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

Next, animal inoculation experiments were performed to examine the in vivo phenotypic alterations associated with serial in vitro passage at low temperatures (a cold adaption tool for virus attenuation) of the virulent Aram strain. The pathogenicity of the parental Aram-P5 and its cold-adapted derivative, Aram-P29-CA, was characterized in pigs. Twelve piglets divided into three groups of four animals each were challenged orally with parental Aram-P5 (group 1) or cold-adapted Aram-P29-CA (group 2), and the remaining piglets in a control group received cell culture medium. Clinical signs were recorded daily, and fecal swabs were collected pre-and post-challenge for the duration of the study. During the acclimation period, all piglets were active, showed no clinical symptoms, and had normal fecal consistency that did not contain any PEDV genetic material. After the challenge, none of the negative-control piglets developed clinical presentations typical of PEDV throughout the study. In contrast, Aram-P5-challenged piglets (group 1) displayed clinical signs including loss of appetite and diarrheic feces by 1 DPI (mean CSS ± SDM of 0.67 ± 1.15) and underwent lethal watery diarrhea with vomiting thereafter (mean CSS of > 3.0) (Fig. 6A) . All the inoculated animals in group 1 finally died by 5 DPI. Remarkably, the cold-adapted Aram-P29-CA virus-inoculated piglets in group 2 experienced neither PEDV-related clinical symptoms nor mortality throughout the experiment.