HBV antiviral immunity: not all CD8 T cells are born equal

HBsAg level defines different clinical phenotypes of HBeAg(-) chronic HBV infection related to HBV polymerase-specific CD8+ cell response quality

Background

HBe-antigen(Ag)-negative chronic hepatitis B virus (HBV) infection is characterized by little liver fibrosis progression and vigorous HBV-multispecific CD8+ T-cell response.

Aims

To assess whether HBsAg level could discriminate different HBeAg-negative chronic HBV infection subtypes with dissimilar quality of HBV-specific CD8+ T-cell response.

Methods

We recruited 63 HBeAg-negative chronic HBV infection patients in which indirect markers of liver inflammation/fibrosis, portal pressure, viral load (VL), and HBV-specific CD8+ cell effector function were correlated with HBsAg level.

Results

A positive linear trend between HBsAg level and APRI, liver stiffness (LS), liver transaminases, and HBV VL, and a negative correlation with platelet count were observed. Frequency of cases with HBV-specific CD8+ T-cell proliferation against at least two HBV epitopes was higher in HBsAg < 1,000 IU/ml group. CD8+ T-cell expansion after HBVpolymerase456-63-specific stimulation was impaired in HBsAg > 1,000 IU/ml group, while the response against HBVcore18-27 was preserved and response against envelope183-91 was nearly abolished, regardless of HBsAg level. Cases with preserved HBVpolymerase456-63 CD8+ cell response had lower LS/duration of infection and APRI/duration of infection rates. HBV-polymerase456-63-specific CD8+ T-cell proliferation intensity was negatively correlated with LS/years of infection ratio.

Conclusion

HBsAg > 1,000 IU/ml HBeAg-negative chronic HBV infection group shows indirect data of higher degree of inflammation, liver stiffness, and fibrosis progression speed, which are related to an impaired HBV-polymerase-specific CD8+ T-cell response.

Classifying hepatitis B therapies with insights from covalently closed circular DNA dynamics

The achievement of a functional cure for chronic hepatitis B (CHB) remains limited to a minority of patients treated with currently approved drugs. The primary objective in developing new anti-HBV drugs is to enhance the functional cure rates for CHB. A critical prerequisite for the functional cure of CHB is a substantial reduction, or even eradication of covalently closed circular DNA (cccDNA). Within this context, the changes in cccDNA levels during treatment become as a pivotal concern. We have previously analyzed the factors influencing cccDNA dynamics and introduced a preliminary classification of hepatitis B treatment strategies based on these dynamics. In this review, we employ a systems thinking perspective to elucidate the fundamental aspects of the HBV replication cycle and to rationalize the classification of treatment strategies according to their impact on the dynamic equilibrium of cccDNA. Building upon this foundation, we categorize current anti-HBV strategies into two distinct groups and advocate for their combined use to significantly reduce cccDNA levels within a well-defined timeframe.

Metabolic interventions improve HBV envelope-specific T-cell responses in patients with chronic hepatitis B

BACKGROUND

Restoration of HBV-specific T cell immunity is a promising approach for the functional cure of chronic Hepatitis B (CHB), necessitating the development of valid assays to boost and monitor HBV-specific T cell responses in patients with CHB.

METHODS

We analyzed hepatitis B virus (HBV) core- and envelope (env)-specific T cell responses using in vitro expanded peripheral blood mononuclear cells (PBMCs) from patients with CHB exhibiting different immunological phases, including immune tolerance (IT), immune activation (IA), inactive carrier (IC), and HBeAg-negative hepatitis (ENEG). Additionally, we evaluated the effects of metabolic interventions, including mitochondria-targeted antioxidants (MTA), polyphenolic compounds, and ACAT inhibitors (iACAT), on HBV-specific T-cell functionality.

RESULTS

We found that HBV core- and env-specific T cell responses were finely coordinated and more profound in IC and ENEG than in the IT and IA stages. HBV env-specific T cells were more dysfunctional but prone to respond to metabolic interventions using MTA, iACAT, and polyphenolic compounds than HBV core-specific T-cells. The responsiveness of HBV env-specific T cells to metabolic interventions can be predicted by the eosinophil (EO) count and the coefficient of variation of red blood cell distribution width (RDW-CV).

CONCLUSION

These findings may provide valuable information for metabolically invigorating HBV-specific T-cells to treat CHB.

Interspecies comparison of the early transcriptomic changes associated with hepatitis B virus exposure in human and macaque immune cell populations

BACKGROUND AND AIMS

Hepatitis B virus (HBV) infection affects 300 million individuals worldwide, representing a major factor for the development of hepatic complications. Although existing antivirals are effective in suppressing replication, eradication of HBV is not achieved. Therefore, a multi-faceted approach involving antivirals and immunomodulatory agents is required. Non-human primates are widely used in pre-clinical studies due to their close evolutionary relationship to humans. Nonetheless, it is fundamental to identify the differences in immune response between humans and these models. Thus, we performed a transcriptomic characterization and interspecies comparison of the early immune responses to HBV in human and cynomolgus macaques.

METHODS

We characterized early transcriptomic changes in human and cynomolgus B cells, T cells, myeloid and plasmacytoid dendritic cells (pDC) exposed to HBV ex vivo for 2 hours. Differentially-expressed genes were further compared to the profiles of HBV-infected patients using publicly-available single-cell data.

RESULTS

HBV induced a wide variety of transcriptional changes in all cell types, with common genes between species representing only a small proportion. In particular, interferon gamma signaling was repressed in human pDCs. At the gene level, interferon gamma inducible protein 16 (IFI16) was upregulated in macaque pDCs, while downregulated in humans. Moreover, IFI16 expression in pDCs from chronic HBV-infected patients anti-paralleled serum HBsAg levels.

CONCLUSION

Our characterization of early transcriptomic changes induced by HBV in humans and cynomolgus macaques represents a useful resource for the identification of shared and divergent host responses, as well as potential immune targets against HBV.

TRAF2 as a key candidate gene in clinical hepatitis B-associated liver fibrosis

Objectives: Approximately 240 million individuals are infected with chronic hepatitis B virus (HBV) worldwide. HBV infection can develop into liver fibrosis. The mechanism of HBV-related liver fibrosis has not been fully understood, and there are few effective treatment options. The goal of this study was to use transcriptomics in conjunction with experimental validation to identify new targets to treat HBV-related liver fibrosis. Methods: To identify differentially expressed genes (DEGs), five liver tissues were collected from both healthy individuals and patients with chronic hepatitis B. NovoMagic and Java GSEA were used to screen DEGs and key genes, respectively. Immunocell infiltration analysis of RNA-seq data was, and the results were confirmed by Western blotting (WB), real-time quantitative polymerase chain reaction (RT-qPCR), and immunohistochemistry. Results: We evaluated 1,105 genes with differential expression, and 462 and 643 genes showed down- and upregulation, respectively. The essential genes, such as tumor necrosis factor (TNF) receptor-associated factor-2 (TRAF2), were screened out of DEGs. TRAF2 expression was abnormally high in hepatic fibrosis in patients with hepatitis B compared with healthy controls. The degree of hepatic fibrosis and serum levels of glutamate transaminase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBIL) were positively linked with TRAF2 expression. TRAF2 may be crucial in controlling T lymphocyte-mediated liver fibrosis. Conclusion: Our findings imply that TRAF2 is essential for HBV-induced liver fibrosis progression, and it may potentially be a promising target for the treatment of hepatic fibrosis in hepatitis B.

Monocytic MDSCs homing to thymus contribute to age-related CD8+ T cell tolerance of HBV

Hepatitis B virus exposure in children usually develops into chronic hepatitis B (CHB). Although hepatitis B surface antigen (HBsAg)–specific CD8⁺ T cells contribute to resolve HBV infection, they are preferentially undetected in CHB patients. Moreover, the mechanism for this rarely detected HBsAg-specific CD8⁺ T cells remains unexplored. We herein found that the frequency of HBsAg-specific CD8⁺ T cells was inversely correlated with expansion of monocytic myeloid-derived suppressor cells (mMDSCs) in young rather than in adult CHB patients, and CCR9 was upregulated by HBsAg on mMDSCs via activation of ERK1/2 and IL-6. Sequentially, the interaction between CCL25 and CCR9 mediated thymic homing of mMDSCs, which caused the cross-presentation, transferring of peripheral HBsAg into the thymic medulla, and then promoted death of HBsAg-specific CD8⁺ thymocytes. In mice, adoptive transfer of mMDSCs selectively obliterated HBsAg-specific CD8⁺ T cells and facilitated persistence of HBV in a CCR9-dependent manner. Taken together, our results uncovered a novel mechanism for establishing specific CD8⁺ tolerance to HBsAg in chronic HBV infection.

Risks and Benefits of Discontinuation of Nucleos(t)ide Analogue Treatment: A Treatment Concept for Patients With HBeAg-Negative Chronic Hepatitis B

Systematic discontinuation of long-term treatment with nucleos(t)ide analogues (NAs) is one strategy to increase functional cure rates in patients with chronic hepatitis B e antigen (HBeAg)-negative hepatitis B. Currently, available study results are heterogeneous; however, long-term hepatitis B surface antigen (HBsAg) loss rates of up to 20% have been reported in prospective trials. This review proposes criteria that can be used when considering NA discontinuation in patients with chronic hepatitis B virus (HBV). Discontinuing NA treatment frequently results in a virologic and biochemical relapse that runs through different phases: the lag phase, reactivation phase, and consolidation phase. The HBV-DNA flares observed during the reactivation phase are often transient and most likely represent a trigger for inducing a long-term immune control by specific CD8+ T cells, and therefore do not need immediate interventions but close follow-up evaluation. Low HBsAg levels at the time of treatment cessation predict a positive long-term response to NA discontinuation associated with a higher likelihood of HBsAg clearance. Other host and viral biomarkers are currently under evaluation that may prove to be helpful to further characterize the population that may benefit most from the finite NA treatment concept. Potential harmful biochemical flares during the reactivation phase need to be identified early and can be effectively terminated by reintroducing NA treatment. Hepatic decompensation represents a risk to patients with cirrhosis undergoing NA discontinuation. Therefore, the finite NA approach should only be considered after excluding advanced fibrosis and cirrhosis and if a close follow-up of the patient and supervision by an experienced physician can be guaranteed. Conclusion: For selected patients, NA discontinuation has become a powerful tool to achieve control over HBeAg-negative HBV infections. Its significant effect represents a challenge to novel treatment approaches, but it may also serve as their enhancer.

TOX defines the degree of CD8+ T cell dysfunction in distinct phases of chronic HBV infection

OBJECTIVE

Chronic hepatitis B virus (HBV) infection is characterised by HBV-specific CD8+ T cell dysfunction that has been linked to Tcell exhaustion, a distinct differentiation programme associated with persisting antigen recognition. Recently, Thymocyte Selection-Associated High Mobility Group Box (TOX) was identified as master regulator of CD8+ T cell exhaustion. Here, we addressed the role of TOX in HBV-specific CD8+ T cell dysfunction associated with different clinical phases of infection.

DESIGN

We investigated TOX expression in HBV-specific CD8+ T cells from 53 HLA-A*01:01, HLA-A*11:01 and HLA-A*02:01 positive patients from different HBV infection phases and compared it to hepatitis C virus (HCV)-specific, cytomegalovirus (CMV)-specific, Epstein-Barr virus (EBV)-specific and influenza virus (FLU)-specific CD8+ T cells. Phenotypic and functional analyses of virus-specific CD8+ T cells were performed after peptide-loaded tetramer-enrichment and peptide-specific expansion.

RESULTS

Our results show that TOX expression in HBV-specific CD8+ T cells is linked to chronic antigen stimulation, correlates with viral load and is associated with phenotypic and functional characteristics of T-cell exhaustion. In contrast, similar TOX expression in EBV-specific and CMV-specific CD8+ T cells is not linked to T-cell dysfunction suggesting different underlying programmes. TOX expression in HBV-specific CD8+ T cells is also affected by targeted antigens, for example, core versus polymerase. In HBV-specific CD8+ T cells, TOX expression is maintained after spontaneous or therapy-mediated viral control in chronic but not self-limiting acute HBV infection indicating a permanent molecular imprint after chronic but not temporary stimulation.

CONCLUSION

Our data highlight TOX as biomarker specific for dysfunctional virus-specific CD8+ T cells in the context of an actively persisting infection.

Serum ERK1/2 proteins fluctuating with HBV infection report frequency of viral-specific CD8+ T cells and predict IFNα therapeutic effect in chronic hepatitis B patients

Chronic hepatitis B (CHB) is a life-threatening disease caused by HBV infection. Our previous work proved that activation of ERK1/2 and STAT3 signaling was involved in HBV tolerance. We herein investigated clinical significances of serum ERK1/2 and STAT3 proteins in CHB. Results showed that ERK1/2 and STAT3 were fluctuated with natural history of CHB. In addition, STAT3 was found to be positively correlated to the elevation of ALT, AST and GGT, while ERK1 was negatively correlated to decreases of TP and ALB. Also, there was a positive correlation between the anti-HBc antibody and ERK1, ERK2 or STAT3 in HBeAg-negative patients. Strikingly, serum ERK1 and ERK2 could reflect level of HBsAg-specific CD8⁺ T cells. A model composed with baseline ERK1 and ERK2 levels had a high accuracy to predict the effect of IFNα treatment. In conclusion, serum ERK1, ERK2 and STAT3 could serve as novel biomarkers in chronic HBV infections.

Optimized ex vivo stimulation identifies multi-functional HBV-specific T cells in a majority of chronic hepatitis B patients

High antigen burden during chronic hepatitis B (CHB) results in a low frequency HBV-specific T cell response with restricted functionality. However, this observation is based on limited data because low T cell frequencies have hindered effective ex vivo analysis. We adapted the ELISpot assay to overcome this obstacle to measure ex vivo T cell responses in CHB patients. We modified the key variables of cell number and the peptide pulsing method to improve ex vivo detection of HBV-specific T cells. We detected IFN-γ responses in 10/15 vaccinated controls and 20/30 CHB patients, averaging 195 and 84 SFUs/2 × 10⁶ PBMCs respectively. Multi-analyte FluoroSpots improved functional characterization of T cells. We detected IFN-γ responses in all tested vaccinated controls (n = 10) and CHB patients (n = 13). IL-2 responses were detectable in 9/10 controls and 10/13 patients. TNF-α displayed less sensitivity, detectable in only 7/10 controls and 7/13 patients. Antigen-specific analysis demonstrated that IFN-γ responses were dominated by polymerase and core, with weak responses to envelope and X. IL-2 responses were found in 3/5 patients and equally directed towards polymerase and core. While their ex vivo frequency is extremely low, a fraction of HBV-specific T cells are detectable and display multi-functionality ex vivo.

Discovery and Selection of Hepatitis B Virus-Derived T Cell Epitopes for Global Immunotherapy Based on Viral Indispensability, Conservation, and HLA-Binding Strength

Multiple HBV-derived T cell epitopes have been reported, which can be useful in a therapeutic vaccination strategy. However, these epitopes are largely restricted to HLA-A*02, which is not dominantly expressed in populations with high HBV prevalence. Thus, current epitopes are falling short in the development of a global immunotherapeutic approach. Therefore, we aimed to identify novel epitopes for 6 HLA supertypes most prevalent in the infected population. Moreover, established epitopes might not all be equally effective as they can be subject to different levels of immune escape. It is therefore important to identify targets that are crucial in viral replication and conserved in the majority of the infected population. Here, we applied a stringent selection procedure to compose a combined overview of existing and novel HBV-derived T cell epitopes most promising for viral eradication. This set of T cell epitopes now lays the basis for the development of globally effective HBV antigen-specific immunotherapies.

Immunotherapy represents an attractive option for the treatment of chronic hepatitis B virus (HBV) infection. The HBV proteins polymerase (Pol) and HBx are of special interest for antigen-specific immunotherapy because they are essential for viral replication and have been associated with viral control (Pol) or are still expressed upon viral DNA integration (HBx). Here, we scored all currently described HBx- and Pol-derived epitope sequences for viral indispensability and conservation across all HBV genotypes. This yielded 7 HBx-derived and 26 Pol-derived reported epitopes with functional association and high conservation. We subsequently predicted novel HLA-binding peptides for 6 HLA supertypes prevalent in HBV-infected patients. Potential epitopes expected to be the least prone to immune escape were subjected to a state-of-the-art in vitro assay to validate their HLA-binding capacity. Using this method, a total of 13 HLA binders derived from HBx and 33 binders from Pol were identified across HLA types. Subsequently, we demonstrated interferon gamma (IFN-γ) production in response to 5 of the novel HBx-derived binders and 17 of the novel Pol-derived binders. In addition, we validated several infrequently described epitopes. Collectively, these results specify a set of highly potent T cell epitopes that represent a valuable resource for future HBV immunotherapy design.

IMPORTANCE Multiple HBV-derived T cell epitopes have been reported, which can be useful in a therapeutic vaccination strategy. However, these epitopes are largely restricted to HLA-A*02, which is not dominantly expressed in populations with high HBV prevalence. Thus, current epitopes are falling short in the development of a global immunotherapeutic approach. Therefore, we aimed to identify novel epitopes for 6 HLA supertypes most prevalent in the infected population. Moreover, established epitopes might not all be equally effective as they can be subject to different levels of immune escape. It is therefore important to identify targets that are crucial in viral replication and conserved in the majority of the infected population. Here, we applied a stringent selection procedure to compose a combined overview of existing and novel HBV-derived T cell epitopes most promising for viral eradication. This set of T cell epitopes now lays the basis for the development of globally effective HBV antigen-specific immunotherapies.

Emerging tools in the changing landscape of chronic hepatitis B management

Introduction: The availability of a preventative vaccine, interferon, and nucleos(t)ide analogs have provided progress in the control of chronic hepatitis B (CHB). Despite this, it remains a major contributor to global morbidity and mortality. Developments in our understanding of the pathogenesis of CHB and the emergence of new therapies are paving the way, as we move toward HBV cure.Areas covered: We performed bibliographical searches of online databases to review the literature regarding conventional disease phases of CHB. We provide the latest evidence challenging the perception of the natural history of CHB, noting that previously considered quiescent disease phases may not represent benign disease states devoid of progression. We explore the use of potential novel immunological and viral tools which should enhance disease stratification and management decisions in the coming years. Finally, we discuss the timing of treatment and how this could be initiated earlier to improve treatment outcomes, preventing sequelae of chronic infection.Expert opinion: The treatment paradigm in CHB is set to change with multiple novel agents in early phase clinical trials with the aim of a functional cure. An improved understanding of disease pathogenesis and the timing of treatment will be critical to the success of new therapies.

Roadmap to functional cure of chronic hepatitis B: An expert consensus

Hepatitis B virus (HBV) infection continues to be a major public health issue worldwide. HBsAg loss is associated with functional remission and improved long-term outcome, and is considered to be a 'functional cure' (also referred to as clinical or immunologic cure) for chronic hepatitis B. This ideal goal of therapy can be achieved using optimized combination regimens with direct-acting antivirals [eg nucleos(t)ide analogues (NAs)] and immunomodulators [eg pegylated interferon alpha2a (Peg-IFN)] in selected patients with chronic hepatitis B. Among different combination therapies currently available, those with NA lead-in followed by Peg-IFN in virally suppressed patients has been demonstrated to be effective. This review provides an updated overview of the evidence supporting the use of combination therapies and summarizes expert consensus on the roadmap to attain functional cure for chronic hepatitis B patients.

Acetaldehyde suppresses the display of HBV-MHC class I complexes on HBV-expressing hepatocytes

Hepatitis B virus (HBV) infection and alcoholism are major public health problems worldwide, contributing to the development of end-stage liver disease. Alcohol intake affects HBV infection pathogenesis and treatment outcomes. HBV-specific cytotoxic T lymphocytes (CTLs) play an important role in HBV clearance. Many previous studies have focused on alcohol-induced impairments of the immune response. However, it is not clear whether alcohol alters the presentation of HBV peptide-major histocompatibility complex (MHC) class I complexes on infected hepatocytes resulting in escape of its recognition by CTLs. Hence, the focus of this study was to investigate the mechanisms by which ethanol metabolism affects the presentation of CTL epitope on HBV-infected hepatocytes. As demonstrated here, although continuous cell exposure to acetaldehyde-generating system (AGS) increased HBV load in HepG2.2.15 cells, it decreased the expression of HBV core peptide 18-27-human leukocyte antigen-A2complex (CTL epitope) on the cell surface. Moreover, we observed AGS-induced suppression of chymotrypsin- and trypsin-like proteasome activities necessary for peptide processing by proteasome as well as a decline in IFNγ-stimulated immunoproteasome (IPR) function and expression of PA28 activator and immunoproteasome subunits LMP7 and LMP2. Furthermore, IFNγ-induced activation of peptide-loading complex (PLC) components, such as transporter associated with antigen processing (TAP1) and tapasin, were suppressed by AGS. The attenuation of IPR and PLC activation was attributed to AGS-triggered impairment of IFNγ signaling in HepG2.2.15 cells. Collectively, all these downstream events reduced the display of HBV peptide-MHC class I complexes on the hepatocyte surface, which may suppress CTL activation and the recognition of CTL epitopes on HBV-expressing hepatocytes by immune cells, thereby leading to persistence of liver inflammation.NEW & NOTEWORTHY Our study shows that in HBV-expressing HepG2.2.15 cells, acetaldehyde alters HBV peptide processing by suppressing chymotrypsin- and trypsin-like proteasome activities and decreases IFNγ-stimulated immunoproteasome function and expression of PA28 activator and immunoproteasome subunits. It also suppresses IFNγ-induced activation of peptide-loading complex (PLC) components due to impairment of IFNγ signaling via the JAK-STAT1 pathway. These acetaldehyde-induced dysfunctions reduced the display of HBV peptide-MHC class I complexes on the hepatocyte surface, thereby leading to persistence of HBV infection.

Ex vivo Detection and Characterization of Hepatitis B Virus-Specific CD8+ T Cells in Patients Considered Immune Tolerant

In this study, we aimed to detect and characterize ex vivo virus-specific CD8+ T cells in patients with immune-tolerant hepatitis B virus (HBV) infection. We investigated a Korean chronic hepatitis B cohort composed of 15 patients in the immune-tolerant phase, 17 in the immune-active phase, and 13 under antiviral treatment. We performed enzyme-linked immunospot (ELISpot) assays ex vivo and intracellular cytokine staining after in vitro culture. We also performed ex vivo multimer staining assays and examined the expression of programmed death-1 (PD-1) and CD127 in pentamer-positive cells. Ex vivo ELISpot revealed that HBV-specific T cell function was weaker in immune-tolerant patients than in those under antiviral treatment. In vitro culture of peripheral blood mononuclear cells for 10 days revealed that HBV-specific CD8+ T cells produced interferon-γ in some immune-tolerant patients. We detected HBV-specific CD8+ T cells ex vivo (using the HBV core18-27 pentamer) in patients from all three groups. The PD-1+ subset of pentamer+ CD8+ T cells was smaller ex vivo in the immune-tolerant phase than in the immune-active phase or under antiviral treatment. Interestingly, the proportion of PD-1+ CD8+ T cells in HBV-specific CD8+ T cells correlated with patient age when all enrolled patients were analyzed. Overall, HBV-specific CD8+ T cells are present in patients considered as immune-tolerant, although their ex vivo functionality is significantly weaker than that in patients under antiviral treatment (P < 0.05). Despite the high viral load, the proportion of PD-1 expression in HBV-specific CD8+ T cells is lower in the immune-tolerant phase than in other phases. Our results indicate appropriate stimulation may enhance the effector function of HBV-specific CD8+ T cells in patients considered as being in the immune-tolerant phase.