Antigenic sites of poliovirus type 3 eliciting IgA monoclonal antibodies in orally immunized mice

A panel of neutralizing IgA monoclonal antibodies was produced from mice orally inoculated with poliovirus type 3 Sabin and cholera toxin as adjuvant. Low levels of neutralizing antibodies were elicited in mice after several boosts, but only in the presence of cholera toxin. Characterization of IgA MAbs by neutralization-escape virus mutants showed that all but one neutralizing MAbs against type 3 poliovirus were directed to antigenic site N-AgIII, which was previously found by us to be the major target of mucosal immune response to Sabin 1 in the mouse. Our data indicate that residue 236 of VP3, not previously reported, is also involved in forming site N-AgIII in addition to formerly described VP3 (aa 58-59) and VP1 (aa 286-290) residues. Unlike poliovirus type 1 IgA MAbs, all IgA MAbs herein described neutralized the wild-type parental poliovirus.