Interaction between cellular and viral genes in the expression of the RSV‐induced transformation‐specific cell‐surface antigen VCSA

Transformation of BHK hamster fibroblasts by an env strain of Rous sarcoma virus (RSV) leads to the appearance at the cell surface of a virus‐induced nonvirion antigen (VCSA), specific for transformation, whose expression is controlled by the transforming src gene. Previous work has shown that a rabbit anti‐VCSA serum lyses specifically, in the presence of complement, ⁵¹Cr‐labelled RSV‐transformed cells from different animal species. Now, by competition experiments with a panel of different unlabelled cells we show that the VCSA expressed on RSV‐transformed hamster fibroblasts is a complex of at least three distinct antigenic specificities: (1)one expressed on all RSV‐transformed fibroblasts, regardless their species and the subgroup or strain of the transforming virus; (2) one cross‐reacting with a cell‐surface antigen (CSA) expressed at various degrees on untransformed avian fibroblasts, but not on mammalian fibroblasts; (3) one species‐specific, present only on RSV‐transformed hamster fibroblasts. It is concluded that VCSA is a complex of several antigenic determinants, and that some of these differ in different cells transformed by RSV. This observation indicates that VCSA expression at the cell suface is likely to be the result of the interaction between the viral src gene product pp60^src with host cell gene(s) or gene product(s), rather than the simple expression of this molecule at the cell surface.