The pathogenesis of infectious avian encephalomyelitis. 2. The effect of immunosuppression on the disease

Normal chickens given infectious avian encephalomyelitis virus (IAEV) orally at 1, 7 or 14 days of age developed infectious avian encephalomyelitis (IAE), whereas those dosed with the virus at 21, 28 and 35 days of age did not. Chickens in all of these age groups that had been treated with cyclophosphamide or testosterone developed clinical IAE. Intraperitoneal inoculation of IAEV immunoglobulin at the time of dosing with the virus, or 48 hours later, protected normal and immunosuppressed chickens against the onset of clinical IAE. The titre of IAEV serum neutralising antibody was found to be lower in normal chickens given the virus at 1, 7 and 14 days of age in older chickens. These results suggest a significant role for the humoral immune system in the pathogenesis of IAE and in the development of immunity to the disease.