A novel cross-species vaccine design and nasal immunization strategy based on recombinant Lactiplantibacillus plantarum expressing PEDV tS1.

Porcine epidemic diarrhea (PED) is a highly lethal and airborne disease in neonatal piglets that has caused significant economic losses in the pig industry over the last three decades. Despite the widespread implementation of commercial vaccines, the disease continues to exhibit recurrent outbreaks, primarily owing to suboptimal immunization efficacy. In this study, we engineered recombinant Lactiplantibacillus plantarum LP12:PEDV tS1, which expresses the truncated S1 domain of the porcine epidemic diarrhea virus (PEDV) spike protein through a surface anchoring mechanism. The expression was confirmed using western blotting, flow cytometry, and indirect immunofluorescence assays, with a maximum protein yield of 1.7657 μg per 1×109 CFU. Furthermore, we immunized mice and pigs nasally with LP12:PEDV tS1 separately. Immunization elicited robust mucosal immune responses, as evidenced by a significant increase in specific secretory IgA (sIgA) with neutralizing activity in alveolar lavage fluid and fecal samples. Our results also indicated that LP12:PEDV tS1 activated dendritic cells in the mesenteric lymph nodes of mice, marked by notable upregulation of CD80 and CD86. Successive immunization with LP12:PEDV tS1 protected piglets from PEDV infection and elicited comparable mucosal immune responses across species, demonstrating its strong potential as a PEDV vaccine candidate. Moreover, an intranasal immunization strategy based on recombinant Lactiplantibacillus plantarum demonstrated suitability for cross-species vaccination between mice and piglets, potentially streamlining the preclinical evaluation process.IMPORTANCEPorcine epidemic diarrhea (PED) is a major cause of piglet mortality. Current control relies on vaccinating pregnant sows with inactivated or attenuated viruses. However, not all sows develop sufficient antibodies to protect piglets. Once piglets are infected, no effective emergency vaccines are available for them, as existing options pose biosafety risks. To address this, we developed a subunit mucosal vaccine using recombinant Lactiplantibacillus plantarum. This vaccine is cost-effective, enables cross-species immunization, and remarkably provides immediate immunity to prevent viral infection in neonatal piglets.