Relationship between poliovirus neutralization and aggregation.

The interaction of mono- and polyclonal neutralizing antibodies with poliovirus was studied. In all cases, neutralization was due to antibody-mediated virus aggregation, and the unpolymerized virions accounted for the residual infectivity. The effect of papain on previously neutralized virus was to deaggregate the virus to fully infective single virions. With some antibodies, the amount of aggregated virus regressed in the region of greatest antibody excess, even though the virus remained fully neutralized. Under these conditions, noninfective, unaggregated immune complexes were formed. A mutant resistant to one of the monoclonal antibodies was selected. The mutant virions were still bound but no longer aggregated or neutralized by the selecting antibodies.