Invasion of the central nervous system by herpes simplex virus type 1 after subcutaneous inoculation of immunosuppressed mice.

Young adult mice given subcutaneous inoculations in the rear footpad with herpes simplex virus type 1 were found to be resistant to infection unless they were immunosuppressed with sublethal doses of irradiation or cyclophosphamide. In these mice, virus multiplied in the sciatic nerve three to four days after inoculation. This development was followed by multiplication of virus in the spinal cord and brain, which caused death of the mice in about eight days. No virus was detected in the blood or liver. Resection of the sciatic nerve significantly increased the number of immunosuppressed mice surviving footpad inoculation. Passive transfer of antibody had no effect on the course of infection. Sublethal doses of irradiation or cyclophosphamide can apparently increase the susceptibility of the central nervous system to invasion of Herpesvirus from extraneural sites of infection by spread along peripheral nerves.