title: Refocusing of B-cell responses following a single amino acid substitution in an antigen.
abstract: Intranasal immunization of BALB/c strain mice was carried out using baculovirus-derived human chorionic gonadotrophin (hCG) beta-chain, together with Escherichia coli heat-labile enterotoxin. Gonadotrophin-reactive immunoglobulin A (IgA) was induced in a remote mucosal site, the lung, in addition to a systemic IgG response. The extensive sequence homology with luteinizing hormone (LH) results in the production of LH cross-reactive antibodies when holo-hCG is used as an immunogen. In contrast to wild-type hCGbeta, a mutated hCGbeta-chain containing an arginine to glutamic acid substitution at position 68 did not induce the production of antibodies which cross-react with LH. Furthermore, the epitopes utilized in the B-cell response to the mutated hCGbeta shifted away from the immunodominant region of the parent wild-type molecule towards epitopes within the normally weakly immunogenic C terminus. This shift in epitope usage was also seen following intramuscular immunization of rabbits. Thus, a single amino acid change, which does not disrupt the overall structure of the molecule, refocuses the immune response away from a disadvantageous cross-reactive epitope region and towards a normally weakly immunogenic but antigen-unique area. Similar mutational strategies for epitope-refocusing may be applicable to other vaccine candidate molecules.
authors: Department of Immunology and Molecular Pathology, The Windeyer Institute for Medical Sciences, University College London, UK.
authors: M D
authors: MD
authors: Chiesa
authors: P M
authors: PM
authors: Martensen
authors: C
authors: C
authors: Simmons
authors: N
authors: N
authors: Porakishvili
authors: J
authors: J
authors: Justesen
authors: G
authors: G
authors: Dougan
authors: I M
authors: IM
authors: Roitt
authors: P J
authors: PJ
authors: Delves
authors: T
authors: T
authors: Lund
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D000941:Antigens / Q000737:chemistry / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D016367:Baculoviridae / Q000235:genetics; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D003429:Cross Reactions; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D005260:Female; D018928:Immunity, Mucosal; D007114:Immunization / Q000379:methods; D007071:Immunoglobulin A, Secretory / Q000096:biosynthesis; D007074:Immunoglobulin G / Q000096:biosynthesis; D008168:Lung / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids; D017354:Point Mutation; D011817:Rabbits; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D000941:Antigens; D018997:Chorionic Gonadotropin, beta Subunit, Human; D018985:Epitopes, B-Lymphocyte; D007071:Immunoglobulin A, Secretory; D007074:Immunoglobulin G; D011994:Recombinant Proteins