Enterovirus 71 drives TLR2-NF-κB-dependent inflammatory skeletal muscle injury in neonatal BALB/c mice

Enterovirus 71 (EV-A71) can cause inflammatory injury beyond the central nervous system, yet the host pathways driving EV-A71-associated skeletal muscle pathology remain poorly defined. Toll-like receptor 2 (TLR2) is a key innate immune sensor capable of amplifying inflammatory signaling during infection. Here, we established an EV-A71 infection model in 1-day-old BALB/c suckling mice by intraperitoneal inoculation for 3 consecutive days and administered the TLR2 inhibitor C29 intraperitoneally at 6 h post-inoculation. EV-A71 infection induced prominent skeletal muscle pathology characterized by inflammatory cell infiltration, muscle bundle disruption, and dissolution, and reduced myofiber cross-sectional area. Consistently, EV-A71 increased the levels of TLR2, nuclear factor-κB (NF-κB) signaling markers (p65 and phosphorylated p65), the pro-inflammatory cytokine IL-6, and the viral protein VP1 in skeletal muscle. EV-A71 infection was also associated with elevated α-SMA and collagen III, suggesting tissue remodeling in injured muscle. Notably, pharmacological inhibition of TLR2 with C29 markedly alleviated histopathological damage and reduced IL-6 expression in skeletal muscle. Collectively, these findings support a model in which EV-A71 activates a TLR2-NF-κB-linked inflammatory program that contributes to skeletal muscle immunopathology and highlights TLR2 as a tractable host-directed target for mitigating virus-associated skeletal muscle injury.IMPORTANCEVirus-associated skeletal muscle injury can cause functional impairment and may worsen outcomes, but actionable host determinants remain limited. Using a neonatal mouse model, we show that enterovirus 71 (EV-A71) infection is accompanied by activation of a Toll-like receptor 2 (TLR2)-linked inflammatory program in skeletal muscle and that pharmacological TLR2 inhibition reduces IL-6 expression and alleviates muscle pathology. These results support the concept that excessive innate immune signaling contributes to muscle immunopathology and identify TLR2 as a potential host-directed intervention point. This work provides a mechanistic framework for understanding and targeting skeletal muscle injury associated with EV-A71 and potentially other viral infections.