Effect of gMDSCs on natural killer cell functionality in chronic hepatitis C patients treated with direct-acting antiviral agents

Abstract

Objective: To investigate the changes of natural killer(NK) cell function, and clarify the effect of granulocytic myeloid derived suppressor cells (G-MDSCs) on NK cell functionality in patients with treatment-naive chronic hepatitis C (CHC) who were cured by direct-acting antiviral agents (DAAs). Methods: Thirteen treatment-naive CHC patients and 13 healthy controls were prospectively included in this study from March 2016 to January 2017. They were divided into case group and control group, respectively. The patients of case group,6 males and 7 females aged 21-65 years old with an average of (37±14),were treated with daclatasvir and asunaprevir combination (DCV/ASV) at the Department of Infectious Diseases, Fifth Medical Center of Chinese PLA General Hospital. While 13 healthy individuals, 6 males and 7 females aged 21-57 (36±11) years old, were enrolled as healthy controls(control group). Flow cytometry was used to determine the immunological characteristics of peripheral blood NK cells subset, and detect the frequencies of gMDSCs in peripheral blood of people in two groups. It was specifically notes that CHC patients of case group would be detected before, during and after treatment. The correlations between gMDSCs and each NK cell subset function were also examined. The impact of gMDSCs on NK cell functionalities and the relevant regulatory mechanisms were explored using co-culture experiments of sorted NK cells and gMDSCs in vitro. Results: Compared with healthy controls, the decreased IFN-γ production[M(Q1,Q3)] [3.182 (2.757, 4.237) vs 6.675 (4.476, 8.280),1.434 (1.127, 2.434) vs 3.045 (1.680, 4.856), 2.611 (1.749, 3.498) vs 5.160 (4.232, 7.683)] and increased CD107a degranulation [9.314 (7.838, 13.543) vs 3.480 (2.938, 6.824), 2.544 (1.366, 4.768) vs 0.552 (0.408, 1.560), 10.339 (9.145, 12.534) vs 3.488 (3.117, 5.651)] (all P<0.05) were found on NK cell and its subsets. The frequencies of gMDSCs and plasma concentration of arginase-1 in CHC patients was significantly higher than that in healthy controls [7.050 (4.180, 12.538) vs 1.440 (0.444, 2.261), 114.278 (68.492, 163.724) vs 64.753 (50.809, 93.278)](all P<0.05). The production of IFN-γ was increased and the secretion of CD107a was decreased in NK cell and its subsets after DAAs treatment (P<0.05). The frequencies of gMDSCs and plasma arignase I levels were also decreased in CHC patients treated with DAAs (P<0.05).The results of the study indicated that the frequencies of G-MDSCs were inversely associated with the levels of IFN-γproduction of NK cells and CD56dim NK cells in CHC patients (r=0.668, -0.750, respectively, both P<0.05). In addition, the frequencies of gMDSCs were positively associated with the expression of CD107a in the CD56bright NK cell subset (r=0.711, P=0.021). In vitro, the inhibition of gMDSCs on the IFN-γ production of NK cells was demonstrated in the co-culture experiments of sorted NK cells and gMDSCs, and blocking arginase I can significantly increase the ability of NK cells to produce IFN-γ, restore NK cell IFN-γ production. Conclusions: gMDSCs in peripheral blood of CHC patients has been shown to suppress NK cell IFN-γ production in an arginase I-dependent manner. Direct-acting antiviral-mediated clearance of HCV is associated with the normalization of NK cell function and gMDSCs frequency.