Effect of 5-fluoro-2′-deoxyuridine on the synthesis of vaccinia virus

Abstract

The effect of FUDR on vaccinia virus replication in HeLa cells was investigated. The incorporation of deoxyuridine-H 3 into viral DNA, as determined by autoradiography, was completely blocked by 10 −6 M FUDR. This concentration of the analog prevented production of infectious virus above levels present in the cultures after washing at the end of the viral adsorption period. The production of vaccinial HA was also inhibited. However, 20–70% of the inhibited cells produced NP and LS antigen detectable by the fluorescent antibody technique. These findings were in accord with the results of previous experiments using p-fluorophenylalanine which had suggested that viral antigen can be synthesized in the absence of synthesis of viral DNA. The proportion of cells that synthesized antigen was progressively reduced by increasing the concentration of FUDR or increasing the duration of pretreatment of cultures with the analog. The inhibition of synthesis of infectious virus and of viral antigen was not prevented by uridine added with the FUDR but was reversed by thymidylic acid added at the time of infection to cultures that had been pretreated for as long as 12 hours with FUDR. When FUDR was added to cultures at the time of infection and thymidylic acid was added 12 hours later, the proportion of cells that synthesized viral antigen was essentially the same as in cultures not treated with FUDR; however, the yield of infectious virus in the former cultures was only 15% of that from cultures not treated with the analog.