Location of type-specific antigens in calf rotaviruses.

Rotavirus antisera with and without neutralizing activity to calf rotavirus were compared for their ability to agglutinate calf rotavirus particles with and without an outer capsid layer. Particles without the outer capsid layer were agglutinated by antisera with immunofluorescent antibody activity and by antisera with immunofluorescent antibody and neutralizing activity. Particles with the outer capsid layer were agglutinated only by antisera with neutralizing activity. The neutralization test appears to be type specific, and it was concluded that type-specific antigens are associated with the outer capsid layer of rotaviruses. Since particles with the outer capsid layer were not agglutinated by antisera lacking neutralizing activity but possessing immunofluorescent antibody activity, it was concluded that in intact particles the group-specific antigen is masked by the outer capsid layer.