Construction and Immunogenicity Evaluation of a Ferritin-Based Nanoparticle Vaccine Displaying the PDCoV Spike Receptor-Binding Domain

Porcine deltacoronavirus (PDCoV) poses a significant threat to the global swine industry, underscoring the urgent need for effective vaccines. In this study, a self-assembling ferritin-based nanoparticle vaccine displaying the PDCoV spike receptor-binding domain (S-RBD), designated PDCoV-S-RBD-FR, was constructed and evaluated for its immunogenicity and safety. Transmission electron microscopy (TEM) showed that the recombinant PDCoV-S-RBD-FR protein formed spherical nanoparticles with a mean diameter of 25.55 ± 4.39 nm. In mice, immunization with PDCoV-S-RBD-FR elicited antigen-specific IgG responses, with titers reaching 1:40,960 following booster immunization. Significantly elevated serum IFN-γ and IL-4 levels were observed following immunization. Notably, virus neutralization assays demonstrated that the vaccine induced functional neutralizing antibodies (titer 1:128) capable of effectively blocking PDCoV-induced cytopathic effects in vitro. Histopathological examination of the heart, liver, spleen, lungs, and kidneys revealed no significant lesions in immunized mice relative to the PBS control group, suggesting good tolerability in mice. Collectively, these findings indicate that the ferritin-based PDCoV-S-RBD nanoparticle vaccine elicits antigen-specific IgG responses together with elevated serum cytokine levels and functional neutralizing activity in vitro and no detectable histopathological alterations in major organs, supporting its further evaluation as a vaccine candidate against PDCoV.