Ferritin-displayed engineered sCAR1 nanoparticles as a receptor-decoy antiviral strategy against Coxsackievirus B-associated inflammation

Coxsackievirus Group B (CVB) remains an important cause of severe disease in infants and young children, including viral myocarditis and meningitis, yet no licensed vaccine or virus-specific antiviral therapy is currently available. Here, we engineered soluble Coxsackievirus and adenovirus receptor (CAR) ectodomains and displayed the optimized receptor decoy on ferritin nanoparticles to generate a potent anti-CVB3 entry inhibitor. Wild-type soluble CAR ectodomains neutralized CVB3 but were limited by homodimerization and by residual binding to endogenous CAR/JAML, which was associated with dose-dependent mitogenic activity. Guided by structural information, we introduced mutations that abolished dimerization and CAR/JAML binding while preserving, and further improving, viral neutralization. Ferritin display of the optimized sCAR1 mutant enhanced multivalent presentation, systemic persistence, and tissue delivery. The resulting sCAR1 Mu+Ferritin nanoparticle achieved IC50 values of 413 ng/mL in Vero cells and 140 ng/mL in SH-SY5Y cells. In neonatal BALB/c mice, prophylactic administration of sCAR1 Mu+Ferritin (200 μg, 6 h before challenge) conferred 68.75% protection against lethal CVB3 infection (103.5 CCID50), reduced viral burden in the liver, spleen, brain, and heart, and alleviated myocarditis and neuroinflammation without sustained cytokine activation. Cross-neutralizing activity against CVB1 further supports the breadth of this receptor-based platform. These findings identify ferritin-displayed engineered CAR nanoparticles as a safety-optimized and mutation-resilient antiviral strategy for CVB infections.