An autoradiographic and immunofluorescent study of the infectious cycle of sheeppox virus in cell cultures exposed to 5-fluorodeoxyuridine.

No progeny virus is detected by determination of the infectivity titres when embryo muscle cell cultures are exposed to a concentration of 10−5 M of 5-fluorodeoxyuridine at the time of sheeppox virus infection. The autoradiographic preparations of FUdR treated cells showed cytoplasmic labelling into viral DNA (tritiated deoxyuridine) in 4 to 9% of the cells during the first 24 hours of infection. In cells exposed to FUdR in which viral DNA synthesis was detected by autoradiography, progeny virus not detectable by infectivity test might be produced. The demonstration of viral proteins by immunofluorescence served to establish that viral DNA synthesis is not essential for viral protein synthesis in FUdR treated cells. Under light microscopy, there is no apparent difference between the cytopathic effects of viral infection in treated and in untreated cells.