Temporal analysis of early immune responses in patients with acute hepatitis B virus infection

Host immune players and their response to Hepatitis C therapies

This study aimed to investigate alterations in the expression of four key cytokines (IL-7, IL-11, IL-15, and IL-27) and assess differential FAM26F expression in response to Hepatitis C virus (HCV) infection. Additionally, it sought to analyze changes in these cytokines after treatment in 244 chronic HCV patients and 28 controls undergoing various treatments, including standard interferon, pegylated interferon, and Direct Acting Antivirals (DAAs). The objective was to compare immune system regulation between treatment groups. The expression levels of FAM26F and the cytokines (IL-7, IL-11, IL-15, and IL-27) were evaluated using Real-time qPCR in PBMCs of treatment groups. Results revealed significant downregulation of IL-7 and IL-27 in infected individuals compared to healthy controls, persisting even after treatment. This suggests the crucial roles of these immune modulators in facilitating the necessary T-cell response for viral clearance. IL-11 expression also remained suppressed post-treatment, supporting viral clearance by restoring the Th1 response. The decrease in IL-11 levels during treatment indicates the restoration of the Th1 response, vital for viral clearance. IL-15, the key cytokine regulating cytotoxic cells (NKT and NK cells), displayed consistent expression across all sample groups, indicating maintained IL-15-induced cytotoxicity in both control and infected individuals. Additionally, FAM26F expression was reduced in the HCV-infected group compared to controls, but higher in HCV-recovered cases, potentially due to reduced infection and enhanced immunity. In conclusion, this research unveils the relationship between FAM26F and HCV infection, highlighting the virus's tendency to suppress cytokine and FAM26F expression. An effective treatment strategy for establishing an ideal host immune response may involve restoring FAM26F and cytokine expression to their normal levels.

Current and future use of antibody-based passive immunity to prevent or control HBV/HDV infections

With the increasing momentum and success of monoclonal antibody therapy in conventional medical practices, there is a revived emphasis on the development of monoclonal antibodies targeting the hepatitis B surface antigen (anti-HBs) for the treatment of chronic hepatitis B (HBV) and hepatitis D (HDV). Combination therapies of anti-HBs monoclonal antibodies, and novel anti-HBV compounds and immunomodulatory drugs presenting a promising avenue to enhanced therapeutic outcomes in HBV/HDV cure regimens. In this review, we will cover the role of antibodies in the protection and clearance of HBV infection, the association of anti-HBV surface antigen antibodies (anti-HBs) in protection against HBV and how antibody effector functions, beyond neutralization, are likely necessary. Lastly, we will review clinical data from previous and ongoing clinical trials of passive antibody therapy to provide a state-of-the-are perspective on passive antibody therapies in combinations with additional novel agents.

Evaluating the Therapeutic Potential of Durvalumab in Adults with Locally Advanced or Metastatic Biliary Tract Cancer: Evidence to Date

Advanced biliary tract cancers (BTCs) have historically been managed with chemotherapy but, in recent years, this treatment paradigm has begun to shift with the introduction of immune checkpoint inhibitors in addition to standard of care chemotherapy. The tumor microenvironment of BTC may be enriched with regulatory T lymphocytes and immune checkpoint expression in some patients. Durvalumab, an anti-programmed death ligand-1 (PD-L1) antibody, in combination with gemcitabine and cisplatin, has now received United States Food and Drug Administration approval for treatment of advanced BTC. Regulatory approval was based on the Phase III, randomized TOPAZ-1 trial that demonstrated survival benefit with addition of durvalumab to gemcitabine plus cisplatin compared to chemotherapy alone. The combination of chemotherapy and immunotherapy was well tolerated, and a subset of patients were able to achieve a durable response, with a 2-year overall survival rate of 23.6%. However, limitations remain in identifying which patients are most likely to benefit from immune checkpoint inhibition. Future study should aim to identify biomarkers predictive of substantial benefit, as well as the role of immune checkpoint inhibition in combination with targeted therapies and radiotherapy in the management of advanced BTC.

Intracellular Host Restriction of Hepatitis B Virus Replication

The hepatitis B virus (HBV) infects hepatocytes and hijacks host cellular mechanisms for its replication. Host proteins can be frontline effectors of the cell's defense and restrict viral replication by impeding multiple steps during its intracellular lifecycle. This review summarizes many of the well-described restriction factors, their mechanisms of restriction, and counteractive measures of HBV, with a special focus on viral transcription. We discuss some of the limitations and knowledge gaps about the restriction factors, highlighting how these factors may be harnessed to facilitate therapeutic strategies against HBV.

STINGing Defenses: Unmasking the Mechanisms of DNA Oncovirus-Mediated Immune Escape

DNA oncoviruses represent an intriguing subject due to their involvement in oncogenesis. These viruses have evolved mechanisms to manipulate the host immune response, facilitating their persistence and actively contributing to carcinogenic processes. This paper describes the complex interactions between DNA oncoviruses and the innate immune system, with a particular emphasis on the cGAS-STING pathway. Exploring these interactions highlights that DNA oncoviruses strategically target and subvert this pathway, exploiting its vulnerabilities for their own survival and proliferation within the host. Understanding these interactions lays the foundation for identifying potential therapeutic interventions. Herein, we sought to contribute to the ongoing efforts in advancing our understanding of the innate immune system in oncoviral pathogenesis.

Single-cell RNA-sequencing of virus-specific cellular immune responses in chronic hepatitis B patients

Chronic hepatitis B (CHB) is a major global health challenge. CHB can be controlled by antivirals but a therapeutic cure is lacking. CHB is characterized by limited HBV-specific T cell reactivity and functionality and expression of inhibitory receptors. The mechanisms driving these T cell phenotypes are only partially understood. Here, we created a single-cell RNA-sequencing dataset of HBV immune responses in patients to contribute to a better understanding of the dysregulated immunity. Blood samples of a well-defined cohort of 21 CHB and 10 healthy controls, including a subset of 5 matched liver biopsies, were collected. scRNA-seq data of total immune cells (55,825) plus sorted HBV-specific (1,963), non-naive (32,773) and PD1+ T cells (96,631) was generated using the 10X Genomics platform (186,123 cells) or the full-length Smart-seq2 protocol (1,069 cells). The shared transcript count matrices of single-cells serve as a valuable resource describing transcriptional changes underlying dysfunctional HBV-related T cell responses in blood and liver tissue and offers the opportunity to identify targets or biomarkers for HBV-related immune exhaustion.

Efficacy of immunotherapy in hepatocellular carcinoma: Does liver disease etiology have a role?

The systemic treatment of hepatocellular carcinoma (HCC) is changing rapidly. After a decade of tyrosine kinase inhibitors (TKIs), as the only therapeutic option for the treatment of advanced HCC, in the last few years several phase III trials demonstrated the efficacy of immune checkpoint inhibitors (ICIs). The combination of the anti-PD-L1 atezolizumab and the anti-vascular endothelial growth factor (VEGF) bevacizumab demonstrated the superiority over sorafenib and currently represents the standard of care treatment for advanced HCC. In addition, the combination of durvalumab (an anti-PD-L1) and tremelimumab (an anti-CTLA4) proved to be superior to sorafenib, and in the same trial durvalumab monotherapy showed non-inferiority compared to sorafenib. However, early reports suggest an influence of HCC etiology in modulating the response to these drugs. In particular, a lower effectiveness of ICIs has been suggested in patients with non-viral HCC (in particular non-alcoholic fatty liver disease). Nevertheless, randomized controlled trials available to date have not been stratified for etiology and data suggesting a possible impact of etiology in the outcome of patients managed with ICIs derive from subgroup not pre-specified analyses. In this review, we aim to examine the potential impact of HCC etiology on the response to immunotherapy regimens for HCC.

The novel mechanism facilitating chronic hepatitis B infection: immunometabolism and epigenetic modification reprogramming

Hepatitis B Virus (HBV) infections pose a global public health challenge. Despite extensive research on this disease, the intricate mechanisms underlying persistent HBV infection require further in-depth elucidation. Recent studies have revealed the pivotal roles of immunometabolism and epigenetic reprogramming in chronic HBV infection. Immunometabolism have identified as the process, which link cell metabolic status with innate immunity functions in response to HBV infection, ultimately contributing to the immune system's inability to resolve Chronic Hepatitis B (CHB). Within hepatocytes, HBV replication leads to a stable viral covalently closed circular DNA (cccDNA) minichromosome located in the nucleus, and epigenetic modifications in cccDNA enable persistence of infection. Additionally, the accumulation or depletion of metabolites not only directly affects the function and homeostasis of immune cells but also serves as a substrate for regulating epigenetic modifications, subsequently influencing the expression of antiviral immune genes and facilitating the occurrence of sustained HBV infection. The interaction between immunometabolism and epigenetic modifications has led to a new research field, known as metabolic epigenomics, which may form a mutually reinforcing relationship with CHB. Herein, we review the recent studies on immunometabolism and epigenetic reprogramming in CHB infection and discuss the potential mechanisms of persistent HBV infection. A deeper understanding of these mechanisms will offer novel insights and targets for intervention strategies against chronic HBV infection, thereby providing new hope for the treatment of related diseases.

Mechanism of interferon alpha therapy for chronic hepatitis B and potential approaches to improve its therapeutic efficacy

Hepatitis B virus (HBV) chronically infects 296 million people worldwide and causes more than 820,000 deaths annually due to cirrhosis and hepatocellular carcinoma. Current standard-of-care medications for chronic hepatitis B (CHB) include nucleos(t)ide analogue (NA) viral DNA polymerase inhibitors and pegylated interferon alpha (PEG-IFN-α). NAs can efficiently suppress viral replication and improve liver pathology, but not eliminate or inactivate HBV covalently closed circular DNA (cccDNA). CCC DNA is the most stable HBV replication intermediate that exists as a minichromosome in the nucleus of infected hepatocyte to transcribe viral RNA and support viral protein translation and genome replication. Consequentially, a finite duration of NA therapy rarely achieves a sustained off-treatment suppression of viral replication and life-long NA treatment is most likely required. On the contrary, PEG-IFN-α has the benefit of finite treatment duration and achieves HBsAg seroclearance, the indication of durable immune control of HBV replication and functional cure of CHB, in approximately 5% of treated patients. However, the low antiviral efficacy and poor tolerability limit its use. Understanding how IFN-α suppresses HBV replication and regulates antiviral immune responses will help rational optimization of IFN therapy and development of novel immune modulators to improve the rate of functional cure. This review article highlights mechanistic insight on IFN control of HBV infection and recent progress in development of novel IFN regimens, small molecule IFN mimetics and combination therapy of PEG-IFN-α with new direct-acting antivirals and therapeutic vaccines to facilitate the functional cure of CHB.

Therapeutic vaccination with lentiviral vector in HBV-persistent mice and two inactive HBsAg carriers

BACKGROUND & AIMS

Immunotherapy for chronic hepatitis B virus (HBV) infection has not yet demonstrated sufficient efficacy. We developed a non-integrative lentiviral-vectored therapeutic vaccine for chronic hepatitis B and tested its antiviral effects in HBV-persistent mice and two inactive HBsAg carriers.

METHODS

Lentiviral vectors (LVs) encoding the core, preS1, or large HBsAg (LHBs) proteins of HBV were evaluated for immunogenicity in HBV-naïve mice and therapeutic efficacy in a murine model of chronic HBV infection. In addition, two inactive HBsAg carriers each received two doses of 5×107 transduction units (TU) or 1×108 TU of lentiviral-vectored LHBs (LV-LHBs), respectively. The endpoints were safety, LHBs-specific T-cell responses, and serum HBsAg levels during a 24-week follow-up.

RESULTS

In the mouse models, LV-LHBs was the most promising in eliciting robust antigen-specific T cells and in reducing the levels of serum HBsAg and viral load. By the end of the 34-week observation period, six out of ten (60%) HBV-persistent mice vaccinated with LV-LHBs achieved serum HBsAg loss and significant depletion of HBV-positive hepatocytes in the liver. In the two inactive HBsAg carriers, vaccination with LV-LHBs induced a considerable increase in the number of peripheral LHBs-specific T cells in one patient, and a weak but detectable response in the other, accompanied by a sustained reduction of HBsAg (-0.31 log10 IU/ml and -0.46 log10 IU/ml, respectively) from baseline to nadir.

CONCLUSIONS

A lentiviral-vectored therapeutic vaccine for chronic HBV infection demonstrated the potential to improve HBV-specific T-cell responses and deplete HBV-positive hepatocytes, leading to a sustained loss or reduction of serum HBsAg.

IMPACT AND IMPLICATIONS

Chronic HBV infection is characterized by an extremely low number and profound hypo-responsiveness of HBV-specific T cells. Therapeutic vaccines are designed to improve HBV-specific T-cell responses. We show that immunization with a lentiviral-vectored therapeutic HBV vaccine was able to expand HBV-specific T cells in vivo, leading to reductions of HBV-positive hepatocytes and serum HBsAg.

Serum proteomics reveals a tolerant immune phenotype across multiple pathogen taxa in wild vampire bats

Bats carry many zoonotic pathogens without showing pronounced pathology, with a few exceptions. The underlying immune tolerance mechanisms in bats remain poorly understood, although information-rich omics tools hold promise for identifying a wide range of immune markers and their relationship with infection. To evaluate the generality of immune responses to infection, we assessed the differences and similarities in serum proteomes of wild vampire bats (Desmodus rotundus) across infection status with five taxonomically distinct pathogens: bacteria (Bartonella spp., hemoplasmas), protozoa (Trypanosoma cruzi), and DNA (herpesviruses) and RNA (alphacoronaviruses) viruses. From 19 bats sampled in 2019 in Belize, we evaluated the up- and downregulated immune responses of infected versus uninfected individuals for each pathogen. Using a high-quality genome annotation for vampire bats, we identified 586 serum proteins but found no evidence for differential abundance nor differences in composition between infected and uninfected bats. However, using receiver operating characteristic curves, we identified four to 48 candidate biomarkers of infection depending on the pathogen, including seven overlapping biomarkers (DSG2, PCBP1, MGAM, APOA4, DPEP1, GOT1, and IGFALS). Enrichment analysis of these proteins revealed that our viral pathogens, but not the bacteria or protozoa studied, were associated with upregulation of extracellular and cytoplasmatic secretory vesicles (indicative of viral replication) and downregulation of complement activation and coagulation cascades. Additionally, herpesvirus infection elicited a downregulation of leukocyte-mediated immunity and defense response but an upregulation of an inflammatory and humoral immune response. In contrast to our two viral infections, we found downregulation of lipid and cholesterol homeostasis and metabolism with Bartonella spp. infection, of platelet-dense and secretory granules with hemoplasma infection, and of blood coagulation pathways with T. cruzi infection. Despite the small sample size, our results suggest that vampire bats have a similar suite of immune mechanisms for viruses distinct from responses to the other pathogen taxa, and we identify potential biomarkers that can expand our understanding of pathogenesis of these infections in bats. By applying a proteomic approach to a multi-pathogen system in wild animals, our study provides a distinct framework that could be expanded across bat species to increase our understanding of how bats tolerate pathogens.

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

Introduction

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

Methods

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

Results

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

Discussion

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

IFIT3 Is Increased in Serum from Patients with Chronic Hepatitis B Virus (HBV) Infection and Promotes the Anti-HBV Effect of Interferon Alpha via JAK-STAT2 In Vitro

Increasing evidence indicates that interferon alpha (IFN-α) therapy is an effective treatment option for a subgroup of patients with chronic hepatitis B virus (HBV) infection. It has been confirmed that interferon-induced protein with tetratricopeptide repeats 3 (IFIT3), a member of the interferon-stimulated genes (ISGs), could inhibit the replication of various viruses. However, its effect on HBV replication is unclear. The present study sought to explore the role and mechanism of IFIT3 in IFN-α antiviral activities against HBV. IFIT3 mRNA levels in the peripheral blood of 108 treatment-naive patients and 70 healthy controls were analyzed first. The effect of IFIT3 on the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway under the dual intervention of IFN-α and HBV was also explored in vitro. Treatment-naive individuals exhibited elevated levels of IFIT3 mRNA compared to the controls (P < 0.0001). Mechanistically, the knockdown of IFIT3 inhibited the phosphorylation of signal transducer and activator of transcription 2 (STAT2), whereas the overexpression of IFIT3 produced the opposite effect in vitro. Meanwhile, the overexpression of IFIT3 enhanced the expression of IFN-α-triggered ISGs, including myxovirus resistance A (MxA), 2'-5'-oligoadenylate synthetase 1 (OAS1), and double-stranded RNA-activated protein kinase (PKR), while a weaker induction of IFN-α-triggered ISGs was observed in ruxolitinib-treated cells. After decreasing IFIT3 expression by validated small hairpin RNAs (shRNAs), the levels of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and HBV DNA secreted by HepG2 cells transiently transfected with the pHBV1.2 plasmid were increased. Our findings suggest that IFIT3 works in a STAT2-dependent manner to promote the antiviral effect of IFN-α through the JAK-STAT pathway in HBV infection in both human hepatocytes and hepatocarcinoma cells. IMPORTANCE Our study contributes new insights into the understanding of the functions and roles of interferon-induced protein with tetratricopeptide repeats 3 (IFIT3), which is one of the interferon-stimulated genes induced by hepatitis B virus infection in human hepatocytes and hepatocarcinoma cells, and may help to identify targeted genes promoting the efficacy of interferon alpha.

Studying Hepatitis Virus-Host Interactions in Patient Liver Biopsies

Infectious diseases are a major contributor to human suffering and the associated socioeconomic burden worldwide. A better understanding of human pathogen-host interactions is a prerequisite for the development of treatment strategies aimed at combatting human pathogen-induced diseases. Model systems that faithfully recapitulate the pathogen-host interactions in humans are critical to gain meaningful insight. Unfortunately, such model systems are not yet available for a number of pathogens. The strict tropism of the hepatitis B (HBV) and C (HCV) viruses for the human liver has made it difficult to study their virus-host interactions during the natural history of these infections. In this case, surplus liver biopsy tissue donated by patients provides an opportunity to obtain a snapshot of the phenomenological and molecular aspects of the human liver of chronically HCV or HBV-infected patients. In this review, we will briefly summarize our own efforts over the years to advance our knowledge of the virus-host interactions during the natural history of chronic HCV and HBV infection.

Innate Immunity, Inflammation, and Intervention in HBV Infection

Hepatitis B virus (HBV) infection is still one of the most dangerous viral illnesses. HBV infects around 257 million individuals worldwide. Hepatitis B in many individuals ultimately develops hepatocellular carcinoma (HCC), which is the sixth most common cancer and the third leading cause of cancer-related deaths worldwide. The innate immunity acts as the first line of defense against HBV infection through activating antiviral genes. Along with the immune responses, pro-inflammatory cytokines are triggered to enhance the antiviral responses, but this may result in acute or chronic liver inflammation, especially when the clearance of virus is unsuccessful. To a degree, the host innate immune and inflammatory responses dominate the HBV infection and liver pathogenesis. Thus, it is crucial to figure out the signaling pathways involved in the activation of antiviral factors and inflammatory cytokines. Here, we review the interplay between HBV and the signal pathways that mediates innate immune responses and inflammation. In addition, we summarize current therapeutic strategies for HBV infection via modulating innate immunity or inflammation. Characterizing the mechanisms that underlie these HBV-host interplays might provide new approaches for the cure of chronic HBV infection.

IFNα subtype-specific susceptibility of HBV in the course of chronic infection

Chronic hepatitis B virus (HBV) infection continues to be a major health problem worldwide and remains hard to be cured. Therapy with interferon (IFN) α is an important method for the clinical treatment of chronic hepatitis B. IFNα exhibits direct antiviral effects as well as immunomodulatory activities, which can induce sustained antiviral responses in part of the treated chronic hepatitis B patients. Numerous IFNα subtypes with high sequence identity between 76-96% exist which are characterized by diverse, non-redundant biological activities. Our previous studies have demonstrated that the clinically approved IFNα2 is not the most effective subtype for the anti-HBV treatment among all IFNα subtypes. So far very little is known about the IFNα subtype expression pattern during early HBV infection and the IFNα subtype-specific susceptibility during persistent HBV infection as well as its related cellular mechanism. Here we determined the Ifna subtype mRNA expression during acute and chronic HBV infection by using the well-established hydrodynamic injection (HDI) mouse model and we revealed a transient but strong expression of a panel of Ifna subtypes in the spleen of HBV persistent replication mice compared to HDI controls. Immunotherapy with distinct IFNα subtypes controlled chronic HBV infection. IFNα subtype-mediated antiviral response and immune activation were comprehensively analyzed in an AAV-HBV persistent infection murine model and murine IFNα2 was identified as the most effective subtype in suppression of HBV replication. Further analysis of the immune response revealed a strong immunomodulatory activity of murine IFNα2 on splenic and intrahepatic NK and T cell activation during persistent HBV infection. Taken together, our data provide IFNα subtype-specific differences in the antiviral and immunomodulatory effector responses and a strong expression of all IFNα subtypes in the spleen during persistent HBV infection in mice. This knowledge will support the development of novel immunotherapeutic strategies for chronic hepatitis B infection.

Hepatocyte-targeted delivery of imiquimod reduces hepatitis B virus surface antigen

Hepatitis B virus (HBV) can rapidly replicate in the hepatocytes after transmission, leading to chronic hepatitis, liver cirrhosis and eventually hepatocellular carcinoma. Interferon-α (IFN-α) is included in the standard treatment for chronic hepatitis B (CHB). However, this therapy causes serious side effects. Delivering IFN-α selectively to the liver may enhance its efficacy and safety. Imiquimod (IMQ), a Toll-Like Receptor (TLR) 7 agonist, stimulates the release of IFN-α that exhibits potent antiviral activity. However, the poor solubility and tissue selectivity of IMQ limits its clinical use. Here, we demonstrated the use of lipid-based nanoparticles (LNPs) to deliver IMQ and increase the production of IFN-α in the liver. We encapsulated IMQ in two liver-targeted LNP formulations: phospholipid-free small unilamellar vesicles (PFSUVs) and DSPG-liposomes targeting the hepatocytes and the Kupffer cells, respectively. In vitro drug release/retention, in vivo pharmacokinetics, intrahepatic distribution, IFN-α production, and suppression of serum HBV surface antigen (HBsAg) were evaluated and compared for these two formulations. PFSUVs provided >95% encapsulation efficiency for IMQ at a drug-to-lipid ratio (D/L) of 1/20 (w/w) and displayed stable drug retention in the presence of serum. DSPG-IMQ showed 79% encapsulation of IMQ at 1/20 (D/L) and exhibited ∼30% burst release when incubated with serum. Within the liver, PFSUVs showed high selectivity for the hepatocytes while DSPG-liposomes targeted the Kupffer cells. Finally, in an experimental HBV mouse model, PFSUVs significantly reduced serum levels of HBsAg by 12-, 6.3- and 2.2-fold compared to the control, IFN-α, and DSPG-IMQ groups, respectively. The results suggest that the hepatocyte-targeted PFSUVs loaded with IMQ exhibit significant potential for enhancing therapy of CHB.

Recent Drug Development in the Woodchuck Model of Chronic Hepatitis B

Infection with hepatitis B virus (HBV) is responsible for the increasing global hepatitis burden, with an estimated 296 million people being carriers and living with the risk of developing chronic liver disease and cancer. While the current treatment options for chronic hepatitis B (CHB), including oral nucleos(t)ide analogs and systemic interferon-alpha, are deemed suboptimal, the path to finding an ultimate cure for this viral disease is rather challenging. The lack of suitable laboratory animal models that support HBV infection and associated liver disease progression is one of the major hurdles in antiviral drug development. For more than four decades, experimental infection of the Eastern woodchuck with woodchuck hepatitis virus has been applied for studying the immunopathogenesis of HBV and developing new antiviral therapeutics against CHB. There are several advantages to this animal model that are beneficial for performing both basic and translational HBV research. Previous review articles have focused on the value of this animal model in regard to HBV replication, pathogenesis, and immune response. In this article, we review studies of drug development and preclinical evaluation of direct-acting antivirals, immunomodulators, therapeutic vaccines, and inhibitors of viral entry, gene expression, and antigen release in the woodchuck model of CHB since 2014 until today and discuss their significance for clinical trials in patients.

Analyzing the gene regulatory network in hepatitis B patients by single-cell ATAC sequencing

OBJECTIVE

This study aims to provide a new perspective of determining the pathophysiology of chronic hepatitis B (CHB) development by analyzing the gene regulatory network in CHB patients using single-cell ATAC sequencing.

BACKGROUND

Hepatitis B virus (HBV)-related liver disease induces liver damage by hepatic immune and inflammatory responses. The exact mechanism is unknown. As such, there is an urgent need to address this problem and study the relationship between aberrant peripheral blood mononuclear cell (PBMC) immune response and progression of liver disease.

METHOD

The sequencing of the chromatin accessibility of 8016 cells from the whole venous blood of normal control (NC) individuals and CHB patients was performed through assay for transposase-accessible chromatin in single-cell sequencing (ScATAC-seq). Unsupervised clustering and annotation analyses were performed by Signac (version 1.7.0) and Seurat clustering to identify different cell types. Then, TF motif enrichment analysis and differentially expressed peak analysis were performed to identify cell-type-specific candidate open chromatins related to CHB.

RESULT

We identified 12 leukocytic clusters corresponding to five cell types. The specific cell types associated with CHB were found to be located in B-0 and T-3. We have drawn the regulatory network of the hepatitis B signal pathway composed of genes linked to the differentially expressed peaks of these two CHB disease-specific cell types. Further, we profoundly explored the potential mechanisms of B-0-associated TF motif IRF2 and T-3-associated TF motif FOXC2 in the occurrence of CHB.

CONCLUSION

We have drawn a systematic and distinguishing gene regulatory network of CHB-related PBMCs. Key Points • Peripheral blood mononuclear cells were robustly clustered based on their types without using antibodies. • We draw a systematic and distinctive gene regulatory network of CHB-related PBMC through ScATAC-seq.

Toll-like receptor-mediated innate immunity orchestrates adaptive immune responses in HBV infection

Chronic hepatitis B virus (HBV) infection remains to be a substantial global burden, especially for end-stage liver diseases. It is well accepted that HBV-specific T and B cells are essential for controlling HBV infection. Toll-like receptors (TLRs) represent one of the major first-line antiviral defenses through intracellular signaling pathways that induce antiviral inflammatory cytokines and interferons, thereby shaping adaptive immunity. However, HBV has evolved strategies to counter TLR responses by suppressing the expression of TLRs and blocking the downstream signaling pathways, thus limiting HBV-specific adaptive immunity and facilitating viral persistence. Recent studies have stated that stimulation of the TLR signaling pathway by different TLR agonists strengthens host innate immune responses and results in suppression of HBV replication. In this review, we will discuss how TLR-mediated responses shape HBV-specific adaptive immunity as demonstrated in different experimental models. This information may provide important insight for HBV functional cure based on TLR agonists as immunomodulators.

Occult hepatitis B — the result of the host immune response interaction with different genomic expressions of the virus

With over 40 years of history, occult hepatitis B infection (OBI) continues to remain an important and challenging public health problem. Defined as the presence of replication-competent hepatitis B virus (HBV) DNA (i.e., episomal HBV covalently closed circular DNA) in the liver and/or HBV DNA in the blood of people who test negative for hepatitis B surface antigen (HBsAg) in currently available assays, OBI is currently diagnosed using polymerase chain reaction (PCR) and real-time PCR assays. However, all efforts should be made to exclude a false negative HBsAg in order to completely follow the definition of OBI. In recent years, significant advances have been made in understanding the HBV lifecycle and the molecular mechanisms that lead to the persistence of the virus in the occult form. These factors are mainly related to the host immune system and, to a smaller proportion, to the virus. Both innate and adaptive immune responses are important in HBV infection management, and epigenetic changes driven by host mechanisms (acetylation, methylation, and microRNA implication) are added to such actions. Although greater genetic variability in the S gene of HBV isolated from OBIs was found compared with overt infection, the mechanisms of OBI are not mainly viral mutations.

B10 Cells Are Associated With Clinical Prognosis During Adult Symptomatic Acute HBV Infection

There are few reports about the role of B10 cells in acute hepatitis B (AHB) infection. In this study, based on 48 acute hepatitis B infected patients, we analysis the correlation of B10 cells with HBV clinical prognosis. The results showed that B10 was positively correlated with HBsAg and HBeAg and inversely correlated with anti-HBs. The level of B10 in one week before HBsAg clearance was significantly lower than 2 weeks prior to HBsAg clearance and after 1-2 weeks of HBsAg clearance. B10 cell frequency displayed no correlation with HBV DNA; however, it showed significant temporal synchronization with hepatic inflammatory markers such as ALT. B10 level also associated with hospitalization time. These results indicated that B10 is closely related to the clinical prognosis of acute HBV infection.

Viral hepatitis: Past, present, and future

Each hepatitis virus-Hepatitis A, B, C, D, E, and G-poses a distinct scenario to the patient and clinician alike. Since the discovery of each virus, extensive knowledge regarding epidemiology, virologic properties, and the natural clinical and immunologic history of acute and chronic infections has been generated. Basic discoveries about host immunologic responses to acute and chronic viral infections, combined with virologic data, has led to vaccines to prevent Hepatitis A, B, and E and highly efficacious antivirals for Hepatitis B and C. These therapeutic breakthroughs are transforming the fields of hepatology, transplant medicine in general, and public and global health. Most notably, there is even an ambitious global effort to eliminate chronic viral hepatitis within the next decade. While attainable, there are many barriers to this goal that are being actively investigated in basic and clinical labs on the local, national, and international scales. Herein, we discuss pertinent clinical information and recent organizational guidelines for each of the individual hepatitis viruses while also synthesizing this information with the latest research to focus on exciting future directions for each virus.

Immunotherapies for hepatocellular carcinoma

Liver cancer, more specifically hepatocellular carcinoma (HCC), is the second leading cause of cancer-related death and its incidence is increasing globally. Around 50% of patients with HCC receive systemic therapies, traditionally sorafenib or lenvatinib in the first line and regorafenib, cabozantinib or ramucirumab in the second line. In the past 5 years, immune-checkpoint inhibitors have revolutionized the management of HCC. The combination of atezolizumab and bevacizumab has been shown to improve overall survival relative to sorafenib, resulting in FDA approval of this regimen. More recently, durvalumab plus tremelimumab yielded superior overall survival versus sorafenib and atezolizumab plus cabozantinib yielded superior progression-free survival. In addition, pembrolizumab monotherapy and the combination of nivolumab plus ipilimumab have received FDA Accelerated Approval in the second-line setting based on early efficacy data. Despite these major advances, the molecular underpinnings governing immune responses and evasion remain unclear. The immune microenvironment has crucial roles in the development and progression of HCC and distinct aetiology-dependent immune features have been defined. Inflamed and non-inflamed classes of HCC and genomic signatures have been associated with response to immune-checkpoint inhibitors, yet no validated biomarker is available to guide clinical decision-making. This Review provides information on the immune microenvironments underlying the response or resistance of HCC to immunotherapies. In addition, current evidence from phase III trials on the efficacy, immune-related adverse events and aetiology-dependent mechanisms of response are described. Finally, we discuss emerging trials assessing immunotherapies across all stages of HCC that might change the management of this disease in the near future.

Innate and Adaptive Immunopathogeneses in Viral Hepatitis; Crucial Determinants of Hepatocellular Carcinoma

Viral hepatitis B (HBV) and hepatitis C (HCV) infections remain the most common risk factors for the development of hepatocellular carcinoma (HCC), and their heterogeneous distribution influences the global prevalence of this common type of liver cancer. Typical hepatitis infection elicits various immune responses within the liver microenvironment, and viral persistence induces chronic liver inflammation and carcinogenesis. HBV is directly mutagenic but can also cause low-grade liver inflammation characterized by episodes of intermittent high-grade liver inflammation, liver fibrosis, and cirrhosis, which can progress to decompensated liver disease and HCC. Equally, the absence of key innate and adaptive immune responses in chronic HCV infection dampens viral eradication and induces an exhausted and immunosuppressive liver niche that favors HCC development and progression. The objectives of this review are to (i) discuss the epidemiological pattern of HBV and HCV infections, (ii) understand the host immune response to acute and chronic viral hepatitis, and (iii) explore the link between this diseased immune environment and the development and progression of HCC in preclinical models and HCC patients.

Interferon Gamma-Inducible Protein 16 of Peripheral Blood Mononuclear Cells May Sense Hepatitis B Virus Infection and Regulate the Antiviral Immunity

Interferon gamma-inducible protein 16 (IFI16) is a DNA sensor protein, which triggers interferon-beta (IFN-β) production. However, the role of IFI16 in the innate immunity against hepatitis B virus (HBV) remains controversial. Peripheral blood mononuclear cells (PBMCs) and serum specimens were collected from 20 patients with chronic hepatitis B (CHB) receiving Peg-IFN-α2b therapy. IFI16 mRNA/protein of PBMCs and serum IFI16 at baseline and changes during Peg-IFN-α2b treatment were detected. The interaction between IFI16 and HBV DNA in the PBMCs was analyzed using chromatin immunoprecipitation assay. Leukemic T cell line CEM-C7 and HBV-replicating HepG2.2.15 cells were used to test the effects of interferon treatment and HBV replication on IFI16 expression. Compared with healthy controls, lower levels of IFI16 mRNA but more significant expression of IFI16 protein with heterogeneous degradation were detected in PBMCs of CHB patients. Early changes in IFI16 mRNA, but not IFNB mRNA of PBMCs or serum IFI16, were correlated to HBeAg seroconversion of Peg-IFN-α2b therapy. An interaction between IFI16 and HBV DNA was detected in the PBMCs. In the cultured HepG2.2.15 and CEM-C7 cells, interferons resulted in the translocalization of IFI16 from the cytoplasm to the nucleus and inhibited IFI16 degradation. IFI16 of PBMCs may play a role in sensing HBV infection, and early change in IFI16 mRNA of PBMCs is valuable to predict HBeAg seroconversion in Peg-IFN-α2b treatment. The influences on IFI16 degradation and subcellular location may present a molecular mechanism of antiviral activity of interferon.

In Vivo Modelling of Hepatitis B Virus Subgenotype A1 Replication Using Adeno-Associated Viral Vectors

The paucity of animal models that simulate the replication of the hepatitis B virus (HBV) is an impediment to advancing new anti-viral treatments. The work reported here employed recombinant adeno-associated viruses (AAVs) to model HBV subgenotype A1 and subgenotype D3 replication in vitro and in vivo. Infection with subgenotype A1 is endemic to parts of sub-Saharan Africa, and it is associated with a high risk of hepatocellular carcinoma. Recombinant AAV serotype 2 (AAV2) and 8 (AAV8) vectors bearing greater-than-genome-length sequences of HBV DNA from subgenotype A1 and D3, were produced. Transduced liver-derived cultured cells produced HBV surface antigen and core antigen. Administration of AAV8 carrying HBV subgenotype A1 genome (AAV8-A1) to mice resulted in the sustained production of HBV replication markers over a six-month period, without elevated inflammatory cytokines, expression of interferon response genes or alanine transaminase activity. Markers of replication were generally higher in animals treated with subgenotype D3 genome-bearing AAVs than in those receiving the subgenotype A1-genome-bearing vectors. To validate the use of the AAV8-A1 murine model for anti-HBV drug development, the efficacy of anti-HBV artificial primary-microRNAs was assessed. Significant silencing of HBV markers was observed over a 6-month period after administering AAVs. These data indicate that AAVs conveniently and safely recapitulate the replication of different HBV subgenotypes, and the vectors may be used to assess antivirals’ potency.

Nucleic acid vaccines: A taboo broken and prospect for a hepatitis B virus cure

Although a prophylactic vaccine is available, hepatitis B virus (HBV) remains a major cause of liver-related morbidity and mortality. Current treatment options are improving clinical outcomes in chronic hepatitis B; however, true functional cure is currently the exception rather than the rule. Nucleic acid vaccines are among the emerging immunotherapies that aim to restore weakened immune function in chronically infected hosts. DNA vaccines in particular have shown promising results in vivo by reducing viral replication, breaking immune tolerance in a sustained manner, or even decimating the intranuclear covalently closed circular DNA reservoir, the hallmark of HBV treatment. Although DNA vaccines encoding surface antigens administered by conventional injection elicit HBV-specific T cell responses in humans, initial clinical trials failed to demonstrate additional therapeutic benefit when administered with nucleos(t)ide analogs. In an attempt to improve vaccine immunogenicity, several techniques have been used, including codon/promoter optimization, coadministration of cytokine adjuvants, plasmids engineered to express multiple HBV epitopes, or combinations with other immunomodulators. DNA vaccine delivery by electroporation is among the most efficient strategies to enhance the production of plasmid-derived antigens to stimulate a potent cellular and humoral anti-HBV response. Preliminary results suggest that DNA vaccination via electroporation efficiently invigorates both arms of adaptive immunity and suppresses serum HBV DNA. In contrast, the study of mRNA-based vaccines is limited to a few in vitro experiments in this area. Further studies are needed to clarify the prospects of nucleic acid vaccines for HBV cure.

How to get away with liver innate immunity? A viruses' tale

In their never-ending quest towards persistence within their host, hepatitis viruses have developed numerous ways to counteract the liver innate immunity. This review highlights the different and common mechanisms employed by these viruses to (i) establish in the liver (passive entry or active evasion from immune recognition) and (ii) actively inhibit the innate immune response (ie modulation of pattern recognition receptor expression and/or signalling pathways, modulation of interferon response and modulation of immune cells count or phenotype).

HBeAg mediates inflammatory functions of macrophages by TLR2 contributing to hepatic fibrosis

BACKGROUND

We and others have confirmed activation of macrophages plays a critical role in liver injury and fibrogenesis during HBV infection. And we have also proved HBeAg can obviously induce the production of macrophage inflammatory cytokines compared with HBsAg and HBcAg. However, the receptor and functional domain of HBeAg in macrophage activation and its effects and mechanisms on hepatic fibrosis remain elusive.

METHODS

The potentially direct binding receptors of HBeAg were screened and verified by Co-IP assay. Meanwhile, the function domain and accessible peptides of HBeAg for macrophage activation were analyzed by prediction of surface accessible peptide, construction, and synthesis of truncated fragments. Furthermore, effects and mechanisms of the activation of hepatic stellate cells induced by HBeAg-treated macrophages were investigated by Transwell, CCK-8, Gel contraction assay, Phospho Explorer antibody microarray, and Luminex assay. Finally, the effect of HBeAg in hepatic inflammation and fibrosis was evaluated in both human and murine tissues by immunohistochemistry, immunofluorescence, ELISA, and detection of liver enzymes.

RESULTS

Herein, we verified TLR-2 was the direct binding receptor of HBeAg. Meanwhile, C-terminal peptide (122-143 aa.) of core domain in HBeAg was critical for macrophage activation. But arginine-rich domain of HBcAg hided this function, although HBcAg and HBeAg shared the same core domain. Furthermore, HBeAg promoted the proliferation, motility, and contraction of hepatic stellate cells (HSCs) in a macrophage-dependent manner, but not alone. PI3K-AKT-mTOR and p38 MAPK signaling pathway were responsible for motility phenotype of HSCs, while the Smad-dependent TGF-β signaling pathway for proliferation and contraction of them. Additionally, multiple chemokines and cytokines, such as CCL2, CCL5, CXCL10, and TNF-α, might be key mediators of HSC activation. Consistently, HBeAg induced transient inflammation response and promoted early fibrogenesis via TLR-2 in mice. Finally, clinical investigations suggested that the level of HBeAg is associated with inflammation and fibrosis degrees in patients infected with HBV.

CONCLUSIONS

HBeAg activated macrophages via the TLR-2/NF-κB signal pathway and further exacerbated hepatic fibrosis by facilitating motility, proliferation, and contraction of HSCs with the help of macrophages.

Cytokines profile in patients with acute and chronic hepatitis B infection

Hepatitis B virus (HBV) is one of the leading causes of acute and chronic hepatitis and represents a serious public health threat. Cytokines are important chemical mediators that regulate the differentiation, proliferation, and function of immune cells, with accumulating evidence indicating that the inadequate immune responses are responsible for the elimination or persistence of HBV. This study aimed to determine the cytokine profiles (IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10, and IL-17A) during HBV infection and investigate their association with genotypes. A total of 66 plasma samples, 19 from patients with acute and 47 with chronic hepatitis B infection, were subjected to biochemical tests, nested-PCR, and real-time PCR, with cytokines evaluated using a commercial BD Cytometric Bead Array Human Th1/Th2/Th17 Cytokine Kit. Healthy controls (10 individuals) were selected from blood donors with no history of liver diseases. No correlation was found between genotypes, viral load, and cytokines analyzed. All cytokines showed higher levels of production among infected individuals when compared with the control group. A positive correlation classified as moderate to strong was found between cytokines IFN-γ, TNF, IL-10, IL-6, IL-4, and IL-2 through the Spearman correlation coefficient. TNF (P = 0.009), IL-10 (P < 0.001), and IL-6 (P < 0.001) levels were higher in acute individuals compared with chronic and control groups. Theses cytokines could be involved in the elimination of virus and protection against chronicity.

Delivery of toll-like receptor 3 ligand poly(I:C) to the liver by calcium phosphate nanoparticles conjugated with an F4/80 antibody exerts an anti-hepatitis B virus effect in a mouse model

Hepatitis B virus (HBV) is a global health issue, but currently available anti-HBV drugs have limited success. Previously, introduction of the Toll-like receptor (TLR)-3 ligand poly(I:C) to the liver via hydrodynamic injection (HI) was shown to effectively suppress HBV replication in a chronic HBV replication mouse model. However, this method cannot be applied in human beings. To improve the liver targeting of poly(I:C) via intravenous injection, calcium phosphate nanoparticles (CPNs) carrying poly(I:C) with or without antibodies were constructed, and their anti-HBV effects were investigated. We found that significantly more anti-F4/80-conjugated and IgG2α-conjugated nanoparticles were taken up in liver cells both in vivo and in vitro. In addition, these nanoparticles produced pronounced immunostimulatory effects in vitro in primary liver cells. Importantly, treatment with nanoparticles carrying poly(I:C) increased the production of intrahepatic cytokines and chemokines and enhanced T cell responses, significantly reducing HBsAg, HBeAg and HBV DNA levels in the mice. Compared to nonconjugated and isotype-antibody-conjugated nanoparticles, the anti-F4/80-conjugated nanoparticles demonstrated the strongest anti-HBV effects. In summary, nanoparticles carrying poly(I:C) conjugated with an F4/80 antibody promoted liver targeting, and they may represent a suitable alternative to HI for future anti-HBV treatment. STATEMENT OF SIGNIFICANCE: HBV chronically infects approximately 250 million individuals worldwide but current anti-HBV drugs have limited success. Introduction of toll-like receptor 3 ligand poly(I:C) into liver by hydrodynamic injection has been proven to promote HBV clearance in mouse model. However, this technique is not clinically suitable for human patients. We have constructed calcium phosphate nanoparticles carrying poly(I:C) with specific antibody targeting liver nonparenchymal cells. The uptake into relevant liver cells and the anti-HBV effects were studied. After intravenous injection into mice, the uptake rate of anti-F4/80-conjugated nanoparticels was enhanced in liver, and these nanoparticles exert effective anti-HBV effects in vivo. This may provide important insight into future HBV immunotherapy based on nanoparticle-mediated drug delivery.

A quantitative systems pharmacology model for acute viral hepatitis B

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Mechanistic model characterizing acute immune response and HBV system interactions.

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Key role of the cellular and regulatory response triggering hepatitis B chronicity.

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Modelling framework to easily incorporate and explore additional biological mechanisms.

Hepatitis B liver infection is caused by hepatitis B virus (HBV) and represents a major global disease problem when it becomes chronic, as is the case for 80–90% of vertical or early life infections. However, in the vast majority (>95%) of adult exposures, the infected individuals are capable of mounting an effective immune response leading to infection resolution. A good understanding of HBV dynamics and the interaction between the virus and immune system during acute infection represents an essential step to characterize and understand the key biological processes involved in disease resolution, which may help to identify potential interventions to prevent chronic hepatitis B.

In this work, a quantitative systems pharmacology model for acute hepatitis B characterizing viral dynamics and the main components of the innate, adaptive, and tolerant immune response has been successfully developed. To do so, information from multiple sources and across different organization levels has been integrated in a common mechanistic framework. The final model adequately describes the chronology and plausibility of an HBV-triggered immune response, as well as clinical data from acute patients reported in the literature. Given the holistic nature of the framework, the model can be used to illustrate the relevance of the different immune pathways and biological processes to ultimate response, observing the negligible contribution of the innate response and the key contribution of the cellular response on viral clearance. More specifically, moderate reductions of the proliferation of activated cytotoxic CD8+ lymphocytes or increased immunoregulatory effects can drive the system towards chronicity.

Toll-Like Receptor Response to Hepatitis B Virus Infection and Potential of TLR Agonists as Immunomodulators for Treating Chronic Hepatitis B: An Overview

Chronic hepatitis B virus (HBV) infection remains a major global health problem. The immunopathology of the disease, especially the interplay between HBV and host innate immunity, is poorly understood. Moreover, inconsistent literature on HBV and host innate immunity has led to controversies. However, recently, there has been an increase in the number of studies that have highlighted the link between innate immune responses, including Toll-like receptors (TLRs), and chronic HBV infection. TLRs are the key sensing molecules that detect pathogen-associated molecular patterns and regulate the induction of pro- and anti-inflammatory cytokines, thereby shaping the adaptive immunity. The suppression of TLR response has been reported in patients with chronic hepatitis B (CHB), as well as in other models, including tree shrews, suggesting an association of TLR response in HBV chronicity. Additionally, TLR agonists have been reported to improve the host innate immune response against HBV infection, highlighting the potential of these agonists as immunomodulators for enhancing CHB treatment. In this study, we discuss the current understanding of host innate immune responses during HBV infection, particularly focusing on the TLR response and TLR agonists as immunomodulators.

Simultaneous or prior activation of intrahepatic type I interferon signaling leads to hepatitis B virus persistence in a mouse model

It remains controversial how interferon (IFN) response contributes to hepatitis B virus (HBV) control and pathogenesis. A previous study identified that hydrodynamic injection (HI) of type I IFN (IFN-I) inducer polyinosinic-polycytidylic acid (poly(I:C)) leads to HBV clearance in a chronic HBV mouse model. However, recent studies have suggested that premature IFN-I activation in the liver may facilitate HBV persistence. In the present study, we investigated how the early IFN-I response induces an immunosuppressive signaling cascade and thus causes HBV persistence. We performed HI of the plasmid adeno-associated virus (pAAV)/HBV 1.2 into adult BALB/c mice to establish an adult acute HBV replication model. Activation of the IFN-I signaling pathway following poly(I:C) stimulation or murine cytomegalovirus (MCMV) infection resulted in subsequent HBV persistence. HI of poly(I:C) with the pAAV/HBV 1.2 plasmid resulted in not only the production of IFN-I and the anti-inflammatory cytokine interleukin (IL)-10 but also the expansion of intrahepatic regulatory T cells (Tregs), Kupffer cells (KCs) and myeloid-derived suppressor cells (MDSCs), all of which impaired the T cell response. However, when poly(I:C) was injected at day 14 after the HBV plasmid injection, it significantly enhanced HBV specific T cell responses. In addition, interferon-alpha/beta receptor (IFNAR) blockade rescued T cell response by downregulating of IL-10 expression and decreasing Treg and KC expansion. Consistently, Treg depletion or IL-10 blockade also controlled HBV replication. Importance: IFN-I plays a double-edged sword role during chronic HBV infection. Here, we identified that application of IFN-I at different time points causes contrast outcome. Activation of the IFN-I pathway before HBV replication induces an immunosuppressive signaling cascade in the liver, and consequently caused HBV persistence while IFN-I activation post HBV infection enhances HBV-specific T cell responses and thus promote HBV clearance. This result provided an important clue to the mechanism of HBV persistence in adult individuals.

B Cell-mediated Humoral Immunity in Chronic Hepatitis B Infection

B cell-mediated humoral immunity plays a vital role in viral infections, including chronic hepatitis B virus (HBV) infection, which remains a critical global public health issue. Despite hepatitis B surface antigen-specific antibodies are essential to eliminate viral infections, the reduced immune functional capacity of B cells was identified, which was also correlated with chronic hepatitis B (CHB) progression. In addition to B cells, T follicular helper (Tfh) cells, which assist B cells to produce antibodies, might also be involved in the process of anti-HBV-specific antibody production. Here, we provide a comprehensive review of the role of various subsets of B cells and Tfh cells during CHB progression and discuss current novel treatment strategies aimed at restoring humoral immunity. Understanding the mechanism of dysregulated B cells and Tfh cells will facilitate the ultimate functional cure of CHB patients.

The Inflammatory Cytokine Profile Associated with Liver Damage is Broader and Stronger in Chronic Hepatitis B Patients Compared to Acute Hepatitis B Patients

Liver damage in hepatitis B is immune driven and correlates with inflammatory markers in patient serum. There is no comparison of these markers to determine if inflammatory profiles are distinct to different types of liver damage across patients at different stages of disease. We measured 25 inflammatory markers in acute hepatitis B, chronic hepatitis B patients with HBeAg seroconversion and chronic patients stopping nucleoside analogue therapy. Myeloid markers dominated the inflammatory profile in all stages of hepatitis B. More inflammatory markers were detectable in chronic patients, including elevated concentrations of cytotoxic effectors Fas ligand, TRAIL and TNF-α.

Molecular Mechanisms during Hepatitis B Infection and the Effects of the Virus Variability

The immunopathogenesis and molecular mechanisms involved during a hepatitis B virus (HBV) infection have made the approaches for research complex, especially concerning the patients’ responses in the course of the early acute stage. The study of molecular bases involved in the viral clearance or persistence of the infection is complicated due to the difficulty to detect patients at the most adequate points of the disease, especially in the time lapse between the onset of the infection and the viral emergence. Despite this, there is valuable data obtained from animal and in vitro models, which have helped to clarify some aspects of the early immune response against HBV infection. The diversity of the HBV (genotypes and variants) has been proven to be associated not only with the development and outcome of the disease but also with the response to treatments. That is why factors involved in the virus evolution need to be considered while studying hepatitis B infection. This review brings together some of the published data to try to explain the immunological and molecular mechanisms involved in the different stages of the infection, clinical outcomes, viral persistence, and the impact of the variants of HBV in these processes.

Review of Lambda Interferons in Hepatitis B Virus Infection: Outcomes and Therapeutic Strategies

Hepatitis B virus (HBV) chronically infects over 250 million people worldwide and causes nearly 1 million deaths per year due to cirrhosis and liver cancer. Approved treatments for chronic infection include injectable type-I interferons and nucleos(t)ide reverse transcriptase inhibitors. A small minority of patients achieve seroclearance after treatment with type-I interferons, defined as sustained absence of detectable HBV DNA and surface antigen (HBsAg) antigenemia. However, type-I interferons cause significant side effects, are costly, must be administered for months, and most patients have viral rebound or non-response. Nucleos(t)ide reverse transcriptase inhibitors reduce HBV viral load and improve liver-related outcomes, but do not lower HBsAg levels or impart seroclearance. Thus, new therapeutics are urgently needed. Lambda interferons (IFNLs) have been tested as an alternative strategy to stimulate host antiviral pathways to treat HBV infection. IFNLs comprise an evolutionarily conserved innate immune pathway and have cell-type specific activity on hepatocytes, other epithelial cells found at mucosal surfaces, and some immune cells due to restricted cellular expression of the IFNL receptor. This article will review work that examined expression of IFNLs during acute and chronic HBV infection, the impact of IFNLs on HBV replication in vitro and in vivo, the association of polymorphisms in IFNL genes with clinical outcomes, and the therapeutic evaluation of IFNLs for the treatment of chronic HBV infection.

Immunopathology of Chronic Hepatitis B Infection: Role of Innate and Adaptive Immune Response in Disease Progression

More than 250 million people are living with chronic hepatitis B despite the availability of highly effective vaccines and oral antivirals. Although innate and adaptive immune cells play crucial roles in controlling hepatitis B virus (HBV) infection, they are also accountable for inflammation and subsequently cause liver pathologies. During the initial phase of HBV infection, innate immunity is triggered leading to antiviral cytokines production, followed by activation and intrahepatic recruitment of the adaptive immune system resulting in successful virus elimination. In chronic HBV infection, significant alterations in both innate and adaptive immunity including expansion of regulatory cells, overexpression of co-inhibitory receptors, presence of abundant inflammatory mediators, and modifications in immune cell derived exosome release and function occurs, which overpower antiviral response leading to persistent viral infection and subsequent immune pathologies associated with disease progression towards fibrosis, cirrhosis, and hepatocellular carcinoma. In this review, we discuss the current knowledge of innate and adaptive immune cells transformations that are associated with immunopathogenesis and disease outcome in CHB patients.

Innate immunity in hepatitis B and D virus infection: consequences for viral persistence, inflammation, and T cell recognition

Chronic infections with human hepatitis viruses continue to be a major health burden worldwide. Despite the availability of an effective prophylactic vaccine against the hepatitis B virus (HBV) and of antiviral agents efficiently suppressing HBV replication, more than 250 million people are currently chronically infected with this hepatotropic DNA virus, and resolution of chronic hepatitis B (CHB) is rarely achieved. Moreover, coinfection with the hepatitis D virus (HDV), a human RNA satellite virus requiring the envelope proteins of HBV for productive viral spreading, substantially aggravates the disease course of CHB. The molecular mechanisms by which these viruses interact with each other and with the intrinsic innate responses of the hepatocytes are not fully understood. While HBV appears to avoid innate immune recognition, HDV elicits a strong enhancement of innate responses. Notwithstanding, such induction does not hamper HDV replication but contributes to liver inflammation and pathogenesis. Intriguingly, HDV appears to influence the ability of T cells to recognize infected hepatocytes by boosting antigen presentation. This review focuses on current knowledge regarding how these viruses can shape and counteract the intrinsic innate responses of the hepatocytes, thus affecting the immune system and pathogenesis. Understanding the distinct strategies of persistence that HBV and HDV have evolved is central for advancing the development of curative therapies.

The Functional and Antiviral Activity of Interferon Alpha-Inducible IFI6 Against Hepatitis B Virus Replication and Gene Expression

Hepatitis B virus is an enveloped DNA virus, that infects more than three hundred and sixty million people worldwide and leads to severe chronic liver diseases. Interferon-alpha inducible protein 6 (IFI6) is an IFN-stimulated gene (ISG) whose expression is highly regulated by the stimulation of type I IFN-alpha that restricts various kinds of virus infections by targeting different stages of the viral life cycle. This study aims to investigate the antiviral activity of IFI6 against HBV replication and gene expression. The IFI6 was highly induced by the stimulation of IFN-α in hepatoma cells. The overexpression of IFI6 inhibited while knockdown of IFI6 elevated replication and gene expression of HBV in HepG2 cells. Further study determined that IFI6 inhibited HBV replication by reducing EnhII/Cp of the HBV without affecting liver enriched transcription factors that have significant importance in regulating HBV enhancer activity. Furthermore, deletion mutation of EnhII/Cp and CHIP analysis revealed 100 bps (1715-1815 nt) putative sites involved in IFI6 mediated inhibition of HBV. Detailed analysis with EMSA demonstrated that 1715-1770 nt of EnhII/Cp was specifically involved in binding with IFI6 and restricted EnhII/Cp promoter activity. Moreover, IFI6 was localized mainly inside the nucleus to involve in the anti-HBV activity of IFI6. In vivo analysis based on the hydrodynamic injection of IFI6 expression plasmid along with HBV revealed significant inhibition of HBV DNA replication and gene expression. Overall, our results suggested a novel mechanism of IFI6 mediated HBV regulation that could develop potential therapeutics for efficient HBV infection treatment.

Peripheral natural killer cells in chronic hepatitis B patients display multiple molecular features of T cell exhaustion

Antiviral effectors such as natural killer (NK) cells have impaired functions in chronic hepatitis B (CHB) patients. The molecular mechanism responsible for this dysfunction remains poorly characterised. We show that decreased cytokine production capacity of peripheral NK cells from CHB patients was associated with reduced expression of NKp30 and CD16, and defective mTOR pathway activity. Transcriptome analysis of patients NK cells revealed an enrichment for transcripts expressed in exhausted T cells suggesting that NK cell dysfunction and T cell exhaustion employ common mechanisms. In particular, the transcription factor TOX and several of its targets were over-expressed in NK cells of CHB patients. This signature was predicted to be dependent on the calcium-associated transcription factor NFAT. Stimulation of the calcium-dependent pathway recapitulated features of NK cells from CHB patients. Thus, deregulated calcium signalling could be a central event in both T cell exhaustion and NK cell dysfunction occurring during chronic infections.

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

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

Macrophage Phenotypes and Hepatitis B Virus Infection

Globally, hepatitis B virus (HBV) infection and its related liver diseases account for 780,000 deaths every year. Outcomes of HBV infection depend on the interaction between the virus and host immune system. It is becoming increasingly apparent that Kupffer cells (KCs), the largest population of resident and monocyte-derived macrophages in the liver, contribute to HBV infection in various aspects. These cells play an important role not only in the anti-HBV immunity including virus recognition, cytokine production to directly inhibit viral replication and recruitment and activation of other immune cells involved in virus clearance but also in HBV outcome and progression, such as persistent infection and development of end-stage liver diseases. Since liver macrophages play multiple roles in HBV infection, they are directly targeted by HBV to benefit its life cycle. In the present review, we briefly outline the current advances of research of macrophages, especially the studies of their phenotypes, in chronic HBV infection.

Interplay between Hepatitis D Virus and the Interferon Response

Chronic hepatitis D (CHD) is the most severe form of viral hepatitis, with rapid progression of liver-related diseases and high rates of development of hepatocellular carcinoma. The causative agent, hepatitis D virus (HDV), contains a small (approximately 1.7 kb) highly self-pairing single-strand circular RNA genome that assembles with the HDV antigen to form a ribonucleoprotein (RNP) complex. HDV depends on hepatitis B virus (HBV) envelope proteins for envelopment and de novo hepatocyte entry; however, its intracellular RNA replication is autonomous. In addition, HDV can amplify HBV independently through cell division. Cellular innate immune responses, mainly interferon (IFN) response, are crucial for controlling invading viruses, while viruses counteract these responses to favor their propagation. In contrast to HBV, HDV activates profound IFN response through the melanoma differentiation antigen 5 (MDA5) pathway. This cellular response efficiently suppresses cell-division-mediated HDV spread and, to some extent, early stages of HDV de novo infection, but only marginally impairs RNA replication in resting hepatocytes. In this review, we summarize the current knowledge on HDV structure, replication, and persistence and subsequently focus on the interplay between HDV and IFN response, including IFN activation, sensing, antiviral effects, and viral countermeasures. Finally, we discuss crosstalk with HBV.

Distinct Cytokine Profiles Correlate with Disease Severity and Outcome in Longitudinal Studies of Acute Hepatitis B Virus and Hepatitis D Virus Infection in Chimpanzees

Historical studies conducted in chimpanzees gave us the opportunity to investigate the basis for the different severities of liver damage and disease outcome associated with infection with wild-type hepatitis B virus (HBV) versus a precore HBV mutant, HBV/hepatitis D virus (HDV) coinfection, and HDV superinfection. Weekly samples from 9 chimpanzees were studied for immune responses by measuring plasma levels of 29 cytokines in parallel with alanine aminotransferase (ALT) levels and viral kinetics. Comparison of classic acute hepatitis B (AHB) with severe or progressive AHB and HBV/HDV coinfection or superinfection identified distinct cytokine profiles. Classic AHB (mean ALT peak, 362 IU/liter) correlated with an early and significant induction of interferon alpha-2 (IFN-α2), IFN-γ, interleukin-12 p70 (IL-12 p70), and IL-17A. In contrast, these cytokines were virtually undetectable in severe AHB (mean ALT peak, 1,335 IU/liter), characterized by significant elevations of IL-10, tumor necrosis factor alpha (TNF-α), and MIP-1β. In progressive AHB (mean ALT peak, 166 IU/liter), there was a delayed and lower-magnitude induction of cytokines. The ALT peak was also delayed (mean, 23.5 weeks) compared to those of classic (13.5 weeks) and severe AHB (7.5 weeks). HBV/HDV coinfection correlated with significantly lower levels of IFN-α2, IFN-γ, and IL-17A, associated with the presence of multiple proinflammatory cytokines, including IL-1α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, and IL-15. Conversely, HDV superinfection induced the highest ALT peak (1,910 IU/liter) and was associated with a general suppression of cytokines. Our data demonstrate that the most severe liver damage, caused by an HBV precore mutant and HDV, correlated with restricted cytokine expression and lack of Th1 response, raising the question of whether these viruses are directly cytopathic.IMPORTANCE Studies performed in chimpanzees at the National Institutes of Health (NIH) demonstrated a significant difference in ALT levels during acute hepatitis of different viral etiologies, with a hierarchy in the extent of liver damage according to the infecting virus: the highest level was in HDV superinfection, followed by infection with a precore HBV mutant, HBV/HDV coinfection, and, lastly, wild-type HBV infection. Our study demonstrates that both the virus and host are important in disease pathogenesis and offers new insights into their roles. We found that distinct cytokine profiles were associated with disease severity and clinical outcome. In particular, resolution of classic acute hepatitis B (AHB) correlated with a predominant Th1 response, whereas HBV/HDV coinfection showed a predominant proinflammatory response. Severe AHB and HDV superinfection showed a restricted cytokine profile and no evidence of Th1 response. The lack of cytokines associated with adaptive T-cell responses toward the precore HBV mutant and HDV superinfection argues in favor of a direct cytopathic effect of these viruses.

Hepatitis B Virus Might Be Sensed by STING-Dependent DNA Sensors and Attenuates the Response of STING-Dependent DNA Sensing Pathway in Humans with Acute and Chronic Hepatitis B Virus Infection

DNA-dependent activator of interferon regulatory factors (DAIs), interferon gamma inducible protein 16 (IFI16), DEAD-box polypeptide 41 (DDX41), DNA-dependent protein kinase (DNA-PK), meiotic recombination 11 homolog A (MRE11), and cyclic GMP-AMP synthase (cGAS) have been identified as intracellular STING-dependent DNA sensors in recent years. Studies have shown that the DNA sensor-STING-interferon (IFN)-β pathway plays an important role in the defense against intracellular invasion of many DNA viruses. However, the intracellular recognition of hepatitis B virus (HBV) DNA by DNA sensors is still largely unclear. In this study, we aimed to determine whether the DNA sensor-STING pathway in peripheral blood mononuclear cells (PBMCs) can be activated by acute and chronic HBV infections in humans. We first evaluated the expression of these DNA sensors in PBMCs of acute and chronic HBV-infected patients by quantitative real-time polymerase chain reaction. We next compared the expression of the upregulated DNA sensor between monocytes and nonmonocytes to find its cellular source. Finally, by in vitro stimulation, we analyzed the IFN-β response of the DNA sensor-STING pathway in PBMCs and monocytes from chronic HBV-infected patients. The results showed that IFI16, DDX41, MRE11, and the adaptor STING were upregulated in chronic HBV-infected patients, whereas only IFI16 was upregulated in acute HBV-infected patients. However, IFN-β expression was not changed in PBMCs from acute and chronic HBV-infected patients. We next found IFI16 was mainly expressed in monocytes of acute and chronic hepatitis B patients. Finally, by stimulation of monocytes with VACV ds 70mer, a ligand for IFI16, we confirmed the attenuated response of the IFI16-STING pathway. Taken together, our results suggest that HBV might be sensed by DNA sensors in PBMCs of acute and chronic HBV-infected patients, and meanwhile HBV infection attenuates the response of the DNA sensor-STING pathway in PBMCs and monocytes, which may facilitate the persistence of HBV infection.

Immunotherapy of hepatocellular carcinoma with infection of hepatitis B or C virus

Hepatocellular carcinoma (HCC) has one of highest mortalities globally amongst cancers, but has limited therapeutic options once in the advanced stage. Hepatitis B or C virus infection are the most common drivers for HCC carcinogenesis, triggering chronic liver inflammation and adding to the complexity of the immune microecosystem of HCC. The emergence of immunotherapy has afforded a new avenue of therapeutic options for patients with advanced HCC with a history of hepatitis B or C virus infection. This article reviews the change of immunity elicited by hepatitis B or C virus infection, the immune feature of HCC, and the clinical evidence for immunotherapy in advanced HCC and discusses future directions in this field.