Mutations in the hepatitis C virus polymerase that increase RNA binding can confer resistance to cyclosporine A.

Unlabelled: Hepatitis C virus (HCV) infection leads to acute and chronic liver diseases, and new classes of anti-HCV therapeutics are needed. Cyclosporine A (CsA) inhibits HCV replication and CsA derivatives that lack the immunosuppressive function are currently in clinical trials as candidate anti-HCV drugs. Here we characterize several independently derived HCV replicons with varying levels of CsA resistance due to mutations in nonstructural protein 5B (NS5B), the HCV-encoded polymerase.

Selection and characterization of drug-resistant HCV replicons in vitro with a flow cytometry-based assay.

Because HCV RNA-dependent RNA polymerase is error-prone and the viral RNA has a high turnover rate, the genetic diversity of HCV is very high both in vitro and in vivo. The mutation rate in long-term replicon cultures approaches 3.0 x 10(-3) base substitutions/site/year in this in vitro replication model.

Cyclophilin A is an essential cofactor for hepatitis C virus infection and the principal mediator of cyclosporine resistance in vitro.

Cyclosporine (CsA) and its derivatives potently suppress hepatitis C virus (HCV) replication. Recently, CsA-resistant HCV replicons have been identified in vitro. We examined the dependence of the wild-type and CsA-resistant replicons on various cyclophilins for replication.

Characterization of hepatitis C virus subgenomic replicon resistance to cyclosporine in vitro.

Treatment of hepatitis C virus (HCV) infection has been met with less than satisfactory results due primarily to its resistance to and significant side effects from alpha interferon (IFN-alpha). New classes of safe and broadly acting treatments are urgently needed. Cyclosporine (CsA), an immunosuppressive and anti-inflammatory drug for organ transplant patients, has recently been shown to be highly effective in suppressing HCV replication through a mechanism that is distinct from the IFN pathway.

Effect of cell growth on hepatitis C virus (HCV) replication and a mechanism of cell confluence-based inhibition of HCV RNA and protein expression.

An intimate relationship between hepatitis C virus (HCV) replication and the physiological state of the host liver cells has been reported. In particular, a highly reproducible and reversible inhibitory effect of high cell density on HCV replication was observed: high levels of HCV RNA and protein can be detected in actively growing cells but decline sharply when the replicon cells reach confluence. Arrested cell growth of confluent cells has been proposed to be responsible for the inhibitory effect.