A genotype 2b NS5B polymerase with novel substitutions supports replication of a chimeric HCV 1b:2b replicon containing a genotype 1b NS3-5A background

HCV diversity suggests that evaluation of HCV inhibitors for broad genotypic efficacy is warrented. The replicon system enables cell-culture compound efficacy evaluation against an active replication complex, and a functional replicon dependent upon a genotype 2b polymerase would augment existing cell-culture efficacy studies that are presently limited to genotype 1a, 1b, and 2a replicons. We made a chimeric Neo 1b:2b replicon where genotype 2b NS5B was inserted into a genotype 1b NS3-5A background and transfected replicon RNA to generate Neo cell lines. All cell lines contained novel substitutions within NS5B which were subsequently engineered into the parental 1b:2b replicon and shown to enhance replication to various degrees. A single NS5B M31I substitution enhanced replication to levels sufficiently robust to quantify sensitivity to HCV inhibitors in a transient replication assay. The M31I 1b:2b replicon was similarly sensitive to an active-site nucleoside inhibitor of NS5B as genotype 1b replicons, but was insensitive to two non-nucleoside inhibitors which were otherwise efficacious against the genotype 1b replicons. This work describes a novel HCV replicon sustained by a genotype 2b polymerase that is sufficiently robust for quantifiable analysis in a transient replication assay, and demonstrates its utility in characterizing anti-HCV compounds for cross-genotypic efficacy. (c) 2005 Elsevier B.V. All rights reserved.