Sarcoma in a hamster inoculated with BK virus, a human papovavirus

An undifferentiated sarcoma occurred in 1 of 52 hamsters inoculated when newborn with BK virus (BKV), a simian virus 40 (SV40) related human papovavirus. It was transplantable and grew in tissue culture. Sera of tumor bearing hamsters were without antibodies reactive to BKV virion antigens in hemagglutination inhibition and neutralization tests, but contained antibodies reactive in immunofluorescence (IF) tests to SV40 T antigen in SV40 transformed cells and to antigens in cells acutely infected with BKV or SV40. The IF reaction between tumor cells and sera of tumor bearing hamsters was minimal in tests of tumor cells of an early passage but satisfactory in tests of cells from a later passage. Fusion of tumor cells with permissive (monkey and human) cells, induced by inactivated Sendai virus, did not lead to recovery of infectious BKV. Immunization of hamsters with BKV or SV40 failed to protect against challenge with tumor cells. There was considerable cross reactivity between the T antigens of BKV and SV40 viruses.