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

In South Korea, a number of modified live virus (MLV) vaccines for classical G1a PEDV came to be widely used throughout the country; however, they were incapable of controlling the impact of the recent massive G2b outbreaks in the domestic swine industry because of limited cross-protection between two genetic clusters [1, 2, 4, 18] . Considering this efficacy issue, there is a high priority for the development of a next-generation MLV vaccine against G2b epizootic or related strains prevalent in the field, which can replicate to high titer in the gut and also boost lactogenic immune responses without giving rise to clinical illnesses. In general, the attenuated virus utilized to prepare the MLV vaccine can be achieved by traditional cell culture adaptation procedures of the virulent wild-type virus in non-host cell lines, but this process is impeded by difficulties in performing laboratory procedures, such as numerous time-consuming, and repetitive passages in non-host cell lines. In contrast, adaptation to growth at low (< 37°C) temperatures by short-term serial passages in vitro has been frequently used to generate several attenuated DNA and RNA viruses [19] [20] [21] [22] . In this study, we sought to create a cold-adapted attenuated G2b PEDV low-passage strain by progressively decreasing growth temperatures to 32°C in Vero cells and then attempted to evaluate its protective efficacy on neonatal piglets against virulent PEDV challenge.