Specifically, 3D4 cell lines designated 3D4CD163, 3D4CD163−6E8-mutant, and 3D4CD163−9A10-mutant were generated via infection with recombinant lentiviruses encoding porcine full-length CD163, CD163–6E8-mutant and CD163–9A10-mutant, respectively. Here, CD163 is linked to infection.