Purification of the IDIR strain of group B rotavirus and identification of viral structural proteins

A purification scheme was developed that allowed for the partial purification of complete, double-shelled particles of the infectious diarrhea of infant rats (IDIR) virus, a group B rotavirus (GBR). Structural proteins from the isolated, complete viral particles were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and evaluated by silver staining and by immunoblotting using antisera obtained from rats that had recovered from IDIR virus infection. Analysis of the stained gels and immunoblots demonstrated the presence of IDIR virus structural proteins having estimated molecular weights of 130, 100, 88, 80, 61, 44, 32, and 25 kDa. Treatment of complete viral particles with EDTA removed the outer capsid layer producing single-shelled particles that lacked the 80, 61, 32, and 25 kDa proteins seen in the double-shelled particles. The 44-kDa protein was most abundant and was recognized by a mouse monoclonal antibody and hyperimmune guinea pig serum prepared against IDIR virus and by hyperimmune guinea pig serum prepared against adult diarrhea rotavirus (ADRV), a human strain of GBR. Convalescent serum obtained from a piglet inoculated with a porcine GBR reacted with the 61 kDa, outer capsid protein of IDIR virus. This information on the structural nature of IDIR virus should be helpful in establishing the genetic and structural relationships among the GBR and to further exploit the potential of IDIR virus as a tool for understanding GBR infections in human and animal populations.