Neutralization Epitopes on Poliovirus Type 3 Particles: an Analysis Using Monoclonal Antibodies

Monoclonal antibodies to poliovirus type 3 secreted by 51 hybridoma cell clones have been characterized in terms of (i) virus-neutralizing properties, (ii) reactivity in antigen-blocking tests with infectious, 155S ('D' antigen) and empty 80S ('C' antigen) poliovirus particles and (iii) reactivity in immunoblot tests with the isolated protein components of the poliovirus capsid. The antibodies could be separated into three groups on the basis of their reactivities with 'D' and 'C' antigens. All antibodies that reacted with both 'D' and 'C' antigen had potent neutralizing activity. Only a proportion of antibodies that reacted uniquely with 'D' antigen possessed neutralizing activity. Unexpectedly, one of 24 'C' antigen-specific antibodies inhibited virus growth. None of the antibodies that possessed virus-neutralizing activity reacted with isolated poliovirus capsid proteins, although the majority of these have been shown in previous studies to be specific for VP1 on intact virus particles. These findings suggest that antigenic determinants involved in virus neutralization do not survive the denaturing conditions required for the isolation of poliovirus capsid proteins and consequently are likely to be specified by the structural conformation of VP1 rather than by amino acid sequence alone. However, several of the antibodies which bound uniquely to 'C' antigen reacted in immunoblot tests, five with VP1 and one with VP3. Some of these antibodies also possessed heterotypic reactivity with the corresponding capsid proteins separated from other poliovirus types.