Immunization with a nonpathogenic HSV-1 strain prevents clinical and neuroendocrine changes of experimental HSV-1 encephalitis

We examined whether immunization with the nonpathogenic strain R-15 of herpes simplex virus-1 (HSV-1) may prevent the clinical and neuroendocrine changes induced by the pathogenic HSV-1 strain Syn17+. Inoculation of strain Syn17+ to control rats induced fever, marked motor hyperactivity and aggressive behavior, and increased serum ACTH, corticosterone (CS) and brain prostaglandin-E₂ production. Mortality was 100%. Immunization with strain R-15 prior to challenge with Syn17+ induced the production of neutralizing antibodies to HSV-1 Syn17+, and abolished the above clinical and neuroendocrine changes. Mortality was completely prevented. These results indicate that immunization with HSV-1 strain R-15 protects rats from lethal HSV-1 encephalitis and prevents its clinical and neurochemical manifestations.