Antigenic Analysis of Avian Rotavirus VP6 Using Monoclonal Antibodies

Monoclonal antibodies (MAbs) were prepared to analyze antigens on the major inner capsid protein, VP6 of avian group A rotavirus. Based on the results of a competitive binding assay using 15 MAbs directed against VP6 of the PO-13 rotavirus strain, isolated from a pigeon in Japan, it was found that VP6 of avian rotavirus possesses at least four spatially distinct antigenic sites. Two antigenic sites (I and II) were topologically distinct from the other two (III and IV), which were in close proximity. From the reaction of MAbs in indirect immunofluorescent antibody tests to a series of known rotaviruses, epitopes representing common antigens of all group A rotavirus including avian rotavirus were localized in sites II and III. One epitope in site IV appeared to have a subgroup antigenic specificity that reacted only with rotaviruses belonging to subgroup I. Interestingly, avian rotaviruses isolated from turkeys and chickens in Northern Ireland also reacted only with these subgroup I specific MAbs, but not with subgroup II specific MAb. This indicates that avian rotavirus has subgroup I specific antigen, which is antigenically similar to that of other mammalian rotavirus strains.