Infection and transformation of dog cells with a modified sarcoma virus

Dog-embryo cell cultures were infected with a mixture of feline leukemia virus (FelLV) and a modified murine (Moloney) sarcoma virus MSV(FelLV). Morphological alteration of the cells was observed 3 days post infection. Virus progeny from the infected cultures increased 50- to 100-fold in foci of cellular alteration on dog cell cultures pretreated with diethylaminoethyl-dextran, but only twofold on cat embryo cultures similarly treated. The numbers of foci produced corresponded to a dual infection with the MSV(FelLV) and endogenous FelLV and could be increased by simultaneous infection with exogenous FelLV. After five serial passages in dog cell cultures, the virus mixture still had a superior focus-inducing capacity on cat cells as compared with dog cells. Electron microscopic examination of infected dog cultures showed typical C-type virions. FelLV alone propagated in dog cell cultures without inducing morphological alteration, and progeny virus, capable of promoting focus formation by MSV(FelLV), could be detected 48 hours post infection.