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.