A2 Supertype Research Articles

Divergent Peptide Presentations of HLA-A*30 Alleles Revealed by Structures With Pathogen Peptides

Human leukocyte antigen (HLA) alleles have a high degree of polymorphism, which determines their peptide-binding motifs and subsequent T-cell receptor recognition. The simplest way to understand the cross-presentation of peptides by different alleles is to classify these alleles into supertypes. A1 and A3 HLA supertypes are widely distributed in humans. However, direct structural and functional evidence for peptide presentation features of key alleles (e.g., HLA-A*30:01 and -A*30:03) are lacking. Herein, the molecular basis of peptide presentation of HLA-A*30:01 and -A*30:03 was demonstrated by crystal structure determination and thermostability measurements of complexes with T-cell epitopes from influenza virus (NP44), human immunodeficiency virus (RT313), and Mycobacterium tuberculosis (MTB). When binding to the HIV peptide, RT313, the PΩ-Lys anchoring modes of HLA-A*30:01, and -A*30:03 were similar to those of HLA-A*11:01 in the A3 supertype. However, HLA-A*30:03, but not -A*30:01, also showed binding with the HLA*01:01-favored peptide, NP44, but with a specific structural conformation. Thus, different from our previous understanding, HLA-A*30:01 and -A*30:03 have specific peptide-binding characteristics that may lead to their distinct supertype-featured binding peptide motifs. Moreover, we also found that residue 77 in the F pocket was one of the key residues for the divergent peptide presentation characteristics of HLA-A*30:01 and -A*30:03. Interchanging residue 77 between HLA-A*30:01 and HLA-A*30:03 switched their presented peptide profiles. Our results provide important recommendations for screening virus and tumor-specific peptides among the population with prevalent HLA supertypes for vaccine development and immune interventions.

KIR3DL1 alleles and their epistatic interactions with human leukocyte antigen class I influence resistance and susceptibility to HIV-1 acquisition in the Pumwani sex worker cohort.

To determine the associations of KIR3DL1/S1(3DL1/S1) and its epistatic interactions with human leukocyte antigen class I (HLA-I) alleles with resistance and susceptibility to HIV-1. Despite repeated exposure to HIV-1, a subset of women enrolled in the Pumwani sex worker cohort remain HIV uninfected. Previous studies have shown that specific HLA class I and II alleles were associated with this natural immunity. In this study, we investigated the association of 3DL1/S1 and its epistatic interactions with HLA-I, with resistance or susceptibility to HIV-1 acquisition. We used a sequence-based typing method to genotype 3DL1/S1 of 641 women in this cohort. The association of 3DL1/S1 and its epistatic interactions with HLA-I were analyzed using SPSS statistics software. 3DL1041 is enriched in the HIV-1-resistant women [P = 0.009, Pc = 0.0468, odds ratio (OR): 3.359, 95% confidence interval (CI): 1.39-8.32], whereas, 3DL1020 was associated with susceptibility to HIV-1 infection before correction for multiple comparisons (P = 0.029, Pc = 0.0858, OR: 0.316, 95%CI: 0.10-1.04). Epistatic interactions between several 3DL1 alleles and specific HLA-I alleles were observed. Among them the cocarriage of 3DL1041 with Bw4 (P = 1E - 05, Pc = 0.0015, OR: 13.33, 95%CI: 3.43-51.9), or Bw6 (P = 0.008, Pc = 0.272, OR: 3.92, 95%CI: 1.51-10.17), increased the odds of remaining HIV-1 uninfected. Further, 3DL1041+/Bw4+ women who entered the cohort HIV negative remained uninfected (P = 0.032, Pc = 0.0858). Cocarriage of 3DL101501 with C02 : 10 (P = 2.73E - 07, Pc = 7.0954E - 06), B15 : 03 (P = 3.21E - 04, Pc = 0.0042), A24 supertype (P = 8.89E - 04, Pc = 0.0077), or A23 : 01 (P = 0.0036, Pc = 0.0236) was associated with increased susceptibility to seroconversion. The effects of interactions between 3DL1 and HLA-I alleles on resistance/susceptibility to HIV-1 infection suggest that innate immunity plays an important role in HIV-1 acquisition and should be studied and explored for HIV prevention.

Improved Transgenic Mouse Model for Studying HLA Class I Antigen Presentation.

HLA class I (HLA-I) transgenic mice have proven to be useful models for studying human MHC-related immune responses over the last two decades. However, differences in the processing and presentation machinery between humans and mice may have profound effects on HLA-I restricted antigen presentation. In this study, we generated a novel human TAP-LMP (hTAP-LMP) gene cluster transgenic mouse model carrying an intact human TAP complex and two human immunoproteasome LMP subunits, PSMB8/PSMB9. By crossing the hTAP-LMP strain with different HLA-I transgenic mice, we found that the expression levels of human HLA-I molecules, especially the A3 supertype members (e.g., A11 and A33), were remarkably enhanced in corresponding HLA-I/hTAP-LMP transgenic mice. Moreover, we found that humanized processing and presentation machinery increased antigen presentation of HLA-A11-restricted epitopes and promoted the rapid reduction of hepatitis B virus (HBV) infection in HLA-A11/hTAP-LMP mice. Together, our study highlights that HLA-I/hTAP-LMP mice are an improved model for studying antigen presentation of HLA-I molecules and their related CTL responses.

Computational prediction and functional identification of HLA-A2-restricted T lymphocyte epitopes derived from swine leukocyte antigen (TRAN2P.962)

Abstract Xenotransplantation using porcine organs is a potential solution to the problem of the shortage of allografts. However, immunological rejection of xenografts remains as a major hurdle to success. Little information is available regarding the precise swine leukocyte antigen (SLA)-derived immunogenic peptides that are presented in the context of human HLA molecules. The SLA-derived peptides that bind to HLA-A*0201, a representative of the A2 supertype, were predicted using a computer-assisted algorithm. The candidate peptides were synthesized, and the stabilities of complexes formed between the peptides and HLA-A*0201 were compared using MHC stabilization assays. The cytotoxic T lymphocyte (CTL)-inducing activity of the selected peptides was examined in HLA-A*0201-transgenic mice. Among 15 candidate peptides synthesized, two peptides, peptide-35 (YLGPDGLLL) and peptide-43 (TLICHVDSI), were selected to have high affinity and stability with HLA-A*0201. Examination of the CTL-inducing activity of the two peptides in HLA-A*0201-transgenic mice showed that immunization with peptide-35, but not peptide-43, elicited potent CD8-specific-CTL responses. The Peptide-35 is present in non-polymorphic a2 domains of 34 SLA-1 alleles, 18 SLA-2 alleles, and 1 SLA-3 allele. These results show that Peptide-35 is a HLA-A2-restricted immunogenic peptide derived from SLA.

Identification of HLA-A2-restricted immunogenic peptides derived from a xenogenic porcine major histocompatibility complex.

Little information is available regarding the precise swine leukocyte antigen (SLA)-derived immunogenic peptides that are presented in the context of human HLA molecules. Here, we identified SLA-derived immunogenic peptides that are presented in association with human HLA-A2 molecule. The SLA-derived peptides that bind to HLA-A*0201, a representative of the A2 supertype, were predicted using a computer-assisted algorithm. The candidate peptides were synthesized, and the stabilities of complexes formed between peptides and HLA-A*0201 were compared using major histocompatibility complex (MHC) stabilization assays. The cytotoxic T lymphocyte (CTL)-inducing activity of the selected peptides was examined in HLA-A*0201-transgenic mice. Among 15 candidate peptides synthesized, two peptides, peptide-35 (YLGPDGLLL) and peptide-43 (TLICHVDSI), were selected to have high affinity and stability with HLA-A*0201. Examination of the CTL-inducing activity of the two peptides in HLA-A*0201-transgenic mice showed that immunization with peptide-35, but not peptide-43, elicited potent CD8-specific CTL responses. The Peptide-35 is present in non-polymorphic α2 domains of 34 SLA-1 alleles, 18 SLA-2 alleles, and 1 SLA-3 allele. This study identifies an immunogenic HLA-A*0201-restricted epitope derived from the SLA, which may be valuable for the development of epitope-specific immunoregulation strategies.

Identification of swine leukocyte antigen-derived peptides inducing epitope-specific CTL responses in HLA-A2 transgenic mice (TRAN3P.882)

Abstract Xenotransplantation of porcine organ is considered a potential solution to the problem of allograft shortage. A xenograft is rejected by cross-primed CD8 cytotoxic T cells as these cells show cytotoxicity against xenografts by recognition of swine leukocyte antigen (SLA). However, the precise swine leukocyte antigen (SLA)-derived immunogenic peptides that are presented in the context of human HLA molecules remain to be elucidated. In the present study, the SLA-derived peptides that bind to HLA-A*0201, a representative of the A2 supertype, were predicted using a computer-assisted algorithm. The candidate peptides were synthesized, and then the stability of peptide/HLA-A*0201 complexes was compared by MHC stabilization assays using HLA-A*0201-expressing Tap knock out T2 cells. Of 15 candidate peptides, two peptides, peptide-35 and peptide-43, were selected to have high affinity and stability with HLA-A*0201. Immunization of HLA- A*0201-transgenic mice with peptide-35 elicited potent CD8 CTL cell responses, while immunization with peptide-43 did not induce noticeable CTL responses. Induction of peptide-35-specific CD8 T cells was also confirmed by intracellular IFN-g staining of CD8 T cells from peptide-35 primed mice. This study has important implications not only for the identification of an immunogenic HLA-A*0201-restricted indirect epitope derived from SLA, but also for the development of epitope-specific immunoregulation strategies.

Structural basis for the differential classification of HLA-A*6802 and HLA-A*6801 into the A2 and A3 supertypes

High polymorphism is one of the most important features of human leukocyte antigen (HLA) alleles, which were initially classified by serotyping but have recently been re-grouped into supertypes according to their peptide presentation properties. Two relatively prevalent HLA alleles HLA-A*6801 and HLA-A*6802, are classified into the same serotype HLA-A68. However, based on their distinct peptide-binding characteristics, HLA-A*6801 is grouped into A3 supertype, whereas HLA-A*6802 belongs to A2 supertype, similar to HLA-A*0201. Thusfar, the structural basis of the different supertype definitions of these serotyping-identical HLA alleles remains largely unknown. Herein, we determined the structures of HLA-A*6801 and HLA-A*6802 presenting three typical A3 and A2 supertype-restricted peptides, respectively. The binding capabilities of these peptides to HLA-A*6801, HLA-A*6802, and HLA-A*0201 were analyzed. These data indicate that the similar conformations of the residues within the F pocket contribute to close-related peptide binding features of HLA-A*6802 and HLA-A*0201. However, the overall structure and the peptide conformation of HLA-A*6802 are more similar to HLA-A*6801 rather than HLA-A*0201 which illuminates the similar serotype grouping of HLA-A*6802 and HLA-A*6801. Our findings are helpful for understanding the divergent peptide presentation and virus-specific CTL responses impacted by MHC micropolymorphisms and also elucidate the molecular basis of HLA supertype definitions.

SY7-7 - New Peptide-Based Cancer Vaccine: Phase I and Early Phase II Clinical Trials for Castration-Resistant Prostate Cancer

ABSTRACT The field of cancer vaccines has moved forward dramatically since 1991, when Boon and his colleagues reported their discovery of the first tumor-associated antigen. Numerous tumor-associated antigens have been identified since that time, and some of them have been clinically tested with encouraging results in immunotherapy against patients with various types of cancer. Indeed, several immunotherapy strategies for prostate cancer, such as single-peptide-based vaccine, multiple-peptide-based vaccine, cell-based vaccine, viral vaccine, antibody-based therapy and their combination with other therapies, have been evaluated. We also reported the clinical outcome along with the safety and immune responses of the personalized peptide vaccination (PPV) alone as well as combined with other therapies. More recently, the US Food and Drug Administration (FDA) recently approved two novel immunotherapy agents, sipuleucel-T and ipilimumab, which showed a survival benefit for patients with metastatic prostate cancer and melanoma, respectively. These cancer vaccines, however, had several limitations, with regard to clinical efficacy, cost, and HLA-restriction. To overcome these limitations, new types of cancer vaccine are under basic and clinical investigation. Tumor cell heterogeneity and heterogeneity of the human immune response in different individuals suggest that polyvalent tumor vaccines will be required for optimal efficacy. We have developed a new cancer vaccine which included 20 different peptides for HLA-A2, -A24, -A3 supertype (A3, A11, A31, or A33) or -A26. Now, we are planning phase I and early phase II clinical trials for patients with castration-resistant prostate cancer. We discuss the current status of the cancer vaccine, particularly mixed peptide based vaccine, and the future direction of therapeutic cancer vaccines.

Human leukocyte antigen class I supertypes and viral control in HIV-1 infected former plasma donors from China

Background The role of human leukocyte antigen (HLA) class I supertypes in controlling human immunodeficiency virus type 1 (HIV-1) infection in Chinese has not been established. The aim of this study is to examine the frequency of HLA-A and HLA-B alleles and supertypes of 222 HIV-1 infected former plasma donors in central China and to investigate their impact on HIV-1 viral control. Methods HLA-A and HLA-B alleles were genotyped with PCR-SSP and sequence-based typing assay to four-digit resolution. The HLA alleles were classified functionally to 4 HLA-A supertypes and 6 HLA-B supertypes according to their shared peptide binding properties. Plasma viral load was determined using the Roche Amplicor ultrasensitive assay which has a lower detection limit of 50 copies HIV-1 RNA per ml. Results HLA-A03 supertypes(A03s) and HLA-B62 supertypes (B62s) were associated with lower viral load (P=0.0206, P=0.0483), whereas HLA- A24 supertypes(A24s) appeared to have an association with higher viral load (P=0.0483). There was ah ighly significant correlation between the genotypic supertypes(GS) and viral load (Kendall’s tau b = 0.180, P=0.000). The median viral load was lower among A*3001(P=0.0139), A*1101(P=0.0096), B*5101(P=0.0025), B*3501(P=0.0091) or B*4601(P=0.001) carriers and higher in A*2301(P=0.0106) carriers. Conclusion

Structural basis of cross-allele presentation by HLA-A*0301 and HLA-A*1101 revealed by two HIV-derived peptide complexes

Human leukocyte antigens (HLA) are initially classified by serotyping but recently can be re-grouped by their peptide-presentation characteristics into supertypes. Both HLA-A*0301 and HLA-A*1101 are grouped into A3 supertype. Although a number of cross-presented T cell epitopes of HLA-A*0301 and HLA-A*1101 have been identified, the molecular mechanisms of cross-presentation remain elusive. Herein, the structures of HLA-A*0301 with two HIV-derived immunodominant T cell epitopes were solved and their characteristics in comparison with HLA-A*1101 presenting the same peptides were analyzed. The comparable structures of HLA-A*0301 and HLA-A*1101 with subtle differences illustrate the common modes of cross-presented peptides and the strict HLA-restriction of T cell receptor (TCR)-recognition.

Selection of conserved HIV-1 vaccine epitopes based on cross-reactivity to feline immunodeficiency virus (53.17)

Abstract Recent reports suggest that CTLs against the conserved epitopes on HIV-1 are required for an effective HIV-1 vaccine, and that the vaccine should induce CTLs to conserved epitopes mimicking those generated by HIV-1+ long-term survivors (LTS). The CTL epitopes needed for vaccine are still unclear. Our current study identifies the evolutionarily-conserved CTL epitopes preserved between HIV-1 and FIV reverse transcriptases (RT) most frequently recognized by HIV+ subjects, including LTS. The IFNγ-ELISpot, CFSE-proliferation, and intracellular staining (ICS) analyses of PBMC upon stimulation with HIV or FIV RT peptide pools or peptides (overlapping 15-mer peptides of whole RT) were used to map the anti-FIV and anti-HIV responses made by HIV+ group (n=14 includes 7 LTS) and HIV- controls (n=5). The HIV+ subjects had HLA alleles from 8 supertypes (mainly A2 supertype) and some with B57 or B27 allele for AIDS nonprogression. Seven of 14 HIV+ subjects (includes 4 LTS) reacted to 4 FIV RT pools and to their HIV counterparts, and none by the controls. Peptides from these pools induced the proliferation of CD3+CD8+ or CD3+CD4+ T cells, which were ICS positive for IFNγ, perforin, granzyme-A, or granzyme-B in various combinations. The existence of evolutionarily-conserved CTL epitopes was determined using HIV/FIV epitope mapping. This approach can select for highly conserved epitopes that are less likely to mutate and as a result can be useful in the development of an HIV-1 vaccine.

Origins and relatedness of human leukocyte antigen class I allele supertypes

Class I human leukocyte antigen (HLA) alleles can be classified into supertypes based on the epitope specificity of their peptide binding grooves. The evolutionary origin of these supertypes has been the topic of prior research and remains an important question because of the increasing interest in HLA supertypes in the contexts of infection and cancer epidemiology and vaccine development. Here I re-examine the origins of HLA class I supertypes using the nucleotide sequences of 88 HLA-A alleles and 117 HLA-B alleles. Phylogenetic trees with ancestral character state reconstruction show that the HLA-A02, A03, and A24 supertypes largely form clades with a single ancestral origin while HLA-A01 shows multiple independent origins all from HLA-A03 ancestors. HLA-B supertypes show multiple origins for the B07, B08, and B27 supertypes, while the B44, B58, and B62 supertypes largely form clades with a single ancestor. Supertypes arising multiple times show different amino acid substitutions in each clade. These findings suggest that convergent evolution has occurred in only a few HLA allele supertypes and may indicate different evolutionary pressures shaping certain supertypes.

HLA Class I Supertypes in Type 1 Diabetic Children in an Urban Children's Hospital

Type 1 diabetes is an autoimmune disorder characterized by progressive destruction of insulin-secreting beta cells of the pancreas, in which CD8(+) T cells play a critical role. The diversity in the HLA alleles expressed among various racial and ethnic groups leads to great variability in antigen presentation and recognition by CD8(+) T cells in the context of MHC class I molecules. To date, studies aimed at identifying disease-relevant antigenic epitopes have focused on using mice transgenic for HLA-A*0201, a common allele, particularly among Caucasians. We present HLA class I typing data from 88 children with type 1 diabetes at the Children's Hospital at Montefiore, where the patient population is ethnically diverse, but largely minority. When categorized into the HLA supertypes A2, A3, B7, and C1, 77% of those studied have alleles belonging to at least one supertype, and of these patients, 65% do not belong to the A2 supertype, which is the supertype represented by the HLA-A*0201 allele. These results support the need for studies using HLA transgenic mice expressing MHC molecules representative of a variety of HLA supertypes, particularly when searching for antigenic epitopes applicable for study among largely urban, minority pediatric populations.

The peptide-binding specificity of HLA-A*3001 demonstrates membership of the HLA-A3 supertype

Human leukocyte antigen class I (HLA-I) molecules are highly polymorphic peptide receptors, which select and present endogenously derived peptide epitopes to CD8+ cytotoxic T cells (CTL). The specificity of the HLA-I system is an important component of the overall specificity of the CTL immune system. Unfortunately, the large and rapidly increasing number of known HLA-I molecules seriously complicates a comprehensive analysis of the specificities of the entire HLA-I system (as of June 2008, the international HLA registry holds >1,650 unique HLA-I protein entries). In an attempt to reduce this complexity, it has been suggested to cluster the different HLA-I molecules into "supertypes" of largely overlapping peptide-binding specificities. Obviously, the HLA supertype concept is only valuable if membership can be assigned with reasonable accuracy. The supertype assignment of HLA-A*3001, a common HLA haplotype in populations of African descent, has variously been assigned to the A1, A3, or A24 supertypes. Using a biochemical HLA-A*3001 binding assay, and a large panel of nonamer peptides and peptide libraries, we here demonstrate that the specificity of HLA-A*3001 most closely resembles that of the HLA-A3 supertype. We discuss approaches to supertype assignment and underscore the importance of experimental verification.

HLA Class I-T Cell Epitopes from trans-Sialidase Proteins Reveal Functionally Distinct Subsets of CD8+ T Cells in Chronic Chagas Disease

BackgroundPreviously, we identified a set of HLA-A020.1-restricted trans-sialidase peptides as targets of CD8+ T cell responses in HLA-A0201+ individuals chronically infected by T. cruzi.Methods and FindingsHerein, we report the identification of peptides encoded by the same trans-sialidase gene family that bind alleles representative of the 6 most common class I HLA-supertypes. Based on a combination of bioinformatic predictions and HLA-supertype considerations, a total of 1001 epitopes predicted to bind to HLA A01, A02, A03, A24, B7 and B44 supertypes was selected. Ninety-six supertype-binder epitopes encoded by multiple trans-sialidase genes were tested for the ability to stimulate a recall CD8+ T cell response in the peripheral blood from subjects with chronic T. cruzi infection regardless the HLA haplotype. An overall hierarchy of antigenicity was apparent, with the A02 supertype peptides being the most frequently recognized in the Chagas disease population followed by the A03 and the A24 supertype epitopes. CD8+ T cell responses to promiscuous epitopes revealed that the CD8+ T cell compartment specific for T. cruzi displays a functional profile with T cells secreting interferon-γ alone as the predominant pattern and very low prevalence of single IL-2-secreting or dual IFN-γ/IL-2 secreting T cells denoting a lack of polyfunctional cytokine responses in chronic T. cruzi infection.ConclusionsThis study identifies a set of T. cruzi peptides that should prove useful for monitoring immune competence and changes in infection and disease status in individuals with chronic Chagas disease.

Improving MHC binding peptide prediction by incorporating binding data of auxiliary MHC molecules

Various computational methods have been proposed to tackle the problem of predicting the peptide binding ability for a specific MHC molecule. These methods are based on known binding peptide sequences. However, current available peptide databases do not have very abundant amounts of examples and are highly redundant. Existing studies show that MHC molecules can be classified into supertypes in terms of peptide-binding specificities. Therefore, we first give a method for reducing the redundancy in a given dataset based on information entropy, then present a novel approach for prediction by learning a predictive model from a dataset of binders for not only the molecule of interest but also for other MHC molecules. We experimented on the HLA-A family with the binding nonamers of A1 supertype (HLA-A*0101, A*2601, A*2902, A*3002), A2 supertype (A*0201, A*0202, A*0203, A*0206, A*6802), A3 supertype (A*0301, A*1101, A*3101, A*3301, A*6801) and A24 supertype (A*2301 and A*2402), whose data were collected from six publicly available peptide databases and two private sources. The results show that our approach significantly improves the prediction accuracy of peptides that bind a specific HLA molecule when we combine binding data of HLA molecules in the same supertype. Our approach can thus be used to help find new binders for MHC molecules.

Motif Inference Reveals Optimal CTL Epitopes Presented by HLA Class I Alleles Highly Prevalent in Southern Africa

HIV-specific CTL play a central role in immune control of HIV. The basis for understanding the success or failure of this immune response requires identification of the specific epitopes targeted by CTL. However, in populations most severely affected by the global epidemic, this fundamental knowledge is hindered by the lack of characterization of many of the HLA class I alleles highly prevalent in such populations. Overall, the peptide-binding motif has been determined for a small minority (9%) of HLA class I alleles, with a strong bias toward those alleles prevalent in Caucasoid populations. These studies therefore set out to define, in a South African Zulu/Xhosa population at the epicenter of the epidemic, the epitopes presented by alleles highly prevalent, but for which the peptide-binding motif had not been characterized. Using a method of motif inference, epitopes presented by four such alleles prevalent in the Zulu/Xhosa population of Durban, South Africa, namely, B*3910, B*4201, B*8101, and Cw*1801, are described. Importantly, this approach may additionally facilitate optimization of epitopes in certain instances where conflicting reports in the literature exist regarding the peptide-binding motif, such as for HLA-A*2902, also highly prevalent in southern African populations. These data indicate that the previously anomalous position of HLA-A*2902 among HLA-A alleles, outside any recognized HLA-A supertype, is artifactual, and the true position of the A*2902 motif overlaps those of the A1 and A24 supertypes.

Human Leukocyte Antigen Concordance and the Transmission Risk via Breast‐Feeding of Human T Cell Lymphotropic Virus Type I

We examined the association between mother-to-child human T cell lymphotropic virus type I (HTLV-I) transmission and human leukocyte antigen (HLA) class I types. In 1989, children born to HTLV-I-infected mothers in Jamaica were enrolled and prospectively evaluated for HTLV-I infection. HLA class I types in mothers and children were determined by DNA-based polymerase chain reaction methods. Associations between HLA class I types and transmission of HTLV-I were analyzed using proportional-hazards regression models adjusted for the duration of breast-feeding. Transmission risk in children still breast-feeding at 12 months was determined using actuarial methods. Of 162 children, 28 (17%) became infected. After Bonferroni's adjustment for multiple comparisons, the transmission risk was not influenced by any specific HLA class type or the A2 supertype. However, compared with children who shared 3 HLA class I types with their mothers (the minimum number possible), the transmission risk increased 1.8-fold with 4 shared types and 3.0-fold with 5 or 6 shared types (Ptrend = .039; 1.75-fold increase for each additional concordant HLA type). This association was independent of maternal HTLV-I proviral level, antibody titer, and household income. We found a significant dose-response relationship between HTLV-I transmission via breast-feeding and mother-child HLA class I type concordance. Immunological interactions between a child's cells and maternal cells may influence the risk of HTLV-I infection by breast-feeding, perhaps because antigens on maternal cells are seen by the child as being "self."

HLA class I-restricted responses to vaccinia recognize a broad array of proteins mainly involved in virulence and viral gene regulation.

We have analyzed by ex vivo ELISPOT the anti-vaccinia cytotoxic T lymphocyte responses of peripheral blood mononuclear cells from humans vaccinated with Dryvax vaccine. More than 6,000 peptides from 258 putative vaccinia ORFs predicted to bind the common molecules of the HLA A1, A2, A3, A24, B7, and B44 supertypes were screened with peripheral blood mononuclear cells of 31 vaccinees. A total of 48 epitopes derived from 35 different vaccinia antigens were identified, some of which (B8R, D1R, D5R, C10L, C19L, C7L, F12, and O1L) were recognized by multiple donors and contain multiple epitopes recognized in the context of different HLA types. The antigens recognized tend to be >100 residues in length and are expressed predominantly in the early phases of infection, although some late antigens were also recognized. Viral genome regulation and virulence factor were recognized most frequently, whereas few structural proteins were immunogenic. Finally, most epitopes were highly conserved among vaccinia virus Western Reserve, variola major and modified vaccinia Ankara, supporting their potential use in vaccine and diagnostic applications.

Classification of A1- and A24-supertype molecules by analysis of their MHC-peptide binding repertoires

At the functional level, the majority of human leukocyte antigen (HLA) class I MHC variants can be classified into about ten different major groups, or supertypes, characterized by overlapping peptide binding motifs and repertoires. Previous studies have detailed the peptide binding specificity of the HLA A2, A3, B7, and B44 supertypes, and predicted, on the basis of MHC pocket structures, known motifs, or the sequence of T cell epitopes, the existence of the HLA A1 and A24 supertypes. Direct experimental validation of the A1 and A24 supertypes, however, has been lacking. In the current study, the peptide-binding repertoires and main anchor specificities of several common HLA A molecules (A*0101, A*2301, A*2402, A*2601, A*2902, and A*3002) predicted to be members of the A1 or A24 supertypes were analyzed and defined using single amino acid substituted peptides and a large peptide library. Based on the present findings, the A1 supertype includes A*0101, A*2601, A*2902, and A*3002, whereas the A24 supertype includes A*2301 and A*2402. Interestingly, A*2902 is associated with a motif and peptide binding repertoire that overlaps significantly with those of all of the A1- and A24-supertype molecules studied, representing-to our knowledge-the first report of significant cross-reactivity among molecules belonging to different supertypes.