Combined effects of Venezuelan equine encephalitis IIIA virus and gamma irradiation in mice.

The combined effects of injury from exposure to ionizing radiation and the potential biological warfare agent Venezuelan equine encephalitis (VEE) virus remain largely unknown. To study these effects, 4- to 5-week-old B6D2F1/J female mice were given a sublethal whole-body 7 Gy dose of 60Co gamma-photon radiation followed 48 hours later by aerosol or intraperitoneal challenge with enzootic VEE IIIA virus. Survival was observed for 30 days. A single sublethal 7 Gy dose of gamma radiation reduced the LD50/30 of VEE IIIA virus, in intraperitoneal challenged mice by a factor of 10(4) from 1.1 x 10(6) plaque-forming units (pfu) to 1 x 10(2) pfu, and in aerosol challenged mice, by a factor of 5 from 70 pfu to 14 pfu. These findings further confirm there is a combined effect of exposure to ionizing radiation and biological warfare agents, which could be devastating to unprotected populations and thus should be investigated further.