AIM: To analyze the polymorphisms of CTLA-4 gene involved in the response against hepatitis C virus(HCV) infection.METHODS: We recruited 500 hemodialysed patients from several hemodialysis centers, all HCV-antibody positive, spread over different regions of Tunisia, as part of a national survey in 2008 conducted in the laboratory of immunology at the Charles Nicolle hospital Tunisia, classified into two groups G1(PCR+) and G2(PCR-) according to the presence or absence of viral RNA. Of these patients, 307 were followed prospectively on a viral molecular level over a period from 2002 to 2008, divided into two groups based on the persistence and viral clearance. PCR-RFLP was performed for the analysis of SNPs(+49) A/G and(+6230) G/A CTLA-4 for these 500 patients and 358 healthy controls.RESULTS: Analysis of clinical and virological charac-teristics of our cohort suggests a nosocomial infection in our hemodialysed patients with transfusion history as a primary risk factor and a predominance of genotype 1b. The haplotype analysis revealed an increase of frequencies of GG(+49)/(CT60) CTLA-4 in the entire patients group compared to controls(P = 0.0036 and OR = 1.42; 95%CI: 1.12-1.79, respectively). This haplotype is therefore associated with susceptibility to HCV infection. CONCLUSION: Our study suggests a possible role of CTLA-4 polymorphisms in the outcome of HCV infection in the Tunisian hemodialysed population. AIM: To analyze the polymorphisms of CTLA-4 gene involved in the response to hepatitis C virus (HCV) infection. METHODS: We recruited 500 hemodialysed patients from several hemodialysis centers, all HCV-antibody positive, spread over different regions of Tunisia, as part of a national survey in 2008 conducted in the laboratory of immunology at the Charles Nicolle hospital Tunisia, classified into two groups G1 (PCR +) and G2 (PCR-) according to the presence or absence of viral RNA. Of these patients, 307 were followed by prospectively on a viral molecular level over a period from 2002 to 2008, divided into two groups based on the persistence and viral clearance. PCR-RFLP was performed for the analysis of SNPs (+49) A / G and (+6230) G / A CTLA-4 for these 500 patients and 358 healthy controls .RESULTS: Analysis of clinical and virological charac-teristics of our cohort suggests a nosocomial infection in our hemodialysed patients with transfusion history as a primary risk factor and a predominanc e of genotype 1b. The haplotype analysis revealed an increase of frequencies of GG (+49) / (CT60) CTLA-4 in the entire patients group compared to controls (P = 0.0036 and OR = 1.42; 95% CI: 1.12-1.79 , respectively). This haplotype is therefore associated with susceptibility to HCV infection. CONCLUSION: Our study suggests a possible role of CTLA-4 polymorphisms in the outcome of HCV infection in the Tunisian hemodialysed population.