R753Q Single-Nucleotide Polymorphism Impairs Toll-Like Receptor 2 Recognition of Hepatitis C Virus Core and Nonstructural 3 Proteins

Background. Hepatitis C virus (HCV) core and nonstructural (NS) 3 proteins induce inflammation and immunity through a Toll-like receptor (TLR) 2-dependent pathway. Individuals with the R753Q single-nucleotide polymorphism (SNP) in the TLR2 gene have increased the risk of allograft failure after liver transplantation for chronic hepatitis C. Methods. To test the hypothesis that R753Q SNP impairs TLR2 recognition of HCV proteins, a series of in vitro experiments were performed wherein stable clones of wild-type TLR2-deficient human embryonic kidney (HEK) 293 cells and HEK293 cells transfected with wild-type (HEK293-TLR2) or variant TLR2 genes (HEK293-TL122-R753Q) were stimulated with HCV core and NS3 proteins. Cellular activation was assessed by nuclear factor-kappa B-driven luciferase activity, cytokine secretion, and gene upregulation. Results. Compared with TLR2-deficient HEK293 cells, HEK293-TLR2 cells had marked nuclear factor-kappa B-driven luciferase activity, had modest to marked upregulation in TLR2 signaling-associated genes, and secreted large quantities of interleukin-8 during exposure to HCV core and NS3 proteins. In contrast, HEK293-TLR2-R753Q cells did not respond to stimulation with HCV and behaved similarly like TLR2-deficient HEK293 cells. Conclusion. R753Q SNP impairs TLR2-mediated immune recognition of HCV core and NS3 proteins. This biologic defect may account for the predisposition of patients to develop allograft failure after liver transplantation for chronic hepatitis C.