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).