Molecular cloning of the immunodominant regions of hepatitis C virus type III and IV by immunoscreening.

: We have identified the immunodominant regions of hepatitis C virus (HCV) type III and IV by immunoscreening of a lambda gt11 cDNA library, which was constructed with RNA extracted from pooled sera of patients. In addition to the nucleocapsid protein, nonstructural region 3 (NS3), and NS4 regions, we found that the region at the N terminus of NS5 in type III and IV were also immunoreactive as well as in the prototype and type II, although amino acid homologies were approximately 60% between the prototype (or HCV type II) and HCV isolates of type III or IV. This result indicated that the region at the N terminus of NS5 may be a candidate for serotyping studies of HCV. This report presents the primary structure of immunodominant portions at the N terminus of NS5 in two HCV subtypes and a preliminary study of the immune responses to these antigens.