Aim: The aim of the present study is to study the mechanism of entry of hepatitis C virus (HCV) into human cells. We examined the in vitro binding of HCV to various human cell lines with or without CD81 expression.
Methods: We first used three cell lines, two hepatocyte-derived, huH-7 and HepG2, and one colon cancer cell line, Cw2. Among them, HepG2 did not express TAPA-1 (CD81) on their surface but two others did. They were incubated with HCV + serum for 1 h and HCV-RNA in extracted RNA obtained from these cells was examined by using both a quantitative test and reverse transcriptase-polymerase chain reaction (RT-PCR).
Results: We found that a significant amount of HCV-RNA was detected in huH-7 and HepG2 but not in Cw2. In addition, the titer of HCV-RNA in serum-incubated CD81-transfected HepG2 was similar to that of the non-transfected titer, and the binding between HCV and huH-7 was not inhibited by anti-CD81. Under the same condition, HCV-RNA tended to be detectable in serum-pulsed hepatocyte-derived cell lines, but not in the others.
Conclusion: These results suggest that while CD81, as reported, specifically binds to HCV-E2 protein, the entry of HCV into human hepatocytes might be regulated by CD81-unrelated molecule(s).
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