2.1 Cells and sample collection
Swine testicle (ST) cells were purchased from the China Institute of Veterinary Drug Control, Beijing, China, and passaged in Dulbecco’s modified Eagle’s medium (DMEM) (Gibco, Carlsbad, CA, USA) supplemented with 10% heat-inactivated fetal bovine serum (FBS) (Gibco).
A total of 1,174 tissue samples (including lungs, brains, kidneys, lymph nodes and spleens) were collected from Bartha-K61-immunized swine farms in the East (including in Kaifeng, Shangqiu and Zhoukou cities), West (including in Luoyang, Sanmenxia cities), South (including in Nanyang, Zhumadian, Xinyang cities), North (including in Anyang, Xinxiang, Jiaozuo, Puyang and Hebi cites) and Middle (including in Zhengzhou, Pingdingshan, Xuchang and Luohe cities) of Henan province, China, during 2012-2019 (Fig.1).