title: Characterization of T cell epitopes restricted by HLA-DP9 in streptococcal M12 protein.
abstract: Interaction of the HLA-DP9 (DPA1*0201/DPB1*0901) molecule and M protein of serotype 12 (SS95/12) streptococci, a main component of the streptococcal cell wall Ag, has been investigated to decipher peptide-binding capacity and T cell activation in the context of the HLA-DP molecule. Seven antigenic peptides (amino acids 19-25) restricted by the HLA-DP9 molecule were identified in M12 protein, using M12 protein- or peptide-specific T cell lines from naturally exposed individuals. The binding affinity of each peptide to the HLA-DP9 molecule was measured by fluorescence intensity of biotinylated peptides bound to L cell transfectants expressing HLA-DP9, followed by treatment with avidin-fluorescence. Binding of biotinylated peptides to the HLA-DP9 molecule was inhibited by an excess amount of corresponding nonbiotinylated peptides and other nonbiotinylated peptides, indicating that the peptides were bound to the HLA-DP9 molecule at a single binding site. Seven synthetic peptides containing the T cell epitopes restricted by the HLA-DP9 molecule had high binding affinity to the HLA-DP9 molecule. Comparison of the amino acid sequences of truncated analogues that could bind to the HLA-DP9 molecule and/or activate T cells suggested an HLA-DP9-specific binding motif, composed of a positively charged residue (R or K) at position 1, a hydrophobic residue (A, G, or L) at position 6, and another hydrophobic residue (L or V) at position 9. Analysis of single amino acid-substituted analogues suggested that the positively charged amino acid in the motif served as a key anchor residue for binding to the HLA-DP9 molecule, which differs from the binding motif to the HLA-DR molecules.
authors.affiliation: Department of Genetics, Kyushu University, Fukuoka, Japan.
authors.forename: R P
authors.initials: RP
authors.lastname: Dong
authors.forename: N
authors.initials: N
authors.lastname: Kamikawaji
authors.forename: N
authors.initials: N
authors.lastname: Toida
authors.forename: Y
authors.initials: Y
authors.lastname: Fujita
authors.forename: A
authors.initials: A
authors.lastname: Kimura
authors.forename: T
authors.initials: T
authors.lastname: Sasazuki
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000276:immunology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D001667:Binding, Competitive / Q000276:immunology; D002352:Carrier Proteins; D002460:Cell Line; D000939:Epitopes / Q000276:immunology*; D006682:HLA-DP Antigens / Q000235:genetics*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D000939:Epitopes; D006682:HLA-DP Antigens; D010446:Peptide Fragments; C014689:streptococcal M protein