Response to Retreatment With Interferon- Plus Ribavirin in Chronic Hepatitis C Patients Is Independent of the NS5A Gene Nucleotide Sequence Nieves Ibarrola, Ph.D., Jose ´ A. Moreno-Monteagudo, M.D., Margarita Sa ´iz, Ph.D., Carmelo Garcı ´a-Monzo ´n, M.D., Francisco Sobrino, Ph.D., Luisa Garcı ´a-Buey, M.D., Oreste Lo Iacono, M.D., Ricardo Moreno-Otero, M.D., and Encarnacio ´n Martı ´nez-Salas, Ph.D. Centro de Biologı ´a Molecular Severo Ochoa, CSIC-UAM, Madrid, Liver Unit, Hospital de la Princesa, Universidad Auto ´noma, Madrid, and Centro de Investigacio ´n en Sanidad Animal, INIA, Madrid, Spain OBJECTIVE: Interferon- plus ribavirin is an effective treat- ment for chronic hepatitis C patients. We evaluated whether the response to this combined therapy correlated with the presence of mutations in a region of 372 nucleotides within the NS5A gene. METHODS: Sixty-two patients, 42 nonresponders and 20 re- lapsers to a previous course of interferon-, received 3 million units thrice weekly of interferon--2b and 1–1.2 g daily of ribavirin for 12 months. Basal biochemical and virological (HCV RNA and genotype) parameters were de- termined. Clinical examinations were carried out at 1, 2, 3, 6, and 12 months. In addition, nucleotide sequencing of the NS5A gene was determined for viral samples obtained from 38 of these patients at the baseline of the combined therapy, as well as in 15 of them before initiating the previous course of interferon as monotherapy. RESULTS: On finishing the 12 months, 36 patients (58.1%) had normal aminotransferases and 25 (40.3%) cleared vire- mia. Nucleotide sequencing indicated the same level of genetic variability within the group of responder and non- responder patients all along the 124 amino acid residues of the NS5A gene studied. Neither the type of amino acid substitution nor the number of them was significantly dif- ferent in one group relative to the other. CONCLUSIONS: Therapy with interferon--2b plus ribavirin was well tolerated, achieving an end-of-treatment response in 25 (40.3%) patients. Response did not correlate with the presence of mutations in the NS5A gene analyzed, including the interferon sensitivity determining region (ISDR) and its flanking sequences. (Am J Gastroenterol 1999;94: 2487–2495. © 1999 by Am. Coll. of Gastroenterology) INTRODUCTION Chronic infection by the hepatitis C virus (HCV) is respon- sible for a progressive liver disease that constitutes an im- portant health care problem throughout the world (1, 2). Using interferon- (IFN-), at a recommended dose of 3 million units subcutaneously thrice weekly for 12–18 months, a biochemical response during treatment is obtained in up to 70% of patients, although after ceasing therapy relapse is frequent (3–5). Thus, only 20 –25% of the patients treated with IFN- achieve sustained virological response (6, 7). Predictors of response to IFN- are controversial, considering that genotypes other than 1, a low viremia level, and absence of liver fibrosis on histology are associated with the best chance of a sustained response (8). Additionally, in patients infected with genotype 1b, a substantial correlation between responses to IFN- and mutations in the NS5A gene has been reported (9). However, this correlation has been shown to fail in other groups of samples (10, 11). Due to the limitations of IFN efficacy, a more effective treatment in chronic hepatitis C (CHC) patients is currently being evaluated. Ribavirin, a nucleoside analogue active against a range of DNA and RNA viruses, used in combi- nation therapy with IFN-, significantly increases the pro- portion of patients with complete biochemical and virolog- ical responses (12, 13). This combined therapy may have the advantage of superimposing the immunomodulatory and antiviral activity of IFN- (14) on that of ribavirin, provided that their combination is not exceedingly toxic to the pa- tients (13). The target for ribavirin antiviral effects remains largely unknown; regardless of its potential modulatory effect on the patient’s immunological system, its capacity to eliminate viral RNA from tissue culture cells persistently infected with the picornavirus foot-and-mouth disease virus (FMDV) has been proven (15). Because in this in vitro system immune surveillance is absent and production of IFN is not detectable (16), it is likely that some pathway within the infection cycle is sensitive to the action of this nucleoside analogue. In spite of the differences between HCV and FMDV infection cycles, their genome organiza- tion presents several similarities (17). Therefore, a common target for ribavirin may exist during the infection cycles of HCV and FMDV. Several reports have associated the IFN- response with the composition of the NS5A gene (9, 18). Thus, the aim of THE AMERICAN JOURNAL OF GASTROENTEROLOGY Vol. 94, No. 9, 1999 © 1999 by Am. Coll. of Gastroenterology ISSN 0002-9270/99/$20.00 Published by Elsevier Science Inc. PII S0002-9270(99)00437-2