Borna disease virus-induced retinitis in Lewis rats--an immune-mediated retinopathy.

Borna disease virus (BDV) infection, naturally occurring in horses and sheep induces a mononuclear retinitis and meningoencephalitis in adult Lewis rats. In the pathogenesis a virus-specific cell mediated immune reaction presumably of delayed hypersensitivity type is operative. Corresponding to the encephalitic lesions a progressive retinitis with loss of the first and second retinal neuron develops. The inflammatory response is characterized by predominance of macrophages in the early phase of infection followed by distinct plasmacellular infiltration. Immunosuppressed and immuno-incompetent rats do not develop retinal lesions after intracerebral inoculation. Thus similar as in the brain probably virus specific immunopathological reactions play a crucial role in the pathogenesis of BDV-induced retinitis in Lewis rats.