Isolation and characterization of soluble antigens of sheep poxvirus

A soluble antigen fraction of sheep poxvirus (SPV) isolated from infectious virus particles by ultracentrifugation and purified by subtractive immunoaffinity chromatography was characterized. Exclusion chromatography studies revealed 10 proteins of molecular weight (MW) 220, 168, 87.3, 71.5, 52.5, 36.7, 31.0, 23.4, 18.3 and 14.2 kDa. Nine of them were found to be precipitinogens and 5 were identified as structural components of the virus particles. SDS-PAGE analysis revealed a polypeptide profile of 10 bands with 2 prominent polypeptides of 64 and 42 kDa. Western blotting, however, detected 2 immunogenic polypeptides of MW 100 and 64 kDa. Moreover, crossed immunoelectrophoresis showed the presence of proteins of varied electrophoretic mobility and sharing of antigenic determinants among a few soluble antigens. Physico-chemical characterization further revealed that these precipitinogens can withstand ambient temperatures, but were sensitive to trypsin and ether whereas, chloroform had no effect on immunoprecipitation pattern of soluble antigens.