Infection of cultured human muscle cells by influenza virus.

In a search for myotropic viruses with a potential to initiate muscle autoimmunity, we found that two strains of influenza A virus, A/England/863/78 (H3N2) and the reassortant virus X-47 (H3N2), could infect human syncytial myotubes lytically. The X-47 strain could, in addition, infect unicellular precursor myoblasts. Intracellular viral protein synthesis was demonstrated by pulse-labelling studies in both cell types with both virus strains. By immunofluorescence and immunoelectron microscopy, viral antigens were demonstrated in infected muscle cells specifically identified by double staining with monoclonal antibodies to either of two independent muscle-specific antigens. However, using 'co-capping' techniques in conjunction with electron microscopy, there was no evidence of association between viral haemagglutinin and the acetylcholine receptor (one major target of autoimmunity to muscle cells) on the infected cell membrane.