Isolation and Characterization of an Antigen of the Bovine C-type Virus1

by the immunodiffusion test was found to be the same as that detected by the IFA technique (5). Previous studies also showed that disruption of the virus is necessary for release of the antigen, suggesting that the antigen is an internal virion component (3, 6). The resistance of the BLV antigen to ether and acetone, and its presence in the cytoplasm of infected cells, are features which also characterize the gs antigen of the major internal proteins of the other known Ctype viruses (11, 16, 17). On the other hand, no immunobogi cal relationships between the BLV antigen and the gs anti gens of other leukemia viruses could be demonstrated (3, 6). Subsequent investigations were concerned with the isola tion, purification, and further characterization of the inter nal BLV antigen. Similar studies in other C-type virus sys tems were facilitated by the availability of large amounts of purified virus. However, at the time these studies were initi ated, our sources of BLV were limited to lymphoid cultures (short-term cultures of bovine BC cells and New Bolton Center cell lines) in which most virus particles are associ ated with cell membranes. This made it extremely difficult to obtain the amounts of purified virus required to extract enough antigen for characterization. Consequently, we de cided to investigate the possibility of isolating and purifying the antigen from BLV-infected cells that contain free anti gen in the cytoplasm and that usually have numerous virus particles attached to the cell membrane. Using G-100 Seph adex chromatography and isoelectric focusing, it was pos sible to obtain a good yield of antigen in a highly purified form from extracts of such BLV-infected cells. The antigen is present on an internal BLV protein with a molecular weight and isoelectric point similar to that of the major internal proteins of other mammalian leukemia viruses. Im munodiffusion studies showed that the BLV antigen is im munologically unrelated to the antigens of MuLV, FeLV, the foamy-like BSV (20), and the MPMV. A preliminary report of some of these findings has been presented elsewhere (22).