An attractive vaccine candidate based on AP205 VLPs fusing with a receptor-binding domain of a newly emerged porcine deltacoronavirus strain in China.

Emerging swine enteric coronaviruses (SeCoV) pose significant threats to global pork security, with zoonotic porcine deltacoronavirus (PDCoV) demonstrating cross-species transmission potential. Here, we identified a new PDCoV strain, CHN/GD/2023, which was isolated from porcine intestinal epithelium, showing phylogenetic clustering with China-endemic variants through viral spike (S) protein evolutionary tracing. A vaccine candidate for PDCoV was produced by genetically fusing the receptor-binding domain (RBD) of CHN/GD/2023 to the C-terminus of the AP205 gene. The purified AP205-RBD successfully displayed RBD on and exhibited a spherical nanoparticle structure packaging nucleic acid inside particles. Furthermore, AP205-RBD generate high level of RBD-specific IgG antibodies, neutralizing PDCoV, and concurrently enhancing both CD4+ and CD8+ T-cell responses compared to controls, which has the potential to be produced at large scale for immunization programs.