Antigenic diversity of infectious bursal disease viruses.

Statistically significant antigenic differences were detected among serotype I infectious bursal disease viruses (IBDV) using the virus-neutralization test. Eight serotype I commercial vaccine strains, five serotype I field strains, and two serotype II field strains were tested. Hyperimmune guinea pig antisera against heterologous and homologous IBDV strains were used in cross-neutralization tests. Relatedness values were calculated from geometric mean antibody titers based on a minimum of three tests. Six subtypes were distinguished among the 13 serotype I strains tested.