An adenovirus vector system used to express polyoma virus tumor antigens

We have used a generalized adenovirus vector system to express the three polyoma tumor (T) antigen proteins under the control of the adenovirus major late promoter. One hybrid virus, Ad-PySVR498, expresses high levels of polyoma middle and small T antigens. A second hybrid virus, Ad-LTSVR545, which contains a cDNA copy of the polyoma A gene, overproduces large T antigen. The T antigens produced are indistinguishable from their authentic polyoma counterparts as determined by immunoprecipitation and partial cleavage by V8 protease. Analysis of polyoma mRNAs encoded by the recombinant viruses showed that they initiate from the adenovirus major late promoter and contain the tripartite leader at their 5' ends. Large T antigen isolated from Ad-LTSVR545-infected cells by immunoaffinity was shown to bind selectively to polyoma DNA sequences that contain the origin of viral DNA replication as well as the sites for transcription initiation.