Summary
Thymectomy of newborn hamsters enhanced the tumorigenicity of polyoma virus given 1 week or 4 months after surgery, of SV40 virus given 1 week after surgery, and of adenovirus 3 and 7 injected immediately after thymectomy. There was no effect on tumor incidence following adenovirus 12 given in high or low dose immediately after surgery. Adenovirus types 1 and 4, influenza types A, A2, and B, ECHO 25, poliovirus 1, reovirus 1, vaccinia, and M. orale 1 failed to induce tumor when inoculated into newborn thymectomized and nonsurgically treated hamsters. The influence of age on host susceptibility to viral oncogenesis was studied by inoculating adenovirus 7 and SV40 virus into newborn, 1-, 3-, and 12.5-14-month-old hamsters. Adenovirus 7 induced tumors in the newborn group alone; by contrast, SV40 virus induced tumors in all age groups. The influence of virus strain and cell culture passage on oncogenicity was studied with the Pinckney and Gomen strains of adenovirus 7. These latter factors did not affect the induction of tumors in newborn hamsters; instead, the amount of virus given was the most important determinant. The significance of the findings in relation to detection of oncogenic viruses are discussed.
