Schwann cell remyelination in experimental herpes simplex encephalitis at the trigeminal root entry zone.

Inoculation of mice on the cornea with herpes simplex virus, type I, results in demyelination of central nervous system (CNS) axons at the trigeminal root entry zone. This study examined the process of remyelination in this area. Between eight and 15 days after corneal infection, increasing numbers of Schwann cells appeared on the CNS side of the trigeminal root entry zone, where they encircled the demyelinated CNS axons. Remyelination of CNS axons by Schwann cells began between 12 and 15 days and increased during the following weeks. Remodeling of remyelinated internodes continued during the nine weeks of observation. No infectious virus could be cultured 15 days after infection, although latent virus was recovered from the dorsal root ganglia at this time. The disruption of astrocytes on the CNS side of the trigeminal root entry zone during the early stages of infection and the proximity of Schwann cells to the CNS trigeminal root entry zone appear to be important factors affecting CNS remyelination.