Pathogenicity of a vaccine strain of vaccina virus in rabbits administered by intravenous route.

The pathogenicity of the Lister (Elstree) strain, a vaccinia virus, in rabbits after intravenous injection was studied by histopathological and immunofluorescent methods. Inoculation of 1 X 10(7) PFU (pock-forming unit) virus into weanling and young adult rabbits caused severe emaciation and high mortality within 2 weeks. Pathological findings were characterized by vesicular lesions along muco-cutaneous junction areas of the eyes, nose and mouth and by inflammatory changes in the brain, mainly in the meninges and choroid plexus. Immunofluorescent staining of the tissues of animals sacrificed at intervals demonstrated the accumulation of vaccinia viral antigen (s) in the loci of pathological changes. The suitability of this model system for the study of pathogenesis of human postvaccinal meningoencephalitis is discussed.