We found that significantly more EGFP-positive cells were observed in HLECs than in RPECs and ASFCs as determined by fluorescence microscopy at 72 h after infection by lenti-LEP503-HSV-tk-EGFP (Figure 2A), whereas more EGFP-positive cells were observed in HLECs, RPECs, and ASFCs after infection by lenti-CMV-HSV-tk-EGFP (Figure 2B). Here, TKT is linked to infection.