Viral expression in experimental canine distemper demyelinating encephalitis.

We have characterized the relationship between the expression of canine distemper virus (CDV) and demyelinating lesions in the white matter of the cerebellum of experimentally infected dogs. In animals which had demyelinating lesions, CDV proteins (N, P, F and H) were expressed and infectious virus could be recovered from brain tissue. Viral proteins (N, P, F and H) were detected by monoclonal antibodies and immunocytochemistry within demyelinating lesions as well as in scattered glial cells in areas of the white matter which lacked detectable lesions. Many cell types, including astrocytes, neurons, ependymal cells, choroid plexus cells, meningeal cells and perivascular inflammatory cells were labelled for viral antigen. We conclude from our results that the mechanism of demyelination in canine distemper virus-induced encephalitis involves expression of viral gene products at the lesion site.