Inhibition of hepatitis C virus replication by antimonial compounds

Hypericin inhibits hepatitis C virus replication via deacetylation and down-regulation of heme oxygenase-1

BACKGROUND

Hepatitis C virus (HCV) is a globally prevalent pathogen and a leading cause of death and morbidity. Traditional therapy with pegylated interferon-<alpha> and ribavirin has had only limited success, with some adverse effects. Direct-acting antivirals (DAAs) are effective in suppressing HCV replication, but are expensive.

PURPOSE

Hypericin has been reported to be a good antiviral agent for inhibiting HCV replication, however, little is known about its mechanisms of action. The aim of this study is to elucidate the mode of action of hypericin in Ava5 human hepatoma cell line (Huh7 derivative) harboring HCV subgenomic replicon RNA.

METHODS

To determine the non-structure protein 5A (NS5A) mRNA and NS3 protein expression levels, real-time PCR and Western blot analysis were performed, respectively. To investigate how hypericin inhibits HCV replication, 5-aza-2'-deoxycytidine (5-Aza-dC) and chidamide were used for determining histone modification. Furthermore, shRNA was applied to confirm the role of heme oxygenase (HO-1) in HCV repression.

RESULTS

Hypericin in experiment were tested and showed no cytotoxicity. Hypericin reduced HO-1 and NS5A in a time- and dose- dependent manner. Chidamide, but not 5-Aza-dc, restored hypericin-induced reduction in HCV NS3 expression and reversed HO-1 expression in Ava5 cells. LY294002 inhibited HCV replication via HO-1 down-regulation. Constitutive expressed p-AKT was not involved in hypericin-induced reduction in HCV replication. In addition, shHO-1 inhibited HCV replication.

CONCLUSION

In conclusion, hypericin inhibits HCV replication via down-regulation of HO-1 expression and deacetylation.

Development of NS3/4A protease-based reporter assay suitable for efficiently assessing hepatitis C virus infection

A cell culture system for the production of hepatitis C virus (HCV) whole virions has greatly accelerated studies of the virus life cycle and the discovery of anti-HCV agents. However, the quantification of the HCV titers in a whole-virus infection/replication system currently relies mostly on reverse transcription-PCR or immunofluorescence assay, which would be cumbersome for high-throughput drug screening. To overcome this problem, this study has generated a novel cell line, Huh7.5-EG(Delta4B5A)SEAP, that carries a dual reporter, EG(Delta4B5A)SEAP. The EG(Delta4B5A)SEAP reporter is a viral protease-cleavable fusion protein in which the enhanced green fluorescence protein is linked to secreted alkaline phosphatase (SEAP) in frame via Delta4B5A, a short peptide cleavage substrate for NS3/4A viral protease. This study demonstrates that virus replication/infection in the Huh7.5-EG(Delta4B5A)SEAP cells can be quantitatively indicated by measuring the SEAP activity in cell culture medium. The levels of SEAP released from HCV-infected Huh7.5-EG(Delta4B5A)SEAP cells correlated closely with the amounts of HCV in the inocula. The Huh7.5-EG(Delta4B5A)SEAP cells were also shown to be a suitable host for the discovery of anti-HCV inhibitors by using known compounds that target multiple stages of the HCV life cycle. The Z'-factor of this assay ranged from 0.64 to 0.74 in 96-well plates, indicating that this reporter system is suitable for high-throughput screening of prospective anti-HCV agents.

A liver slice culture-based ex vivo assay to predict the outcome of antiviral therapy for chronic hepatitis C

A liver slice culture-based, ex vivo drug suppression assay was developed as a pre-therapeutic predictor for the outcome of antiviral therapy. To investigate its clinical application, 106 consecutive patients with chronic hepatitis C virus (HCV) infection were evaluated. Ex vivo drug suppression assay was performed before administrating a standard course of peginterferon plus ribavirin combination therapy. Stepwise logistic regression model was used to estimate sustained virological response (SVR) on the presence of various clinicopathological parameters. Suppression of HCV replication in the ex vivo assay was present in 32 patients, 29 (90.6%) of whom achieved SVR. Stepwise logistic regression analysis indicated that the presence of interferon suppression effect in the ex vivo assay (odds ratio [OR], 5.552; 95% confidence interval [CI], 1.114-27.673; P = 0.036), genotype 1 (OR; 0.045, 95% CI, 0.008-0.259; P = 0.001), HCV-RNA level (OR, 0.739; 95% CI, 0.617-0.885; P = 0.001), the presence of fatty metamorphosis (OR, 0.205; 95% CI, 0.053-0.793; P = 0.022), and albumin (OR, 9.687; 95% CI, 2.237-41.940; P = 0.002) were independent determinants of SVR. Categorical analysis revealed that 17 of 17 (100%) patients with genotype non-1 and positive ex vivo suppression test achieved SVR, while 20 of 40 (50%) with genotype 1 and negative ex vivo suppression test achieved SVR. In conclusion, the ex vivo drug suppression assay may serve as an independent pre-therapeutic predictor for the SVR in interferon-based antiviral therapy.

Hepatitis C virus infection in mouse hepatoma cells co-expressing human CD81 and Sip-L

Although human CD81 has been shown to be essential for hepatitis C virus (HCV) infection, non-hepatic cells or transgenic animals expressing human CD81 alone did not support HCV replication. Co-expression of other cofactors was thus necessary for HCV replication. Previously, a hepatic factor named Sip-L was found to support HCV replication in an otherwise non-permissive cell line. To understand the species specificity of hepatic factors required for HCV replication, mouse hepatoma cells co-expressing human CD81 and Sip-L (Hepa1-6-CD81-Sip-L cells) were subjected for HCV infection assay. It was discovered that Hepa1-6-CD81-Sip-L cells were permissive for HCV infection and replication. An animal model was thus established by subcutaneous injection of the permissive cells into nude mice to generate tumors. Viral passages could be achieved in these animals. The antiviral effects of interferon and sodium stibogluconate administrated as a single agent or in combination were demonstrated in this animal model.

Targets of emerging therapies for viral hepatitis B and C

Viral hepatitis B and C, structurally two completely different viruses, commonly infect human hepatocytes and cause similar clinical manifestations. Since their discovery, IFN has been a pillar in the treatment. However, because of the different natures of the viruses, therapeutic approaches diverge and new treatment targets are tailored specifically for each virus. Herein, the authors analyse therapeutic approaches for hepatitis B virus (HBV) and hepatitis C virus (HCV) and focus on emerging concepts that are under clinical evaluation. In particular, promising viral inhibitors for HBV and HCV are reviewed and the current status of research for gene therapy for HCV is described. Immune therapy is a fast-moving field with fascinating results which include therapeutic vaccines and toll-like receptor agonists that could improve tomorrow's treatment approaches.

Status presens of antiviral drugs and strategies: Part II: RNA VIRUSES (EXCEPT RETROVIRUSES)

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of HIV infections. The others have been approved for the therapy of herpesvirus (HSV, VZV, CMV), hepadnavirus (HBV), hepacivirus (HCV) and myxovirus (influenza, RSV) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these are targeting HIV infections. Yet, quite a number of important viral pathogens (i.e. HPV, HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.