Encephalitis resulting from reactivation of latent herpes simplex virus in mice

Herpes simplex virus (HSV) encephalitis was produced in mice from reactivation of latent virus. Two experimental models were used: the trigeminal model after corneal inoculation of HSV, and the hypoglossal model after tongue inoculation of HSV. In the trigeminal model, cyclophosphamide treatment induced reactivation of latent virus in ganglia but not in central nervous system tissue. Spread of the reactivated virus from ganglia to brain occurred only in mice deficient in anti-HSV antibody. In the hypoglossal model, sectioning of the hypoglossal nerve provoked chromatolysis in the corresponding central nervous system motor neurons and occasionally reactivated latent HSV in the brains of mice. These results suggest that HSV encephalitis can result from the spread of reactivated virus from ganglia to brain and also from in situ reactivation in brain.