Transcripts of a chimeric cDNA clone of hepatitis C virus genotype 1b are infectious in vivo.

We constructed a chimeric cDNA clone of hepatitis C virus (HCV) that is infectious. The chimeric genome encodes the polyprotein of a genotype 1b strain (HC-J4) of HCV and replicates via 5' and 3' untranslated regions of a genotype 1a strain. The infectivity of three full-length cDNA clones was tested by direct injection of RNA transcripts into the liver of a chimpanzee. The chimpanzee became infected with HCV and the viral titer increased over time from 10(2) genome equivalents (GE)/ml at week 1 postinoculation (p.i.) to 10(4)-10(5) GE/ml during weeks 3-11 p.i. Antibodies to HCV were detected from week 18 p.i. However, the chimpanzee did not develop hepatitis. Sequence analysis of PCR products amplified from the serum of the chimpanzee demonstrated that only one of the three clones was infectious. Sequence comparisons with the cloning source, an acute-phase infectious plasma pool derived from an experimentally infected chimpanzee, showed that this infectious clone had three amino acids that differed from the consensus sequence of HC-J4, whereas the two noninfectious clones had seven and nine amino acid differences, respectively. Together, genotype 1b, represented by the infectious molecular clone described herein, and genotype 1a, represented by the two cDNA clones previously shown to be infectious for chimpanzees, account for the majority of HCV infections in the United States, Europe, and Japan.