Safety and Immunogenicity of a Novel Recombinant Newcastle Disease Virus Spotteddove-S Expressing the S Protein of Porcine Epidemic Diarrhea Virus Variant in Pigs

Porcine epidemic diarrhea virus (PEDV) is a porcine enteric coronavirus globally, especially since 2010, the variants have caused huge economic losses to the global pig industry. To develop a low-cost, antigen-stable vaccine against PEDV variants, we selected a lentogenic Newcastle disease virus (NDV) as a vaccine vector to express the S protein of the highly pathogenic PEDV variant, and its safety, protective efficacy and optimal immune route were evaluated in naive gilts. Our data uncovered that the recombinant NDV SpottedDove-S efficiently and stably expressed S protein in embryonated chicken eggs and cells. Additionally, the insertion of exogenous gene did not alter the pathogenicity of recombinant NDV to embryonated chicken eggs and chicks. Furthermore, NDV SpottedDove-S elicited potent anti-PEDV or anti-NDV neutralizing antibodies in mice. Importantly, the recombinant NDV SpottedDove-S exhibited safety in pigs, induced strong PEDV-specific antibodies and protected pigs from PEDV-typified symptoms, reduced virus shedding after PEDV challenge. Interestingly, Houhai acupoint (HA) immunization was more effective than intramuscular (IN) immunization in inducing serum antibody response and blocking viral shedding in pigs. These data indicate that NDV SpottedDove-S is a promising vaccine candidate against PEDV circulating in China, suggesting that the NDV vector platform has the potential to further develop other pig diseases.