Experimental influenza B viral myositis

Area of Science:

• Virology
• Pathology
• Immunology

Background:

• Influenza is a common viral infection.
• Influenza-associated myositis is a rare but recognized complication.
• The exact pathogenesis of influenza myositis remains unclear.

Purpose of the Study:

• To investigate the pathogenesis of influenza myositis.
• To determine if influenza B virus can infect skeletal muscle directly.
• To elucidate the mechanisms of muscle damage during influenza infection.

Main Methods:

• Intramuscular inoculation of BALB/c mice with influenza B/Lee virus.
• Monitoring of serum creatinine phosphokinase (CPK) levels.
• Histopathological examination of muscle tissue.
• Immunofluorescent staining for viral antigens.
• Virus isolation and detection of viral RNA using RT-PCR.

Main Results:

• Virus-inoculated mice showed significant increases in serum CPK levels.
• Influenza B virus infection led to muscle inflammation and degeneration in quadriceps muscles.
• Viral antigens were detected within muscle fiber nuclei and cytoplasm.
• Infectious virus titers decreased over time, suggesting limited viral replication.
• Control muscles and contralateral muscles showed no signs of infection or damage.

Conclusions:

• Influenza B virus can establish a non-permissive infection in murine skeletal muscle.
• The infection can damage muscle fibers, leading to degeneration and necrosis.
• These findings support the hypothesis that influenza virus directly infects muscle, causing myositis.
• A similar mechanism may underlie focal myositis observed in human influenza cases.