Neurotropism and interferon-dominated immune responses in a mouse-adapted coxsackievirus A16 infection model.

The development of animal models infected with Coxsackievirus A16 (CVA16) is limited by insufficient neurovirulence, which hinders the study of pathogenesis mechanisms and antiviral drug evaluation. Therefore, we aimed to develop a neonatal ICR mouse model for CVA16 infection, wherein infected brain tissue was continuously passaged from 2-day-old ICR suckling mice, resulting in a highly neurovirulent mouse-adapted strain (CVA16-P5) to establish optimal infection conditions for antiviral assessment. By systematically optimizing viral dose, inoculation route, and age at infection, we defined conditions that reproducibly induced progressive neurological disease and multisystem involvement. Infection with the CVA16-P5 strain resulted in consistent pathological alterations across multiple tissues, accompanied by characteristic neurological manifestations. Transcriptomic analysis of neural tissues revealed tissue-specific interferon-dominated immune responses and signatures of systemic viral dissemination that recapitulate key features of severe human infection. Whole-genome sequencing identified a nonsynonymous mutation in the VP1 capsid protein associated with enhanced neurovirulence during mouse adaptation. Overall, this CVA16-P5-adapted strain infection model provides a robust experimental platform for investigating CVA16 pathogenesis and for the preclinical evaluation of vaccines and antiviral drugs against neurotropic enteroviruses. IMPORTANCE: The lack of animal models that reliably recapitulate the neurological manifestations of Coxsackievirus A16 infection has constrained progress in understanding CVA16 neuropathogenesis. Here, we describe a neonatal mouse model based on a mouse-adapted CVA16 strain (CVA16-P5) that consistently induces neurological disease and multisystem pathology. This model enables the analysis of tissue-specific immune responses, viral dissemination, and genetic determinants of neurovirulence, including a VP1 mutation associated with enhanced pathogenicity. By providing a reproducible and physiologically relevant system for studying severe CVA16 infection, the CVA16-P5-adapted strain infection model setup in this study supports mechanistic studies of CVA16 pathogenesis and facilitates the preclinical evaluation of vaccines and antiviral drugs against neurotropic enteroviruses.