Evaluating the antiviral effects of polygonum cuspidatum nanoparticles against enterovirus 71 in vitro and in vivo

Enterovirus 71 (EV71) is a major causative agent of hand, foot, and mouth disease (HFMD) and is associated with severe neurological complications in young children. However, effective antiviral therapeutics remain limited. In this study, nanoparticles derived from Polygonum cuspidatum (NPC) were prepared and their antiviral activity against EV71 was evaluated in vitro and in vivo. Cytotoxicity and antiviral assays in human rhabdomyosarcoma (RD) cells demonstrated that NPC exhibited substantially lower cytotoxicity than the crude extract while maintaining comparable antiviral potency against EV71. NPC treatment markedly reduced EV71-induced cytopathic effects and significantly decreased viral RNA levels, as confirmed by indirect immunofluorescence and RT-qPCR. In an EV71-infected ICR suckling mouse model, oral administration of NPC significantly improved survival, attenuated clinical disease scores and body weight loss, and reduced viral loads in muscle and brain tissues in a dose-dependent manner. Histopathological analysis revealed alleviated tissue injury in the NPC-treated mice. These findings suggest that nanonization improves the therapeutic index of P. cuspidatum and support further investigation of NPC as a potential plant-derived antiviral candidate for EV71 infection.