Polypeptides of endogenous avian C-type viruses: Their detection in the plasma membrane of normal and infected cells

Abstract Uninfected as well as avian leukosis sarcoma virus-infected fibroblasts from a variety of avian and mammalian species were investigated for the cell surface expression of endogenous or exogenous type-C virus polypeptides. A sensitive 14 C-nicotinamide membrane permeability (NAMP) test was used to check cell surface binding of rabbit antibodies monospecific for individual avian type-C virus polypeptides (VPP). Uninfected chicken, jungle fowl, turkey, and ring-necked pheasant cells reacted positively with antibodies specific for the major virus polypeptides with molecular weights of 85,000 (gp85), 37,000 (gp37), 27,000 (p27), and 15,000 (p15). Antisera to the VPP 19,000 (p19) and 12,000 (p12) were negative. These positive reactions are interpreted as the result of VPP-synthesis by endogenous avian type-C viruses. The same pattern of antibody reactivity was also seen with all virus-infected avian cells. Uninfected fibroblasts from a variety of other avian species as well as (with one exception) all mammalian cells, irrespective of whether or not the latter were virus-infected, did not react with any of the antisera. A correlation between endogenous VPP expression and positive chicken helper factor activity could not be demonstrated.