ARTICLE IN PRESS JID: HBPD [m5G;April 1, 2018;4:28] Hepatobiliary & Pancreatic Diseases International 000 (2018) 1–8 Contents lists available at ScienceDirect Hepatobiliary & Pancreatic Diseases International journal homepage: www.elsevier.com/locate/hbpd Original Article/Liver HBsAg stimulates NKG2D receptor expression on natural killer cells and inhibits hepatitis C virus replication Xiao-Xiao Wang, Xiao-Ben Pan, Jin-Chao Han, Xu Cong, Qian Jin, Xiang-Sha Kong, Lai Wei, Bo Feng ∗ Peking University People’s Hospital, Peking University Hepatology Institute, Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Diseases, No.11 Xizhimen South Street, Beijing 100044, China a r t i c l e i n f o Article history: Received 24 May 2017 Accepted 13 February 2018 Available online xxx Keywords: Hepatitis B surface antigen Hepatitis C virus Natural killer cells NKG2D a b s t r a c t Background: Higher hepatitis B surface antigen (HBsAg) facilitates hepatitis C virus (HCV) clearance in patients with hepatitis B virus (HBV)/HCV co-infection. We investigated the effect of exogenous HBsAg on the inhibition of HCV replication mediated by natural killer (NK) cells. Methods: After isolated from peripheral blood of 42 chronic hepatitis B (CHB) patients and 16 healthy individuals, NK cells were co-cultured with HCV-infected Huh7 cells, respectively, with or without HBsAg. Three days later, the co-cultured supernatants were collected and HCV RNA levels were measured by real- time quantitative PCR. NKG2D, NKp46 and NKG2A expression levels were measured by flow cytometry. NKG2D on NK cells from CHB responsive subgroup was blocked and HCV RNA levels were examined again. Results: HCV RNA levels in the co-cultured system were significantly reduced by NK cells isolated from healthy donors (P < 0.01) but not from CHB patients. However, HCV RNA levels in CHB cultures were significantly decreased following HBsAg addition (P < 0.05), whereas no such effect was seen in control cultures. No significant difference was observed in basic NKG2D expression between the CHB patients and healthy donors. On NK cells from CHB patients, the expression of NKG2D was increased significantly by HBsAg stimulation (P < 0.01), and higher than that from healthy controls (P < 0.05). HCV RNA levels were increased significantly after the blockage of NKG2D on NK cells from responsive CHB patients in the co-cultured system (P < 0.05). Conclusion: Exogenous HBsAg stimulated NKG2D expression on NK cells from CHB patients which inhibit HCV replication, suggesting that HBsAg may facilitate the clearance of HCV in patients with HBV/HCV co-infection. © 2018 First Affiliated Hospital, Zhejiang University School of Medicine in China. Published by Elsevier B.V. All rights reserved. Introduction Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection lead to serious health problems. These two viruses share the same transmission mechanism, thus co-infection is very common, partic- ularly in high endemic areas, amongst individuals with a high-risk of parenteral infection [1]. The prevalence of HBV/HCV co-infection is approximately 5−20% in patients whose hepatitis B surface anti- gen (HBsAg) are positive and 2−10% in HCV-positive patients [2]. A prevalence of overt HBV co-infection in HCV-positive patients was recently reported at 1.4% in the United States [1]. ∗ Corresponding author. E-mail address: fengbo@pkuph.edu.cn (B. Feng). Patients with HBV/HCV co-infection behave differently: acceler- ates liver disease progression and increases the risk of HCC. Haz- ard ratios (HRs) for HCC in cases of HBV/HCV co-infection are 6.7 times greater than in those of HBV mono-infection, and 11.1 times greater than in those of HCV mono-infection [3–5]. On the other hand, HCV RNA clearance rate in HBV/HCV co-infection individu- als was higher than that in HCV mono-infection patients in 14–21 years [6]. Our previous epidemiological survey [7] showed that in HBV/HCV co-infected patients, the spontaneous clearance of HCV was associated with the level of HBsAg. In all co-infected patients, HCV RNA levels in those with HBsAg-positive were lower than in those with HBsAg-negative. The proportion of HCV RNA clearance in patients with HBsAg-positive was significantly higher than that in patients with HBsAg-negative [8]. A large-scale study in uremic patients in southern taiwan indicated that if the serum level of https://doi.org/10.1016/j.hbpd.2018.03.010 1499-3872/© 2018 First Affiliated Hospital, Zhejiang University School of Medicine in China. Published by Elsevier B.V. All rights reserved. Please cite this article as: X.-X. Wang et al., HBsAg stimulates NKG2D receptor expression on natural killer cells and inhibits hepatitis C virus replication, Hepatobiliary & Pancreatic Diseases International (2018), https://doi.org/10.1016/j.hbpd.2018.03.010