Ionizing radiation modulates the spread of an apathogenic rabies virus in mouse brain.

Ionizing radiation has been shown to affect a broad range of viral diseases including neurotropic infections through an immunosuppression mechanism. In the present study we have investigated the effect of ionizing radiation on the characteristics of neurotropic infection by rabies virus, which has the unusual feature of infecting almost exclusively neurons. In order to analyze better the effect produced, the study concerned the spread of an apathogenic rabies virus variant in mouse brain. Irradiation was shown to increase both the intensity and duration of the infection in a reversible and dose-dependent manner and was effective in whole-body irradiation and in head-protected body irradiation, whereas cephalic irradiation had no effect. These results underline the role played by the immune system in the regulation of neurotropic virus infections in the brain and show that phenomena such as viral clearance and time-course of a neurotropic viral infection may be significantly modified by ionizing radiation, even for viruses whose infection involves only neurons.