C형 간염바이러스의 NS3 세린 프로테아제를 통한 자연살해세포 활성의 억제

Hepatitis C virus (HCV) infection is characterized by a high frequency of chronic cases owing to the impairment of innate and adaptive immune responses. The modulation of natural killer (NK) cell functions by HCV leads to an impaired innate immune response. However, the underlying mechanisms and roles of HCV proteins in this immune evasion are controversial, especially in the early phase of HCV infection. To investigate the role of HCV non-structural proteins especially NS3 in the impairment of NK functions, NK cells were isolated from the peripheral blood mononuclear cell (PBMC) by negative selection. To assess the direct cytotoxicity and IFN-γ production capability of NK cells, NK cells were co-cultured with uninfected, HCV-infected, HCV-NS3 expressing construct-transfected Huh-7.5 cells, or HCV-NS replicon cells. To determine the effect of an NS3 serine protease inhibitor, HCV-infected Huh-7.5 cells were treated with BILN-2061. Then, NK cells were harvested and further co-cultured with K-562 target cells. NK cell functions were analyzed by flow cytometry (FACS) and enzyme-linked immunosorbent assay (ELISA). When co-cultured with HCV-infected Huh-7.5 cells, the natural cytotoxicity and IFN-γ production capability of NK cells were significantly reduced. NK cell functions were inhibited to similar levels upon co-culture with HCV-NS replicon cells, HCV-NS3 expressing construct-transfected Huh-7.5 cells, and HCV-infected Huh-7.5 cells. These reductions were restored by BILN-2061-treatment. Furthermore, BILN-2061 treatment significantly increased degranulation against K-562 target cells and IFN-γ productivity in NK cells. Consistent with these findings, the expression levels of activating NK cell receptors, such as NKp46 and NKp30, were also increased by BILN-2061 treatment. Together, in HCV-infected Huh-7.5 cells, the serine protease NS3 may play a role in the abrogation of NK cell functions in the early phase of infection through downregulation of NKp46 and NKp30 receptors on NK cells. These results suggest that NS3 represents a novel drug target for the treatment of HCV infections.open박