Plaque Formation by Vaccinia Virus in Tissue Cultures Inhibited by 5-Fluorodeoxyuridine

Abstract

Vaccinia virus forms plaques in monolayers of RK 13, Hep. 2 and EeLa cells grown in concentrations of 5-fluorodeoxyuridine (FUDR) higher than those previously claimed to inhibit completely the synthesis of vaccinia virus DNA in suspended tissue cultures. The limited virus synthesis observed is not due to a varying susceptibility of the cells to FUDR, nor to the selection of virus resistant to FUDR. Experiments suggest that virus synthesis is made possible by thymidine from the DNA of dead cells.