Behavioral disease in rats caused by immunopathological responses to persistent borna virus in the brain.

Borna virus replicated persistently in the brains of rats, causing frenzied and apathetic behavioral states in sequence but no mortality. The transient frenzied behavior was caused by an immune-mediated, cytolytic, encephalitic response that was unexpectedly self-limiting. Cessation of active pathological processes coincided with the onset of the passive phase of the disease. This study thus demonstrates suppression of virus-specific inflammation despite continuous viral replication and describes a new mechanism by which chronic encephalitis may become established.