Kazuhiro Tanahashi

A Sensitive Serodiagnosis of Hepatitis C Virus (HCV) Infection with Two Non‐Fused Peptides: Comparison of Antibody Responses Detected with a Newly Developed Assay and a Commercial Second‐Generation Test

An enzyme‐linked immunosorbent assay (ELISA) was developed for the detection of anti‐HCV antibody. We assayed for antibodies against either oligopeptide (S29‐1) deduced from the nucleocapsid gene or the product of nonstructural region (NS3) synthesized in a recombinant Escherichia coli (S4). To reduce false‐positive results induced by non‐specific binding of antibodies with a carrier protein and to increase the sensitivity of an immunoassay, non‐fused S4 peptide was prepared by the recombinant DNA technique and site‐specific proteolysis (by factor Xa). In 71 non‐A, non‐B hepatitis patients with chronic liver disease, 70 (98.5%) were positive by S29‐1/S4 ELISA as well as by a second‐generation test (Abbott II). On the other hand, of 40 serum samples from blood donors, in which anti‐N14 (core) and C100‐3 antibodies were not detected but hepatitis C virus (HCV) RNA was detectable by polymerase chain reaction (PCR), 24 (60%) were positive by S29‐1/S4 ELISA, whereas only 18 (45%) were diagnosed by Abbott II. In addition, based on results in a small group of 92 blood donors, detection of anti‐S29‐1/S4 antibody correlated well with HCV viremia as confirmed by PCR. These results indicated that the preparation of non‐fused protein (S4) by recombinant DNA technique and a combination of S29‐1 and S4 as immobilized antigens in an ELISA provide a sensitive and specific diagnosis for HCV infection with good correlation with the presence of viral RNA as confirmed by PCR.