Promiscuous and specific binding of HIV peptides to HLA-DR1 and DR103. Impact on T-cell repertoire of nonimmunized individuals.

The binding of immunogenic peptides to DR molecules is influenced by residues that point into the peptide-binding groove. The T-cell response toward a peptide complexed to an MHC molecule depends on the presence of a sufficient number of T cells reactive with peptide-MHC complex on the surface of APCs. From 96 overlapping HIV peptides, we have selected 11 that show a significant binding to either DR1, DR103, or both. These two DR molecules are identical except for three amino acids at positions 67, 70, and 71 on the beta chain. Peptide-specific T-cell lines and clones were generated with cells from nonimmunized donors homozygous for DR1 or DR103 by using either individual peptides or peptide pools for the in vitro priming. Three of the peptides induced T-cell-specific proliferative response in both individuals, and these peptides were not among those with highest affinity. Most of the peptides induced strong responses against autologous APCs. This might reflect cross-reactivity between HIV and self-peptides. Definition of peptides that both show promiscuous binding to DR and elicit a strong T-cell response is important for design of efficient synthetic vaccines.