CLDN1 and infection: Incomparison to HCVcc infection of Huh-7.5 cells, for which viral infectioustiters (above 1×106 i.u./ml) could be assessed byimmunostaining for Core protein, the same viral stocks resulted in lowerinfectivity levels in SK-Hep1-CLDN1-SR-BI target cells (data not shown),precluding accurate determination of infectious titers by immuno-detection.Therefore, we used a sensitive and quantitative real-time RT-PCR (RT-qPCR) assayto measure changes in HCV RNA at 4 hr, 12 hr and 72 hr post-infection withHCVcc.