Identification and characterization of a C(K/R)TC motif as a common epitope present in all subtypes of hepatitis B surface antigen.
The a determinant of hepatitis B surface antigen (HBsAg) is the most critical determinant for both diagnosis and immunoprophylaxis of the hepatitis B virus. We have used synthetic peptides and an anti-a mAb to identify a peptide sequence corresponding to amino acid residues 117 to 128 of HBsAg as an antigenic epitope contributing to the a determinant. Compared to the native protein HBsAg, the cyclic form of the peptide (aa 117-128) is only 20-fold less effective, whereas the linear form of the peptide is 160-fold less effective in the inhibition of mAb binding to HBsAg. Based on these results, we have postulated a previously unidentified disulfide bond between residue Cysl21 and Cysl24. Individual substitution of amino acids in the peptide (aa 117-128) with alanine identified three residues Cys121, Thr123, and Cys124 as the most critical residues for mAb recognition. Substitution of alanine for any one of the three residues caused a substantial loss in binding free energy (greater than 4.5 kcal/mol). Sequence analysis indicated that the C(K/R)TC motif is highly conserved among 100 subtypes and mutants of HBsAg isolates. Collectively, these results show that the cyclic C(K/R)TC motif is an essential part of the a determinant of HBsAg. Synthetic peptides containing the C(K/R)TC motif are potentially useful as alternative hepatitis B vaccines and as diagnostic reagents for the detection of the hepatitis B virus.
Qiu
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Department of Peptide Engineering, Abbott Laboratories, Abbott Park, IL 60064, USA.
Schroeder
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Bridon
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000915:Antibody Affinity; D001666:Binding Sites, Antibody; D006510:Hepatitis B Antibodies / Q000737:chemistry; D006514:Hepatitis B Surface Antigens / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D006515:Hepatitis B virus / Q000235:genetics; D006801:Humans; D016056:Immunodominant Epitopes / Q000737:chemistry* / Q000302:isolation & purification*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology*; D016415:Sequence Alignment; D012703:Serotyping
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens; D016056:Immunodominant Epitopes; D010446:Peptide Fragments