Restriction of latent herpes virus infection in rabbits immunized with subviral herpes simplex virus vaccine.

The ability of an experimental herpes simplex virus type 1 (HSV) vaccine to influence the establishment of latent infection was examined. The virion-free vaccine was prepared from HSV 1-infected LEP cells by extraction with Nonidet P 40. Albino rabbits were immunized with three doses of the subviral vaccine (strain KOS) and challenged with 10(5) PFU of HSV 1 (Kupka strain) into the right scarified cornea. Non-immune controls and rabbits immunized with formalin-inactivated virion vaccine (strain KOS) were infected in a similar way. At intervals from 53 to 164 days p. i., the animals were killed and fragments of both trigeminal ganglia were kept separately in culture for 10 days. In 18 out of 22 immunized animals (81.8%), latency was established in the homolateral Gasserian ganglion. The proportion of HSV-yielding fragments, was considerably higher in ganglia from non-immune animals (42.6%) as compared to those from ganglia of rabbits immunized with the subviral vaccine (5.4%) or with the whole virion vaccine (14.6%). The immunity resulting from previous vaccination restricted about 5 times the number of ganglion cells, which become virus carriers.