Serum activity inhibiting specific simian virus 40-induced transplantation resistance and its correlation with primary SV40 tumors appearance in hamsters.

Using the modified technique of transplantation test, ITR serum activity was found in most (14 out of 21) individual hamster sera obtained during the latent period of primary SV40 carcinogenesis (60 days after virus infection when newborn). On the other hand, as a rule, no ITR activity was observed in the sera of the same hamsters after tumor appearance and during their growth. ITR activity rapidly disappeared from sera of hamsters neonatally infected with SV40 after their successful immunization with the same virus during the latent period. There appears to be a correlation between the presence of ITR serum factor during the latent period and the subsequent primary SV40 tumor appearance in hamsters.