Alphaherpesvirus saimiri in rabbits: a model for human encephalitis?

One (KM91) of a series of isolates of alphaherpesvirus saimiri (alpha HVS) produced rapidly fatal encephalitis in rabbits following intradermal infection, whereas the others (KM180, KM322 and KM338) were non-lethal and produced ganglionitis and prolonged latency. Alphaherpesvirus saimiri KM91 initially produced ganglionitis but quickly ascended the spinal cord to the brain causing death 10 days post-infection. Prior infection with any of the three benign isolates or inoculation with beta-propiolactone (beta PL)-inactivated alpha HVS KM91 protected rabbits from lethal encephalitis when they were subsequently challenged with a lethal dose of alpha HVS KM91. Each of 20 rabbits co-inoculated in the same site with a lethal dose of alpha HVS KM91 and either alpha HVS KM322 (1.5 X 10(3) to 1.5 X 10(5) p.f.u.) or beta PL-inactivated alpha HVS KM322 (1 X 10(7) p.f.u. equivalents) survived. In contrast only half of those co-inoculated with alpha HVS KM91 and beta PL-inactivated alpha HVS KM91 (1 X 10(7) p.f.u. equivalents) survived. Co-inoculation of lethal alpha HVS KM91 (75 p.f.u.) and benign alpha HVS KM322 (1.5 X 10(3) p.f.u.) into opposite flanks resulted in protection from encephalitis in one of four rabbits. Alphaherpesvirus saimiri KM91 was shown to have the capacity to become latent in dorsal root ganglia if the rabbit did not die.