IDENTIFICATION OF THE PEPTIDE BINDING MOTIF FOR HLA-B44, ONE OF THE MOST COMMON HLA-B ALLELES IN THE CAUCASIAN POPULATION

Most peptides that bind to a particular MHC class I molecule share ami no acid residues that are thought to physically ''anchor'' the peptide to polymorphic pockets within the class I binding site. Sequence anal ysis of endogenous peptides bound to HLA-B44 revealed two potential do minant anchor residues: Glu at P2 and Tyr, or occasionally Phe, at P9. In vitro assembly assays employing synthetic peptides and recombinant HLA-B44 produced by Escherichia coli revealed that an acidic amino ac id at P2 was necessary for promoting stable peptide binding to HLA-B44 . Surprisingly, although Tyr was almost exclusively found at p9 of the endogenous peptide sequences, a wide variety of amino acid residues s uch as Leu, Ala, Arg, Lys, His, and Phe could be tolerated at this pos ition. Using this information, we identified antigenic peptides from t he influenza virus components nonstructural protein I and nucleoprotei n that are presented by HLA-B44 to antiinfluenza type A cytotoxic T ly mphocytes. In addition, cytotoxic T lymphocytes induced by these antig enic peptides were shown to be capable of recognizing endogenously pro cessed peptides from influenza-infected cells, indicating a potential use for these peptides in vaccine development. Finally, molecular mode ls were created to investigate the possible ways in which the anchor r esidues might function to stabilize the binding of peptides to HLA-B44 , and these models indicate that the acidic residue at P2 most likely interacts primarily with Lys 45 of the HLA-B44 heavy chain and makes a dditional contacts with Ser 67 and Tyr 9.