OCULAR INFECTION WITH HERPES-SIMPLEX VIRUS IN SEVERAL STRAINS OF RAT

Purpose. To assess the suitability of the rat for studies of ocular infection with herpes simplex virus (HSV). Methods. LEW, AO, DA, PVG, and (DAxLEW)F-1 X LEW backcross generation rats, 7 to 9 weeks of age, were inoculated with HSV-1 McKrae. The course of primary disease was assessed by clinical observation using a slit lamp. Infectious virus was assayed in ocular and nervous tissue, and the incidence of latent infection was determined. Results. LEW and AO strains were the most susceptible. All LEW rats died after an inoculum of 4 X 10(2) plaque-forming units (pfu) and developed severe corneal disease and uveitis. In contrast, all PVG rats survived 10(4) pfu, 60% survived 4 X 10(4) pfu, and eye disease was restricted to epithelial lesions, sometimes accompanied by mild stromal haze. This resolved, even in animals that developed central nervous system disease. The DA strain showed intermediate susceptibility. Resistance was dominant because disease in backcross generation (DA X LEW)F-1 X LEW rats resembled that of the DA rather than the LEW strain. Resistance appeared to be linked to coat color (P < 0.001) rather than to major histocompatibility complex (MHC) type. Chronic stromal disease did not occur in survivors (DA, PVG, and hybrid strains only). Conclusions. The susceptibility of rat strains to infection of the cornea with HSV varies, and, as with mice, resistance seems to be controlled by non-MHC genes. Rats may prove useful for immunologic studies. Virus reactivation will be the subject of a future report.