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

Area of Science:

• Virology
• Immunology
• Neurology

Background:

• The cause of human polymyositis (PM) is unknown.
• Group B coxsackieviruses (CVB) are suspected contributors to PM pathogenesis.
• A specific strain, coxsackievirus type 1 (CVB 1), induces a PM-like condition in mice.

Purpose of the Study:

• To investigate the role of active coxsackievirus type 1 (CVB 1) in inducing inflammatory myositis.
• To establish the necessity of active virus in the pathogenesis of CVB 1-induced murine polymyositis (PM).

Main Methods:

• Neonatal Swiss mice were infected with active or inactivated CVB 1.
• Viral replication and titers in muscle tissue were monitored.
• Histological examination assessed myonecrosis and chronic inflammation.
• Antibody responses to CVB 1 were analyzed.

Main Results:

• Active CVB 1 replicated to high titers in muscle, causing acute myonecrosis.
• Viral presence peaked at Day 7 and became undetectable after Day 14.
• Despite myocyte regeneration, chronic inflammatory myositis developed by Day 14 and persisted.
• Inactivated virus did not cause disease, but induced anti-CVB 1 antibodies.
• Anti-CVB 1 antibodies were present in both active and inactivated virus groups.

Conclusions:

• Active CVB 1 infection is essential for inducing inflammatory myositis in mice.
• This murine model closely resembles human polymyositis (PM).
• The findings highlight the etiological role of active CVB 1 in PM pathogenesis.