Immunochemical analyses of Australian bluetongue virus serotypes using monoclonal antibodies.

In order to characterize the immunochemical role of bluetongue virus (BTV)-specified proteins and provide reagents capable of defining the serological relatedness of bluetongue (BT) serotypes and their relationship with other orbiviruses, a panel of 16 IgG monoclonal antibodies was raised to the Australian BTV serotypes, isolate CSIRO156 (BTV 1), CSIRO19 (BTV20) and CSIRO154 (BTV21). Analyses of virus-coded polypeptide specificities of these monoclonals using enzyme-linked immunosorbent assay (ELISA), a radioimmunoprecipitation assay (RIPA), and a virus neutralization assay, revealed the outer coat viral protein P2 to have a major role in the neutralization of both CSIRO156 and CSIRO19. Presumptive evidence for the involvement of the P3 protein in the neutralization of CSIRO19 was also obtained. The virus-specified non-structural protein P6A induced a group reactive immune response to all 3 serotypes. Antigenic relationships between P3 of CSIRO156 and P2 of CSIRO19 were found, and an analysis of the relationships between epitopic regions on P2 and P3 of both viruses revealed several distinct immunogenic sites exist on the P2 protein.