Antiviral strategies to eliminate hepatitis B virus covalently closed circular DNA (cccDNA)

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.

STAT4 genetic polymorphism significantly affected HBeAg seroconversion in HBeAg-positive chronic hepatitis B patients receiving Peginterferon-α therapy: A prospective cohort study in China Running title: STAT4 variation affecting response to PegIFN-α therapy

AIM

Variant in STAT4 was reported to correlate with response of IFN-α in a retrospective study in HBeAg-positive chronic hepatitis B (CHB) patients. Here we conducted a prospective study to analyze the effect of STAT4 genetic polymorphism on response of PegIFN-α-2a in HBeAg-positive patients.

METHOD

A prospective, multi-center, open-label, paralleled cohort study was performed. 150 treat-naïve and 156 nucleos(t)ide analogues (NAs)-experienced HBeAg-positive CHB patients were enrolled respectively. All patients received PegIFN-α-2a treatment for 48 weeks and 24-week follow-up post PegIFN-α-2a treatment. Before treatment, STAT4 genetic polymorphism were determined by PCR and DNA sequencing. Serological markers, serum HBV DNA level and adverse events were collected at each visit point.

RESULT

We observed a larger reduction of HBV DNA load and significant higher HBeAg seroconversion rate in GT/TT than in GG group at week 72 (P = 0.002 and P = 0.023) in treat-naïve patients. In NAs-experienced patients, the HBeAg seroconversion rate in GT/TT group was higher than in GG group at week 72 (P = 0.005). STAT4 rs7574865 gene polymorphism was the strongest independent predictor for HBeAg seroconversion in both two paralleled cohorts. Also, patients in GT/TT group had higher HBsAg loss rate than in GG group in the study. There was no significant difference in adverse events between GG and GT/TT groups.

CONCLUSION

This prospective cohort study confirmed that STAT4 rs7574865 polymorphism is associated with HBeAg seroconversion and HBsAg loss irrespective of naïve and NAs-experienced HBeAg-positive CHB patients treated with PegIFN-α-2a. This article is protected by copyright. All rights reserved.

Hepatitis B virus core-related antigen (HBcrAg) as a prognostic marker for the development of hepatocellular carcinoma: A mini systematic review of the literature

Chronic hepatitis B (CHB) infection is a risk factor for hepatocellular carcinoma (HCC). Previous studies showed that elevated levels of Hepatitis B Virus (HBV) DNA and HBsAg are associated with increased HCC risk in patients with chronic HBV infection. Multiple studies showed that high levels of HBV DNA and Hepatitis B Surface Antigen (HBsAg) are associated with higher HCC risk in CHB patients. Patients treated with antiviral therapy may have undetectable or low levels of HBV DNA and HBsAg loss. However, HCC may develop in some patients with low-level HBV DNA and HBsAg seroconversion. In this study, we evaluated the role of HBcrAg in predicting HBV related HCC development. We searched PubMed, Scopus, and Web of Science databases using keywords (hepatitis B core-related antigen, hepatocellular carcinoma, liver neoplasm, hepatocellular and hepatic cancer, to identify studies assessing serum level of HBcrAg in patients with CHB and HCC. The search resulted in 184 studies. Seven studies were included: Four of which were retrospective cohort studies, and the rest were prospective cohort, case controls. Six of them reported a higher HBcrAg positivity rate in the HCC group when compared with the HBV DNA assay, yet with similar hazard ratio (HR) in predicting the incidence of HCC. However, four studies found that HBcrAg positivity was an independent risk factor for HCC development with a HR ranging from 3.27 to 7.05. HBV-related HCC has many proposed biomarkers in its prediction, yet our findings revealed HBcrAg to may have superiority over other biomarkers. High quality studies with bigger sample size research is needed to understand the potential role of HBcrAg in CHB induced HCC.

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.

STAT3-Dependent Gene TRIM5γ Interacts With HBx Through a Zinc Binding Site on the BBox Domain

Owing to its broad-spectrum antivirus activities, interferon (IFN) is an important alternative agent for use in the treatment of hepatitis B virus (HBV)-infected patients; however, the mechanism involved in the inhibition of HBV infection and replication by IFN remains unclear. We previously reported that the induction of TRIM5γ is important in the IFN treatment of HBV patients as it promotes the degradation of the HBx protein, while the manner in which TRIM5γ is induced by IFN and how TRIM5γ interacts with HBx remain unestablished until date. Our present findings confirmed the TRIM5γ-HBx-DDB1 interactions in the HBV-infected Primary human hepatocytes (PHH), and we further found that STAT3, and not STAT1, was responsible for the induction of TRIM5γ upon IFN stimulation and that the zinc binding site His123 on the BBOX domain was a decisive site in the interaction between TRIM5γ BBOX and HBx. In addition, based on the BBOX domain, we detected a 7-amino acid peptide with the potential of promoting HBx degradation and inhibiting HBV replication. On the other hand, we noted that the TRIM5γ expression was inhibited by HBV in chronically HBV infected patients. Thus, our study identified the crucial role of STAT3 in the induction of TRIM5γ, as well as proposed a 7-amino acid, small peptide as a potential candidate for the development of therapeutic agents targeting HBx.

Long-Term Traditional Chinese Medicine Combined with NA Antiviral Therapy on Cirrhosis Incidence in Chronic Hepatitis B Patients in the Real-World Setting: A Retrospective Study

Objective

To evaluate the impact of long-term Traditional Chinese Medicine (TCM) syndrome differentiation combined with antiviral therapy with Nucleos (t) ide analogues (NAs) on the incidence of cirrhosis in patients with chronic hepatitis B.

Methods

This retrospective cohort study included 521 patients with chronic hepatitis B who underwent a treatment course of ≥3 years from 1998–2019. Of the 521 patients, 261 were defined as TCM users while 260 were TCM nonusers (control group). All the enrolled subjects were followed up until February 2019 to measure the incidence and hazard ratio (HR) of cirrhosis, and the Cox proportional hazards regression model was used to analyze the independent factors affecting the occurrence of cirrhosis.

Results

The cumulative incidence of TCM users and nonusers was 6.9% and 13.5%, respectively (P=0.013). Results of the Kaplan–Meier analysis demonstrated that TCM users had a significantly lower cumulative incidence of cirrhosis than TCM nonusers (P=0.011), and TCM users had a significantly lower liver cirrhosis risk than TCM nonusers (adjusted HR = 0.416, 95% CI, 0.231–0.749). The histological evaluation revealed improved fibrosis in 45.0% of TCM users and 11.1% of TCM nonusers (P=0.033). The analysation of the prescriptions including total 119 single Chinese herbs medicinal demonstrated that “replenish qi and fortify the spleen,” “clear heat and dispel dampness,” and “soothe the liver and regulate qi” are the main treatment methods of TCM for CHB.

Conclusions

Our study demonstrated that long-term TCM use may attenuate liver cirrhosis risk in patients with chronic hepatitis B (CHB).

Chinese herbal medicine combined with entecavir to reduce the off-therapy recurrence risk in HBeAg-positive chronic hepatitis B patients: a multicener, double-blind, randomized controlled trial in China

Background

Nucleos(t)ide analogues (NAs) are the first-line option against chronic hepatitis B (CHB). NAs produce potent suppression of viral replication with a small chance of HBsAg seroclearance and a high risk of virological relapse after discontinuation. The combined therapy of NAs plus traditional Chinese medicine (TCM) is widely accepted and has been recognized as a prospective alternative approach in China. Based on preliminary works, this study was designed to observe the therapeutic effect of TCM plus entecavir (ETV) against HBeAg-positive chronic hepatitis B with respect to reducing the recurrence risk after NA withdrawal.

Methods/design

The study is a nationwide, multicenter, double-blind, randomized, placebo-controlled trial with a duration of 120 weeks. A total of 18 hospitals and 490 eligible Chinese HBeAg-positive CHB patients will be enrolled and randomly allocated into the experimental group and control group in a 1:1 ratio. Patients in the experimental group will be prescribed TCM formulae (Tiaogan-BuXu-Jiedu granules) plus ETV 0.5 mg per day for consolidation therapy for 96 weeks. Patients in the control group will be prescribed TCM granule placebo plus ETV 0.5 mg per day for the same course. After consolidation therapy, all patients will discontinue their trial drugs and be closely monitored over the next 24 weeks. Once clinical recurrence (CR) occurs, ETV treatment will be restarted. The primary outcome is the cumulative rate of CR at the end of this trial.

Conclusion

This study is the first of its kind to observe therapeutic effects with respect to reducing recurrence after NA withdrawals after unified integrative consolidation therapy in the CHB population.

Trial registration

Chinese Clinical Trial Registry No. ChiCTR1900021232. Registered on February 2, 2019

A novel recombinant cccDNA-based mouse model with long term maintenance of rcccDNA and antigenemia

The covalently closed circular DNA (cccDNA) of hepatitis B virus (HBV) is critical for viral persistence in vivo. The lack of reliable, characterized and convenient small animal models for studying cccDNA persistence has long been a bottleneck for basic and translational research on HBV cure. A mouse model that can maintain intrahepatic cccDNA is urgently needed. Through combining the Cre/loxP-mediated recombination and adeno-associated virus (AAV) vector delivery strategy, we establish a novel recombinant cccDNA (rcccDNA) mouse model. AAV-rcccDNA mice supported long-term maintenance of intrahepatic rcccDNA which could be easily detected by Southern blotting within 30 weeks after transduction. Quantitative PCR could detect the rcccDNA signal throughout the experiment duration (>51 weeks). Furthermore, rcccDNA supported persistent serum antigenemia (>72 weeks) and intrahepatic HBsAg and HBcAg expression (>51 weeks). Flow cytometry analysis and single-cell RNA sequencing showed that AAV-rcccDNA mice displayed a compromised CD8⁺ T cell response. Meanwhile, minimal intrahepatic inflammation and fibrosis were observed. Furthermore, three anti-HBV compounds, AKEX0007, a post-transcriptional inhibitor, Bay 41-4109, a capsid allosteric modulator, and Entecavir were assessed in this AAV-rcccDNA mouse model. The changes of viral markers by these drugs were consistent with their mode of action although neither of them diminished the level of rcccDNA. This mouse model recapitulated the immune tolerant state of HBV infection with long term maintenance of cccDNA and antigenemia, which will provide a suitable platform for studying cccDNA persistence and developing intervention strategies that would eventually break the tolerance and clear the virus.

A Telomerase-Derived Peptide Exerts an Anti-Hepatitis B Virus Effect via Mitochondrial DNA Stress-Dependent Type I Interferon Production

Previously, a telomerase-derived 16-mer peptide, GV1001, developed as an anticancer vaccine, was reported to exert antiviral effects on human immunodeficiency virus or hepatitis C virus in a heat shock protein-dependent manner. Here we investigated whether GV1001 exerts antiviral effects on hepatitis B virus (HBV) and elucidated its underlying mechanisms. GV1001 inhibited HBV replication and hepatitis B surface antigen (HBsAg) secretion in a dose-dependent manner, showing synergistic antiviral effects with nucleos(t)ide analogs (NAs) including entecavir and lamivudine. This peptide also inhibited viral cccDNA and pgRNA. The intravenous GV1001 treatment of transgenic mice had anti-HBV effects. Our mechanistic studies revealed that GV1001 suppresses HBV replication by inhibiting capsid formation via type I interferon-mediated induction of heme oxygenase-1 (HO-1). GV1001 promoted the mitochondrial DNA stress-mediated release of oxidized DNA into the cytosol, resulting in IFN-I-dependent anti-HBV effects via the STING-IRF3 axis. We found that the anti-HBV effect of GV1001 was due to its ability to penetrate into the cytosol via extracellular heat shock protein, leading to phagosomal escape-mediated mtDNA stress. We demonstrated that the cell-penetrating and cytosolic localization capacity of GV1001 results in antiviral effects on HBV infections via mtDNA stress-mediated IFN-I production. Thus, GV1001, a peptide proven to be safe for human use, may be an anti-HBV drug that can be synergistically used with nucleot(s)ide analog.

Type-I-IFN-Stimulated Gene TRIM5γ Inhibits HBV Replication by Promoting HBx Degradation

To understand the molecular mechanisms that mediate the anti-hepatitis B virus (HBV) effect of interferon (IFN) therapy, we conduct high-throughput bimolecular fluorescence complementation screening to identify potential physical interactions between the HBx protein and 145 IFN-stimulated genes (ISGs). Seven HBx-interacting ISGs have consistent and significant inhibitory effects on HBV replication, among which TRIM5γ suppresses HBV replication by promoting K48-linked ubiquitination and degradation of the HBx protein on the K95 ubiquitin site. The B-Box domain of TRIM5γ under overexpression conditions is sufficient to trigger HBx degradation and is responsible both for interacting with HBx and recruiting TRIM31, which is an ubiquitin ligase that triggers HBx ubiquitination. High expression levels of TRIM5γ in IFN-α-treated HBV patients might indicate a better therapeutic effect. Thus, our studies identify a crucial role for TRIM5γ and TRIM31 in promoting HBx degradation, which may facilitate the development of therapeutic agents for the treatment of patients with IFN-resistant HBV infection.

Host genetic background affects the course of infection and treatment response in patients with chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) utilizes proteins encoded by the host to infect hepatocytes and replicate. Recently, several novel host factors have been identified and described as important to the HBV lifecycle. The influence of host genetic background on chronic hepatitis B (CHB) pathogenesis is still poorly understood.

OBJECTIVES

Here, we aimed to investigate the association of NTCP, FXRα, HNF1α, HNF4α, and TDP2 genetic polymorphisms with the natural course of CHB and antiviral treatment response.

STUDY DESIGN

We genotyped 18 single-nucleotide polymorphisms using MALDI-TOF mass spectrometry in 136 patients with CHB and 100 healthy individuals. We investigated associations of the selected polymorphisms with biochemical, serological and hepatic markers of disease progression and treatment response.

RESULTS

No significant differences in genotypic or allelic distribution between CHB and control groups were observed. Within TDP2, rs3087943 variations were associated with treatment response, and rs1047782 modified the risk of advanced liver inflammation. Rs7154439 within NTCP was associated with HBeAg seroconversion after 48 weeks of nucleos(t)ide analogue treatment. HNF1α genotypes were associated with treatment response, liver damage and baseline HBeAg presence. HNF4α rs1800961 predicted PEG-IFNα treatment-induced HBsAg clearance in long-term follow up.

CONCLUSIONS

This study indicates host genetic background relevance in the course of CHB and confirms the role of recently described genes for HBV infection. The obtained results might serve as a starting point for validation studies on the clinical application of selected genetic variants to predict individual risks of CHB-induced liver failure and treatment response.

Treatment of Chronic Hepatitis B Virus Infection Using Small Molecule Modulators of Nucleocapsid Assembly: Recent Advances and Perspectives

On the basis of the recent advance of basic research on molecular biology of hepatitis B virus (HBV) infection, novel antiviral drugs targeting various steps of the HBV life cycle have been developed in recent years. HBV nucleocapsid assembly is now recognized as a hot target for anti-HBV drug development. Structural and functional analysis of HBV nucleocapsid allowed rational design and improvement of small molecules with the ability to interact with the components of HBV nucleocapsid and modulate the viral nucleocapsid assembly process. Prototypes of small molecule modulators targeting HBV nucleocapsid assembly are being preclinically tested or have moved forward in clinical trials, with promising results. This Review summarizes the recent advances in the approach to develop antiviral drugs based on the modulation of HBV nucleocapsid assembly. The antiviral mechanisms of small molecule modulators beyond the capsid formation and the potential implications will be discussed.

Insights From Deep Sequencing of the HBV Genome-Unique, Tiny, and Misunderstood

Hepatitis B virus (HBV) is a unique, tiny, partially double-stranded, reverse-transcribing DNA virus with proteins encoded by multiple overlapping reading frames. The substitution rate is surprisingly high for a DNA virus, but lower than that of other reverse transcribing organisms. More than 260 million people worldwide have chronic HBV infection, which causes 0.8 million deaths a year. Because of the high burden of disease, international health agencies have set the goal of eliminating HBV infection by 2030. Nonetheless, the intriguing HBV genome has not been well characterized. We summarize data on the HBV genome structure and replication cycle, explain and quantify diversity within and among infected individuals, and discuss advances that can be offered by application of next-generation sequencing technology. In-depth HBV genome analyses could increase our understanding of disease pathogenesis and allow us to better predict patient outcomes, optimize treatment, and develop new therapeutics.

Clinical evaluation of hepatitis B core-related antigen in chronic hepatitis B and hepatocellular carcinoma patients

BACKGROUND

Hepatitis B core-related antigen (HBcrAg) has been revealed as an important marker of Hepatitis B virus (HBV) infection recently. We aimed to evaluate the HBcrAg assay for indication of HBV loads in chronic hepatitis B (CHB) and hepatocellular carcinoma (HCC) patients and assess the association between HBcrAg/cccDNA and HCC recurrence.

METHODS

HBcrAg was measured by chemiluminescence enzyme immunoassay. Intrahepatic covalently closed circular DNA (cccDNA) was measured by real-time PCR with TaqMan fluorescent probes based on liver specimens from 89 HCC patients.

RESULTS

HBcrAg correlated positively with HBV DNA irrespective of HBeAg status. Both HBcrAg and HBV DNA were associated with cccDNA in patients with elevated serum HBV DNA (>4 log IU/mL). In patients with non-elevated HBV DNA (≤4 log IU/mL), no relationship between HBV DNA and cccDNA was observed, but we still documented a modest correlation between HBcrAg and cccDNA. Finally, the recurrence-free survival rates were significantly lower in HCC patients with high intrahepatic cccDNA and serum HBcrAg levels than those with low cccDNA/HBcrAg levels (p = 0.035, p = 0.003 respectively).

CONCLUSIONS

HBcrAg not only can serve as a biomarker to assess HBV loads in patients as well as provide a good method for monitoring cccDNA in HCC, but also can be used as a good prognostic predictor for HCC patients.

Establishment of Cre-mediated HBV recombinant cccDNA (rcccDNA) cell line for cccDNA biology and antiviral screening assays

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), existing in hepatocyte nuclei as a stable minichromosome, plays a central role in the life cycle of the virus and permits the persistence of infection. Despite being essential for HBV infection, little is known about the molecular mechanisms of cccDNA formation, regulation and degradation, and there is no therapeutic agents directly targeting cccDNA, fore mostly due to the lack of robust, reliable and quantifiable HBV cccDNA models. In this study, combined the Cre/loxP and sleeping beauty transposons system, we established HepG2-derived cell lines integrated with 2-60 copies of monomeric HBV genome flanked by loxP sites (HepG2-HBV/loxP). After Cre expression via adenoviral transduction, 3.3-kb recombinant cccDNA (rcccDNA) bearing a chimeric intron can be produced in the nuclei of these HepG2-HBV/loxP cells. The rcccDNA could be accurately quantified by quantitative PCR using specific primers and cccDNA pool generated in this model could be easily detected by Southern blotting using the digoxigenin probe system. We demonstrated that the rcccDNA was epigenetically organized as the natural minichromosome and served as the template supporting pgRNA transcription and viral replication. As the expression of HBV S antigen (HBsAg) is dependent on the newly generated cccDNA, HBsAg is the surrogate marker of cccDNA. Additionally, the efficacies of 3 classes of anti-HBV agents were evaluated in HepG2-HBV/loxP cells and antiviral activities with different mechanisms were confirmed. These data collectively suggested that HepG2-HBV/loxP cell system will be powerful platform for studying cccDNA related biological mechanisms and developing novel cccDNA targeting drugs.

Advanced Strategies for Eliminating the cccDNA of HBV

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

Recent advances in the study of hepatitis B virus covalently closed circular DNA

Chronic hepatitis B infection is caused by hepatitis B virus (HBV) and a total cure is yet to be achieved. The viral covalently closed circular DNA (cccDNA) is the key to establish a persistent infection within hepatocytes. Current antiviral strategies have no effect on the pre-existing cccDNA reservoir. Therefore, the study of the molecular mechanism of cccDNA formation is becoming a major focus of HBV research. This review summarizes the current advances in cccDNA molecular biology and the latest studies on the elimination or inactivation of cccDNA, including three major areas: (1) epigenetic regulation of cccDNA by HBV X protein, (2) immune-mediated degradation, and (3) genome-editing nucleases. All these aspects provide clues on how to finally attain a cure for chronic hepatitis B infection.

Detection of HBV Covalently Closed Circular DNA

Chronic hepatitis B virus (HBV) infection affects approximately 240 million people worldwide and remains a serious public health concern because its complete cure is impossible with current treatments. Covalently closed circular DNA (cccDNA) in the nucleus of infected cells cannot be eliminated by present therapeutics and may result in persistence and relapse. Drug development targeting cccDNA formation and maintenance is hindered by the lack of efficient cccDNA models and reliable cccDNA detection methods. Southern blotting is regarded as the gold standard for quantitative cccDNA detection, but it is complicated and not suitable for high-throughput drug screening, so more sensitive and simple methods, including polymerase chain reaction (PCR)-based methods, Invader assays, in situ hybridization and surrogates, have been developed for cccDNA detection. However, most methods are not reliable enough, and there are no unified standards for these approaches. This review will summarize available methods for cccDNA detection. It is hoped that more robust methods for cccDNA monitoring will be developed and that standard operation procedures for routine cccDNA detection in scientific research and clinical monitoring will be established.