A single CTL clone can recognize a naturally processed HIV-1 epitope presented by two different HLA class I molecules

Although it is known that a single peptide can be recognized by CTL restric ted to two MHC class I alleles, there is no direct evidence for presentatio n of a single peptide by two MHC class I molecules. Furthermore, it is uncl ear whether such peptides are presented to the same T cell or to different T cells. Our previous study suggested that CTL recognition of the human imm unodeficiency virus-1 (HIV-1) Pot HIV-B35-SF2-24 epitope (IPLTEEAEL) occurs via both HLA-B35 and HLA-B51 restriction. Here we provide the first direct evidence that a single CTL clone can recognize this peptide presented by b oth HLA-B35 and HLA-B51. Furthermore, we directly purified this peptide elu ted from both HLA-B*3501 and HLA-B*5101 molecules isolated from target cell s infected with HIV-1 recombinant vaccinia virus. These results demonstrate that HIV-B35-SF2-24 is a naturally processed peptide which is presented by both HLA-B*3501 and HLA-B*5101. TCR analysis of one CTL clone suggested th at it is a single clone. B*3501-SF2-24-tetrameric complexes inhibited both HLA-B*3501-and HLA-B*5101-restricted recognition of this clone, suggesting that the TCR of this clone cross-recognize the structure of both HLA class I-peptide complexes.