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Original Article
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Volume 334:77-82 January 11, 1996 Number 2
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Mutations in the Nonstructural Protein 5a Gene and Response to Interferon in Patients with Chronic Hepatitis C Virus 1b Infection
Nobuyuki Enomoto, M.D., Ikuo Sakuma, M.D., Yasuhiro Asahina, M.D., Masayuki Kurosaki, M.D., Takeshi Murakami, M.D., Chikara Yamamoto, M.D., Yuki Ogura, M.D., Namiki Izumi, M.D., Fumiaki Marumo, M.D., and Chifumi Sato, M.D.

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ABSTRACT

Background A region associated with sensitivity to interferon has been identified in the nonstructural protein 5A (NS5A) of hepatitis C virus (HCV) genotype 1b. The region spans amino acid residues 2209 to 2248 (NS5A2209–2248) of HCV-J, a strain of HCV-1b whose complete genomic sequence has been identified. We examined whether the NS5A2209–2248 sequence present before therapy could be used as a predictor of the response to interferon therapy in patients with chronic HCV-1b infection.

Methods We retrospectively analyzed 84 patients with chronic HCV-1b infection who had received interferon alfa (total dose, 516 million to 880 million units) for six months. Pretreatment serum samples were analyzed. The amino acid sequence of NS5A2209–2248 was determined by direct sequencing of the HCV genome amplified by the polymerase chain reaction (PCR) and was compared with the established sequence for HCV-J.

Results A complete response, as evidenced by the absence of HCV RNA in serum on nested reverse-transcription PCR for six months after therapy, did not occur in any of the 30 patients whose NS5A2209–2248 sequences were identical to that of HCV-J (wild type). Five of 38 patients (13 percent) with 1 to 3 changes in NS5A2209–2248 (intermediate type) had complete responses, as did all 16 patients with 4 to 11 amino acid substitutions (mutant type), indicating that the mutant type was significantly associated with a complete response (P<0.001). Although base-line serum HCV RNA levels, as measured by a branched-chain DNA assay, were lower in patients with the mutant type of NS5A2209–2248 than in those with the other types (P<0.001), multivariate analyses revealed that the number of amino acid substitutions in NS5A2209–2248 was the only variable associated with an independent effect on the outcome of interferon therapy (odds ratio, 5.3; 95 percent confidence interval, 1.6 to 18; P = 0.007).

Conclusions In patients with chronic HCV-1b infection, there is a substantial correlation between responses to interferon and mutations in the NS5A gene.


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From the Second Department of Internal Medicine (N.E., I.S., Y.A., M.K., T.M., C.Y., Y.O., F.M., C.S.) and Division of Health Science (C.S.), Faculty of Medicine, Tokyo Medical and Dental University, and the Department of Internal Medicine, Musashino Red Cross Hospital (N.I.) — both in Tokyo, Japan.

Address reprint requests to Dr. Sato at the Second Department of Internal Medicine, Faculty of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113, Japan.

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