Different immunodominance of HIV-1-specific CTL epitopes among three subtypes of HLA-A∗26 associated with slow progression to AIDS

It is speculated that HLA-A∗26-restricted HIV-1-specific CTLs can control HIV-1, since HLA-A∗26 is associated with a slow progression to AIDS. In three major HLA-A∗26 subtypes, HLA-A∗2601-restricted, and HLA-A∗2603-restricted HIV-1 epitopes have been identified, but HLA-A∗2602-restricted ones have not. We here identified HLA-A∗2602-restricted HIV-1 epitopes by using reverse immunogenetics and compared the immunodominance of the epitopes among the three subtypes. Out of 110 HIV-1 peptides carrying HLA-A∗26 anchor residues, only the Gag169-177 peptide, which had been previously identified as an HLA-A∗2601- and HLA-A∗2603-restricted immunodominant epitope, induced Gag169-177-specific CD8+ T cells from only two of six HLA-A∗2602+ HIV-1-infected individuals. No difference in affinity of this epitope peptide was found among these three HLA-A∗26 subtypes, indicating that Gag169-177 was effectively presented by HLA-A∗2602 but recognized as a subdominant epitope in HIV-1-infected HLA-A∗2602+ individuals. These findings indicate different immunodominance of Gag169-177 epitope among 3 HLA-A∗26 subtypes.