Effect of the expression of an endogenous viral gene on the growth of tumours induced by Rous sarcoma virus in chickens.

: The endogenous group-specific antigen of avian retroviruses has been detected in feather pulp of chickens of the inbred CB line (WL breed). Expression of the gs antigen has been demonstrated by ELISA, whereas the classical methods have classified the CB line as gs-. The number of gs+ chickens decreased with increasing age after hatching, and all chickens were gs- already at 20 weeks of age. The longer duration of gs antigen expression in line CB chickens had an adverse effect on their ability to regress Rous sarcomas. Chickens from a closed flock of the BL breed that segregated to gs+ and gs- also significantly differed in the ability to regress Rous sarcomas.