CLDN1 and hepatocellular carcinoma: To determine if the differences in HCVpp and HCVcc infection between each hepatoma cell line could be attributed to entry factors already shown to modulate HCV permissiveness in other hepatoma cell lines [25, 32, 48–51], we examined the expression of four essential HCV entry factors (i.e. CD81, SR-BI, CLDN1 and OCLN) by RTqPCR, flow cytometric and immunofluorescence analysis (Figure 2).