Histopathology in Coronavirus-Induced Demyelination

The experimental model system of coronavirus mouse hepatitis virus (MHV) induced demyelination in 4–6 week old C57Bl/6 or Balb/c mice exhibits a biphasic disease and two distinct forms of virus-induced demyelination. During the acute phase of the disease MHV infection causes acute encephalitis, and some strains of virus cause also hepatitis. Infection with the JHM strain of MHV causes severe panencephalitis, whereas MHV-A59 causes mild to moderate encephalitis involving specific limbic and limbic related areas of the brain and brain stem. The target cells are neurons and glia including oligodendrocytes. Demyelination during the acute stage is due to cytolytic infection of oligodendrocytes. After two weeks, the disease process enters a chronic stage of immune-mediated demyelination, in the presence of high levels of anti-viral antibodies and persistent low levels viral RNA in glial cells, without detectable levels of infectious virus or viral antigens.