Imbalance between circulating CD4+ regulatory T and conventional T lymphocytes in patients with HBV-related acute-on-chronic liver failure

Single-Cell Transcriptome Identifies a Proinflammatory B-Cell Subset in Hepatitis B Virus Associated Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is a severe clinical condition with high short-term mortality, in part due to the dysfunctional immune response. Identifying immune mechanism under ACLF is critical to understand its pathogenesis and to develop novel targeted therapeutics. Among the immune cells, how are B cells involved in ACLF remains largely unknown. We performed scRNA-seq on peripheral blood mononuclear cells from clinical ACLF patients and healthy controls. Integrated analysis was performed to identify the role of B cells in ACLF. Subsequently, different subsets of B cells in ACLF were validated through flow cytometry based on their highlighted markers. Six B-cell subgroups, including naive B cells, naive B2 cells, nonclass-switched memory B cells, class-switched memory B cells, autoimmune-related B cells and plasma B cells were identified. The proportions of naive B cells significantly expand in ACLF, compared with healthy control. Function enrichment analysis revealed the activation of inflammatory response in naive B cells. Further flow cytometry confirmed the elevated circulating naive B cells in ACLF. Our study uncovered the altered immune landscape of circulating B cells after ACLF. The proportion dynamics and functional perturbation indicate the potential of naive B cells as intervention targets in the future ACLF therapy.

Metabolic Dysregulation and Metabolite Imbalances in Acute-on-chronic Liver Failure: Impact on Immune Status

Liver failure encompasses a range of severe clinical syndromes resulting from the deterioration of liver function, triggered by factors both within and outside the liver. While the definition of acute-on-chronic liver failure (ACLF) may vary by region, it is universally recognized for its association with multiorgan failure, a robust inflammatory response, and high short-term mortality rates. Recent advances in metabolomics have provided insights into energy metabolism and metabolite alterations specific to ACLF. Additionally, immunometabolism is increasingly acknowledged as a pivotal mechanism in regulating immune cell functions. Therefore, understanding the energy metabolism pathways involved in ACLF and investigating how metabolite imbalances affect immune cell functionality are crucial for developing effective treatment strategies for ACLF. This review methodically examined the immune and metabolic states of ACLF patients and elucidated how alterations in metabolites impact immune functions, offering novel perspectives for immune regulation and therapeutic management of liver failure.

Single-Cell RNA Sequencing Shows T-Cell Exhaustion Landscape in the Peripheral Blood of Patients with Hepatitis B Virus-Associated Acute-on-Chronic Liver Failure

Background/Aims

The occurrence and development of hepatitis B virus-associated acute-on-chronic liver failure (HBV-ACLF) is closely related to the immune pathway. We explored the heterogeneity of peripheral blood T cell subsets and the characteristics of exhausted T lymphocytes, in an attempt to identify potential therapeutic target molecules for immune dysfunction in ACLF patients.

Methods

A total of 83,577 T cells from HBV-ACLF patients and healthy controls were screened for heterogeneity by single-cell RNA sequencing. In addition, exhausted T-lymphocyte subsets were screened to analyze their gene expression profiles, and their developmental trajectories were investigated. Subsequently, the expression of exhausted T cells and their capacity in secreting cytokines (interleukin 2, interferon γ, and tumor necrosis factor α) were validated by flow cytometry.

Results

A total of eight stable clusters were identified, among which CD4+ TIGIT+ subset and CD8+ LAG-3+ subset, with high expression of exhaust genes, were significantly higher in the HBV-ACLF patients than in normal controls. As shown by pseudotime analysis, T cells experienced a transition from naïve T cells to effector T cells and then exhausted T cells. Flow cytometry confirmed that the CD4+TIGIT+ subset and CD8+LAG-3+ subset in the peripheral blood of the ACLF patients were significantly higher than those in the healthy controls. Moreover, in vitro cultured CD8+LAG-3+ T cells were significantly fewer capable of secreting cytokines than CD8+LAG-3- subset.

Conclusions

Peripheral blood T cells are heterogeneous in HBV-ACLF. The exhausted T cells markedly increase during the pathogenesis of ACLF, suggesting that T-cell exhaustion is involved in the immune dysfunction of HBV-ACLF patients.

CHINAT-CD4 Score Predicts Transplant-Free Survival in Patients with Acute-on-Chronic Liver Failure

Aim

The early prognosis evaluation of acute-on-chronic liver failure (ACLF) is important to decrease its mortality. We aimed to develop a new score to accurately predict the outcome of patients with ACLF.

Methods

A derivation set of 408 patients with hepatitis B virus-related ACLF (HBV-ACLF) based on the Asian Pacific Association for the Study of the Liver criteria is used to develop a prognostic score that was validated in 209 patients with HBV-ACLF and 195 patients with non-HBV-ACLF.

Results

Seven factors were significantly related to the 28-day mortality and constituted a new score (CHINAT-CD4 = 0.320 × ln (creatinine) + 0.668 × hepatic encephalopathy score + 0.745 × ln (international normalized ratio) + 0.476 × ln (neutrophil) + 0.251 × ln (aspartate aminotransferase) + 0.411 × ln (total bilirubin) - 0.605 × ln (CD4+ T cells count)). The C-indices of the new score for the 28-/90-day mortality (0.810/0.806) outperformed those of the other seven scores (p≤0.05). The results were confirmed in a validation set (0.798/793 for HBV-ACLF; 0.790/0.788 for non-HBV-ACLF). The novel score based on CD4⁺ T cell count showed high predictive performance for the 28-/90-day mortality of ACLF.

Conclusion

The novel score based on CD4⁺ T cell count can accurately predict the 28-/90-day mortality for patients with ACLF.

Characterization of intrahepatic B cells in acute-on-chronic liver failure

Background and objectives

Acute on chronic liver failure (ACLF) is characterized by the immunologic dissonance during the prolonged pathogenic development. Both abnormal innate immune response and adaptive T-cell response have been reported in patients with ACLF; however, less is known regarding B cells in ACLF pathogenesis. Previous reports were only based on immunophenotyping of peripheral blood samples. Here, we aim to dissect liver-infiltrating B-cell subpopulation in ACLF.

Methods

Paired liver perfusate and peripheral blood were freshly collected from healthy living donors and recipients during liver transplantation. Liver tissues were obtained from patients with ACLF, cirrhosis, and healthy controls. Flow cytometry was used to characterize the phenotypic and functional alterations in intrahepatic and circulating B-cell populations from ACLF, cirrhosis, and healthy controls. The expression of CD19⁺ and CD138⁺ on liver tissues was examined by immunohistochemistry staining.

Results

In this study, we first deciphered the intrahepatic B cells subsets of patients with ACLF. We found that the ACLF liver harbored reduced fraction of naïve B cells and elevated percentage of CD27⁺CD21^- activated memory B cells (AM), CD27^-CD21^- atypical memory B cells (atMBC), CD27⁺IgD^-IgM⁺(IgM⁺ memory B cells), and CD27⁺CD38⁺⁺ plasma cells than cirrhosis and healthy controls. Moreover, these B subpopulations demonstrated enhanced activation and altered effector functions. Specifically, the ACLF liver was abundant in atMBC expressing higher CD11c and lower CD80 molecule, which was significantly correlated to alanine aminotransferase and aspartate aminotransferase. In addition, we found that intrahepatic CD27⁺CD38⁺⁺plasma cells were preferentially accumulated in ACLF, which expressed more CD273 (PD-L2) and secreted higher granzyme B and IL-10. Finally, the enriched hepatic plasma B cells were in positive association with disease severity indices including alkaline phosphatase and gamma-glutamyl transferase.

Conclusions

In this pilot study, we showed an intrahepatic B-cell landscape shaped by the ACLF liver environment, which was distinct from paired circulating B-cell subsets. The phenotypic and functional perturbation in atMBC and plasma cells highlighted the unique properties of infiltrating B cells during ACLF progression, thereby denoting the potential of B-cell intervention in ACLF therapy.

The Mechanisms of Systemic Inflammatory and Immunosuppressive Acute-on-Chronic Liver Failure and Application Prospect of Single-Cell Sequencing

Acute-on-chronic liver failure (ACLF) is a complex clinical syndrome, and patients often have high short-term mortality. It occurs with intense systemic inflammation, often accompanied by a proinflammatory event (such as infection or alcoholic hepatitis), and is closely related to single or multiple organ failure. Liver inflammation begins when innate immune cells (such as Kupffer cells (KCs)) are activated by binding of pathogen-associated molecular patterns (PAMPs) from pathogenic microorganisms or damage-associated molecular patterns (DAMPs) of host origin to their pattern recognition receptors (PRRs). Activated KCs can secrete inflammatory factors as well as chemokines and recruit bone marrow-derived cells such as neutrophils and monocytes to the liver to enhance the inflammatory process. Bacterial translocation may contribute to ACLF when there are no obvious precipitating events. Immunometabolism plays an important role in the process (including mitochondrial dysfunction, amino acid metabolism, and lipid metabolism). The late stage of ACLF is mainly characterized by immunosuppression. In this process, the dysfunction of monocyte and macrophage is reflected in the downregulation of HLA-DR and upregulation of MER tyrosine kinase (MERTK), which weakens the antigen presentation function and reduces the secretion of inflammatory cytokines. We also describe the specific function of bacterial translocation and the gut-liver axis in the process of ACLF. Finally, we also describe the transcriptomics in HBV-ACLF and the recent progress of single-cell RNA sequencing as well as its potential application in the study of ACLF in the future, in order to gain a deeper understanding of ACLF in terms of single-cell gene expression.

Identification of effective diagnostic biomarker and immune cell infiltration characteristics in acute liver failure by integrating bioinformatics analysis and machine-learning strategies

Background: To determine effective biomarkers for the diagnosis of acute liver failure (ALF) and explore the characteristics of the immune cell infiltration of ALF.

Methods: We analyzed the differentially expressed genes (DEGs) between ALF and control samples in GSE38941, GSE62029, GSE96851, GSE120652, and merged datasets. Co-expressed DEGs (co-DEGs) identified from the five datasets were analyzed for enrichment analysis. We further constructed a PPI network of co-DEGs using the STRING database. Then, we integrated the two kinds of machine-learning strategies to identify diagnostic biomarkers of top hub genes screened based on MCC and Degree methods. And the potential diagnostic performance of the biomarkers for ALF was estimated using the AUC values. Data from GSE14668, GSE74000, and GSE96851 databases was performed as external verification sets to validate the expression level of potential diagnostic biomarkers. Furthermore, we analyzed the difference in the protein level of diagnostic biomarkers between normal and ALF mice models. Finally, we used CIBERSORT to estimate relative infiltration levels of 22 immune cell subsets in ALF samples and further analyzed the relationships between the diagnostic biomarkers and infiltrated immune cells.

Results: A total of 200 co-DEGs were screened. Enrichment analyses depicted that they are highly enriched in metabolism and matrix collagen production-associated processes. The top 28 hub genes were obtained by integrating MCC and Degree methods. Then, the collagen type IV alpha 2 chain (COL4A2) was regarded as the diagnostic biomarker and showed excellent specificity and sensitivity. COL4A2 also showed a statistically significant difference and excellent diagnostic effectiveness in the verification set. In addition, there was a significant upregulation in the COL4A2 protein level in ALF mice models compared with the normal group. CIBERSORT analysis showed that activated CD4 T cells, plasma cells, macrophages, and monocytes may be implicated in the progress of ALF. In addition, COL4A2 showed different degrees of correlation with immune cells.

Conclusion: In conclusion, COL4A2 may be a diagnostic biomarker for ALF, and immune cell infiltration may have important implications for the occurrence and progression of ALF.

The Immune Pathogenesis of Acute-On-Chronic Liver Failure and the Danger Hypothesis

Acute-on-chronic liver failure (ACLF) is a group of clinical syndromes related to severe acute liver function impairment and multiple-organ failure caused by various acute triggering factors on the basis of chronic liver disease. Due to its severe condition, rapid progression, and high mortality, it has received increasing attention. Recent studies have shown that the pathogenesis of ACLF mainly includes direct injury and immune injury. In immune injury, cytotoxic T lymphocytes (CTLs), dendritic cells (DCs), and CD4⁺ T cells accumulate in the liver tissue, secrete a variety of proinflammatory cytokines and chemokines, and recruit more immune cells to the liver, resulting in immune damage to the liver tissue, massive hepatocyte necrosis, and liver failure, but the key molecules and signaling pathways remain unclear. The “danger hypothesis” holds that in addition to the need for antigens, damage-associated molecular patterns (DAMPs) also play a very important role in the occurrence of the immune response, and this hypothesis is related to the pathogenesis of ACLF. Here, the research status and development trend of ACLF, as well as the mechanism of action and research progress on various DAMPs in ACLF, are summarized to identify biomarkers that can predict the occurrence and development of diseases or the prognosis of patients at an early stage.

Glucocorticoid Treatment Strategies in Liver Failure

Liver failure is characterized by serious liver decompensation and high mortality. The activation of systemic immune responses and systemic inflammation are widely accepted as the core pathogenesis of liver failure. Glucocorticoids (GCs) are most regularly utilized to suppress excessive inflammatory reactions and immunological responses. GCs have been used in the clinical treatment of liver failure for nearly 60 years. While there has been no unanimity on the feasibility and application of GC treatment in liver failure until recently. The most recent trials have produced conflicting results when it comes to the dose and time for GC therapy of different etiology of liver failure. Our review outlines the issues and options in managing GC treatment in liver failure based on an investigation of the molecular mechanism that GC may give in the treatment.

CD200R Combined Neutrophil-Lymphocyte Ratio Predict 90-Day Mortality in HBV-Related Acute-On-Chronic Liver Failure

Background: Survival of acute-on-chronic liver failure (ACLF) cannot be properly predicted based on clinical characteristics.

Aims: This study aimed to develop a predictive model to evaluating the prognosis for hepatitis B virus-related ACLF (HBV-ACLF) based on specific laboratory and immune indicators.

Methods: Baseline laboratory results were obtained and immune indicators were detected by flow cytometry. A predictive model, which estimates the prognosis at 90-day follow-up, was developed using data from a prospective study on 45 patients hospitalized of HBV-ACLF from June 2016 to April 2018 at the Beijing Ditan Hospital, Capital Medical University. The prognostic values of the predictive factors were determined by the area under the receiver operating characteristic (AUROC) curves.

Results: Six factors exhibited statistical differences between the survival and non-survival groups: proportions of CD4⁺T_N, CD4⁺T_EM, CD8⁺T_N, CD8⁺T_EM, CD200R⁺CD4⁺T cells and neutrophil-lymphocyte ratio (NLR). CD200R combined with the NLR had an AUROC of 0.916, which was significantly higher than the AUROC values of CD200R⁺CD4⁺T cells (0.868), NLR (0.761), model for end-stage liver disease (MELD) (0.840), MELD-Na (0.870), Child-Turcotte-Pugh (CTP) (0.580), or chronic liver failure-consortium ACLF (CLIF-C ACLF) score(0.840). At the cut-off point of−3.87, matching the maximum Youden index determined by ROC analysis, the positive predictive and negative predictive values for the mortality were 0.86 and 0.97, respectively.

Conclusions: The 90-day prediction model based on baseline levels of CD200R⁺CD4⁺T cells and NLR offers potential predictive value for the mortality of HBV-ACLF.

Treg/Th17 Cell Balance in Patients with Hepatitis B Virus-Related Acute-on-Chronic Liver Failure at Different Disease Stages

Background

T-helper 17 (Th17) and CD4⁺CD25⁺ T-regulatory (Treg) cells play important roles in the pathogenesis of hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF). This study is aimed at investigating shifts in Treg/Th17 balance in the peripheral blood of HBV-ACLF patients at different disease stages.

Methods

Sixty HBV-ACLF patients, admitted to the First Hospital of Hunan University of Chinese Medicine, China, including early-stage (n = 20), middle-stage (n = 20), and late-stage patients (n = 20), were enrolled in the study. In addition, 20 patients with chronic hepatitis B and 20 healthy volunteers were also included in the study as controls. Flow cytometry, cytometric bead array, and quantitative real-time PCR protocols were used to evaluate the expression of Treg and Th17 cells as well as of related cytokines.

Results

The levels of Th17 cells and their effectors interleukin- (IL-) 17A, IL-23, and tumor necrosis factor-α increased with disease progression. Similarly, Treg cells and their effector cytokines transforming growth factor-β and IL-10 also increased. Although Treg and Th17 levels were positively correlated, the latter were always at higher numbers. Noteworthy, the Treg/Th17 ratio gradually decreased and was negatively correlated with ACLF severity. FoxP3 levels in the peripheral blood gradually decreased with ACLF progression, whereas ROR-γt gradually increased. Serum c-reactive protein, procalcitonin, and lipopolysaccharide were also upregulated with disease progression and positively correlated with Th17 abundance. Further, Th17, IL-17A, and IL-23 were independent risk factors for ACLF. A prognostic model for HBV-ACLF was established, with a correct prediction rate of 90.00% (54/60).

Conclusion

Treg/Th17 imbalance occurs throughout the pathogenic course of HBV-ACLF, with an imbalance shift toward Th17. Hence, the Th17-mediated inflammatory response drives HBV-ACLF-associated inflammation and supports the pathological mechanisms of liver failure.

Characteristics of Peripheral Lymphocyte Subsets in Patients With Acute-On-Chronic Liver Failure Associated With Hepatitis B

Background and Aims: Acute-on-chronic liver failure (ACLF) is a rare, but dramatic clinical syndrome. There is substantial evidence suggesting that immunity-mediated inflammation plays an important role in HBV-ACLF. Our aim was to characterize the proportion and cell counts of peripheral blood lymphocyte subsets in acute-on-chronic liver failure patients caused by HBV infection.

Methods: One hundred and seventeen patients were enrolled in this study, including those with HBV-related ACLF (HBV-ACLF; n = 70), and HBV related non-ACLF patients (HBV non-ACLF; n = 47). Demographics, clinical and laboratory data at hospital admission were retrospectively analyzed. The percentage and cell count of peripheral lymphocyte subsets were evaluated by flow cytometry. Comparison analysis was performed by t-test or non-parametric Mann–Whitney U-test. Actuarial probabilities of death were calculated by the Kaplan-Meier method.

Results: Both circulating lymphocyte count and lymphocyte percentage were significantly reduced in patients with HBV-ACLF (P < 0.001). The CD8⁺ T cell, CD4⁺ T cell, and CD16⁺CD56⁺ NK cell counts were significantly decreased in HBV-ACLF. Consistently, flow cytometric analysis showed that CD8⁺ T cell counts were significantly decreased in non-survivors, while no significant differences were found in CD4⁺ T cell, CD19⁺ B cell, or CD56⁺CD16⁺ NK cell counts. Furthermore, the group with the lower CD8⁺ T cell count displayed a significantly higher mortality rate compared with the group with the higher CD8⁺ T cell count.

Conclusions: The abnormal prevalence of lymphocyte subsets may be important in the pathogenesis of HBV-ACLF. The decrease in CD8⁺ T cell counts may be related to poor survival in HBV-ACLF patients.

PD-1 Involvement in Peripheral Blood CD8+ T Lymphocyte Dysfunction in Patients with Acute-on-chronic Liver Failure

BACKGROUND AND AIMS

Programmed cell death-1 (PD-1) plays an important role in downregulating T lymphocytes but the mechanisms are still poorly understood. This study aimed to explore the role of PD-1 in CD8⁺ T lymphocyte dysfunction in hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF).

METHODS

Thirty patients with HBV-ACLF and 30 healthy controls (HCs) were recruited. The differences in the numbers and functions of CD8⁺ T lymphocytes, PD-1 and glucose transporter-1 (Glut1) expression from the peripheral blood of patients with HBV-ACLF and HCs were analyzed. In vitro, the CD8⁺ T lymphocytes from HCs were cultured (HC group) and the CD8⁺ T lymphocytes from ACLF patients were cultured with PD-L1-IgG (ACLF+PD-1 group) or IgG (ACLF group). The numbers and functions of CD8⁺ T lymphocytes, PD-1 expression, glycogen uptake capacity, and Glut1, hexokinase-2 (HK2), and pyruvate kinase (PKM2) expression were analyzed among the HC group, ACLF group and ACLF+ PD-1group.

RESULTS

The absolute numbers of CD8⁺ T lymphocytes in the peripheral blood from patients with HBV-ACLF were lower than in the HCs (p<0.001). The expression of PD-1 in peripheral blood CD8⁺ T lymphocytes was lower in HCs than in patients with HBV-ACLF (p=0.021). Compared with HCs, PD-1 expression was increased (p=0.021) and Glut1 expression was decreased (p=0.016) in CD8⁺ T lymphocytes from the HBV-ACLF group. In vitro, glycogen uptake and functions of ACLF CD8⁺ T lymphocytes were significantly lower than that in HCs (p=0.017; all p<0.001). When PD-1/PD-L1 was activated, the glycogen uptake rate and expression levels of Glut1, HK2, and PKM2 showed a decreasing trend (ACLF+PD-1 group compared to ACLF group , all p<0.05). The functions of CD8⁺ T lymphocytes in the ACLF+PD-1 group [using biomarkers of Ki67, CD69, IL-2, interferon-gamma, and tumor necrosis factor-alpha- were lower than in the ACLF group (all p<0.05).

CONCLUSIONS

CD8⁺ T lymphocyte dysfunction is observed in patients with HBV-ACLF. PD-1-induced T lymphocyte dysfunction might involve glycolysis inhibition.

Peripheral T lymphocytes predict the severity and prognosis in patients with HBV-related acute-on-chronic liver failure

BACKGROUND

Hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF) is a life-threatening syndrome with high mortality. Biomarkers are urgently needed to predict the prognosis of HBV-ACLF. Recent evidence suggests a key role for immune system in the pathology of HBV-ACLF. Here, we analyzed the correlation between peripheral blood T lymphocytes and the severity and prognosis in HBV-ACLF patients.

METHOD

Sixty-six patients with HBV-ACLF received conventional medical treatments for 4 weeks. Twenty-five healthy subjects and 20 HBV patients were enrolled for comparison. We determined white blood cell count, lymphocytes, CD3+, CD4+ and CD8+ T cells, and CD4+CD25+ Treg cells in the blood of all subjects. Their associations with laboratory parameters before or after treatments were statistically analyzed.

RESULT

The results showed that compare normal subjects and chronic hepatitis B patients, HBV-ACLF patients had significantly increased white blood count, CD4+ T cells and decreased lymphocytes, CD3+ T cells, and Treg cells. Correlation analysis showed that white blood cell, lymphocytes, and peripheral T lymphocytes were correlated with prothrombin activity (PTA) and model for end-stage liver disease (MELD) scores. After treatment, white blood cell, lymphocytes, and peripheral T lymphocytes were also correlated with PTA and MELD scores. Additionally, total bilirubin (TBIL), alanine aminotransferase (ALT), international standard ratio (INR), MELD, and white blood cell count were potential prognostic criteria for HBV-ACLF patients.

CONCLUSION

HBV-ACLF patients had depletion and dysfunction of immune system. Changes of peripheral T lymphocytes were closely related to the pathogenesis and prognosis of disease. Our results may contribute to predict the severity of HBV-ACLF, and provide a prognosis response to improve the treatment of HBV-ACLF.

Dynamic changes of T cell receptor repertoires in patients with hepatitis B virus-related acute-on-chronic liver failure

BACKGROUND AND AIMS

T cell-mediated immune injury plays a critical role in the pathogenesis of hepatitis B virus-related acute-on-chronic liver failure (HBV-ACLF). Given the high short-term mortality and crucial role of T cells in the disease progression, it is necessary to investigate the dynamics of T cell clones during HBV-ACLF. The aim of this study was to longitudinally investigate dynamic changes in the composition and perturbation of T cell receptor β (TCRβ) chain repertoires and to determine whether TCR repertoire characteristics were associated with HBV-ACLF patient outcomes.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected at two time points from 5 HBV-ACLF patients. Global CD4⁺ and CD8⁺ T cells were sorted using magnetic beads. TCRβ complementarity-determining region 3 was analyzed by unbiased high-throughput sequencing.

RESULTS

During HBV-ACLF, there was a significant decrease in the diversity of T cell repertoires and an increase in proportion of the most 100 abundant clonotypes of CD8 T cells but not CD4. Decreased CD8 repertoire diversity was positively correlated with the reduction of the Model for End-Stage Liver Disease (MELD) score.

CONCLUSIONS

There was significant clonal expansion in CD8 but not in CD4 T cell repertoires in HBV-ACLF patients during disease progression. Patients with greater clonal expansions in CD8 T cell repertoires may have better outcomes. CD8 TCRβ repertoire diversity may serve as a potential predictive marker for disease outcome.

The immunological roles in acute-on-chronic liver failure: An update

BACKGROUND

Acute-on-chronic liver failure (ACLF) refers to the acute deterioration of liver function that occurs in patients with chronic liver disease. ACLF is characterized by acute decompensation, organ failure and high short-term mortality. Numerous studies have been conducted and remarkable progress has been made regarding the pathophysiology and pathogenesis of this disease in the last decade. The present review was to summarize the advances in this field.

DATA SOURCES

A comprehensive search in PubMed and EMBASE was conducted using the medical subject words "acute-on-chronic liver failure", "ACLF", "pathogenesis", "predictors", and "immunotherapy" combined with free text terms such as "systemic inflammation" and "immune paralysis". Relevant papers published before October 31, 2018, were included.

RESULTS

ACLF has two marked pathophysiological features, namely, excessive systemic inflammation and susceptibility to infection. The systemic inflammation is mainly manifested by a significant increase in the levels of plasma pro-inflammatory factors, leukocyte count and C-reactive protein. The underlying mechanisms are unclear and may be associated with decreased immune inhibitory cells, abnormal expression of cell surface molecules and intracellular regulatory pathways in immune cells and increased damage-associated molecular patterns in circulation. However, the main cause of susceptibility to infection is immune paralysis. Immunological paralysis is characterized by an attenuated activity of immune cells. The mechanisms are related to elevations of immune inhibitory cells and the concentration of plasma anti-inflammatory molecules. Some immune biological indicators, such as soluble CD163, are used to explore the pathogenesis and prognosis of the disease, and some immunotherapies, such as glucocorticoids and granulocyte colony-stimulating factor, are effective on ACLF.

CONCLUSIONS

Overwhelming systemic inflammation and susceptibility to infection are two key features of ACLF. A better understanding of the state of a patient's immune system will help to guide immunotherapy for ACLF.

Aberrant GSTP1 promoter methylation predicts poor prognosis of acute-on-chronic hepatitis B pre-liver failure

It has been demonstrated that glutathione-S-transferase P1 (GSTP1) could protect cells from DNA damage mediated by oxidizing agents or electrophiles in hepatic inflammatory response. Our study evaluated the methylation status and the predictive value for prognosis of GSTP1 promoter region in patients with acute-on-chronic hepatitis B pre-liver failure (pre-ACHBLF). Methylation status of GSTP1 promoter in peripheral blood mononuclear cells (PBMCs) and plasma was measured in 103 patients with pre-ACHBLF, 80 patients with chronic hepatitis B (CHB) and 30 healthy controls (HCs) by methylation-specific polymerase chain reaction. The mRNA level of GSTP1 was detected by quantitative real-time polymerase chain reaction. The methylation frequency of GSTP1 promoter region in patients with pre-ACHBLF (35/103 in PBMCs and 33/103 in plasma) was significantly higher than CHB (2/80) and HCs (0/30), respectively. The mRNA level of GSTP1 in patients with pre-ACHBLF was significantly lower than CHB and HCs. Additionally, pre-ACHBLF patients with methylated GSTP1 presented strikingly higher incidence of ACHBLF than those without. Of note, GSTP1 methylation presented distinctly better performance than model for end-stage liver disease score [area under the receiver operating characteristic curves (AUCs) 0.825 in PBMCs and 0.798 in plasma VS 0.589; AUC 0.804 in PBMCs and 0.779 in plasma VS 0.622; AUC 0.767 in PBMCs and 0.744 in plasma VS 0.602, respectively] when used to predict the 1-, 2- or 3-month incidence of ACHBLF in patients with pre-ACHBLF. Aberrant methylation of GSTP1 has potential to be a prognostic biomarker for pre-ACHBLF.

Changes in cellular proliferation and plasma products are associated with liver failure

AIM

To study the differences in immune response and cytokine profile between acute liver failure and self-limited acute hepatitis.

METHODS

Forty-six patients with self-limited acute hepatitis (AH), sixteen patients with acute liver failure (ALF), and twenty-two healthy subjects were involved in this study. The inflammatory and anti-inflammatory products in plasma samples were quantified using commercial enzyme-linked immunoassays and quantitative real-time PCR. The cellular immune responses were measured by proliferation assay using flow cytometry. The groups were divided into viral- and non-viral-induced self-limited AH and ALF. Thus, we worked with five groups: Hepatitis A virus (HAV)-induced self-limited acute hepatitis (HAV-AH), HAV-induced ALF (HAV-ALF), non-viral-induced self-limited acute hepatitis (non-viral AH), non-viral-induced acute liver failure (non-viral ALF), and healthy subjects (HC). Comparisons among HAV and non-viral-induced AH and ALF were performed.

RESULTS

The levels of mitochondrial DNA (mtDNA) and the cytokines investigated [interleukin (IL)-6, IL-8, IL-10, interferon gamma, and tumor necrosis factor] were significantly increased in ALF patients, independently of etiology (P < 0.05). High plasma mtDNA and IL-10 were the best markers associated with ALF [mtDNA: OR = 320.5 (95%CI: 14.42-7123.33), P < 0.0001; and IL-10: OR = 18.8 (95%CI: 1.38-257.94), P = 0.028] and death [mtDNA: OR = 12.1 (95%CI: 2.57-57.07), P = 0.002; and IL-10: OR = 8.01 (95%CI: 1.26-50.97), P = 0.027]. In the cellular proliferation assay, NK^bright, NKT and regulatory T cells (TReg) predominated in virus-specific stimulation in HAV-induced ALF patients with an anergic behavior in the cellular response to mitotic stimulation. Therefore, in non-viral-induced ALF, anergic behavior of activated T cells was not observed after mitotic stimulation, as expected and as described by the literature.

CONCLUSION

mtDNA and IL-10 may be predictors of ALF and death. TReg cells are involved in immunological disturbance in HAV-induced ALF.

Regulatory T-cells promote hepatitis B virus infection and hepatocellular carcinoma progression

Regulatory T-cells (Tregs), known for their immune suppressive function, have been reported in higher numbers, with activated phenotypes and greater potency, in hepatitis B virus (HBV)-related liver diseases than in normal conditions. The numbers, phenotypes, and function of intrahepatic and/or tumor-infiltrating Tregs in HBV-related liver diseases also differ from those of Tregs in the peripheral blood. By inhibiting the function of effector T-cells (Teffs), Tregs play a substantial role in the formation and maintenance of the liver's suppressive microenvironment, which might account for the progression of HBV-related hepatitis and hepatocellular carcinoma (HCC). In acute hepatitis B virus infection, Tregs can safeguard the liver from damage at the cost of prolonged antiviral processes, which results in chronic HBV infection in the liver. Furthermore, Tregs play a role in the development of cirrhosis, the transformation of cirrhosis to HCC, and the progression and metastasis of HCC. Higher levels of Tregs in the peripheral blood and/or tumor sites signify a poorer prognosis in HBV-related liver conditions, and observational data from mouse models and human patients support the theory that depleting Tregs may be therapeutic in HBV-related liver diseases by inducing antiviral and antitumor immunity.

Clinical Potential of Regulatory T Cell Therapy in Liver Diseases: An Overview and Current Perspectives

The increasing demand for liver transplantation and the decline in donor organs has highlighted the need for alternative novel therapies to prevent chronic active hepatitis, which eventually leads to liver cirrhosis and liver cancer. Liver histology of chronic hepatitis is composed of both effector and regulatory lymphocytes. The human liver contains different subsets of effector lymphocytes that are kept in check by a subpopulation of T cells known as Regulatory T cells (Treg). The balance of effector and regulatory lymphocytes generally determines the outcome of hepatic inflammation: resolution, fulminant hepatitis, or chronic active hepatitis. Thus, maintaining and adjusting this balance is crucial in immunological manipulation of liver diseases. One of the options to restore this balance is to enrich Treg in the liver disease patients. Advances in the knowledge of Treg biology and development of clinical grade isolation reagents, cell sorting equipment, and good manufacturing practice facilities have paved the way to apply Treg cells as a potential therapy to restore peripheral self-tolerance in autoimmune liver diseases (AILD), chronic rejection, and posttransplantation. Past and on-going studies have applied Treg in type-1 diabetes mellitus, systemic lupus erythematosus, graft versus host diseases, and solid organ transplantations. There have not been any new therapies for the AILD for more than three decades; thus, the clinical potential for the application of autologous Treg cell therapy to treat autoimmune liver disease is an attractive and novel option. However, it is fundamental to understand the deep immunology, genetic profiles, biology, homing behavior, and microenvironment of Treg before applying the cells to the patients.

Cytokines elevated in patients with HBV-related acute-on-chronic liver failure promote NK cell mediated cytotoxicity through TRAIL

BACKGROUND AND AIMS

The role of NK cells on inducing liver injury in patients with HBV-related acute-on-chronic liver failure (HBV-ACLF) is not well understood. The aim of this study was to determine the cytotoxicity of tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-expressed NK cells from HBV-ACLF patients and facilitate a better understanding of the immune pathogenesis of HBV-ACLF.

METHODS

Peripheral blood samples were obtained from HBV-ACLF patients, mild chronic hepatitis B (CHB) patients and healthy controls (HC). Circulating NK cells phenotype was determined using flow cytometry. Serum cytokine concentrations were ascertained using the CBA Inflammation kit. Cell apoptosis was analyzed using the FITC-annexin V Apoptosis Detection Kit.

RESULTS

Peripheral NK cells from HBV-ACLF expressed higher levels of TRAIL than those from CHB and HC. Expression of TRAIL on NK cells was correlated positively with serum IL-6 and IL-8 concentrations in HBV-ACLF patients, which is further confirmed by cytokines stimulation in vitro. NK cells caused a significant increase of apoptotic hepatocytes, and further increased the frequency of apoptosis in IL-6 and IL8-stimulated hepatocytes; the apoptosis was then inhibited partially by an anti-TRAIL monoclonal antibody.

CONCLUSION

These results suggested that inflammation cytokines elevated in patients with HBV-ACLF may promote NK cell mediated cytotoxicity through TRAIL pathway.

Characterization of the Treg Response in the Hepatitis B Virus Hydrodynamic Injection Mouse Model

Regulatory T cells (Tregs) play an important role in counter-regulating effector T cell responses in many infectious diseases. However, they can also contribute to the development of T cell dysfunction and pathogen persistence in chronic infections. Tregs have been reported to suppress virus-specific T cell responses in hepatitis B virus (HBV) infection of human patients as well as in HBV animal models. However, the phenotype and expansion of Tregs has so far only been investigated in other infections, but not in HBV. We therefore performed hydrodynamic injections of HBV plasmids into mice and analyzed the Treg response in the spleen and liver. Absolute Treg numbers significantly increased in the liver but not the spleen after HBV injection. The cells were natural Tregs that surprisingly did not show any activation or proliferation in response to the infection. However, they were able to suppress effector T cell responses, as selective depletion of Tregs significantly increased HBV-specific CD8+ T cell responses and accelerated viral antigen clearance. The data implies that natural Tregs infiltrate the liver in HBV infection without further activation or expansion but are still able to interfere with T cell mediated viral clearance.

Acute-on-Chronic Liver Failure

Over the past 2 decades, the concept of acute-on-chronic liver failure (ACLF) has been proposed as an alternate path in the natural history of decompensated cirrhosis. ACLF thus is characterized by the presence of a precipitating event (identified or unidentified) in subjects with underlying chronic liver disease leading to rapid progression of liver injury and ending in multi-organ dysfunction characterized by high short-term mortality. Multiple organ failure and an increased risk for mortality are key to the diagnosis of ACLF. The prevalence of ACLF ranges from 24% to 40% in hospitalized patients. The pathophysiological basis of ACLF can be explained using the following 4-part model: predisposing event, injury caused by a precipitating event, response to injury, and organ failure. Although several mathematic scores have been proposed for identifying outcomes with ACLF, it is as yet unclear whether these organ failure scores are truly prognostic or only reflective of the dying process. Treatment paradigms continue to evolve but consist of early recognition, supportive intensive care, and consideration of liver transplantation before onset of irreversible multiple organ failure.

Significant roles of regulatory T cells and myeloid derived suppressor cells in hepatitis B virus persistent infection and hepatitis B virus-related HCCs

The adaptive immune system, including type1 helper T cells (Th1 cells), cytotoxic T lymphocytes (CTLs), and dendritic cells (DCs), plays an important role in the control of hepatitis B virus (HBV). On the other hand, regulatory T cells (Tregs) and myeloid derived suppressor cells (MDSCs) suppress the immune reaction in HBV and hepatocellular carcinoma (HCC). Excessive activation of immune suppressive cells could contribute to the persistent infection of HBV and the progression of HCC. The frequency and/or function of Tregs could affect the natural course in chronic hepatitis B patients and the treatment response. In addition to the suppressive function of MDSCs, MDSCs could affect the induction and function of Tregs. Therefore, we should understand in detail the mechanism by which Tregs and MDSCs are induced to control HBV persistent infection and HBV-related HCC. Immune suppressive cells, including Tregs and MDSCs, contribute to the difficulty in inducing an effective immune response for HBV persistent infection and HBV-related HCC. In this review, we focus on the Tregs and MDSCs that could be potential targets for immune therapy of chronic hepatitis B and HBV-related HCC.

T helper cell dysregulation with hepatitis B and rebalance with glucocorticoids

AIM: To investigate T helper 17/regulatory T cell alterations in early severe hepatitis B and the effect of glucocorticoids.

METHODS: The study included 20 patients in the early stage of severe hepatitis B (SHB) and 11 healthy controls. All patients had elevated T helper 17 (Th17) levels, decreased regulatory T (Treg) cell levels, and significant Th17/Treg ratios.

RESULTS: After glucocorticoid treatment, 16 patients showed improvement with significant decreases in Th17 levels, increases in Treg, and rebalanced Th17/Treg ratios. The four patients who showed no improvement had increases in both Th17 and Treg levels and an even higher Th17/Treg ratio than before.

CONCLUSION: Glucocorticoid treatment can rectify Th17/Treg dysregulation in patients with SHB.

Innate immune responses in hepatitis B virus (HBV) infection

Hepatitis B virus (HBV) infection has a low rate of chronicity compared to HCV infection, but chronic liver inflammation can evolve to life threatening complications. Experimental data from HBV infected chimpanzees and HBV transgenic mice have indicated that cytotoxic T cells are the main cell type responsible for inhibition of viral replication, but also for hepatocyte lysis during chronic HBV infection. Their lower activation and impaired function in later stages of infection was suggested as a possible mechanism that allowed for low levels of viral replication. The lack of an interferon response in these models also indicated the importance of adaptive immunity in clearing the infection. Increased knowledge of the signalling pathways and pathogen associated molecular patterns that govern activation of innate immunity in the early stages of viral infections in general has led to a re-evaluation of the innate immune system in HBV infection. Numerous studies have shown that HBV employs active strategies to evade innate immune responses and induce immunosuppression. Some of the immune components targeted by HBV include dendritic cells, natural killer cells, T regulatory cells and signalling pathways of the interferon response. This review will present the current understanding of innate immunity in HBV infection and of the challenges associated with clearing of the HBV infection.