A hepatitis C virus (HCV) E2 variant encompassing amino acids 458 to 680 was expressed in
Escherichia coli
. The recombinant product (His-E2
680) was immunoidentified as a 30-kD protein using the serum from a patient with chronic hepatitis C, and was purified using Ni
2+-NTA chelate chromatography. When HCV-positive human sera were tested with the His-E2
680 protein, 39% of them showed anti-E2 reactivity. ELISA experiments showed that this antigen was very immunogenic in immunized rabbits. Using synthetic peptides, we identified an immunologically relevant region in the 643-671 segment of the His-E2
680 protein.