Natural killer cell activation contributes to hepatitis B viral control in a mouse model

COVID-19 Vaccination Alters NK Cell Dynamics and Transiently Reduces HBsAg Titers Among Patients With Chronic Hepatitis B

Coronavirus disease 2019 (COVID-19) vaccination may non-specifically alter the host immune system. This study aimed to evaluate the effect of COVID-19 vaccination on hepatitis B surface Ag (HBsAg) titer and host immunity in chronic hepatitis B (CHB) patients. Consecutive 2,797 CHB patients who had serial HBsAg measurements during antiviral treatment were included in this study. Changes in the HBsAg levels after COVID-19 vaccination were analyzed. The dynamics of NK cells following COVID-19 vaccination were also examined using serial blood samples collected prospectively from 25 healthy volunteers. Vaccinated CHB patients (n=2,329) had significantly lower HBsAg levels 1-30 days post-vaccination compared to baseline (median, -21.4 IU/ml from baseline), but the levels reverted to baseline by 91-180 days (median, -3.8 IU/ml). The velocity of the HBsAg decline was transiently accelerated within 30 days after vaccination (median velocity: -0.06, -0.39, and -0.04 log10 IU/ml/year in pre-vaccination period, days 1-30, and days 31-90, respectively). In contrast, unvaccinated patients (n=468) had no change in HBsAg levels. Flow cytometric analysis showed that the frequency of NK cells expressing NKG2A, an NK inhibitory receptor, significantly decreased within 7 days after the first dose of COVID-19 vaccine (median, -13.1% from baseline; p<0.001). The decrease in the frequency of NKG2A+ NK cells was observed in the CD56dimCD16+ NK cell population regardless of type of COVID-19 vaccine. COVID-19 vaccination leads to a rapid, transient decline in HBsAg titer and a decrease in the frequency of NKG2A+ NK cells.

Prospects for NK-based immunotherapy of chronic HBV infection

Effective and long-term treatment is required for controlling chronic Hepatitis B Virus (HBV) infection. Natural killer (NK) cells are antiviral innate lymphocytes and represent an essential arm of current immunotherapy. In chronic HBV (CHB), NK cells display altered changes in phenotypes and functions, but preserve antiviral activity, especially for cytolytic activity. On the other hand, NK cells might also cause liver injury in the disease. NK -based immunotherapy, including adoptive NK cell therapy and NK -based checkpoint inhibition, could potentially exploit the antiviral aspect of NK cells for controlling CHB infection while preventing liver tissue damage. Here, we review recent progress in NK cell biology under the context of CHB infection, and discuss potential NK -based immunotherapy strategies for the disease.

Expansion of dysfunctional CD56-CD16+ NK cells in chronic hepatitis B patients

BACKGROUND & AIMS

Natural killer (NK) cells are primary innate effector cells that play an important role in the control of human viral infections. During chronic viral infection, NK cells undergo significant changes in phenotype, function and subset distribution, including the appearance of CD56-CD16+ (CD56-) NK cells, previously identified in chronic human immunodeficiency virus (HIV) and hepatitis C virus infection. However, the presence of CD56- NK cells in the pathogenesis of chronic hepatitis B (CHB) remains unknown.

METHODS

Phenotype and function of CD56- NK cells from patients with CHB (n = 28) were assessed using flow cytometry and in vitro stimulation with HBV antigen.

RESULTS

CHB patients had a higher frequency of CD56- NK cells compared to healthy controls in peripheral blood (6.2% vs 1.4%, P < .0001). Compared to CD56+ NK cells, CD56- NK cells had increased expression of inhibitory receptors, and reduced expression of activating receptors, as measured by MFI and qPCR. CD56- NK cells were less responsive to target cell and cytokine stimulation compared to their CD56+ counterparts. In addition, CD56- NK cells demonstrated defective dendritic cells (DCs) interactions resulting in reduced DCs maturation, lower expression of NK CD69 and impaired capacity of NK cells to eliminate immature DCs in co-culture studies. Finally, frequency of CD56- NK cells was positively correlated with serum HBV DNA levels.

CONCLUSION

Chronic HBV infection induces the expansion of highly dysfunctional of CD56- NK cells that likely contribute to inefficient innate and adaptive antiviral immune response in chronic HBV infection.

Natural killer cell receptor variants and chronic hepatitis B virus infection in the Vietnamese population

OBJECTIVES

Genes of host immunity play an important role in disease pathogenesis and are determinants of clinical courses of infections, including hepatitis B virus (HBV). Killer-cell immunoglobulin-like receptor (KIR), expressed on the surface of natural killer cells (NK), regulate NK cell cytotoxicity by interacting with human leukocyte antigen (HLA) class I molecules and are candidates for influencing the course of HBV. This study evaluated whether variations in KIR gene content and HLA-C ligands are associated with HBV and with the development of liver cirrhosis and hepatocellular carcinoma.

METHODS

A Vietnamese study cohort (HBV n = 511; controls n = 140) was genotyped using multiplex sequence-specific polymerase chain reaction (PCR-SSP) followed by melting curve analysis.

RESULTS

The presence of the functional allelic group of KIR2DS4 was associated with an increased risk of chronic HBV (OR = 1.86, p^corr = 0.02), while KIR2DL2+HLA-C1 (OR = 0.62, p^corr = 0.04) and KIR2DL3+HLA-C1 (OR = 0.48, p^corr = 0.04) were associated with a decreased risk. The pair KIR2DL3+HLA-C1 was associated with liver cirrhosis (OR = 0.40, p^corr = 0.01). The presence of five or more activating KIR variants was associated with hepatocellular carcinoma (OR = 0.53, p^corr = 0.04).

CONCLUSIONS

KIR gene content variation and combinations KIR-HLA influence the outcome of HBV infection.

NKG2C+ natural killer cell function improves the control of HBV replication in individuals with acute HIV infection coinfected with HBV

Individuals infected with hepatitis B virus (HBV) are often coinfected with human immunodeficiency virus (HIV). However, individuals with chronic HBV infection living with acute HIV infection have a significantly lower HBV viral load, along with higher HBeAg and HBsAg loss than HBV-infected individuals alone. Here, we investigated the possible role of natural killer cells (NK cell) function in this progressive course to explore the relationship between phenotypic/functional changes in NK cells during acute HIV infection and HBV clearance in patients with HIV/HBV coinfection.Peripheral blood NK cells from 38 patients with primary HIV infection, including 20 with untreated HIV infection and 18 treatment-naïve patients with HIV/HBV coinfection and 16 patients with chronic HBV infection, were enrolled in this study.We found that the HIV/HBV-coinfected individuals had higher levels of NK cells than the HBV-infected individuals, due to expansion of the CD56 NK cell population. The proportion of NK cells in CD56 and CD56 NK subsets was not found significant difference between HIV/HBV-coinfected and HBV-infected individuals. However, NKG2C levels on NK cells and subsets were significantly higher in HIV/HBV-coinfected individuals than in HBV-infected individuals, whereas NKG2A levels were unaffected or decreased. In addition, the levels of degranulation CD107a, cytotoxicity and IFN-γ production of NK cells were increased in HIV/HBV-coinfected individuals than in HBV-infected individuals. The level of IL-10 production of NK cells was decreased in HIV/HBV-coinfected individuals than in HBV-infected individuals. Furthermore, the level of HBV-DNA was inversely correlated with the proportion of NKG2C and NKG2CNKG2A NK cells, while positively correlated with the proportion of NKG2A and NKG2CNKG2A NK cells. IFN-γ production was inversely correlated with levels of HBV-DNA, but the CD107a expression and IL-10 production of NK cells were not correlated with HBV-DNA levels.These results demonstrate that the upregulation of NKG2C expression, but not of NKG2A expression on the surface of NK cells increases cytolytic capacity and the amounts of cytokines produced and may play a crucial role in HBV clearance during HIV/HBV-coinfection.

IL-33 Inhibits Hepatitis B Virus through Its Receptor ST2 in Hydrodynamic HBV Mouse Model

Interleukin-33 has been demonstrated to be associated with liver damage. However, its potential value in hepatitis B virus (HBV) infection remains unknown. This study was designed to investigate the role of IL-33 in hydrodynamic HBV mouse model. Different doses of IL-33 were used to treat HBV wild-type, ST2 knockout, CD8+ T depletion, NK depletion C57BL/6 mice and C.B-17 SCID and nod SCID mouse, respectively. The concentrations of HBV DNA, HBsAg, HBeAg, and molecules related to liver function were detected in the collected serum at different time points from model mice. Intrahepatic HBcAg was visualized by immunohistochemical staining of liver tissues. In vitro, hepG2 cells were transfected with pAAV-HBV 1.2, then treated with IL-33. The results showed that IL-33 significantly reduced HBV DNA and HBsAg in a dose-dependent manner in HBV wild-type mice. However, in the IL-33 specific receptor ST2 knockout mice, their antiviral effects could not be exerted. Through immunodeficient animal models and in vivo immune cell depletion mouse model, we found that IL-33 could not play antiviral effects without NK cells. Moreover, IL-33 could reduce the levels of HBsAg and HBeAg in the supernatant of HBV-transfected hepG2 cells in vitro. Our study revealed that IL-33 could inhibit HBV through ST2 receptor in the HBV mouse model, and this effect can be impaired without NK cell. Additionally, IL-33 had the direct anti-HBV effect in vitro, indicating that IL-33 could be a potent inducer of HBV clearance and a promising drug candidate.

KLRG1+ natural killer cells exert a novel antifibrotic function in chronic hepatitis B

BACKGROUND & AIMS

Natural killer (NK) cells are known to exert strong antiviral activity. Killer cell lectin-like receptor subfamily G member 1 (KLRG1) is expressed by terminally differentiated NK cells and KLRG1-expressing lymphocytes are known to expand following chronic viral infections. We aimed to elucidate the previously unknown role of KLRG1 in the pathogenesis of chronic hepatitis B (CHB).

METHODS

KLRG1+ NK cells were taken from the blood and liver of healthy individuals and patients with CHB. The phenotype and function of these cells was assessed using flow cytometry and in vitro stimulation.

RESULTS

Patients with CHB had a higher frequency of KLRG1+ NK cells compared to healthy controls (blood 13.4 vs. 2.3%, p <0.0001 and liver 23.4 vs. 2.6%, p <0.01). KLRG1+ NK cells were less responsive to K562 and cytokine stimulation, but demonstrated enhanced cytotoxicity (9.0 vs. 4.8%, p <0.05) and IFN-γ release (8.0 vs. 1.5%, p <0.05) via antibody dependent cellular cytotoxicity compared to their KLRG1- counterparts. KLRG1+ NK cells possessed a mature phenotype, demonstrating stronger cytolytic activity and IFN-γ secretion against hepatic stellate cells (HSCs) than KLRG1- NK cells. Moreover, KLRG1+ NK cells more effectively induced primary HSC apoptosis in a TRAIL-dependent manner. Increased KLRG1+ NK cell frequency in the liver and blood was associated with lower fibrosis stage (F0/F1) in patients with CHB. Finally, the expression of CD44, degranulation and IFN-γ production were all increased in KLRG1+ NK cells following stimulation with osteopontin, the CD44 ligand, suggesting that HSC-derived osteopontin may cause KLRG1+ NK cell activation.

CONCLUSIONS

KLRG1+ NK cells likely play an antifibrotic role during the natural course of CHB infection. Harnessing this antifibrotic function may provide a novel therapeutic approach to treat liver fibrosis in patients with CHB.

LAY SUMMARY

Individuals that are chronically infected with hepatitis B virus (HBV) possess an increased number of immune cells, called natural killer (NK) cells expressing the surface marker KLRG1 in the blood and liver. Here, we demonstrate that these specific NK cells are able to kill activated stellate cells in the liver. Because activated stellate cells contribute to liver scarring, i.e. fibrosis, and subsequent liver dysfunction in individuals with chronic HBV infection, KLRG1+ NK cells are a novel immune cell type that can limit liver scarring.

CCR5 deficiency enhances hepatic innate immune cell recruitment and inflammation in a murine model of acute hepatitis B infection

Human genetic studies demonstrate a link between the 32-bp deletion that produces a nonfunctional CCR5 receptor and enhanced recovery from acute hepatitis B virus (HBV) infection. To investigate the role of CCR5 in immune responses to acute HBV, we intravenously infected Ccr5^+/+ (WT) and Ccr5^-/- (KO) mice with a replication-incompetent adenovirus containing the overlapping HBV1.3 construct (AdHBV), or vector control. At day 3 following AdHBV infection, analysis of intrahepatic leukocytes (IHL) showed KO mice had increased CD11b⁺ NK cells compared to WT (18.2% versus 7.6% of live IHL, P < 0.01). These CD11b⁺ NK cells were nonresident (CD49a^- ) and had capacity to degranulate and produce IFN-γ following stimulation. At day 3, plasma CXCL10 was significantly increased in KO, but not WT, mice receiving AdHBV as compared to vector control, while CXCR3 expression on hepatic CD11b⁺ NK cells in AdHBV-treated KO mice was significantly lower than that in uninfected mice, suggesting these NK cells are recruited along the CXCL10-CXCR3 axis. At days 7 and 14, no differences between genotypes were observed in number, or HBV-specific function, of intrahepatic CD8⁺ T cells. Instead, at day 14, KO mice had increased intrahepatic proinflammatory monocytes compared to WT mice (17.56% versus 6.57% of live IHL, P = 0.014), corresponding with an increase in plasma alanine aminotransferase and intrahepatic IL-1β observed in KO mice. Taken together, these findings demonstrate that loss of CCR5 signaling drives a more robust inflammatory liver microenvironment early in acute HBV infection via enrichment of hepatic innate immune cells.

Natural Killer Cell Dysfunction in Hepatocellular Carcinoma: Pathogenesis and Clinical Implications

Hepatocellular carcinoma (HCC) is currently the third leading cause of malignancy-related mortalities worldwide. Natural killer (NK) cells are involved in the critical role of first line immunological defense against cancer development. Defects in NK cell functions are recognized as important mechanisms for immune evasion of tumor cells. NK cell function appears to be attenuated in HCC, and many previous reports suggested that NK cells play a critical role in controlling HCC, suggesting that boosting the activity of dysfunctional NK cells can enhance tumor cell killing. However, the detailed mechanisms of NK cell dysfunction in tumor microenvironment of HCC remain largely unknown. A better understanding of the mechanisms of NK cell dysfunction in HCC will help in the NK cell-mediated eradication of cancer cells and prolong patient survival. In this review, we describe the various mechanisms underlying human NK cell dysfunction in HCC. Further, we summarize current advances in the approaches to enhance endogenous NK cell function and in adoptive NK cell therapies, to cure this difficult-to-treat cancer.

Perforin inhibition protects from lethal endothelial damage during fulminant viral hepatitis

CD8 T cells protect the liver against viral infection, but can also cause severe liver damage that may even lead to organ failure. Given the lack of mechanistic insights and specific treatment options in patients with acute fulminant hepatitis, we develop a mouse model reflecting a severe acute virus-induced CD8 T cell-mediated hepatitis. Here we show that antigen-specific CD8 T cells induce liver damage in a perforin-dependent manner, yet liver failure is not caused by effector responses targeting virus-infected hepatocytes alone. Additionally, CD8 T cell mediated elimination of cross-presenting liver sinusoidal endothelial cells causes endothelial damage that leads to a dramatically impaired sinusoidal perfusion and indirectly to hepatocyte death. With the identification of perforin-mediated killing as a critical pathophysiologic mechanism of liver failure and the protective function of a new class of perforin inhibitor, our study opens new potential therapeutic angles for fulminant viral hepatitis.

CD8 T cells can protect the liver from viral infection, but can also result in severe liver damage and organ failure. Here, the authors develop a mouse model reflecting fulminant CD8 T cell mediated viral hepatitis, which occurs in a perforin-dependent manner that is protected by the use of perforin inhibitors.

NK cells in liver homeostasis and viral hepatitis

As an important member of the innate immune system, natural killer (NK) cells are well known for their rapid and efficient immune responses against infectious agents and tumors. NK cells are widely distributed throughout the body and are particularly enriched within the liver, where they display unique phenotypic and functional properties, playing important roles in various liver diseases. Herein, we present an overview of liver NK cell properties with regard to phenotype, function, and subset composition at steady state, and we also summarize the complex reciprocal interactions between liver NK cells and other cell types within the local environment of the liver. We also provide an overview of recent advances demonstrating the roles of NK cells in viral hepatitis, including a discussion of NK cell altered states and their beneficial versus harmful effects during hepatitis B virus and hepatitis C virus infection.

Immune function of plasmacytoid dendritic cells, natural killer cells, and their crosstalk in HBV infection

Chronic hepatitis B virus infection is a major health problem, with over 245 million chronic carriers worldwide. This persistent infection is thought to be associated with inefficient innate and adaptive immune responses. Natural killer cells (NK cells) and plasmacytoid dendritic cells (pDCs) are the major innate immune cells which respond to viral infection at the early phase and are considered major components of the antiviral immune response. In this review, we summarize recent findings regarding the role of NK cells, pDCs, and their cross-talk in HBV infection and its chronicity. Although the data regarding the biological function of pDCs and NK cells in HBV infection is still controversial, many studies show that in chronic HBV infection, the cytotoxicity of NK cells is retained, while their capacity to secrete cytokines is strongly impaired. In addition, interferon-α production by pDCs is impaired during chronic HBV infection, and the virus interferes with pDC-NK cell interaction.

Interleukin-28B dampens airway inflammation through up-regulation of natural killer cell-derived IFN-γ

Interleukin-28A (IL-28A) modulates CD11c+ dendritic cell (DC) function and promotes type 1T helper (Th1) differentiation, thus suppressing allergic airway diseases. However, the function of the IL-28A isoform IL-28B in these diseases remains largely unknown. In this study, we revealed a novel role of IL-28B in inducing type 1 immunity and protecting against ovalbumin (OVA)-induced allergic asthma in mice. IL-28B overexpression in wild-type mice promoted natural killer (NK) cell polarization in the lung, leading to the increased number of interferon (IFN)-γ-producing NK1 cells as well as Th1 differentiation. Importantly, IL-28B overexpression had no protective effect on OVA-induced asthma in IFN-γ-knockout (IFN-γ−/−) mice. These results demonstrate that IL-28B ameliorates experimental allergic asthma via enhancing NK cell polarization, which might be useful for prevention and treatment of allergic asthma.