Masao Hashimoto

A Molecular Basis for the Control of Preimmune Escape Variants by HIV-Specific CD8(+) T Cells.

The capacity of the immune system to adapt to rapidly evolving viruses is a primary feature of effective immunity, yet its molecular basis is unclear. Here, we investigated protective HIV-1-specific CD8+ T cell responses directed against the immunodominant p24 Gag-derived epitope KK10 (KRWIILGLNK263-272) presented by human leukocyte antigen (HLA)-B∗2705. We found that cross-reactive CD8+ T cell clonotypes were mobilized to counter the rapid emergence of HIV-1 variants that can directly affect T cell receptor (TCR) recognition. These newly recruited clonotypes expressed TCRs that engaged wild-type and mutant KK10 antigens with similar affinities and almost identical docking modes, thereby accounting for their antiviral efficacy in HLA-B∗2705+ individuals. A protective CD8+ T cell repertoire therefore encompasses the capacity to control TCR-accessible mutations, ultimately driving the development of more complex viral escape variants that disrupt antigen presentation.

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

ABSTRACT 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. IMPORTANCE 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 HIVs unique adaptation to cellular immune pressures imposed by different global populations.

Selection of escape mutant by HLA-C-restricted HIV-1 Pol-specific cytotoxic T lymphocytes carrying strong ability to suppress HIV-1 replication

HIV‐1 mutants escaping from HLA‐A‐ or HLA‐B‐restricted CTL have been well studied, but those from HLA‐C‐restricted CTL have not. Therefore we investigated the ability of HLA‐C‐restricted CTL to select HIV‐1 escape mutants. In the present study, we identified two novel HLA‐Cw*1202‐restricted Pol‐specific CTL epitopes (Pol328‐9 and Pol463‐10). CTL specific for these epitopes were detected in 25–40% of chronically HIV‐1‐infected HLA‐Cw*1202+ individuals and had strong abilities to kill HIV‐1‐infected cells and to suppress HIV‐1 replication in vitro, suggesting that these CTL may have the ability to effectively control HIV‐1 in some HLA‐Cw*1202+ individuals. Sequence analysis of these epitopes showed that a V‐to‐A substitution at the 9th position (V9A) of Pol 463‐10 was significantly associated with the HLA‐Cw*1202 allele and that the V9A mutant was slowly selected in the HLA‐Cw*1202+ individuals. Pol 463‐10‐specific CTL failed both to kill the V9A virus‐infected cells and to suppress replication of the V9A mutant. These results indicate that the V9A mutation was selected as an escape mutant by the Pol463‐10‐specific CTL. The present study strongly suggests that some HLA‐C‐restricted CTL have a strong ability to suppress HIV‐1 replication so that they can select HIV escape mutants as in the case of HLA‐A‐restricted or HLA‐B‐restricted CTL.

Different In Vivo Effects of HIV-1 Immunodominant Epitope-Specific Cytotoxic T Lymphocytes on Selection of Escape Mutant Viruses

ABSTRACT HIV-1 escape mutants are well known to be selected by immune pressure via HIV-1-specific cytotoxic T lymphocytes (CTLs) and neutralizing antibodies. The ability of the CTLs to suppress HIV-1 replication is assumed to be associated with the selection of escape mutants from the CTLs. Therefore, we first investigated the correlation between the ability of HLA-A*1101-restricted CTLs recognizing immunodominant epitopes in vitro and the selection of escape mutants. The result showed that there was no correlation between the ability of these CTLs to suppress HIV-1 replication in vitro and the appearance of escape mutants. The CTLs that had a strong ability to suppress HIV-1 replication in vitro but failed to select escape mutants expressed a higher level of PD-1 in vivo, whereas those that had a strong ability to suppress HIV-1 replication in vitro and selected escape mutants expressed a low level of PD-1. Ex vivo analysis of these CTLs revealed that the latter CTLs had a significantly stronger ability to recognize the epitope than the former ones. These results suggest that escape mutations are selected by HIV-1-specific CTLs that have a stronger ability to recognize HIV-1 in vivo but not in vitro.

CTL recognition of HIV-1-infected cells via cross-recognition of multiple overlapping peptides from a single 11-mer Pol sequence

It is known that overlapping HIV‐1 peptides of different lengths can be presented by a given HLA class I molecule. However, the role of those peptides in CD8+ T cells recognition of HIV‐1‐infected cells remains unclear. Here we investigated the recognition of overlapping 8‐mer to 11‐mer peptides of Pol 155–165 by HLA‐B*54:01‐restricted CD8+ T cells. The analysis of ex vivo T cells using ELISPOT and tetramer binding assays showed that there were different patterns of CD8+ T‐cell responses to these peptides among chronically HIV‐1‐infected HLA‐B*54:01+ individuals, though the response to the 9‐mer peptide was the strongest among them. CD8+ T‐cell clones with TCRs specific for the 9‐mer, 10‐mer, and/or 11‐mer peptides effectively killed HIV‐1‐infected cells. Together, these results suggest that the 9‐mer and 10‐mer peptides could be predominantly presented by HLA‐B*54:01, though it remains possible that the 11‐mer peptide was also presented by this HLA allele. The present study demonstrates effective CD8+ T‐cell recognition of HIV‐1‐infected cells via presentation of multiple overlapping HIV‐1 peptides and cross‐recognition by the CD8+ T cells.

Selection of escape mutation by Pol154-162-specific cytotoxic T cells among chronically HIV-1-infected HLA-B*5401-positive individuals.

Most escape mutations have been identified on cytotoxic T lymphocyte (CTL) epitopes presented by Caucasian or African human leukocyte antigen (HLA) class I alleles, whereas a limited number of studies have identified the escape mutations on epitopes presented by Asian alleles. HLA-B54 is a common HLA allele in Asian countries. We recently identified five HLA-B*5401-restricted HIV-1-specific CTL epitopes. We here investigated escape mutations in these CTL epitopes in Japanese HIV-1-infected individuals. The frequency of substitution from Glu (E) to Asp (D) at position 7 (FV9-7D) in the Pol 154-162 (FV9) epitope was significantly higher in HLA-B*5401(+) HIV-infected individuals than in HLA-B*5401(-) individuals, whereas substitutions that were significantly higher in HLA-B*5401(+) individuals than in HLA-B*5401(-) individuals were not found in the other four epitopes. FV9-specific CTLs showed reduced killing activity against target cells pulsed with the FV9-7D mutant peptide and failed to kill those infected with the FV9-7D mutant virus, strongly suggesting that FV9-7D is an escape mutant. Furthermore, longitudinal sequence analysis of the FV9 epitope in two HLA-B*5401(+) individuals revealed that the sequence had changed from the wild type to the FV9-7D during the clinical course. Taken together, these results indicate that the FV9-7D escape mutant had been selected by FV9-specific CTLs among chronically HIV-1-infected HLA-B*5401(+) individuals.

Fine-tuning of CD8|[plus]| T-cell effector functions by targeting the 2B4-CD48 interaction

Polyfunctionality and cytotoxic activity dictate CD8+ T‐cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T‐cell receptor (TCR) and its cognate peptide‐MHC class I complex, in addition to signals provided by co‐stimulatory or co‐inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co‐stimulatory or co‐inhibitory in modulating T‐cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8+ T‐cell clones. In this setting, we show that the 2B4‐CD48 axis is involved in the fine‐tuning of CD8+ T‐cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8+ T‐cell clone‐mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4‐CD48 interaction to the modulation of CD8+ T‐cell functional properties, potentially linked to intrinsic levels of T‐bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4‐CD48 interaction in the fine regulation of CD8+ T‐cell effector function upon antigenic stimulation.

Fine tuning of CD8+ T-cell effector functions by targeting the 2B4-CD48

Polyfunctionality and cytotoxic activity dictate CD8+ T‐cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T‐cell receptor (TCR) and its cognate peptide‐MHC class I complex, in addition to signals provided by co‐stimulatory or co‐inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co‐stimulatory or co‐inhibitory in modulating T‐cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8+ T‐cell clones. In this setting, we show that the 2B4‐CD48 axis is involved in the fine‐tuning of CD8+ T‐cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8+ T‐cell clone‐mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4‐CD48 interaction to the modulation of CD8+ T‐cell functional properties, potentially linked to intrinsic levels of T‐bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4‐CD48 interaction in the fine regulation of CD8+ T‐cell effector function upon antigenic stimulation.

Fine-tuning of CD8 + T-cell effector functions by targeting the 2B4-CD48 interaction

Polyfunctionality and cytotoxic activity dictate CD8+ T‐cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T‐cell receptor (TCR) and its cognate peptide‐MHC class I complex, in addition to signals provided by co‐stimulatory or co‐inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co‐stimulatory or co‐inhibitory in modulating T‐cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8+ T‐cell clones. In this setting, we show that the 2B4‐CD48 axis is involved in the fine‐tuning of CD8+ T‐cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8+ T‐cell clone‐mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4‐CD48 interaction to the modulation of CD8+ T‐cell functional properties, potentially linked to intrinsic levels of T‐bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4‐CD48 interaction in the fine regulation of CD8+ T‐cell effector function upon antigenic stimulation.

Fine tuning of CD8+ T-cell effector functions by targeting the 2B4-CD48: Role of the 2B4-CD48 axis in CD8+ T-cell function

Polyfunctionality and cytotoxic activity dictate CD8+ T‐cell efficacy in the eradication of infected and malignant cells. The induction of these effector functions depends on the specific interaction between the T‐cell receptor (TCR) and its cognate peptide‐MHC class I complex, in addition to signals provided by co‐stimulatory or co‐inhibitory receptors, which can further regulate these functions. Among these receptors, the role of 2B4 is contested, as it has been described as either co‐stimulatory or co‐inhibitory in modulating T‐cell functions. We therefore combined functional, transcriptional and epigenetic approaches to further characterize the impact of disrupting the interaction of 2B4 with its ligand CD48, on the activity of human effector CD8+ T‐cell clones. In this setting, we show that the 2B4‐CD48 axis is involved in the fine‐tuning of CD8+ T‐cell effector function upon antigenic stimulation. Blocking this interaction resulted in reduced CD8+ T‐cell clone‐mediated cytolytic activity, together with a subtle drop in the expression of genes involved in effector function regulation. Our results also imply a variable contribution of the 2B4‐CD48 interaction to the modulation of CD8+ T‐cell functional properties, potentially linked to intrinsic levels of T‐bet expression and TCR avidity. The present study thus provides further insights into the role of the 2B4‐CD48 interaction in the fine regulation of CD8+ T‐cell effector function upon antigenic stimulation.