IMMUNE-MEDIATED BRAIN ATROPHY - CD8-CELLS CONTRIBUTE TO TISSUE DESTRUCTION DURING BORNA-DISEASE( T)

Borna disease (BD) is a virus-induced immunopathologic disease of the central nervous system in a variety of species from birds to primates and probably in humans. Severe inflammatory reactions lead to tissue d estruction and finally to cortical brain atrophy. After experimental i nfection of the rat, intraparenchymal CD8(+) T cells, MHC class I Ags on Borna disease virus (BDV)-infected neurons, and numerous nerve cell lesions were present. Treatment of BDV-infected rats with the mAb OX- 8 directed against CD8(+) cells inhibited the immunopathologic reactio ns and reduced MHC class I Ag expression. Neuronal lesions were minima l and no loss of brain substance could be observed. Because BDV has no acute cytopathic effects, we provide evidence that the presence of CD 8(+) T cells within the brain parenchyma and the expression of MHC cla ss I Ags on neurons play a major role for immunopathologic brain tissu e destruction and virus-infected neurons in vivo can be destroyed by T cell-mediated cytotoxicity.