Intranuclear inclusion bodies in the brain of guinea-pigs infected with louping ill virus with special reference to the effect of treatment with cyclophosphamide.

Eosinophilic, intranuclear inclusion bodies are described in the brains of guinea-pigs after intracerebral inoculation with louping ill virus. The incidence of the inclusion bodies was considerably increased by following virus inoculation with immunosuppression effected by cyclophosphamide. Length of survival time and degree of pathological change also played some part in the aetiology of the inclusion bodies. Allergic encephalitis or quaranfil viral encephalitis were induced in other guinea-pigs with or without a period of immunosuppression but the brains did not yield inclusion bodies. It seemed that for a high incidence of inclusion bodies treatment with both louping ill virus and cyclophosphamide was needed. No viral antigen was detected in the inclusions by the fluorescent antibody technique.