Association of TLR7 single nucleotide polymorphisms with chronic HCV-infection and response to interferon-a-based therapy.
An efficient immune response against hepatitis C virus (HCV) is necessary to clear infection. As HCV is a single-stranded RNA virus, a role for TLR7 in the immune response against HCV is possible, and early clinical studies have demonstrated an antiviral effect of TLR7 stimulation. We tested the hypothesis that genetic variations of TLR7 are associated with chronic HCV-infection and outcome of therapy. The prevalence of three TLR7 variations was analysed in 978 patients with chronic HCV-infection, 898 patients with chronic liver disease of other aetiologies, and in 203 healthy controls. The prevalence of TLR7 variations was correlated with the response to interferon-alpha-based treatment in 544 patients with chronic HCV-infection. We analysed TLR7 polymorphisms by melting curve analysis and reconstructed haplotypes. The c.32A>T variation was over-represented in female patients with chronic HCV-infection compared to patients with other chronic liver diseases and to healthy controls (P< 0.05). In contrast, c.2403 G>A was less prevalent in male patients with chronic HCV-infection (P< 0.05). No association was observed for the third variant, c.1-120T>G. Haplotype analysis confirmed the differential distribution of TLR7 variants between the groups. Within the group of female patients with chronic HCV-infection, c.32T was predictive of an unfavourable outcome of interferon-alpha therapy (P< 0.05). This study reports the association of TLR7 variants with chronic HCV-infection and with the response to interferon-alpha therapy in patients with chronic HCV-infection. Our results suggest that variations of TLR7 impair the immune response to HCV and imply a gender-specific effect of this X-chromosomal variation.