Immunogenicity and protective efficacy of recombinant adenovirus expressing a novel genotype G2b PEDV spike protein in protecting newborn piglets against PEDV

Abstract

Porcine epidemic diarrhea (PED) is a highly infectious and economically significant gastrointestinal disorder that affects pigs of all ages. Preventing and controlling PED is achieved by immunizing sows with vaccines, enabling passive piglet immunization via colostrum. The prevalence of G2b porcine epidemic diarrhea virus (PEDV) continues in China despite the use of commercial vaccines, raising questions regarding current vaccine efficacy and the need for novel vaccine development. Adenovirus serotype 5 (Ad5) has several advantages, including high transduction efficiency, a wide range of host cells, and the ability to infect cells at various stages. In this study, we expressed the immunogenic proteins of spike (S) using an Ad5 vector and generated a PED vaccine candidate by inducing significant humoral immunity. The rAd5-PEDV-S prevented PED-induced weight loss, diarrhea, and intestinal damage in piglets. This novel vaccine candidate strain possesses the potential for use in the pig breeding industry.

Keywords: G2b genotype; S protein; adenoviral vector; immune efficacy; porcine epidemic diarrhea virus; protective efficacy.

Fig 1

Construction and identification of rAd5-PEDV-S. (A) Ad-related cytopathic effect (CPE) caused by rAd5-PEDV-S in HEK293 cells. The left figure represents CPE caused by rAd5-PEDV-S, right represents normal cells. (B) The genetic stability of rAd5-PEDV-S in HEK293 cells was detected by PCR, “P” means passage. “+” means positive control, “-” means negative control. (C) Western blotting analysis of S protein expressed by rAd5-PEDV-S in HEK293 cells. (D)Immunofluorescence assay (IFA) analysis of S protein expressed by rAd5-PEDV-S in HEK293 cells.

Fig 2

Humoral immune responses of rAd5-PEDV-S in sows. (A) Schematic representation of the immunization procedure. These sows being immunized with a primary immunization at 5 weeks before farrowing and a secondary immunization with the same dose irradiated 2 weeks before farrowing and immunized only once each at 5 weeks before or 2 weeks before farrowing. (B) IgA antibody titers in colostrum. (C) IgG antibody titers in serum. (D) NAb titers in colostrum assay in Vero cells. (E) NAb titers in serum assay in Vero cells. (Data were analyzed by Tukey’s multiple comparison test for subsequent analysis. Each point represents the titer of an individual. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, no significance).

Fig 3

Clinical symptom of PED-infected piglets. (A) Diarrhea scores of PED-infected piglets. (B) Daily gain of PED-infected piglets. (C) PEDV genomic RNA copies of PED-infected piglets. (D) Survival rate of PED-infected piglets. (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, no significant).

Fig 4

Pathological analysis of PED-infected piglets. The ileum of each pig was collected and stained with hematoxylin and eosin and examined using light microscopy.