Hemoxygenase-1 and its downstream product Biliverdin suppress HCV replication and provides hepatoprotective effects in humanized uPA/SCID mice

Background: Hepatis C Virus (HCV) infection is a leading cause of chronic hepatitis worldwide. Induction of the anti-apoptotic, anti-inflammatory and anti-oxidant enzyme heme oxygenase 1 (HO-1) or application of its heme degradation product biliverdin has been shown to interfere with HCV replication in vitro. Enhancement of host anti-oxidant enzymes, such as HO-1, may attenuate hepatocyte injury during chronic HCV infection. The Aim of this study was to investigate the antiviral and hepatoprotective effects of the HO-1 in vivo using HCV-infected humanized uPA/SCID mice. The antiviral effects of HO-1 induction were also evaluated in combination with interferon alpha treatment. Methods: Patient-derived HCV-positive serum (genotype 1a) was used to establish HCV infection in uPA/SCID mice displaying high levels of human chimerism. Mice received intraperitoneal injections of CoPP (5 mg/kg) or Biliverdin (25 mg/kg) twice per week. Human peg-interferon-alpha (peg-IFNα) (2.5 ng/g; twice/week) was given either alone or in combination with CoPP. Virological changes and intrahepatic expression levels of human genes were measured by qRT-PCR. HCVcore and HO-1 protein levels were visualised by immunohistochemistry. Results: Two weeks of CoPP administration to HCV-infected humanized mice significantly increased human HO-1 RNA levels (14-fold induction), and suppressed HCV replication (median 2log viremia reduction). Furthermore, HO-1 induction attenuated the HCV-driven enhancement of human interferon-stimulated genes (ISGs), such as ISG-15 and Mx1, as well as the expression of human-specific pro-inflammatory cytokines, e.g. TGFβ, thus confirming the protective function of HO-1 in human hepatocytes in vivo. Direct anti-viral effects were determined also after 2 weeks of biliverdin administration (median 1log viremia reduction), although such treatment did not lower the cytokine milieu with similar efficacy. Two weeks of combined treatment with CoPP and peg-IFNα induced an even stronger suppression of HCV viremia (3log reduction) compared to mice receiving the same dosage of peg-IFNα as mono therapy (1log reduction). Conclusions: Induction of the anti-oxidant enzyme HO-1 in human hepatocytes not only provoked significant suppression of viral replication, but also mitigated the pro-inflammatory cytokine milieu in HCV-infected livers. The synergistic anti-viral effects of CoPP and peg-IFNα in combination with protection from HCV-mediated hepatocellular injury suggest a potential role for HO-1 in anti-HCV therapy.