In vitro and in vivo inhibition of virus multiplicaton by microwave hyperthemia.

The effect of microwave hyperthermia (41 degrees and 43 degrees C) on virus multiplication have been explored in vitro (HSV-1 infected primary rabbit kidney cultures) and in vivo (mice infected with HSV-1 or vaccinia). In vitro the cells were inoculated with HSV-1 and heated to 41 degrees or 43 degrees C either before or after infection. Virus yields were significantly decreased when the cells were exposed to hyperthemia within the first few hours after infection, while hyperthemia was without effect when applied before infection or with several hours delay after infection. In mice inoculated intranasally with HSV-1, mortality due to herpes encephalitis was significantly reduced upon daily exposure to microwave hyperthermia from the day of infection onward. In mice inoculated intravenously with vaccinia, a significant decrease in the number of specific tail lesions was observed if the animals were exposed to microwave hyperthermia within the first three days after infection, while irradiation prior to infection or delayed until several days after infection did not exhibit an appreciable effect. Our data suggest that microwave hyperthermia interferes directly with the virus multiplication cycle both in vitro and in vivo.