The defect of TLR3 signaling in Marc-145 cells may be one reason that this cell type is permissive for PRRSV replication, which is reminiscent of another cell type, human hepatoma Huh7.5, with defects in RIG-I and other receptor signaling proteins that make it highly permissive to HCV infection [35]. The gene discussed is TLR3; the disease is hepatocellular carcinoma.