Efficacy of inactivated variant porcine epidemic diarrhea virus vaccines in growing pigs

Lee, Seung Heon; Yang, Dong-Kun; Kim, Ha-Hyun; Cho, In-Soo

All growing pigs were apparently healthy and had no clinical symptoms before oral challenge. The protective efficacy of the experimental vaccines against challenge with virulent homologous virus (10 4.0 TCID50/mL PEDV QIAP1401-p11) was determined by the absence of clinical signs and decreased viral shedding during the 15-day observation period. Viral shedding in feces was determined using a commercial rRT-PCR kit. All pigs in the non-vaccinated control (NVC) group exhibited early signs of disease, typically mild diarrhea and loss of appetite (mean clinical score ≤1.0) after 2 dpc and experienced severe watery diarrhea with vomiting thereafter (mean clinical score ≤1.75) (Fig. 2A) . The IMS1313-and IMSgel-adjuvanted vaccine groups exhibited a similar clinical presentation to that of the NVC group. In contrast, the ISA206-adjuvanted vaccine group exhibited weaker and delayed clinical signs, mainly mild diarrhea (mean clinical score ≤1.0). In the ISA201 vaccine group, clinical disease progression was slow, and clinical severity was relatively weak, compared with the NVC group, but watery diarrhea eventually developed. Viral shedding was defined as the presence of PEDV RNA as detected by rRT-PCR. PEDV shedding in feces in all groups was generally accompanied by clinical signs of disease (Fig. 2B) . PEDV RNA was first detected in one of four pigs in the IMS1313, IMSgel, and NVC groups at 3 dpc. The duration of viral shedding differed among the groups. In the ISA206 and ISA201 groups, viral shedding in feces continued for 3 and 6 days, respectively. In contrast, in the other vaccinated groups and in the NVC group, viral shedding in feces was observed until the end of the challenge experiment. The viral shedding rates differed significantly among the groups (number of pigs with PEDV/total number of fecal samples) at both 6 and 9 dpc (p<0.05).