Control of cccDNA function in hepatitis B virus infection

A novel, small anti-HBV compound reduces HBsAg and HBV-DNA by destabilizing HBV-RNA

BACKGROUND

Currently, standard treatments for chronic hepatitis B such as nucleos(t)ide analogs (NAs), effectively reduce hepatitis B virus (HBV) loads but rarely result in a functional cure (defined as sustained HBsAg loss). We report the discovery of a novel, 4-pyridone compound, SAG-524, a potent and orally bioavailable small molecule inhibitor of HBV replication.

METHODS

The antiviral characteristics and selectivity of SAG-524 and its derivative compound against HBV were evaluated in HBV-infection assays and HBV-infected chimeric urokinase-type plasminogen activator/severe combined immunodeficiency mice with humanized livers (PXB mice), alone or in combination with entecavir. Toxicity studies were conducted in mice and monkeys.

RESULTS

SAG-524 reduced HBV-DNA (IC50 = 0.92 nM) and HBsAg (IC50 = 1.4 nM) in the supernatant of the HepG2.2.15 cells. SAG-524 selectively destabilized HBV-RNA via PAPD5, but not GAPDH or albumin mRNA, by shortening the poly(A) tail. PAPD5 may also be involved in HBV regulation via ELAVL1. In a study of HBV-infected PXB mice, SAG-524 produced potent reductions of serum HBsAg and HBcrAg, and the minimum effective dose was estimated to be 6 mg/kg/day. The combination therapy with entecavir greatly reduced HBsAg and cccDNA in the liver due to reduction of human hepatocytes with good tolerability. Administration of SAG-524 to monkeys, up to 1000 mg/kg/day for two weeks, led to no significant toxicity, as determined by blood tests and pathological images.

CONCLUSIONS

We have identified SAG-524 as novel and orally bioavailable HBV-RNA destabilizers which can reduce HBsAg and HBV-DNA levels, and possibly contribute a functional cure.

Elimination of the hepatitis B virus: A goal, a challenge

The hepatitis B elimination is a goal proposed by the WHO to be achieved by 2030 through the adoption of synergistic measures for the prevention and chronic HBV infection treatment. Complete cure is characterized by the HBV elimination from the body and is the goal of the chronic hepatitis B treatment, which once achieved, will enable the hepatitis B elimination. This, today, has been a scientific challenge. The difficulty in achieving a complete cure is due to the indefinite maintenance of a covalently closed episomal circular DNA (cccDNA) reservoir and the maintenance and persistence of an insufficient and dysfunctional immune response in chronically infected patients. Among the measures adopted to eliminate hepatitis B, two have the potential to directly interfere with the virus cycle, but with limited effect on HBV control. These are conventional vaccines-blocking transmission and antiviral therapy-inhibiting replication. Vaccines, despite their effectiveness in protecting against horizontal transmission and preventing mother-to-child vertical transmission, have no effect on chronic infection or potential to eliminate the virus. Treatment with antivirals suppresses viral replication, but has no curative effect, as it has no action against cccDNA. Therapeutic vaccines comprise an additional approach in the chronic infection treatment, however, they have only a modest effect on the immune system, enhancing it temporarily. This manuscript aims to address (1) the cccDNA persistence in the hepatocyte nucleus and the immune response dysfunction in chronically infected individuals as two primary factors that have hampered the treatment and HBV elimination from the human body; (2) the limitations of antiviral therapy and therapeutic vaccines, as strategies to control hepatitis B; and (3) the possibly promising therapeutic approaches for the complete cure and elimination of hepatitis B.

G-quadruplexes control hepatitis B virus replication by promoting cccDNA transcription and phase separation in hepatocytes

Phase separation regulates fundamental processes in gene expression and is mediated by the local concentration of proteins and nucleic acids, as well as nucleic acid secondary structures such as G-quadruplexes (G4s). These structures play fundamental roles in both host gene expression and in viral replication due to their peculiar localisation in regulatory sequences. Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is an episomal minichromosome whose persistence is at the basis of chronic infection. Identifying the mechanisms controlling its transcriptional activity is indispensable to develop new therapeutic strategies against chronic hepatitis B. The aim of this study was to determine whether G4s are formed in cccDNA and regulate viral replication. Combining biochemistry and functional studies, we demonstrate that cccDNA indeed contains ten G4s structures. Furthermore, mutations disrupting two G4s located in the enhancer I HBV regulatory region altered cccDNA transcription and viral replication. Finally, we showed for the first time that cccDNA undergoes phase separation in a G4-dependent manner to promote its transcription in infected hepatocytes. Altogether, our data give new insight in the transcriptional regulation of the HBV minichromosome that might pave the way for the identification of novel targets to destabilize or silence cccDNA.

Oxygen-dependent histone lysine demethylase 4 restricts hepatitis B virus replication

Mammalian cells have evolved strategies to regulate gene expression when oxygen is limited. Hypoxia-inducible factors (HIF) are the major transcriptional regulators of host gene expression. We previously reported that HIFs bind and activate hepatitis B virus (HBV) DNA transcription under low oxygen conditions; however, the global cellular response to low oxygen is mediated by a family of oxygenases that work in concert with HIFs. Recent studies have identified a role for chromatin modifiers in sensing cellular oxygen and orchestrating transcriptional responses, but their role in the HBV life cycle is as yet undefined. We demonstrated that histone lysine demethylase 4 (KDM4) can restrict HBV, and pharmacological or oxygen-mediated inhibition of the demethylase increases viral RNAs derived from both episomal and integrated copies of the viral genome. Sequencing studies demonstrated that KDM4 is a major regulator of the hepatic transcriptome, which defines hepatocellular permissivity to HBV infection. We propose a model where HBV exploits cellular oxygen sensors to replicate and persist in the liver. Understanding oxygen-dependent pathways that regulate HBV infection will facilitate the development of physiologically relevant cell-based models that support efficient HBV replication.

LncRNA NKILA inhibits HBV replication by repressing NF-κB signalling activation

Hepatitis B virus (HBV) infection results in liver cirrhosis and hepatocellular carcinoma (HCC). HBx/nuclear factor (NF)-κB pathway plays a role in HBV replication. However, whether NF-κB-interacting long noncoding RNA (NKILA), a suppressor of NF-κB activation, regulates HBV replication remains largely unknown. In this study, gain-and-loss experiments showed that NKILA inhibited HBV replication by inhibiting NF-κB activity. In turn, HBV infection down-regulated NKILA expression. In addition, expression levels of NKILA were lower in the peripheral blood-derived monocytes (PBMCs) of HBV-positive patients than in healthy individuals, which were correlated with HBV viral loads. And a negative correlation between NKILA expression level and HBV viral loads was observed in blood serum from HBV-positive patients. Lower levels of endogenous NKILA were also observed in HepG2 cells expressing a 1.3-fold HBV genome, HBV-infected HepG2-NTCP cells, stable HBV-producing HepG2.2.15 and HepAD38 ​cells, compared to those HBV-negative cells. Furthermore, HBx was required for NKILA-mediated inhibition on HBV replication. NKILA decreased HBx-induced NF-κB activation by interrupting the interaction between HBx and p65, whereas NKILA mutants lack of essential domains for NF-ĸB inhibition, lost the ability to inhibit HBV replication. Together, our data demonstrate that NKILA may serve as a suppressor of HBV replication via NF-ĸB signalling.

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.

HBV eradication from the host: Current understanding and challenges

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Novel Approaches to Inhibition of HBsAg Expression from cccDNA and Chromosomal Integrants: A Review

Hepatitis B virus (HBV) is a widely prevalent liver infection that can cause acute or chronic hepatitis. Although current treatment modalities are highly effective in the suppression of viral levels, they cannot eliminate the virus or achieve definitive cure. This is a consequence of the complex nature of HBV-host interactions. Major challenges to achieving sustained viral suppression include the presence of a high viral burden from the HBV DNA and hepatitis B surface antigen (HBsAg), the presence of reservoirs for HBV replication and antigen production, and the HBV-impaired innate and adaptive immune response of the host. Those therapeutic methods include cell entry inhibitors, HBsAg inhibitors, gene editing approaches, immune-targeting therapies and direct inhibitors of covalently closed circular DNA (cccDNA). Novel approaches that target these key mechanisms are now being studied in preclinical and clinical phases. In this review article, we provide a comprehensive review on mechanisms by which HBV escapes elimination from current treatments, and highlight new agents to achieve a definitive HBV cure.

CD4+ T cells reverse surface antigen persistence in a mouse model of HBV replication

IMPORTANCE

Hepatitis B virus (HBV) is a leading causative agent of viral hepatitis. A preventative vaccine has existed for decades, but only limited treatment options are available for people living with chronic HBV. Animal models for studying HBV are constrained due to narrow viral tropism, impeding understanding of the natural immune response to the virus. Here, using a vector to overcome the narrow host range and establish HBV replication in mice, we identified the role of helper T cells in controlling HBV. We show that helper T cells promote the B cell's ability to generate antibodies that remove HBV and its associated surface antigen from the blood and that transfer of purified helper T cells from HBV-immunized mice can reverse the accumulation of virus and antigen, furthering our understanding of the immune response to HBV.

In vitro evaluation of tropolone absorption, metabolism, and clearance

Tropolone compounds can inhibit hepatitis B virus (HBV) replication at sub-micromolar levels and are synergistic upon co-treatment with nucleos(t)ide analog drugs. However, only a few compounds within this chemotype have been screened for their pharmacological properties. Here, we chose 36 structurally diverse tropolones from six subclasses to characterize their in vitro pharmacological parameters. All compounds were more soluble in pHs that reflect the gastrointestinal tract (pH 5 and 6.5) than plasma (pH 7.4). Those compounds that had solubility limits >100 μM were tested in a passive permeability assay, and there was no general trend in the compounds' passive permeability at any pH. Twenty-nine compounds with the best absorption parameters were tested in HEK293 cells to assess potential cytotoxicity; measured toxicities were similar to those in the hepatic HepDES19 cells used for screening (R2 = 0.55). Sixteen representative compounds were tested against five major CYP450 isoforms and there was no substantial inhibition by any compound against any of the enzymes tested (<50%). The t1/2 values of 15 compounds were determined in the microsome stability assay and 12 compounds were evaluated in plasma protein binding assays to assess factors affecting their rate of clearance. All compounds with detectable analyte peaks had t1/2 > 30 min, and while 4 of 12 had statistically significant decreased potency in conditions with increased albumin concentrations, only one compound's potency was biologically significant. These data indicate that the tropolones have pharmacological characteristics that reflect approved drugs and inform future structure activity relationships during drug design.

The role of HBV cccDNA in occult hepatitis B virus infection

Occult hepatitis B virus (HBV) infection (OBI) refers to the presence of replication-competent HBV DNA in the liver, with or without HBV DNA in the blood, in individuals who tested negative for HBV surface antigen (HBsAg). In this peculiar phase of HBV infection, the covalently closed circular DNA (cccDNA) is in a low state of replication. Several advances have been made toward clarifying the mechanisms involved in such a suppression of viral activity, which seems to be mainly related to the host's immune control and epigenetic factors. Although the underlying mechanisms describing the genesis of OBI are not completely known, the presence of viral cccDNA, which remains in a low state of replication due to the host's strong immune suppression of HBV replication and gene expression, appears to be the causative factor. Through this review, we have provided an updated account on the role of HBV cccDNA in regulating OBI. We have comprehensively described the HBV cell cycle, cccDNA kinetics, current regulatory mechanisms, and the therapeutic methods of cccDNA in OBI-related diseases.

Nuclear translocation of YAP drives BMI-associated hepatocarcinogenesis in hepatitis B virus infection

BACKGROUND AND AIMS

Hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) development and progression. The aim of this study was to mechanistically investigate the involvement of Hippo signalling in HBV surface antigen (HBsAg)-dependent neoplastic transformation.

METHODS

Liver tissue and hepatocytes from HBsAg-transgenic mice were examined for the Hippo cascade and proliferative events. Functional experiments in mouse hepatoma cells included knockdown, overexpression, luciferase reporter assays and chromatin immunoprecipitation. Results were validated in HBV-related HCC biopsies.

RESULTS

Hepatic expression signatures in HBsAg-transgenic mice correlated with YAP responses, cell cycle control, DNA damage and spindle events. Polyploidy and aneuploidy occurred in HBsAg-transgenic hepatocytes. Suppression and inactivation of MST1/2 led to the loss of YAP phosphorylation and the induction of BMI1 expression in vivo and in vitro. Increased BMI1 directly mediated cell proliferation associated with decreased level of p16INK4a , p19ARF , p53 and Caspase 3 as well as increased Cyclin D1 and γ-H2AX expression. Chromatin immunoprecipitation and the analysis of mutated binding sites in dual-luciferase reporter assays confirmed that the YAP/TEAD4 transcription factor complex bound and activated the Bmi1 promoter. In chronic hepatitis B patients, paired liver biopsies of non-tumour and tumour tissue indicated a correlation between YAP expression and the abundance of BMI1. In a proof-of-concept, treatment of HBsAg-transgenic mice with YAP inhibitor verteporfin directly suppressed the BMI1-related cell cycle.

CONCLUSION

HBV-associated proliferative HCC might be related to the HBsAg-YAP-BMI1 axis and offer a potential target for the development of new therapeutic approaches.

Evaluation of reverse transcription-polymerase chain reaction and simultaneous amplification and testing for quantitative detection of serum hepatitis B virus RNA

BACKGROUND

Chronic hepatitis B virus (HBV) infection is one of the common infectious diseases in the world. HBV covalently closed circular DNA (cccDNA) is the initial template of HBV replication, which can exist in human hepatocytes for a long time and is difficult to be completely removed. It has been shown that HBV RNA can directly respond to the levels and transcriptional activity of cccDNA in hepatocytes and can be used as a surrogate marker of cccDNA transcriptional activity. At present, the detection techniques used for quantitative HBV RNA mainly include reverse transcription quantitative polymerase chain reaction (RT-qPCR) and simultaneous amplification and testing (SAT).

METHODS

In this study, we verified the performance of the SAT method for detecting HBV RNA and the clinical effectiveness of SAT and RT-qPCR, and compared the correlation and consistency of the two detection methods for HBV RNA detection.

RESULTS

The results showed that the limit of detection for HBV RNA by SAT method was 50 copies/mL, with a linear range of 1 × 102-1 × 108 copies/mL. There was no difference in HBV RNA levels detected by the two methods. The correlation and consistency of the results were good, with the coefficient of determination of 0.7787 in HBeAg positive group and 0.8235 in HBeAg negative group.

CONCLUSIONS

Therefore, this study confirmed that the SAT method and RT-qPCR for detecting HBV RNA have good agreement, which are both reliable methods to detect HBV RNA and can replace each other.

Live Cell Imaging Reveals HBV Capsid Translocation from the Nucleus To the Cytoplasm Enabled by Cell Division

Hepatitis B virus (HBV) capsid assembly is traditionally thought to occur predominantly in the cytoplasm, where the virus gains access to the virion egress pathway. To better define sites of HBV capsid assembly, we carried out single cell imaging of HBV Core protein (Cp) subcellular trafficking over time under conditions supporting genome packaging and reverse transcription in Huh7 hepatocellular carcinoma cells. Time-course analyses including live cell imaging of fluorescently tagged Cp derivatives showed Cp to accumulate in the nucleus at early time points (~24 h), followed by a marked re-distribution to the cytoplasm at 48 to 72 h. Nucleus-associated Cp was confirmed to be capsid and/or high-order assemblages using a novel dual label immunofluorescence strategy. Nuclear-to-cytoplasmic re-localization of Cp occurred predominantly during nuclear envelope breakdown in conjunction with cell division, followed by strong cytoplasmic retention of Cp. Blocking cell division resulted in strong nuclear entrapment of high-order assemblages. A Cp mutant, Cp-V124W, predicted to exhibit enhanced assembly kinetics, also first trafficked to the nucleus to accumulate at nucleoli, consistent with the hypothesis that Cp's transit to the nucleus is a strong and constitutive process. Taken together, these results provide support for the nucleus as an early-stage site of HBV capsid assembly, and provide the first dynamic evidence of cytoplasmic retention after cell division as a mechanism underpinning capsid nucleus-to-cytoplasm relocalization. IMPORTANCE Hepatitis B virus (HBV) is an enveloped, reverse-transcribing DNA virus that is a major cause of liver disease and hepatocellular carcinoma. Subcellular trafficking events underpinning HBV capsid assembly and virion egress remain poorly characterized. Here, we developed a combination of fixed and long-term (>24 h) live cell imaging technologies to study the single cell trafficking dynamics of the HBV Core Protein (Cp). We demonstrate that Cp first accumulates in the nucleus, and forms high-order structures consistent with capsids, with the predominant route of nuclear egress being relocalization to the cytoplasm during cell division in conjunction with nuclear membrane breakdown. Single cell video microscopy demonstrated unequivocally that Cp's localization to the nucleus is constitutive. This study represents a pioneering application of live cell imaging to study HBV subcellular transport, and demonstrates links between HBV Cp and the cell cycle.

The Complex Role of HBeAg and Its Precursors in the Pathway to Hepatocellular Carcinoma

Hepatitis B virus (HBV) is one of the seven known human oncogenic viruses and has adapted to coexist with a single host for prolonged periods, requiring continuous manipulation of immunity and cell fate decisions. The persistence of HBV infection is associated with the pathogenesis of hepatocellular carcinoma, and various HBV proteins have been implicated in promoting this persistence. The precursor of hepatitis e antigen (HBeAg), is translated from the precore/core region and is post-translationally modified to yield HBeAg, which is secreted in the serum. HBeAg is a non-particulate protein of HBV and can act as both a tolerogen and an immunogen. HBeAg can protect hepatocytes from apoptosis by interfering with host signalling pathways and acting as a decoy to the immune response. By evading the immune response and interfering with apoptosis, HBeAg has the potential to contribute to the hepatocarcinogenic potential of HBV. In particular, this review summarises the various signalling pathways through which HBeAg and its precursors can promote hepatocarcinogenesis via the various hallmarks of cancer.

Emerging Therapies for Chronic Hepatitis B and the Potential for a Functional Cure

Worldwide, an estimated 296 million people are living with chronic hepatitis B virus (HBV) infection, with a significant risk of morbidity and mortality. Current therapy with pegylated interferon (Peg-IFN) and indefinite or finite therapy with nucleoside/nucleotide analogues (Nucs) are effective in HBV suppression, hepatitis resolution, and prevention of disease progression. However, few achieve hepatitis B surface antigen (HBsAg) loss (functional cure), and relapse often occurs after the end of therapy (EOT) because these agents have no direct effect on durable template: covalently closed circular DNA (cccDNA) and integrated HBV DNA. Hepatitis B surface antigen loss rate increases slightly by adding or switching to Peg-IFN in Nuc-treated patients and this loss rate greatly increases up to 39% in 5 years with finite Nuc therapy with currently available Nuc(s). For this, great effort has been made to develop novel direct-acting antivirals (DAAs) and immunomodulators. Among the DAAs, entry inhibitors and capsid assembly modulators have little effect on reducing HBsAg levels; small interfering RNA, antisense oligonucleotides, and nucleic acid polymers in combination with Peg-IFN and Nuc may reduce HBsAg levels significantly, even a rate of HBsAg loss sustained for > 24 weeks after EOT up to 40%. Novel immunomodulators, including T-cell receptor agonists, check-point inhibitors, therapeutic vaccines, and monoclonal antibodies may restore HBV-specific T-cell response but not sustained HBsAg loss. The safety issues and the durability of HBsAg loss warrant further investigation. Combining agents of different classes has the potential to enhance HBsAg loss. Compounds directly targeting cccDNA would be more effective but are still in the early stage of development. More effort is required to achieve this goal.

Development and characterization of a chronic hepatitis B murine model with a mutation in the START codon of an HBV polymerase

Chronic hepatitis B (CHB) is caused by the Hepatitis B virus (HBV) and affects millions of people worldwide. Developing an effective CHB therapy requires using in vivo screening methods, such as mouse models reflecting CHB based on hydrodynamic delivery of plasmid vectors containing a replication-competent HBV genome. However, long-term expression of HBV proteins is accompanied by production of progeny virions, thereby requiring a Biosafety Level (BSL) 3 animal facility. In the present study, we introduced a point mutation in the START codon of the HBV polymerase to develop a mouse model reflecting chronic hepatitis B infection without formation of viral progeny. We induced the mouse model by hydrodynamic injection of adeno-associated virus plasmid vector (pAAV) and minicircle plasmid (pMC) constructs into C57Bl/6 and C3H/HeN mouse strains, monitoring HBV antigens and antibodies in blood by enzyme-linked immunosorbent assay and analyzing liver expression of HBV core antigen by immunohistology. Persisting expression of viral antigens over 140 days (study endpoint) was observed only in the C3H/HeN mouse strain when using pAAV/1.2HBV-A and pMC/1.0HBV-D with pre-C and pre-S recombination sites. In addition, pAAV/1.2HBV-A in C3H/HeN sustained HBV core antigen positivity up to the study endpoint in C3H/HeN mice. Moreover, introducing the point mutation in the START codon of polymerase effectively prevented the formation of viral progeny. Our study establishes an accessible and affordable experimental paradigm for developing a robust mouse model reflecting CHB suitable for preclinical testing of anti-HBV therapeutics in a BSL2 animal facility.

Positive hepatitis B core antibody is associated with advanced fibrosis and mortality in nonalcoholic fatty liver disease

OBJECTIVE

Concomitant hepatitis B virus infection and nonalcoholic fatty liver disease (NAFLD) are relatively common, while little is known about the impact of anti-hepatitis B core antibody (anti-HBc) on NAFLD individuals. We aimed to investigate the association of positive anti-HBc with advanced fibrosis and mortality in NAFLD.

METHODS

We analyzed data from 3268 NAFLD participants who underwent abdominal ultrasonography during the Third National Health and Nutrition Examination Survey (NHANES III). The fibrosis 4 index (FIB-4) score >2.67, NAFLD fibrosis score >0.676, or aspartate aminotransferase to platelet ratio index >1.5 were defined as advanced fibrosis. All-cause and cause-specific mortality were obtained from the NHANES III-linked follow-up file through 31 December 2015.

RESULTS

A total of 242 (7.4%) patients had positive anti-HBc. Patients with positive anti-HBc had a higher percentage of advanced fibrosis than those with negative anti-HBc (12.2% vs. 5.8%). Positive anti-HBc was significantly associated with advanced fibrosis [adjusted odds ratio = 1.69, 95% confidence interval (CI), 1.05-2.72]. During a median follow-up of 22 years, the cumulative all-cause and cancer-related mortalities were higher in participants with positive anti-HBc than in their counterparts (log-rank test P < 0.001). When demographic and metabolic risk factors were considered, NAFLD cases with positive anti-HBc had a significantly higher cancer-related mortality (adjusted hazard ratio = 1.54, 95% CI, 1.05-2.25).

CONCLUSION

Our findings suggested that NAFLD cases with positive anti-HBc had higher risks for liver fibrosis and long-term mortality, justifying the medical importance of testing anti-HBc in NAFLD patients.

An Ideal Hallmark Closest to Complete Cure of Chronic Hepatitis B Patients: High-sensitivity Quantitative HBsAg Loss

In the era of antiviral therapy, the main goal of treatment has shifted from the persistent inhibition of hepatitis B virus (HBV) replication to the pursuit of serological clearance of HBs surface antigen (HBsAg). Based on the life cycle of HBV, HBsAg originates from covalently closed circular DNA (cccDNA) and integrated HBV DNA, thus reflecting their transcriptional activity. Complete HBsAg loss may mean elimination or persistent inactivity of the HBV genome including cccDNA and integrated HBV DNA. HBsAg loss improves the recovery of abnormal immune function, which in turn, may further promote the clearance of residual viruses. Combined with functional cure and the great improvement of clinical outcomes, the continuous seroclearance of high-sensitivity quantitative HBsAg may represent the complete cure of chronic hepatitis B (CHB). For many other risk factors besides HBV itself, patients with HBsAg loss still need regular monitoring. In this review, we summarized the evolution of CHB treatment, the origin of serum HBsAg, the pattern of HBsAg seroclearance, and the effect of HBsAg loss on immune function and disease outcomes. In addition, we discuss the significance of high-sensitivity HBsAg detection and its possibility as a surrogate of complete cure.

Modulation of gene expression by YTH domain family (YTHDF) proteins in human physiology and pathology

The advent of high throughput techniques in the past decade has significantly advanced the field of epitranscriptomics. The internal chemical modification of the target RNA at a specific site is a basic feature of epitranscriptomics and is critical for its structural stability and functional property. More than 170 modifications at the transcriptomic level have been reported so far, among which m6A methylation is one of the more conserved internal RNA modifications, abundantly found in eukaryotic mRNAs and frequently involved in enhancing the target messenger RNA's (mRNA) stability and translation. m6A modification of mRNAs is essential for multiple physiological processes including stem cell differentiation, nervous system development and gametogenesis. Any aberration in the m6A modification can often result in a pathological condition. The deregulation of m6A methylation has already been described in inflammation, viral infection, cardiovascular diseases and cancer. The m6A modification is reversible in nature and is carried out by specialized m6A proteins including writers (m6A methyltransferases) that add methyl groups and erasers (m6A demethylases) that remove methyl groups selectively. The fate of m6A-modified mRNA is heavily reliant on the various m6A-binding proteins ("readers") which recognize and generate a functional signal from m6A-modified mRNA. In this review, we discuss the role of a family of reader proteins, "YT521-B homology domain containing family" (YTHDF) proteins, in human physiology and pathology. In addition, we critically evaluate the potential of YTHDF proteins as therapeutic targets in human diseases.

Preclinical characterization of ABI-H2158, an HBV core inhibitor with dual mechanisms of action

The HBV core protein plays an integral role in multiple steps of the HBV lifecycle. Consequently, HBV core inhibitors interrupt multiple steps of the replication cycle, including blocking pgRNA encapsidation and prematurely disassembling existing nucleocapsids, thereby preventing them from transporting relaxed circular (rcDNA) to the nucleus for conversion to covalently closed circular DNA (cccDNA). ABI-H2158 is an HBV core inhibitor that advanced into Phase 2 clinical trials for the treatment of chronic hepatitis B virus infection (cHBV) but was discontinued due to hepatotoxicity. Here, the potency, selectivity, and mechanisms of action of ABI-H2158 were evaluated using a variety of cell-based assays. Antiviral activity was measured by quantifying intracellular or secreted HBV DNA, RNA, and antigens. ABI-H2158 inhibited HBV replication by blocking pgRNA encapsidation in induced HepAD38 cells (EC₅₀ = 22 nM) and had similar potency in HBV-infected HepG2-NTCP cells (EC₅₀ = 27 nM) and primary human hepatocytes (PHH) (EC₅₀ = 41 nM). ABI-H2158 is a pan-genotypic HBV inhibitor, with EC₅₀s ranging from 7.1 to 22 nM across HBV genotypes A-E. ABI-H2158 also potently blocked the formation of cccDNA in de novo HBV infections with EC₅₀s of ∼200 nM in HepG2-NTCP and PHH assays. These results indicate ABI-H2158 has dual mechanisms of action, inhibiting both early and late steps of the HBV replication cycle.

Characterization of a KDM5 small molecule inhibitor with antiviral activity against hepatitis B virus

Chronic hepatitis B (CHB) is a global health care challenge and a major cause of liver disease. To find new therapeutic avenues with a potential to functionally cure chronic Hepatitis B virus (HBV) infection, we performed a focused screen of epigenetic modifiers to identify potential inhibitors of replication or gene expression. From this work we identified isonicotinic acid inhibitors of the histone lysine demethylase 5 (KDM5) with potent anti-HBV activity. To enhance the cellular permeability and liver accumulation of the most potent KDM5 inhibitor identified (GS-080) an ester prodrug was developed (GS-5801) that resulted in improved bioavailability and liver exposure as well as an increased H3K4me3:H3 ratio on chromatin. GS-5801 treatment of HBV-infected primary human hepatocytes reduced the levels of HBV RNA, DNA and antigen. Evaluation of GS-5801 antiviral activity in a humanized mouse model of HBV infection, however, did not result in antiviral efficacy, despite achieving pharmacodynamic levels of H3K4me3:H3 predicted to be efficacious from the in vitro model. Here we discuss potential reasons for the disconnect between in vitro and in vivo efficacy, which highlight the translational difficulties of epigenetic targets for viral diseases.

EDP-514 in healthy subjects and nucleos(t)ide reverse transcriptase inhibitor-suppressed patients with chronic hepatitis B

Background

Chronic hepatitis B (CHB) remains a major cause of morbidity and mortality. EDP-514 is a potent core inhibitor of hepatitis B virus (HBV) that reduces viral load reduction in HBV-infected chimeric mice. This first-in-human study evaluated the safety, tolerability, and pharmacokinetics (PK) of EDP-514 in healthy subjects and antiviral activity in patients with CHB.

Methods

In Part 1, 82 subjects received placebo or EDP-514 in fed or fasted state as single ascending doses of 50–800 mg and multiple ascending doses of 200–800 mg for 14 days. In Part 2, 24 HBV DNA-suppressed, nucleos(t)ide (NUC)-treated (i.e., NUC-suppressed) CHB patients received EDP-514 200–800 mg or placebo for 28 days.

Results

EDP-514 was well tolerated in healthy subjects and CHB patients with most adverse events of mild intensity. In Part 1, EDP-514 exposure increased in an approximately dose proportional manner up to 600 mg after single doses and up to 400 mg after 14-day dosing. In Part 2, EDP-514 exposure increased linearly with dose on Day 1 and Day 28, with some accumulation for Day 28 and median trough concentrations (Ctrough) approximately 20-fold above the protein-adjusted 50% effective concentration (EC50) for the dose range. Mean change in HBV RNA from baseline to Day 28 was −2.03, −1.67, −1.87, and −0.58 log U/mL in the 200 mg, 400 mg, 800 mg, and placebo CHB groups, respectively.

Conclusions

EDP-514 was well tolerated, had a PK profile supporting once daily dosing, and reduced HBV RNA levels in NUC-suppressed CHB patients.

Ivermectin Inhibits HBV Entry into the Nucleus by Suppressing KPNA2

Hepatitis B virus (HBV) specifically infects human hepatocytes and increases the risks of cirrhosis and liver cancer. Currently, nucleic acid analogs are the main therapeutics for chronic hepatitis caused by HBV infection. Although nucleic acid analogs can eliminate HBV DNA by inhibiting HBV reverse transcriptase, they cannot lead to negative conversion of covalently closed circular DNA (cccDNA) and hepatitis B surface antigen (HBsAg). In this study, we revealed that the antifilarial drug ivermectin suppresses HBV production by a different mechanism from the nucleic acid analog entecavir or Na⁺ taurocholate co-transporting polypeptide-mediated entry inhibitor cyclosporin A. Ivermectin reduced the levels of several HBV markers, including HBsAg, in HBV-infected human hepatocellular carcinoma cells (HepG2-hNTCP-C4 cells) and humanized mouse hepatocytes (PXB hepatocytes). In addition, ivermectin significantly decreased the expression of HBV core protein and the nuclear transporter karyopherin α2 (KPNA2) in the nuclei of HepG2-hNTCP-C4 cells. Furthermore, depletion of KPNA1-6 suppressed the production of cccDNA. These results suggest that KPNA1-6 is involved in the nuclear import of HBV and that ivermectin suppresses the nuclear import of HBV by inhibiting KPNA2. This study demonstrates the potential of ivermectin as a novel treatment for hepatitis B.

Role of epigenetic modification in interferon treatment of hepatitis B virus infection

Human hepatitis B virus (HBV) is a small, enveloped DNA virus that causes acute and chronic hepatitis. Chronic hepatitis B (CHB) is associated with hepatocellular carcinoma pathogenesis. Interferons (IFNs) have been used for the treatment of CHB for a long time, with advantages including less treatment duration and sustained virological response. Presently, various evidence suggests that epigenetic modification of the viral covalently closed circular DNA (cccDNA) and the host genome is crucial for the regulation of viral activity. This modification includes histone acetylation, DNA methylation, N6-methyladenosine, and non-coding RNA modification. IFN treatment for CHB can stimulate multiple IFN-stimulated genes for inhibiting virus replication. IFNs can also affect the HBV life cycle through epigenetic modulation. In this review, we summarized the different mechanisms through which IFN-α inhibits HBV replication, including epigenetic regulation. Moreover, the mechanisms underlying IFN activity are discussed, which indicated its potential as a novel treatment for CHB. It is proposed that epigenetic changes such as histone acetylation, DNA methylation, m6A methylation could be the targets of IFN, which may offer a novel approach to HBV treatment.

APOBEC3B: Future direction of liver cancer research

Liver cancer is one of the most common cancers in the world, and the rate of liver cancer is high due to the of its illness. The main risk factor for liver cancer is infection with the hepatitis B virus (HBV), but a considerable number of genetic and epigenetic factors are also directly or indirectly involved in the underlying pathogenesis of liver cancer. In particular, the apolipoprotein B mRNA editing enzyme, catalytic peptide-like protein (APOBEC) family (DNA or mRNA editor family), which has been the focus of virology research for more than a decade, has been found to play a significant role in the occurrence and development of various cancers, providing a new direction for the research of liver cancer. APOBEC3B is a cytosine deaminase that controls a variety of biological processes, such as protein expression, innate immunity, and embryonic development, by participating in the process of cytidine deamination to uridine in DNA and RNA. In humans, APOBEC3B has long been known as a DNA editor for limiting viral replication and transcription. APOBEC3B is widely expressed at low levels in a variety of normal tissues and organs, but it is significantly upregulated in different types of tumor tissues and tumor lines. Thus, APOBEC3B has received increasing attention in various cancers, but the role of APOBEC3B in the occurrence and development of liver cancer due to infection with HBV remains unclear. This review provides a brief introduction to the pathogenesis of hepatocellular carcinoma induced by HBV, and it further explores the latest results of APOBEC3B research in the development of HBV and liver cancer, thereby providing new directions and strategies for the treatment and prevention of liver cancer.

Oligonucleotide-Based Therapies for Chronic HBV Infection: A Primer on Biochemistry, Mechanisms and Antiviral Effects

Three types of oligonucleotide-based medicines are under clinical development for the treatment of chronic HBV infection. Antisense oligonucleotides (ASOs) and synthetic interfering RNA (siRNA) are designed to degrade HBV mRNA, and nucleic acid polymers (NAPs) stop the assembly and secretion of HBV subviral particles. Extensive clinical development of ASOs and siRNA for a variety of liver diseases has established a solid understanding of their pharmacodynamics, accumulation in different tissue types in the liver, pharmacological effects, off-target effects and how chemical modifications and delivery approaches affect these parameters. These effects are highly conserved for all ASO and siRNA used in human studies to date. The clinical assessment of several ASO and siRNA compounds in chronic HBV infection in recent years is complicated by the different delivery approaches used. Moreover, these assessments have not considered the large clinical database of ASO/siRNA function in other liver diseases and known off target effects in other viral infections. The goal of this review is to summarize the current understanding of ASO/siRNA/NAP pharmacology and integrate these concepts into current clinical results for these compounds in the treatment of chronic HBV infection.

Medical Advances in Hepatitis D Therapy: Molecular Targets

An approximate number of 250 million people worldwide are chronically infected with hepatitis B virus, making them susceptible to a coinfection with hepatitis D virus. The superinfection causes the most severe form of a viral hepatitis and thus drastically worsens the course of the disease. Until recently, the only available therapy consisted of interferon-α, only eligible for a minority of patients. In July 2020, the EMA granted Hepcludex conditional marketing authorization throughout the European Union. This first-in-class entry inhibitor offers the promise to prevent the spread in order to gain control and eventually participate in curing hepatitis B and D. Hepcludex is an example of how understanding the viral lifecycle can give rise to new therapy options. Sodium taurocholate co-transporting polypeptide, the virus receptor and the target of Hepcludex, and other targets of hepatitis D therapy currently researched are reviewed in this work. Farnesyltransferase inhibitors such as Lonafarnib, targeting another essential molecule in the HDV life cycle, represent a promising target for hepatitis D therapy. Farnesyltransferase attaches a farnesyl (isoprenyl) group to proteins carrying a C-terminal Ca1a2X (C: cysteine, a: aliphatic amino acid, X: C-terminal amino acid) motif like the large hepatitis D virus antigen. This modification enables the interaction of the HBV/HDV particle and the virus envelope proteins. Lonafarnib, which prevents this envelopment, has been tested in clinical trials. Targeting the lifecycle of the hepatitis B virus needs to be considered in hepatitis D therapy in order to cure a patient from both coexisting infections. Nucleic acid polymers target the hepatitis B lifecycle in a manner that is not yet understood. Understanding the possible targets of the hepatitis D virus therapy is inevitable for the improvement and development of a sufficient therapy that HDV patients are desperately in need of.

Rapamycin inhibits hepatitis B virus covalently closed circular DNA transcription by enhancing the ubiquitination of HBx

Hepatitis B virus (HBV) infection is still a serious public health problem worldwide. Antiviral therapies such as interferon and nucleos(t)ide analogs efficiently control HBV replication, but they cannot eradicate chronic hepatitis B (CHB) because of their incapacity to eliminate endocellular covalently closed circular DNA (cccDNA). Thus, there is a necessity to develop new strategies for targeting cccDNA. As cccDNA is difficult to clear, transcriptional silencing of cccDNA is a possible effective strategy. HBx plays a vitally important role in maintaining the transcriptional activity of cccDNA and it could be a target for blocking the transcription of cccDNA. To screen new drugs that may contribute to antiviral therapy, the ability of 2,000 small-molecule compounds to inhibit HBx was examined by the HiBiT lytic detection system. We found that the macrolide compound rapamycin, which is clinically used to prevent acute rejection after organ transplantation, could significantly reduce HBx protein expression. Mechanistic studies demonstrated that rapamycin decreased the stability of the HBx protein by promoting its degradation via the ubiquitin-proteasome system. Moreover, rapamycin inhibited HBV RNA, HBV DNA, and cccDNA transcription levels in HBV-infected cells. In addition, HBx deficiency abrogated the inhibition of cccDNA transcription induced by rapamycin. Similar results were also confirmed in a recombinant cccDNA mouse model. In summary, we report a new small-molecule, rapamycin, which targets HBx to block HBV cccDNA transcription and inhibit HBV replication. This approach can identify new strategies to cure CHB.

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.

The RNA-Binding Protein ELAVL1 Regulates Hepatitis B Virus Replication and Growth of Hepatocellular Carcinoma Cells

Previous RNA immunoprecipitation followed by proteomic approaches successfully demonstrated that Embryonic Lethal, Abnormal Vision, Drosophila-Like 1 (ELAVL1) interacts with hepatitis B virus (HBV)-derived RNAs. Although ELAVL family proteins stabilize AU-rich element (ARE)-containing mRNAs, their role in HBV transcription remains unclear. This study conducted loss-of-function assays of ELAVL1 for inducible HBV-replicating HepAD38 cells and HBx-overexpressed HepG2 cells. In addition, clinicopathological analyses in primary hepatocellular carcinoma (HCC) surgical samples were also conducted. Lentivirus-mediated short hairpin RNA knockdown of ELAVL1 resulted in a decrease in both viral RNA transcription and production of viral proteins, including HBs and HBx, probably due to RNA stabilization by ELAVL1. Cell growth of HepAD38 cells was more significantly impaired in ELAVL1-knockdown than those in the control group, with or without HBV replication, indicating that ELAVL1 is involved in proliferation by factors other than HBV-derived RNAs. Immunohistochemical analyses of 77 paired HCC surgical specimens demonstrated that diffuse ELAVL1 expression was detected more frequently in HCC tissues (61.0%) than in non-tumor tissues (27.3%). In addition, the abundant expression of ELAVL1 tended to affect postoperative recurrence in HBV-related HCC patients. In conclusion, ELAVL1 contributes not only to HBV replication but also to HCC cell growth. It may be a potent therapeutic target for HBV-related HCC treatment.

Occult Hepatitis B Virus Infection: An Update

Occult hepatitis B virus (HBV) infection (OBI) refers to a condition in which replication-competent viral DNA is present in the liver (with detectable or undetectable HBV DNA in the serum) of individuals testing negative for the HBV surface antigen (HBsAg). In this peculiar phase of HBV infection, the covalently closed circular DNA (cccDNA) is in a low state of replication. Many advances have been made in clarifying the mechanisms involved in such a suppression of viral activity, which seems to be mainly related to the host's immune control and epigenetic factors. OBI is diffused worldwide, but its prevalence is highly variable among patient populations. This depends on different geographic areas, risk factors for parenteral infections, and assays used for HBsAg and HBV DNA detection. OBI has an impact in several clinical contexts: (a) it can be transmitted, causing a classic form of hepatitis B, through blood transfusion or liver transplantation; (b) it may reactivate in the case of immunosuppression, leading to the possible development of even fulminant hepatitis; (c) it may accelerate the progression of chronic liver disease due to different causes toward cirrhosis; (d) it maintains the pro-oncogenic properties of the "overt" infection, favoring the development of hepatocellular carcinoma.

Arthrospira Enhances Seroclearance in Patients with Chronic Hepatitis B Receiving Nucleos(t)ide Analogue through Modulation of TNF-α/IFN-γ Profile

Chronic hepatitis B (CHB) virus infection, causing immune dysfunction and chronic hepatitis, is one of the leading risk factors for hepatocellular cancer. We investigated how Arthrospira affected hepatitis B surface antigen (HBsAg) reduction in CHB patients under continued nucleos(t)ide analogues (NA). Sixty CHB patients who had been receiving NA for at least one year with undetectable HBV DNA were randomized into three groups: control and oral Arthrospira at 3 or 6 g daily add-on therapy groups. Patients were followed up for 6 months. Oral Arthrospira-diet mice were established to investigate the possible immunological mechanism of Arthrospira against HBV. Within 6 months, mean quantitative HBsAg (qHBsAg) decreased in the oral Arthrospira add-on therapy group. Interestingly, interferon gamma (IFN-γ) increased but TNF-α, interleukin 6 (IL-6), hepatic fibrosis, and steatosis decreased in the add-on groups. In mice, Arthrospira enhanced both innate and adaptive immune system, especially natural killer (NK) cell cytotoxicity, B cell activation, and the interleukin 2 (IL-2), IFN-γ immune response. Arthrospira may modulate IL-2- and TNF-α/IFN-γ-mediated B and T cell activation to reduce HBsAg. Also, Arthrospira has the potential to restore immune tolerance and enhance HBsAg seroclearance in CHB patients through promoting T, B, and NK cell activation.

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.

Hepatitis B virus X protein counteracts high mobility group box 1 protein-mediated epigenetic silencing of covalently closed circular DNA

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), serving as the viral persistence form and transcription template of HBV infection, hijacks host histone and non-histone proteins to form a minichromosome and utilizes posttranslational modifications (PTMs) "histone code" for its transcriptional regulation. HBV X protein (HBx) is known as a cccDNA transcription activator. In this study we established a dual system of the inducible reporter cell lines modelling infection with wildtype (wt) and HBx-null HBV, both secreting HA-tagged HBeAg as a semi-quantitative marker for cccDNA transcription. The cccDNA-bound histone PTM profiling of wt and HBx-null systems, using chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR), confirmed that HBx is essential for maintenance of cccDNA at transcriptionally active state, characterized by active histone PTM markers. Differential proteomics analysis of cccDNA minichromosome established in wt and HBx-null HBV cell lines revealed group-specific hits. One of the hits in HBx-deficient condition was a non-histone host DNA-binding protein high mobility group box 1 (HMGB1). Its elevated association to HBx-null cccDNA was validated by ChIP-qPCR assay in both the HBV stable cell lines and infection systems in vitro. Furthermore, experimental downregulation of HMGB1 in HBx-null HBV inducible and infection models resulted in transcriptional re-activation of the cccDNA minichromosome, accompanied by a switch of the cccDNA-associated histones to euchromatic state with activating histone PTMs landscape and subsequent upregulation of cccDNA transcription. Mechanistically, HBx interacts with HMGB1 and prevents its binding to cccDNA without affecting the steady state level of HMGB1. Taken together, our results suggest that HMGB1 is a novel host restriction factor of HBV cccDNA with epigenetic silencing mechanism, which can be counteracted by viral transcription activator HBx.

IFN-α inhibits HBV transcription and replication by promoting HDAC3-mediated de-2-hydroxyisobutyrylation of histone H4K8 on HBV cccDNA minichromosome in liver

The epigenetic modification of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a crucial role in cccDNA transcription and viral persistence. Interferon-α (IFN-α) is a pivotal agent against HBV cccDNA. However, the mechanism by which IFN-α modulates the epigenetic regulation of cccDNA remains poorly understood. In this study, we report that IFN-α2b enhances the histone deacetylase 3 (HDAC3)-mediated de-2-hydroxyisobutyrylation of histone H4 lysine 8 (H4K8) on HBV cccDNA minichromosome to restrict the cccDNA transcription in liver. By screening acetyltransferases and deacetylases, we identified that HDAC3 was an effective restrictor of HBV transcription and replication. Moreover, we found that HDAC3 was able to mediate the de-2-hydroxyisobutyrylation of H4K8 in HBV-expressing hepatoma cells. Then, the 2-hydroxyisobutyrylation of histone H4K8 (H4K8hib) was identified on the HBV cccDNA minichromosome, promoting the HBV transcription and replication. The H4K8hib was regulated by HDAC3 depending on its deacetylase domain in the system. The low level of HDAC3 and high level of H4K8hib were observed in the liver tissues from HBV-infected human liver-chimeric mice. The levels of H4K8hib on HBV cccDNA minichromosome were significantly elevated in the liver biopsy specimens from clinical hepatitis B patients, which was consistent with the high transcriptional activity of cccDNA. Strikingly, IFN-α2b effectively facilitated the histone H4K8 de-2-hydroxyisobutyrylation mediated by HDAC3 on the HBV cccDNA minichromosome in primary human hepatocytes and hepatoma cells, leading to the inhibition of HBV transcription and replication. Our finding provides new insights into the mechanism by which IFN-α modulates the epigenetic regulation of HBV cccDNA minichromosome.

Role of hepatitis B virus in development of hepatocellular carcinoma: Focus on covalently closed circular DNA

Chronic infection with hepatitis B virus (HBV) remains a major global health problem, especially in developing countries. It may lead to prolonged liver damage, fibrosis, cirrhosis, and hepatocellular carcinoma. Persistent chronic HBV infection is related to host immune response and the stability of the covalently closed circular DNA (cccDNA) in human hepatocytes. In addition to being essential for viral transcription and replication, cccDNA is also suspected to play a role in persistent HBV infections or hepatitis relapses since cccDNA is very stable in non-dividing human hepatocytes. Understanding the pathogenicity and oncogenicity of HBV components would be essential in the development of new diagnostic tools and treatment strategies. This review summarizes the role and molecular mechanisms of HBV cccDNA in hepatocyte transformation and hepatocarcinogenesis and current efforts to its detection and targeting.

Occult hepatitis B virus infection in hepatitis C virus negative chronic liver diseases

Data concerning the prevalence of hepatitis B virus (HBV) occult infection (OBI) varies greatly in the different studies according to the sensitivity and specificity of the diagnostic approaches and the HBV prevalence in the different populations examined. The clinical implications of OBI are still debated. While the impact of OBI in HBV transmission as well as in HBV reactivation under immunosuppression are well established, the role of OBI in liver disease and hepatocellular carcinoma (HCC) development are still not definitively elucidated. It has been hypothesized that OBI might contribute to worsening the liver disease course when other causes of liver damage co-exist. Furthermore, much evidence suggests a role of OBI in the hepato-carcinogenesis processes through both indirect and direct oncogenic mechanisms that might favour HCC development. Data on the OBI clinical implications mainly come from studies performed in patients with hepatitis C virus (HCV) infection. However, HCV prevalence has dramatically fallen in the past years also because of the advent of specific and highly effective direct acting antivirals, with a consequent abrupt change of the worldwide scenario of chronic liver disease. Information about OBI prevalence and possible clinical impact in non-HCV-related liver disease are fragmentary, and the objective of this review is to critically summarize the available data in this field.

PRKDC promotes hepatitis B virus transcription through enhancing the binding of RNA Pol II to cccDNA

Hepatitis B virus infection remains a major health problem worldwide due to its high risk of liver failure and hepatocellular carcinoma. Covalently closed circular DNA (cccDNA), which is present as an individual minichromosome, serves as the template for transcription of all viral RNAs and pla ays critical role in viral persistence. Therefore, there is an urgent need to gain broader insight into the transcription regulation of cccDNA. Here, we combined a modified Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) with an engineered ascorbate peroxidase 2 (APEX2) to identify cccDNA associated proteins systematically in living cells. By functional screening, we verified that protein kinase, DNA-activated, catalytic subunit (PRKDC) was an effective activator of HBV cccDNA transcription in HBV-infected HepG2-NTCP cells and primary human hepatocytes. Mechanismly, PRKDC interacted with POLR2A and POLR2B, the two largest subunits of RNA polymerase II (Pol II) and recruited Pol II to HBV cccDNA minichromosome in a kinase-dependent manner. PRKDC knockdown or inhibitor treatment significantly decreased the enrichment of POLR2A and POLR2B on cccDNA, as well as reducing the levels of cccDNA associated Pol II Ser5 and Ser2 phosphorylation, which eventually inhibited the HBV cccDNA activity. Collectively, these findings give us new insights into cccDNA transcription regulation, thus providing new potential targets for HBV treatment in patients.

HIV-1-Mediated Acceleration of Oncovirus-Related Non-AIDS-Defining Cancers

With the advent of combination antiretroviral therapy (cART), overall survival has been improved, and the incidence of acquired immunodeficiency syndrome (AIDS)-defining cancers has also been remarkably reduced. However, non-AIDS-defining cancers among human immunodeficiency virus-1 (HIV-1)-associated malignancies have increased significantly so that cancer is the leading cause of death in people living with HIV in certain highly developed countries, such as France. However, it is currently unknown how HIV-1 infection raises oncogenic virus-mediated cancer risks in the HIV-1 and oncogenic virus co-infected patients, and thus elucidation of the molecular mechanisms for how HIV-1 expedites the oncogenic viruses-triggered tumorigenesis in the co-infected hosts is imperative for developing therapeutics to cure or impede the carcinogenesis. Hence, this review is focused on HIV-1 and oncogenic virus co-infection-mediated molecular processes in the acceleration of non-AIDS-defining cancers.

Anti-rheumatic drug-induced hepatitis B virus reactivation and preventive strategies for hepatocellular carcinoma

To date, an estimated 3 million people worldwide have been infected with chronic hepatitis B virus (HBV). Although anti-HBV therapies have improved the long-term survival profile of chronic carriers, viral reactivation still poses a significant challenge for preventing HBV-related hepatitis, hepatocellular carcinoma (HCC), and death. Immuno-modulating drugs, which are widely applied in managing rheumatic conditions, are commonly associated with HBV reactivation (HBVr) as a result of drug-induced immune suppression. However, there are few reports on the risk of HBVr and the medication management plan for HBV carriers, especially rheumatic patients. In this review, we summarize immuno-modulating drug-induced HBVr during rheumatoid therapy and its preventive strategies for HBVr-induced liver diseases, especially cirrhosis and HCC. These findings will assist with developing treatments for rheumatic patients, and prevent HBV-related cirrhosis and HCC.

The N6-Methyladenosine Modification and Its Role in mRNA Metabolism and Gastrointestinal Tract Disease

The N6-methyladenosine (m6A) modification is the most abundant internal modification of messenger RNA (mRNA) in higher eukaryotes. Under the actions of methyltransferase, demethylase and methyl-binding protein, m6A resulting from RNA methylation becomes dynamic and reversible, similar to that from DNA methylation, and this effect allows the generated mRNA to participate in metabolism processes, such as splicing, transport, translation, and degradation. The most common tumors are those found in the gastrointestinal tract, and research on these tumors has flourished since the discovery of m6A. Overall, further analysis of the mechanism of m6A and its role in tumors may contribute to new ideas for the treatment of tumors. m6A also plays an important role in non-tumor diseases of the gastrointestinal tract. This manuscript reviews the current knowledge of m6A-related proteins, mRNA metabolism and their application in gastrointestinal tract disease.

Type-III interferon stimulated gene TRIM31 mutation in an HBV patient blocks its ability in promoting HBx degradation

TRIM5γ, together with TRIM31, has been shown to promote HBx ubiquitination and degradation. This study aimed to explore whether a patient with HCC (hepatic cell carcinoma) having a small nucleotide inserted into the TRIM31 gene, which made a shorter transcript stop at 768 bp, would result in blocking the activity of TRIM31 in promoting HBx degradation. Besides, this study aimed to determine the binding region of the TRIM31-TRIM5γ-HBx complex. HBV (Hepatitis B virus) infection was reported to induce type-III IFN but not type-I or type-II IFNs, here TRIM31 was found to be a type III rather than a type I stimulated gene, which was indispensable in inhibiting the hepatitis B virus replication by the interferon families. Thus, this study further identified the critical role of TRIM31 in the host-hepatitis B virus interaction.

OUP accepted manuscript

Chronic infection with hepatitis B virus (HBV) is associated with liver cirrhosis and hepatocellular carcinoma. Upon infection of hepatocytes, HBV covalently closed circular DNA (cccDNA) exists as histone-bound mini-chromosome, subjected to transcriptional regulation similar to chromosomal DNA. Here we identify high mobility group AT-hook 1 (HMGA1) protein as a positive regulator of HBV transcription that binds to a conserved ATTGG site within enhancer II/core promoter (EII/Cp) and recruits transcription factors FOXO3α and PGC1α. HMGA1-mediated upregulation of EII/Cp results in enhanced viral gene expression and genome replication. Notably, expression of endogenous HMGA1 was also demonstrated to be upregulated by HBV, which involves HBV X protein (HBx) interacting with SP1 transcription factor to activate HMGA1 promoter. Consistent with these in vitro results, chronic hepatitis B patients in immune tolerant phase display both higher intrahepatic HMGA1 protein levels and higher serum HBV markers compared to patients in inactive carrier phase. Finally, using a mouse model of HBV persistence, we show that targeting endogenous HMGA1 through RNA interference facilitated HBV clearance. These data establish HMGA1 as an important positive regulator of HBV that is reciprocally upregulated by HBV via HBx and also suggest the HMGA1-HBV positive feedback loop as a potential therapeutic target.

Pharmacological perspectives and molecular mechanisms of coumarin derivatives against virus disease

Infections caused by viruses are one of the foremost causes of morbidity and mortality in the world. Although a number of antiviral drugs are currently used for treatment of various kinds of viral infection diseases, there is still no available therapeutic agent for most of the viruses in clinical practice. Coumarin is a chemical compound which is found naturally in a variety of plants, it can also be synthetically produced possessing diverse biological effects. More recently, reports have highlighted the potential role of coumarin derivatives as antiviral agents. This review outlines the advances in coumarin-based compounds against various viruses including human immunodeficiency virus, hepatitis virus, herpes simplex virus, Chikungunya virus and Enterovirus 71, as well as the structure activity relationship and the possible mechanism of action of the most potent coumarin derivatives.

Efficacy and Safety of Hepatitis B Virus Vaccination Following Hepatitis B Immunoglobulin Withdrawal After Liver Transplantation

BACKGROUND

Hepatitis B immunoglobulin (HBIG) and oral nucleoside/nucleotide analogs have been the mainstay of hepatitis B virus (HBV) prophylaxis after liver transplantation. However, long-term HBIG administration could have disadvantages, such as an increase in medical costs and the development of mutant HBV strains. This study aimed to investigate the safety and efficacy of HBV vaccination after the withdrawal of HBIG after liver transplantation.

METHODS

This prospective open-label single-arm observational clinical trial enrolled 41 patients who underwent liver transplantation between 2010 and 2016 because of a condition related to chronic HBV infection. At the time of enrollment, all patients had taken entecavir and discontinued HBIG administration. When hepatitis B surface antibody titer was undetectable after the withdrawal of HBIG, a recombinant HBV vaccine was injected intramuscularly at month 0, 1, and 6.

RESULTS

After excluding 5 patients who dropped out and 2 patients who had a persistent hepatitis B surface antibody titer, 9 (26.5%) of 34 patients had a positive vaccination response. The median hepatitis B surface antibody titer at seroconversion was 86 (12-1000) IU/L, and those at the end of follow-up were 216 (30-1000) IU/L. No patients experienced HBV recurrence during the study period. Sex (female, odds ratio 32.91 [1.83-592.54], P = .018) and the dosing interval of HBIG before withdrawal (≥90 days, 16.21 [1.21-217.31], P = .035) were independent contributing factors for positive response to the vaccination.

CONCLUSION

HBV vaccination still deserves consideration as active immunoprophylaxis after liver transplantation because it could provide added immunity to nucleoside/nucleotide analogs monotherapy with excellent cost-effectiveness.

Novel Therapies That May Cure Chronic Hepatitis B Virus

The hepatitis B virus (HBV) is a member of the Hepadnaviridae family, which includes small DNA enveloped viruses that infect primates, rodents, and birds and is the causative factor of chronic hepatitis B. A common feature of all these viruses is their great specificity by species and cell type, as well as a peculiar genomic and replication organization similar to that of retroviruses. The HBV virion consists of an external lipid envelope and an internal icosahedral protein capsid containing the viral genome and a DNA polymerase, which also functions as a reverse transcriptase.

Approaches to quantifying Hepatitis B Virus covalently closed circular (ccc)DNA

Chronic hepatitis B is a major cause of liver disease worldwide and is currently incurable. Hepatitis B virus (HBV) covalently closed circular (ccc) DNA is a key form of the virus responsible for its persistence and is the transcriptional template for all viral transcripts. The field is focussed on methods to clear HBV cccDNA but this been limited by technical difficulties in its quantification due to: identical sequence to other forms of HBV DNA; low copy number per cell; and high resistance to denaturation by heat, leading to difficulty using polymerase chain reaction or hybridization methods for detection. A number of assays have been developed in order to overcome these hurdles either directly or detecting cccDNA levels indirectly via its transcriptional products. In this review, we summarize the approaches to cccDNA quantification that are currently used, and outline key open questions in the cccDNA biology field which remain to be answered due to the limitations of current methods.

The Hepatitis B Virus Interactome: A Comprehensive Overview

Despite the availability of a prophylactic vaccine, chronic hepatitis B (CHB) caused by the hepatitis B virus (HBV) is a major health problem affecting an estimated 292 million people globally. Current therapeutic goals are to achieve functional cure characterized by HBsAg seroclearance and the absence of HBV-DNA after treatment cessation. However, at present, functional cure is thought to be complicated due to the presence of covalently closed circular DNA (cccDNA) and integrated HBV-DNA. Even if the episomal cccDNA is silenced or eliminated, it remains unclear how important the high level of HBsAg that is expressed from integrated HBV DNA is for the pathology. To identify therapies that could bring about high rates of functional cure, in-depth knowledge of the virus' biology is imperative to pinpoint mechanisms for novel therapeutic targets. The viral proteins and the episomal cccDNA are considered integral for the control and maintenance of the HBV life cycle and through direct interaction with the host proteome they help create the most optimal environment for the virus whilst avoiding immune detection. New HBV-host protein interactions are continuously being identified. Unfortunately, a compendium of the most recent information is lacking and an interactome is unavailable. This article provides a comprehensive review of the virus-host relationship from viral entry to release, as well as an interactome of cccDNA, HBc, and HBx.