Culturing MARC-145 Cells and Propagating PRRSV Strains

MARC-145 cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM, 10566-016, Gibco, NY, USA) supplemented with 10% fetal bovine serum (FBS, 10099141C, Gibco), 100 units/mL penicillin, and 100 μg/mL streptomycin sulfate (B540732, Sangon Biotech, Shanghai, China). PAMs were obtained and cultured as previously described (27 (link)). The recombinant PRRSV-GFP strain (50 (link)) was kindly donated by Professor En-Min Zhou from Northwest A&F University (Yangling, Shaanxi, China). The highly pathogenic PRRSV strain HN07-1 (HP-PRRSV, GenBank accession no. KX766378.1) (51 (link)) was kindly donated by Professor Gai-Ping Zhang from Henan Agricultural University (Zhengzhou, China). The less pathogenic PRRSV strain BJ-4 (LP-PRRSV no. AF331831.1) was used as described previously (27 (link)). Viruses were propagated and titrated in MARC-145 cells by calculating the median tissue culture infective dose as previously described (27 (link)).