Effect of cordycepin on the replication of type-c RNA tumor viruses

Cordycepin (3'-deoxyadenosine) was previously shown to inhibit virus production induced by iododeoxyuridine from murine fibroblasts (Wu et al., 1972). We now report that the inhibitory effect of cordycepin results in a reduction of the number of cells producing virus as measured by the infectious center assay and fluorescent antibody technique. Cordycepin has a much greater inhibitory effect on viral replication than on transformation of normal rat kidney cells by murine sarcoma virus since viral production was greatly reduced (seven- to 35-fold) with 5-10 mug/ml of cordycepin while viral transformation was only slightly inhibited (two-fold reduction in focus-forming units) with the same concentration of cordycepin. Inhibition of viral production is most effective if the compound is present during the first 24 h after injection.