Elucidating the role of human skeletal muscles in the pathogenesis of enterovirus D68 infection.

Enterovirus D68 (EV-D68) is an emerging respiratory virus associated with extra-respiratory complications, especially acute flaccid myelitis. However, the pathogenesis of acute flaccid myelitis is not fully understood. It is hypothesised that through infection of skeletal muscles, the virus further infects motor neurons via the neuromuscular junction. We hypothesise that EV-D68 infection of human skeletal muscles can impair muscle function directly, thereby contributing to the development of EV-D68-associated muscle weakness. Here, we inoculated human induced pluripotent stem cell-derived skeletal muscle myotubes grown in 2D and 3D with different EV-D68 isolates, which resulted in a productive infection and cell death. We showed through neuraminidase treatment that sialic acids facilitate infection of these cells. EV-D68 infection of the 3D model led to tissue damage, reduction of contractile force, and hampered muscle regeneration. Altogether, we showed that human skeletal muscle can act as an extra-respiratory replication site and infection of skeletal muscles may contribute to EV-D68-associated muscle weakness.