Different composition of intrahepatic lymphocytes in the immune-tolerance and immune-clearance phase of chronic hepatitis B

Tissue-specific features of innate lymphoid cells in antiviral defense

Innate lymphocytes (ILCs) rapidly respond to and protect against invading pathogens and cancer. ILCs include natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTi) cells and include type I, type II, and type III immune cells. While NK cells have been well recognized for their role in antiviral immunity, other ILC subtypes are emerging as players in antiviral defense. Each ILC subset has specialized functions that uniquely impact the antiviral immunity and health of the host depending on the tissue microenvironment. This review focuses on the specialized functions of each ILC subtype and their roles in antiviral immune responses across tissues. Several viruses within infection-prone tissues will be highlighted to provide an overview of the extent of the ILC immunity within tissues and emphasize common versus virus-specific responses.

Induction of broad multifunctional CD8+ and CD4+ T cells by hepatitis B virus antigen-based synthetic long peptides ex vivo

Introduction

Therapeutic vaccination based on synthetic long peptides (SLP®) containing both CD4+ and CD8+ T cell epitopes is a promising treatment strategy for chronic hepatitis B infection (cHBV).

Methods

We designed SLPs for three HBV proteins, HBcAg and the non-secreted proteins polymerase and X, and investigated their ability to induce T cell responses ex vivo. A set of 17 SLPs was constructed based on viral protein conservation, functionality, predicted and validated binders for prevalent human leukocyte antigen (HLA) supertypes, validated HLA I epitopes, and chemical producibility.

Results

All 17 SLPs were capable of inducing interferon gamma (IFNɣ) production in samples from four or more donors that had resolved an HBV infection in the past (resolver). Further analysis of the best performing SLPs demonstrated activation of both CD8+ and CD4+ multi-functional T cells in one or more resolver and patient sample(s). When investigating which SLP could activate HBV-specific T cells, the responses could be traced back to different peptides for each patient or resolver.

Discussion

This indicates that a large population of subjects with different HLA types can be covered by selecting a suitable mix of SLPs for therapeutic vaccine design. In conclusion, we designed a set of SLPs capable of inducing multifunctional CD8+ and CD4+ T cells ex vivo that create important components for a novel therapeutic vaccine to cure cHBV.

The Characteristics of Natural Killer Cells and T Cells Vary With the Natural History of Chronic Hepatitis B in Children

Background and Aims: The immune status of children with chronic hepatitis B (CHB) in different phases is still unclear. The aim of this study was to investigate the phenotype and cytokine-producing ability of natural killer (NK) and T cells and to better understand the immune characteristics of children with different phases of CHB. Methods: Treatment-naive children with CHB were divided into groups with different clinical phases of CHB. Fresh peripheral blood drawn from hepatitis B virus (HBV)-infected and healthy children was processed to perform flow cytometric analysis. Results: A total of 112 treatment-naive children with CHB and 16 comparable healthy controls were included in this study. The expression of HLA-DR on NK cells and CD38 on T cells were upregulated, especially in the IA phase, in children with CHB compared with healthy controls. The ability of circulating NK cells instead of CD8+ T cells to produce IFN-γ in children with CHB was slightly increased, but TNF-α production seemed to be decreased compared with that in healthy controls. The expression of some activation markers varied among children with different phases of CHB, especially the higher CD38 expression found on T cells in the IA phase. Regression analysis revealed that IFN-γ and TNF-α production by NK cells and CD8+ T cells seemed to have positive correlations with ALT elevation and an activated status of NK cells or T cells. Conclusion: NK cells and T cells tended to be phenotypically activated (especially in the IA phase) in children with CHB compared with healthy controls. However, their cytokine-producing function was not obviously elevated, especially IFN-γ production by CD8+ T cells. More studies investigating the mechanism and observing the longitudinal changes in the immune status in children with CHB are needed.

Unresolved issues of immune tolerance in chronic hepatitis B

During the natural course of chronic hepatitis B virus infection, immune-tolerant phase is characterized by high viral replication, the presence of HBV e antigen (HBeAg), and normal or minimally elevated serum alanine aminotransferase. Immune-tolerant phase is usually regarded as a benign course of the disease. International guidelines recommend observation rather than treatment during immune-tolerant phase. In this article, we review unresolved issues related to the definition of true immune-tolerant phase and the benefit of antiviral treatment. Defining true immune-tolerant phase requires a careful approach and long-term follow-up. In previous studies, many patients were misclassified as being immune-tolerant phase. Noninvasive methods of assessing fibrosis are warranted for patients in the immune-tolerant phase. Yet, there has been controversy over the benefit and harm of antiviral treatment for immune-tolerant phase patients. Thus, further larger scale studies are needed to investigate the prognosis of patients in true immune-tolerant phase and their need for antiviral therapy.

Hepatitis B virus-specific effector CD8+ T cells are an important determinant of disease prognosis: A meta-analysis

BACKGROUND

Hepatitis B virus (HBV)-specific effector CD8⁺ T cells are critical for viral clearance. To determine the effects of HBV-specific effector CD8⁺ T cells on HBV infection, we performed a meta-analysis of the available literature.

METHODS

Electronic database searches identified appropriately designed studies that detected specific CD8⁺ T cells in HBV-infected patients. Our main endpoints were the course of infection, seroconversion of HBV "e" antigen (HBeAg), the level of HBVDNA, and alanine aminotransferase (ALT) activity. We used a fixed/random model for analysis, according to the results of a heterogeneity test (P value of Q-squared, I²).

RESULTS

Our searches found five eligible articles. Pooled estimation of the reported results showed that levels of specific CD8⁺ T cells were significantly higher in patients with acute hepatitis B than in patients with chronic hepatitis B (odds ratio [OR] = 76.30, 95% confidence interval [CI]: 15.37-378.70). With respect to chronic hepatitis B, patients with <10⁷ copies/ml HBVDNA had higher levels of specific CD8⁺ T cells relative to patients with >10⁷ copies/ml HBVDNA, but the difference had no statistics significance (OR: 3.89, 95% CI: 0.71-21.33). Patients with negative HBeAg or positive anti-HBeAg antibody (anti-HBe) results had significantly higher levels of specific CD8⁺ T cells versus patients with positive HBeAg results (OR: 5.82, 95% CI: 1.41-24.13). There were no significant associations between the levels of specific CD8⁺ T cells and serum ALT activity (OR = 0.86, 95% CI: 0.01-74.15).

CONCLUSION

HBV-specific effector CD8⁺ T cells influence the disease activity in HBV-infected patients in various ways and determine prognosis by eliminating the virus. Therefore, efforts of studying HBV-specific effector CD8⁺ T cells focused vaccine are potentially needed.

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.

A STAT4 variant increases liver fibrosis risk in Caucasian patients with chronic hepatitis B

BACKGROUND

Host genetic modifiers of the natural history of chronic hepatitis B (CHB) remain poorly understood. Recently, a genome-wide association study (GWAS)-identified polymorphism in the STAT4 gene that contributes to the risk for hepatocellular carcinoma (HCC) was shown to be associated with the full spectrum of hepatitis B virus (HBV) outcomes in Asian patients. However, the functional mechanisms for this effect are unknown and the role of the variant in modulating HBV disease in Caucasians has not been investigated.

AIMS

To determine whether STAT4 genetic variation is associated with liver injury in Caucasian patients with CHB and to investigate potential mechanisms mediating this effect.

METHODS

STAT4 rs7574865 was genotyped in 1085 subjects (830 with CHB and 255 healthy controls). STAT4 expression in liver, PBMCs and NK cells, STAT4 phosphorylation and secretion of interferon-gamma (IFN-γ) according to STAT4 genetic variation was examined.

RESULTS

STAT4 rs7574865 genotype was independently associated with hepatic inflammation (OR: 1.42, 95% CI: 1.07-2.06, P = 0.02) and advanced fibrosis (OR: 1.83, 95% CI: 1.19-2.83, P = 0.006). The minor allele frequency of rs7574865 was significantly lower than that in healthy controls. rs7574865 GG risk carriers expressed lower levels of STAT4 in liver, PBMCs and in NK cells, while NK cells from patients with the risk genotype had impaired STAT4 phosphorylation following stimulation with IL-12/IL-18 and a reduction in secretion of IFN-γ.

CONCLUSION

Genetic susceptibility to HBV persistence, hepatic inflammation and fibrosis in Caucasians associates with STAT4 rs7574865 variant. Downstream effects on NK cell function through STAT4 phosphorylation-dependent IFN-γ production likely contribute to these effects.

Hepatitis B virus infection and the immune response: The big questions

Clinical events and the host immune response during hepatitis B virus (HBV) infection are intricately linked. Despite decades of research, important questions concerning the immunopathogenesis of chronic HBV infection remain unanswered. For example, it is unclear which immune parameters facilitate persistence, and if HBV can be completely cleared from the human liver. Recent technological breakthroughs now allow researchers to address these seemingly basic, but essential questions surrounding HBV immunity. It will be important to better define the molecular underpinnings of immune cell function and dysfunction during chronic disease and in controlled infection, with particular focus on the liver, as little information is available on the intrahepatic compartment. In the near future, it may be possible to solve some of the controversy surrounding the immune responses to HBV, and establish the features of both the innate and adaptive arms of the immune system required to achieve sustained control of HBV infection.

Roles of acetylation-dependent regulation in pathogenesis of chronic hepatitis B virus infection: Potential application as targets for antiviral treatment

In recent years, many studies have confirmed that epigenetics and acetylation-dependent regulation play important roles in the pathogenesis of chronic hepatitis and primary hepatocellular carcinoma. This paper systematically introduces the roles and possible mechanisms of acetylation and its related signal pathways in the pathogenesis of chronic hepatitis B virus (HBV) infection, which may provide a potential novel strategy for the therapy of chronic HBV infection.

PD-L1 expression as a predictive biomarker for cytokine-induced killer cell immunotherapy in patients with hepatocellular carcinoma

Cytokine-induced killer (CIK) cell immunotherapy represents an effective treatment strategy for treating hepatocellular carcinoma (HCC). However, the therapeutic benefits of CIK cell treatment can be influenced by differences in complex immune microenvironment between patients. Herein, we investigated the relationship between PD-L1 expression and survival benefits of CIK cell immunotherapy in HCC patients. This retrospective study included 448 HCC patients: 217 cases underwent hepatectomy alone; 231 cases received hepatectomy and post-operative CIK cell transfusion. Immunohistochemistry was used to measure PD-L1 expression in tumor tissue sections from all patients. Meanwhile, flow cytometry was performed to explore the relationship between PD-L1 expression and localized inflammatory response in HCC microenvironment. We found a significantly improved prognosis in CIK treatment group compared with surgery alone group. In the CIK treatment group, higher PD-L1 expression was observed in patients who exhibited long-term survival benefit. Survival analysis showed patients with ≥5% PD-L1 expression had better overall survival (OS) and recurrence-free survival (RFS) than patients with 1-5% or <1% PD-L1 expression, particularly in the subgroup with high hepatitis B viral load. By contrast, PD-L1 expression did not show direct impact on the survival of patients in surgery alone group. Additionally, PD-L1 expression was found to be highly associated with hepatitis B viral load and the proportion of tumor-infiltrating lymphocytes in HCC patients. In conclusions, our study indicates that PD-L1 expression may reflect the presence of endogenous host immune response to tumor and serve as a biomarker for predicting survival benefits from adjuvant CIK cell immunotherapy in HCC patients.

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

BACKGROUND

Natural killer (NK) cells are the main effective component of the innate immune system that responds to chronic hepatitis B (CHB) infection. Although numerous studies have reported the immune profiles of NK cells in CHB patients, they are limited by inconsistent results. Thus, we performed a meta-analysis to characterize reliably the immune profiles of NK cells after CHB infection, specifically frequency, phenotype, and function.

METHODS

A literature search of the computer databases MEDLINE, PUBMED, EMBASE, and Cochrane Center Register of Controlled Trails was performed and 19 studies were selected. The standard mean difference (SMD) and 95% confidence interval (CI) of each continuous variable was estimated with a fixed effects model when I2 < 50% for the test for heterogeneity, or the random effects model otherwise. Publication bias was evaluated using Begg's and Egger's tests.

RESULTS

The meta-analysis of publications that reported frequency of peripheral NK cells showed that NK cell levels in CHB patients were significantly lower compared with that of healthy controls. A higher frequency of CD56bright NK subsets was found in CHB patients, but the CD56dim NK subsets of CHB patients and healthy controls were similar. CHB patients before and after antiviral therapy with nucleotide analogues (NUCs) showed no statistical difference in NK frequency. The activating receptors were upregulated, whereas inhibitory receptors were comparable in the peripheral NK cells of CHB individuals and healthy controls. NK cells of CHB patients displayed higher cytotoxic potency as evidenced by CD107a protein levels and conserved potency to produce interferon-gamma (IFNγ), compared with their healthy counterparts.

CONCLUSION

Our results revealed that CHB patients had a lower frequency of NK cells compared with healthy individuals not treatable with antiviral NUC therapy. With an activating phenotype, NK cells in CHB patients showed better cytotoxic potency and conserved IFNγ production.

Role natural killer group 2D-ligand interactions in hepatitis B infection

Hepatitis B virus (HBV) infection is the leading cause of liver disease and hepatocellular carcinoma (HCC) worldwide, in spite of prophylactic vaccination and antiviral treatment modalities. The immunopathogenesis of HBV infection has been intensively studied and is propelled by complex interactions between the virus and the host immune system. Natural killer group 2D (NKG2D) is a well-characterized activating receptor, expressed on natural killer (NK) cells, NK T cells and CD8⁺ cytotoxic T cells. This receptor is present in both humans and mice and binds to a diverge family of ligands that resemble the MHC-class I molecules. Increasing evidence shows that NKG2D-ligand interactions are critical in the establishment of HBV persistence and the development of liver injury and HCC. The expression of NKG2D ligands depends on the presence of several polymorphisms and is also modulated post-transcriptionally by HBV. While it is known that HBV circumvents host’s innate immunity via the NKG2D pathway but the exact mechanisms involved are still elusive. This letter discusses previous accomplishments on the role of NKG2D ligand regulation in the development of chronic HBV, liver injury and HCC.

Natural Killer p46 Controls Hepatitis B Virus Replication and Modulates Liver Inflammation

Natural killer (NK) cells play an important role in hepatitis B virus (HBV) infection control, and are regulated by a complex network of activating and inhibitory receptors. However, NK cell activity in HBV patients remains poorly understood. The objective of this study was to investigate the phenotypic and functional characteristics of circulating NK cells in patients during different chronic hepatitis B (CHB) infection stages. We investigated NK cell phenotypes, receptor expression and function in 86 CHB patients and 20 healthy controls. NK cells were purified and NK cell subsets were characterized by flow cytometry. Cytotoxic activity (CD107a) and interferon-gamma (IFN-γ) secretion were examined, and Natural Killer p46 (NKP46) blockade and spontaneous NK cell cytolytic activity against K562, HepG2 and HepG2.215 cell lines was studied. Activating NKp46 receptor expression was higher in inactive HBsAg carriers when compared with other groups (p = 0.008). NKp46 expression negatively correlated with HBV DNA (R = -0.253, p = 0.049) and ALT (R = -0.256, p = 0.045) levels. CD107a was higher in immune-activated groups when compared with immune-tolerant groups (p = 0.039). CD107a expression was related to viral load (p = 0.02) and HBeAg status (p = 0.024). In vitro NKp46 blockade reduced NK cell cytolytic activity against HepG2 and HepG2.215 cell lines (p = 0.02; p = 0.039). Furthermore, NK cells from high viral load CHB patients displayed significantly lower specific cytolytic activity against anti-NKp46-loaded K562 targets (p = 0.0321). No significant differences were observed in IFN-γ secretion (p > 0.05). In conclusion, NKp46 expression regulates NK cell cytolytic function. NKp46 may moderate NK cell activity during HBV replication suppression and HBV-associated liver damage and may be critical for NK cell activity during CHB infection.

Decreased peripheral natural killer cells activity in the immune activated stage of chronic hepatitis B

Background & Aims

The natural course of chronic hepatitis B virus (HBV) infection is characterized by different immune responses, ranging from immune tolerant (IT) to immune activated (IA) stages. In our study, we investigated the natural killer (NK) cells activity in patients at different immunological stages of chronic HBV infection.

Methods

Blood samples obtained from 57 HBeAg positive patients with chronic hepatitis B (CHB), including 15 patients in the immune tolerant (IT) stage, 42 patients in the immune activated (IA) stage, and 18 healthy individuals (HI). The analyses included flow cytometry to detect NK cells, the determination of cytokine levels as well as of surface receptor expression and cytotoxicity.

Results

NK cells in peripheral blood were significantly lower in patients in the IA stage of CHB compared to HI (p<0.05). Patients in the IA stage of CHB had lower levels of NK cells activating receptor NKp30 and NKG2D expression, cytokine interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) production, as compared to patients in the IT stage and HI, respectively (p<0.05). Cytotoxicity of NK cells was lower in patients in the IA stage of CHB compared to patients in the IT stage and HI, respectively (p<0.05). The level of IFN-γ but not level of TNF-α and cytotoxicity of NK cells was inversely correlated with serum HBV load in patients with CHB. Peripheral NK cells activity did not correlate with ALT level.

Conclusion

NK cells activity was lower in CHB patients, especially in those in the IA stage.

Hepatitis B virus-related immune reconstitution inflammatory syndrome in two patients coinfected with human immunodeficiency virus diagnosed with a liver biopsy

Hepatic flares occurred in two patients with HBV/HIV coinfection following the commencement of antiretroviral therapy (ART). At that time, the HIV RNA and HBV DNA levels had decreased. The results of liver biopsies showed lymphocytic infiltration that was diffusely positive for CD8(+) T cells in the portal areas and lobules. These findings suggested HBV-related immune reconstitution inflammatory syndrome (IRIS). The alanine aminotransferase levels of both patients gradually decreased with the continuation of ART. Because there are few reports of the liver histology of HBV-related IRIS, these cases provide a better understanding of the pathogenesis of HBV-related IRIS.

HIV and co-infections

Despite significant reductions in morbidity and mortality secondary to availability of effective combination anti-retroviral therapy (cART), human immunodeficiency virus (HIV) infection still accounts for 1.5 million deaths annually. The majority of deaths occur in sub-Saharan Africa where rates of opportunistic co-infections are disproportionately high. In this review, we discuss the immunopathogenesis of five common infections that cause significant morbidity in HIV-infected patients globally. These include co-infection with Mycobacterium tuberculosis, Cryptococcus neoformans, hepatitis B virus, hepatitis C virus, and Plasmodium falciparum. Specifically, we review the natural history of each co-infection in the setting of HIV, the specific immune defects induced by HIV, the effects of cART on the immune response to the co-infection, the pathogenesis of immune restoration disease (IRD) associated with each infection, and advances in the areas of prevention of each co-infection via vaccination. Finally, we discuss the opportunities and gaps in knowledge for future research.

Influence of B cells in liver fibrosis associated with hepatitis B virus harboring basal core promoter mutations

The development of the liver disease in chronic hepatitis B with common viral variants can be determined through the interaction between the virus and the host immune response. B cells constitute half of the intrahepatic lymphocyte population with an impact on fibrosis. A proliferation-inducing ligand (APRIL) has been shown to have a co-stimulatory activity on B cells. For this study HBV DNA was amplified and then sequenced to show the presence of the basal core promoter (BCP) mutations in the serum from 57 patients with chronic hepatitis B. The range of IgD-positive B cells was detected by immunohistochemistry in liver biopsies; and patients serum was assayed for APRIL levels by enzyme immunoassay. Twenty-seven patients (47.4%) harbored the A1762T-G1764A BCP mutations. Coefficients of logistic regression showed that the effect of increasing IgD-positive B cells in rising odds of the liver disease is the same in the patients with BCP mutation A1762T-G1764A and in the patients without mutation, nevertheless the effect of APRIL is not similar in these two groups of patients. Logistic regression in patients with BCP A1762T-G1764A mutations demonstrated that increasing one score of APRIL decreased the odds of fibrosis stage about 8%. These results suggest that in infection with viral variants of hepatitis B virus, the population of IgD-positive B cells may play a decisive role in later stages of the liver disease which is reduced by APRIL in chronic hepatitis patients with BCP mutations.

NK cells: a double-edged sword in chronic hepatitis B virus infection

There is natural enrichment of NK cells in the human liver and this intrahepatic predominance underscores their potential importance in the control of infections with hepatotropic viruses such as hepatitis B virus (HBV). The contribution of innate components during chronic HBV infection has been a relatively under-investigated area. However, recent data have highlighted that NK cells are capable of exerting antiviral and immunoregulatory functions whilst also contributing to the pathogenesis of liver injury via death receptor pathways. We will present an overview of current knowledge regarding the complex biology of NK cells in the context of their antiviral versus pathogenic role in chronic hepatitis B as a clinically relevant avenue for further investigation.

Natural killer cells in viral hepatitis: facts and controversies

BACKGROUND

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are major human hepatotropic pathogens responsible for a large number of chronic infections worldwide. Their persistence is thought to result from inefficiencies of innate and adaptive immune responses; however, very little information is available on the former. Natural killer (NK) cells are a major component of innate immunity and their activity is tightly regulated by several inhibitory and activating receptors.

DESIGN

In this review, we examine controversial findings regarding the role of NK cells in the pathogenesis of acute and chronic liver disease caused by HCV and HBV.

RESULTS

Recent studies built up on technical advances to identify NK receptors and their functional correlates in this setting. While NK cells seem to behave correctly during acute hepatitis, it would appear that the NK cytotoxic potential is generally conserved in chronic hepatitis, if not increased in the case of HCV. In contrast, their ability to secrete antiviral cytokines such as interferon ex vivo or after cytokine stimulation is severely impaired.

CONCLUSIONS

Current evidence suggests the existence of an NK cell functional dichotomy, which may contribute to virus persistence, while maintaining low-level chronic liver inflammation. The study of liver-infiltrating NK cells is still at the very beginning, but it is likely that it will shed more light on the role of this simple and at the same time complex innate immune cell in liver disease.

Down-regulation of Z39Ig on macrophages by IFN-gamma in patients with chronic HBV infection

Co-inhibitory signals from the B7 superfamily have been demonstrated to induce T cell dysfunction in chronic HBV infection (CHB). However, the expression and function of Z39Ig, a new inhibitor of the B7 superfamily, is still unclear in CHB. Here immunohistochemical staining showed that Z39Ig was restricted to macrophages and that its level was decreased significantly in CHB patients compared to healthy controls. Moreover, reduced Z39Ig expression was positively correlated with plasma HBV load but was inversely related to serum alanine aminotransaminase levels. Further, Z39Ig mRNA had a negative relation to IFN-gamma in vivo, and IFN-gamma also down-regulated Z39Ig expression on monocyte-derived macrophages (MDMs) in a time- and dose-dependent manner in vitro. Interestingly, Z39Ig expression on MDMs was restored when IFN-gamma neutralizing antibodies were added to the T cell/MDM co-culture system, indicating that the IFN-gamma derived from activated-T cells may contribute to the reduction of Z39Ig in the CHB environment. Our results suggest that T cells can opposite T cell hyporesponsiveness through dampening Z39Ig inhibitory signals from macrophages and thus maintain their anti-viral function in CHB. Therefore, decreasing Z39Ig signals from macrophages could contribute to CHB clinical therapy.

Immune restoration diseases reflect diverse immunopathological mechanisms

Up to one in four patients infected with human immunodeficiency virus type 1 and given antiretroviral therapy (ART) experiences inflammatory or cellular proliferative disease associated with a preexisting opportunistic infection, which may be subclinical. These immune restoration diseases (IRD) appear to result from the restoration of immunocompetence. IRD associated with intracellular pathogens are characterized by cellular immune responses and/or granulomatous inflammation. Mycobacterial and cryptococcal IRD are attributed to a pathological overproduction of Th1 cytokines. Clinicopathological characteristics of IRD associated with viral infections suggest different pathogenic mechanisms. For example, IRD associated with varicella-zoster virus or JC polyomavirus infection correlate with a CD8 T-cell response in the central nervous system. Exacerbations or de novo presentations of hepatitis associated with hepatitis C virus (HCV) infection following ART may also reflect restoration of pathogen-specific immune responses as titers of HCV-reactive antibodies rise in parallel with liver enzymes and plasma markers of T-cell activation. Correlations between immunological parameters assessed in longitudinal sample sets and clinical presentations are required to illuminate the diverse immunological scenarios described collectively as IRD. Here we present salient clinical features and review progress toward understanding their pathogeneses.

Hepatitis virus immune restoration disease of the liver

PURPOSE OF REVIEW

Co-infection of HIV with hepatitis B virus or hepatitis C virus is common. Hepatotoxicity (grade 3 or 4 transaminitis) after highly active antiretroviral therapy occurs more frequently in either hepatitis B virus or hepatitis C virus co-infection. The cause of abnormal alanine aminotransferase following the initiation of highly active antiretroviral therapy is often multifactorial, and may include immune restoration disease. Since the widespread use of highly active antiretroviral therapy, liver disease secondary to viral hepatitis has become one of the most common causes of death in HIV infected individuals. A better understanding of the immunopathogenesis, diagnosis and treatment of hepatitis immune restoration disease is urgently needed, therefore.

RECENT FINDINGS

Our current understanding of the immunopathogenesis of hepatitis immune restoration disease is limited but it is likely that hepatic damage is secondary to recruitment of both antigen-specific and nonantigen-specific mononuclear cells to the liver, possibly mediated by IFN-gamma. HIV-hepatitis B virus co-infected individuals with low CD4 T-cells and elevated hepatitis B virus DNA and alanine aminotransferase prior to initiation of highly active antiretroviral therapy are at increased risk of hepatitis B virus immune restoration disease. Risk factors for hepatitis C virus immune restoration disease are less well defined. Although clinical deterioration can occur, hepatitis immune restoration disease has also been associated with successful clearance of both hepatitis B virus and hepatitis C virus.

SUMMARY

Further randomized clinical trials are needed to develop improved management strategies for hepatitis immune restoration disease.

[Relationship between the phenotypes and functions of peripheral blood dendritic cells and the different spleen deficiency syndrome types in patients with chronic hepatitis B]

OBJECTIVE

To study the phenotypes and functions of dendritic cells (DCs) derived from peripheral blood monocytes of chronic hepatitis B (CHB) patients with different traditional Chinese medicine (TCM) syndrome types, and to explore the relationship between TCM syndrome type and DC functions.

METHODS

Sixty CHB patients were included in this study. All the CHB patients were divided into spleen deficiency and liver stagnation, spleen deficiency and dampness-heat and deficiency of both spleen and kidney groups according to TCM syndrome diagnosis standard. There were 20 cases in each group, and ten healthy people were included as normal control. The volunteer's peripheral blood was collected for monocyte separation, biochemical test and hepatitis B virus DNA loads detection. DCs were induced and isolated from peripheral blood monocytes, and then the expressions of surface markers CD80, CD86, CD1a and HLA-DR were detected by flow cytometric analysis method. Interleukin-10 (IL-10) production of the DCs was quantified by enzyme-linked immunosorbent assay.

RESULTS

The proliferation of DCs in the CHB patients was slower than that in the healthy volunteers (P<0.05). The expressions of DC surface molecules such as CD80, CD86, and CD1a were obviously decreased in the CHB patients as compared with those in the healthy volunteers (P<0.05). More over, expressions of DC surface molecules were different among CHB patients with different TCM syndrome types. The positive expressions of CD80, CD1a, and HLA-DR in the CHB patients with spleen deficiency and liver stagnation were obviously higher than those in the CHB patients with deficiency of both spleen and kidney (P<0.05), and the CD1a expression in the CHB patients with spleen deficiency and dampness-heat was higher than that in the CHB patients with deficiency of both spleen and kidney (P<0.05). In DC culture supernatant, the IL-10 concentration of the CHB patients with deficiency of both spleen and kidney was higher than that of the CHB patients with spleen deficiency and liver stagnation (P<0.05), and the IL-10 concentrations of the CHB patients with different TCM syndrome types were higher than that of the healthy volunteers (P<0.05).

CONCLUSION

During the pathogenic course of CHB, the phenotypes and functions of DCs are different in CHB patients with different TCM syndrome types. It suggests that there is a correlation between TCM syndrome type and body immunity function.

Cytokine expression during chronic versus occult hepatitis B virus infection in HIV co-infected individuals

Chronic hepatitis B virus infection is characterized by persistent detectable levels of hepatitis B surface antigen (HBsAg) and HBV DNA in the serum. In contrast, HBsAg is not detectable during occult HBV infection, despite the presence of HBV DNA. An altered host immune response could play a role in the development of occult HBV infection; however, potential differences in immune responses among chronic and occult HBV-infected patients have not been evaluated in vivo. In the current study, we evaluated serum levels of regulatory, apoptotic, and fibrotic/anti-fibrotic cytokines/markers as indicators of immune responses in 25 chronic and 12 occult HBV-infected patients. More than half of the patients in both chronic and occult HBV infection groups had IL-2, IL-4, IL-13, and IFN-gamma levels below detectable limits. In contrast, most patients had detectable levels of IL-8, IL-10, IP-10, sFas, sFasL, and TGF-beta1. Of these, only sFas was significantly different between the two groups, with lower levels observed during occult compared to chronic HBV infection (p=0.01). As a surrogate marker of apoptotic inhibition, decreased sFas during occult HBV infection suggests that apoptosis occurs at different rates in occult compared to chronic HBV infection and therefore, may contribute to persistence of occult HBV infection.

Peripheral T-lymphocyte subpopulations in different clinical stages of chronic HBV infection correlate with HBV load

AIM

To characterize the peripheral T-cell subpopulation profiles and their correlation with hepatitis B virus (HBV) replication in different clinical stages of chronic HBV infection.

METHODS

A total of 422 patients with chronic HBV infection were enrolled in this study. The patients were divided into three stages: immune-tolerant stage, immune active stage, and immune-inactive carrier stage. Composition of peripheral T-cell subpopulations was determined by flow cytometry. HBV markers were detected by enzyme-linked immunosorbent assay. Serum HBV DNA load was assessed by quantitative real-time polymerase chain reaction.

RESULTS

CD8(+) T-cells were significantly higher in patients at the immune-tolerant stage than in patients at the immune-active and -inactive carrier stages (36.87 +/- 7.58 vs 34.37 +/- 9.07, 36.87 +/- 7.58 vs 28.09 +/- 5.64, P < 0.001). The peripheral blood in patients at the immune-tolerant and immune active stages contained more CD8(+) T-cells than CD4(+) T-cells (36.87 +/- 7.58 vs 30.23 +/- 6.35, 34.37 +/- 9.07 vs 30.92 +/- 7.40, P < 0.01), whereas the peripheral blood in patients at the immune-inactive carrier stage and in normal controls contained less CD8(+) T-cells than CD4(+) T-cells (28.09 +/- 5.64 vs 36.85 +/- 6.06, 24.02 +/- 4.35 vs 38.94 +/- 3.39, P < 0.01). ANOVA linear trend test showed that CD8(+) T-cells were significantly increased in patients with a high viral load (39.41 +/- 7.36, 33.83 +/- 7.50, 31.81 +/- 5.95 and 26.89 +/- 5.71, P < 0.001), while CD4(+) T-cells were significantly increased in patients with a low HBV DNA load (37.45 +/- 6.14, 33.33 +/- 5.61, 31.58 +/- 6.99 and 27.56 +/- 5.49, P < 0.001). Multiple regression analysis displayed that log copies of HBV DNA still maintained its highly significant coefficients for T-cell subpopulations, and was the strongest predictors for variations in CD3(+), CD4(+) and CD8(+) cells and CD4(+)/CD8(+) ratio after adjustment for age at HBV-infection, maternal HBV-infection status, presence of hepatitis B e antigen and HBV mutation.

CONCLUSION

Differences in peripheral T-cell subpopulation profiles can be found in different clinical stages of chronic HBV infection. T-cell impairment is significantly associated with HBV load.

Impaired quality of the hepatitis B virus (HBV)-specific T-cell response in human immunodeficiency virus type 1-HBV coinfection

Hepatitis B virus (HBV)-specific T cells play a key role both in the control of HBV replication and in the pathogenesis of liver disease. Human immunodeficiency virus type 1 (HIV-1) coinfection and the presence or absence of HBV e (precore) antigen (HBeAg) significantly alter the natural history of chronic HBV infection. We examined the HBV-specific T-cell responses in treatment-naïve HBeAg-positive and HBeAg-negative HIV-1-HBV-coinfected (n = 24) and HBV-monoinfected (n = 39) Asian patients. Peripheral blood was stimulated with an overlapping peptide library for the whole HBV genome, and tumor necrosis factor alpha and gamma interferon cytokine expression in CD8+ T cells was measured by intracellular cytokine staining and flow cytometry. There was no difference in the overall magnitude of the HBV-specific T-cell responses, but the quality of the response was significantly impaired in HIV-1-HBV-coinfected patients compared with monoinfected patients. In coinfected patients, HBV-specific T cells rarely produced more than one cytokine and responded to fewer HBV proteins than in monoinfected patients. Overall, the frequency and quality of the HBV-specific T-cell responses increased with a higher CD4+ T-cell count (P = 0.018 and 0.032, respectively). There was no relationship between circulating HBV-specific T cells and liver damage as measured by activity and fibrosis scores, and the HBV-specific T-cell responses were not significantly different in patients with either HBeAg-positive or HBeAg-negative disease. The quality of the HBV-specific T-cell response is impaired in the setting of HIV-1-HBV coinfection and is related to the CD4+ T-cell count.

A synergistic interferon-gamma production is induced by mouse hepatitis virus in interleukin-12 (IL-12)/IL-18-activated natural killer cells and modulated by carcinoembryonic antigen-related cell adhesion molecules (CEACAM) 1a receptor

The production of interferon-gamma (IFN-gamma) by infiltrating natural killer (NK) cells in liver is involved in the control of mouse hepatitis virus (MHV) infection. The objectives of this study were to identify the mechanisms used by MHV type 3 to modulate the production of IFN-gamma by NK cells during the acute hepatitis in susceptible C57BL/6 mice. Ex vivo and in vitro experiments revealed that NK cells, expressing carcinoembryonic antigen-related cell adhesion molecules (CEACAM) 1a (the MHV receptor), can produce a higher level of IFN-gamma in the presence of both L2-MHV3 and interleukin-12 (IL-12)/IL-18. The synergistic production of IFN-gamma by NK cells depends on viral replication rather than viral fixation only, because it is inhibited or not induced in cells infected with ultraviolet-inactivated viruses and in cells from Ceacam1a(-/-) mice infected with virulent viruses. The synergistic IFN-gamma production involves the p38 mitogen-activated protein kinase (MAPK) rather than the extracellular signal-regulated kinase-1/2 MAPK signalling pathway. However, the signal triggered through the engagement of CEACAM1a decreases the production of IFN-gamma, when these molecules are cross-linked using specific monoclonal antibodies. These results suggest that control of acute hepatitis by IFN-gamma-producing NK cells may depend on both production of IL-12 and IL-18 in the liver environment and viral infection of NK cells.

NK and NKT cells in liver injury and fibrosis

The innate immune mechanisms of the liver represent an important first line of defense against bacterial products, toxins, and food antigens coming from the intestine. Natural Killer (NK) and Natural Killer T cells (NKT) are components of the innate immune system with increased presence in the liver compared to other organs and have been reported to participate in the inflammatory processes during hepatic diseases. However significant confusion has been noted in this field mainly due to changes in the characterization of these cells as new knowledge accumulates and due to differences in the approaches used for their study. Both cell types can mediate hepatic injury in several models but studies in human liver diseases have not managed to fully explain their functions. However accumulating evidence supports an antifibrotic role of NK cells mainly via an inhibitory effect on hepatic stellate cells by inducing apoptosis and via production of interferon-gamma. Therefore, downregulation of NK cells during most types of liver injury may facilitate liver fibrosis. Data about the role of NKT cells in liver fibrosis are limited. This review will summarize the studies about the role of NK and NKT cells in liver diseases with a special interest in hepatic injury and liver fibrosis.

The phenotype of hepatitis B virus-specific T cells differ in the liver and blood in chronic hepatitis B virus infection

Hepatitis B virus (HBV)-specific T cells play a key role in clearance of the virus and in the pathogenesis of liver disease. Peripheral blood (n = 25) and liver biopsies (n = 19) were collected from individuals with chronic untreated HBV infection. Whole blood, cultured peripheral blood mononuclear cells (PBMCs), and cultured liver-infiltrating lymphocytes (LILs) were each stimulated with an overlapping peptide library to the whole HBV genome. The expression of T helper 1 (Th1) cytokines [interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin 2 (IL-2)] and interleukin 10 (IL-10) was analyzed by intracellular cytokine staining and flow cytometry. In ex vivo whole blood, more lymphocytes produced Th1 cytokines than IL-10. When comparing cultured LILs with cultured PBMCs, we found a significantly higher magnitude of CD8(+) T cells from the liver producing IL-10 (P = 0.044), primarily in hepatitis B e antigen positive (HBeAg(+)) individuals. A positive correlation resulted between the magnitude of HBV-specific TNF-alpha(+) CD4(+) T cells in the liver and the degree of liver inflammation and fibrosis (P = 0.002 and P = 0.006, respectively).

CONCLUSION

The differences in cytokine production from HBV-specific T cells in blood and liver may explain the capacity for HBV to persist in the absence of significant hepatic destruction and highlights the balance between cytokine-mediated viral control and liver damage.

B7-H1 up-regulation on myeloid dendritic cells significantly suppresses T cell immune function in patients with chronic hepatitis B

Although dysfunctional dendritic cells contribute to inadequate adaptive immunity in chronic hepatitis B (CHB), underlying molecular mechanisms remain largely undefined. In this study, we examined B7-H1 expression on circulating myeloid dendritic cells (mDCs) in 46 CHB patients, 10 autoimmune hepatitis patients, and 10 healthy subjects as control. We found that B7-H1 expression is significantly up-regulated on circulating mDCs of CHB and autoimmune hepatitis patients compared with healthy individuals. The B7-H1 up-regulation was significantly correlated with an elevation of serum alanine aminotransaminase levels and plasma viral load. In addition, in vitro, both IFN-alpha and IFN-gamma could strongly stimulate mDCs to express B7-H1. More importantly, elevated B7-H1 expression is also closely associated with the suppression of T cell immune function. In vitro blockade of B7-H1 signaling could not only down-regulate IL-10 and up-regulate IL-12 production by mDCs, but also enhance mDC-mediated allostimulatory capacity and cytokine production of T cells. Blockade of B7-H1 signaling could improve hepatitis B c Ag-pulsed monocyte-derived DC-induced IFN-gamma production by autologous hepatitis B virus-specific T cells. These new findings suggested that chronic inflammation may contribute to B7-H1 up-regulation on mDCs in CHB patients, which potentially cause defective hepatitis B virus-specific T cell function and viral persistence. Our findings further support the notion that the blockade of B7-H1 may represent a novel therapeutic approach for this disease.

Cytokines induced during chronic hepatitis B virus infection promote a pathway for NK cell-mediated liver damage

Hepatitis B virus (HBV) causes chronic infection in more than 350 million people worldwide. It replicates in hepatocytes but is non-cytopathic; liver damage is thought to be immune mediated. Here, we investigated the role of innate immune responses in mediating liver damage in patients with chronic HBV infection. Longitudinal analysis revealed a temporal correlation between flares of liver inflammation and fluctuations in interleukin (IL)-8, interferon (IFN)-α, and natural killer (NK) cell expression of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) directly ex vivo. A cross-sectional study confirmed these findings in patients with HBV-related liver inflammation compared with healthy carriers. Activated, TRAIL-expressing NK cells were further enriched in the liver of patients with chronic HBV infection, while their hepatocytes expressed increased levels of a TRAIL death–inducing receptor. IFN-α concentrations found in patients were capable of activating NK cells to induce TRAIL-mediated hepatocyte apoptosis in vitro. The pathogenic potential of this pathway could be further enhanced by the ability of the IFN-α/IL-8 combination to dysregulate the balance of death-inducing and regulatory TRAIL receptors expressed on hepatocytes. We conclude that NK cells may contribute to liver inflammation by TRAIL-mediated death of hepatocytes and demonstrate that this non-antigen–specific mechanism can be switched on by cytokines produced during active HBV infection.

Immunopathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) infection is a non-cytopathic hepatotropic virus that can lead to severe liver disease including acute hepatitis, cirrhosis and hepatocellular carcinoma. Successful clearance of the virus as well as the establishment of liver disease is largely driven by a complex interaction between the virus and the host immune response. In this review, the immunological events, including both the innate and adaptive immune response are discussed in the setting of both acute and chronic HBV infection and liver disease.

Increased infiltration of intrahepatic DC subsets closely correlate with viral control and liver injury in immune active pediatric patients with chronic hepatitis B

The roles of functionally impaired dendritic cells (DCs) in natural history of chronic hepatitis B (CHB) are unknown. We therefore characterized circulating DC subsets in 15 immune tolerant (IT) and 31 immune active (IA) HBV-infected children. Additionally, intrahepatic DC subsets were also analyzed in 4 IT and 9 IA individuals. The results showed that circulating DC subset numbers were decreased, but the intrahepatic DC counts were concomitantly increased in IA patients versus IT patients or healthy children. This results in the reduction of overall IFN-alpha but not IL-12 production by peripheral blood mononuclear cells of IA patients, although the capacity of single DC in producing cytokines was unchanged in these children. Moreover, there is a significantly inverse correlation of intrahepatic DC subsets with plasma HBV load and a positive correlation with serum ALT levels. These findings suggest that the increased infiltration of intrahepatic DC subsets may participate in the local antiviral immune response in pediatric patients with CHB.