-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

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.