CD163 and infection: After infection with PRRSV-HuN4, we found that the PAM-Tang-low line, which contained 55.18% CD163-positive cells, showed limited PRRSV replication; however, PRRSV replicated efficiently in both the PAM-Tang-middle (68.4% CD163-positive cells) and PAM-Tang-high lines (82.88% CD163-positive cells) (Figure 4D).