title: Epitopes associated with a synthetic hepatitis B surface antigen peptide.
abstract: A synthetic peptide (SP1), corresponding to the amino acid residues 122 through 137 of the major polypeptide derived from hepatitis B surface antigen (HBsAg), subtype ayw, was analyzed for the presence of the major epitopes of HBsAg. Both a cyclic form, produced by introduction of an intrachain disulfide bond, and a linear form of the peptide were characterized. A panel of monoclonal antibodies with defined specificity for the cross-reactive group a antigenic determinant(s) and for the y and w subtype specificities was used for this analysis. The cyclic, but not the linear, form of SP1 reacted with five of 14 anti-a monoclonal antibodies, demonstrating that the cyclic peptide contains a conformation-dependent a epitope. Only one anti-a antibody was found to react with both cyclic and linear forms of SP1. Because SP1 failed to react with the remaining 8 anti-a monoclonal antibodies, it was concluded that the a antigenic reactivity associated with HBsAg contains an additional epitope(s) unrelated to that expressed on SP1. Both cyclic and linear SP1 reacted with three of three anti-y monoclonal antibodies, indicating that a sequential y epitope is also present on SP1; no w reactivity was detected. Analysis of the idiotypes associated with the monoclonal antibodies showed those that combined with cyclic SP1 also inhibited the binding of a common human anti-HBs (CHBs) idiotype with its rabbit anti-idiotype serum, whereas a monoclonal antibody that did not react with the cyclic SP1 epitope failed to inhibit the CHBs idiotype-anti-idiotype reaction. Thus, the conformational a epitope present on cyclic SP1 appears to contain the predominant epitope recognized by humans in response to a natural HBV infection.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001667:Binding, Competitive; D000939:Epitopes / Q000032:analysis* / Q000276:immunology; D006510:Hepatitis B Antibodies / Q000032:analysis*; D006514:Hepatitis B Surface Antigens / Q000032:analysis*; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D051379:Mice; D010455:Peptides / Q000276:immunology*; D011487:Protein Conformation
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens; D007130:Immunoglobulin Idiotypes; D010455:Peptides; C021759:(T,G)-A-L