Type-specific antigenicity of avian reoviruses.

The type-specificity of the neutralizing activity in chicken antiserum to avian reoviruses was affected by the method of antiserum production. The neutralizing activity produced in response to virus infection had higher type-specificity than that produced by immunization with inactivated virus emulsified in adjuvant. By using reassortant viruses the induction of type-specific neutralizing activity was shown to be associated with the sigma C (sigmaC) virion protein. Antigenic classification of virus strains based on immunoprecipitation of the sigmaC protein by chicken antiserum was attempted and the results were similar to those obtained by reciprocal serum neutralization tests. One-way immunoprecipitation of the sigmaC protein by antisera to some heterologous viruses, similar to that reported in reciprocal neutralization tests, made it difficult to assign individual viruses to serogroups and showed that the type-specificity of the sigmaC protein was not absolute. The neutralization activity of monoclonal antibodies to the sigmaC protein of the RAM1 strain of avian reovirus suggested there were separate type- and group-specific antigenic domains on the sigmaC protein, and that the group-specific domains may be associated with the induction of antibody against heterologous viruses.