Herpes simplex virus type 1 envelope subunit vaccine not only protects against lethal virus challenge, but also may restrict latency and virus reactivation.

A subunit vaccine containing the main antigenic components of herpes simplex virus 1 (HSV-1) was tested in Balb/c mice and albino rabbits. The mice were completely protected against challenge with 10 LD50 of the highly pathogenic SC16 strain given by intraperitoneal (ip) route when immunized with 1000 antigen units (ELISA) corresponding to 110 micrograms of protein. The animals were protected against lethal disease when immunized with 1-33 micrograms of protein per dose. Immunization of rabbits with 3000 antigen units prior to inoculation of strain Kupka into right scarified cornea limited the establishment of latency in the trigeminal ganglia. Both the number of animals in which latency had been established as well as the number of homolateral sensory ganglion cells which had become virus carriers were reduced. However, the effect of immunization was less striking at preventing HSV reactivation in rabbits vaccinated after infection. When shedding of reactivated HSV was elicited by repeated epinephrine iontophoresis to cornea, there was no quantitative difference between the immunized and mock-immunized groups, only the period between stimulation and the onset of virus shedding was prolonged in immunized rabbits (from 3.6 to 5.6 days, p < 0.05). But if the corneas were stimulated by a single iontophoresis procedure, the duration of virus shedding was significantly reduced from 5.6 days in the mock-immunized rabbits to 1.7 days in the immunized ones (p < 0.025). In the latter experiment, the total number of positive swabs during 14 days of the post-stimulation period was higher in the mock-immunized animals (31 of 171, 18.1%) than in the immunized ones (12 of 162, 7.4%; p < 0.025).