Coxsackievirus B 1 induced murine polymyositis: acute infection with active virus is required for myositis.

Although the etiology of human polymyositis (PM) remains obscure, group B coxsackieviruses (CVB) have been implicated in disease pathogenesis and a particular strain of type 1 CVB (CVB 1) has been shown to cause in mice an inflammatory myositis which is similar to human PM. After infection of neonatal Swiss mice with active CVB 1, virus replicated to high titers in muscle and produced acute myonecrosis. Viral titers peaked in muscle at Day 7 and virus was undetectable after Day 14. Myocytes regenerated, but a chronic inflammatory myositis, involving principally proximal muscle groups of the hind limbs, was observed by Day 14 and persisted through at least Day 70. Injection of inactivated virus resulted in no clinical or histological disease. Anti-CVB 1 antibody was demonstrated in mice injected with inactivated or active virus pools. This report establishes the need for active virus in the pathogenesis of CVB 1 induced murine PM.