Protective effect of an oral infection with Herpes simplex virus type 1 against subsequent genital infection with Herpes simplex virus type 2

The problem of whether oral Herpes simplex virus type 1 (HSV-1) infection provides protection against subsequent genital infection by Herpes simplex virus type 2 (HSV-2) was investigated. Mice were used as models. Following conditions in man, both the oral and genital infections applied were noninjurious. Mice infected orally with HSV-1 were weakly protected against virus take following vaginal challenge with HSV-2. Genital takes were found in 67% of the immunized mice, as compared with 83% of the controls (protection rate 20%,P=0.002). The course of genital infection in the immunized mice, however, was relatively mild: Lethality decreased from 97% in the controls to 35% in the immunized mice (protection rate 63%,P<0.001). Furthermore, local and neurologic symptoms occurred less frequently. Attempts to isolate the virus from homogenized brain and spinal cord of immunized mice that died after genital challenge with HSV-2 failed in most cases. Also virus could not be recovered from the liver of infected mice, irrespective of the experimental group.