Antigenic variation of poliovirus studied by means of monoclonal antibodies.

The natural distribution of poliovirus neutralization epitopes was studied on several field isolates of each of the three serotypes by a neutralization index test for which a panel of homotypic monoclonal antibodies was used. Two categories of neutralization epitopes were detected: strain-specific or variable epitopes, and cross-reacting or common epitopes. The latter tended to be conserved among homotypic viruses. Some of the Sabin-specific neutralization epitopes were found to be mutually exclusive of wild-type epitopes, but coexistence of Sabin-specific and wild-type epitopes was found in other cases. During virus excretion by infants fed type 1 Sabin vaccine, the Sabin-specific neutralization epitope was lost, and sometimes the original epitope motif of the parental wild (Mahoney) virus was recovered. Epitope variation was also expressed by loss of epitope function in virus neutralization without modification of antigenic conformation.