PRESENCE OF CD4-CELLS AND EXPRESSION OF MHC CLASS-I AND MHC CLASS-II ANTIGEN IN HORSES WITH BORNA-DISEASE VIRUS-INDUCED ENCEPHALITIS( AND CD8+ T)

Tissues from 9 horses and 1 donkey suffering from natural Borna diseas e were investigated immunomorphologically. Lymphocytic inflammatory re actions and increased expressions of MHC class I and class II antigen were found in the brain as well as in the trigeminal and olfactory sys tem. Perivascular inflammatory infiltrates were dominated by CD4+ T ce lls, whereas the majority of CD8+ T cells were disseminated intraparen chymally. No evidence of inflammation was found in the retina. Borna d isease virus proteins and nucleic acids were present in the hippocampu s, thalamus and medulla oblongata in all 10 animals, in the cerebral c ortex, retina, trigeminal ganglion and nerve in 9, in the olfactory ep ithelium in 6 and in roots and proximal parts of large peripheral nerv es in 3. No evidence of infection was found in the autonomic nervous s ystem, lung, heart, liver, kidney or gut. BDV- proteins and nucleic ac ids were even more abundant in the trigeminal system than in the olfac tory system, suggesting that infection may have occured via the trigem inal nerve.