RNA type C virus antigens in hamster cells transformed by carcinogenic DNA viruses and chemicals

The passive hemagglutination inhibition technique was used to test serologically for the presence of Syrian hamster type C virus antigen(s) (SHCVA) in a wide variety of normal and transformed hamster cells and tissues. SHCVA could not be detected in normal tissues or nonneoplastic tissues of tumor-bearing Syrian hamsters. Normal hamster embryo cells or cells transformed in vitro by simian adenovirus, by chemical alone, or doubly transformed by simian adenovirus and chemical did not contain SHCVA; however, SHCVA was found in a majority of tumors resulting from transplantation of these in vitro-transformed cells. No consistent pattern was observed in the capacity of individual transformed cell lines to produce SHCVA-positive or -negative tumors. When cells of a given transformed line were inoculated at 4 sites on each of 8 hamsters, SHCVA-positive tumors were found not to be randomly distributed but rather to be clustered on a few animals. SHCVA could be detected in only a few primary tumors induced by inoculation of carcinogenic DNA viruses; however, both the incidence and titer of SHCVA were significantly increased in a variety of transplanted tumors. These data suggest that SHCVA may be introduced into transplanted, transformed hamster cell tumors during passage in the host animal. Alternatively, in vivo conditions may allow expression of viral antigens not found under in vitro conditions; however, if this is true, only certain animals appear to be capable of activating SHCVA.