Efficient initiation of HCV RNA replication in cell culture

Hepatitis C virus (HCV) infection is a global health problem affecting an e stimated 170 million individuals worldwide. We report the identification of multiple independent adaptive mutations that cluster in the HCV nonstructu ral protein NS5A and confer increased replicative ability in vitro. Among t hese adaptive mutations were a single amino acid substitution that allowed HCV RNA replication in 10% of transfected hepatoma cells and a deletion of 47 amino acids encompassing the interferon (IFN) sensitivity determining re gion (ISDR). Independent of the ISDR, IFN-alpha rapidly inhibited HCV RNA r eplication in vitro. This work establishes a robust, cell-based system for genetic and functional analyses of HCV replication.