A novel virus-like particles vaccine induces broad immune protective against deltacoronavirus in piglets

Coronaviruses (CoVs) comprise a group of important human and animal pathogens that threaten public health because of their interspecies transmission potential to humans. However, virus-like particles (VLPs) constitute versatile tools in CoVs vaccine development due to their favorable immunological characteristics. Here, we engineered the VLPs composed of the spike (S), membrane (M), and envelope (E) structural proteins of the Porcine deltacoronavirus (PDCoV) and examined their immune responses in mice. Neutralization assays and flow Cytometry demonstrated that PDCoV VLPs induced highly robust neutralizing antibodies (NAbs) and elicited cellular immunity. To assess the protective efficacy of VLPs in newborn piglets, pregnant sows received vaccinations with either a PDCoV-inactivated vaccine or VLPs at 40 and 20 days before delivery. Five days post-farrowing, piglets were orally challenged with the PDCoV strain. Severe diarrhea, high viral RNA copies, and substantial intestinal villus atrophy were detected in piglets born to unimmunized sows. However, piglets from sows immunized with VLPs exhibited high NAbs titers and markedly reduced microscopic damage to the intestinal tissues, with no piglet showing diarrhea. Hence, the results indicate that the VLPs are a potential clinical candidate for PDCoV vaccination, while the strategy may serve as a platform for developing other coronavirus vaccines.