Znaczenie polimorfizmu IL28B w odpowiedzi na leczenie interferonem pegylowanym α i rybawiryną przewlekłego zapalenia wątroby wywołanego genotypem 1b HCV

Introduction

Hepatitis C virus (HCV) infection is a serious global problem, with the number of affected individuals worldwide approximating 170 million people and about 0.7 million individuals in Poland. The virus causes chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The standard antiviral therapy is pegylated interferon  (Peg-IFN) and ribavirin, but treatment response is not satisfactory. Sustained virological response (SVR), defined as undetectable HCV-RNA in blood 6 months after 48 weeks of treatment, is seen in 80% of subjects and is lower (about 50%) in the HCV genotype 1 infection [1]. The effectiveness of treatment depends on the HCV (genotype, viral load) and the genetic host factors [2-4]. In recent years, it has been shown that a single nucleotide polymorphism (SNP) in the region of the interleukin-28B (IL-28B) gene significantly correlates with spontaneous elimination of HCV and SVR [5]. The SNP rs12979860 was described in the IL28B region and the investigators demonstrated that the genetic profile is associated with favourable alleles C/C IL28B [2-7]. However, variants of the T/C or T/T IL28B gene are characterized by a lower percentage of SVR. The pharmacogenetics of chronic hepatitis is associated with a dependence of IL28B genotyping with the elimination of HCV and is important in the individualization of therapy, predicting the effectiveness and costs [3, 8].

The HCV genotype 1b occurs in more than 80% of patients in Poland [9], and the association of the response to treatment with the IL28B genetic determinant in this population has not been previously evaluated.

Aim

The aim of this study was to investigate whether in patients with chronic hepatitis caused by the HCV genotype 1b from the region of southern Poland, the HCV treatment outcomes depend on the rs12979860 variant in IL28B, and also whether this polymorphism can be considered a predictor of response to therapy.

Material and methods

The study included 142 consecutive adult patients of a Slavic ethnic origin, with chronic hepatitis induced by the HCV genotype 1b, who reported for treatment at University Hospital in Krakow and met the following criteria. Inclusion criteria: anti-HCV and HCV-RNA present in the serum and elevated alanine aminotransferase (ALT), evaluated at least 6 months before inclusion, histological examination confirming chronic hepatitis, body mass index (BMI) below 30 kg/m². Exclusion criteria: decompensated cirrhosis, liver cancer, HBV or HIV infection, autoimmune liver disease, alcohol abuse, diabetes, dyslipidaemia, severe chronic diseases, immunosuppressive therapy.

The patients were treated for 48 weeks: Peg-IFN -2a (Roche), 180 µg/kg subcutaneously once per week with ribavirin (Roche) orally, 1-1.2 γ daily or Peg-IFN -2b (Schering-Plough, MSD) 1.5 µg/kg of body weight once a week with ribavirin (Schering-Plough, MSD), 1-1.2 γ daily. After treatment, the patients were followed for 24 weeks.

The study was conducted in accordance with the Helsinki Declaration of 1975, and the patients were informed about the study and provided written consent to participate in the study. Serum anti-HCV, HCV-RNA and ALT were determined. HCV-RNA was measured by reverse transcriptase – polymerase chain reaction (RT-PCR) (Cobas TaqMan HCV Test v. 2.0, Roche Molecular Systems, Inc., USA). HCV-RNA and ALT were determined before treatment and after 12, 48 and 72 weeks. Early virological response (EVR) was defined as undetectable HCV-RNA or at least a 2-log drop in HCV RNA from the baseline at week 12 of treatment; end treatment response (ETR) was defined as undetectable HCV-RNA at the end of the 48-week treatment.

Liver biopsies were performed within the 12 months prior to enrolment. Biopsies containing at least 6 portal spaces were stained with haematoxylin and eosin, the Gomori-Masson method and trichrome for the presence of connective tissue. In staging the fibrotic liver changes, the Batts and Ludwig scale was applied. The characteristics of patients are shown in Table I.

Genomic DNA was isolated from peripheral blood samples using proteinase K – a set of ion-exchange extraction column (A&A Biotechnology, Gdynia, Poland). An amplification product 190 bp in length was obtained using a standard PCR with primers 5'-GCC TCT TCC TCC TGC GGG ACA AG and 5'-GCG CGG GCA AGT ATT CAA CCC T Bsh1236I. After digestion with endonuclease, the resulting products were distributed in the agarose gel electrophoresis. Option C was digested with the enzyme. All the laboratory procedures were carried out on blinded samples.

Statistical analysis

Statistical analysis was performed using the chi-square test and Fisher's exact probability test to compare categorical variables. After analysis of results with the Shapiro-Wilk test, the results were compared by the Wilcoxon-Mann-Whitney U-test, Kruskal-Wallis test or Student’s t-test. The analyses were performed using Statistica v. 9.0 (StatSoft, Inc., USA). The results are presented as mean values and standard deviations (SD), and p < 0.05 in the two-sided test was taken as statistically significant.

Results

The genotyping of IL28B showed the presence of the genotype C/C in 38 patients (26.8%), genotype T/C in 70 patients (49.2%) and genotype T/T in 34 patients (24%). HCV-RNA viral load in serum of patients before treatment and after 12 weeks, during the evaluation of early response to therapy in the groups of genotypes C/C, T/C and T/T, is shown in Table II. The baseline viral load was not significantly lower in patients with the genotype C/C (2.82 ±3.17 × 106 IU/ml) as compared to individuals with T/C and T/T (respectively: 5.08 ±8.27 and 3.85 ±6.36 × 106 IU/ml). HCV-RNA viral load after 12 weeks of treatment in patients with the genotype C/C was significantly (p < 0.01) lower (0.01 ±0.02 × 106 IU/ml) as compared with T/C and much lower than in the genotype T/T (Table II). Additionally, the Spearman's rank correlation performed between HCV-RNA viral load and ALT activity in patients before treatment and after 12 weeks of therapy did not confirm the presence of any significant relationships.

Among all patients treated with Peg-IFN and ribavirin, 38% achieved EVR, 69.7% achieved ETR, and 44.4% achieved SVR. Response to treatment depending on the genotypes C/C, T/C and T/T of IL28B is shown in Table II. The EVR, ETR and SVR in patients with the genotype C/C as compared with the genotypes T/C and T/T were significantly higher. The SVR, which is the criterion of the effectiveness of HCV infection therapy, was achieved in 71.1% of patients with the genotype C/C of IL28B, compared with 41.4% in patients with the genotype T/C, and 23.5% in the genotype T/T (p = 0.006). Tolerance of treatment was similar and independent of the genotypes C/C, T/C and T/T of IL28B.

The ALT activity assessed at the baseline and after 12, 24, 48 and 72 weeks did not differ significantly between the groups with the genotypes C/C, T/T and T/C.

Thus, the independent predictors of SVR in patients with the genotype C/C of IL28B and infected with the difficult to treat HCV genotype 1b were: viral load after 12 weeks of treatment, EVR, and ETR; and in patients with elevated ALT at the baseline, they were enzyme activity after 4 and 12 weeks of therapy.

Discussion

Genetic studies have shown that in patients with chronic hepatitis caused by the HCV gene, polymorphism rs12979860 in IL28B is closely related to the effectiveness of treatment with Peg-IFN and ribavirin [4-6, 10]. Moreover, it has been shown that genetic alterations in IL28B may be predictors of response to this treatment [3, 4, 10-13]. The association of host genetic changes with the treatment outcome in patients with chronic hepatitis have not yet been tested in a population of Polish patients infected with the HCV genotype 1b. We have shown that HCV-RNA in serum of patients at the baseline did not differ significantly among patients with the genotypes C/C, T/C and T/T IL28B. However, after 12 weeks of treatment, HCV-RNA viral load was significantly lower in patients with the genotype C/C versus T/T and did not differ between the genotypes C/C and T/C. These results differ from previous studies of other authors who showed a higher initial viral load of the HCV genotype C/C in an American population [6, 11]. Early treatment response (EVR) reached 63.2% in patients with the genotype C/C, was significantly lower (34.3%) in individuals with the genotype T/C, and was only 17.7% in T/T. These results are poorer than those obtained by other authors [2, 4]. Thompson et al. described EVR in 87% of patients with the genotype C/C IL28B and in 38% and 28%, respectively, of patients with the genotype T/C and T/T [4]. These differences may be due to a different patient population and an initial viral load, which are prognostic factors of response [2]. Several authors have also confirmed a significantly better response to treatment in patients with the genotype C/C compared to the genotypes T/C and T/T [2, 4, 7].

Virological response at the end of treatment (ETR) reached 92.1% in patients with the genotype C/C, 67.1% with T/C, and only 52.9% with the genotype T/T. These results are similar to other studies [4-6]. The SVR is the most important indicator of treatment efficacy of patients with HCV. In this study, SVR was observed in 71.1% of patients with the genotype C/C and was significantly (p = 0.03) lower in subjects with the genotype T/C (41.4%) and with the genotype T/T (23.5%). The multivariate analysis showed that the genotype C/C of IL28B was associated with a significantly higher incidence of ETR and SVR achieved by the patients. The results of these studies are similar to those presented by other authors [4-6].

The mean ALT level exceeded the upper normal limit at the baseline in all the groups and during treatment was similar regardless of the genotype IL28B. Contrary results were obtained by other authors who observed higher ALT in patients with the genotype C/C as compared with T/C and T/T [11]. It should be noted that normal ALT activities are often recorded in patients with chronic hepatitis caused by HCV.

In conclusion, patients with chronic hepatitis caused by the difficult-to-treat HCV genotype 1b treated with Peg-IFN and ribavirin achieved a sustained virological response, which in patients with the genotype C/C IL28B was significantly better in comparison to the genotype T/C (71.1% vs. 41.4%) and the genotype T/T (71.1% vs. 23.5%). The study confirmed, in a patient population from the region of southern Poland, that the response to standard treatment of HCV genotype 1b chronic hepatitis depends on polymorphism of the IL28B gene, which may be a predictor of virus elimination in these patients.

Acknowledgments

All authors declare no conflict of interest.

References

1. Manns MP, McHutchison JG, Gordon SC, et al. Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomized trial. Lancet 2001; 358: 958-65.  

2. Fattovich G, Covolo L, Bibert S, et al. IL28B polymorphisms, IP-10 and viral load predict virological response to therapy in chronic hepatitis C. Aliment Pharmacol Ther 2011; 33: 1162-72.  

3. Ahlenstiel G, Booth DR, George J. IL28B in hepatitis C virus infection: translating pharmacogenomics into clinical practice. J Gastroenterol 2010; 45: 903-10.  

4. Thompson AJ, Muir AJ, Sulkowski MS, et al. Interleukin 28B polymorphism improves viral kinetics and is the strongest pretreatment predictor of sustained virologic response in genotype 1 hepatitis C virus. Gastroenterology 2010; 139: 120-9.  

5. Clark PJ, Thompson AJ, McHutchison JG. IL28B genomic-based treatment paradigms for patients with chronic hepatitis C infection: the future of personalized HCV therapies. Am J Gastroenterol 2011; 106: 38-45.  

6. Ge D, Fellay J, Thompson AJ, et al. Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature 2009; 461: 399-401.  

7. Balagopal A, Thomas DL, Thio CL. IL28B and the control of hepatitis C virus infection. Gastroenterology 2010; 139: 1865-76.  

8. Afdhal NH, McHutchison JG, Zeuzem S, et al. Hepatitis C pharmacogenetics: state of the art in 2010. Hepatology 2011; 53: 336-45.

9. Juszczyk J, Beniowski M, Berak H, et al. Effectiveness of combined treatment with pegylated interferona-2a and ribavirin in chronic hepatitis C – study phase summary. Med Sci Monit 2004; 10 (S1): 5-11.

10. Montes-Cano MA, García-Lozano JR, Abad-Molina C, et al. Interleukin-28B genetic variants and hepatitis virus infection by different viral genotypes. Hepatology 2010; 52: 33-7.

11. Grebely J, Petoumenos K, Hellard M, et al.; ATAHC Study Group. Potential role for interleukin-28B genotype in treatment decision-making in recent hepatitis C virus infection. Hepatology 2010; 52: 1216-24.

12. McCarthy JJ, Li JH, Thompson A, et al. Replicated association between an IL28B gene variant and a sustained response to pegylated interferon and ribavirin. Gastroenterology 2010; 138: 2307-14.

13. Pearlman BL. The IL-28 genotype: how it will affect the care of patients with hepatitis C virus infection. Curr Gastroenterol Rep 2011; 13: 78-86.