Immunoaffinity purification of two major proteins of bovine leukemia virus (gp51 and p24) and their use for discrimination between vaccinated and infected animals.

The outer envelope glycoprotein gp51 and the core protein p24 of bovine leukemia virus (BLV), were purified from culture media of FLK-BLV cells by a single-step procedure, using immunoaffinity chromatography based on monoclonal antibodies to the respective proteins. About 90% of the envelope glycoprotein in the culture medium was recovered as a highly purified product. Both purified protein (gp51 and p24) preparations, were found to be highly specific antigens by ELISA, and did not cross-react with sera raised against the other antigen. The conformational epitopes on the purified gp51 were preserved as judged by their reactions with the corresponding monoclonal antibodies. The p24 ELISA reacted only with sera from naturally infected animals and not with sera from animals immunized with an experimental gp51-iscom vaccine. The p24 antigen is therefore useful for discriminating between BLV-infected animals and those immunized with a gp51 subunit vaccine.