An equine rotavirus strain FI-14 was shown to belong to serotype 3 by neutralization assay. In addition, it was found to react with both subgroup I and subgroup II monoclonal antibodies by ELISA, thus representing the first rotavirus strain to have both subgroup specificities. Using hybridoma technology, we successfully produced monoclonal antibodies directed against the major inner capsid protein VP6 (the sixth gene product) of FI-14 virus. These monoclonal antibodies reacted specifically with either subgroup I or subgroup II rotaviruses thus demonstrating that the VP6 of FI-14 virus has both subgroup I and subgroup II-specific epitopes. Four additional monoclones directed to the VP-6 of FI-14 demonstrated distinct reactivities by ELISA with a panel of 22 rotavirus strains derived from 11 different animal and avian species. Thus, at least six distinct epitopes were shown to exist on VP6 of FI-14 virus. When analyzed by radioimmunoprecipitation, the molecular weight of the FI-14 virus VP6 (subgroups I and II) was found to be larger (approximately 45K) than the VP6 (approximately 42K) of rhesus rotavirus MMU18006 (subgroup I) or the VP6 of human rotavirus Wa (subgroup II). By RNA-RNA hybridization analysis, the FI-14 virus was shown not to share significant homology with any of the four known human rotavirus serotypes.
