Characterization of Polyoma T Antigens Through Immunological Studies

Abstract

Polyoma, a virus shich induces tumors in rodents, encodes three proteins involved in the process of tumorigenesis: the large, middle, and small T antigens. Two projects were performed with the goal of eventually characterizing the T antigens better. The first project involved monitoring immunological responses to the T antigens and two experiments were performed. In experiment one, a postulated correlation between tumor induction in rats and anti-T antigen antibody production was investigated. No correlation was found, however, as some animals with polyoma-induced tumors produced no detectable levels of antibody, and animals which rejected their tumors also experienced varying antibody responses. The purpose of the second experiment was to isolate hybrid-melanoma (hybridoma) cells producing monoclonal antibodies to the three T antigens. Hybridomas were successfully cloned for large and middle T antigens, although none specific for small T were isolated. The second project was designed to characterize by restriction analysis a group of previously prepared plasmids with integrated polyoma sequences having deletions in the EcoRI region of the genome (0 map units). This region of polyoma encodes the carboxy-terminus of middle T antigen so that upon injection into animals, the amount of deletion of middle T possible before protein inactivation could be determined. Three plasmids were characterized, and one was determined to have a deletion within the 97 map unit middle T terminus, while the other two had deletions mapping beyond the sequence encoding middle T.