Generation and protective efficacy of a cold-adapted attenuated genotype 2b porcine epidemic diarrhea virus

Won, Hokeun; Lee, Dong-Uk; Jang, Guehwan; Noh, Yun-Hee; Lee, Seung-Chul; Choi, Hwan-Won; Yoon, In-Joong; Yoo, Han Sang; Lee, Changhee

Swine vaccination and challenge experiments were conducted with a total of 6 commercial crossbred pregnant sows (Great Yorkshire × Dutch Landrace) with the same parity and expected farrowing date. Animals were allocated randomly into three experimental groups: vaccinated group 1 (n = 3), challenge control group 2 (n = 2), and strict negative control group 3 (n = 1). A multiple-dose PED homologous vaccination schedule at 2-week intervals starting prior to farrowing was applied in the present protection study. Three sows in group 1 were orally administered twice with a 1 mL dose of the Aram-P29-CA with 10 4.5 TCID 50 /mL at 4 and 2 weeks pre-partum. The remaining sows in groups 2 and 3 were unvaccinated and served as controls. All sows were monitored daily for clinical alterations and adverse effects following vaccination. To mimic the field conditions of nursing piglets, all sows were allowed to farrow naturally and nurse their piglets freely for the duration of the study. Ten 4-day-old suckling piglets per litter (a total of 50 newborn piglets) in groups 1 and 2 were challenged orally with a 1 mL dose of 10 4.0 TCID 50 /mL of virulent Aram-P5 virus. The sham-inoculated piglets from group 3 were administered with cell culture medium as a placebo. Animals were observed daily for clinical signs, including vomiting, diarrhea, and mortality. Fecal specimens were taken from all groups and examined for PEDV shedding as described above. A CSS was determined for 7 days postchallenge (DPC) as described above. Blood samples were collected from sows before (at each vaccination), at, after farrowing (up to 2 weeks) and also from 5 representative piglets per litter from each dam at 0 and 7 DPC. Colostrum was collected at the day of farrowing.