Immunogenicity of recombinant porcine parainfluenza virus 5 expressing the spike protein of porcine epidemic diarrhea virus.

The porcine epidemic diarrhea virus (PEDV) induces severe diarrhea in neonatal piglets, often resulting in high mortality rates. Consequently, the development of effective and safe vaccines is a critical priority for controlling PEDV infection. Vaccines vectored by the parainfluenza virus 5 (PIV5) exhibit distinct advantages in terms of safety, genomic stability, and immunogenicity. In this study, two novel porcine-origin PIV5 strains (PIV5-HuB and PIV5-DP1-1) were isolated from pigs in China, and their whole-genome sequences and phylogenetic relationships were analyzed. Subsequently, the PIV5-HuB strain, which exhibited superior growth characteristics, was selected for the construction of infectious clones and a reporter virus. Furthermore, the recombinant PIV5 expressing the full-length spike (S) protein of G2a subtype PEDV was developed, and its immunogenicity was evaluated in murine models. Immunization with the recombinant rPIV5-PEDV-S in mice elicited robust PEDV-specific IgG in serum, secretory IgA (sIgA) in bronchoalveolar lavage fluid (BALF), and neutralizing antibody responses against PEDV G2a, G1b, and G2c subtypes. Additionally, the recombinant rPIV5-PEDV-S enhanced PEDV-specific lymphocyte proliferation and increased the proportions of CD3+CD8+ T cells and CD3+CD4+ T cells. This study provides evidence supporting the potential of PIV5 as a vaccine delivery vector for enteric viral diseases in swine.