Mutations in the NS5A region do not predict interferon-responsiveness in American patients infected with genotype 1b hepatitis C virus

A striking association has been demonstrated recently between mutations in amino acid residues 2209-2248 of the nonstructural protein 5a (NS5a) region of hepatitis C virus (HCV) and sustained responses to interferon in Japane se patients infected with genotype 1b. Therefore, analysis of this sequence has been suggested as a predictor of treatment response. We sought to dete rmine whether mutations in this region predict outcome in U.S. patients inf ected with genotype Ib hepatitis C virus (HCV-1b). We analyzed stored pretr eatment sera retrospectively from 22 patients with HCV-1b infection who had received interferon alpha-2b (IFN alpha-2b) as part of a controlled trial. Two patients were sustained responders (SR), 7 were transient responders ( TR), and 13 were nonresponders (NR). We performed nested reverse transcript ion-polymerase chain reaction (RT-PCR) on extracted RNA using primers flank ing HCV amino acids 2209-2248 and sequenced the PCR products directly. The deduced amino acid sequences were compared with the prototype HCV-J. Isolat es with four or more deviations from the prototype were defined as "mutant" type, those with one to three substitutions as "intermediate" type, and th ose matching the prototype as "wildtype." Of the 22 HCV-1b isolates, 6 were wildtype, 11 intermediate type, and 5 mutant type. Both of the SRs were in termediate type. The 20 TRs and NRs were distributed among mutant (5), inte rmediate (9), and wildtype (6). Of the five patients with mutant virus, fou r were NR and one a TR. Variation in NS5a(2209-2248) fails to predict inter feron responsiveness in this cohort of American patients infected with HCV- 1b. Thus, the utility of this sequence as a predictor of interferon respons iveness appears to be specific to Japanese patients and may reflect differe nces between patient groups in treatment regimens, host genetic background, or alterations in the interferon signaling pathway induced by surrounding sequences within or outside NS5a. Overall, NS5a is not as integral a determ inant of interferon responsiveness as previously suggested. J.Med. Virol. 5 8:353-358, 1999. (C) 1999 Wiley-Liss, Inc.