A second group of hepatitis C viruses.

cDNA clone 11-7 was isolated by immunoscreening a cDNA library that was prepared from a pooled plasma of non-A non-B hepatitis (NANBH) patients using expression vector lambda gt11. This cDNA corresponds to known nucleotide positions 3983-4745 of the genome of hepatitis C virus (HCV). This clone was used as a probe for screening the HCV-related cDNAs in a cDNA library similarly prepared by using lambda gt10. As a result, six more cDNA clones were isolated and analyzed for their nucleotide sequences. The results strongly suggested that there are at least two groups of HCV, group I and group II. According to our classification, the prototype HCV and clone 11-7 belong to group I HCV, and their nucleotide and deduced amino acid sequences were diverged from those of group II HCV. Genetic variation observed in the nucleotide and the amino acid sequences between the two groups resembles that in the NS3 region of the genome between Japanese encephalitis virus and West Nile fever virus. Polypeptides produced in Escherichia coli carrying a clone 11-7 or a group II cDNA clone E reacted with antibodies in the blood of 12 or 4 out of 14 individual chronic NANBH patients, respectively. Our data clearly indicate the existence of a second group of HCV.