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.