Hepatitis B virus-host interactions and novel targets for viral cure

Development of sulfamoylbenzamide-based capsid assembly modulators for hepatitis B virus capsid assembly

Hepatitis B virus (HBV) is a leading cause of chronic hepatitis and remains a significant global public health concern due to the lack of effective treatments. HBV replicates through reverse transcription within the viral capsid, making capsid assembly a promising antiviral target. However, no approved therapies currently target this process. In our previous study, we optimized the structure-activity relationship (SAR) of NVR 3-778 by modifying the A and B rings, leading to the identification of KR-26556 and Compound 3. In this study, we further synthesized derivatives to modify the C ring, resulting in the discovery of KR019 and KR026. These compounds exhibited over 170-fold higher selectivity than the reference compound while demonstrating potent antiviral activity in HBV-replicating cells. Mechanistic studies revealed that KR019 binds to the hydrophobic pocket at the core protein dimer-dimer interface, misdirecting capsid assembly into genome-free capsids and thereby inhibiting viral replication. Additionally, pharmacokinetic profiling confirmed favorable stability and safety. These findings highlight the strong antiviral potential of KR019 and KR026 and provide a foundation for further in vivo investigation.

Domestic Cat Hepadnavirus, a Hepatitis B-like Virus Associated with Feline Liver Disease

In 2018, a surprising finding was reported; cats are naturally infected with a virus related to hepatitis B virus (HBV), domestic cat hepadnavirus (DCH). HBV causes chronic hepatitis and hepatocellular carcinoma in people, and HBV-like viruses cause similar diseases in rodents. If DCH negatively impacts feline health then demand for diagnostics, therapeutics, and vaccination will follow. Hence, understanding pathogenic potential of DCH for cats, and the size of any associated disease burden are critical goals. Here we evaluate progress made towards these goals by reviewing published studies of DCH against the backdrop of our understanding of HBV and HBV-like viruses.

Salicylamide derivatives as potent HBV inhibitors: insights into structure-activity relationships

Current HBV treatment with nucleos(t)ide analogs requires lifelong administration and is associated with the risk of drug resistance, underscoring the urgent need for novel antivirals with alternative targets. Herein, we reported the design, synthesis, and biological evaluation of a series of salicylamide derivatives as potent anti-HBV agents. The nine selected compounds exhibited dose-dependent inhibitory effects on HBV replication, as evidenced by significant reductions in both virion DNA and the secretion levels of HBsAg and HBeAg. Among them, compounds 50 and 56 exhibited the highest anti-HBV activity (IC50 = 0.52 and 0.47 μM, respectively) and selectivity (SI = 20.1 and 17.6, respectively). Mechanistic studies revealed that compounds 27, 31, and 47 impaired HBV core protein (HBc) expression, while compound 50 disrupted capsid formation without significantly affecting HBc expression. These findings highlight the therapeutic potential of salicylamide derivatives as promising anti-HBV agents and provide a foundation for further structural optimization and mechanistic exploration.

A patent review of hepatitis B virus core protein allosteric modulators (2019-present)

INTRODUCTION

The hepatitis B virus (HBV) core protein is a significant therapeutic target due to its essential role in HBV replication. Over the past five years, numerous structurally unique CpAMs have been patented. However, no compounds have been approved due to various issues such as poor pharmacokinetics (PK) and hepatotoxicity. As a result, there is an urgent need to develop novel CpAMs without these limitations.

AREAS COVERED

This review provides a comprehensive analysis of patents related to CpAMs from 2019 to the present, with the aim of delineating the chemical evolution that has occurred in the pursuit of more promising CpAMs. The sources of patent information included databases of the European Patent Office, the China Patent Office and the U.S.A. Patent Office, while relevant research articles were accessed through PubMed.

EXPERT OPINION

During the optimization of CpAMs, striking a good balance between activity and druggability usually poses a certain challenge while the emergence of drug resistance issues further complicates the development process. A comprehensive analysis of the structural features of CpAMs and identification of essential patterns in chemical evolution can reveal common principles that improve pharmacodynamic (PD) and PK profiles, thereby facilitating the discovery of next-generation CpAMs.

Induction of hepatitis B core protein aggregation targeting an unconventional binding site

The hepatitis B virus (HBV) infection is a major global health problem, with chronic infection leading to liver complications and high death toll. Current treatments, such as nucleos(t)ide analogs and interferon-α, effectively suppress viral replication but rarely cure the infection. To address this, new antivirals targeting different components of the HBV molecular machinery are being developed. Here we investigated the hepatitis B core protein (HBc) that forms the viral capsids and plays a vital role in the HBV life cycle. We explored two distinct binding pockets on the HBV capsid: the central hydrophobic pocket of HBc-dimers and the pocket at the tips of capsid spikes. We synthesized a geranyl dimer that binds to the central pocket with micromolar affinity, and dimeric peptides that bind the spike-tip pocket with sub-micromolar affinity. Cryo-electron microscopy further confirmed the binding of peptide dimers to the capsid spike tips and their capsid-aggregating properties. Finally, we show that the peptide dimers induce HBc aggregation in vitro and in living cells. Our findings highlight two tractable sites within the HBV capsid and provide an alternative strategy to affect HBV capsids.

Deciphering Host-Virus Interactions and Advancing Therapeutics for Chronic Viral Infection

Chronic viral infections like HIV, HBV, and HCV establish persistent interactions with the host immune system, resulting in immune evasion and long-term immune dysfunction. These viruses use a range of strategies to limit host defenses, such as downregulating MHC class I, disrupting interferon signaling, altering apoptosis pathways, and suppressing cytotoxic T-cell activity. Key viral proteins, including HIV Nef, HBV X protein, and HCV NS5A, interfere with antigen presentation and JAK/STAT signaling, thereby reducing antiviral immune responses. Chronic infections induce immune exhaustion due to persistent antigen exposure, which leads to the expression of inhibitory receptors like PD-1 and CTLA-4 on T cells. Viral epigenetic changes, such as N6-methyladenosine modifications and histone deacetylation, enhance immune evasion by modulating gene expression in infected cells. Viruses further manipulate host cytokine networks by promoting an immunosuppressive environment through IL-10 and TGF-β secretion, which suppress inflammatory responses and inhibit T-cell activation. This review examines the molecular/cellular mechanisms that enable chronic viruses to escape host immunity, focusing on antigenic variation, cytokine disruption, and control of apoptotic pathways. It also addresses how host genetic factors, such as HLA polymorphisms, influence disease progression. Lastly, we discuss host-targeted therapies, including immune checkpoint inhibitors, cytokine treatments, and CRISPR.

Host-targeting antivirals for chronic viral infections of the liver

Infection with one or several of the five known hepatitis viruses is a leading cause of liver disease and poses a high risk of developing hepatocellular carcinoma upon chronic infection. Chronicity is primarily caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) and poses a significant health burden worldwide. Co-infection of chronic HBV infected patients with hepatitis D virus (HDV) is less common but is marked as the most severe form of chronic viral hepatitis. Hepatitis A virus (HAV) and hepatitis E virus (HEV) primarily cause self-limiting acute hepatitis. However, studies have also reported chronic progression of HEV disease in immunocompromised patients. While considerable progress has been made in the treatment of HCV and HBV through the development of direct-acting antivirals (DAAs), challenges including drug resistance, incomplete viral suppression resulting in failure to achieve clearance and the lack of effective treatment options for HDV and HEV remain. Host-targeting antivirals (HTAs) have emerged as a promising alternative approach to DAAs and aim to disrupt virus-host interactions by modulating host cell pathways that are hijacked during the viral replication cycle. The aim of this review is to provide a comprehensive overview about the major milestones in research and development of HTAs for chronic HBV/HDV and HCV infections. It also summarizes the current state of knowledge on promising host-targeting therapeutic options against HEV infection.

Prospects of viral vector-mediated delivery of sequences encoding anti-HBV designer endonucleases

Available treatment for chronic hepatitis B virus (HBV) infection offers modest functional curative efficacy. The viral replicative intermediate comprising covalently closed circular DNA (cccDNA) is responsible for persistent chronic HBV infection. Hence, current efforts have focused on developing therapies that disable cccDNA. Employing gene editing tools has emerged as an attractive strategy, with the end goal of establishing permanently inactivated cccDNA. Although anti-HBV designer nucleases are effective in vivo, none has yet progressed to clinical trial. Lack of safe and efficient delivery systems remains the limiting factor. Several vectors may be used to deliver anti-HBV gene editor-encoding sequences, with viral vectors being at the forefront. Despite the challenges associated with packaging large gene editor-encoding sequences into viral vectors, advancement in the field is overcoming such limitations. Translation of viral vector-mediated gene editing against HBV to clinical application is within reach. This review discusses the prospects of delivering HBV targeted designer nucleases using viral vectors.

Foxa deficiency restricts hepatitis B virus biosynthesis through epigenic silencing

In the hepatis B virus (HBV) transgenic mouse model of chronic infection, the forkhead box protein A/hepatocyte nuclear factor 3 (Foxa/HNF3) family of pioneer transcription factors are required to support postnatal viral demethylation and subsequent HBV transcription and replication. Liver-specific Foxa-deficient mice with hepatic expression of only Foxa3 do not support HBV replication but display biliary epithelial hyperplasia with bridging fibrosis. However, liver-specific Foxa-deficient mice with hepatic expression of only Foxa1 or Foxa2 also successfully restrict viral transcription and replication but display only minimal alterations in liver physiology. These observations suggest that the level of Foxa activity, rather than the combination of specific Foxa genes, is a key determinant of HBV biosynthesis. Together, these findings suggest that targeting Foxa activity could lead to HBV DNA methylation and transcriptional inactivation, resulting in the resolution of chronic HBV infections that are responsible for approximately one million deaths annually worldwide.

IMPORTANCE

The current absence of curative therapies capable of resolving chronic hepatis B virus (HBV) infection is a major clinical problem associated with considerable morbidity and mortality. The small viral genome limits molecular targets for drug development, suggesting that the identification of cellular factors essential for HBV biosynthesis may represent alternative targets for therapeutic intervention. Genetic Foxa deficiency in the neonatal liver of HBV transgenic mice leads to the transcriptional silencing of viral DNA by CpG methylation without affecting viability or displaying an obvious phenotype. Therefore, limiting liver Foxa activity therapeutically may lead to the methylation of viral covalently closed circular DNA (cccDNA), resulting in its transcriptional silencing and ultimately the resolution of chronic HBV infection.

TLR8 agonist selgantolimod regulates Kupffer cell differentiation status and impairs HBV entry into hepatocytes via an IL-6-dependent mechanism

OBJECTIVE

Achieving HBV cure will require novel combination therapies of direct-acting antivirals and immunomodulatory agents. In this context, the toll-like receptor 8 (TLR8) agonist selgantolimod (SLGN) has been investigated in preclinical models and clinical trials for chronic hepatitis B (CHB). However, little is known regarding its action on immune effectors within the liver. Our aim was to characterise the transcriptomic changes and intercellular communication events induced by SLGN in the hepatic microenvironment.

DESIGN

We identified TLR8-expressing cell types in the human liver using publicly available single-cell RNA-seq data and established a method to isolate Kupffer cells (KCs). We characterised transcriptomic and cytokine KC profiles in response to SLGN. SLGN's indirect effect was evaluated by RNA-seq in hepatocytes treated with SLGN-conditioned media (CM) and quantification of HBV parameters following infection. Pathways mediating SLGN's effect were validated using transcriptomic data from HBV-infected patients.

RESULTS

Hepatic TLR8 expression takes place in the myeloid compartment. SLGN treatment of KCs upregulated monocyte markers (eg, S100A12) and downregulated genes associated with the KC identity (eg, SPIC). Treatment of hepatocytes with SLGN-CM downregulated NTCP and impaired HBV entry. Cotreatment with an interleukin 6-neutralising antibody reverted the HBV entry inhibition.

CONCLUSION

Our transcriptomic characterisation of SLGN sheds light into the programmes regulating KC activation. Furthermore, in addition to its previously described effect on established HBV infection and adaptive immunity, we show that SLGN impairs HBV entry. Altogether, SLGN may contribute through KCs to remodelling the intrahepatic immune microenvironment and may thus represent an important component of future combinations to cure HBV infection.

Small Molecule Assembly Agonist Alters the Dynamics of Hepatitis B Virus Core Protein Dimer and Capsid

Chronic hepatitis B virus (HBV) poses a significant public health burden worldwide, encouraging the search for curative antivirals. One approach is capsid assembly modulators (CAMs), which are assembly agonists. CAMs lead to empty and defective capsids, inhibiting the formation of new viruses, and can also lead to defects in the release of the viral genome, inhibiting new infections. In this study, we employed hydrogen-deuterium exchange mass spectrometry (HDX-MS) to assess the impact of one such CAM, HAP18, on HBV dimers, capsids composed of 120 (or 90) capsid protein dimers, and cross-linked capsids (xl-capsids). HDX analysis revealed hydrogen bonding networks within and between the dimers. HAP18 disrupted the hydrogen bonding network of dimers, demonstrating a previously unappreciated impact on the dimer structure. Conversely, HAP18 stabilized both unmodified and cross-linked capsids. Intriguingly, cross-linking the capsid, which was accomplished by forming disulfides between an engineered C-terminal cysteine, increased the overall rate of HDX. Moreover, HAP18 binding induced conformational changes beyond the binding sites. Our findings provide evidence for allosteric communication within and between capsid protein dimers. These results show that CAMs are capable of harnessing this allosteric network to modulate the dimer and capsid dynamics.

CAM-A-dependent HBV core aggregation induces apoptosis through ANXA1

Background & Aims

Chronic HBV infection is the leading cause of liver disease and of hepatocellular carcinoma. The improvement of antiviral therapy remains an unmet medical need. Capsid assembly modulators (CAMs) target the HBV core antigen (HBc) and inhibit HBV replication. Although CAM-A compounds are well-known inducers of aberrant viral capsid aggregates, their mechanisms of action in HBV-hepatocyte interactions are poorly understood. Recently, we demonstrated that CAM-A molecules lead to a sustained reduction of HBsAg in the serum of HBV replicating mice and induce HBc aggregation in the nucleus of HBc-expressing cells leading to cell death.

Methods

The mechanism of action by which CAM-A compounds induce cell death was investigated using an HBV infection model, HBc-overexpressing HepG2-NTCP cells, primary human hepatocytes, and HBV replicating HepAD38 cells.

Results

We first confirmed the decrease in HBsAg levels associated with CAM-A treatment and the induction of cell toxicity in HBV-infected differentiated HepaRG cells. Next, we showed that CAM-A-mediated nuclear aggregation of HBc was associated with cell death through the activation of apoptosis. Transcriptomic analysis was used to investigate the mechanism of action driving this phenotype. CAM-A-induced HBc nuclear aggregation led to the upregulation of ANXA1 expression, a documented driver of apoptosis. Finally, silencing of ANXA1 expression delayed cell death and apoptosis in CAM-A-treated cells, confirming its direct involvement in CAM-A-induced cell death.

Conclusions

Our results unravel a previously undiscovered mechanism of action involving CAM-As and open the door to new therapeutic strategies involving CAM to achieve a functional cure in patients with chronic infections.

Impact and implications

Chronic HBV infection is a global health threat. To date, no treatment achieves viral clearance in chronically infected patients. In this study, we characterized a new mechanism of action of an antiviral molecule targeting the assembly of the viral capsid (CAM). The study demonstrated that a CAM subtype, CAM-A-induced formation of aberrant structures from HBV core protein aggregates in the nucleus leading to cell death by ANXA1-driven apoptosis. Thus, CAM-A treatment may lead to the specific elimination of HBV-infected cells by apoptosis, paving the way to novel therapeutic strategies for viral cure.

Diagnostic Utility of Pre-Genomic Hepatitis B RNA in the Evaluation of HBV/HIV Coinfection

Background

Newer biomarkers of Hepatitis B virus (HBV) infection and treatment response have not been well-characterized in individuals with HBV/HIV coinfection.

Methods

Pre-genomic RNA (pgRNA) and quantitative HBsAg (qHBsAg) were used to evaluate the associations with baseline characteristics. Participants included two separate groups - 236 with HBV/HIV coinfection enrolled in a cross-sectional cohort in Ghana and 47 from an HBV nucleoside/nucleotide treatment trial comparing tenofovir to adefovir in the United States.

Results

In both cohorts, HBe antigenemia was highly associated with pgRNA and HBV DNA levels. In the treatment cohort, pre-treatment pgRNA serum concentration was 7.0 log10 U/mL, and mean qHBsAg was 201,297 IU/mL. The observed treatment-associated decrease in pgRNA was consistent with a biphasic decline curve that reached second-phase kinetics following treatment week 12. Changes from baseline were significantly correlated with changes in serum ALT (r = - 0.518; P = 0.023) but not with changes in HBV DNA (r = 0.132, P = NS). qHBsAg also correlated with ALT change (r = - 0.488, P = 0.034).

Conclusion

pgRNA and qHBsAg represent newer biomarkers of HBV replication that may help monitor response and treatment outcomes. HBV pgRNA is highly associated with both HBeAg and ALT and may predict both active replication from the closed circular DNA (cccDNA) template as well as hepatic injury.

Etiologically Significant microRNAs in Hepatitis B Virus-Induced Hepatocellular Carcinoma

Hepatitis B virus (HBV) infection has been causally linked to hepatocellular carcinoma (HCC) in more than 50% cases. MicroRNAs (miRNAs) play cross-cutting mechanistic roles in the complex interplay between viral pathogenesis, host survival, and clinical outcomes. The present study set out to identify etiologically significant human miRNAs associated with HBV infection in liver-related pathologies leading to HCC. In diverse tissue types, we assembled 573 miRNAs differentially expressed in HBV-associated liver pathologies, HBV infection, fibrosis, cirrhosis, acute on chronic liver failure, and HCC. Importantly, 43 human differentially expressed miRNAs (hDEmiRs) were regulated in serum/plasma and liver tissue of patients with HBV-positive conditions. However, only two hDEmiRs, hsa-miR-21-5p and hsa-miR-143-3p, were regulated across all disease conditions. To shortlist the functional miRNAs in HBV-induced HCC pathogenesis, a reverse bioinformatics analysis was performed using eight GEO datasets and the TCGA database containing the list of differentially regulated mRNAs in HCC. A comparative study using these data with the identified targets of hDEmiRs, a set of unidirectionally regulated hDEmiRs with the potential to modulate mRNAs in HCC, were found. Moreover, our study identified five miRNAs; hsa-miR-98-5p, hsa-miR-193b-3p, hsa-miR-142-5p, hsa-miR-522-5p, and hsa-miR-370-3p targeting PIGC, KNTC1, CSTF2, SLC41A2, and RAB17, respectively, in HCC. These hDEmiRs and their targets could be pivotal in HBV infection and subsequent liver pathologies modulating HCC clinical progression. HBV infection is the largest contributor to HCC, and the present study comprises the first of its kind compendium of hDEmiRs related to HBV-related pathologies.

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

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

Decoding the multifaceted interventions between human sirtuin 2 and dynamic hepatitis B viral proteins to confirm their roles in HBV replication

The human sirtuin 2 gene (SIRT2) encodes a full-length Sirt2 protein (i.e., the Sirt2 isoform 1), which primarily functions as a cytoplasmic α-tubulin deacetylase, and which promotes the growth of hepatocellular carcinoma (HCC). Hepatitis B virus (HBV) replication itself, or HBV X (HBx) protein-mediated transcriptional transactivation, enhances Sirt2.1 expression; therefore, Sirt2.1 itself is capable of positively increasing HBV transcription and replication. Sirt2.1 is linked to liver fibrosis and epithelial-to-mesenchymal transition and, consequently, augments the risk of HCC. The Sirt2.1 protein enhances the HBV replication cycle by activating the AKT/glycogen synthase kinase 3 beta (GSK3β)/β-catenin pathway. It also activates the transcription of the viral enhancer I/HBx promoter (EnI/Xp) and enhancer II/HBc promoter (EnII/Cp) by targeting the transcription factor p53. The Sirt2 isoform 2 (Sirt2.2) is mainly localized in the cytoplasm, and the N-terminus is shorter by 37 amino acids than that of Sirt2.1. Despite the truncation of the N-terminal region, Sirt2.2 is still capable of enhancing HBV replication and activating the AKT/GSK3β/β-catenin signaling pathway. The Sirt2 isoform 5 (Sirt2.5) is primarily localized to the nucleus, it lacks a nuclear export signal (NES), and the catalytic domain (CD) is truncated. Upon HBV replication, expression of the Sirt2 isoforms is also enhanced, which further upregulates the HBV replication, and, therefore, supports the vicious cycle of viral replication and progression of the disease. Sirt2 diversely affects HBV replication such that its isoform 1 intensely augments HBV replication and isoform 2 (despite of the truncated N-terminal region) moderately enhances HBV replication. Isoform 5, on the other hand, tends to protect the cell (for smooth long-term continued viral replication) from HBV-induced extreme damage or death via a discrete set of regulatory mechanisms impeding viral mRNAs, the hepatitis B core/capsid protein (HBc), core particles, replicative intermediate (RI) DNAs, and covalently closed circular DNA (cccDNA) levels, and, consequently, limiting HBV replication. In contrast to Sirt2.1 and Sirt 2.2, the Sirt2.5-mediated HBV replication is independent of the AKT/GSK3β/β-catenin signaling cascade. Sirt2.5 is recruited more at cccDNA than the recruitment of Sirt2.1 onto the cccDNA. This recruitment causes the deposition of more histone lysine methyltransferases (HKMTs), including SETDB1, SUV39H1, EZH2, and PR-Set7, along with the respective corresponding transcriptional repressive markers such as H3K9me3, H3K27me3, and H4K20me1 onto the HBV cccDNA. In HBV-replicating cells, Sirt2.5 can also make complexes with PR-Set7 and SETDB1. In addition, Sirt2.5 has the ability to turn off transcription from cccDNA through epigenetic modification via either direct or indirect interaction with HKMTs.

Design, Synthesis, and Biological Evaluation of Novel Thioureidobenzamide (TBA) Derivatives as HBV Capsid Assembly Modulators

Hepatitis B virus (HBV) capsid assembly modulators (CAMs) represent a promising therapeutic approach for the treatment of HBV infection. In this study, we designed and synthesized five series of benzamide derivatives based on a multisite-binding strategy at the tolerant region and diversity modification in the solvent-exposed region. Among them, thioureidobenzamide compound 17i exhibited significantly increased anti-HBV activity in HepAD38 (EC50 = 0.012 μM) and HBV-infected HLCZ01 cells (EC50 = 0.033 μM). Moreover, 17i displayed a better inhibitory effect on the assembly of HBV capsid protein compared with NVR 3-778 and a inhibitory effect similar to the clinical drug GLS4. In addition, 17i showed moderate metabolic stability in human microsomes, had excellent oral bioavailability in Sprague-Dawley (SD) rats, and inhibited HBV replication in the HBV carrier mice model, which could be considered as a promising candidate drug for further development.

The premise of capsid assembly modulators towards eliminating HBV persistence

INTRODUCTION

The burden of chronic hepatitis B virus (HBV) results in almost a million deaths per year. The most common treatment for chronic hepatitis B infection is long-term nucleoside analogs (NUC) or one-year interferon-alpha (pegylated or non-pegylated) therapy before or after NUC therapy. Unfortunately, these therapies rarely result in HBV functional cure because they do not eradicate HBV from the nucleus of the hepatocytes, where the covalently closed circular DNA (cccDNA) is formed and/or where the integrated HBV DNA persists in the host genome. Hence, the search continues for novel antiviral therapies that target different steps of the HBV replication cycle to cure chronically infected HBV individuals and eliminate HBV from the liver reservoirs.

AREAS COVERED

The authors focus on capsid assembly modulators (CAMs). These molecules are unique because they impact not only one but several steps of HBV viral replication, including capsid assembly, capsid trafficking into the nucleus, reverse transcription, pre-genomic RNA (pgRNA), and polymerase protein co-packaging.

EXPERT OPINION

Mono- or combination therapy, including CAMs with other HBV drugs, may potentially eliminate hepatitis B infections. Nevertheless, more data on their potential effect on HBV elimination is needed, especially when used daily for 6-12 months.

Treatment of Liver Fibrosis after Hepatitis B with TCM Combined with NAs Evaluated by Noninvasive Diagnostic Methods: A Retrospective Study

Objective. Chronic hepatitis B liver fibrosis is an important intermediate link in the development of liver cirrhosis. A retrospective cohort study was conducted in Longhua Hospital affiliated to the Shanghai University of Traditional Chinese Medicine in order to prove whether integrated traditional Chinese and Western medicine could improve the incidence of CHB complications and clinical prognosis. There are 130 patients with hepatitis B liver fibrosis (being treated from 2011-2021) included in the study, and the patients were divided into 64 TCM users (NAs combined with TCM) and 66 TCM nonusers (NAs antiviral therapy). The serum noninvasive diagnostic model (APRI, FIB-4) and LSM value were used to classify the stages of fibrosis. The results showed that the LSM value was decreased significantly in TCM users compared with TCM nonusers (40.63% versus 28.79%). Indicators of FIB-4 and APRI of TCM users have improved significantly compared with that of TCM nonusers (32.81% versus 10.61% and 35.94% versus 24.24%). The AST, TBIL, and HBsAg levels in TCM users were lower than those in TCM nonusers, and the HBsAg level was inversely correlated with the CD3+, CD4+, and CD8+ in TCM users. The PLT and spleen thickness of TCM users also were improved considerably. The incidence rate of end-point events (decompensated cirrhosis/liver cancer) in TCM nonusers was higher than that of TCM users (16.67% versus 1.56%). The long course of the disease and a family history of hepatitis B were the risk factors for disease progression, and long-term oral administration of TCM was the protective factor. As a result, the serum noninvasive fibrosis index and imaging parameters in TCM users were lower than those of TCM nonusers. Patients in the treatment of NAs combined with TCM had better prognoses such as a lower HBsAg level, a more stable lymphocyte function, and a lower incidence of end-point events. The present findings suggest the effect of TCM combined with NAs in the treatment of chronic hepatitis B liver fibrosis is better than that of single drug treatment.

The antiviral activity of tripartite motif protein 38 in hepatitis B virus replication and gene expression and its association with treatment responses during PEG-IFN-α antiviral therapy

Hepatitis B virus (HBV) infection represents one of the most critical health problems worldwide. Tripartite motif protein 38 (TRIM38) is an interferon-stimulated gene (ISG) that inhibits various DNA and RNA viruses.In this study, we found a mechanistic correlation between TRIM38 expression levels and the efficacy of HBV infection and IFN-α therapy in patients with CHB. TRIM38 was highly induced by IFN-alpha (IFN-α) in vivo and in vitro. TRIM38 overexpression inhibited HBV replication and gene expression in HepG2 and HepG2.2.15 cells, whereas knockdown of TRIM38 increased these processes. Further experiments indicated that TRIM38 protein enhanced the antiviral effect of IFN-α by enhancing the expression of antiviral proteins. A prospective study revealed high TRIM38 levels in peripheral blood PBMCs were from early responders, and increased TRIM38 expression correlated with a better response to PEG-IFN-α therapy. Taken together, our study suggests that TRIM38 plays a vital role in HBV replication and gene expression.

Molecular elucidation of drug-induced abnormal assemblies of the hepatitis B virus capsid protein by solid-state NMR

Hepatitis B virus (HBV) capsid assembly modulators (CAMs) represent a recent class of anti-HBV antivirals. CAMs disturb proper nucleocapsid assembly, by inducing formation of either aberrant assemblies (CAM-A) or of apparently normal but genome-less empty capsids (CAM-E). Classical structural approaches have revealed the CAM binding sites on the capsid protein (Cp), but conformational information on the CAM-induced off-path aberrant assemblies is lacking. Here we show that solid-state NMR can provide such information, including for wild-type full-length Cp183, and we find that in these assemblies, the asymmetric unit comprises a single Cp molecule rather than the four quasi-equivalent conformers typical for the icosahedral T = 4 symmetry of the normal HBV capsids. Furthermore, while in contrast to truncated Cp149, full-length Cp183 assemblies appear, on the mesoscopic level, unaffected by CAM-A, NMR reveals that on the molecular level, Cp183 assemblies are equally aberrant. Finally, we use a eukaryotic cell-free system to reveal how CAMs modulate capsid-RNA interactions and capsid phosphorylation. Our results establish a structural view on assembly modulation of the HBV capsid, and they provide a rationale for recently observed differences between in-cell versus in vitro capsid assembly modulation.

The scientific basis of combination therapy for chronic hepatitis B functional cure

Functional cure of chronic hepatitis B (CHB) - or hepatitis B surface antigen (HBsAg) loss after 24 weeks off therapy - is now the goal of treatment, but is rarely achieved with current therapy. Understanding the hepatitis B virus (HBV) life cycle and immunological defects that lead to persistence can identify targets for novel therapy. Broadly, treatments fall into three categories: those that reduce viral replication, those that reduce antigen load and immunotherapies. Profound viral suppression alone does not achieve quantitative (q)HBsAg reduction or HBsAg loss. Combining nucleos(t)ide analogues and immunotherapy reduces qHBsAg levels and induces HBsAg loss in some patients, particularly those with low baseline qHBsAg levels. Even agents that are specifically designed to reduce viral antigen load might not be able to achieve sustained HBsAg loss when used alone. Thus, rationale exists for the use of combinations of all three therapy types. Monitoring during therapy is important not just to predict HBsAg loss but also to understand mechanisms of HBsAg loss using viral and immunological biomarkers, and in selected cases intrahepatic sampling. We consider various paths to functional cure of CHB and the need to individualize treatment of this heterogeneous infection until a therapeutic avenue for all patients with CHB is available.

The emerging role of DEAD/H-box helicases in hepatitis B virus infection

DEAD/H-box helicases are an essential protein family with a conserved motif containing unique amino acid sequences (Asp-Glu-Ala-Asp/His). Current evidence indicates that DEAD/H-box helicases regulate RNA metabolism and innate immune responses. In recent years, DEAD/H-box helicases have been reported to participate in the development of a variety of diseases, including hepatitis B virus (HBV) infection, which is a significant risk factor for hepatic fibrosis, cirrhosis, and liver cancer. Furthermore, emerging evidence suggests that different DEAD/H-box helicases play vital roles in the regulation of viral replication, based on the interaction of DEAD/H-box helicases with HBV and the modulation of innate signaling pathways mediated by DEAD/H-box helicases. Besides these, HBV can alter the expression and activity of DEAD/H-box helicases to facilitate its biosynthesis. More importantly, current investigation suggests that targeting DEAD/H-box helicases with appropriate compounds is an attractive treatment strategy for the virus infection. In this review, we delineate recent advances in molecular mechanisms relevant to the interplay of DEAD/H-box helicase and HBV and the potential of targeting DEAD/H-box helicase to eliminate HBV infection.

Hepatitis B virus movement through the hepatocyte: An update

Viruses are obligate intracellular pathogens that utilize cellular machinery for many aspects of their propagation and effective egress of virus particles from host cells is one important determinant of virus infectivity. Hijacking host cell processes applies in particular to the hepatitis B virus (HBV), as its DNA genome with about 3 kb in size is one of the smallest viral genomes known. HBV is a leading cause of liver disease and still displays one of the most successful pathogens in human populations worldwide. The extremely successful spread of this virus is explained by its efficient transmission strategies and its versatile particle types, including virions, empty envelopes, naked capsids and others. HBV exploits distinct host trafficking machineries to assemble and release its particle types including nucleocytoplasmic shuttling transport, secretory and exocytic pathways, the Endosomal Sorting Complexes Required for Transport pathway, and the autophagy pathway. Understanding how HBV uses and subverts host membrane trafficking systems offers the chance of obtaining new mechanistic insights into the regulation and function of this essential cellular processes. It can also help to identify potential targets for antiviral interventions. Here, I will provide an overview of HBV maturation, assembly, and budding, with a focus on recent advances, and will point out areas where questions remain that can benefit from future studies. Unless otherwise indicated, almost all presented knowledge was gained from cell culture-based, HBV in vitro -replication and in vitro -infection systems. This article is protected by copyright. All rights reserved.

HBV cccDNA-A Culprit and Stumbling Block for the Hepatitis B Virus Infection: Its Presence in Hepatocytes Perplexed the Possible Mission for a Functional Cure

Hepatitis B virus infection (HBV) is still a big health problem across the globe. It has been linked to the development of liver cirrhosis and hepatocellular carcinoma and can trigger different types of liver damage. Existing medicines are unable to disable covalently closed circular DNA (cccDNA), which may result in HBV persistence and recurrence. The current therapeutic goal is to achieve a functional cure, which means HBV-DNA no longer exists when treatment stops and the absence of HBsAg seroclearance. However, due to the presence of integrated HBV DNA and cccDNA functional treatment is now regarded to be difficult. In order to uncover pathways for potential therapeutic targets and identify medicines that could result in large rates of functional cure, a thorough understanding of the virus' biology is required. The proteins of the virus and episomal cccDNA are thought to be critical for the management and support of the HBV replication cycle as they interact directly with the host proteome to establish the best atmosphere for the virus while evading immune detection. The breakthroughs of host dependence factors, cccDNA transcription, epigenetic regulation, and immune-mediated breakdown have all produced significant progress in our understanding of cccDNA biology during the past decade. There are some strategies where cccDNA can be targeted either in a direct or indirect way and are presently at the point of discovery or preclinical or early clinical advancement. Editing of genomes, techniques targeting host dependence factors or epigenetic gene maintenance, nucleocapsid modulators, miRNA, siRNA, virion secretory inhibitors, and immune-mediated degradation are only a few examples. Though cccDNA approaches for direct targeting are still in the early stages of development, the assembly of capsid modulators and immune-reliant treatments have made it to the clinic. Clinical trials are currently being conducted to determine their efficiency and safety in patients, as well as their effect on viral cccDNA. The influence of recent breakthroughs in the development of new treatment techniques on cccDNA biology is also summarized in this review.

DNA Repair Factor Poly(ADP-Ribose) Polymerase 1 Is a Proviral Factor in Hepatitis B Virus Covalently Closed Circular DNA Formation

The biogenesis and eradication of HBV cccDNA have been a research priority in recent years. In this study, we identified the DNA repair factor PARP1 as a host factor required for the HBV de novo cccDNA formation.

SIRT2 Promotes HBV Transcription and Replication by Targeting Transcription Factor p53 to Increase the Activities of HBV Enhancers and Promoters

Chronic hepatitis B (CHB) virus infection is one of the leading causes of cirrhosis and liver cancer. Although the major drugs against CHB including nucleos(t)ide analogs and PEG-interferon can effectively control human hepatitis B virus (HBV) infection, complete cure of HBV infection is quite rare. Targeting host factors involved in the viral life cycle contributes to developing innovative therapeutic strategies to improve HBV clearance. In this study, we found that the mRNA and protein levels of SIRT2, a class III histone deacetylase, were significantly upregulated in CHB patients, and that SIRT2 protein level was positively correlated with HBV viral load, HBsAg/HBeAg levels, HBcrAg, and ALT/AST levels. Functional analysis confirmed that ectopic SIRT2 overexpression markedly increased total HBV RNAs, 3.5-kb RNA and HBV core DNA in HBV-infected HepG2-Na⁺/taurocholate cotransporting polypeptide cells and primary human hepatocytes. In contrast, SIRT2 silencing inhibited HBV transcription and replication. In addition, we found a positive correlation between SIRT2 expression and HBV RNAs synthesis as well as HBV covalently closed circular DNA transcriptional activity. A mechanistic study suggested that SIRT2 enhances the activities of HBV enhancer I/HBx promoter (EnI/Xp) and enhancer II/HBc promoter (EnII/Cp) by targeting the transcription factor p53. The levels of HBV EnI/Xp and EnII/Cp-bound p53 were modulated by SIRT2. Both the mutation of p53 binding sites in EnI/Xp and EnII/Cp as well as overexpression of p53 abolished the effect of SIRT2 on HBV transcription and replication. In conclusion, our study reveals that, in terms of host factors, a SIRT2-targeted program might be a more effective therapeutic strategy for HBV infection.

Capsid Assembly Modulators as Antiviral Agents against HBV: Molecular Mechanisms and Clinical Perspectives

Despite a preventive vaccine being available, more than 250 million people suffer from chronic hepatitis B virus (HBV) infection, a major cause of liver disease and HCC. HBV infects human hepatocytes where it establishes its genome, the cccDNA with chromosomal features. Therapies controlling HBV replication exist; however, they are not sufficient to eradicate HBV cccDNA, the main cause for HBV persistence in patients. Core protein is the building block of HBV nucleocapsid. This viral protein modulates almost every step of the HBV life cycle; hence, it represents an attractive target for the development of new antiviral therapies. Capsid assembly modulators (CAM) bind to core dimers and perturb the proper nucleocapsid assembly. The potent antiviral activity of CAM has been demonstrated in cell-based and in vivo models. Moreover, several CAMs have entered clinical development. The aim of this review is to summarize the mechanism of action (MoA) and the advancements in the clinical development of CAMs and in the characterization of their mod of action.

Multitasking Na+/Taurocholate Cotransporting Polypeptide (NTCP) as a Drug Target for HBV Infection: From Protein Engineering to Drug Discovery

Hepatitis B virus (HBV) infections are among the major public health concerns worldwide with more than 250 million of chronically ill individuals. Many of them are additionally infected with the Hepatitis D virus, a satellite virus to HBV. Chronic infection frequently leads to serious liver diseases including cirrhosis and hepatocellular carcinoma, the most common type of liver cancer. Although current antiviral therapies can control HBV replication and slow down disease progress, there is an unmet medical need to identify therapies to cure this chronic infectious disease. Lately, a noteworthy progress in fighting against HBV has been made by identification of the high-affinity hepatic host receptor for HBV and HDV, namely Na⁺/taurocholate cotransporting polypeptide (NTCP, gene symbol SLC10A1). Next to its primary function as hepatic uptake transporter for bile acids, NTCP is essential for the cellular entry of HBV and HDV into hepatocytes. Due to this high-ranking discovery, NTCP has become a valuable target for drug development strategies for HBV/HDV-infected patients. In this review, we will focus on a newly predicted three-dimensional NTCP model that was generated using computational approaches and discuss its value in understanding the NTCP’s membrane topology, substrate and virus binding taking place in plasma membranes. We will review existing data on structural, functional, and biological consequences of amino acid residue changes and mutations that lead to loss of NTCP’s transport and virus receptor functions. Finally, we will discuss new directions for future investigations aiming at development of new NTCP-based HBV entry blockers that inhibit HBV tropism in human hepatocytes.

Cellular and Molecular Mechanisms Underlying Scope and Limitation of Ongoing and Innovative Therapies for Treating Chronic Hepatitis B

Millions of people of the world suffer from chronic hepatitis B (CHB), a pathological entity in which the patients are chronically infected with hepatitis B virus (HBV) and express hepatitis B surface antigen (HBsAg) and HBV DNA, as well as evidence of liver damages. Considerable numbers of CHB patients develop cirrhosis of the liver and hepatocellular carcinoma if untreated. Two groups of drugs (interferons and nucleoside analogs) are used to treat CHB patients, but both are endowed with considerable adverse effects, increased costs, extended duration of therapy, and limited efficacy. Thus, there is a pressing need to develop new and innovative therapeutics for CHB patients, and many such drugs have been developed during the last four decades. Some of these drugs have inspired considerable optimism to be a game-changer for the treatment of CHB. Here, we first discuss why ongoing therapeutics such as interferon and nucleoside analogs could not stand the test of time. Next, we dissect the scope and limitation of evolving therapies for CHB by dissecting the cellular and molecular mechanisms of some of these innovative therapeutics.

The Hepatitis B Virus Nucleocapsid-Dynamic Compartment for Infectious Virus Production and New Antiviral Target

Hepatitis B virus (HBV) is a small enveloped DNA virus which replicates its tiny 3.2 kb genome by reverse transcription inside an icosahedral nucleocapsid, formed by a single ~180 amino acid capsid, or core, protein (Cp). HBV causes chronic hepatitis B (CHB), a severe liver disease responsible for nearly a million deaths each year. Most of HBV's only seven primary gene products are multifunctional. Though less obvious than for the multi-domain polymerase, P protein, this is equally crucial for Cp with its multiple roles in the viral life-cycle. Cp provides a stable genome container during extracellular phases, allows for directed intracellular genome transport and timely release from the capsid, and subsequent assembly of new nucleocapsids around P protein and the pregenomic (pg) RNA, forming a distinct compartment for reverse transcription. These opposing features are enabled by dynamic post-transcriptional modifications of Cp which result in dynamic structural alterations. Their perturbation by capsid assembly modulators (CAMs) is a promising new antiviral concept. CAMs inappropriately accelerate assembly and/or distort the capsid shell. We summarize the functional, biochemical, and structural dynamics of Cp, and discuss the therapeutic potential of CAMs based on clinical data. Presently, CAMs appear as a valuable addition but not a substitute for existing therapies. However, as part of rational combination therapies CAMs may bring the ambitious goal of a cure for CHB closer to reality.