Altered Immune Profiles of Natural Killer Cells in Chronic Hepatitis B Patients: A Systematic Review and Meta-Analysis

IL-21 collaborates with anti-TIGIT to restore NK cell function in chronic HBV infection

Available therapies for chronic hepatitis B virus (HBV) infection are not satisfying, and interleukin-21 (IL-21) and checkpoint inhibitors are potential therapeutic options. However, the mechanism underlying IL-21 and checkpoint inhibitors in treating chronic HBV infection is unclear. To explore whether IL-21 and checkpoint inhibitors promote HBV clearance by modulating the function of natural killer (NK) cells, we measured the phenotypes and functions of NK cells in chronic HBV-infected patients and healthy controls on mRNA and protein levels. We found that chronic HBV infection disturbed the transcriptome of NK cells, including decreased expression of KLRK1, TIGIT, GZMA, PRF1, and increased expression of CD69. We also observed altered phenotypes and functions of NK cells in chronic HBV-infected patients, characterized by decreased NKG2D expression, increased TIGIT expression and impaired interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α) production. Furthermore, these alterations cannot be restored by telbivudine treatment but can be partially restored by IL-21 and anti-TIGIT stimulation. IL-21 upregulated the expression of activating receptor CD16, CD69, and NKG2D on NK cells, enhanced IFN-γ production, cytolysis, and proliferation of NK cells, while anti-TIGIT promoted IFN-γ production in CD56dim subset exclusively in chronic HBV infected patients. Additionally, IL-21 was indispensable for anti-TIGIT in HBsAg clearance in mice bearing HBV. It enhanced IFN-γ production in splenic NK cells rather than intrahepatic NK cells, indicating a brand-new mechanism of IL-21 in HBV clearance when combined with anti-TIGIT. Overall, our findings contribute to the design of immunotherapy through enhancing the antiviral efficacy of NK cells in chronic HBV infection.

NK cell phenotypic profile during active TB in people living with HIV-evolution during TB treatment and implications for bacterial clearance and disease severity

Natural killer (NK) cells, key effector cells of the innate immune system, play an important role in the clearance and control of Mycobacterium tuberculosis and HIV infections. Here, we utilized peripheral blood specimens from the Improving Retreatment Success CAPRISA 011 study to characterize NK cell phenotypes during active TB in individuals with or without HIV co-infection. We further assessed the effects of TB treatment on NK cell phenotype, and characterized the effects of NK cell phenotypes during active TB on mycobacterial clearance and TB disease severity measured by the presence of lung cavitation. TB/HIV co-infection led to the expansion of functionally impaired CD56neg NK cell subset. TB treatment completion resulted in restoration of total NK cells, NK cell subset redistribution and downregulation of several NK cell activating and inhibitory receptors. Higher percentage of peripheral CD56bright cells was associated with longer time to culture conversion, while higher expression of NKp46 on CD56dim NK cells was associated with lower odds of lung cavitation in the overall cohort and the TB/HIV co-infected participants. Together these results provide a detailed description of peripheral NK cells in TB and TB/HIV co-infection and yield insights into their role in TB disease pathology.

Hepatitis B functional cure and immune response

Hepatitis B virus (HBV) is a hepatotropic virus, which damage to hepatocytes is not direct, but through the immune system. HBV specific CD4⁺ T cells can induce HBV specific B cells and CD8⁺ T cells. HBV specific B cells produce antibodies to control HBV infection, while HBV specific CD8⁺ T cells destroy infected hepatocytes. One of the reasons for the chronicity of HBV infection is that it cannot effectively activate adoptive immunity and the function of virus specific immune cells is exhausted. Among them, virus antigens (including HBV surface antigen, e antigen, core antigen, etc.) can inhibit the function of immune cells and induce immune tolerance. Long term nucleos(t)ide analogues (NAs) treatment and inactive HBsAg carriers with low HBsAg level may "wake up" immune cells with abnormal function due to the decrease of viral antigen level in blood and liver, and the specific immune function of HBV will recover to a certain extent, thus becoming the "dominant population" for functional cure. In turn, the functional cure will further promote the recovery of HBV specific immune function, which is also the theoretical basis for complete cure of hepatitis B. In the future, the complete cure of chronic HBV infection must be the combination of three drugs: inhibiting virus replication, reducing surface antigen levels and specific immune regulation, among which specific immunotherapy is indispensable. Here we review the relationship, mechanism and clinical significance between the cure of hepatitis B and immune system.

Peripheral Immune Cells Exhaustion and Functional Impairment in Patients With Chronic Hepatitis B

After infection of hepatitis B virus (HBV), the virus induces a variety of immune disorders in the host, leading to immune escape and, finally, the chronicity of the disease. This study investigated immune cell defects and functional impairment in patients with chronic hepatitis B (CHB). We analyzed the percentage, function, and phenotypes of various immune cell subpopulations in the peripheral blood along with the concentrations of cytokines in the plasma. We compared the results between patients with CHB and healthy individuals. It was found that in patients with CHB, the cell function was impaired and, there was increased expression of inhibitory receptors, such as NKG2A and PD-1 in both NK and T cells. The impairment of function was mainly in cytokine secretion, and the cytotoxicity was not significantly diminished. We also found that the proportion of dendritic cells (DC) decreased and regulatory B cells (Breg) increased in CHB. In addition, the Breg cells were negatively correlated with T cell cytokine and positively correlated with ALT and HBV viral load. Taken together, various disorders and functional impairments were found in the immune cells of peripheral blood in CHB patients, especially NK and T cells. These cells showed exhaustion and the increase of regulatory B cells may be one of the reasons for this phenomenon.

Serum HBV pregenomic RNA exhibited opposite associations with NKdim and NKbright cell immunity in treatment-naïve chronic hepatitis B patients

Hepatitis B virus (HBV) pregenomic RNA (pgRNA) is a new biomarker that reflects HBV replication, but its relationship with natural killer (NK) cell immunity in chronic hepatitis B (CHB) is unknown. We assessed serum HBV pgRNA levels in 323 CHB patients by reverse transcription-polymerase chain reaction, assessed cytokine production and activation and inhibitory markers of NK cells by flow cytometry, and measured serum cytokines by enzyme-linked immunosorbent assays (ELISAs). Among the different CHB phases, the serum HBV pgRNA level was highest in the immune-tolerant (IT) and immune-active (IA) phases. Regarding NK and NKdim cells, HBV pgRNA was negatively associated with frequencies, but positively associated with NKp44 and NKp46 expression (activation markers). Regarding NKbright cells, serum HBV pgRNA was positively associated with frequency and programmed cell death protein 1 (PD1) expression (inhibitory marker), but negatively associated with NKp44 and NKp46. Serum HBV pgRNA was not associated with NKp30 (activation marker) on NK cells or subsets. Lastly, serum HBV pgRNA was positively correlated with the levels of serum IL-7 and IL-12P40 (NK cell-promoting cytokines) and negatively correlated with serum prostaglandin E2 (PGE2) level (which negatively regulates NK cells). In conclusion, we found varied relationships between serum HBV pgRNA and NK cells and subsets, indicating that HBV pgRNA may play a complicated role in NK cell-related immunity, providing new information on HBV and host immunity.

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.

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.

Persistent Replication of HIV, Hepatitis C Virus (HCV), and HBV Results in Distinct Gene Expression Profiles by Human NK Cells

Natural killer (NK) cells during chronic viral infection have been well studied in the past. We performed an unbiased next-generation RNA-sequencing approach to identify commonalities or differences of the effect of HIV, HCV, and HBV viremia on NK cell transcriptomes. Using cell sorting, we obtained CD3^- CD56⁺ NK cells from blood of 6 HIV-, 8 HCV-, and 32 HBV-infected patients without treatment. After library preparation and sequencing, we used an in-house analytic pipeline to compare expression levels with matched healthy controls. In NK cells from HIV-, HCV-, and HBV-infected patients, transcriptome analysis identified 272, 53, and 56 differentially expressed genes, respectively (fold change, >1.5; q-value, 0.2). Interferon-stimulated genes were induced in NK cells from HIV/HCV patients, but not during HBV infection. HIV viremia downregulated ribosome assembly genes in NK cells. In HBV-infected patients, viral load and alanine aminotransferase (ALT) variation had little effect on genes related to NK effector function. In conclusion, we compare, for the first time, NK cell transcripts of viremic HIV, HCV, and HBV patients. We clearly demonstrate distinctive NK cell gene signatures in three different populations, suggestive for a different degree of functional alterations of the NK cell compartment compared to healthy individuals.IMPORTANCE Three viruses exist that can result in persistently high viral loads in immunocompetent humans: human immunodeficiency virus (HIV), hepatitis C virus, and hepatitis B virus. In the last decades, by using flow cytometry and in vitro assays on NK cells from patients with these types of infections, several impairments have been established, particularly during and possibly contributing to HIV viremia. However, the background of NK cell impairments in viremic patients is not well understood. In this study, we describe the NK cell transcriptomes of patients with high viral loads of different etiologies. We clearly demonstrate distinctive NK cell gene signatures with regard to interferon-stimulated gene induction and the expression of genes coding for activation markers or proteins involved in cytotoxic action, as well immunological genes. This study provides important details necessary to uncover the origin of functional and phenotypical differences between viremic patients and healthy subjects and provides many leads that can be confirmed using future in vitro manipulation experiments.

The relationship between neopterin and hepatitis B surface antigen positivity

Hepatitis B is a life-threatening viral liver infection caused by the hepatitis B virus. Neopterin is regarded as an immunologic biomarker of several diseases related to activation of the cellular immune system. Hepatitis B infection is associated with increased production of cellular immune system markers. We aimed to investigate whether there is a relationship between hepatitis B surface antigen-positivity (HBsAg +) and neopterin to determine the role of neopterin in the early diagnosis of hepatitis B infections. Seventy-two HBsAg (+) patients with normal liver function tests and forty-three controls were included in the study. Neopterin levels were 17.6 ± 0.13 nmol/L in HBsAg (+) patients; and 9.12 ± 0.09 nmol/L in infection-free controls, respectively. Compared to the control group, a statistically significant increase (p < 0.001) in the serum neopterin levels of the patients was observed. No significant relationship was determined between neopterin levels and age/sex (both, p > 0.05). With overstimulation of interferon-gamma, the production of neopterin increases by monocytes/macrophages. Likewise with other diseases associated with an activated cellular immune system, this study shows that neopterin can be a predictive biomarker for persistent carriers of hepatitis B infection.

Veritable antiviral capacity of natural killer cells in chronic HBV infection: an argument for an earlier anti-virus treatment

Background

There is limited information on innate immunity, especially natural killer (NK) cell function, in different chronic hepatitis B (CHB) stages. Therefore, we examined whether the clinical staging strategy accurately reflects veritable NK cell immunity.

Methods

A total of 237 eligible CHB patients and 22 healthy controls were enrolled in our study. Demographic and clinical data were collected, and the CHB phases (immune active-IA, immune tolerant phase-IT, inactive CHB-IC, and grey zone-GZ) were classified according to the latest American Association for the Study of Liver Disease guidelines. Peripheral blood mononuclear cells from patients and healthy controls were tested for NK cell frequency, phenotype and function using flow cytometry.

Results

A significant decrease in activating receptor NKp44 and NKp46 expression and significant increase of exhaustion molecule Tim-3 expression were observed in NK cells from CHB patients. Reduced cytokine secretion and preserved or elevated cytotoxic function were also observed. Patients in the IT group exhibited comparable cytokine secretion and cytolytic capacity as age-matched IA patients. NK cell anti-viral functions were preserved in GZ patients. Some of the NK cell function in patients who were excluded from treatment by the current treatment guidelines was less compromised than patients who qualified for treatment.

Conclusion

Our findings provide evidence of veritable NK cell immunity during different natural history phases in treatment-naïve patients with chronic HBV Infection. Chronic HBV infection hindered NK cell function in CHB patients. However, the presumed IT and GZ statuses of CHB patients based on the clinical parameters may not accurately reflect the inner immune status of these patients and should be reconsidered. Some patients excluded from treatment by the current treatment guidelines may be able to be selected as candidates for treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1318-1) contains supplementary material, which is available to authorized users.

Cytomegalovirus-Driven Adaptive-Like Natural Killer Cell Expansions Are Unaffected by Concurrent Chronic Hepatitis Virus Infections

Adaptive-like expansions of natural killer (NK) cell subsets are known to occur in response to human cytomegalovirus (CMV) infection. These expansions are typically made up of NKG2C⁺ NK cells with particular killer-cell immunoglobulin-like receptor (KIR) expression patterns. Such NK cell expansion patterns are also seen in patients with viral hepatitis infection. Yet, it is not known if the viral hepatitis infection promotes the appearance of such expansions or if effects are solely attributed to underlying CMV infection. In sizeable cohorts of CMV seropositive hepatitis B virus (HBV), hepatitis C virus (HCV), and hepatitis delta virus (HDV) infected patients, we analyzed NK cells for expression of NKG2A, NKG2C, CD57, and inhibitory KIRs to assess the appearance of NK cell expansions characteristic of what has been seen in CMV seropositive healthy individuals. Adaptive-like NK cell expansions observed in viral hepatitis patients were strongly associated with CMV seropositivity. The number of subjects with these expansions did not differ between CMV seropositive viral hepatitis patients and corresponding healthy controls. Hence, we conclude that adaptive-like NK cell expansions observed in HBV, HCV, and/or HDV infected individuals are not caused by the chronic hepatitis infections per se, but rather are a consequence of underlying CMV infection.