Hepatitis B e Antigen Induces NKG2A+ Natural Killer Cell Dysfunction via Regulatory T Cell-Derived Interleukin 10 in Chronic Hepatitis B Virus Infection.

Qingqing Ma,Min Zhang,Dandan Sun,Meijuan Zheng,Tao Zhong,Ying Ye,Yufeng Gao,Qiong Lu,Lu Zong,Jun Cheng,Siyu Liu,Xiaoyu Dong,Yuanhong Xu,Changcheng Zhao

doi:10.3389/fcell.2020.00421

Abstract

Although persistent hepatitis B virus (HBV) infection is associated with natural killer (NK) cell dysfunction, it remains obscure whether HBV viral antigens are responsible for NK cell dysfunction in patients with chronic hepatitis B (CHB) infection. In this study, we found that the percentage of NK cells expressing the inhibitory receptor, NKG2A, was increased in CHB patients, and NKG2A blockade restored NK cell function. Furthermore, in CHB patients, the frequency of NK cells expressing NKG2A positively correlated with the number of regulatory T cells (Tregs) and production of interleukin-10 (IL-10) in these Tregs. Moreover, exposure of peripheral blood mononuclear cells (PBMCs) isolated from healthy controls to sera from CHB patients resulted in increased proportion of NKG2A+ NK cells; IL-10 blockade reduced the frequency of NKG2A+ NK cells while increasing the percentage of IFN-γ+ NK cells. In addition, stimulation of NK cells and Tregs from healthy controls with CHB sera together with anti-IL-10 antibody increased IFN-γ production in the culture supernatant. The frequencies of NKG2A+ NK cells and IL-10+ Tregs, along with serum levels of alanine transferase and HBV DNA, were significantly increased in CHB patients positive for the Hepatitis B e antigen (HBeAg, a marker of viral replication) when compared to HBeAg-negative CHB patients. Importantly, exposure of PBMCs from healthy controls to HBeAg resulted in increased IL-10 production but reduced levels of TNF and IFN-γ, and IL-10 blockade rescued the generation of TNF and IFN-γ in this assay. The reduced production of TNF and IFN-γ was also observed in NK cells and Tregs from healthy controls that were stimulated with HBeAg, while IL-10 blockade increased the secretion of these two cytokines. We conclude that HBeAg induces IL-10 production in Tregs, thereby leading to increased expression of NKG2A on NK cells, which contributes to NK cell dysfunction during CHB infection. These data suggest that HBeAg is associated with NK cell dysfunction in CHB.

Highlights

Hepatitis B virus (HBV) infection is a major public health problem worldwide and individuals with chronic HBV (CHB) infection are at high-risk for the development of cirrhosis and hepatocellular carcinoma (HCC) (Lozano et al, 2012; Maini and Peppa, 2013; Tian et al, 2013)
Expression of inhibitory receptor, NKG2A, was significantly increased in patients with CHB compared with healthy donors, while there was no difference in the expression of other natural killer (NK) cell receptors, including KIR3DL1, NKP46, NKP30, CD244, and NKG2D (Figures 1A,B) between patients with CHB and healthy controls
Both the mean fluorescence intensity and the absolute number of NKG2A+ NK cells were higher in peripheral blood from patients with CHB relative to healthy controls (Figures 1C,D), there was no significant difference in NKG2A expression on CD8+ T cells in patients with CHB compared with healthy controls (Supplementary Figures S2A,B)

Summary

Introduction

Hepatitis B virus (HBV) infection is a major public health problem worldwide and individuals with chronic HBV (CHB) infection are at high-risk for the development of cirrhosis and hepatocellular carcinoma (HCC) (Lozano et al, 2012; Maini and Peppa, 2013; Tian et al, 2013). CHB is associated with ineffective antiviral immune responses (Dienstag, 2008; Li et al, 2015), and accumulating evidence supports a relationship between CHB infection and impaired natural killer (NK) cell cytotoxicity and cytokine secretion (Martinet et al, 2012; Zheng et al, 2018). Despite this association, the mechanisms involved in NK cell dysfunction in CHB patients are yet to be clarified. High levels of NKG2A expression on NK cells leads to NK cell exhaustion and is associated with poor prognosis for patients with HCC (Sun et al, 2017). Anti-NKG2A treatment has been suggested to enhance NK cell activity in cancer vaccinations (Haanen and Cerundolo, 2018)

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