Non-infected (–) and infected (+) Marc-145 whole cell extracts (5 μg) were separated by 15% SDS-PAGE, and the membrane was blotted with PRRS virus M protein antibody [HL2575] (GTX638953) diluted at 1:1000. The HRP-conjugated anti-rabbit IgG antibody (GTX213110-01) was used to detect the primary antibody.