Immunological and pathological findings in demyelinating encephalitis associated with canine distemper virus infection.

Nine dogs with canine distemper encephalitis (CDE) were examined with immunological techniques including demonstration of antibodies against canine distemper virus (CDV) in the serum and against myelin basic protein (MBP) in serum and in CSF. Mitogen stimulation tests of lymphocytes were also done. The brains were examined pathologically and immunoglobulin and C3 were demonstrated in lesions by means of immunohistological techniques. Six dogs with acute CDE had none or low antibody levels against CDV or MBP, and there was no immunoglobulin in demyelinating lesions. Some of these dogs had depressed lymphocyte mitogen responses. Two dogs with chronic CDE showed recovery of lymphocyte mitogen responses. One of these had a significant antibody response against CDV and MBP in the serum. Both dogs with chronic CDE had very high antibody titers against MBP in the CSF and demyelinating lesions contained immunoglobulin. These results suggest that acute demyelination in CDE is probably due to some direct viral activity and that the progression of demyelination in chronic CDE is associated with a local immune response.