ENDOGENOUS PEPTIDES WITH DISTINCT AMINO-ACID ANCHOR RESIDUE MOTIFS BIND TO HLA-A1 AND HLA-B8

Distinct amino acid (aa) residue motifs for peptides binding to HLA-A1 and HLA-B8 were identified by sequence analyses of reversed-phase HPL C fractions containing endogenous peptides derived from these HLA mole cules. Fifteen different primary sequences were determined for HLA-A1- associated peptides, 12 of which were nine aa in length. Common featur es among these peptide sequences were Tyr at the COOH-terminus, a nega tively charged aa (usually Glu) at position 3 (P3), and Pro at P4. Twe nty-seven different primary sequence assignments were made for HLA-B8- associated peptides, most of which were eight aa in length. Lys, and i n a few cases Arg, predominated at P3 and P5; Leu and Pro predominated at P2, and Leu was the preferred COOH-terminal residue. Unlike all ot her human class I molecules whose peptide-binding properties have been studied, both HLA-A1 and HLA-B8 endogenous peptide sequences have a d ominant anchor residue at P3, and these aa are opposite in charge to t he aa at position 156 of the peptide-binding site. Synthetic peptides corresponding to endogenous peptide sequences bound to their respectiv e HLA molecules in vitro, indicating that they derive from peptides bo und to HLA and not from copurifying contaminants. Eight of the HLA-A1 and HLA-B8 endogenous peptide sequences matched intracellularly expres sed proteins found in protein sequence data bases. The HLA-A1 peptide- binding motif was then used to identify potential antigenic peptides f rom influenza A viral proteins that bound to HLA-A1 in vitro.