An unbalanced PD-L1/CD86 ratio in CD14++CD16+ monocytes is correlated with HCV viremia during chronic HCV infection

Circulating monocyte subsets with distinct functions play important roles in hepatitis C virus (HCV) infection. However, the mechanisms have not been well studied. In this study, we analyzed the distributions and phenotypic characteristics of three circulating monocyte subsets-CD14(++)CD16(-), CD14(++)CD16(+) and CD14(+/dim)CD16(+)-in chronic HCV-infected patients, HCV spontaneous resolvers and healthy controls, and we evaluated the possible link between HCV viremia and disease progression. Our results indicated that the frequency of the CD14(++)CD16(+) monocyte subset was decreased, and negatively correlated with HCV RNA and core antigen levels during chronic HCV infection. PD-L1 expression and the PD-L1/CD86 ratio in CD14(++)CD16(+) monocytes were higher during chronic HCV infection than in spontaneous HCV resolvers and healthy controls. The PD-L1/CD86 ratio positively correlated with HCV viral load and core antigen levels. Finally, PD-L1 was significantly increased, while cytokine secretions were dramatically decreased upon Toll-like receptor (TLR) ligand binding and HCV JFH-1stimulation. These findings indicates the compromised immune status of the CD14(++)CD16(+) monocytes during chronic HCV infection and provides new insights into the specific role of the CD14(++)CD16(+) monocytes and their significance in chronic HCV infection.