Chronic relapsing experimental allergic encephalomyelitis: CNS plaque development in unsuppressed and suppressed animals.

Central nervous system (CNS) lesion morphology has been studied in inbred Strain 13 guinea pigs sensitized for chronic relapsing EAE in which the disease was either left to develop (unsuppressed) or was suppressed with injections containing myelin basic protein (MBP). Pathologic changes correlated well with clinical activity. In unsuppressed chronic EAE animals, active clinical disease was invariably matched by acute inflammation in the CNS. In more chronic states, the CNS displayed fibrosis and remyelination while relapses showed the CNS to contain recent changes superimposed upon old lesions. In animals in which the disease was suppressed by injections of MBP, clinical signs did not develop. However, some early subclinical changes were seen morphologically. These lesions were able to remyelinate early on and there was no progression in lesion formation. Apparently, therefore, MBP had a beneficial effect upon the course of the disease and had promoted structural repair. It thus appears that MBP therapy might be one effective approach for the prevention of chronic relapsing EAE. The findings should prove relevant to future MBP trials in multiple sclerosis.