Thermoinactivation of Human Cytomegalovirus

Abstract

The inactivation at 4 and 37 C of several strains of human cytomegalovirus was studied. The preliminary findings that freshly har -vested cytomegalovirus was inactivated more rapidly at 4 C than at higher temperatures was confirmed. Intracellular virus still within infected cells was found to be more stable at 4 C than virus released by sonic treatment just before incubation at 4 C. The composition of the diluent played an important role. In tris(hydroxymethyl)-aminomethane buffer, virus was unstable both at 4 and 37 C, with the rate of inactivation faster at 4 than at 37 C. Similar results were obtained when bicarbonate-phosphate buffer or Eagle''s medium with bicarbonate was used as virus diluent. Calf serum stabilized the virus at 37 C, but not at 4 C. The deletion of bicarbonate from Eagle''s medium had a stabilizing effect at both temperatures. An even greater stabilizing effect at both 4 and 37 C was obtained when distilled water was used as virus diluent. Inactivation rates varied from one strain to the next at 4 C but not at 37 C. Differences were found also with virus progeny derived from a single strain, but harvested at different stages during virus multiplication. Virus harvested early was more labile at 4 than at 37 C, whereas the late virus was more labile at the higher temperature. Intracellular and extracellular virus preparations were inactivated at the same rates at either 4 or 37 C.