High dose of bile acid enables the cellular entry and replication of hepatitis C virus in vitro

Background Natural hosts infected with hepatitis C virus (HCV) have a different bile acid (BA) composition than non-natural hosts uninfected. Our cumulative reports clarified that amid humoral milieu components, BA renders HBV permissive to human or rodent hepatic and non-hepatic cells. However, it is unknown if BA has a permissive effect in HCV against the same target cells. Objective We aimed to establish an in vitro replication platform with BA-directed HCV entry and permissiveness in both human and murine cell lines. Results Low doses of different BAs, such as trihydroxy BA, taurocholic acid (tCA) and dihydroxy BA, taurochenodeoxycholic acid (tCDCA), augmented HCV genome stability and surface antigenicity in vitro. By contrast, high-dosed BA improved the entry of wild type HCV into human and rodent hepatoma or non-hepatic cell lines. In line, we found that the in vitro cell culture condition (100 μmol/L of tCA coupled with 1 × 10 6 IU/mL HCV) was optimal for HCV penetration into target cells. Human (HepG2, Huh7) and rodent (Hepa1c1c7, H4-II-E) hepatoma cell lines were infected with HCV using this method, as evidenced by the presence of HCV RNA in culture supernatant. Further, cellular entry assay revealed that HCV could infect 12 different non-hepatic cell lines regardless of species or organ/tissue, consequently reproducing viral progeny as confirmed by HCV RNA. Lastly, irrespective of tCA, HCV progenies from immortalized HepG2 or Hepa1c1c7 cells successfully infected their mother cells as shown in reinfection assay. Conclusion This study reveals that a high dose of BA, specifically tCA, can directly regulate lipid bilayer status in vitro, allowing HCV entry into immortalized hepatocytes, and non-hepatocytes in humans and mice. This is the first report on HCV permissiveness into human or rodent hepatocytes and non-hepatocytes via non-genetic humoral milieu modulation alone, establishing the platform for a robust HCV replication system in vitro.