Morphology of central nervous system disease in immunosuppressed mice after peripheral herpes simplex virus inoculation. Trigeminal root entry zone.

Inoculation of mice and rabbits on the cornea with herpes simplex type 1 virus has been shown to cause an ascending infection of the trigeminal nerve, ganglion, and descending tract within the brainstem (2, 3, 7). A discrete, destructive, and primarily demyelinative lesion is seen on the central nervous system side of the trigeminal root entry zone 5 to 8 days after infection (8, 15, 16). This study, utilizing Swiss mice, demonstrated that immunosuppression with cyclophosphamide prior to infection with herpes simplex type virus causes a marked reduction of the mononuclear infiltrate within the central nervous system and a significant decrease in myelin destruction when compared with the infected, nonimmunosuppressed control animals. The content of virus in the brainstem was similar in both groups by day 8 as were the neutralizing antibody titers to herpes simplex type 1 virus. These results suggest that the cellular response plays a definitive role in the destruction of central nervous system tissue after peripheral infection with herpes simplex type 1 virus.