Comparative Investigation of Monoclonal and Polyclonal Antibodies Directed against Strain-Specific and Common Antigenic Sites on Influenza H1N1 Virus Hemagglutinin

Abstract

Antibodies directed against strain-specific and common antigenic sites of H1N1 influenza virus hemagglutinin were tested comparatively, using monoclonal antibodies raised against strain A/Brazil/11/78 and polyclonal antibodies directed against strains A/Brazil/11/78, A/USSR/97/77, A/PR/301/54, and A/FM/1/47. The patterns of competition between antibodies for adsorption onto homologous virus indicated that the monoclonals comprised antibodies directed to each of the two strain-specific (Sa and Sb) and common antigenic sites (Ca and Cb) of virus hemagglutinin. Polyclonal strain-specific antibodies (SSA) yielded the competition patterns of mixtures of anti-Sa and anti-Sb antibodies and polyclonal common antigen antibodies (CAA) yielded those of mixtures of antibodies directed against sites Ca and Cb, indicating that the polyclonal preparations comprised a similar repertoire of antibodies, as represented by the panel of monoclonals. This conclusion was confirmed by determining, by means of equilibrium filtration, the number of epitopes per homologous virion(s) recognized by antibody preparations and their mixtures. Polyclonal SSA and CAA gave s values not significantly different from those of mixtures of the corresponding monoclonal antibodies. The strains tested were found to possess equivalent numbers of strain-specific and common epitopes per virion. The competition between antibodies was further examined in terms of the additiveness of s values they recognize in simultaneous reactions. No competition was observed for the monoclonal antibody pairs anti-Sa/anti-Ca, anti-Sa/anti-Cb and anti-Sb/anti-Cb, indicating that these antibodies combined with nonoverlapping epitopes. Polyclonal SSA and CAA yielded partial competition. The equilibrium constants (K) of comparable SSA and CAA were within the same range, and SSA and CAA did not influence their binding avidity when allowed to react simultaneously with homologous virus.