Quantification and characterization of avian RNA tumor virus group specific antigen by radioimmunoassay

Although the gs antigen preparation used in the RIA had originally been thought to contain only one protein, further analysis by column chromatography and polyacrylamide gel electrophoresis revealed the presence of two viral polypeptides. Subsequent analysis of the immune precipitates of the RIA by SDS polyacrylamide gel electrophoresis identified 70 percent of precipitable radioactivity as gs-1 (major antigen) and 30 percent as gs-3. Extensive immunological competitive inhibition reactions confirmed this analysis. The RIA for avian group specific antigen has, therefore, duel specificity since it does not require one polypeptide specificity for the majority of its applications. The RIA was used to follow the progress of in vitro infection by avian leukosis and sarcoma viruses by monitoring the intracellular appearance of gs antigen. In these studies gs antigen was detected within 6-12 hours after virus infections. This was 6 hours before the release of progeny virus and 18 hours before the previous studies had detected viral products. These studies were also important in demonstrating the feasibility of using production of an intracellular viral antigen as a marker to follow virus infections. The success of these in vitro studies allowed the quantification in vivo of the pathogenesis of a virus induced chicken leukemia, avian myeloblastosis