Interferon-γ and Tumor Necrosis Factor-α Produced by T Cells Reduce the HBV Persistence Form, cccDNA, Without Cytolysis

Immune suppression in chronic hepatitis B infection associated liver disease: A review

Hepatitis B virus (HBV) infection is one the leading risk factors for chronic hepatitis, liver fibrosis, cirrhosis and hepatocellular cancer (HCC), which are a major global health problem. A large number of clinical studies have shown that chronic HBV persistent infection causes the dysfunction of innate and adaptive immune response involving monocytes/macrophages, dendritic cells, natural killer (NK) cells, T cells. Among these immune cells, cell subsets with suppressive features have been recognized such as myeloid derived suppressive cells(MDSC), NK-reg, T-reg, which represent a critical regulatory system during liver fibrogenesis or tumourigenesis. However, the mechanisms that link HBV-induced immune dysfunction and HBV-related liver diseases are not understood. In this review we summarize the recent studies on innate and adaptive immune cell dysfunction in chronic HBV infection, liver fibrosis, cirrhosis, and HCC, and further discuss the potential mechanism of HBV-induced immunosuppressive cascade in HBV infection and consequences. It is hoped that this article will help ongoing research about the pathogenesis of HBV-related hepatic fibrosis and HBV-related HCC.

LncRNA PCNAP1 modulates hepatitis B virus replication and enhances tumor growth of liver cancer

Rationale: Hepatitis B virus (HBV) is a major risk factor for liver cancer, in which HBV covalently closed circular DNA (cccDNA) plays crucial roles. However, the effect of pseudogene-derived long noncoding RNAs (lncRNAs) acting as functional regulators of their ancestral gene expression on HBV replication and hepatocellular carcinoma (HCC) remains unclear. In this study, we speculated that the pseudogene-derived lncRNA PCNAP1 and its ancestor PCNA might modulate HBV replication and promote hepatocarcinogenesis.

Methods: We investigated the roles of lncRNA PCNAP1 in contribution of HBV replication through modulating miR-154/PCNA/HBV cccDNA signaling in hepatocarcinogenesis by using CRISPR/Cas9, Southern blot analysis, confocal assays, et al. in primary human hepatocytes (PHH), HepaRG cells, HepG2-NTCP cells, hepatoma carcinoma cells, human liver-chimeric mice model, transgenetic mice model, in vitro tumorigenicity and clinical patients.

Results: Interestingly, the expression levels of PCNAP1 and PCNA were significantly elevated in the liver of HBV-infectious human liver-chimeric mice. Clinically, the mRNA levels of PCNAP1 and PCNA were increased in the liver of HBV-positive/HBV cccDNA-positive HCC patients. Mechanistically, PCNA interacted with HBV cccDNA in a HBc-dependent manner. PCNAP1 enhanced PCNA through sponging miR-154 targeting PCNA mRNA 3′UTR. Functionally, PCNAP1 or PCNA remarkably enhanced HBV replication and accelerated the growth of HCC in vitro and in vivo.

Conclusion: We conclude that lncRNA PCNAP1 enhances the HBV replication through modulating miR-154/PCNA/HBV cccDNA signaling and the PCNAP1/PCNA signaling drives the hepatocarcinogenesis. Our finding provides new insights into the mechanism by which lncRNA PCNAP1 enhances HBV replication and hepatocarcinogenesis.

An interferon-like small chemical compound CDM-3008 suppresses hepatitis B virus through induction of interferon-stimulated genes

Oral administration of nucleotide analogues and injection of interferon-α (IFNα) are used to achieve immediate suppression in replication of hepatitis B virus (HBV). Nucleotide analogs and IFNα inhibit viral polymerase activity and cause long-term eradication of the virus at least in part through removing covalently closed circular DNA (cccDNA) via induction of the APOBEC3 deaminases family of molecules, respectively. This study aimed to explore whether the orally administrable low molecular weight agent CDM-3008 (RO8191), which mimics IFNα through the binding to IFNα/β receptor 2 (IFNAR2) and the activation of the JAK/STAT pathway, can suppress HBV replication and reduce cccDNA levels. In primary cultured human hepatocytes, HBV DNA levels were decreased after CDM-3008-treatment in a dose-dependent manner with a half-maximal inhibitory concentration (IC₅₀) value of 0.1 μM, and this was accompanied by significant reductions in cellular cccDNA levels, both HBeAg and HBsAg levels in the cell culture medium. Using a microarray we comprehensively analyzed and compared changes in gene (mRNA) expression in CDM-3008- and IFNα-treated primary cultured human hepatocytes. As reported previously, CDM-3008 mimicked the induction of genes that participate in the interferon signaling pathway. OAS1 and ISG20 mRNA expression was similarly enhanced by both CDM-3008 and IFNα. Thus, CDM-3008 could suppress pgRNA expression to show anti-HBV activity. APOBEC3F and 3G mRNA expression was also induced by CDM-3008 and IFNα treatments, suggesting that cccDNA could be degraded through induced APOBEC3 family proteins. We identified the genes whose expression was specifically enhanced in CDM-3008-treated cells compared to IFNα-treated cells. The expression of SOCS1, SOCS2, SOCS3, and CISH, which inhibit STAT activation, was enhanced in CDM-3008-treated cells suggesting that a feedback inhibition of the JAK/STAT pathway was enhanced in CDM-3008-treated cells compared to IFNα-treated cells. In addition, CDM-3008 showed an additive effect with a clinically-used nucleoside entecavir on inhibition of HBV replication. In summary, CDM-3008 showed anti-HBV activity through activation of the JAK/STAT pathway, inducing the expression of interferon-stimulated genes (ISGs), with greater feedback inhibition than IFNα.

Stem Cell-Derived Hepatocyte-Like Cells as Model for Viral Hepatitis Research

Viral hepatitis, the leading cause of liver diseases worldwide, is induced upon infection with hepatotropic viruses, including hepatitis A, B, C, D, and E virus. Due to their obligate intracellular lifestyles, culture systems for efficient viral replication are vital. Although basic and translational research on viral hepatitis has been performed for many years, conventional hepatocellular culture systems are not optimal. These studies have greatly benefited from recent efforts on improving cell culture models for virus replication and infection studies. Here we summarize the use of human stem cell-derived hepatocyte-like cells for hepatotropic virus infection studies, including the dissection of virus-host interactions and virus-induced pathogenesis as well as the identification and validation of novel antiviral agents.

Virological Basis for the Cure of Chronic Hepatitis B

Hepatitis B virus (HBV) has infected one-third of world population, and 240 million people are chronic carriers, to whom a curative therapy is still not available. Similar to other viruses, persistent HBV infection relies on the virus to exploit host cell functions to support its replication and efficiently evade host innate and adaptive antiviral immunity. Understanding HBV replication and concomitant host cell interactions is thus instrumental for development of therapeutics to disrupt the virus-host interactions critical for its persistence and cure chronic hepatitis B. Although the currently available cell culture systems of HBV infection are refractory to genome-wide high throughput screening of key host cellular factors essential for and/or regulating HBV replication, classic one-gene (or pathway)-at-a-time studies in the last several decades have already revealed many aspects of HBV-host interactions. An overview of the landscape of HBV-hepatocyte interaction indicates that, in addition to more tightly suppressing viral replication by directly targeting viral proteins, disruption of key viral-host cell interactions to eliminate or inactivate the covalently closed circular (ccc) DNA, the most stable HBV replication intermediate that exists as an episomal minichromosome in the nucleus of infected hepatocyte, is essential to achieve a functional cure of chronic hepatitis B. Moreover, therapeutic targeting of integrated HBV DNA and their transcripts may also be required to induce hepatitis B virus surface antigen (HBsAg) seroclearance and prevent liver carcinogenesis.

T cell receptor grafting allows virological control of Hepatitis B virus infection

T cell therapy is a promising means to treat chronic HBV infection and HBV-associated hepatocellular carcinoma. T cells engineered to express an HBV-specific T cell receptor (TCR) may achieve cure of HBV infection upon adoptive transfer. We investigated the therapeutic potential and safety of T cells stably expressing high affinity HBV envelope- or core-specific TCRs recognizing European and Asian HLA-A2 subtypes. Both CD8+ and CD4+ T cells from healthy donors and from chronic hepatitis B patients became polyfunctional effector cells when grafted with HBV-specific TCRs and eliminated HBV from infected HepG2-NTCP cell cultures. A single transfer of TCR-grafted T cells into HBV-infected, humanized mice controlled HBV infection and virological markers declined 4-5 log or below detection limit. When - as in a typical clinical setting - only a minority of hepatocytes were infected, engineered T cells specifically cleared infected hepatocytes without damaging non-infected cells. Cell death was compensated by hepatocyte proliferation and alanine amino transferase levels peaking at day 5 to 7 normalized again thereafter. Co-treatment with the entry inhibitor Myrcludex B ensured long-term control of HBV infection. Thus, T cells stably transduced with highly functional TCRs have the potential to mediate clearance of HBV-infected cells causing limited liver injury.

Immune response pattern varies with the natural history of chronic hepatitis B

BACKGROUND

Chronic hepatitis B is a highly heterogeneous disease that can be divided into four phases: Immune tolerant (IT), immune active (IA), inactive carrier (IC) and hepatitis B envelope antigen (HBeAg)-negative hepatitis (ENEG).

AIM

To investigate the immune status of natural killer (NK) and T cells in different phases of chronic hepatitis B.

METHODS

The frequency, phenotype and function of circulating NK cells, as well as nonantigen-specific and hepatitis B virus (HBV)-specific T cell responses were detected by flow cytometry in healthy and HBV-infected subjects.

RESULTS

The ability of NK cells to produce IFN-γ was markedly attenuated in HBV-infected patients overall but was less compromised in IC patients. Patients in the IT and IA phases also displayed significantly lower TNF-α production compared to healthy subjects. NK cells were phenotypically activated in the IA and ENEG phases, as evidenced by the upregulation of NKp44 in CD56^bright NK cells and CD69 in CD56^dim NK cells. Furthermore, global T-cells from the ENEG phase displayed a proinflammatory cytokine profile with upregulated IFN-γ and TNF-α expression, while this profile was suppressed in IT and IA patients. Finally, core and S antigen-specific T cell responses were significantly stronger after in vitro expansion in the IC phase compared to other phases.

CONCLUSION

Our findings demonstrate the changes in immune response pattern during the natural history of HBV infection. Both NK and T cells are functionally impaired in the IT and IA phases. With the spontaneous clearance of HBeAg and hepatitis B surface antigen decline, NK cell cytokine production and HBV-specific T responses are partially restored in IC phase, and the ENEG phase is dominated by nonantigen-specific T cell responses.

Hepatitis B Surface Antigen Activates Unfolded Protein Response in Forming Ground Glass Hepatocytes of Chronic Hepatitis B

Ground glass hepatocytes (GGHs), a histological hallmark of chronic hepatitis B virus (HBV) infection, contain excessive hepatitis surface antigen (HBsAg) in the endoplasmic reticulum (ER), which is linked to unfolded protein response (UPR). The mechanism by which HBV activates UPR has not been fully defined. To investigate this, HepG2-NTCP cells and primary human hepatocytes (PHHs) were either infected with HBV or transduced with adenoviral vectors expressing replication-competent HBV genome or individual HBV genes. UPR markers were evaluated by qPCR, Western blotting, and immunofluorescence. Apoptosis and cell viability were measured by Caspase-3/7 and ATPlite assay respectively. We found that UPR markers were induced by the overexpression of HBsAg in HepG2-NTCP cells and PHHs. Elevation of UPR-induced genes showed a dose-dependent correlation with HBsAg levels. In HBV-infected livers, GGHs also demonstrated excessive accumulation of HBsAg associated with increased BIP/GRP78 staining, a marker of UPR. Prolonged activation of UPR by HBsAg overexpression induced signs of apoptosis. Overexpression of HBsAg can induce ER stress through protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathway in vitro, and may be linked to the appearance of GGHs. The activation of UPR by HBsAg may sensitize hepatocytes to cell death and result in possible subsequent cellular changes leading to a premalignant phenotype.

siRNA nanotherapeutics: a promising strategy for anti‐HBV therapy

Chronic hepatitis B (CHB) is the most common cause of hepatocellular carcinoma (HCC) and liver cirrhosis worldwide. In spite of the numerous advances in the treatment of CHB, drugs and vaccines have failed because of many factors like complexity, resistance, toxicity, and heavy cost. New RNA interference (RNAi)‐based technologies have developed innovative strategies to target Achilles' heel of the several hazardous diseases involving cancer, some genetic disease, autoimmune illnesses, and viral disorders particularly hepatitis B virus (HBV) infections. Naked siRNA delivery has serious challenges including failure to cross the cell membrane, susceptibility to the enzymatic digestion, and excretion by renal filtration, which ideally can be addressed by nanoparticle‐mediated delivery systems. cccDNA formation is a significant problem in obtaining HBV infections complete cure because of strength, durability, and lack of proper immune response. Nano‐siRNA drugs have a great potential to address this problem by silencing specific genes which are involved in cccDNA formation. In this article, the authors describe siRNA nanocarrier‐mediated delivery systems as a promising new strategy for HBV infections therapy. Simultaneously, the authors completely represent the clinical trials which use these strategies for treatment of the HBV infections.

A global scientific strategy to cure hepatitis B

Chronic hepatitis B virus (HBV) infection is a global public health challenge on the same scale as tuberculosis, HIV, and malaria. The International Coalition to Eliminate HBV (ICE-HBV) is a coalition of experts dedicated to accelerating the discovery of a cure for chronic hepatitis B. Following extensive consultation with more than 50 scientists from across the globe, as well as key stakeholders including people affected by HBV, we have identified gaps in our current knowledge and new strategies and tools that are required to achieve HBV cure. We believe that research must focus on the discovery of interventional strategies that will permanently reduce the number of productively infected cells or permanently silence the covalently closed circular DNA in those cells, and that will stimulate HBV-specific host immune responses which mimic spontaneous resolution of HBV infection. There is also a pressing need for the establishment of repositories of standardised HBV reagents and protocols that can be accessed by all HBV researchers throughout the world. The HBV cure research agenda outlined in this position paper will contribute markedly to the goal of eliminating HBV infection worldwide.

Smoking and Hepatitis B Virus-Related Hepatocellular Carcinoma Risk: The Mediating Roles of Viral Load and Alanine Aminotransferase

Smoking interacts with hepatitis B virus (HBV) to increase the risk of hepatocellular carcinoma (HCC), which might be explained by its role in antiviral immunity. We evaluated the potential mediating role of viral load and/or alanine aminotransferase (ALT) in the relation of smoking with HBV-associated HCC risk. Using multiple mediation analyses to analyze data from 209 HCC cases and 1,256 controls nested within a cohort of 4,841 male HBV carriers, we found that the effect of smoking on the risk of subsequent HCC was substantially mediated through viral load (percent mediated, 31.7%; P = 0.0054), and a significant mediation effect by both viral load and ALT was also evidenced. Among the 1,143 subjects with repeated measures of viral load and ALT over periods of up to 16 years, we further observed that a higher number of pack-years of smoking was associated with higher viral load, maintenance of a high viral load (>4.39 log copies/mL), more severe hepatotoxicity grade, and increased likelihood of ALT ≥80 U/L (odds ratio, 3.14; 95% confidence interval, 1.03-9.64; odds ratio, 6.06; 95% confidence interval, 1.10-33.25, respectively, for 10-19 and ≥20 pack-years versus nonsmokers) during follow-up. Furthermore, plasma interferon-γ levels were reduced in smokers compared with nonsmokers (interferon-γ-positive rate, 14.9% versus 28.7%; P < 0.0001) at baseline. Smoking was also associated with a reduced natural killer (NK) cell frequency in peripheral blood, characterized by reduced NK function through a systems immunology approach, after long-term follow-up in a subsample (n = 171). The combination of smoking and reduced NK cell frequency further increased viral load and the likelihood of ALT ≥80 U/L. Conclusion: The data highlight a role of smoking in HBV viral load, underlining the importance of smoking prevention and cessation in hepatitis B management.

The balance of type 1 and type 2 immune responses in the contexts of hepatitis B infection and hepatitis D infection

BACKGROUND AND AIM

Hepatitis delta virus (HDV) infection is the most rapidly progressive chronic viral hepatitis. Little is understood about the immune responses to HDV. This study aims to characterize the systemic immune environments of hepatitis B virus (HBV) and HDV patients at various disease stages.

METHODS

A total of 129 subjects were evaluated: 53 HBV, 43 HDV, and 33 healthy controls. HBV and HDV subjects were categorized by aspartate aminotransferase to platelet ratio index (APRI) into mild (APRI < 0.5), moderate, and severe (APRI > 1.0). Serum cytokines and immune markers were assessed at a single treatment-naïve time-point.

RESULTS

Type 1 cytokines are elevated in both HBV and HDV. Both groups show higher tumor necrosis factor-α (TNF-α), interleukin (IL)-12p40, and C-X-C motif chemokine ligand 9 when compared with controls (all P < 0.05). However, only HBV group displayed elevated γ-interferon compared with controls. Type 2 cytokines are elevated in HBV. HBV group shows higher IL-4, IL-13, and C-C motif chemokine ligand (CCL) 26 compared with healthy controls and HDV. Chemokines CCL2 and CCL13 are lower in HDV. When assessing ratios, HDV displays higher γ-interferon/IL-4, TNF-α/IL-4, and TNF-α/IL-13 ratios than HBV and controls.

CONCLUSION

Hepatitis B virus and HDV subjects show similarly elevated type 1 cytokines. HDV subjects display relatively lower type 2 cytokines. These differences in the systemic immune environments, particularly the predominance of type 1 responses, may contribute to the comparatively rapid progression of HDV disease. Characterization of the imbalance in type 1 and type 2 immunity unique HDV has the potential to provide immunological insights for designing therapeutic targets in HDV-associated disease progression.

Evaluation of a Fully Human, Hepatitis B Virus-Specific Chimeric Antigen Receptor in an Immunocompetent Mouse Model

Chimeric antigen receptor (CAR) T cell therapy is a promising novel therapeutic approach for cancer but also for chronic infection. We have developed a fully human, second-generation CAR directed against the envelope protein of hepatitis B virus on the surface of infected cells (S-CAR). The S-CAR contains a human B cell-derived single-chain antibody fragment and human immunoglobulin G (IgG) spacer, CD28- and CD3-signaling domains that may be immunogenic in mice. Because immunosuppression will worsen the clinical course of chronic hepatitis B, we aimed at developing a preclinical mouse model that is immunocompetent and mimics chronic hepatitis B but nevertheless allows evaluating efficacy and safety of a fully human CAR. The S-CAR grafted on T cells triggered antibody responses in immunocompetent animals, and a co-expressed human-derived safeguard, the truncated epidermal growth factor receptor (EGFRt), even induced B and T cell responses, both limiting the survival of S-CAR-grafted T cells. Total body irradiation and transfer of T cells expressing an analogous, signaling-deficient S-CAR decoy and the safeguard induced immune tolerance toward the human-derived structures. S-CAR T cells transferred after immune recovery persisted and showed long-lasting antiviral effector function. The approach we describe herein will enable preclinical studies of efficacy and safety of fully human CARs in the context of a functional immune system.

B-Cell Lymphoma 6 (BCL6) Is a Host Restriction Factor That Can Suppress HBV Gene Expression and Modulate Immune Responses

Hepatitis B virus (HBV) infection causes acute and chronic liver inflammation. Recent studies have demonstrated that some viral antigens can suppress host innate and adaptive immunity, and thus lead to HBV liver persistency. However, the cellular factors that can help host cells to clear HBV during acute infection remain largely unknown. Here, we used HBV-cleared and HBV-persistent mouse models to seek for cellular factors that might participate in HBV clearance. HBV replicon DNA was delivered into the mouse liver by hydrodynamic injection. RNA-Seq analysis was conducted to identify immune-related genes that were differentially expressed in HBV-persistent and HBV-cleared mouse models. A cellular factor, B cell lymphoma 6 (BCL6), was found to be significantly upregulated in the liver of HBV-cleared mice upon HBV clearance. Co-expression of BCL6 and a persistent HBV clone rendered the clone largely cleared, implicating an important role of BCL6 in controlling HBV clearance. Mechanistic studies demonstrated that BCL6 functioned as a repressor, binding to and suppressing the activities of the four HBV promoters. Correspondingly, BCL6 expression significantly reduced the levels of HBV viral RNA, DNA, and proteins. BCL6 expression could be stimulated by inflammatory cytokines such as TNF-α; the BCL6 in turn synergized TNF-α signaling to produce large amounts of CXCL9 and CXCL10, leading to increased infiltrating immune cells and elevated cytokine levels in the liver. Thus, positive feedback loops on BCL6 expression and immune responses could be produced. Together, our results demonstrate that BCL6 is a novel host restriction factor that exerts both anti-HBV and immunomodulatory activities. Induction of BCL6 in the liver may ultimately assist host immune responses to clear HBV.

Targeting Innate and Adaptive Immune Responses to Cure Chronic HBV Infection

Fewer than 1% of chronic hepatitis B virus infections per year are cured with antiviral treatment. This creates a need for long-term treatment, which poses challenges for patients and health systems. Because cure is accompanied by recovery of antiviral immunity, a combination of direct-acting antiviral agents and immunotherapy are likely to be required. Extensive efforts have been made to identify determinants of the failed immune response to hepatitis B virus in patients with chronic infection. We review mechanisms of immune dysfunction in patients with chronic hepatitis B virus infection, immunotherapy strategies in development, and the challenges associated with successful implementation of immunotherapy.

Development of Direct-acting Antiviral and Host-targeting Agents for Treatment of Hepatitis B Virus Infection

Hepatitis B virus (HBV) infection affects approximately 300 million people worldwide. Although antiviral therapies have improved the long-term outcomes, patients often require life-long treatment and there is no cure for HBV infection. New technologies can help us learn more about the pathogenesis of HBV infection and develop therapeutic agents to reduce its burden. We review recent advances in development of direct-acting antiviral and host-targeting agents, some of which have entered clinical trials. We also discuss strategies for unbiased high-throughput screens to identify compounds that inhibit HBV and for repurposing existing drugs.

Plasma CXCL13 is a predictive factor for HBsAg loss and clinical relapse after discontinuation of nucleos(t)ide analogue treatment

In this study, we investigated whether plasma cytokine/chemokine levels could predict HBsAg loss or clinical relapse (CR) after stopping nucleos(t)ides analogue (NA) treatment. Theplasma cytokines/chemokines levels were measured at 0, 4, 8, 12, 24 and 48 weeks after NA discontinuation by using the enzyme-linked immunoassay (ELISA) kit. Cox regression analysis revealed that CXCL13 level at the end of treatment (EOT) was an independent predictor for CR (HR 0.26, p < 0.001) and HBsAg loss (HR 3.01, p = 0.008) after treatment cessation. Among the patients with EOT CXCL13 level < 80 pg/ml, the cumulative incidences of CR and HBsAg loss were 65% and 0% at 4 years, respectively. As for the patients with EOT CXCL13 level ≥ 1000 pg/ml, 47.5% cases had HBsAg loss. Our study showed that EOT CXCL13 level was associated with off-treatment response, which may be used to guide cessation of NA treatment in clinical practice.

CD56bright natural killer cells induce HBsAg reduction via cytolysis and cccDNA decay in long-term entecavir-treated patients switching to peginterferon alfa-2a

HBV surface antigen (HBsAg) reduction is well observed in chronic hepatitis B (CHB) patients treated with pegylated interferon alpha-2a (PegIFNα). However, the mechanism of HBsAg suppression has not been fully elucidated. Twenty-seven of 55 entecavir-treated CHB e antigen positive patients were switched to PegIFNα treatment (Group A) whereas 28 patients continued entecavir treatment (Group B). The percentage or absolute number of CD56^bright /CD56^dim NK cells, expression of receptors and cytokines were evaluated by flow cytometry for 48 weeks and correlated with treatment efficacy. In vitro, purified NK cells were co-cultured with HepAD38 cells for measurement of HBsAg, apoptosis and covalently closed circular DNA (cccDNA). In association with a reduction of HBsAg, the percentage and absolute number of CD56^bright NK cells was significantly elevated in patients in group A, especially in Virologic Responders (VRs, HBsAg decreased). Furthermore, the percentage of NKp30⁺ , NKp46⁺ , TRAIL⁺ , TNF-α⁺ and IFNγ⁺ CD56^bright NK cells were significantly expanded in Group A, which were positively correlated with the decline of HBsAg at week 48. In vitro, peripheral NK cells from Group A induced a decline of HBsAg in comparison with NK cells from Group B which was significantly inhibited by anti-TRAIL, anti-TNF-α and anti-IFNγ antibodies. Furthermore, apoptosis of HepAD38 cells and levels of cccDNA, were significantly reduced by TRAIL⁺ and TNF-α⁺ /IFNγ⁺ NK cells from Group A, respectively. A functional restoration of CD56^bright NK cells in entecavir-treated patients who were switched to PegIFNα contributes to HBsAg and cccDNA clearance through TRAIL-induced cytolysis and TNF-α/IFNγ-mediated noncytolytic pathways.

Clinical Implications of Hepatitis B Virus RNA and Covalently Closed Circular DNA in Monitoring Patients with Chronic Hepatitis B Today with a Gaze into the Future: The Field Is Unprepared for a Sterilizing Cure

. Chronic hepatitis B virus (HBV) infection has long remained a critical global health issue. Covalently closed circular DNA (cccDNA) is a persistent form of the HBV genome that maintains HBV chronicity. Decades of extensive research resulted in the two therapeutic options currently available: nucleot(s)ide analogs and interferon (IFN) therapy. A plethora of reliable markers to monitor HBV patients has been established, including the recently discovered encapsidated pregenomic RNA in serum, which can be used to determine treatment end-points and to predict the susceptibility of patients to IFN. Additionally, HBV RNA splice variants and cccDNA and its epigenetic modifications are associated with the clinical course and risks of hepatocellular carcinoma (HCC) and liver fibrosis. However, new antivirals, including CRISPR/Cas9, APOBEC-mediated degradation of cccDNA, and T-cell therapies aim at completely eliminating HBV, and it is clear that the diagnostic arsenal for defining the long-awaited sterilizing cure is missing. In this review, we discuss the currently available tools for detecting and measuring HBV RNAs and cccDNA, as well as the state-of-the-art in clinical implications of these markers, and debate needs and goals within the context of the sterilizing cure that is soon to come.

Direct Antiviral Mechanisms of Interferon-Gamma

Interferon-gamma (IFNG) is a pleiotropic cytokine that modulates both innate and adaptive immune networks; it is the most potent activator of macrophages and a signature cytokine of activated T lymphocytes. Though IFNG is now appreciated to have a multitude of roles in immune modulation and broad-spectrum pathogen defense, it was originally discovered, and named, as a secretory factor that interferes with viral replication. In contrast to the prototypical type I interferons produced by any cells upon viral infection, only specific subsets of immune cells can produce IFNG upon infection or stimulation with antigen or mitogen. Still, virtually all cells can respond to both types of interferons. This makes IFNG a versatile anti-microbial cytokine and also gives it a unique position in the antiviral defense system. The goal of this review is to highlight the direct antiviral mechanisms of IFNG, thereby clarifying its antiviral function in the effective control of viral infections.

Host functions used by hepatitis B virus to complete its life cycle: Implications for developing host-targeting agents to treat chronic hepatitis B

Similar to other mammalian viruses, the life cycle of hepatitis B virus (HBV) is heavily dependent upon and regulated by cellular (host) functions. These cellular functions can be generally placed in to two categories: (a) intrinsic host restriction factors and innate defenses, which must be evaded or repressed by the virus; and (b) gene products that provide functions necessary for the virus to complete its life cycle. Some of these functions may apply to all viruses, but some may be specific to HBV. In certain cases, the virus may depend upon the host function much more than does the host itself. Knowing which host functions regulate the different steps of a virus' life cycle, can lead to new antiviral targets and help in developing novel treatment strategies, in addition to improving a fundamental understanding of viral pathogenesis. Therefore, in this review we will discuss known host factors which influence key steps of HBV life cycle, and further elucidate therapeutic interventions targeting host-HBV interactions.

Circulating and intrahepatic antiviral B cells are defective in hepatitis B

B cells are increasingly recognized as playing an important role in the ongoing control of hepatitis B virus (HBV). The development of antibodies against the viral surface antigen (HBV surface antigen [HBsAgs]) constitutes the hallmark of resolution of acute infection and is a therapeutic goal for functional cure of chronic HBV (CHB). We characterized B cells directly ex vivo from the blood and liver of patients with CHB to investigate constraints on their antiviral potential. Unexpectedly, we found that HBsAg-specific B cells persisted in the blood and liver of many patients with CHB and were enriched for T-bet, a signature of antiviral potential in B cells. However, purified, differentiated HBsAg-specific B cells from patients with CHB had defective antibody production, consistent with undetectable anti-HBs antibodies in vivo. HBsAg-specific and global B cells had an accumulation of CD21-CD27- atypical memory B cells (atMBC) with high expression of inhibitory receptors, including PD-1. These atMBC demonstrated altered signaling, homing, differentiation into antibody-producing cells, survival, and antiviral/proinflammatory cytokine production that could be partially rescued by PD-1 blockade. Analysis of B cells within healthy and HBV-infected livers implicated the combination of this tolerogenic niche and HBV infection in driving PD-1hiatMBC and impairing B cell immunity.

Hepatitis B virus-persistent infection and innate immunity defect: Cell-related or virus-related?

The outcomes of hepatitis B virus (HBV) infection are closely related to the age at which infection was acquired. Infection acquired in adult life tends to be self-limited, in contrast to perinatal acquirement, for which chronic persistence of the HBV is a general outcome. Innate immunity plays an indispensable role in early virus infection, facilitating virus clearance. However, it has been reported that HBV is under-recognized and poorly eliminated by the innate immune system in the early stages of infection, possibly explaining the long-lasting persistence of viremia afterwards. Furthermore, due to the existence of covalently closed circular DNA, chronic HBV clearance is very difficult, even when patients are given interferon-α and nucleotide/nucleoside analogs for antiviral therapy. The mechanism by which HBV evades innate immune recognition and establishes persistent infection remains a subject of debate. Besides, some researchers are becoming more interested in how to eradicate chronic HBV infection by restoring or boosting innate immunity. This review aimed to summarize the current knowledge on how intrahepatocyte signaling pathways and innate immune cells act after the onset of HBV infection and how these actions are related to the persistence of HBV. We anticipate the insights presented herein to be helpful for future development of novel immune therapeutic strategies to fight HBV infection.

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

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

Hepatitis B virus-specific T cell responses after stopping nucleos(t)ide analogue therapy in HBeAg-negative chronic hepatitis B

BACKGROUND & AIMS

Treatment with nucleos(t)ide analogues (NA) leads to hepatitis B virus (HBV) DNA suppression in most patients with chronic hepatitis B (CHB), but HBV surface antigen (HBsAg) loss rates are low. Upon NA discontinuation, HBV DNA can return rapidly with ensuing alanine aminotransferase flares and induction of cytokines. Several studies reported higher HBsAg loss rates after stopping therapy, but at present it is unclear if cell-mediated immune responses are altered after treatment discontinuation. The aim of this study was to characterise T cell responses during the early phase of virological relapse, following discontinuation of NA therapy in HBeAg-negative patients.

METHODS

A total of 15 HBeAg-negative patients with CHB on long-term NA treatment were included in a prospective study and subjected to structured NA discontinuation. T cell responses were studied at the end of NA therapy and 4, 8 and 12 weeks thereafter.

RESULTS

The T cell phenotype of patients with CHB on long-term NA therapy was markedly different compared to healthy individuals, but was only slightly altered after discontinuation of therapy. T cells from patients with HBsAg loss expressed low levels of KLRG1 and PD-1 at all time-points and high levels of Ki-67 and CD38 at week 12 after treatment cessation. In vitro peptide stimulated HBV-specific T cell responses were increased in several patients after NA cessation. Blocking of PD-L1 further enhanced HBV-specific T cell responses, especially after discontinuation of therapy.

CONCLUSION

Relapse of active HBV replication after stopping therapy may trigger an immunological environment that enhances the responsiveness of HBV-specific T cells in vitro. Together with other immune interventions, this approach might be of interest for the development of novel therapeutic options to induce HBsAg loss in CHB.

LAY SUMMARY

Relapse of hepatitis B virus replication after discontinuation of nucleos(t)ide analogue therapy in certain patients with chronic hepatitis B may alter the phenotype of T cells and enhance the responsiveness of hepatitis B virus-specific T cells to in vitro peptide stimulation. Blocking PD-L1 can further augment these hepatitis B virus-specific T cell responses. Interestingly, T cells of patients that subsequently achieve hepatitis B surface antigen loss are less exhausted at all time-points after stopping treatment and display a higher proliferative capacity 12-weeks after treatment discontinuation. These findings contribute to the understanding of the immunological events that occur during discontinuation of nucleos(t)ide analogue therapy.

Interferon signaling during Hepatitis B Virus (HBV) infection and HBV-associated hepatocellular carcinoma

Chronic Hepatitis B Virus (HBV) infection is linked to hepatocellular carcinoma (HCC) pathogenesis. The World Health Organization estimates that globally 257 million people are chronic HBV carriers at risk of developing liver cancer. Current therapies for prevention and treatment of HCC are inadequate. Although interferon-based treatment strategies hold great promise for combating chronic infection and HCC, many patients do not respond to the IFN-based drugs for reasons not completely understood. Interferon signaling plays key roles in activation of innate and adaptive immunity. However, HBV has evolved various mechanisms to suppress IFN signaling. In this review, we present the basics about HBV infection and interferon signaling. Next, we discuss mechanisms through which HBV downregulates the function -activity and transcription- of the transcription factor STAT1 during acute and chronic infection. STAT1 is activated in response to all types (I/II/III) of interferon signaling and is essential in mediating all types (I/II/III) of interferon responses. Lastly, we discuss emerging evidence from different human cancers linking loss of interferon signaling to aggressive cancer and cancer stem cells. Whether the same occurs during HBV-associated hepatocarcinogenesis is discussed and currently under investigation.

Intracellular interleukin-32γ mediates antiviral activity of cytokines against hepatitis B virus

Cytokines are involved in early host defense against pathogen infections. In particular, tumor necrosis factor (TNF) and interferon-gamma (IFN-γ) have critical functions in non-cytopathic elimination of hepatitis B virus (HBV) in hepatocytes. However, the molecular mechanisms and mediator molecules are largely unknown. Here we show that interleukin-32 (IL-32) is induced by TNF and IFN-γ in hepatocytes, and inhibits the replication of HBV by acting intracellularly to suppress HBV transcription and replication. The gamma isoform of IL-32 (IL-32γ) inhibits viral enhancer activities by downregulating liver-enriched transcription factors. Our data are validated in both an in vivo HBV mouse model and primary human hepatocytes. This study thus suggests that IL-32γ functions as intracellular effector in hepatocytes for suppressing HBV replication to implicate a possible mechanism of non-cytopathic viral clearance.

Cytokines such as TNF and IFN-γ are important for immunity against hepatitis B virus (HBV). Here the authors show that interleukin-32 gamma (IL-32γ) acts downstream of TNF and IFN-γ as an intracellular effector, and that IL-32γ negatively regulates host factors contributing to HBV transcription to promote HBV clearance.

Regulation of Cytosolic Sulfotransferases in Models of Human Hepatocyte Development

Cytosolic sulfotransferases (SULTs) are expressed during early life and therefore metabolize endogenous and xenobiotic chemicals during development. Little is currently known about the regulation of individual SULTs in the developing human liver. We characterized SULT expression in primary cultures of human fetal hepatocytes and the HepaRG model of liver cell differentiation. SULT1A1 (transcript variants 1-4), SULT1C2, SULT1C4, SULT1E1, and SULT2A1 were the most abundant transcripts in human fetal hepatocytes. In HepaRG cells, SULT1B1, SULT1C2/3/4, and SULT1E1 mRNA levels increased during the transition from proliferation to confluency and then decreased as the cells underwent further differentiation. By contrast, SULT2A1 mRNA levels increased during differentiation, whereas SULT1A1 and SULT2B1 mRNA levels remained relatively constant. The temporal patterns of SULT1C2, SULT1E1, and SULT2A1 protein content were consistent with those observed at the mRNA level. To identify regulators of SULT expression, cultured fetal hepatocytes and HepaRG cells were treated with a panel of lipid- and xenobiotic-sensing receptor activators. The following effects were observed in both fetal hepatocytes and HepaRG cells: 1) liver X receptor activator treatment increased SULT1A1 transcript variant 5 levels; 2) vitamin D receptor activator treatment increased SULT1C2 and SULT2B1 mRNA levels; and 3) farnesoid X receptor activator treatment decreased SULT2A1 expression. Activators of aryl hydrocarbon receptor, constitutive androstane receptor, pregnane X receptor, and peroxisome proliferator-activated receptors produced additional gene-dependent effects on SULT expression in HepaRG cells. These findings suggest that SULT-regulating chemicals have the potential to modulate physiologic processes and susceptibility to xenobiotic stressors in the developing human liver.

Nonlytic Lymphocytes Engineered to Express Virus-Specific T-Cell Receptors Limit HBV Infection by Activating APOBEC3

BACKGROUND & AIMS

Strategies to develop virus-specific T cells against hepatic viral infections have been hindered by safety concerns. We engineered nonlytic human T cells to suppress replication of hepatitis B virus (HBV) and hepatitis C virus (HCV) without overt hepatotoxicity and investigated their antiviral activity.

METHODS

We electroporated resting T cells or T cells activated by anti-CD3 with mRNAs encoding HBV or HCV-specific T-cell receptors (TCRs) to create 2 populations of TCR-reprogrammed T cells. We tested their ability to suppress HBV or HCV replication without lysis in 2-dimensional and 3-dimensional cultures of HepG2.2.15 cells and HBV-infected HepG2-hNTCP cells. We also injected TCR-reprogrammed resting and activated T cells into HBV-infected urokinase-type plasminogen activator/severe combined immunodeficiency disease/interleukin 2γ mice with humanized livers and measured levels of intrahepatic and serological viral parameters and serum alanine aminotransferase. Livers were collected for analysis of gene expression patterns to determine effects of the TCR-reprogrammed T cells.

RESULTS

TCR-reprogrammed resting T cells produced comparable levels of interferon gamma but lower levels of perforin and granzyme than activated T cells and did not lyse HCV- or HBV-infected hepatoma cells. Although T-cell secretion of interferon gamma was required to inhibit HCV replication, the HBV-specific TCR-reprogrammed resting T cells reduced HBV replication also through intracellular activation of apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3 (APOBEC3). The mechanism of APOBEC3 intracellular activation involved temporal expression of lymphotoxin-β receptor ligands on resting T cells after TCR-mediated antigen recognition and activation of lymphotoxin-β receptor in infected cells.

CONCLUSIONS

We developed TCR-reprogrammed nonlytic T cells capable of activating APOBEC3 in hepatoma cells and in HBV-infected human hepatocytes in mice, limiting viral infection. These cells with limited hepatotoxicity might be developed for treatment of chronic HBV infection.

Long-Term Follow-Up of Acute Hepatitis B: New Insights in Its Natural History and Implications for Antiviral Treatment

Acute hepatitis B infection (AHB) is still a common viral acute hepatitis worldwide. As vaccination, antiviral treatment, and immigration are bound to affect the epidemiological landscape of HBV infections, and some of its aspects need to be investigated: (1) the circulation of vaccine escape mutants and of primary drug resistant strains; (2) the change in HBV genotype prevalence; and (3) the clinical implications of AHB and the probability of chronification. The serological, virological, and clinical parameters of 75 patients, acutely infected by HBV, were gathered for a retrospective study. Long-term follow up, either to complete seroconversion or for up to five years, was possible for 44 patients. Sequence analysis of the reverse transcriptase/HBsAg and precore regions was performed to investigate the molecular epidemiology and pathogenesis of recent infections by HBV. Genotype distribution in AHB in Italian patients was radically different from that of chronic infections, with a dramatic increase of extra-European genotypes (A1, F), suggesting that a proportion of AHBs are currently related to imported strains. None of the documented infections occurred in vaccinated individuals, while HBsAg variants (potentially vaccine escape variants) were rare and less prevalent than in chronic infections. No drug resistant strains were observed. Spontaneous viral clearance occurred in all but three cases. Time to viral clearance was inversely proportional to liver damage, but HBsAg titer on day 28 and, better still, HBsAg decay from day 0 to day 28 after admission, were the best predictors of chronification. They are, thus, potentially useful to guide antiviral treatment to prevent chronic evolution.

Hepatitis B virus infection

Hepatitis B virus (HBV) is a hepatotropic virus that can establish a persistent and chronic infection in humans through immune anergy. Currently, 3.5% of the global population is chronically infected with HBV, although the incidence of HBV infections is decreasing owing to vaccination and, to a lesser extent, the use of antiviral therapy to reduce the viral load of chronically infected individuals. The course of chronic HBV infection typically comprises different clinical phases, each of which potentially lasts for decades. Well-defined and verified serum and liver biopsy diagnostic markers enable the assessment of disease severity, viral replication status, patient risk stratification and treatment decisions. Current therapy includes antiviral agents that directly act on viral replication and immunomodulators, such as interferon therapy. Antiviral agents for HBV include reverse transcriptase inhibitors, which are nucleoside or nucleotide analogues that can profoundly suppress HBV replication but require long-term maintenance therapy. Novel compounds are being actively investigated to achieve the goal of HBV surface antigen seroclearance (functional cure), a serological state that is associated with a higher remission rate (thus, no viral rebound) after treatment cessation and a lower rate of cirrhosis and hepatocellular carcinoma. This Primer addresses several aspects of HBV infection, including epidemiology, immune pathophysiology, diagnosis, prevention and management.

CTLA‑4 interferes with the HBV‑specific T cell immune response (Review)

Hepatitis B virus (HBV) infection is a major cause of hepatic inflammation. Successful HBV clearance in patients is associated with sustained viral control by effector T cells. Compared with acute hepatitis B, chronic HBV infection is associated with the depletion of T cells, resulting in weak or absent virus-specific T cells reactivity, which is described as 'exhaustion'. This exhaustion is characterized by impaired cytokine production and sustained expression of multiple coinhibitory molecules. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of many coinhibitory molecules that can attenuate T cell activation by inhibiting costimulation and transmitting inhibitory signals to T cells. Persistent HBV infection results in the upregulation of CTLA-4 on hepatic CD8⁺ T cells. This prompts CD8⁺ T cell apoptosis, and the activation of cytotoxic T lymphocytes is blocked. Similar to CD8⁺ T cells, CD4⁺ T helper (Th) cell proliferation is hindered following CTLA-4 upregulation. In addition, the differentiation of CD4⁺ Th is polarized toward the Th2/peripherally-inducible T regulatory cell types, increasing the levels of anti-inflammatory cytokines. Conversely, the activation of proinflammatory cells (Th1 and follicular helper T) is blocked, and the levels of proinflammatory cytokines decline. This review summarizes the current literature relevant to T cell exhaustion in patients with HBV-related chronic hepatitis, and discusses the roles of CTLA-4 in T cell exhaustion.

Toll-like receptor 7 agonist GS-9620 induces prolonged inhibition of HBV via a type I interferon-dependent mechanism

BACKGROUND & AIMS

GS-9620, an oral agonist of toll-like receptor 7 (TLR7), is in clinical development for the treatment of chronic hepatitis B (CHB). GS-9620 was previously shown to induce prolonged suppression of serum viral DNA and antigens in the woodchuck and chimpanzee models of CHB. Herein, we investigated the molecular mechanisms that contribute to the antiviral response to GS-9620 using in vitro models of hepatitis B virus (HBV) infection.

METHODS

Cryopreserved primary human hepatocytes (PHH) and differentiated HepaRG (dHepaRG) cells were infected with HBV and treated with GS-9620, conditioned media from human peripheral blood mononuclear cells treated with GS-9620 (GS-9620 conditioned media [GS-9620-CM]), or other innate immune stimuli. The antiviral and transcriptional response to these agents was determined.

RESULTS

GS-9620 had no antiviral activity in HBV-infected PHH, consistent with low level TLR7 mRNA expression in human hepatocytes. In contrast, GS-9620-CM induced prolonged reduction of HBV DNA, RNA, and antigen levels in PHH and dHepaRG cells via a type I interferon (IFN)-dependent mechanism. GS-9620-CM did not reduce covalently closed circular DNA (cccDNA) levels in either cell type. Transcriptional profiling demonstrated that GS-9620-CM strongly induced various HBV restriction factors - although not APOBEC3A or the Smc5/6 complex - and indicated that established HBV infection does not modulate innate immune sensing or signaling in cryopreserved PHH. GS-9620-CM also induced expression of immunoproteasome subunits and enhanced presentation of an immunodominant viral peptide in HBV-infected PHH.

CONCLUSIONS

Type I IFN induced by GS-9620 durably suppressed HBV in human hepatocytes without reducing cccDNA levels. Moreover, HBV antigen presentation was enhanced, suggesting additional components of the TLR7-induced immune response played a role in the antiviral response to GS-9620 in animal models of CHB.

LAY SUMMARY

GS-9620 is a drug currently being tested in clinical trials for the treatment of chronic hepatitis B virus (HBV) infection. GS-9620 has previously been shown to suppress HBV in various animal models, but the underlying antiviral mechanisms were not completely understood. In this study, we determined that GS-9620 does not directly activate antiviral pathways in human liver cells, but can induce prolonged suppression of HBV via induction of an antiviral cytokine called interferon. However, interferon did not destroy the HBV genome, suggesting that other parts of the immune response (e.g. activation of immune cells that kill infected cells) also play an important role in the antiviral response to GS-9620.

HBV Bypasses the Innate Immune Response and Does Not Protect HCV From Antiviral Activity of Interferon

BACKGROUND & AIMS

Hepatitis C virus (HCV) infection is sensitive to interferon (IFN)-based therapy, whereas hepatitis B virus (HBV) infection is not. It is unclear whether HBV escapes detection by the IFN-mediated immune response or actively suppresses it. Moreover, little is known on how HBV and HCV influence each other in coinfected cells. We investigated interactions between HBV and the IFN-mediated immune response using HepaRG cells and primary human hepatocytes (PHHs). We analyzed the effects of HBV on HCV replication, and vice versa, at the single-cell level.

METHODS

PHHs were isolated from liver resection tissues from HBV-, HCV-, and human immunodeficiency virus-negative patients. Differentiated HepaRG cells overexpressing the HBV receptor sodium taurocholate cotransporting polypeptide (dHepaRGNTCP) and PHHs were infected with HBV. Huh7.5 cells were transfected with circular HBV DNA genomes resembling viral covalently closed circular DNA (cccDNA), and subsequently infected with HCV; this served as a model of HBV and HCV coinfection. Cells were incubated with IFN inducers, or IFNs, and antiviral response and viral replication were analyzed by immune fluorescence, reverse-transcription quantitative polymerase chain reaction, enzyme-linked immunosorbent assays, and flow cytometry.

RESULTS

HBV infection of dHepaRGNTCP cells and PHHs neither activated nor inhibited signaling via pattern recognition receptors. Incubation of dHepaRGNTCP cells and PHHs with IFN had little effect on HBV replication or levels of cccDNA. HBV infection of these cells did not inhibit JAK-STAT signaling or up-regulation of IFN-stimulated genes. In coinfected cells, HBV did not prevent IFN-induced suppression of HCV replication.

CONCLUSIONS

In dHepaRGNTCP cells and PHHs, HBV evades the induction of IFN and IFN-induced antiviral effects. HBV infection does not rescue HCV from the IFN-mediated response.

A Highly Sensitive and Robust Method for Hepatitis B Virus Covalently Closed Circular DNA Detection in Single Cells and Serum

Despite implications of persistence of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) in the development of hepatocellular carcinoma (HCC), little is known about serum cccDNA in HBV-infected diseases. We developed a cccDNA-selective droplet digital PCR (ddPCR) to assess cccDNA content and dynamics across different stages of HCC development. One hundred forty-seven serum samples and 35 formalin-fixed, paraffin-embedded tumor tissues were derived from patients with HCC or HBV hepatitis/cirrhosis. After specific amplification and selective digestion, probe-based ddPCR was used to quantify cccDNA copy numbers in single cells and clinical samples. The cccDNA in single HepG2.2.15 cells ranged from 0 to 10.8 copies/cell. Compared with non-HCC patients, HCC patients showed a higher cccDNA-positive rate (89.9% versus 53.2%; P = 4.22 × 10^-6) and increased serum cccDNA contents (P = 0.002 and P = 0.041 for hepatitis and cirrhosis patients, respectively). Serum cccDNA ranged from 84 to 1.07 × 10⁵ copies/mL. Quantification of serum cccDNA and HBV-DNA was an effective way to discriminate HCC patients from non-HCC patients, with areas under the curve of receiver operating characteristic of 0.847 (95% CI, 0.759-0.935; sensitivity, 74.5%; specificity, 93.7%). cccDNA-selective ddPCR is sensitive to detect cccDNA in single cells and different clinical samples. Combined analysis of serum cccDNA and HBV-DNA may be a promising strategy for HBV-induced HCC surveillance and antiviral therapy evaluation.

HBsAg-redirected T cells exhibit antiviral activity in HBV-infected human liver chimeric mice

BACKGROUND

Chronic hepatitis B virus (HBV) infection remains incurable. Although HBsAg-specific chimeric antigen receptor (HBsAg-CAR) T cells have been generated, they have not been tested in animal models with authentic HBV infection.

METHODS

We generated a novel CAR targeting HBsAg and evaluated its ability to recognize HBV+ cell lines and HBsAg particles in vitro. In vivo, we tested whether human HBsAg-CAR T cells would have efficacy against HBV-infected hepatocytes in human liver chimeric mice.

RESULTS

HBsAg-CAR T cells recognized HBV-positive cell lines and HBsAg particles in vitro as judged by cytokine production. However, HBsAg-CAR T cells did not kill HBV-positive cell lines in cytotoxicity assays. Adoptive transfer of HBsAg-CAR T cells into HBV-infected humanized mice resulted in accumulation within the liver and a significant decrease in plasma HBsAg and HBV-DNA levels compared with control mice. Notably, the fraction of HBV core-positive hepatocytes among total human hepatocytes was greatly reduced after HBsAg-CAR T cell treatment, pointing to noncytopathic viral clearance. In agreement, changes in surrogate human plasma albumin levels were not significantly different between treatment and control groups.

CONCLUSIONS

HBsAg-CAR T cells have anti-HBV activity in an authentic preclinical HBV infection model. Our results warrant further preclinical exploration of HBsAg-CAR T cells as immunotherapy for HBV.

Direct antiviral properties of TLR ligands against HBV replication in immune-competent hepatocytes

Current therapies for chronic hepatitis B virus (HBV) infections are effective at decreasing the viral load in serum, but do not lead to viral eradication. Recent studies highlighted the therapeutic or “adjuvant” potential of immune-modulators. Our aim was to explore the direct anti-HBV effect of Toll-Like-Receptors (TLR) agonists in hepatocytes. HBV-infected primary human hepatocytes (PHH) or differentiated HepaRG cells (dHepaRG) were treated with various TLR agonists. Amongst all TLR ligands tested, Pam3CSK4 (TLR1/2-ligand) and poly(I:C)-(HMW) (TLR3/MDA5-ligand) were the best at reducing all HBV parameters. No or little viral rebound was observed after treatment arrest, implying a long-lasting effect on cccDNA. We also tested Riboxxol that features improved TLR3 specificity compared to poly(I:C)-(HMW). This agonist demonstrated a potent antiviral effect in HBV-infected PHH. Whereas, poly(I:C)-(HMW) and Pam3CSK4 mainly induced the expression of classical genes from the interferon or NF-κB pathway respectively, Riboxxol had a mixed phenotype. Moreover, TLR2 and TLR3 ligands can activate hepatocytes and immune cells, as demonstrated by antiviral cytokines produced by stimulated hepatocytes and peripheral blood mononuclear cells. In conclusion, our data highlight the potential of innate immunity activation in the direct control of HBV replication in hepatocytes, and support the development of TLR-based antiviral strategies.

Proliferation of primary human hepatocytes and prevention of hepatitis B virus reinfection efficiently deplete nuclear cccDNA in vivo

OBJECTIVE

The stability of the covalently closed circular DNA (cccDNA) in nuclei of non-dividing hepatocytes represents a key determinant of HBV persistence. Contrarily, studies with animal hepadnaviruses indicated that hepatocyte turnover can reduce cccDNA loads but knowledge on the proliferative capacity of HBV-infected primary human hepatocytes (PHHs) in vivo and the fate of cccDNA in dividing PHHs is still lacking. This study aimed to determine the impact of human hepatocyte division on cccDNA stability in vivo.

METHODS

PHH proliferation was triggered by serially transplanting hepatocytes from HBV-infected humanised mice into naïve recipients. Cell proliferation and virological changes were assessed by quantitative PCR, immunofluorescence and RNA in situ hybridisation. Viral integrations were analysed by gel separation and deep sequencing.

RESULTS

PHH proliferation strongly reduced all infection markers, including cccDNA (median 2.4 log/PHH). Remarkably, cell division appeared to cause cccDNA dilution among daughter cells and intrahepatic cccDNA loss. Nevertheless, HBV survived in sporadic non-proliferating human hepatocytes, so that virological markers rebounded as hepatocyte expansion relented. This was due to reinfection of quiescent PHHs since treatment with the entry inhibitor myrcludex-B or nucleoside analogues blocked viral spread and intrahepatic cccDNA accumulation. Viral integrations were detected both in donors and recipient mice but did not appear to contribute to antigen production.

CONCLUSIONS

We demonstrate that human hepatocyte division even without involvement of cytolytic mechanisms triggers substantial cccDNA loss. This process may be fundamental to resolve self-limiting acute infection and should be considered in future therapeutic interventions along with entry inhibition strategies.

Control of viral transcripts as a concept for future HBV therapies

Chronic hepatitis B virus infections affect over 250 million people world-wide, and, at present, are not curable. Of those, over 800000 are expected to die yearly from complications including cirrhosis and primary hepatocellular carcinoma (HCC). A viral episomal DNA intermediate, covalently closed circular DNA (cccDNA) can persist in nuclei of infected hepatocytes and trigger production of infectious virus. Current standard of care treatments against chronic HBV infections primarily rely on nucleoside analogs (NA) that inhibit de novo virus production by inhibiting the viral reverse transcriptase and, as a consequence, reducing virus titers. However, they cannot cure infections, because they do not directly target cccDNA persistence. Nevertheless, NA therapies can halt progression of liver disease including cirrhosis and can reduce the development of hepatocellular carcinoma (HCC). A cure for chronic hepatitis B (CHB) must reduce the load of cccDNA or permanently silence transcription from cccDNA, and ensure sustained activation of an adaptive immune response that prohibits reactivation and spread of residual virus in the liver. As discussed in this review, novel technologies enabling genetic destruction of cccDNA and advances in our understanding of HBV transcriptional control provide exciting opportunities for the future development of curative therapies desperately needed to reduce the burden of chronic HBV infections.

Analyses of HBV cccDNA Quantification and Modification

Covalently closed circular DNA (cccDNA) serves as the transcriptional template of hepatitis B virus (HBV) replication in the nucleus of infected cells. It ensures the persistence of HBV even if replication is blocked. Immune-mediated killing of infected hepatocytes, cell division, or cytokine induced non-cytolytic degradation of cccDNA can induce the loss of cccDNA. For studies on HBV control, the analysis of cccDNA integrity and its exact quantification is very important. Here, we describe different methods for HBV cccDNA quantification and modification.

Advanced Strategies for Eliminating the cccDNA of HBV

Persistent hepatitis B virus (HBV) infection of hepatocytes is associated with a covalently closed circular DNA (cccDNA) episome. Although serologic hepatitis B surface antigen tests are negative, the presence of cccDNA is obviously increased in HBeAg-positive patients compared with that in HBeAg-negative patients, inactive carriers and patients. Moreover, trace cccDNA levels can also be found in the liver cells of patients with resolved hepatitis B infections. Therefore, clearance of cccDNA in hepatocytes could be an effective cure for HBV. In this review, we summarize the strategies that have been employed to eliminate cccDNA in recent years and discuss the future development of treatments for chronic hepatitis B.

Upcoming pharmacological developments in chronic hepatitis B: can we glimpse a cure on the horizon?

Background

Hepatitis B virus (HBV) chronic infection affects up to 240 million people in the world and it is a common cause of cirrhosis and hepatocellular carcinoma (HCC). HBV covalently closed circular DNA (cccDNA) plays an essential role in HBV persistence and replication. Current pharmacological treatment with nucleos(t)ide analogues (NA) may suppress HBV replication with little or no impact on cccDNA, hence lifelong treatment is required in the vast majority of patients. Clearances of intrahepatic cccDNA and/or HBsAg are critical endpoints for future antiviral therapy in chronic HBV. Recent promising developments targeting different molecular HBV life cycle steps are being pre-clinically tested or have moved forward in early clinical trials.

Methods

We review the current state of the art of these pharmacological developments, mainly focusing on efficacy and safety results, which are expected to lay the ground for future HBV eradication. An inclusive literature search on new treatments of HBV using the following electronic databases: Pubmed/MEDLINE, AMED, CINAHL and the Cochrane Central Register of Controlled Trials. Full-text manuscripts and abstracts published over the last 12 years, from 2005 to March 2011 were reviewed for relevance and reference lists were crosschecked for additional applicable studies regarding new HBV antiviral treatment.

Results

HBV entry inhibitors, HBV core inhibitors, HBV cccDNA transcripts RNA interference, HBV cell apoptosis inducers, HBV RNA, viral proteins and DNA knock down agents, HBV release inhibitors, anti-sense nucleosides, exogenous interferon stimulation, interferon response stimulation and HBV therapeutic vaccines were reviewed.

Conclusion

This review will provide readers with an updated vision of current and foreseeable therapeutic developments in chronic hepatitis B.

Hepatitis B virus evades innate immunity of hepatocytes but activates cytokine production by macrophages

Hepatitis B virus (HBV) infects hepatocytes specifically and causes immune-mediated liver damage. How HBV interacts with the innate immunity at the early phase of infection, either with hepatocytes or other cells in the liver, remains controversial. To address this question, we utilized various human cell-culture models and humanized Alb-uPA/SCID mice. All these models were unable to mount an interferon (IFN) response despite robust HBV replication. To elucidate the mechanisms involved in the lack of IFN response, we examined whether HBV actively inhibits innate immune functions of hepatocytes. By treating HBV-infected cells with known inducers of the IFN signaling pathway, we observed no alteration of either sensing or downstream IFN response by HBV. We showed that the DNA innate sensing pathways are poorly active in hepatocytes, consistent with muted innate immune recognition of HBV. Upon exposure to high-level HBV, human macrophages could be activated with increased inflammatory cytokine expressions.

CONCLUSION

HBV behaves like a "stealth" virus and is not sensed by, nor actively interferes with, the intrinsic innate immunity of infected hepatocytes. Macrophages are capable of sensing HBV, but require exposure to high HBV titers, potentially explaining the long "window period" during acute infection and HBV's propensity to chronic infection. (Hepatology 2017;66:1779-1793).

Epigenetic regulation of hepatitis B virus covalently closed circular DNA: Implications for epigenetic therapy against chronic hepatitis B

Hepatitis B virus (HBV) infection represents a significant public health burden worldwide. Although current therapeutics manage to control the disease progression, lifelong treatment and surveillance are required because drug resistance develops during treatment and reactivations frequently occur following medication cessation. Thus, the occurrence of hepatocellular carcinoma is decreased, but not eliminated. One major reason for failure of HBV treatment is the inability to eradicate or inactivate the viral covalently closed circular DNA (cccDNA), which is a stable episomal form of the viral genome decorated with host histones and nonhistone proteins. Accumulating evidence suggests that epigenetic modifications of cccDNA contribute to viral replication and the outcome of chronic HBV infection. Here, we summarize current progress on HBV epigenetics research and the therapeutic implications for chronic HBV infection by learning from the epigenetic therapies for cancer and other viral diseases, which may open a new venue to cure chronic hepatitis B. (Hepatology 2017;66:2066-2077).

Immunopathogenesis of Hepatitis B Virus

Chronic hepatitis B virus (HBV) infection is a global public health issue. There are >250 million people chronically infected with HBV, and these chronic carriers are at high risk of developing end-stage liver diseases and hepatocellular carcinoma. Patients with chronic hepatitis B (CHB) usually acquire the virus perinatally, while most patients infected during adulthood develop acute hepatitis B (AHB), which usually results in viral clearance. HBV infection is noncytopathic, and liver injury is mostly contributed by host immune responses. The virus is stealthy, since the infection rarely induces type I interferon response in the early phase. In AHB, viral infection is detected and restrained by the innate immune response, which is followed by a strong and robust adaptive immune response and accompanied by viral clearance. In patients with CHB, both innate and adaptive immune responses are weak and thus rarely lead to viral clearance. Interferon α and nucleos(t)ide analogues are 2 classes of approved antiviral therapies. The former treatment activates nature killer (NK) cells and NK T cells, which partially enhances the innate immune response, while the later treatment suppresses viral replication by inhibiting reverse transcriptase, which may restore the HBV-specific adaptive immune response. However, single or combined treatment are still far from achieving seroclearance of HBV surface antigen. Although the treatment response is unsatisfactory in current clinical trials using several immunomodulators for boosting antiviral immunity, immunotherapy that is able to induce immune surveillance is still the most promising modality for HBV cure in the future.