subject: The Distribution Of Genotype And Allelic Frequency Of Il28b Gene Polymorphism In Andhra Pradesh, Ind [print this page] Chronic hepatitis C virus (CHC) infection is a major cause for developing cirrhosis and hepatocellular carcinoma (HCC) which often results in liver failure and require transplantation. According to World Health
Organization (WHO), 180 million people are infected worldwide and annually 34 million new infections were estimated.1 The current standard therapy for CHC consists of polyethylene glycol pegylated-interferon-a and
ribavirin (PEG-IFN-a/ribavirin [RBV]).2 Interferon-a acts through a single receptor and signals through the wellcharacterized janus kinase-signal transducer and activator of transcription protein (JAK-STAT) pathway to
up- or down-regulate hundreds of genes that function in immune response pathways.3 Attainment of sustained virological response (SVR) in patients with hepatitis C virus (HCV) infection depends on virus-specific
characteristics, disease and host genetic factors.4 The human genome is composed of 3.3 billion base pairs and about 10 million of these may vary in nucleotide sequence between individuals (single nucleotiden
polymorphism or SNP). Some of these variations may result in altered expression of the gene or altered processing of the gene product (post-translational modification) or altered functional activity (e.g., receptor
binding). Identifying polymorphisms that result in altered clinical expression (phenotype) is a challenge to unravel the disease process as well as the therapeutic response.5
However, in the past 2 years, genome-wide association studies (GWAS) have confirmed that polymorphisms near the IL28B gene on chromosome 19, which encodes the type-III IFN, predict SVR upon treatment with
PEG-IFN-a/ RBV in HCV-monoinfected patients bearing genotype-1.69 Specifically, SNP rs12979860C/T, located 3 kilobases upstream of the IL28B gene, is strongly associated with more than 2-fold difference in the
rate of SVR.6 IL28B encodes IFN-k3, a cytokine, distantly related to type I IFNs and the interleukin (IL)-10 family. Together with IL28A (IFN-k2) and IL29 (IFN-k1), IL28B forms a cytokine gene cluster on a chromosomal
region mapped to 19q13. Expression of the cytokines encoded by these three genes can be induced by ribonucleic acid (RNA) virus infection.10
Background
The single nucleotide polymorphism (SNP) of IL28B gene on chromosome 19, encoding for the interferon (IFN)-?-3 is strongly associated with treatment response to pegylated-IFN and ribavirin in patients infected with
different genotypes of hepatitis C virus (HCV). Difference between ethnicity and treatment response rates suggesting a key role of host genetics. The IL28B polymorphism (rs12979860C/T) shows a marked differential
distribution between racial groups.
Aim
The present study is aimed to evaluate genotype and allelic frequency of IL28B gene polymorphism (rs12979860C/T) in Andhra Pradesh, India.
Methods
A total of 220 healthy controls were recruited for the study. The genotyping of SNP rs12979860C/T on IL28B gene was performed by polymerase chain reaction-direct sequencing method.
Result
The frequency of CC genotype was found to be significantly (59.09%) higher compared to CT (34.09%) and TT (6.81%) genotypes, respectively. The frequency of major allele C is 0.762 whereas minor allele T is 0.238.
Conclusion
The higher distribution of genotype CC of SNP, rs12979860C/T of IL28B gene in study subjects is suggestive of better response of HCV patients to standard anti-HCV therapy.
