Neuron-glia interactions in the rat retina infected by Borna disease virus

Neuron-glia interactions in the Borna disease virus (BDV)-infected rat reti na were investigated with emphasis on the ultrastructural characterization of degenerative alterations in the ganglion cell and photoreceptor layer. I mmuno- and cytochemical techniques were applied to label microglia, macroph ages and Muller (macroglial) cells. Four weeks after intracerebral infectio n of adult rats, the total thickness of the retina was considerably diminis hed, primarily due to the loss of photoreceptor segments and ganglion cells . A gradual reduction of both plexiform layers was also observed. There was a remarkable increase in the number of microglial cells, predominantly in the ganglion cell and the inner plexiform layers. Ultrastructural analysis confirmed that microglia, but also macrophages, were involved in phagocytos is accompanying severe neuronal degeneration in the ganglion cell and the p hotoreceptor layer. In contrast, Muller cells showed moderate morphological and cytochemical alterations, indicating that Muller cells play only a min or role in early stages of BDV-induced retinitis. Monitoring neuron-glia in teractions in BDV-induced retinopathy, combined with the application of dif ferent protocols of immunosuppression effecting the BDV virus and/or the mi croglia, might help to establish specific strategies to suppress BDV-induce d neuronal degeneration.