Transformation of Simian Virus 40-resistant Hamster Cells with an Adenovirus 7-Simian Virus 40 Hybrid

When the hamster cell lines BHK21 and Nil-2 were infected at a multiplicity of 100 with the adenovirus 7-simian virus 40 (SV40) hybrid (strain LLE46), SV40 T antigen was induced in 0.1 to 6% of the cells during the first 96 hr postinfection, morphological changes occurred 3 to 7 weeks later, and eventually all the cells contained SV40 T antigen, but no adeno 7 T antigen. Results were similar when primary and secondary monolayer cultures of hamster embryo (HE) cells were infected with the adeno 7-SV40 hybrid, and when primary HE cells were infected with SV40. However, infection of BHK21, Nil-2, and secondary HE cells with the same multiplicity of SV40 did not induce SV40 T antigen or morphological transformation. This suggests that the target cells required for infection with SV40 virions, but not those required for infection with the hybrid, are lost or altered in secondary HE cultures and in the two cell lines. In most of the virus-host cell systems in which SV40 T antigen and transformation were induced, there was a decrease in the number of T antigen-positive cells after the initial infection. This was followed by a lag period of up to 2 months before the onset of a progressive increase in the number of positive cells. The beginning of the rise in T antigen production coincided with the first morphological changes.