Mutations within cytotoxic T lymphocyte (CTL) epitopes impair T cell recognition, but escape mutations arising in flanking regions that alter antigen processing have not been defined in natural human infections. In human histocompatibility leukocyte antigen (HLA)-B57+ HIV-infected persons, immune selection pressure leads to a mutation from alanine to proline at Gag residue 146 immediately preceding the NH2 terminus of a dominant HLA-B57-restricted epitope, ISPRTLNAW. Although N-extended wild-type or mutant peptides remained well-recognized, mutant virus-infected CD4 T cells failed to be recognized by the same CTL clones. The A146P mutation prevented NH2-terminal trimming of the optimal epitope by the endoplasmic reticulum aminopeptidase I. These results demonstrate that allele-associated sequence variation within the flanking region of CTL epitopes can alter antigen processing. Identifying such mutations is of major relevance in the construction of vaccine sequences.

Original publication





J Exp Med

Publication Date





905 - 915


Alleles, Amino Acid Sequence, Antigen Presentation, Base Sequence, Clone Cells, DNA, Viral, Epitopes, Gene Products, gag, Genetic Variation, HIV Antigens, HIV Infections, HIV-1, HLA-B Antigens, Humans, Molecular Sequence Data, Mutation, Sequence Homology, Amino Acid, T-Lymphocytes, Cytotoxic