INDUCED RESISTANCE OF THE CENTRAL NERVOUS SYSTEM TO EXPERIMENTAL INFECTION WITH EQUINE ENCEPHALOMYELITIS VIRUS : I. NEUTRALIZING ANTIBODY IN THE CENTRAL NERVOUS SYSTEM IN RELATION TO CEREBRAL RESISTANCE.

1. Neutralizing antibody to equine encephalomyelitis virus was found in the spinal fluid of rabbits sufficiently vaccinated with active or formalin-inactivated virus. Antibody was specific for the Western or for the Eastern virus. 2. Neutralizing capacity of spinal fluid was equivalent to that of a 1/300 dilution of serum of the same animal, and was of the same order of magnitude as that of perfused brain of a vaccinated animal. 3. Vaccinated rabbits which showed antibody in the spinal fluid resisted intracerebral or intracisternal injection of active virus. This immunity was specific, i.e., there was no cross-reaction between the Eastern and Western virus after vaccination with formalin-inactivated virus. On the other hand, lack of antibody in the spinal fluid, even when antibody was demonstrable in the undiluted serum, was associated with lack of cerebral resistance.