POSSIBILE REQUIREMENT OF DNA SYNTHESIS FOR THE GROWTH OF FRIEND LEUKEMIA VIRUS

Abstract
MLg cells originated from lung tissues of newborn ddY mice were successfully infected with tissue culture-grown Friend leukemia virus and a growth curve of the virus in vitro was obtained. The leukemogenicity of the culture fluid was detectable as early as 18 hr. post-infection and the maximum virus titer was 104 ID50/ml on the 5th day post-infection. Cytosine arabinoside, a specific inhibitor of DNA synthesis, as well as actinomycin D, when added during adsorption or immediately after adsorption, inhibited the growth of Friend leukemia virus in vitro, suggesting that a transitory DNA synthesis is required for the growth of Friend leukemia virus in the early stages of the infection.