Refocusing of B-cell responses following a single amino acid substitution in an antigen

Immunology. 2001 Jun;103(2):172-8. doi: 10.1046/j.1365-2567.2001.01242.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Intranasal
  • Animals
  • Antigens / chemistry
  • Antigens / immunology
  • B-Lymphocytes / immunology*
  • Baculoviridae / genetics
  • Chorionic Gonadotropin, beta Subunit, Human / chemistry
  • Chorionic Gonadotropin, beta Subunit, Human / genetics
  • Chorionic Gonadotropin, beta Subunit, Human / immunology*
  • Cross Reactions
  • Epitopes, B-Lymphocyte / immunology*
  • Female
  • Immunity, Mucosal
  • Immunization / methods
  • Immunoglobulin A, Secretory / biosynthesis
  • Immunoglobulin G / biosynthesis
  • Lung / immunology
  • Mice
  • Mice, Inbred BALB C
  • Plasmids
  • Point Mutation
  • Rabbits
  • Recombinant Proteins / immunology

Substances

  • Antigens
  • Chorionic Gonadotropin, beta Subunit, Human
  • Epitopes, B-Lymphocyte
  • Immunoglobulin A, Secretory
  • Immunoglobulin G
  • Recombinant Proteins