Association of IL28B Genetic Variations with Spontaneous Clearance of Hepatitis C Virus, Treatment Response

Abstract

Among the health problems faced globally Hepatitis C virus (HCV) signify an important entity. The virus is found around the globe with varying occurrence in different countries. HCV has been found as chief factor causing chronic infection in liver leading to fibrosis, cirrhosis which can lead to hepatocellular carcinoma. Various studies have revealed that environmental, viral and host factors contribute to the differences in the disease expression and treatment response. In order to initiate a thorough understanding of the various factors which could affect our set of population the present study was completed in two stages. In the first phase the focus was on analysis of viral factors; the prevalent genotypes in the region with associated viral loads. The investigation revealed the occurrence of genotypes 1 and 3 with additional subtypes 1a, 1b, 3a, 3b and mixed genotypes 1b + 3a, 1b + 3b and 3a + 3b. Quantification of Viral load was done in 151 patients who were found to be HCV positive. Genotype 3a was detected in 124 (82.12%) HCV positive patients, genotype 3b was recognized in 21 (13.91%), however other HCV genotypes were fewer than 2 %. Viral load was associated among various genotypes. Nevertheless, the rigorousness of disease was greater in genotype 1 as shown by comparatively higher viral load associated with this genotype. The Second phase of the study was designed to determine the association of IL28B genetic polymorphisms as host factors playing a role in treatment response in patients having HCV genotype 3a infection. These genotypes are widely associated in different genome wide association studies (GWAS) with spontaneous as well as treatment induced HCV clearance. DNA obtained from 169 HCV patients taking Interferon and Ribavarin base antiviral therapy was analyzed for the polymorphisms of IL28B gene by means of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Bidirectional sequencing was performed on a subset of the studied patients for confirmation of results obtained from PCR-RFLP technique. Information comprising on factors like age, alanine aminotransferase (ALT) levels and Hemoglobin (Hb) was tested. It was noted that ALT association was not significantly associated with Rapid virological response (RVR) but in one set of our study patients (group II) ALT levels showed significant association with Sustained virological response (SVR) (p=0. 010) and in these patients mean ALT levels of patients was 40 U/L. Two IL28B genotypes were analyzed for their linked with RVR and SVR. In one group of study (group I) the occurrence of CC/CT/TT genotypes in rs 12979860 genotypes in patients who achieved SVR were found to be 79.7 %, 15.6 % and 4.7 %, respectively. For rs8099917 genotype, the TT/GT/GG distribution was 81.3 %, 10.9 % and 7.8 %, respectively. CC genotype at rs12979860 and TT genotype at rs8099917 were significantly higher in responders (p = 0.046 and 0.000, respectively). In second group of study the frequency distribution of TT/GT/GG genotype at rs8099917 were 57.3 %, 20.7 % and 1.2 % respectively (p = 0.01). Lower baseline ALT and rapid viral response were also found to be associated with SVR. In this study we have found that among patients infected with HCV genotype 3a there is significant association of successful treatment response in genotype CC in rs12979860 locus (p=0.04) and TT genotype at rs8099917 locus (p=0.00). Favorable C allele at IL28B rs12979860 locus was found in higher ratio (85.6%) than T allele (14.4%). Higher ratio of C allele in SVR achievers and T allele in SVR non-achievers was noted. At rs8099917 T allele was higher in both sets of patients (81.1% & 81.7%) whereas G allele frequency was low. Allele association with RVR and SVR point towards the part of genetic factors in clearance of infection. caused by HCV RVR was noted as a significant predictor of Sustained Virological response in both groups of our study (p =0.029, p =0.000), Considering the analysis in view of early viral kinetics RVR was achieved in 75.6 % of the patients. Further analysis of rs12979860 polymorphism showed (66.5 %) was CC allele carriers while (19.5%) were CT allele carriers. Among, TT allele carriers RVR achievers were (3.4%). In analysis of rs8099917 those with TT allele RVR achievers were (63.2 %) those having TG allele RVR achievers were (20.7 %) and those having GG allele RVR achievers were (4.6 %). Similarly rs8099917 genotype TT was significantly associated with RVR in the group II of the study. The observations highlight the importance of working towards personalized approach for patients where the funds are limited and the chance of success is the duty of specialists to bear in mind right patient for right therapeutic regimen. It is recommended that a broad based strategy regarding parameters such as age, ALT levels, IL28B genotypes rs12979860 polymorphisms (CC, CT &TT) and rs8099917 polymorphisms (TT, GT & TT) and single allele (C, T & G) should be devised. High risks for HCV infection include, intravenous drug users, patients receiving multiple transfusions (Thalassemia and Leukemia patients), patients undergoing Hemodialysis and patients with HBV & HIV co-infections. The studies should be conducted to get a thorough insight into factors playing role in spontaneous and treatment induced clearance of HCV. The results of the detailed analysis might be used to guide treatment for chronic hepatitis C in Pakistani patients in the future.