HLA-associated Mutations Research Articles

HAMdetector: a Bayesian regression model that integrates information to detect HLA-associated mutations.

A key process in anti-viral adaptive immunity is that the human leukocyte antigen (HLA) system presents epitopes as major histocompatibility complex I (MHC I) protein-peptide complexes on cell surfaces and in this way alerts CD8+ cytotoxic T-lymphocytes (CTLs). This pathway exerts strong selection pressure on viruses, favoring viral mutants that escape recognition by the HLA/CTL system. Naturally, such immune escape mutations often emerge in highly variable viruses, e.g. HIV or HBV, as HLA-associated mutations (HAMs), specific to the hosts MHC I proteins. The reliable identification of HAMs is not only important for understanding viral genomes and their evolution, but it also impacts the development of broadly effective anti-viral treatments and vaccines against variable viruses. By their very nature, HAMs are amenable to detection by statistical methods in paired sequence/HLA data. However, HLA alleles are very polymorphic in the human host population which makes the available data relatively sparse and noisy. Under these circumstances, one way to optimize HAM detection is to integrate all relevant information in a coherent model. Bayesian inference offers a principled approach to achieve this. We present a new Bayesian regression model for the detection of HAMs that integrates a sparsity-inducing prior, epitope predictions and phylogenetic bias assessment, and that yields easily interpretable quantitative information on HAM candidates. The model predicts experimentally confirmed HAMs as having high posterior probabilities, and it performs well in comparison to state-of-the-art models for several datasets from individuals infected with HBV, HDV and HIV. The source code of this software is available at https://github.com/HAMdetector/Escape.jl under a permissive MIT license. The data underlying this article were provided by permission. Data will be shared on request to the corresponding author with permission of the respective co-authors. Supplementary data are available at Bioinformatics online.

Effect of Difference in Consensus Sequence between HIV-1 Subtype A/E and Subtype B Viruses on Elicitation of Gag-Specific CD8+ T Cells and Accumulation of HLA-Associated Escape Mutations.

The Gag280 mutation is associated with HLA-C*01:02 but not with HLA-B*52:01 in subtype A/E-infected individuals, whereas this mutation is associated with HLA-B*52:01 but not with HLA-C*01:02 in subtype B infections. Although it is known that the Gag280 mutant is selected by HLA-B*52:01-restricted GagRI8 (Gag275-282)-specific T cells in subtype B infections, it remains unknown why this Gag280 mutation is associated with HLA-C*01:02 rather than HLA-B*52:01 in subtype A/E infections. The subtype B and A/E viruses have different consensus sequence, with Thr and Val at Gag280, respectively. To clarify the effect of this difference in Gag280 consensus sequence, we investigated the role of HLA-C*01:02-restricted GagYI9 (Gag277-285)-specific T cells in selection of Gag280 mutations in subtype A/E-infected Vietnamese and subtype B-infected Japanese individuals. GagYI9-4V-specific T cells, which were frequently elicited in Vietnamese individuals infected with the consensus-type A/E virus, failed to recognize GagV280T mutant A/E virus-infected cells. GagYI9-4T mutant epitope-specific T cells, which were weakly elicited in individuals infected with the mutant A/E virus, had weak or no ability to recognize the mutant virus. These results account for the mechanism for selection and accumulation of GagV280T mutants in the case of subtype A/E infections. In contrast, HLA-C*01:02-restricted GagYI9-4T-specific T cells were weakly elicited in Japanese individuals infected with the subtype B virus, explaining why HLA-C*01:02-restricted Gag280 mutations are not accumulated in the case of a subtype B infection. The present study demonstrated that a difference in the Gag280 consensus sequence influenced the elicitation of the GagYI9-specific T cells involved in the accumulation of HLA-C*01:02-associated Gag280 mutations.IMPORTANCE HIV-1 mutations escaped from HIV-specific CD8+ T cells are mostly detected as HLA-associated mutations. A diversity of HLA-associated mutations is somewhat distinct to each race and region, since HLA allele distribution differs among them. A difference in the consensus sequence among HIV-1 subtypes may also influence the diversity of HLA-associated mutations. HLA-C*01:02-associated GagV280T and HLA-B*52:01-associated GagT280A/S mutations were previously identified in HIV-1 subtype A/E-infected and subtype B-infected individuals, respectively, though these subtype viruses have a different consensus sequence at Gag280. We demonstrated that the GagV280T mutant virus was selected by HLA-C*01:02-restricted GagYI9-4V-specific T cells in subtype A/E-infected Vietnamese but that HLA-C*01:02-restricted GagYI9-4T-specific T cells were weakly elicited in subtype B-infected Japanese. Together with our recent study which demonstrated the mechanism for the accumulation of HLA-B*52:01-associated mutations, we clarified the mechanism for the accumulation of different Gag280 mutations and the effect of the difference in the consensus sequence on the accumulation of escape mutations.

Consequences of HLA-associated mutations in HIV-1 subtype C Nef on HLA-I downregulation ability.

Identification of CD8+ T lymphocyte (CTL) escape mutations that compromise the pathogenic functions of the Nef protein may be relevant for an HIV-1 attenuation-based vaccine. Previously, HLA-associated mutations 102H, 105R, 108D, and 199Y were individually statistically associated with decreased Nef-mediated HLA-I downregulation ability in a cohort of 298 HIV-1 subtype C infected individuals. In the present study, these mutations were introduced by site-directed mutagenesis into different patient-derived Nef sequence backgrounds of high similarity to the consensus C Nef sequence, and their ability to downregulate HLA-I was measured by flow cytometry in a CEM-derived T cell line. A substantial negative effect of 199Y on HLA-I downregulation and Nef expression was observed, while 102H and 105R displayed negative effects on HLA-I downregulation ability and Nef expression to a lesser extent. The total magnitude of CTL responses in individuals harboring the 199Y mutation was lower than those without the mutation, although this was not statistically significant. Overall, a modest positive relationship between Nef-mediated HLA-I downregulation ability and total magnitude of CTL responses was observed, suggesting that there is a higher requirement for HLA-I downregulation with increased CTL pressure. These results highlight a region of Nef that could be targeted by vaccine-induced CTL to reduce HLA-I downregulation and maximize CTL efficacy.

Human Leukocyte Antigen-Associated HIV-1 CRF02_AG gag and vif Polymorphisms in Ghana.

In human immunodeficiency virus type-1 (HIV-1) infections, cytotoxic T-lymphocyte (CTL) responses targeting human leukocyte antigen (HLA)-restricted viral epitopes exert strong suppressive pressure on viral replication and frequently select for mutations resulting in viral escape from CTL recognition. Numerous data on these HLA-associated mutations in HIV-1 subtypes B and C have been amassed with few reports described in other subtypes. In the present study, we investigated the HLA-associated mutations in HIV-1 subtype CRF02_AG prevailing in Ghana, Western Africa. We determined viral gag sequences in 246 out of 324 HIV-1-infected Ghanaians. Phylogeny analysis revealed that 200 (81.3%) individuals were infected with HIV-1 CRF02_AG. Full gag and vif sequences were obtained from 199 and 138, respectively, out of the 200 individuals infected with CRF02_AG and subjected to determination of HLA-associated mutations. The analysis found HLA-associated HIV-1 CRF02_AG non-synonymous polymorphisms at 19 sites; 13 in gag and six in vif, including those that were newly determined. Generation of this data is an important contribution to our understanding of HIV-1 CRF02_AG and host T cell interaction.

Impact of a single HLA-A*24:02-associated escape mutation on the detrimental effect of HLA-B*35:01 in HIV-1 control.

BackgroundHLA-B*35 is an HLA allele associated with rapid progression to AIDS. However, a mechanism underlying the detrimental effect of HLA-B*35 on disease outcome remains unknown. Recent studies demonstrated that most prevalent subtype HLA-B*35:01 is a detrimental allele in HIV-1 clade B-infected individuals. We here investigated the effect of mutations within the epitopes on HLA-B*35:01-restricted CD8+ T cells having abilities to suppress HIV-1 replication.MethodsWe analyzed 16 HLA-B*35:01-restricted epitope-specific T cells in 63 HIV-1 clade B-infected Japanese B*35:01+ individuals and identified HLA-B*35:01-restricted CD8+ T cells having abilities to suppress HIV-1 replication. We further analyzed the effect of HLA-associated mutations on the ability of these T cells.FindingsThe breadth of T cell responses to 4 epitopes was inversely associated with plasma viral load (pVL). However, the accumulation of an Y135F mutation in NefYF9 out of the 4 epitopes, which is selected by HLA-A*24:02-restricted T cells, affected the ability of YF9-specific T cells to suppress HIV-1 replication. HLA-B*35:01+ individuals harboring this mutation had much higher pVL than those without it. YF9-specific T cells failed to suppress replication of the Y135F mutant in vitro. These results indicate that this mutation impairs suppression of HIV-1 replication by YF9-specific T cells.InterpretationThese findings indicate that the Y135F mutation is a key factor underlying the detrimental effect of HLA-B*35:01 on disease outcomes in HIV-1 clade B-infected individuals.FundGrants-in-aid for AIDS Research from AMED and for scientific research from the Ministry of Education, Science, Sports, and Culture, Japan.

HLA Class I-Mediated HIV-1 Control in Vietnamese Infected with HIV-1 Subtype A/E.

HIV-1-specific cytotoxic T cells (CTLs) play an important role in the control of HIV-1 subtype B or C infection. However, the role of CTLs in HIV-1 subtype A/E infection still remains unclear. Here we investigated the association of HLA class I alleles with clinical outcomes in treatment-naive Vietnamese infected with subtype A/E virus. We found that HLA-C*12:02 was significantly associated with lower plasma viral loads (pVL) and higher CD4 counts and that the HLA-A*29:01-B*07:05-C*15:05 haplotype was significantly associated with higher pVL and lower CD4 counts than those for individuals without these respective genotypes. Nine Pol and three Nef mutations were associated with at least one HLA allele in the HLA-A*29:01-B*07:05-C*15:05 haplotype, with a strong negative correlation between the number of HLA-associated Pol mutations and CD4 count as well as a positive correlation with pVL for individuals with these HLA alleles. The results suggest that the accumulation of mutations selected by CTLs restricted by these HLA alleles affects HIV control.IMPORTANCE Most previous studies on HLA association with disease progression after HIV-1 infection have been performed on cohorts infected with HIV-1 subtypes B and C, whereas few such population-based studies have been reported for cohorts infected with the Asian subtype A/E virus. In this study, we analyzed the association of HLA class I alleles with clinical outcomes for 536 HIV-1 subtype A/E-infected Vietnamese individuals. We found that HLA-C*12:02 is protective, while the HLA haplotype HLA-A*29:01-B*07:05-C*15:05 is deleterious. The individuals with HIV-1 mutations associated with at least one of the HLA alleles in the deleterious HLA haplotype had higher plasma viral loads and lower CD4 counts than those of individuals without the mutations, suggesting that viral adaptation and escape from HLA-mediated immune control occurred. The present study identifies a protective allele and a deleterious haplotype for HIV-1 subtype A/E infection which are different from those identified for cohorts infected with HIV-1 subtypes B and C.

Accumulation of Pol Mutations Selected by HLA-B*52:01-C*12:02 Protective Haplotype-Restricted Cytotoxic T Lymphocytes Causes Low Plasma Viral Load Due to Low Viral Fitness of Mutant Viruses.

Numerous population-based studies identified HLA-associated HIV-1 mutations to predict HIV-1 escape mutations from cytotoxic T lymphocytes (CTLs). However, the majority of these HLA-associated mutations have not been identified as CTL escape mutations. Our previous population-based study showed that five HLA-B*52:01-associated mutations at four Pol positions were inversely correlated with the plasma viral load in HLA-B*52:01-negative Japanese individuals. In the present study, we demonstrated that these mutations were indeed selected by CTLs specific for novel B*52:01- and C*12:02-restricted epitopes and that the accumulation of these mutations reduced the viral fitness in vitro This study elucidated the mechanism by which the accumulation of these CTL escape mutations contributed to the protective effect of the HLA-B*52:01-HLA-C*12:02 haplotype on disease progression in HIV-1-infected Japanese individuals.

Early evolution of human leucocyte antigen-associated escape mutations in variable Gag proteins predicts CD4+ decline in HIV-1 subtype C-infected women.

HIV-1 escape from cytotoxic T-lymphocytes results in the accumulation of human leucocyte antigen (HLA)-associated mutations in the viral genome. To understand the contribution of early escape to disease progression, this study investigated the evolution and pathogenic implications of cytotoxic T-lymphocyte escape in a cohort followed from infection for 5 years. Viral loads and CD4 cell counts were monitored in 78 subtype C-infected individuals from onset of infection until CD4 cell count decline to less than 350 cells/μl or 5 years postinfection. The gag gene was sequenced and HLA-associated changes between enrolment and 12 months postinfection were mapped. HLA-associated escape mutations were identified in 48 (62%) of the participants and were associated with CD4 decline to less than 350 cells/μl (P = 0.05). Escape mutations in variable Gag proteins (p17 and p7p6) had a greater impact on disease progression than escape in more conserved regions (p24) (P = 0.03). The association between HLA-associated escape mutations and CD4 decline was independent of protective HLA allele (B57, B58 : 01 and B81) expression. The high frequency of escape contributed to rapid disease progression in this cohort. Although HLA-adaption in both conserved and variable Gag domains in the first year of infection was detrimental to long-term clinical outcome, escape in variable domains had greater impact.

Variable processing and cross-presentation of HIV by dendritic cells and macrophages shapes CTL immunodominance and immune escape.

Dendritic cells (DCs) and macrophages (Møs) internalize and process exogenous HIV-derived antigens for cross-presentation by MHC-I to cytotoxic CD8+ T cells (CTL). However, how degradation patterns of HIV antigens in the cross-presentation pathways affect immunodominance and immune escape is poorly defined. Here, we studied the processing and cross-presentation of dominant and subdominant HIV-1 Gag-derived epitopes and HLA-restricted mutants by monocyte-derived DCs and Møs. The cross-presentation of HIV proteins by both DCs and Møs led to higher CTL responses specific for immunodominant epitopes. The low CTL responses to subdominant epitopes were increased by pretreatment of target cells with peptidase inhibitors, suggestive of higher intracellular degradation of the corresponding peptides. Using DC and Mø cell extracts as a source of cytosolic, endosomal or lysosomal proteases to degrade long HIV peptides, we identified by mass spectrometry cell-specific and compartment-specific degradation patterns, which favored the production of peptides containing immunodominant epitopes in all compartments. The intracellular stability of optimal HIV-1 epitopes prior to loading onto MHC was highly variable and sequence-dependent in all compartments, and followed CTL hierarchy with immunodominant epitopes presenting higher stability rates. Common HLA-associated mutations in a dominant epitope appearing during acute HIV infection modified the degradation patterns of long HIV peptides, reduced intracellular stability and epitope production in cross-presentation-competent cell compartments, showing that impaired epitope production in the cross-presentation pathway contributes to immune escape. These findings highlight the contribution of degradation patterns in the cross-presentation pathway to HIV immunodominance and provide the first demonstration of immune escape affecting epitope cross-presentation.

Host-Specific Adaptation of HIV-1 Subtype B in the Japanese Population

The extent to which HIV-1 clade B strains exhibit population-specific adaptations to host HLA alleles remains incompletely known, in part due to incomplete characterization of HLA-associated HIV-1 polymorphisms (HLA-APs) in different global populations. Moreover, it remains unknown to what extent the same HLA alleles may drive significantly different escape pathways across populations. As the Japanese population exhibits distinctive HLA class I allele distributions, comparative analysis of HLA-APs between HIV-1 clade B-infected Japanese and non-Asian cohorts could shed light on these questions. However, HLA-APs remain incompletely mapped in Japan. In a cohort of 430 treatment-naive Japanese with chronic HIV-1 clade B infection, we identified 284 HLA-APs in Gag, Pol, and Nef using phylogenetically corrected methods. The number of HLA-associated substitutions in Pol, notably those restricted by HLA-B*52:01, was weakly inversely correlated with the plasma viral load (pVL), suggesting that the transmission and persistence of B*52:01-driven Pol mutations could modulate the pVL. Differential selection of HLA-APs between HLA subtype members, including those differing only with respect to substitutions outside the peptide-binding groove, was observed, meriting further investigation as to their mechanisms of selection. Notably, two-thirds of HLA-APs identified in Japan had not been reported in previous studies of predominantly Caucasian cohorts and were attributable to HLA alleles unique to, or enriched in, Japan. We also identified 71 cases where the same HLA allele drove significantly different escape pathways in Japan versus predominantly Caucasian cohorts. Our results underscore the distinct global evolution of HIV-1 clade B as a result of host population-specific cellular immune pressures. Cytotoxic T lymphocyte (CTL) escape mutations in HIV-1 are broadly predictable based on the HLA class I alleles expressed by the host. Because HLA allele distributions differ among worldwide populations, the pattern and diversity of HLA-associated escape mutations are likely to be somewhat distinct to each race and region. HLA-associated polymorphisms (HLA-APs) in HIV-1 have previously been identified at the population level in European, North American, Australian, and African cohorts; however, large-scale analyses of HIV-1 clade B-specific HLA-APs in Asians are lacking. Differential intraclade HIV-1 adaptation to global populations can be investigated via comparative analyses of HLA-associated polymorphisms across ethnic groups, but such studies are rare. Here, we identify HLA-APs in a large Japanese HIV-1 clade B cohort using phylogenetically informed methods and observe that the majority of them had not been previously characterized in predominantly Caucasian populations. The results highlight HIV's unique adaptation to cellular immune pressures imposed by different global populations.

Adapted HIV-1 epitopes can elicit functional CD8+ T cell responses (P6177)

Abstract HIV readily mutates and many of these mutations can be predicted based on the human leukocyte antigen class I (HLA-I) allele of the infected individual. Majority of these HLA-associated HIV polymorphisms may represent escape mutations whereby the epitope adapts to HLA-restricted pressure in every individual. Though these adapted epitopes have escaped recognition by some CD8 T cells, others may readily recognize them. However, to truly answer the question as to whether adapted epitopes induce CD8 T cell responses (primary response), acutely infected patient samples must be tested where we can accurately predict the infecting viral strain. We therefore tested whether CD8 T cells are induced when presented with either adapted or non-adapted epitopes encoded by the infecting viral strain in 8 HIV+ acute patients. Primary responses were more likely induced to non-adapted epitopes compared to the adapted (p=0.041). Furthermore, the few adapted epitopes that were able to elicit responses (primary or not) were predicted to exhibit a significantly higher HLA binding affinity compared to ones that did not elicit a response. CD8 T cells responding to adapted epitopes also shared similar magnitude, functional avidity, and polyfunctionality compared to those elicited to the non-adapted. Our results suggest at least some epitopes with HLA-associated mutations are still potentially immunogenic and may have important implications for T cell-based vaccine development.

ST111 Immune selection and vpu variability in a unique narrow source HIV-Positive village cohort

Background: HLA-class I associated selection pressure on HIV-1 evolution has been described in several cohorts and can leave characteristic “footprints” on HIV-1 strains (Moore et al, Science 2002). We had the opportunity to study a narrow source clade B’ HIV-1 infected Former Plasma Donors (FPD) village Cohort. We have previously reported that after 10 years of infection, clear HLA class I associated foot-prints are seen in the gag, pol and nef genes of bulk pro-viral DNA populations of untreated patients (Dong et al, Blood 2011). Here we present further studies from this cohort with the aim of defining and examining the selective pressures exerted on the vpu gene (which has important immune evasion functions). Methods: Samples were studied from 95 FDP in the village cohort using convenience sampling, collected an estimated 13-15 years after infection. We examined the sequences of HIV-1 vpu from plasma RNA, and assembled a consensus sequence, for which overlapping peptides were synthesised. The HLA class I and viral sequence data were analysed to determine the extent of HLA class I associations with sequence variation along the vpu sequence. Sites of strong class I associations were tested as possible HLA class I – restricted T-cell epitopes using overlapping peptides representing the cohort consensus vpu sequence in ELISpot assays, with cells from cohort members with the relevant HLA class I type. As antibody-dependent cellular cytotoxicity (ADCC) (Stratov et al, J Virology 2008) has been reported to select vpu variants a flow-cytometric ICS-based- assay was optimised for ADCC responses directed towards vpu. Results: Phylogenetic Analysis revealed the vpu sequences clustered together to reference B’ clade Chinese sequences. HLA association studies identified twenty-three mutations associated with vpu – amongst them, Position 27 and Position 38 of the vpu translated sequence were associated with HLA-B*13. Preliminary studies have demonstrated T-cell recognition of peptides containing these mutations in donors with appropriate HLA. Further studies underway will determine the optimal epitopes recognised, confirm the HLA restriction and demonstrate that the HLA-associated mutations represent T-cell escape mutations. Position A14 has been shown to be critical to vpu tetherin antagonism (Vigan et al, J Virology 2010), and our initial analysis reveals that there are a substantial proportion of A to V mutations in this position position A18 which may impact on tetherin binding. Further data on vpu T-cell and ADCC responses will be presented.

Aminopeptidase Substrate Preference Affects HIV Epitope Presentation and Predicts Immune Escape Patterns in HIV-Infected Individuals

Viruses evade immune detection partly through immune-associated mutations. Analyses of HIV sequences derived from infected individuals have identified numerous examples of HLA-associated mutations within or adjacent to T cell epitopes, but the potential impact of most mutations on epitope production and presentation remains unclear. The multistep breakdown of proteins into epitopes includes trimming of N-extended peptides into epitopes by aminopeptidases before loading onto MHC class I molecules. Definition of sequence signatures that modulate epitope production would lead to a better understanding of factors driving viral evolution and immune escape at the population level. In this study, we identified cytosolic aminopeptidases cleavage preferences in primary cells and its impact on HIV Ag degradation into epitopes in primary human cell extracts by mass spectrometry and on epitope presentation to CTL. We observed a hierarchy of preferred amino acid cleavage by cytosolic aminopeptidases. We demonstrated that flanking mutations producing more or less cleavable motifs can increase or decrease epitope production and presentation by up to 14-fold. We found that the efficiency of epitope production correlates with cleavability of flanking residues. These in vitro findings were supported by in vivo population-level analyses of clinically derived viral sequences from 1134 antiretroviral-naive HIV-infected individuals: HLA-associated mutations immune pressures drove the selection of residues that are less cleavable by aminopeptidases predominantly at N-flanking sites, leading to reduced epitope production and immune recognition. These results underscore an important and widespread role of Ag processing mutations in HIV immune escape and identify molecular mechanisms underlying impaired epitope presentation.

Association between amino acid mutations in Gag protein and human leukocyte antigen class I alleles in human immunodeficiency virus-1 B' infected Han Chinese people

To explore the human leukocyte antigen (HLA)-associated mutations in Gag protein of B' clade (human immunodeficiency virus-1) HIV-1 infected Han Chinese people and evaluate the impact of HLA associated Gag mutations on the disease progression of HIV infection. A total of 95 B' clade HIV-1 infected Han Chinese cases were recruited. The gag sequences were amplified from viral RNA and sequenced directly. HLA-I genotypes were detected with the assay of polymerase chain reaction-sequence specific primer (PCR-SSP). HLA-associated mutations were identified and the relationships between HLA-associated mutations and CD4+ T cell counts or plasma viral loads analyzed. Forty-seven kinds of mutations at 28 sites (15, 18, 26, 30, 34, 46, 62, 67, 81, 84, 90, 102, 118, 121, 122, 125, 146, 147, 173, 176, 252, 357, 374, 376, 437, 470, 471, 478) of Gag protein were significantly associated with particular HLA class I allelotypes (P < 0.05). Among which, 9 sites (26, 30, 81, 84, 125, 146, 147, 357, 437) were located within 13 known cytotoxic T-lymphocyte (CTL) epitopes or flanking regions. The number of HLA-associated mutations was significantly associated with both CD4 T cell counts (r = -0.318, P = 0.002) and viral loads (r = 0.360, P = 0.003). HLA-associated mutations may have a significant impact on HIV disease progression in B' clade HIV-1 infected Han Chinese population.

Gag-Protease-Mediated Replication Capacity in HIV-1 Subtype C Chronic Infection: Associations with HLA Type and Clinical Parameters

The mechanisms underlying HIV-1 control by protective HLA class I alleles are not fully understood and could involve selection of escape mutations in functionally important Gag epitopes resulting in fitness costs. This study was undertaken to investigate, at the population level, the impact of HLA-mediated immune pressure in Gag on viral fitness and its influence on HIV-1 pathogenesis. Replication capacities of 406 recombinant viruses encoding plasma-derived Gag-protease from patients chronically infected with HIV-1 subtype C were assayed in an HIV-1-inducible green fluorescent protein reporter cell line. Viral replication capacities varied significantly with respect to the specific HLA-B alleles expressed by the patient, and protective HLA-B alleles, most notably HLA-B81, were associated with lower replication capacities. HLA-associated mutations at low-entropy sites, especially the HLA-B81-associated 186S mutation in the TL9 epitope, were associated with lower replication capacities. Most mutations linked to alterations in replication capacity in the conserved p24 region decreased replication capacity, while most in the highly variable p17 region increased replication capacity. Replication capacity also correlated positively with baseline viral load and negatively with baseline CD4 count but did not correlate with the subsequent rate of CD4 decline. In conclusion, there is evidence that protective HLA alleles, in particular HLA-B81, significantly influence Gag-protease function by driving sequence changes in Gag and that conserved regions of Gag should be included in a vaccine aiming to drive HIV-1 toward a less fit state. However, the long-term clinical benefit of immune-driven fitness costs is uncertain given the lack of correlation with longitudinal markers of disease progression.

HLA-Associated Immune Pressure on Gag Protein in CRF01_AE-Infected Individuals and Its Association with Plasma Viral Load

BackgroundThe human leukocyte antigen (HLA)-restricted cytotoxic T-lymphocyte (CTL) immune response is one of the major factors determining the genetic diversity of human immunodeficiency virus (HIV). There are few population-based analyses of the amino acid variations associated with the host HLA type and their clinical relevance for the Asian population. Here, we identified HLA-associated polymorphisms in the HIV-1 CRF01_AE Gag protein in infected married couples, and examined the consequences of these HLA-selected mutations after transmission to HLA-unmatched recipients.Methodology/Principal FindingsOne hundred sixteen HIV-1-infected couples were recruited at a government hospital in northern Thailand. The 1.7-kb gag gene was amplified and directly sequenced. We identified 56 associations between amino acid variations in Gag and HLA alleles. Of those amino acid variations, 35 (62.5%) were located within or adjacent to regions reported to be HIV-specific CTL epitopes restricted by the relevant HLA. Interestingly, a significant number of HLA-associated amino acid variations appear to be unique to the CRF01_AE-infected Thai population. Variations in the capsid protein (p24) had the strongest associations with the viral load and CD4 cell count. The mutation and reversion rates after transmission to a host with a different HLA environment varied considerably. The p24 T242N variant escape from B57/58 CTL had a significant impact on the HIV-1 viral load of CRF01_AE-infected patients.Conclusions/SignificanceHLA-associated amino acid mutations and the CTL selection pressures on the p24 antigen appear to have the most significant impact on HIV replication in a CRF01_AE-infected Asian population. HLA-associated mutations with a low reversion rate accumulated as a footprint in this Thai population. The novel HLA-associated mutations identified in this study encourage us to acquire more extensive information about the viral dynamics of HLA-associated amino acid polymorphisms in a given population as effective CTL vaccine targets.

HLA-Associated Viral Mutations Are Common in Human Immunodeficiency Virus Type 1 Elite Controllers

HLA-Associated Viral Mutations Are Common in Human Immunodeficiency Virus Type 1 Elite Controllers

HLA-Associated Viral Mutations Are Common in Human Immunodeficiency Virus Type 1 Elite Controllers

Elite controllers (EC) of human immunodeficiency virus type 1 (HIV-1) maintain viremia below the limit of detection without antiretroviral treatment. Virus-specific cytotoxic CD8(+) T lymphocytes are believed to play a crucial role in viral containment, but the degree of immune imprinting and compensatory mutations in EC is unclear. We obtained plasma gag, pol, and nef sequences from HLA-diverse subjects and found that 30 to 40% of the predefined HLA-associated polymorphic sites show evidence of immune selection pressure in EC, compared to approximately 50% of the sites in chronic progressors. These data indicate ongoing viral replication and escape from cytotoxic T lymphocytes are present even in strictly controlled HIV-1 infection.

Protective HLA Class I Alleles That Restrict Acute-Phase CD8 + T-Cell Responses Are Associated with Viral Escape Mutations Located in Highly Conserved Regions of Human Immunodeficiency Virus Type 1

The control of human immunodeficiency virus type 1 (HIV-1) associated with particular HLA class I alleles suggests that some CD8(+) T-cell responses may be more effective than others at containing HIV-1. Unfortunately, substantial diversities in the breadth, magnitude, and function of these responses have impaired our ability to identify responses most critical to this control. It has been proposed that CD8 responses targeting conserved regions of the virus may be particularly effective, since the development of cytotoxic T-lymphocyte (CTL) escape mutations in these regions may significantly impair viral replication. To address this hypothesis at the population level, we derived near-full-length viral genomes from 98 chronically infected individuals and identified a total of 76 HLA class I-associated mutations across the genome, reflective of CD8 responses capable of selecting for sequence evolution. The majority of HLA-associated mutations were found in p24 Gag, Pol, and Nef. Reversion of HLA-associated mutations in the absence of the selecting HLA allele was also commonly observed, suggesting an impact of most CTL escape mutations on viral replication. Although no correlations were observed between the number or location of HLA-associated mutations and protective HLA alleles, limiting the analysis to mutations selected by acute-phase immunodominant responses revealed a strong positive correlation between mutations at conserved residues and protective HLA alleles. These data suggest that control of HIV-1 may be associated with acute-phase CD8 responses capable of selecting for viral escape mutations in highly conserved regions of the virus, supporting the inclusion of these regions in the design of an effective vaccine.

Selective Pressures of HLA Genotypes and Antiviral Therapy on Human Immunodeficiency Virus Type 1 Sequence Mutation at a Population Level

The objective of this study was a comprehensive analysis of the immune-driven evolution of viruses of human immunodeficiency virus type 1 (HIV-1) clade B in a large patient cohort treated at a single hospital in Germany and its implications for antiretroviral therapy. We examined the association of the HLA-A, HLA-B, and HLA-DRB1 alleles with the emergence of mutations in the complete protease gene and the first 330 codons of the reverse transcriptase (RT) gene of HIV-1, studying their distribution and persistence and their impact on antiviral drug therapy. The clinical data for 179 HIV-infected patients, the results of HLA genotyping, and virus sequences were analyzed using a variety of statistical approaches. We describe new HLA-associated mutations in both viral protease and RT, several of which are associated with HLA-DRB1. The mutations reported are remarkably persistent within our cohort, developing more slowly in a minority of patients. Interestingly, several HLA-associated mutations occur at the same positions as drug resistance mutations in patient viruses, where the viral sequence was acquired before exposure to these drugs. The influence of HLA on thymidine analogue mutation pathways was not observed. We were able to confirm immune-driven selection pressure by major histocompatibility complex (MHC) class I and II alleles through the identification of HLA-associated mutations. HLA-B alleles were involved in more associations (68%) than either HLA-A (23%) or HLA-DRB1 (9%). As several of the HLA-associated mutations lie at positions associated with drug resistance, our results indicate possible negative effects of HLA genotypes on the development of HIV-1 drug resistance.