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Telaprevir, a non-structural (NS)3/4A protease inhibitor, is a direct-acting antiviral drug that inhibits viral replication. Triple therapy with telaprevir, pegylated interferon, and ribavirin is a standard therapeutic regimen for patients with genotype 1b chronic hepatitis C virus (HCV) infection and a high viral load. Several factors, including mutations in the NS5A gene, are important predictors of the efficacy of interferon therapy. In this study, we examined the mutational diversity of NS5A and its impact on the efficacy of triple therapy. We enrolled patients with genotype 1b chronic HCV infection and a high viral load (31 males/17 females; mean age, 57.6 years), who were treated with triple therapy. This study was conducted at Kobe University Hospital and at three affiliated hospitals in Hyogo prefecture, Japan, between November 2011 and June 2013. A sustained viral response after 12 weeks (SVR12) was achieved in 37/48 patients (77%). Based on intent-to-treat analysis, SVR12 was significantly greater in patients with the major allele than in those with the minor allele for the IL28B single nucleotide polymorphism (SNP; 88 vs. 56%; P<0.05). The prevalence of the V2334I mutation in NS5A was significantly higher in patients who achieved SVR12, while that of G2356E was significantly higher in patients who did not achieve SVR12 (P<0.05). Mutations in the NS3 region that are thought to confer resistance to telaprevir were detected in 3/27 patients who achieved SVR12 (Val36, n=3) and in 5/10 patients who did not achieve SVR12 (Val36, n=4; Thr54, n=1). In conclusion, the IL28B SNP and mutations in the NS5A region were associated with the therapeutic response to triple therapy. Half of the patients who did not achieve SVR12 had mutations conferring resistance to telaprevir. However, pre-existing mutations in NS3 did not affect the efficacy of triple therapy.

This study demonstrated that Indonesian patients with chronic hepatitis C (mostly ethnic Java people) mostly were infected with hepatitis C virus (HCV) genotype 1; however, they carried mainly the major genotypes of interleukin 28B (IL-28B) single nucleotide polymorphisms (SNPs) (rs12979860 CC, rs11881222 TT, rs8103142 AA, and rs8099917 TT), and they mostly achieved sustained virological responses to pegylated interferon/ribavirin treatment., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

Objectives: This study explores viral factors of the interferon (IFN) and ribavirin (RBV) resistance-determining region (IRRDR), the IFN sensitivity-determining region (ISDR) and the core protein, and host factor interleukin 28B associated with response to pegylated IFN (PEG-IFN) and RBV combination therapy, and the correlation of viral and host factors with IFN-λ1., Methods: A total of 58 patients underwent PEG-IFN/RBV combination therapy for 48 weeks. The pretreatment factors associated with rapid virological response (RVR) and sustained virological response (SVR) were analyzed. Pretreatment IFN-λ1 serum levels were compared with the viral and host factors., Results: Univariate analysis showed that IRRDR ≥6 and ISDR ≥2 were significant pretreatment predictors of RVR, and multivariate analysis identified IRRDR ≥6 and hemoglobin as significant predictors of SVR. Pretreatment IFN-λ1 was significantly higher in the SVR group than in the non-SVR group and also in the IRRDR ≥6 group than in the IRRDR ≤5 group., Conclusions: IRRDR ≥6 was the only significant predictor of SVR and was correlated with IFN-λ1. High serum levels of IFN-λ1 may be conducive to effective PEG-IFN/RBV combination therapy because of the immunomodulatory system., (© 2013 S. Karger AG, Basel.)

Objective: We investigated the impact of host genetics represented by the single nucleotide polymorphism (SNP) of the IL28B gene and viral genetic variations within the nonstructural protein 5A (NS5A) [including the interferon (IFN)/ribavirin (RBV) resistance-determining region (IRRDR) and the IFN sensitivity-determining region (ISDR)] on the outcome of pegylated IFN and RBV (PEG-IFN/RBV) treatment., Methods: Sixty-six patients infected with hepatitis C virus (HCV)-2a or HCV-2b who received PEG-IFN/RBV for 24 weeks were examined., Results: In HCV-2a, the major genotype of IL28B SNP showed a tendency toward association with sustained virological response (SVR) and rapid virological response (RVR), and four or more mutations in IRRDR (IRRDR[2a] ≥4) and one or more mutations in ISDR plus its carboxyl-flanking region (ISDR/+C[2a] ≥1) were significantly associated with SVR and RVR. In HCV-2b, one or more mutations in the N-terminal part of IRRDR (IRRDR/N[2b] ≥1) were significantly associated with RVR. Multivariate analysis identified the major genotype of IL28B SNP and IRRDR[2a] ≥4 as independent predictive factors of SVR in HCV-2a, with IRRDR[2a] ≥4 being more powerful than the IL28B SNP. Also, IRRDR[2a] ≥4 in HCV-2a and IRRDR/N[2b] ≥1 in HCV-2b were significant determiners of RVR., Conclusion: The NS5A sequence heterogeneity and IL28B SNP are useful factors to predict the sensitivity to PEG-IFN/RBV therapy in HCV-2a and HCV-2b infections., (© 2013 S. Karger AG, Basel.)

Objectives: We assessed the outcome of double-filtration plasmapheresis (DFPP) combined with pegylated interferon (PEG-IFN) and ribavirin (RBV) therapy in patients infected with hepatitis C virus (HCV)-1b whose HCV had not disappeared during PEG-IFN/RBV combination therapy, or who had relapsed after the end of the therapy. Additionally, we investigated factors predictive of sustained virological response (SVR), including host and viral genetic factors, to DFPP plus IFN/RBV therapy., Methods: A total of 40 patients infected with HCV-1b whose HCV virus had not been eradicated by previous PEG-IFN/RBV therapy were enrolled for treatment by DFPP plus IFN/RBV. Rapid virological response (RVR) and SVR were assessed, and pretreatment factors associated with SVR - the interleukin (IL)28B gene, the IFN/RBV resistance-determining region (IRRDR) and the IFN sensitivity-determining region (ISDR) - were analyzed., Results: Of the 40 patients, 9 (23%) achieved RVR and 10 (25%) achieved SVR. The significant factors associated with SVR were IL28B major and RVR, as assessed by multivariate analysis (p = 0.0182, p = 0.0005)., Conclusion: Patients whose HCV is not eradicated by previous PEG-IFN/RBV would be good candidates for combined DFPP and IFN/RBV retreatment provided they demonstrate IL28B major and have achieved RVR., (© 2013 S. Karger AG, Basel.)

Hepatitis C virus genotype 4 (HCV-4) is the cause of approximately 20% of the 180 million cases of chronic hepatitis C in the world. HCV-4 infection is common in the Middle East and Africa, with an extraordinarily high prevalence in Egypt. Viral genetic polymorphisms, especially within core and NS5A regions, have been implicated in influencing the response to pegylated-interferon and ribavirin (PEG-IFN/RBV) combination therapy in HCV-1 infection. However, this has not been confirmed in HCV-4 infection. Here, we investigated the impact of heterogeneity of NS5A and core proteins of HCV-4, mostly subtype HCV-4a, on the clinical outcomes of 43 Egyptian patients treated with PEG-IFN/RBV. Sliding window analysis over the carboxy terminus of NS5A protein identified the IFN/RBV resistance-determining region (IRRDR) as the most prominent region associated with sustained virological response (SVR). Indeed, 21 (84%) of 25 patients with SVR, but only 5 (28%) of 18 patients with non-SVR, were infected with HCV having IRRDR with 4 or more mutations (IRRDR ≥ 4) (P = 0.0004). Multivariate analysis identified IRRDR ≥ 4 as an independent SVR predictor. The positive predictive value of IRRDR ≥ 4 for SVR was 81% (21/26; P = 0.002), while its negative predictive value for non-SVR was 76% (13/17; P = 0.02). On the other hand, there was no significant correlation between core protein polymorphisms, either at residue 70 or at residue 91, and treatment outcome. In conclusion, the present results demonstrate for the first time that IRRDR ≥ 4, a viral genetic heterogeneity, would be a useful predictive marker for SVR in HCV-4 infection when treated with PEG-IFN/RBV.

For patients chronically infected with hepatitis C virus (HCV), mutations in the non-structural 5A (NS5A) gene are important predictive factors for the response to interferon (IFN) therapy. In the present study, factor analysis of the therapeutic response of patients following pegylated IFN and ribavirin combination therapy was assessed in a multicenter study. Chronic HCV-infected patients with genotype 1b and high viral load (n=96, mean age 56.5 years; 59 males, 68 females) treated with pegylated IFN-α-2b and ribavirin combination therapy were enrolled. This study was conducted at Kobe University Hospital and 25 affiliated hospitals in Hyogo prefecture. Sixty-five patients (68%) completed treatment with both pegylated IFN and ribavirin at >80% of the weight-based scheduled dosages. Patients who reduced or terminated therapy were frequently aged women (mean age 60.8 years; 11 males, 17 females). Overall, a sustained viral response (SVR) was achieved in 42 (44%) patients out of 96. Based on per-protocol-based (PPB) analysis, the SVR rate in patients with ≥6 amino acid (aa) mutations in the IFN resistance-determining region (IRRDR) (75%) or ≥1 aa mutation in the IFN sensitivity-determining region (ISDR) (61%) was significantly higher than that in patients with <5 aa mutations in IRRDR (30%) or no mutation in ISDR (29%). Multivariate analysis revealed that rapid viral response (RVR) (odds ratio, 18.1) and mutations of ≥6 in IRRDR (odds ratio, 15.5) were significantly associated with SVR. In conclusion, mutations in the NS5A region, particularly in patients with ≥6 aa mutations in IRRDR were strongly associated with a therapeutic response to pegylated IFN and ribavirin combination therapy.

Background: This study explores pretreatment predictive factors for ultimate virological responses to pegylated interferon-α (1.5 μg/kg/week) and ribavirin (600-1000 mg/day) (PEG-IFN/RBV) combination therapy for patients infected with hepatitis C virus (HCV)-1b and a high viral load., Methods: A total of 75 patients underwent PEG-IFN/RBV combination therapy for 48 weeks. HCV amino acid (aa) substitutions in non-structural protein 5a, including those in the IFN/RBV resistance-determining region (IRRDR) and the IFN sensitivity-determining region and the core regions, as well as the genetic variation (rs8099917) near the interleukin 28B (IL28B) gene (genotype TT) were analyzed., Results: Of the 75 patients, 49 % (37/75) achieved a sustained virological response (SVR), 27 % (20/75) showed relapse, and 24 % (18/75) showed null virological response (NVR). Multivariate logistic regression analysis identified IRRDR with 6 or more mutations (IRRDR ≥6) [odds ratio (OR) 11.906, p < 0.0001] and age <60 years (OR 0.228, p = 0.015) as significant determiners of SVR and IL28B minor (OR 14.618, p = 0.0019) and platelets <15 × 10(4)/mm(3) (OR 0.113, p = 0.0096) as significant determiners of NVR. A combination of IRRDR ≥6 and age <60 years improved SVR predictability (93.3 %), and that of IRRDR ≤5 and age ≥60 years improved non-SVR predictability (84.0 %). Similarly, a combination of IL28B minor and platelets <15 × 10(4)/mm(3) improved NVR predictability (85.7 %), and that of IL28B major and platelets ≥15 × 10(4)/mm(3) improved non-NVR (response) (97.1 %) predictability., Conclusion: IRRDR ≥6 and age <60 years were significantly associated with SVR. IL28B minor and platelets <15 × 10(4)/mm(3) were significantly associated with NVR. Certain combinations of these factors improved SVR and NVR predictability and could, therefore, be used to design therapeutic strategies.

Objective: Hepatitis C virus (HCV genome) polymorphisms are thought to influence the outcome of pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy. This study aimed to examine non-structural protein 5A (NS5A) polymorphisms, e.g. IFN/RBV resistance-determining region (IRRDR) and IFN sensitivity-determining region (ISDR), and core protein polymorphism as predictive therapeutic markers., Methods: Pretreatment sequences of NS5A and core regions were analyzed in 68 HCV-1b-infected patients treated with PEG-IFN/RBV., Results: Of 24 patients infected withHCV having an IRRDR with 6 or more mutations (IRRDR≥6), 18 (75%) patients achieved sustained virological response (SVR), whereas only 11 (25%) of 44 patients infected with HCV having IRRDR≤5 did. IRRDR≥6 was significantly associated with SVR (p < 0.0001). On the other hand, ISDR≥2 was significantly associated with relapse (either before [breakthrough] or after end-of-treatment response [ETR[-]relapse]) (p < 0.05) and a point mutation of the core protein from Arg to Gln at position 70 (Gln(70)) was significantly associated with null-response (p < 0.05). Multivariate analysis identified IRRDR≥6 as the only viral genetic factor that independently predicted SVR., Conclusion: NS5A (IRRDR and ISDR) and core protein polymorphisms are associated with the outcome of PEG-IFN/RBV therapy for chronic hepatitis C. In particular, IRRDR≥6 is a useful marker for prediction of SVR., (Copyright © 2011 S. Karger AG, Basel.)

Unlabelled: Pegylated-interferon plus ribavirin (PEG-IFN/RBV) therapy is a current standard treatment for chronic hepatitis C. We previously reported that the viral sequence heterogeneity of part of NS5A, referred to as the IFN/RBV resistance-determining region (IRRDR), and a mutation at position 70 of the core protein of hepatitis C virus genotype 1b (HCV-1b) are significantly correlated with the outcome of PEG-IFN/RBV treatment. Here, we aimed to investigate the impact of viral genetic variations within the NS5A and core regions of other genotypes, HCV-2a and HCV-2b, on PEG-IFN/RBV treatment outcome. Pretreatment sequences of NS5A and core regions were analyzed in 112 patients infected with HCV-2a or HCV-2b, who were treated with PEG-IFN/RBV for 24 weeks and followed up for another 24 weeks. The results demonstrated that HCV-2a isolates with 4 or more mutations in IRRDR (IRRDR[2a]≥4) was significantly associated with rapid virological response at week 4 (RVR) and sustained virological response (SVR). Also, another region of NS5A that corresponds to part of the IFN sensitivity-determining region (ISDR) plus its carboxy-flanking region, which we referred to as ISDR/+C[2a], was significantly associated with SVR in patients infected with HCV-2a. Multivariate analysis revealed that IRRDR[2a]≥4 was the only independent predictive factor for SVR. As for HCV-2b infection, an N-terminal half of IRRDR having two or more mutations (IRRDR[2b]/N≥2) was significantly associated with RVR, but not with SVR. No significant correlation was observed between core protein polymorphism and PEG-IFN/RBV treatment outcome in HCV-2a or HCV-2b infection., Conclusion: The present results suggest that sequence heterogeneity of NS5A of HCV-2a (IRRDR[2a]≥4 and ISDR/+C[2a]), and that of HCV-2b (IRRDR[2b]/N≥2) to a lesser extent, is involved in determining the viral sensitivity to PEG-IFN/RBV therapy.

Both host and viral factors have been implicated in influencing the response to pegylated-interferon/ribavirin (PEG-IFN/RBV) therapy for hepatitis C virus (HCV) infection. Among the viral factors, sequence heterogeneity within NS5A and core regions has been proposed. This study aimed to clarify the relationship between virological responses to PEG-IFN/RBV therapy and sequence heterogeneity within NS5A, including the IFN/RBV resistance-determining region (IRRDR), the interferon sensitivity-determining region (ISDR) and the core region. Pretreatment sequences of NS5A and the core regions were analyzed in 57 HCV-1b-infected patients who were to be treated with PEG-IFN/RBV. Of 40 patients infected with HCV having an IRRDR with four or more mutations (IRRDR ≥ 4), 28 (70%) patients achieved a sustained virological response (SVR). On the other hand, only 4 (24%) of 17 patients infected with HCV having an IRRDR with three or fewer mutations (IRRDR ≤ 3) achieved a SVR (P = 0.001). Similarly, 22 (71%) of 31 patients infected with HCV and having an ISDR with one or more mutations (ISDR ≥ 1) achieved a SVR while 10 (38%) of 26 patients infected with HCV and having an ISDR without any mutations (ISDR = 0) achieved a SVR (P = 0.014). As for the core region, there was significant correlation between a single mutation at position 70 (Gln(70) ) and non-SVR (P = 0.02). Notably, Gln(70) was more prominently associated with the null response (P = 0.0007). In conclusion, sequence heterogeneity within the IRRDR and ISDR, and a single point mutation at position 70 of the core region of HCV-1b are likely to be correlated with virological responses to PEG-IFN/RBV therapy., (© 2011 The Societies and Blackwell Publishing Asia Pty Ltd.)

Background and Aims: Double-filtration plasmapheresis (DFPP) together with interferon (IFN) administration produces a substantial reduction in the viral load during the early stages of treatment., Methods: Based on their responses to previous pegylated IFN and ribavirin (PEG-IFN/RBV) therapy, 20 patients were divided into null virological response (NVR; n = 12) and relapse (n = 8) groups. DFPP was used in combination with IFN-β/RBV with subsequent administration of PEG-IFN-α2a/RBV therapy (DFPP + IFN-β/RBV then PEG-IFN/RBV). Early viral dynamics was assessed, focusing especially on complete early virological response (cEVR) associated with sustained virological response. Additionally, the interleukin 28B gene, the IFN/RBV resistance-determining region, the IFN sensitivity-determining region and the core regions were analyzed., Results: Rapid virological response was achieved in 0% (0/12) of NVR and in 75% (6/8) of relapse patients, with a significant difference between the two groups (p = 0.001). Similarly, cEVR was achieved in 8% (1/12) of NVR and in 88% (7/8) of relapse patients, with a significant difference between the two groups (p = 0.037). By multivariate logistic regression analysis, interleukin-28B major was a significant determiner of cEVR (odds ratio = 24.19, p = 0.037)., Conclusion: DFPP + IFN-β/RBV then PEG-IFN/RBV therapy is indicated more for relapse than for NVR patients., (Copyright © 2011 S. Karger AG, Basel.)

The aim of the study was to identify a predictive marker for the virological response in hepatitis C virus 1b (HCV-1b)-infected patients treated with pegylated interferon plus ribavirin therapy. A total of 139 patients with chronic hepatitis C who received therapy for 48 weeks were enrolled. The secondary structure of the 120 residues of the amino-terminal HCV-1b non-structural region 3 (NS3) deduced from the amino acid sequence was classified into two major groups: A and B. The association between HCV NS3 protein polymorphism and virological response was analyzed in patients infected with group A (n = 28) and B (n = 40) isolates who had good adherence to both pegylated interferon and ribavirin administration (>95% of the scheduled dosage) for 48 weeks. A sustained virological response (SVR) representing successful HCV eradication occurred in 33 (49%) in the 68 patients. Of the 28 patients infected with the group A isolate, 18 (64%) were SVR, whereas of the 40 patients infected with the group B isolate only 15 (38%) were SVR. The proportion of virological responses differed significantly between the two groups (P < 0.05). These results suggest that polymorphism in the secondary structure of the HCV-1b NS3 amino-terminal region influences the virological response to pegylated interferon plus ribavirin therapy, and that virus grouping based on this polymorphism can contribute to prediction of the outcome of this therapy., ((c) 2010 Wiley-Liss, Inc.)

We investigated whether sustained virological response (SVR) and non-SVR by chronic hepatitis C patients to pegylated interferon plus ribavirin (PEG-IFN/RBV) combination therapy are distinguishable by viral factors such as the IFN/RBV resistance-determining region (IRRDR) and by on-treatment factors through new indices such as the rebound index (RI). The first RI (RI-1st; the viral load at week 1 divided by the viral load at 24 h) and the second RI (RI-2nd; the viral load at week 2 divided by the viral load at 24 h) were calculated. The subject patients were divided into 3 groups based on RI-1st and RI-2nd: an RI-A group (RI-1st < or = 1.0), an RI-B group (RI-1st >1.0 and RI-2nd <0.7) and an RI-C group (RI-1st >1.0 and RI-2nd > or = 0.7). The SVR rate was 71.4% (10/14) in the RI-A group, 46.2% (6/13) in the RI-B group and 20.0% (3/15) in the RI-C group (p = 0.005 between the RI-A group and the RI-C group). In IRRDR > or = 6 and IRRDR < or = 5 the SVR rate was 81.3% (13/16) and 23.1% (6/26) (p = 0.0002), respectively. By combining RI and IRRDR as a predicting factor, the SVR rate was 87.5% (7/8) in the RI-A group (> or = 6 mutations in the IRRDR) and 7.7% (1/13) in the RI-C group (< or = 5 IRRDR mutations) (p = 0.0003)., (Copyright 2010 S. Karger AG, Basel.)

Recent clinical trials have shown that pegylated interferon-alpha (PEG-IFN-alpha) in combination with ribavirin (RBV) improves the rate of sustained virological response (SVR), with over 50% of patients demonstrating a positive response to treatment. However, no SVR has been reported when PEG-IFN/RBV combination therapy is discontinued by week 16, especially in cases of chronic hepatitis with a high viral load of serum hepatitis C virus (HCV) RNA, genotype 1b. Here, we describe SVR in a 67-year-old woman whose PEG-IFN/RBV combination therapy for chronic hepatitis C with a high viral load of serum HCV RNA, genotype 1b, was discontinued after 16 weeks because of the onset of PEG-IFN plus RBV-induced acute pancreatitis. Among viral factors, substitution of amino acid 70 (Arg) and 91 (Leu) in the core region and HCV RNA negativity were observed after 8 weeks. Host factors including low body weight, no alcohol consumption, no coinfection with hepatitis B virus, slight fibrosis, and viral factors including early viral clearance, double wild type in the core region, may have contributed to the SVR irrespective of the discontinuation of the combination therapy at week 16. Moreover, PEG-IFN plus RBV-induced acute pancreatitis might have been related to the SVR.

Unlabelled: A substantial proportion of hepatitis C virus (HCV)-1b-infected patients still do not respond to interferon-based therapy. This study aims to explore a predictive marker for the ultimate virological response of HCV-1b-infected patients treated with pegylated interferon/ribavirin (PEG-IFN/RBV) combination therapy. Nonstructural protein 5A (NS5A) sequences of HCV in the pretreated sera of 45 patients infected with HCV-1b were analyzed. The mean number of mutations in the variable region 3 (V3) plus its upstream flanking region of NS5A (amino acid 2334-2379), referred to as IFN/RBV resistance-determining region (IRRDR), was significantly higher for HCV isolates obtained from patients who later achieved sustained virological response (SVR) by PEG-IFN/RBV than for those in patients undergoing non-SVR. The receiver operating characteristic curve analysis estimated six mutations in IRRDR as the optimal threshold for SVR prediction. Indeed, 16 (76%) of 21 SVR, but only 2 (8%) of 24 non-SVR, had HCV with six or more mutations in IRRDR (IRRDR > or = 6) (P < 0.0001). All of 18 patients infected with HCV of IRRDR of 6 or greater examined showed a significant (> or =1 log) reduction or disappearance of serum HCV core antigen titers within 24 hours after initial dose of PEG-IFN/RBV, whereas 10 (37%) of 27 patients with HCV of IRRDR of 5 or less did (P < 0.0001). The positive predictive value of IRRDR of 6 or greater for SVR was 89% (16/18; P = 0.0007), with its negative predictive value for non-SVR being 81% (22/27; P = 0.0008)., Conclusion: A high degree (> or =6) of sequence variation in IRRDR would be a useful marker for predicting SVR, whereas a less diverse (< or =5) IRRDR sequence predicts non-SVR.

We investigated the clinical usefulness of a new immunoradiometric (IRM) assay of hepatitis C virus (HCV) core antigen in predicting virological response during pegylated interferon plus ribavirin (PEG-IFN/RBV) combination therapy for chronic hepatitis with high viral loads of serum HCV RNA genotype 1b. Thirty-nine patients received a regimen of PEG-IFNalpha-2b (1.5 microg/kg/week s.c.) in combination with RBV (600-1,000 mg/day). Of the 39 patients, 18 (46.2%) achieved sustained virological response (SVR), 11 (28.2%) attained partial response (PR) and 10 (25.6%) showed no response (NR). Four weeks after the start of therapy, 1- and 2-log reductions in the amount of HCV core antigen were observed in 20 (2/10) and 0% (0/10) showing NR, 91 (10/11) and 63.6% (7/11) with PRs, and 88.9 (16/18) and 55.6% (10/18) of patients with SVR, respectively. The 1- and 2-log reductions 4 weeks after the start of therapy were not a defining condition for PR and SVR. The amount of HCV core antigen was significantly different between SVR and PR patients on days 1 and 7, and between patients with NR and SVR at all points of time. In conclusion, this new IRM assay is useful in predicting virological response during PEG-IFN/RBV therapy., (Copyright 2008 S. Karger AG, Basel.)

A considerable number of patients infected with Hepatitis C virus subtype 1b (HCV-1b) do not respond to pegylated interferon/ribavirin combination therapy. In this study we explored a useful factor(s) to predict treatment outcome. A total of 47 HCV-1b-infected patients were treated with pegylated interferon/ ribavirin for 48 weeks. Sera of the patients were examined for the entire NS5A sequence of the HCV genome, HCV RNA titers and anti-NS5A antibodies. According to their responses, the patients were divided into two groups, early viral responders who cleared the virus by week 16 (EVR[16w]) and those who did not (Non-EVR[16w]). The mean number of mutations in the V3 region (aa 2356 to 2379) or that in the V3 region plus its N-terminally flanking region, which we refer to as interferon/ribavirin resistancedetermining region (IRRDR; aa 2334 to 2379), of NS5A obtained from the pretreatment sera was signifi-cantly larger for EVR(16w) compared with Non-EVR(16w). Moreover, HCV-1b isolates with > or =5 mutations in V3 or those with > or =6 mutations in IRRDR were almost exclusively found in EVR(16w). Also, the presence of detectable levels of anti-NS5A antibodies in the pretreatment sera was closely associated with EVR(16w). In conclusion, a high degree of sequence variation in V3 (> or =5) or IRRDR (> or =6) and the presence of detectable levels of anti-NS5A antibodies in the pretreatment sera would be useful factors to predict EVR(16w). On the other hand, a less diverse sequence in V3 (< or =4) or IRRDR (< or =5) together with the absence of detectable anti-NS5A antibodies could be a predictive factor for Non-EVR(16w).

Objective: Although all the mechanisms of elimination of hepatitis C virus (HCV) by Interferon (IFN) have not been fully elucidated, the 2'-5'-oligoadenylate (2-5A) system is one of the mechanisms of the antiviral effect of IFN. Consequently, the measurement of 2'-5'-oligoadenylate synthetase (2-5AS) activity could be useful for the evaluation of IFN treatment. This retrospective study was aimed at assessing whether 2-5AS activity functions as a clinical marker of virological response to PEG-interferon-alpha2b (PEG-IFN) plus ribavirin therapy of chronic hepatitis C., Methods: The 32 patients included in this study had high viral loads of serum HCV-RNA of genotype 1b with chronic hepatitis C. All the patients received a regimen of PEG-IFN plus ribavirin for 48 weeks, and were then divided into two groups: one group (effective group) with undetectable serum HCV-RNA levels at 24 weeks (n = 22) of therapy, the other group (ineffective group) with persistent presence of HCV-RNA in serum at 24 weeks (n = 10). The 2-5AS activity in serum was measured 2, 8 and 12 weeks before initial administration., Results: The 2-5AS response ratio (measured value/measured value of baseline 2-5AS) at 2, 8 and 12 weeks after the administration in the effective group was significantly higher than that in the ineffective group., Conclusions: These results suggest that the ratio of 2-5AS is closely related to the antiviral effect, and that the measurement of 2-5AS response ratio may be a useful clinical parameter of virological response to PEG-IFN plus ribavirin therapy of chronic hepatitis C.