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We analyzed serum HCV-RNA levels using a newly developed quantitative nucleic acid hybridization (branched DNA probe) assay in 32 Japanese patients with chronic hepatitis C treated with β-interferon (β-IFN). The branched DNA probe assay was less sensitive than the polymerase chain reaction (PCR) method but it provided easy and accurate quantitative analysis of HCV-RNA levels in several samples. Eleven of 32 (34%) patients had a complete response (CR) to IFN treatment, defined as normalization of ALT levels. Six patients (19%) had a partial response (PR) and 15 (47%) had no response (NR). In only one of 11 (9%) patients with CR, the pre-treatment HCV-RNA level was marginally more than the detectable limit of 350 kequivalents/ml (keq/ml). However, serum HCV-RNA levels were detectable in four of six patients (67%) with PR and 13 of 15 (87%) patients with NR. There was a significant difference in HCV-RNA levels between CR and NR groups (9% vs. 87%, P ) using this method. We could not find a significant difference in the proportion of different genotypes of HCV-RNA between CR and NR groups. We conclude that determination of serum HCV-RNA levels prior to IFN treatment using a branched DNA probe assay is very useful in predicting the effect of IFN treatment.

Effects of interferon (IFN) treatment on 91 patients with chronic HCV-related liver diseases in three hospitals were analyzed. HCV-RNA encoding the NS5 region of HCV was detected by the RT-PCR method, and HCV genotyping was performed by slot-blot hybridization using the type-specific cDNA probes on HCV-NS5. HCV titers in blood before treatment with IFN were determined by the multicyclic PCR method. HCV-NS5 was positive in 61 out of 91 patients and the HCV-K1 genotype was found in 40 patients, whereas the HCV-K2 genotype was found in 21. To summarize results from all three hospitals, 52.3% of patients recovered completely and 33.3% recovered partially in the K2 group, in each of these the percentage was significantly higher than in the K1 group. In addition, the percentage of the patients showing no response to IFN treatment was significantly higher in the K1 group than in the K2 group. In the HCV-NS5-negative group, the percentage of patients who did not respond was significantly lower than in the K1 group. In the K1 group, a complete recovery tended to be found more frequently in patients with lower titers of HCV. However, some patients with low titers of HCV did not respond to treatment. The differences of HCV titers between the groups showing different responses to IFN treatment was not statistically significant. In the K2 group, HCV titers were significantly lower than those in the K1 group; however, the effects of IFN were not related to the titers of HCV in K2 group. Two patients with liver cirrhosis in the K2 group had a complete or partial recovery, whereas four patients with liver cirrhosis in the K1 group did not respond to IFN treatment. These results indicate that the HCV genotype is the most important determinant of the effects of IFN treatment.

A cDNA clone, C8-2, derived from nonstructural (NS) protein 5 region of hepatitis C virus (HCV) genome hasbeen isolated and was expressed in Escherichia coli as a fusion protein with β -galactosidase ( β -Gal). The recombinant protein, β -Gal/C8-2, was partially purified and used for detection of anti-HCV antibody by enzyme-linked immunosorbent assay (ELISA). Anti-C8-2 antibody was detected in 47% of patients with post-transfusion non-A, non-B (NANB) acute hepatitis and in 55% of patients with NANB chronic liver diseases. Of 1491 normal blood donors, ten (0.7%) were positive for anti-C8-2 antibody, and three of these ten samples were negative for anti-C100-3 antibody. HCV RNA was detected in one of these three samples. These results suggest that the recombinant protein containing C8-2 peptide may be useful as another nonstructural protein epitope for diagnosis of hepatitis C and screening of blood donors.