-137G>C Polymorphism in the Promoter Region of Il18gene is Associated with Serum Interleukin 18 (Il-18) Levels in Patients with Hepatitis C Virus Infection

Research Article

J Hepat Res. 2014;1(3): 1016.

-137G>C Polymorphism in the Promoter Region of Il18gene is Associated with Serum Interleukin 18 (Il-18) Levels in Patients with Hepatitis C Virus Infection

Faria PL1, Patente TA4,5, Nastri ACSS1,3, Carrilho FJ1, Pinho JRR1,2* and Malta FM1

1Department of Gastroenterology, University of São Paulo School of Medicine, Brazil

2Hospital Israelita Albert Einstein, Brazil

3Department of Infectious and Parasitic Diseases, University of São Paulo School of Medicine, Brazil

4Department of Immunology, University of São Paulo, Brazil

5Celular and Molecular Laboratory, University of São Paulo School of Medicine, Brazil

*Corresponding author: Pinho JRR, Department of Gastroenterology, University of São Paulo School of Medicine, Hospital Israelita Albert Einstein, Brazil, Avenida Dr. Enéas de Carvalho Aguiar No. 255, Prédio II, 05403-000 São Paulo, SP, Brazil

Received: September 02, 2014; Accepted: November 10, 2014; Published: November 12, 2014


Hepatitis C Virus (HCV) is usually associated with chronic infection and the factors leading to viral clearance or persistence are poorly understood. Interleukin 18 (IL-18) is a pro-inflammatory cytokine with broad biological effects. Several polymorphisms in the IL18 gene and plasma IL-18 levels have been reported to influence the outcome of hepatitis C. In this study, IL18 gene promoter polymorphisms (-607C>A and -137G>C) and levels of serum IL-18 were analyzed in 51 HCV spontaneous clearance and 50 chronically infected patients. Single Nucleotide Polymorphisms (SNPs) were genotyped by qPCR with specific primers and a specific ELISA was used for the quantitative determination of IL-18 cytokine. The results showed that there was no evidence for association between the polymorphisms and the outcome of HCV infection. Nevertheless, plasma IL-18 levels were found to be higher in chronic HCV infected patients than in HCV clearance ones. GG genotype at position -137 was associated with higher IL-18 levels in the studied population even when adjusted for HCV infection status. In conclusion, our data suggest that -137 G>C in IL-18 gene is associated with a functional dysregulation of the IL-18 production in a Brazilian cohort of patients with HCV infection.

Keywords: IL-18; HCV; Single polymorphism and Viral clearance


Hepatitis C Virus (HCV) infection is usually subclinical and typically asymptomatic in the acute phase. However, the virus replicates in the liver continuously and progressively and it is estimated that more than 130 million people were infected worldwide [1,2]. A hallmark of HCV infection is its high propensity to establish persistence in 60–80% of infected individuals. This patients are unable to eliminate the virus and most of them evolve to a chronic infection accompanied by liver inflammation, followed by liver fibrosis, cirrhosis and an increased risk to develop Hepatocellular Carcinoma (HCC) [3-5]. Nevertheless, some patients are able to spontaneously clear the virus. Estimates of clearance rates ranged from 20-40% [6,7] and the reasons why these differences exist in the progression of the disease are not fully understood, although the influence of host and viral factors must be considered.

The immune factors and other biomarkers associated with HCV pathogenesis are not well defined and very little is known about the early events in virus–host interactions that determine HCV clearance versus progression to chronic HCV infection. Cytokines play a key role in the regulation of immune responses. During Hepatitis C virus infection, the production of cytokine appears to contribute to viral persistence and to affect response to therapy [8-11].

One factor that can modulate the host immune response is Interleukin-18 (IL-18), also known as IFN γ–inducing factor, an important regulator of innate and adaptive immune responses that has multiple roles in chronic inflammation and autoimmune disorders [12-15]. IL-18, a member of IL-1 cytokine family, IL-18 is an 18 kDa glycoprotein synthesized as a 23 kDa inactive precursor (pro-IL-18) that needs to be cleared by caspase-1 in order to become an active [14,15,18, 21-24]. It is a pleiotropic cytokine expressed at relatively high levels in different cell types, such as macrophages, osteoblasts, monocytes, macrophages, keratinocytes, intestinal epithelial cells, astrocytes, dendritic cells and microglia [12,16-20].

The IL-18 plays a fundamental role in host defense against pathogens and can regulate both innate immunity and adaptive responses. In chronic HCV infection, the implication of IL-18 has been repeatedly proven in several studies, first as a marker of inflammation and hepatic injury and, second, as a predictor of antiviral treatment response [17,18,21,23-28]. IL-18 activity is determined in part by the action of an intrinsic inhibitor, an IL-18 Binding Protein (IL18BP), which has the ability to bind to a receptor site, preventing the action of IL-18 [15,17,22, 29-31].

The IL18 gene is located on chromosome 11q22.2-q22.3 and a variety of single polymorphisms (SNPs) have been detected within IL18 gene sequence. Giedraitis et al, [2001] described two SNPs at positions -607C>A(rs1946518) and -137G>C (rs197238). Both of them disrupt transcription factors binding sites leading to a decreasing level of IL-18 mRNA. The capacity for IL-18 cytokine production in individuals has a major genetic component. This has been related to polymorphisms within the regulatory regions of cytokine genes. Polymorphisms in IL18gene have been implicated in HCV infection outcome [32-35].

This study was undertaken to investigate the association of two SNPs in the IL18 gene (-607C>A [rs1946518] and -137 G>C [rs187238]) and the relationship between the clearance and the persistence of HCV infection in Brazilian patients. Associations with IL-18 cytokine levels were also assessed.

Materials and Methods


A total of 101 subjects was recruited in this study, including 51 patients with anti-HCV positive and negative for HCV-RNA on at least two occasions, a minimum a six months apart, also confirmed by Recombinant Immuno Blot Assay (spontaneous clearance) and 50 with chronic hepatitis C (anti-HCV and HCV-RNA positive, with the latter being repeatedly positive over at least a 6-month period of testing) [Table 1].