Mammalian tropism of B77(RBI) virus. Expression of virus genome in the hamster sarcoma cell clones.

In contrast to the B77 virus, its B77(RBI) rat variant continuously produced by the rat RBI sarcoma cells in vivo and in vitro, efficiently induced progressively growing tumors in hamsters and transformed hamster embryo cells in vitro. Both, induced tumors and transformed cell cultures showed production of infectious virus and presence of the avian gs-antigen. Clonal analysis of the established hamster sarcoma cell line RBHtc brought evidence that despite the quantitative differences in the virus production and gs-antigen content among various clonal populations, full expression of the B77(RBI) virus genome does occur in each cell of the virus-induced hamster sarcoma. The permissive relationship of the B77(RBI) virus with rat and hamster cells as well as changed antigenic composititon implies that a genetic change of the virus occured, which is reflected in its increased mammalian tropism and its genetically stable firus-productive interaction with mammalian cells. The possible explanations of these phenomena are discussed.