The effect of supraoptimal temperature on the multiplication of different cytomegalovirus strains

Virion synthesis by 5 human cytomegalovirus (CMV) strains in human embryonic fibroblast cultures was stopped by incubation of the infected cultures at 40°C. At this temperature the antigens diffusely filled the nucleus and cytoplasm. The blocking effect of the elevated temperature was exerted in the same stage of the reproduction cycle as the inhibitory effect of cytosine arabinoside. In cell cultures infected with CMV and incubated first at 40°C, and then at 37°C, the synthesis of infectious virus restarted, thus the abortive cycle which was developed at 40°C was reversible. The inhibition of virus multiplication cannot be attributed to thermosensitive activities in the normal function of the host cell.