Mutations in the NS5A gene predict response to interferon therapy in Japanese patients with chronic hepatitis C and cirrhosis

Hepatitis C virus and the controversial role of the interferon sensitivity determining region in the response to interferon treatment

The degree of variability of the interferon sensitivity determining region (ISDR) in the hepatitis C virus (HCV) genome has been postulated to predict the response to interferon therapy, mainly in patients infected with subtype 1b, although this prediction has been the subject of a long controversy. This prediction has been tested by analyzing a cohort of 67 Spanish patients infected with HCV genotype 1, 23 of which were infected with subtype 1a and 44 with subtype 1b. A sample previous to therapy with alpha-interferon plus ribavirin was obtained and several clones (between 25 and 96) including the ISDR were sequenced from each patient. A significant correlation between mutations at the ISDR and response to treatment for subtype 1b patients, but not for those infected with subtype 1a, has been detected. Although the results suggest that the same relationship holds true for subtype 1a, lack of statistical power because of the small sample size of this subtype prevented firmer conclusions. However, identical ISDR sequences were found in responder and non-responder patients, suggesting that the stability of the ISDR sequence can occasionally help HCV to evade interferon therapy, although this is not a sufficient condition. More complex interactions, including the ISDR or not, are likely to exist and govern the HCV response to interferon treatment.

Prediction of efficient virological response to pegylated interferon/ribavirin combination therapy by NS5A sequences of hepatitis C virus and anti-NS5A antibodies in pre-treatment sera

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).

Mutations in the interferon sensitivity-determining region (nonstructural 5A amino acid 2209-2248) in patients with hepatitis C-1b infection and correlating response to combined therapy of pegylated interferon and ribavirin

BACKGROUND

Most reports suggest that mutations in the interferon sensitivity-determining region (ISDR) correlate with response to conventional interferon-based therapies in hepatitis C virus-1b (HCV-1b) patients. However, the correlation between ISDR region mutations and response to pegylated interferon plus ribavirin therapy in HCV-1b patients remains unclear.

AIM

To assess whether ISDR mutations correlate with response to Peg interferon plus ribavirin therapy in HCV-1b patients.

PATIENTS AND METHODS

Sixty HCV-1b naive patients who had undergone 6 months of Peg interferon alpha-2b plus ribavirin and a 6-month follow-up were enrolled. The amino acid sequences of the nonstructural 5A-interferon-induced RNA-dependent protein kinase (NS5A-PKR)-binding domain were determined by polymerase chain reaction and sequencing.

RESULTS

Thirty (50%) patients achieved sustained virological response (SVR). Univariate analysis showed that the proportion of patients with ISDR mutations >or=4 and rapid virological response rate was higher in the sustained virological response group than in the non-SVR group. Viral load was lower in the SVR group than in the non-SVR group. Multivariate analysis revealed that ISDR mutations >or=4 and ribavirin >or=14 mg/kg/day were independent predictors of SVR.

CONCLUSION

Mutations of the ISDR correlate with SVR to Peg interferon alpha-2b plus ribavirin therapy in HCV-1b patients.

Meta-Analysis of Mutations in the Ns5A Gene and Hepatitis C Virus Resistance to Interferon Therapy: Uniting Discordant Conclusions

Background

Hepatitis C virus genotype 1B responds poorly to treatment with interferon, in contrast to the more interferon-sensitive genotypes 2 and 3. Studies on combination therapy regimens with PEG-interferon and ribavirin report sustained response rates that generally do not exceed 50%, in contrast to sustained response rates of 80% for genotype 2 and 3. In Japan, a correlation was found between the number of mutations in an ‘interferon sensitivity determining region’ (ISDR) and outcome of interferon treatment in genotype 1B-infected patients. However, an ongoing controversy on the existence of an ISDR in non-Japanese isolates resulted, as non-Japanese studies failed to confirm this association. The present study approached this issue by carrying out a meta-analysis of ISDR sequences and response to interferon treatment.

Methods

Twenty-seven studies were included, reporting 1351 ISDR sequence data of genotype 1B-infected patients and their virological response to interferon treatment. Both summary statistics and individual patient data were used systematically to explore the association between ISDR mutations and response to interferon.

Results

The ISDR effect on response was universally present but appeared to be stronger in Japan, with a relative risk of 5.73 for mutant viruses as compared to 4.66 for non-Japanese isolates. High interferon dose, in Japan administered more frequently, was associated with an increase in response rate only among patients infected with mutant isolates. Interaction between dose and ISDR type was confirmed in a logistic regression model. After stratifying for dose, differences in response rate between Japanese and non-Japanese patients were no longer present.

Conclusion

This study puts an end to a longstanding controversy by confirming the universal existence of an ISDR in genotype 1B-infected patients. Apparent discrepant findings from Japanese and non-Japanese studies can be explained by differences in dosing regimens and a dose-dependent differential effect of ISDR mutations on response to treatment.

Mutations in nonstructural 5A gene of hepatitis C virus and its response to interferon alfa

AIM

To investigate the relationship between NS5A_2209-2248 sequences and response to interferon therapy, and whether there is an IFN sensitivity determining region(ISDR) in the region of NS5A_2209-2248.

METHODS

We analyzed 11 patients with chronic HCV 1b infection who had received interferon alfa therapy for six months. Pretreatment serum samples were analyzed. The amino acid sequence of NS5A_2209-2248 was determined by direct sequencing of the HCV genome amplified by the polymerase chain reaction.

RESULTS

Among the 11 patients, only 1 was intermediate type, all the others were wild type. 2 of wild type patients showed complete response. Others were nonresponders. There was no significant difference in nucleotide and amino acid sequences between the two groups.The nucleotide and amino acid sequences changed after IFN treatment in one nonresponder.

CONCLUSION

The NS5A_2209-2248 region was highly conservative. In Chinease patients with chronic HCV 1b infection, there was no correlation between response to interferon and mutations in the NS5A gene. HCV quasispecies changed after IFN therapy.

Mutations in the NS5A and E2-PePHD region of hepatitis C virus type 1b and correlation with the response to combination therapy with interferon and ribavirin

Nonstructural 5A (NS5A) and the second envelope (E2) proteins of hepatitis C virus (HCV) have the potential to block interferon (IFN)-induced RNA-dependent protein kinase (PKR) and may therefore interfere with the response to IFN therapy, but controversy still exists regarding the relevance of this. This study aimed to assess whether mutations in these regions correlated with the response to combination therapy, IFN and ribavirin. Pretreatment parameters were analysed in 57 HCV-1b patients who had received IFN-alpha2b (3 or 5 MU three times weekly) and ribavirin (800-1200 mg per day) for 24 weeks. The amino acid sequences of the NS5A and PKR-eIF2alpha phosphorylation homology domain (E2-PePHD) were deduced from the corresponding coding sequence, which were determinated by direct sequencing of the HCV genome amplified by the polymerase chain reaction. Twenty (36%) patients achieved a sustained virological response (SVR). The mean number of amino acid substitutions in the NS5A-PKR binding domain (2209-2274), interferon sensitivity-determining region (ISDR) (2209-2248), and E2-PePHD sequence (659-670) in patients with and without SVR were 4.53 +/- 3.31 vs 2.83 +/- 1.78 (P = 0.094), 2.45 +/- 2.74 vs 1.03 +/- 1.32 (P = 0.042) and 0.25 +/- 0.70 vs 0.03 +/- 0.17 (P = 0.109), respectively. Patients with a mutant-type (>/= 4) NS5A-ISDR had a higher rate of SVR (six of nine, 67%) than those with wild-type (five of 22, 23%) (P = 0.038). Stepwise multiple logistic regression analysis of the factors (age, gender, viral load, cirrhosis rate, IFN dosage and amino acid substitutions) revealed that the mutation in NS5A-ISDR (>/= 4 vs < 4) was the only independent variable of treatment outcome. Our study showed that NS5A-ISDR mutations were correlated with the SVR to combination therapy in chronic HCV-1b patients in Taiwan.

Management of chronic hepatitis C and prevention of hepatocellular carcinoma

Hepatitis C virus (HCV) infection is responsible for more than a half of the cases of chronic viral hepatitis in Japan. About 20% of patients who are chronically infected with the virus develop cirrhosis about 20-30 years after the infection, with hepatocellular carcinoma developing in about 5% of patients a year. The only drug that effectively reduces the virus is interferon, but complete eradication of the virus can be obtained in only 30%-40% of treated patients. Reevaluation of the predictive factors to eradicate the virus by 24-week interferon therapy showed that the genotype other than 1b, a low virus load, and multiple amino acid substitutions in the interferon sensitivity determining region (ISDR) of genotype 1b are statistically significant predictive factors. Amino acid substitution in the PePHD domain of the E2 protein was rare and was unrelated with the outcome of interferon therapy. The fluctuation of the virus titer measured by branched DNA during a 2-year observation period was less that 10-fold in most patients, and amino acid substitutions in the ISDR were rare in such patients, suggesting that one point measurement of these parameters may be useful to select candidates for interferon therapy. A comparison of patients treated with interferon and untreated patients from the viewpoint of cancer prevention showed only a slight decrease in the risk of treated patients developing hepatocellular carcinoma. However, patients who showed normal alanine amino-transaminase (ALT) irrespective of virus clearance showed a significantly reduced risk of liver carcinogenesis. Similarly, a retrospective study to evaluate the long-term preventive effect of glycyrrhizin on hepatocellular carcinoma development showed that the therapy was effective in lowering the ALT value and in preventing liver carcinogenesis.

Southeast Asian patients with chronic hepatitis C: the impact of novel genotypes and race on treatment outcome

Hepatitis C virus (HCV) genotype and other host and viral factors influence treatment outcome in chronic HCV infection. We evaluated the effect of race and genotype on interferon and ribavirin treatment outcome in 70 Southeast Asian (SEA) and 50 white patients. Genotype was based on the 5' untranslated region (5'UTR) with a commonly used line probe assay (INNO-LiPA HCV II) that may mistype genotype 7, 8, or 9 as 1b. HCV core region sequencing resulted in reclassification of 8 genotype 1 and 25 genotype 1b SEA subjects as genotype 7, 8, or 9. Twenty-six SEA genotype 7, 8, and 9 (79%) and 10 SEA true genotype 1b (59%) patients achieved a sustained virologic response (SVR) compared with 15 (34%) white genotype 1b patients. Logistic regression analysis showed that SEA patients with genotype 7, 8, or 9 were more likely to achieve a SVR than white genotype 1b patients (OR 16.56; 95%CI 4.16, 65.91) as were SEA true genotype 1b patients compared with white genotype 1b patients (OR 4.63; 95%CI 1.19, 18.04). In conclusion, a proportion of SEA patients classified by INNO-LiPA as genotype 1b were in reality genotype 7, 8, or 9. In comparison with white genotype 1b patients, both SEA genotype 1b and SEA genotype 7, 8, and 9 patients showed a significantly greater SVR. HCV core sequencing was necessary to determine genotype accurately in persons potentially exposed to HCV genotypes 7, 8, or 9. This study also supports the concept that race and ethnicity are important determinants of treatment outcome in HCV infected patients.

Management strategies using pharmacogenomics in patients with severe HCV-1b infection: a decision analysis

The management of interferon (IFN) therapy for histologically severe chronic hepatitis C virus genotype 1b (HCV-1b [F3]) is controversial. A decision analysis using the Markov decision analysis model was performed for 6 disease management strategies by using clinical data from a Japanese teaching hospital and available published data. The results of base case analyses showed that IFN monotherapy was considered favorable for patients aged 40 to 60 years with HCV-1b (F3). For the sensitivity analyses, to support the results of base case analyses, HCV-1b (F3) patient quality-of-life (QOL) score must be 0.5 or greater for those 40 to 50 years old and 0.4 to 0.5 or greater for those 60 years old. When patients with HCV-1b (F3) were judged as nonresponsive (NR) after IFN monotherapy, the transition probabilities of liver diseases at 40, 50, and 60 years of age had to be such that the progression of liver diseases was controlled at an annual rate of 7.51% to 8.82% or lower, 7.77% to 8.27% or lower, and 6.39% to 6.60% or lower, respectively, and the sustained virologic response (SVR) rate for IFN monotherapy must be 3.0% to 5.51% or greater, 5.57% to 5.93% or greater, and 10.6% to 11.21% or greater, respectively. It is likely that IFN monotherapy could be applied to patients with HCV-1b (F3) aged 40 years at a dose of at least 432 MU. However, IFN monotherapy did not appear useful for patients with HCV-1b (F3) aged 50 and 60 years if they had no amino acid mutation in NS5A 2209 to 2248 and HCV RNA levels exceeded 1.0 mEq/mL. In conclusion, use of decision analysis models can help in therapeutic decisions for patients with HCV-1b.

Hepatitis C viral load does not predict disease outcome: going beyond numbers

The analysis of 58 patients with chronic hepatitis C without cirrhosis and treated with interferon-alpha demonstrated that hepatitis C viral (HCV) load does not correlate with the histological evolution of the disease (p = 0.6559 for architectural alterations and p = 0.6271 for the histological activity index). Therefore, the use of viral RNA quantification as an evolutive predictor or determinant of the severity of hepatitis C is incorrect and of relative value. A review of the literature provided fundamental and interdependent HCV (genotype, heterogeneity and mutants, specific proteins), host (sex, age, weight, etc) and treatment variables (dosage, time of treatment, type of interferon) within the broader context of viral kinetics, interferon-mediated immunological response (in addition to natural immunity against HCV) and the role of interferon as a modulator of fibrogenesis. Therefore, viral load implies much more than numbers and the correct interpretation of these data should consider a broader context depending on multiple factors that are more complex than the simple value obtained upon quantification.

Association of amino acid sequence in the PKR-eIF2 phosphorylation homology domain and response to interferon therapy

Hepatitis C virus (HCV) genotype 1b and high pretreatment virus load are well known predictive factors of poor response to interferon (IFN) therapy. In addition, a sparsity of amino acid substitutions in the interferon sensitivity determining region (ISDR) is also predictive of a poor response to IFN in patients with genotype 1b, although this issue is still controversial. Recently, a 12 amino acid domain in the E2 protein of HCV (PKR-eIF2 alpha phosphorylation homology domain [PePHD]) has been reported to bind with and block the virus replication inhibition ability of PKR, suggesting that the interaction of E2 and PKR may be one mechanism by which HCV circumvents the antiviral effect of IFN. To clarify the significance of amino-acid sequences in this domain in predicting the effect of IFN therapy, we analyzed 82 patients with genotype 1b. Eleven patients (13.4%) responded to treatment whereas the remaining 71 patients (86.6%) were nonresponders. Multivariate analysis showed that only HCV load and amino-acid substitutions in the ISDR were predictive of sustained response to IFN. Amino-acid substitutions in the PePHD were detected in only eight of 82 patients (9.8%), and did not correlate with the therapeutic effect of IFN. However, amino-acid-sequence analyses of quasispecies before and after 1 week of IFN therapy showed elimination of clones with substitutions in this domain. Our results suggest that amino-acid sequences of the PePHD domain may be related to viral resistance to IFN but do not predict the outcome of IFN therapy as amino-acid substitutions in this domain are rare.

Effect of interferon treatment on serum 2',5'-oligoadenylate synthetase levels in hepatitis C-infected patients

Interferon (IFN) is widely used for patients with hepatitis C. Less than half of treated patients respond to IFN therapy, however, and increased resistance to IFN is particularly observed in genotype 1b patients. Recently, genotype 1b patients with the wild type sequence in the NS5A gene were shown to be resistant to therapy, suggesting that the NS5A protein may be involved to IFN resistance. Thus, we investigated the serum 2',5'-oligoadenylate synthetase (2',5'-OAS) levels before and during IFN treatment. In addition, other biochemical markers and NS5A mutations were also examined in 30 HCV genotype 1b-positive patients. Before IFN treatment, 2',5'-OAS activity in sera was significantly lower in wild type patients than in mutant type patients. All patients were subsequently enrolled in IFN therapy, and 2',5'-OAS activity was elevated both in wild and mutant type patients, irrespective of the number of mutations in NS5A. Logistic regression analysis revealed that clearance of serum HCV RNA was independently related to the pretreatment viral load and NS5A mutations, but not to serum 2',5'-OAS activity. We concluded that the NS5A protein, that is associated with the outcome of IFN therapy, affects the kinetics of IFN-induced molecules, such as 2', 5'-OAS. 2',5'-OAS activity does not, however, seem to be related to long-term virological response to IFN therapy.