THEILERS MURINE ENCEPHALOMYELITIS VIRUS-INDUCED CARDIAC AND SKELETAL-MUSCLE DISEASE

The DA strain of Theiler's murine encephalomycelitis virus, a member o f the cardiovirus genus of picornaviruses, induces a restricted and pe rsistent infection associated with a demyelinating process following i ntracerebral inoculation of mice; both virus infection and the immune response are believed to contribute to the late white matter disease. We now report that intraperitoneal inoculation with DA produces an acu te myositis that progresses to a chronic inflammatory muscle disease i n CD-1 mice as well as several inbred mouse strains. Some mouse strain s also develop central nervous system white matter disease and a focal myocarditis. Infections virus in skeletal muscle falls to undetectabl e levels 3 weeks postinoculation (p.i.), although viral genome persist s for at least 12 weeks p.i., the longest period of observation. Sever e combined immunodeficient animals have evidence of muscle pathology a s long as 5 weeks p.i., suggesting that DA virus is capable of inducin g chronic muscle disease in the absence of an immune response. The pre sence in immunocompetent mice, however, of prominent muscle inflammati on in the absence of infections virus suggests that the immune system also contributes to the pathology. T lymphocytes are the predominant c ell type infiltrating the skeletal muscle during the chronic disease. This murine model may further our understanding of virus-induced chron ic myositis and help to clarify the pathogenesis of human inflammatory myopathies.