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Porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus, causes diarrhea in piglets and possesses the potential to infect humans. However, there are no commercially available vaccines for PDCoV.
Methods: In this study, the immune responses to the spike protein and receptor-binding domain trimer were examined in mice.
Results: Neutralization assays and flow cytometry analysis demonstrated that spike protein elicited more robust neutralizing antibodies and cellular immune responses than the receptor-binding domain trimer. Spike protein and inactivated vaccine were used in the assessment of immunogenicity in piglets and sows. Immunized piglets, sows, and suckling pig showed high neutralizing antibody titers and spike-specific sIgA in colostrum, milk, and serum. The piglets/suckling pig from the immunized group displayed significantly fewer microscopic lesions in the intestinal tissue, with only one or no piglet showing mild diarrhea. However, all piglets/suckling pig showed mild to watery diarrhea and exhibited a high level of viral shedding in the challenged control group. The feces from the piglets/suckling pig in the spike protein and inactivated vaccine group exhibited reduced viral load. Of note, vaccine-elicited neutralizing antibodies last for more than 4 months in immunized piglets.
Conclusion: Together, our data demonstrate for the first time the protective efficacy of spike-based subunit vaccine, which could be a candidate vaccine against PDCoV.
Li J, Zhao S, Zhang B, et al. A novel recombinant S-based subunit vaccine induces protective immunity against porcine deltacoronavirus challenge in piglets. J Virol. 2023; e0095823. doi:10.1128/jvi.00958-23