LightCycler-analysis of the Transforming Growth Factor-beta1 Codon 25 Gene Polymorphism in German Patients with Chronic Hepatitis C Infection

In epidemiological studies of chronic HCV infection, duration of the disease, age, alcohol intake, and male gender are independent risk factors related to histological severity of hepatic fibrosis/cirrhosis. However, not all patients exposed to HCV develop the same degree of liver fibrosis. During the last few years, numerous association and genetic susceptibility studies of pro- and anti-inflammatory cytokines have investigated the role of gene polymorphisms in the progression of liver fibrosis in studies evaluating growths factors for their possible role in the progression of liver fibrosis. The polymorphism at codon 25 of the gene encoding the profibrogenic transforming growth factor-beta1 (TGF-beta1), which changes the amino acid sequence of the signal peptide sequence (arginine to proline), is causing a variation in TGF-beta1 production. The homozygous genotype (Arg25Arg) is associated with higher TGF-beta1 production than the heterozygous (Arg25Pro) genotype. We analyzed this polymorphic site in German patients with chronic hepatitis C infection and asked if it is correlated with the stage and grade of hepatic fibrosis. We developed a novel approach for analyzing this polymorphism and determined the allele frequency distributions between patients with different degrees of hepatic fibrosis induced by chronic hepatitis C virus infection. The assay is conducted in a LightCycler (LC) system and specifically distinguishes the different alleles by use of the fluorescence energy transfer (FRET) principle. In patients with severe hepatic fibrosis (METAVIR-score 3–4), the Pro25 allele was twice as frequent compared to patients with mild fibrosis (METAVIR-score 0–2). However, we found no association of necroinflammatory activity and genotype distribution. This observation suggests that the stage of hepatic fibrosis, rather than the grade (inflammation), is influenced by the presence of proline at codon 25 in patients with chronic hepatitis C.