Prevention of Porcine Epidemic Diarrhea Virus With Nanotube-Adjuvanted Oral DNA Vaccines

Porcine epidemic diarrhea virus (PEDV) causes severe diarrhea in piglets. The ideal route of protection against PEDV for piglets is through passive (lactogenic) immunity, which is not provided by current inactivated and subunit vaccines on the market. In this study, we investigated whether a DNA vaccine encoding the full PEDV spike protein adjuvanted with cyclo-peptide nanotubes (cPNTs) can provide protection against PEDV through active and passive immunity. For the active immunization experiment, piglets were vaccinated, and the immune response was analyzed, followed by a PEDV challenge test. In a separate experiment, to evaluate the passive (lactogenic) immunity elicited by the cPNTs-adjuvanted DNA vaccine, pregnant sows in a local farm were immunized, and the survival of farrowed piglets was examined. The results showed that, in the active immunization experiment, the DNA vaccine elicited IFN-γ and IL-12 production in piglets. IgA antibodies were detected in the serum, and the expansion of CD4⁺ and CD8⁺ T cells was observed. Upon virus challenge, vaccinated piglets remained healthy, gained weight, and showed only mild signs of diarrhea, with minimal virus shedding (Ct value of 33, compared with 16 for the saline-vaccinated control group). For the passive immunity experiment, results show that the DNA vaccine administered orally induced higher levels of IgA in the colostrum of vaccinated sows compared to mock vaccination. The survival rate of the farrowed piglets was higher at 84% for the DNA-oral group compared to that of the mock vaccination group (68%). In conclusion, the cPNTs-adjuvanted DNA vaccine can not only generate protective immunity through direct immunization of piglets but also induce lactogenic immunity in pregnant sows to protect farrowed piglets from PEDV infection.