Growth of cytomegalovirus at supra-optimal temperatures

An isolate (Mira) of cytomegalovirus is shown to replicate in human embryonic lung fibroblasts at supra-optimal temperature (40 degrees C). The ability of the Mira isolate to grow at 40 degrees C decreased as a function of age of cells in which the virus was grown. The unusual morphology of the lesions in late passage cells infected and maintained at 40 degrees C is illustrated.