemporaneous autologous NAbs correlated positively with increased sensitivity to soluble CD4 and inversely with anti-CD4 antibody and Envs with increased NAb sensitivity were able to efficiently infect HeLa cells expressing low CD4.

Conclusion

Our data showed considerable variations in autologous neutralization of these early HIV-1 clade C Envs in each of these patients and indicate greater exposure to CD4 of Envs that showed increased autologous neutralization. Interestingly, Env clones obtained from a single patient at different time points were found to retain sensitivity to b12 antibody that binds to CD4 binding site in Env in contrast to Envs obtained from other patients. However, we did not find any association between increased b12 sensitivity of Envs obtained from this particular patient with their degree of exposure to CD4.

Evolution of HIV-1 in India

Nearly 25 years after the discovery of the human immunodeficiency virus type 1 (HIV-1) effective control of the AIDS pandemic remains elusive. At the root of this challenge is the evolution of this virus to elude immune control. Error-prone nature of replication and retro-transcription is the hallmark of this virus. This fidelity of replication in HIV-1 is due to the absence of proof-reading/repair and post-replicative error correction mechanisms that normally operate during replication of DNA viruses. Advances in sequencing technology and expanded disease surveillance have allowed researchers to characterize the variation in HIV-1 around the world and within individual patient overtime. Although HIV-1 has been classified into distinct subtypes, the classification does not reflect dynamic genetic evolution of HIV-1 through which new strains are constantly emerging. The resultant viral diversity has implications for differential rates of disease progression in different geographical areas, differential responses to antiretroviral therapy (including the development of resistance), and vaccine development. In this review evolution of HIV-1 in India is discussed.

Highly complex neutralization determinants on a monophyletic lineage of newly transmitted subtype C HIV-1 Env clones from India

Little is known about the neutralization properties of HIV-1 in India to optimally design and test vaccines. For this reason, a functional Env clone was obtained from each of ten newly acquired, heterosexually transmitted HIV-1 infections in Pune, Maharashtra. These clones formed a phylogenetically distinct genetic lineage within subtype C. As Env-pseudotyped viruses the clones were mostly resistant to IgG1b12, 2G12 and 2F5 but all were sensitive to 4E10. When compared to a large multi-subtype panel of Env-pseudotyped viruses (subtypes B, C and CRF02_AG) in neutralization assays with a multi-subtype panel of HIV-1-positive plasma samples, the Indian Envs were remarkably complex. With the exception of the Indian Envs, results of a hierarchical clustering analysis showed a strong subtype association with the patterns of neutralization susceptibility. From these patterns we were able to identify 19 neutralization cluster-associated amino acid signatures in gp120 and 14 signatures in the ectodomain and cytoplasmic tail of gp41. We conclude that newly transmitted Indian Envs are antigenically complex in spite of close genetic similarity. Delineation of neutralization-associated amino acid signatures provides a deeper understanding of the antigenic structure of HIV-1 Env.

High replication fitness and transmission efficiency of HIV-1 subtype C from India: Implications for subtype C predominance

HIV-1 subtype C has been the predominant subtype throughout the course of the HIV-1 epidemic in India regardless of the geographic region of the country. In an effort to understand the mechanism of subtype C predominance in this country, we have investigated the in vitro replication fitness and transmission efficiency of HIV-1 subtypes A and C from India. Using a dual infection growth competition assay, we found that primary HIV-1 subtype C isolates had higher overall relative fitness in PBMC than subtype A primary isolates. Moreover, in an ex vivo cervical tissue derived organ culture, subtype C isolates displayed higher transmission efficiency across cervical mucosa than subtype A isolates. We found that higher fitness of subtype C was not due to a trans effect exerted by subtype C infected PBMC. A half genome A/C recombinant clone in which the 3' half of the viral genome of subtype A was replaced with the corresponding subtype C3' half, had similar replicative fitness as the parental subtype A. These results suggest that the higher replication fitness and transmission efficiency of subtype C virus compared to subtype A virus from India is most probably not due to the envelope gene alone and may be due to genes present within the 5' half of the viral genome or to a more complex interaction between the genes located within the two halves of the viral genome. These data provide a model to explain the asymmetric distribution of subtype C over other subtypes in India.

HIV infection in India: epidemiology, molecular epidemiology and pathogenesis

The year 1986 saw first case of HIV infection as well as first report of AIDS case in India. Since then the epidemic has spread throughout the country.In the recent years there is evidence of epidemic being stabilized with decrease in new infections reported from some parts of the country. The absolute number of HIV infections in the country is expected to be close to 2.5 million and National AIDS Control Programme, phase III is geared to contain the epidemic. HIV viruses circulating in India predominantly belong to HIV-1 subtype C. However, there have been occasional reports of HIV-1 subtype A and B. Matter of concern is reports of A/C and B/C mosaic viruses that are being reported from different parts of the country. The data on HIV drug resistance from India is rather limited. Most of the studies have shown that the virus strains from drug naive patients do not show significant level of drug resistance mutations. The few immunological studies in Indian patients show that the Indian HIV infected patients show both HIV-specific CTL responses as well as neutralizing antibody response. Mapping of CTL epitopes showed that while Indian patients identify same regions of Gag antigen as recognized by South African subtype C infected patients, some regions are uniquely recognized by Indian patients. There are very few studies on host genetic factors in India in context with HIV infection.However there are evidences reported of association of host genetic factors such as HLA types and haplotypes and HIV disease.

Neutralizing antibody responses in recent seroconverters with HIV-1 subtype C infections in India

The longitudinal heterologous neutralization response against two HIV-1 subtype C isolates was studied in 33 ART-naive individuals recently infected with HIV-1 subtype C from India. Seven of 33 (21%) seroconverters demonstrated a consistent response against both isolates (65-100% neutralization), whereas the remaining 26 (79%) were nonresponders. Four of the seven responders demonstrated a neutralization response (>75% neutralization) within 2-3 months of infection and in the remaining three, the response was demonstrated between 22 and 38 months after infection. In the past, HIV vaccines targeted the V3 region for the development of neutralizing antibodies. However, recent studies have shown that anti-V3 antibodies are generated after HIV-1 infection, but are not effective in neutralizing virus. In this study, the V3 sequences of HIV-1 from seven responders were analyzed and compared with those from nonresponders. The V3 region sequences from early and late responders did show certain mutations that were not found in the nonresponders; however none of these mutations could explain the neutralization responses. This suggested that HIV-1 envelope regions other than the V3 domain may be involved in generating a neutralization response. This is the first report that describes the pattern of emergence and persistence of the heterologous neutralization response in recently HIV-1 subtype C-infected individuals from India and studies its association with sequence variation in the V3 region.

Human immunodeficiency virus type 1 drug resistance mutations in peripheral blood mononuclear cell proviral DNA among antiretroviral treatment-naive and treatment-experienced patients from Pune, India

The prevalence of HIV drug resistance (HIVDR) mutations in the HIV protease (PR) and reverse transcriptase (RT) genes was estimated from peripheral blood mononuclear cells (PBMCs) in a study population of 25 antiretroviral (ARV) therapy-naive and 50 ARV-experienced chronically infected patients from Pune city, Maharashtra State, western India. Of the 75 study HIV-1 sequences, 73 belonged to subtype C and 2 to subtype A1. On phylogenetic analysis, the study subtype C sequences sub clustered randomly with different Indian and non-Indian subtype C sequences, emphasizing the HIV-1 subtype C pol gene diversity. The heterosexual route was the most common route of transmission (74.67%). There were no observable HIVDR mutations in ARV-naive patients. The ARV-experienced patients had a history of exposure to nucleoside reverse transcriptase inhibitor and nonnucleoside reverse transcriptase inhibitor combinations. At least one HIVDR mutation in RT was observed in 29 (80.55%) of ARV-experienced patients with evidence of failing therapy. M184V was the most common observed HIVDR mutation. No PR major mutations were observed among ARV-experienced patients. A higher prevalence of proviral HIVDR mutations in PBMCs was associated with irregular adherence to therapy (p < 0.05) and HIV-1 RNA levels > 1000 copies/ml (p < 0.001).

Extensive cross-reactive neutralizing antibody response in Indian patients with limited genetic diversity of HIV-1

Genome sequence analysis of HIV-1 subtype C viruses from India shows monophyletic lineage and relatively limited genetic diversity. To understand its immunological implication, cross-reactivity of neutralizing antibody response was investigated. In primary screening, neutralizing antibody response to single heterologous primary HIV-1 subtype C isolate was assessed in plasma samples from 235 HIV-1 infected, anti-retroviral treatment naive individuals from Pune, India. Plasma samples that showed > or =90% neutralization and two randomly selected plasma samples that showed 50-60% neutralization were tested against a panel of primary HIV-1 subtype C isolates obtained from epidemiologically unlinked individuals from India. The neutralizing antibody response showed extensive cross-neutralization, suggesting presence of shared neutralization determinants among circulating HIV-1 subtype C viruses in India.

Molecular analysis of gp41 sequences of HIV type 1 subtype C from India

Sequence polymorphism in HIV type 1 env gene is quite high, and there are little data available for subtype C env gp41 sequences from India. We have presented a molecular sequence analysis for gp41 region of env gene from HIV type 1 subtype C-infected individuals. The samples were obtained from 3 acute seroconverters and 5 seropositive individuals from India, one of whom was a minor. Heteroduplex mobility analysis using V3V5 and gp41 confirmed subtype C infection in all the study subjects. The sequences were analyzed for heterogeneity, polymorphism, and epitope recognition. The phylogenetic and SimPlot analysis showed the monophyletic lineage of Indian sequences. The phylogenetic tree constructed for the 286- to 506-bp region is highly variable and clearly distinguishes the subtype C sequences. The interpatient sequence comparison revealed high genetic diversity ranging from 0.0623 to 2.18 (median, 0.119). This supports the phylogeny where sequences belonging to the 8 study subjects form subclusters within Indian subtype C. A majority of the functional domains of gp41 are well conserved for the seroconverter and seropositive sequences. However, sequence polymorphism is high for the sequences obtained from the minor. The sequences of gp41 would provide valuable information regarding the diversity and its diagnostic implications in HIV/AIDS research.