title: Neutralization escape mutants define a dominant immunogenic neutralization site on hepatitis A virus.
abstract: Hepatitis A virus is an hepatotrophic human picornavirus which demonstrates little antigenic variability. To topologically map immunogenic sites on hepatitis A virus which elicit neutralizing antibodies, eight neutralizing monoclonal antibodies were evaluated in competition immunoassays employing radiolabeled monoclonal antibodies and HM-175 virus. Whereas two antibodies (K3-4C8 and K3-2F2) bound to intimately overlapping epitopes, the epitope bound by a third antibody (B5-B3) was distinctly different as evidenced by a lack of competition between antibodies for binding to the virus. The other five antibodies variably blocked the binding of both K3-4C8-K3-2F2 and B5-B3, suggesting that these epitopes are closely spaced and perhaps part of a single neutralization immunogenic site. Several combinations of monoclonal antibodies blocked the binding of polyclonal human convalescent antibody by greater than 96%, indicating that the neutralization epitopes bound by these antibodies are immunodominant in humans. Spontaneously arising HM-175 mutants were selected for resistance to monoclonal antibody-mediated neutralization. Fourteen clonally isolated mutants demonstrated substantial resistance to multiple monoclonal antibodies, including K3-4C8-K3-2F2 and B5-B3. In addition, 13 mutants demonstrated a 10-fold or greater reduction in neutraliztion mediated by polyclonal human antibody. Neutralization resistance was associated with reduced antibody binding. These results suggest that hepatitis A virus may differ from poliovirus in possessing a single, dominant neutralization immunogenic site and therefore may be a better candidate for synthetic peptide or antiidiotype vaccine development.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D002522:Chlorocebus aethiops; D000939:Epitopes / Q000032:analysis; D005799:Genes, Dominant; D005814:Genes, Viral; D006507:Hepatovirus / Q000235:genetics* / Q000276:immunology; D007668:Kidney; D009154:Mutation; D009500:Neutralization Tests
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes