Antigenic relationships among some animal rotaviruses: virus neutralization in vitro and cross-protection in piglets.

The serotype, RNA electropherotype, and cross-protection properties of rotaviruses isolated from canine, simian, porcine, and human species were compared. The bovine strain B:USA:78:1A and the canine strain C:USA:81:2 were adapted to cell culture and cloned in this study. The other viruses, i.e., simian strain S:USA:79:2, porcine Ohio State University strain P:USA:77:1, and human strain WA, were already cell culture adapted, although they were further cloned for this work. The serum neutralization test was used to classify the viruses into serotype groups. Viruses which exhibited a difference of 20-fold or greater in neutralization titer were separated into different serotype groups. In this study, four major serotype groups were found, and these groups were represented by bovine, human, porcine, and canine-simian strains. From cross-protection studies, these serotype groups were found to be significantly different. With the exception of the porcine strain, none of the viruses used as vaccines protected gnotobiotic piglets from challenge with the virulent porcine Ohio State University strain of rotavirus. Furthermore, the canine virus protected piglets from challenge with the simian virus. The RNA electropherotype confirmed that the canine and simian strains were different in eight RNA segments and eliminated the possibility that they were the same virus. From these findings, it was concluded that only viruses belonging to the same serotype group can be expected to confer cross-protection, and thus, vaccines should be made with the serotypes to which the animal is likely to be exposed.