Lymphocyte activation gene 3 negatively regulates the function of intrahepatic hepatitis C virus-specific CD8+ T cells

Background and Aim: Chronic hepatitis C (CHC) in humans caused by persistent hepatitis C virus (HCV) infection is a global public health problem. The functional exhaustion of HCV-specific CD8(+) T cells regulated by several inhibitory receptors has been shown to contribute to chronic HCV infection. Lymphocyte activation gene 3 (LAG-3), which is an inhibitory receptor, plays an important role in several chronic viral infections. However, its effect on the function of HCV-specific CD8(+) T cells is unclear. Methods: The expression of LAG-3 on the CD8(+) T cells in intrahepatic and peripheral lymphocytes from 17 CHC patients and 15 HCV-negative patients was analyzed by flow cytometry. The LAG-3 expression in CD8(+) T cells was downregulated or upregulated by lentivirus LAG-3 shRNA or lentivirus overexpressing LAG-3. After HCV peptide stimulation, flow cytometry was used to detect cell proliferation and cytokine (gamma-interferon [IFN-gamma], tumor necrosis factor-alpha [TNF-alpha], granzyme B, and perforin) production of CD8(+) T cells. Cytotoxicity functions of HCV-specific CD8(+) T cells were measured using a Cr-51 release assay. Results: The frequency of LAG-3-positive intrahepatic and peripheral CD8(+) T cells was higher in CHC patients, compared with HCV-negative patients. The cell proliferation, cytokine (IFN-gamma, TNF-alpha, granzyme B, and perforin) expression and cytotoxicity function of HCV-specific CD8(+) T cells in CHC patients were increased by the knocking down and blockade of LAG-3. In the LAG-3 overexpressed CD8(+) T cells, cell proliferation, cytokine (IFN-gamma, TNF-alpha, granzyme B, and perforin) expression, and cytotoxicity function were inhibited, while the LAG-3 blocking antibody reversed the inhibition. Conclusion: LAG-3 negatively regulated the function of HCV-specific CD8(+) T cells in CHC patients.