Expression of the HCV receptor genes and proteins under hypoxic conditions. (A) Analysis of protein production in Huh7.5 cells cultured under hypoxic and normoxic conditions. A cell lysate was prepared after culturing for 48 h under each condition. H, hypoxic conditions; N, normoxic conditions. (B) Total RNA was extracted from Huh7.5 cells cultured under normoxic or hypoxic condition for 48 h. Expression of mRNAs previously reported to function as HCV receptor genes was analyzed by qRT-PCR (average ± SD; n = 4). (C) Effect of CLDN1, OCLN, and EGFR on Luc-HCVccJFH1 infection of CD81-defective Huh7.5 cells. Huh7.5#26 cells that lack CD81 expression were transfected with CLDN-, OCLD-, and EGFR-expressing plasmids with or without VLDLR-expressing plasmids. After transfection, cells were infected with Luc-HCVccJFH1. At 48 h postinfection, luciferase activity was quantified (average ± SD; n = 3). Expression levels of each HCV entry factor were analyzed by immunoblotting. ***P < 0.005, ns, not significant (Student’s t-test).