Evaluation of the Efficacy of a Recombinant Adenovirus Expressing the Spike Protein of Porcine Epidemic Diarrhea Virus in Pigs

Liu, Xinsheng; Zhao, Donghong; Zhou, Peng; Zhang, Yongguang; Wang, Yonglu

To assess the protective effect of the recombinant virus rAd-PEDV-S, pigs from all four groups (Table 1) were challenged orally with 1 × 10 5 TCID 50 highly virulent genotype GIIb PEDV strain CH/HNPJ/2017 at 28 dpv. All four groups of pigs were apparently healthy and had no clinical symptoms before the oral challenge. Fecal rectal swabs were collected from all piglets at 0 days post inoculation (dpi), and the results of real-time PCR confirmed that all piglets in each group were PEDV negative ( Table 2) . At 1 dpi, typical clinical signs of PEDV infection were observed in 1/5 pigs from the Ad-blank group and in 2/5 pigs from the PBS group, while no pigs from rAd-PEDV-S and inactivated vaccine groups developed clinical signs of PED ( Table 2 ). All pigs (5/5) from the Ad-blank and PBS groups developed severe diarrhea at 3 and 2 dpi, respectively, and then were euthanized after infection was confirmed by clinical symptoms and fecal viral shedding (Table 2) . Pigs in the rAd-PEDV-S and inactivated vaccine groups were PEDV positive and developed clinical signs of PED at 4 dpi (Table 2). Finally, in the rAd-PEDV-S and inactivated vaccine groups, 2/5 and 3/5 of pigs, respectively, were protected during the observation period. Notably, compared with the Ad-blank and PBS groups, the rAd-PEDV-S and inactivated vaccine groups displayed obviously delayed virus shedding and clinical signs of PED in pigs (Table 2) . erefore, rAd-PEDV-S provides only partial protection against the highly virulent PEDV challenge, which was as effective as that of the commercial inactivated vaccine.