Conditional ligands for Asian HLA variants facilitate the definition of CD8⁺T‐cell responses in acute and chronic viral diseases

Abstract

Conditional ligands have enabled the high-throughput production of human leukocyte antigen (HLA) libraries that present defined peptides. Immunomonitoring platforms typically concentrate on restriction elements associated with European ancestry, and such tools are scarce for Asian HLA variants. We report 30 novel irradiation-sensitive ligands, specifically targeting South East Asian populations, which provide 93, 63, and 79% coverage for HLA-A, -B, and -C, respectively. Unique ligands for all 16 HLA types were constructed to provide the desired soluble HLA product in sufficient yield. Peptide exchange was accomplished for all variants as demonstrated by an ELISA-based MHC stability assay. HLA tetramers with redirected specificity could detect antigen-specific CD8+ T-cell responses against human cytomegalovirus, hepatitis B (HBV), dengue virus (DENV), and Epstein-Barr virus (EBV) infections. The potential of this population-centric HLA library was demonstrated with the characterization of seven novel T-cell epitopes from severe acute respiratory syndrome coronavirus, HBV, and DENV. Posthoc analysis revealed that the majority of responses would be more readily identified by our unbiased discovery approach than through the application of state-of-the-art epitope prediction. This flow cytometry-based technology therefore holds considerable promise for monitoring clinically relevant antigen-specific T-cell responses in populations of distinct ethnicity.

In silicodesign of a DNA-based HIV-1 multi-epitope vaccine for Chinese populations

“…Second, Th responses are a part of protective immunity against HIV-1 infection. 36,37 However, we experienced difficulty in finding such Th epitopes, as most published work on epitope identification focused on epitopes restricted to European and American populations, 38 with little information being available about epitopes that match Chinese predominant MHC-II alleles. We finally discovered a 36-aa-long peptide located in the V2 region, a T-cell epitope-rich region, and predicted that it would contain several pan-DR epitopes.…”

The Immunodominant Influenza A Virus M158–66Cytotoxic T Lymphocyte Epitope Exhibits Degenerate Class I Major Histocompatibility Complex Restriction in Humans

“…In addition, we also detected CTL responses in all HLA-C*08-positive individuals, suggesting that the immunoprevalence of HLA-C*08-restricted GILGFVFTL responses in the human population may be comparable to that of HLA-A*02-restricted responses. Interestingly, among HLA-C molecules, HLA-C*08:01 appears to have broad peptide binding capacity, as shown in reports of binding to hepatitis B virus (HBV) envelope residues 171 to 180 (36,37) and CMV pp65 residues 198 to 206 (12). Whether the CTLs recognizing an identical epitope presented by unrelated HLA allelic variants were derived from the same CTL clones, resulting in T cell cross-reactivity, remains to be elucidated.…”

HLA Micropolymorphisms Strongly Affect Peptide–MHC Multimer–Based Monitoring of Antigen-Specific CD8+ T Cell Responses

“…In prior work, UV-induced peptide exchange was developed for HLA-A*02:01 (24), HLA-A*02:06, HLA-A*02:07, and HLA-A*02:11 (7). Based on the observation that the (predicted) peptide-binding motifs of these HLA-A*02 subtypes are highly similar (23), the previously developed conditional ligands were used to refold the HLA*A-02:02, HLA-A*02:05, HLA-A*02:71, and HLA-A*02:77 alleles.…”

“…Thus, no other alleles were expressed that could also form the restriction element of the epitopes concerned. Subsequently, pMHC multimers of all eight HLA-A*02 subtypes were produced for each of the 10 different Ags by UV-mediated peptide exchange (7,24). The set of CD8 + T cell clones was then stained with all pMHC multimer subtypes, loaded either with cognate peptide or with a control peptide.…”

“…To illustrate this bias, .65% of melanoma-associated Ags described in literature are restricted by the HLA-A*02 allele (6), even though this allele is only one of the many HLA-A alleles that are present. Notably, in non-Caucasian populations, the HLA-A*02:01 subtype (by far the most frequent subtype in Caucasian populations) is present in only a minor fraction of HLA-A*02 + individuals (7). The variation between the subtypes of specific HLA alleles (traditionally referred to as four-digit subtypes) maps to a small number of sequence differences within the a1 or a2 domains of the MHC H chain, which together form the peptide-binding groove.…”