A Novel Small Molecule Inhibitor of Hepatitis C Virus Entry

Abstract

Small molecule inhibitors of hepatitis C virus (HCV) are being developed to complement or replace treatments with pegylated interferons and ribavirin, which have poor response rates and significant side effects. Resistance to these inhibitors emerges rapidly in the clinic, suggesting that successful therapy will involve combination therapy with multiple inhibitors of different targets. The entry process of HCV into hepatocytes represents another series of potential targets for therapeutic intervention, involving viral structural proteins that have not been extensively explored due to experimental limitations. To discover HCV entry inhibitors, we utilized HCV pseudoparticles (HCVpp) incorporating E1-E2 envelope proteins from a genotype 1b clinical isolate. Screening of a small molecule library identified a potent HCV-specific triazine inhibitor, EI-1. A series of HCVpp with E1-E2 sequences from various HCV isolates was used to show activity against all genotype 1a and 1b HCVpp tested, with median EC50 values of 0.134 and 0.027 µM, respectively. Time-of-addition experiments demonstrated a block in HCVpp entry, downstream of initial attachment to the cell surface, and prior to or concomitant with bafilomycin inhibition of endosomal acidification. EI-1 was equally active against cell-culture adapted HCV (HCVcc), blocking both cell-free entry and cell-to-cell transmission of virus. HCVcc with high-level resistance to EI-1 was selected by sequential passage in the presence of inhibitor, and resistance was shown to be conferred by changes to residue 719 in the carboxy-terminal transmembrane anchor region of E2, implicating this envelope protein in EI-1 susceptibility. Combinations of EI-1 with interferon, or inhibitors of NS3 or NS5A, resulted in additive to synergistic activity. These results suggest that inhibitors of HCV entry could be added to replication inhibitors and interferons already in development.

Sustained Virological Response Rates to Antiviral Therapy in Genotype 1 and 3 Chronic Hepatitis C Patients: A Study from North India

“…As of now PEG-IFN and ribavirin is still the therapy of choice for HCV patients in our population besides having many side affects. 9 We evaluated the efficacy of PEG-IFN and RBV in northern Indian population suffering from chronic hepatitis C genotype 1 and 3 infection and documented the SVR rates, taking into consideration various predictive factors.…”

Impact of Intra- and Interspecies Variation of Occludin on Its Function as Coreceptor for Authentic Hepatitis C Virus Particles

“…To measure HCV infection by direct cell-to-cell transmission between adjacent cells, we performed a modified version of the agarose overlay assay recently described by Baldick and colleagues (3) in which transmission from HCV-positive donor cells to HCV-negative target cells in coculture was assessed. Donor Huh-7.5 cells were infected with supernatant containing an excess of HCVcc (H77/JFH1 chimera [18]).…”

Cell Culture Systems for Hepatitis C Virus

“…Combination of this system with an agarose overlay facilitates this assay setup (Ciesek, von Hahn et al 2011;Ciesek, Westhaus et al 2011). Instead of using two distinct cell populations, quantification of the number of infected cells per infection focus under an agarose overlay similarly allows to study cell-to-cell spread (Baldick, Wichroski et al 2010;Calland, Albecka et al 2012) …”