Aims
Expression of the nonstructural protein (NS)3/4A protease in cells infected with hepatitis C virus (HCV)
Background & aims
Expression of the nonstructural protein (NS)3/4A protease in cells infected with hepatitis C virus (HCV)
Conclusions
NS3/4A protease inhibitors can restore IRF-3 signaling in HCV-infected cells but only at concentrations far in excess of the antiviral EC(50).
Methods
Antiviral activities of 2 NS3/4A protease inhibitors (TMC435350 and an analog, TMC380765) and a nonnucleoside polymerase inhibitor (Tib-3) were determined in HCV replicon cells and in cells infected with genotype 1a and 2a viruses. The capacity to rescue IRF-3 activation in these cells was assessed by monitoring IFN-beta promoter activity following challenge with Sendai virus. Inhibitor-induced changes in NS3 and MAVS expression were assessed in immunoblots.
Results
Both protease inhibitors were capable of rescuing IFN-beta promoter activation but only at concentrations approximately 100-fold the antiviral 50% effective concentration (EC(50)) for genotype 1 virus. No rescue was observed with the polymerase inhibitor, even at a concentration 600-fold greater than the EC(50). IRF-3 activation did not correlate with reductions in NS3/4A levels or detection of full-length MAVS. Overexpression of the product of NS3/4A cleavage of MAVS did not result in a dominant-negative effect on signaling. Conclusions: NS3/4A protease inhibitors can restore IRF-3 signaling in HCV-infected cells but only at concentrations far in excess of the antiviral EC(50).