Inhibitory effect of adefovir on viral DNA synthesis and covalently closed circular DNA formation in duck hepatitis B virus-infected hepatocytes in vivo and in vitro

Usefulness of serum HBV RNA levels for predicting antiviral response to entecavir treatment in patients with chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) RNA is an important serum biomarker of hepatic covalently closed circular DNA (cccDNA) transcriptional activity; however, its clinical characteristics remain unclear. This study evaluated the clinical utility of HBV RNA levels in patients with chronic hepatitis B (CHB).

METHODS

We studied 87 CHB patients with serum HBV DNA levels ≥ 5.0 log IU/mL who initiated entecavir (ETV) treatment between 2000 and 2018. Serum HBV RNA levels were measured at three-time points: before ETV treatment, at 12 weeks, and at 48 weeks after starting ETV treatment. Clinical markers associated with the antiviral effects of ETV treatment were analyzed.

RESULTS

Serum HBV RNA levels decreased in both HBeAg-positive and -negative patients during the observation period. In HBeAg-positive patients, multivariable analysis showed that lower HBV RNA levels at 48 weeks of ETV treatment were independently associated with HBeAg seroconversion. Additionally, lower baseline HBV RNA levels significantly predicted virologic response in those patients. In contrast, among HBeAg-negative patients, lower HBV core-related antigen (HBcrAg) levels and the FIB-4 index were independently associated with virologic response. In HBeAg-positive patients, those with higher baseline HBV RNA levels showed a more significant reduction in hepatitis B surface antigen levels.

CONCLUSION

Serum HBV RNA levels predicted HBeAg seroconversion and early HBV DNA reduction in HBeAg-positive patients, while HBcrAg was significantly associated with virologic response in HBeAg-negative patients. These findings highlight the different predictive roles of HBV RNA and HBcrAg based on HBeAg status, which may provide individualized treatment strategies.

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.

Conserved use of the sodium/bile acid cotransporter (NTCP) as an entry receptor by hepatitis B virus and domestic cat hepadnavirus

The Orthohepadnavirus genus includes hepatitis B virus (HBV) that can cause chronic hepatitis and hepatocarcinoma in humans. Recently, a novel hepadnavirus in cats, domestic cat hepadnavirus (DCH), was identified that is genetically close to HBV. DCH infection is associated with chronic hepatitis in cats, suggesting a similarity with HBV pathogenesis and the potential to use DCH as a novel animal model for HBV research. HBV is shown to use the sodium/bile acid cotransporter (NTCP) as a major cell entry receptor, but the equivalent receptor for DCH remains unknown. Here we sought to identify the entry receptor for DCH. HBV- and DCH-derived preS1 peptides efficiently bound to both human and cat NTCPs, and residue 158 of NTCP proteins determined the species-specific binding of the DCH preS1 peptide. Myrcludex B, an HBV entry inhibitor, blocked the binding of the DCH preS1 peptide. Thus, DCH and HBV may share cell entry molecules, suggesting a possibility of inter-species transmission. Furthermore, our study suggests that DCH can be useful as a novel model for HBV research.

Recent Updates on Viral Oncogenesis: Available Preventive and Therapeutic Entities

Human viral oncogenesis is a complex phenomenon and a major contributor to the global cancer burden. Several recent findings revealed cellular and molecular pathways that promote the development and initiation of malignancy when viruses cause an infection. Even, antiviral treatment has become an approach to eliminate the viral infections and prevent the activation of oncogenesis. Therefore, for a better understanding, the molecular pathogenesis of various oncogenic viruses like, hepatitis virus, human immunodeficiency viral (HIV), human papillomavirus (HPV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV), could be explored, especially, to expand many potent antivirals that may escalate the apoptosis of infected malignant cells while sparing normal and healthy ones. Moreover, contemporary therapies, such as engineered antibodies antiviral agents targeting signaling pathways and cell biomarkers, could inhibit viral oncogenesis. This review elaborates the recent advancements in both natural and synthetic antivirals to control viral oncogenesis. The study also highlights the challenges and future perspectives of using antivirals in viral oncogenesis.

Early intrahepatic recurrence of HBV infection in liver transplant recipients despite antiviral prophylaxis

Background & Aims

Prophylaxis with nucleos(t)ide analogues (NUCs) and hepatitis B immunoglobulin (HBIG) has decreased the rate of HBV recurrence after orthotopic liver transplantation (OLT), but the duration of this prophylaxis remains debated. Our aim was to investigate the recurrence of both intrahepatic and serum HBV markers after OLT in patients receiving long-term NUC and HBIG prophylaxis.

Methods

A total of 31 HBV-positive patients benefiting from OLT were prospectively enrolled in five French centres between 2012 and 2015. Tissue samples from the native liver, liver reperfusion biopsy, and 12-month post-OLT (M12) biopsy were collected. Intrahepatic HBV markers were quantified using Droplet Digital PCR. Serum hepatitis B core-related antigen (HBcrAg) and HBsAg were quantified using the Lumipulse platform.

Results

Among the 31 patients, 26 were HBeAg negative and 28 had undetectable serum HBV DNA at OLT. All patients received HBIG and NUC after OLT, and serum HBV DNA was undetectable at M12. Of the 27 available native livers, 26 had detectable total HBV DNA (median, 0.045 copies/cell), 21 were positive for cccDNA (0.001 copies/cell), and 19 were positive for 3.5-kb HBV RNA (0.0004 copies/cell). Among the 14 sequential reperfusion and M12 biopsies, seven were positive for HBV markers on the reperfusion sampling, and six of them were also positive at M12. Of the 27 patients with available serum samples at M12, eight were positive for HBcrAg and five were positive for HBsAg by ultrasensitive quantification, although they were negative by conventional techniques. Overall, among the 17 patients having a matched biopsy and serum sample at M12, only one had undetectable HBV markers in both the liver and serum.

Conclusions

Our results demonstrate a very early detection of viral genome in the graft and intrahepatic viral recurrence despite NUC and HBIG prophylaxis.

Clinical Trials Registration

This study is registered at ClinicalTrials.gov (NCT02602847).

Impact and Implications

In this work, we show that, despite the recommended prophylaxis based on NUC and HBIG, HBV can infect the new liver very rapidly after transplantation. Twelve months after transplantation, the majority of patients had at least one HBV marker detected in either serum or the liver. Therefore, our results demonstrate early intrahepatic viral recurrence despite NUC and HBIG therapy and underline the importance of an optimal patient compliance to the antiviral prophylaxis to prevent viral rebound.

Overview of the development of HBV small molecule inhibitors

Like tuberculosis and Acquired Immune Deficiency Syndrome (AIDS), hepatitis B is a globally recognized major public health threat. Although there are many small-molecule drugs for the treatment of hepatitis B, the approved drugs cannot eradicate the pathogenic culprit covalently closed circular DNA in patients, so the patients need long-term medication to control HBV amplification. Driven by a high unmet medical need, many pharmaceutical companies and research institutions have been engaged in the development of anti-HBV drugs to achieve a functional cure for chronic hepatitis B as soon as possible. This review summarizes the pathogenesis of hepatitis B virus and the research progress in the development of anti-HBV small molecule drugs, and introduces the cccDNA formation and transcription inhibitors and core inhibitors in detail, especially emphasizes the role of chinese herbal medicine in the treatment of chronic hepatitis B. Furthermore, this review proposes three potential strategies for cccDNA eradication in the future. We believe this review will provide meaningful guidance to achieve a functional cure for viral hepatitis B in the future.

Immunomodulatory nanosystems: An emerging strategy to combat viral infections

The viral infection spreads with the assistance of a host. Traditional antiviral therapies cannot provide long-term immunity against emerging and drug-resistant viral infections. Immunotherapy has evolved as an efficient approach for disease prevention and treatment, which include cancer, infections, inflammatory, and immune disorders. Immunomodulatory nanosystems can dramatically enhance therapeutic outcomes by combating many therapeutic challenges, such as poor immune stimulation and off-target adverse effects. Recently, immunomodulatory nanosystems have emerged as a potent antiviral strategy to intercept viral infections effectively. This review introduces major viral infections with their primary symptoms, route of transmission & targeted organ, and different stages of the viral life cycle with respective traditional blockers. The IMNs have an exceptional capacity for precisely modulating the immune system for therapeutic applications. The nano sized immunomodulatory systems permit the immune cells to interact with infectious agents enhancing lymphatic drainage and endocytosis by the over-reactive immune cells in the infected areas. Immune cells that can be modulated upon viral infection via various immunomodulatory nanosystems have been discussed. Advancement in theranostics can yield an accurate diagnosis, adequate treatment, and real-time screening of viral infections. Nanosystem-based drug delivery can continue to thrive in diagnosing, treating, and preventing viral infections. The curative medicine for remerging and drug-resistant viruses remains challenging, though certain systems have expanded our perception and initiated a new research domain in antiviral treatments.

Persistent Hepatitis B Viraemia with Polymerase Mutations among HIV/HBV Co-Infected Patients on HBV-Active ART in KwaZulu-Natal, South Africa

To understand the problem of persistent Hepatitis B virus (HBV) viraemia in HIV/HBV co-infected patients on HBV-active antiretroviral therapy (ART), we assessed the rate of HBV virological response in patients on HBV-active ART in KwaZulu-Natal, South Africa, and analysed factors associated with persistent HBV viraemia. One hundred and fifty eligible participants with a chronic HBV diagnosis, with or without HIV coinfection, were enrolled and followed up after 6 months. The HBV pol gene was sequenced by next-generation sequencing and mutations were determined using the Stanford HBVseq database. Logistic regression analysis was used to assess factors associated with HBV viraemia at 6-month follow-up. The mean duration of HBV-active ART was 24 months. Thirty-seven of one hundred and six (35%) participants receiving HBV-active ART for longer than 6 months had virological failure. Advanced immunosuppression with CD4+ cell counts <200 cells/μL was independently associated with persistent HBV viraemia, aOR 5.276 (95% CI 1.575−17.670) p = 0.007. A high proportion of patients on HBV-active ART are unsuppressed, which will ultimately have an impact on global elimination goals. Better monitoring should be implemented, especially in HIV-coinfected patients with low CD4+ cell counts and followed by early HBV drug-resistance testing.

2020 position statement and recommendations of the European Liver and Intestine Transplantation Association (ELITA): management of hepatitis B virus-related infection before and after liver transplantation

BACKGROUND

Prophylaxis of HBV recurrence is critical after liver transplantation in HBV patients. Despite new prophylactic schemes, most European LT centres persist on a conservative approach combining hepatitis B immunoglobulin (HBIG) and nucleos(t)ides analogues (NA).

AIM

This setting prompted the European Liver Intestine Transplantation Association (ELITA) to look for a consensus on the prevention of HBV recurrence.

METHODS

Based on a 4-round Delphi process, ELITA investigated 16 research questions and established 50 recommendations.

RESULTS

Prophylaxis should be driven according to 3 simplified risk groups: Low and high virological risk patients, with undetectable and detectable HBV DNA pre-LT, respectively, and special populations (HDV, HCC, poorly adherent patients). In low-risk patients, short-term (4 weeks) combination of third-generation NA+ HBIG, or third generation NA monotherapy can be considered as prophylactic options. In high-risk patients, HBIG can be discontinued once HBV DNA undetectable. Combined therapy for 1 year is advised. HBV-HCC patients should be treated according to their virological risk. In HDV/HBV patients, indefinite dual prophylaxis remains the gold standard. Full withdrawal of HBV prophylaxis following or not HBV vaccination should only be attempted in the setting of clinical trials. Organs from HBsAg+ve donors may be considered after assessment of risks, benefits, and patient consent. They should not be used if HDV is present. In poorly adherent patients, dual long-term prophylaxis is recommended. Budget impact analysis should be taken into account to drive prophylactic regimen.

CONCLUSIONS

These ELITA recommendations should stimulate a more rational and homogeneous approach to HBV prophylaxis across LT programs.

A systematic study of Tupaia as a model for human acute hepatitis B infection

The molecular features of hepatitis B virus (HBV) infection, eradication, and pathogenesis are poorly understood, partly due to the lack of an adequate animal model that faithfully reproduces the course of infection. Although Tupaia belangeri were previously recognized as HBV-susceptible animals, the course of infection in adult tupaias remains obscure. Herein, we performed a longitudinal study and demonstrated that adult tupaias were efficiently infected (90% infection rate) with 10⁸ copies of the HBV genome. HBV replicated vigorously, produced high levels of covalently closed circular DNA (cccDNA) in hepatocytes, and released hepatitis B surface antigen (HBsAg), hepatitis Be antigen (HBeAg), and HBV DNA into the serum at day 9 post-inoculation (p.i.), which then decreased on day 15 p.i. The kinetics were consistent with the expression of liver HBsAg and HBeAg, as determined with immunohistochemistry. The viral products in serum at day 9 and 15 p.i. represented de novo synthesized viral products, as treatment with a viral entry inhibitor completely abolished these products from the serum. Viral clearance and serological conversion occurred at day 21 p.i. and were accompanied by elevated alanine transaminase (ALT) levels and liver pathology, such as inflammatory infiltration and hepatocyte ballooning degeneration. Although ALT levels eventually returned to normal levels by day 42 p.i., the liver pathology persisted until at least day 120 p.i. The HBV infection process in tupaia, therefore, exhibits features similar to that of human acute HBV infection, including viral replication, viral eradication, ALT elevation, and liver pathology. Thus, adopting the tupaia model to study host-HBV interactions presents an important advance which could facilitate further investigation and understanding of human HBV infection, especially for features like cccDNA that current small-animal models cannot effectively model.

Involvement of Host ATR-CHK1 Pathway in Hepatitis B Virus Covalently Closed Circular DNA Formation

Hepatitis B virus (HBV) chronically infects hundreds of millions of people and remains a major cause of viral hepatitis, cirrhosis, and liver cancer. HBV persistence is sustained by a viral nuclear episome that directs all viral gene expression needed to support viral replication. The episome is converted from an incomplete DNA precursor in viral particles in an ill-understood process. We report here that the incomplete DNA precursor is recognized by the host cell in a way similar to the sensing of damaged cellular DNA for subsequent repair to form the nuclear episome. Intense efforts are ongoing to develop novel antiviral strategies to eliminate CCC DNA so as to cure chronic HBV infection. Our results here provide novel insights into, and suggest novel ways of perturbing, the process of episome formation. Furthermore, our results inform mechanisms of cellular DNA damage recognition and repair, processes essential for normal cell growth.

The covalently closed circular (CCC) DNA of hepatitis B virus (HBV) functions as the only viral transcriptional template capable of producing all viral RNA species and is essential to initiate and sustain viral replication. CCC DNA is converted from a relaxed circular (RC) DNA, in which neither of the two DNA strands is covalently closed. As RC DNA mimics damaged cellular DNA, the host cell DNA damage repair (DDR) system is thought to be responsible for HBV CCC DNA formation. The potential role of two major cellular DDR pathways, the ataxia telangiectasia mutated (ATM) pathway and the ATM and Rad3-related (ATR) pathway, in HBV CCC DNA formation was thus investigated. Inhibition, or expression knockdown, of ATR and its downstream signaling factor CHK1, but not of ATM, decreased CCC DNA formation during de novo HBV infection, as well as intracellular CCC DNA amplification, when RC DNA from extracellular virions and intracellular nucleocapsids, respectively, is converted to CCC DNA. Furthermore, a novel RC DNA processing product with 5′ truncated minus strands was detected when the ATR-CHK1 pathway was inhibited, further indicating that this pathway controls RC DNA processing during its conversion to CCC DNA. These results provide new insights into how host cells recognize and process HBV RC DNA in order to produce CCC DNA and have implications for potential means to block CCC DNA production.

Effects of traditional Chinese medicine formula Le-Cao-Shi on hepatitis B: In vivo and in vitro studies

ETHNOPHARMACOLOGICAL RELEVANCE

Formula Le-Cao-Shi (LCS) is a traditional Chinese medicine (TCM), which has long been used as a folk remedy against hepatitis B in China. The present study was conducted to evaluate the anti-hepatitis B effects of aqueous extract of LCS in vivo and in vitro.

MATERIALS AND METHOD

we investigated the anti-HBV effects of LCS in vivo and in vitro with duck hepatitis B model and HepG2.2.15 cell line model, respectively. The serologic and cellular biomarkers and the histopathological changes were examined.

RESULTS

By a duck hepatitis B model, the extract of LCS was found to restrain the expressions of duck hepatitis B surface antigen (DHBsAg), hepatitis B e antigen (DHBeAg), and HBV-DNA (DHBV-DNA). Moreover, LCS could decrease the levels of aspartate and alanine aminotransferases (AST and ALT) and ameliorate duck liver histological lesions. Correspondingly, in a HepG2.2.15 cellular model, LCS could also significantly inhibit the secretions of HBsAg and HBeAg.

CONCLUSION

LCS exerted potent anti-hepatitis effects against the infection of HBV. The above results demonstrated the first-hand experimental evidences for the anti-hepatitis B efficiency of LCS. Our study provides a basis for further exploration and development of this promising compound prescription to treat hepatitis B disease.

Xiao Chai Hu Tang, a herbal medicine, for chronic hepatitis B

BACKGROUND

Chronic hepatitis B is associated with high morbidity and mortality. Chronic hepatitis B requires long-term management aiming at reduction of the risks of hepatocellular inflammatory necrosis, liver fibrosis, decompensated liver cirrhosis, liver failure, and liver cancer, and improving health-related quality of life. The Chinese herbal medicine formula Xiao Chai Hu Tang has been used to decrease discomfort and replication of the virus in people with chronic hepatitis B. However, the benefits and harms of Xiao Chai Hu Tang formula have never been established with rigorous review methodology.

OBJECTIVES

To assess the benefits and harms of Xiao Chai Hu Tang formula versus placebo or no intervention in people with chronic hepatitis B.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE Ovid, Embase Ovid, and seven other databases to 1 March 2019. We also searched the World Health Organization International Clinical Trials Registry Platform (www.who.int/ictrp), ClinicalTrials.gov (www.clinicaltrials.gov/), and the Chinese Clinical Trial Registry for ongoing or unpublished trials to 1 March 2019.

SELECTION CRITERIA

We included randomised clinical trials, irrespective of publication status, language, and blinding, comparing Xiao Chai Hu Tang formula versus no intervention or placebo in people with chronic hepatitis B. We included participants of any sex and age, diagnosed with chronic hepatitis B according to guidelines or as defined by the trialists. We allowed co-interventions when the co-interventions were administered equally to all the intervention groups.

DATA COLLECTION AND ANALYSIS

Review authors independently retrieved data from reports and after correspondence with investigators. Our primary outcomes were all-cause mortality, serious adverse events, and health-related quality of life. Our secondary outcomes were hepatitis B-related mortality, hepatitis B-related morbidity, and adverse events considered 'not to be serious'. We presented the meta-analysed results as risk ratios (RR) with 95% confidence intervals (CI). We assessed the risks of bias using risk of bias domains with predefined definitions. We used GRADE methodology to evaluate our certainty in the evidence.

MAIN RESULTS

We included 10 randomised clinical trials with 934 participants, but only five trials with 490 participants provided data for analysis. All the trials compared Xiao Chai Hu Tang formula with no intervention. All trials appeared to have been conducted and published only in China. The included trials assessed heterogeneous forms of Xiao Chai Hu Tang formula, administered for three to eight months. One trial included participants with hepatitis B and comorbid tuberculosis, and one trial included participants with hepatitis B and liver cirrhosis. The remaining trials included participants with hepatitis B only. All the trials were at high risk of bias, and the certainty of evidence for all outcomes that provided data for analyses was very low. We downgraded the evidence by one or two levels because of outcome risk of bias, inconsistency or heterogeneity of results (opposite direction of effect), indirectness of evidence (use of surrogate outcomes instead of clinically relevant outcomes), imprecision of results (the CIs were wide), and publication bias (small sample size of the trials). Additionally, 47 trials lacked the necessary methodological information needed to ensure the inclusion of these trials in our review. None of the included trials aimed to assess clinically relevant outcomes such as all-cause mortality, serious adverse events, health-related quality of life, hepatitis B-related mortality, or hepatitis B-related morbidity. The effects of Xiao Chai Hu Tang formula on the proportion of participants with adverse events considered 'not to be serious' is uncertain (RR 0.43, 95% CI 0.02 to 11.98; I2 = 69%; very low-certainty evidence). Only three trials with 222 participants reported the proportion of people with detectable hepatitis B virus DNA (HBV-DNA), but the evidence that Xiao Chai Hu Tang formula reduces the presence of HBV-DNA in the blood (a surrogate outcome) is uncertain (RR 0.62, 95% CI 0.45 to 0.85; I2 = 0%; very low-certainty evidence). Only two trials with 160 participants reported the proportion of people with detectable hepatitis B virus e-antigen (HBeAg; a surrogate outcome) (RR 0.72, 95% CI 0.50 to 1.02; I2 = 38%; very low-certainty evidence) and the evidence is uncertain. The evidence is also uncertain for separately reported adverse events considered 'not to be serious'.

FUNDING

two of the 10 included trials received academic funding from government or hospital. None of the remaining eight trials reported information on funding.

AUTHORS' CONCLUSIONS

The clinical effects of Xiao Chai Hu Tang formula for chronic hepatitis B remain unclear. The included trials were small and of low methodological quality. Despite the wide use of Xiao Chai Hu Tang formula, we lack data on all-cause mortality, serious adverse events, health-related quality of life, hepatitis B-related mortality, and hepatitis B-related morbidity. The evidence in this systematic review comes from data obtained from a maximum three trials. We graded the certainty of evidence as very low for adverse events considered not to be serious and the surrogate outcomes HBeAg and HBV-DNA. We found a large number of trials which lacked clear description of their design and conduct, and hence, these trials are not included in the present review. As all identified trials were conducted in China, there might be a concern about the applicability of this review outside China. Large-sized, high-quality randomised sham-controlled trials with homogeneous groups of participants and transparent funding are lacking.

Revisiting Hepatitis B Virus: Challenges of Curative Therapies

With a yearly death toll of 880,000, hepatitis B virus (HBV) remains a major health problem worldwide, despite an effective prophylactic vaccine and well-tolerated, effective antivirals. HBV causes chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The viral genome persists in infected hepatocytes even after long-term antiviral therapy, and its integration, though no longer able to support viral replication, destabilizes the host genome. HBV is a DNA virus that utilizes a virus-encoded reverse transcriptase to convert an RNA intermediate, termed pregenomic RNA, into the relaxed circular DNA genome, which is subsequently converted into a covalently closed circular DNA (cccDNA) in the host cell nucleus. cccDNA is maintained in the nucleus of the infected hepatocyte as a stable minichromosome and functions as the viral transcriptional template for the production of all viral gene products, and thus, it is the molecular basis of HBV persistence. The nuclear cccDNA pool can be replenished through recycling of newly synthesized, DNA-containing HBV capsids. Licensed antivirals target the HBV reverse transcriptase activity but fail to eliminate cccDNA, which would be required to cure HBV infection. Elimination of HBV cccDNA is so far only achieved by antiviral immune responses. Thus, this review will focus on possible curative strategies aimed at eliminating or crippling the viral cccDNA. Newer insights into the HBV life cycle and host immune response provide novel, potentially curative therapeutic opportunities and targets.

A Global View to HBV Chronic Infection: Evolving Strategies for Diagnosis, Treatment and Prevention in Immunocompetent Individuals

Hepatitis B Virus (HBV) is a significant public health challenge. Around 250 million people live with chronic HBV infection. With a global approach to this issue, we focus on new perspective in diagnosis, management and prevention of HBV chronic infection. Precise diagnosis of HBV status is crucial to guide patient management. Although available drugs reduce the risk of liver disease progression, they are not able to definitely eradicate HBV, and new therapeutic options are urgently needed. Thus, prevention of HBV infection is still the most effective strategy to achieve the control of the disease. Key aspects of prevention programs include surveillance of viral hepatitis, screening programs and immunization strategies. In spite of the high success rate of licensed HBV vaccines, a need for improved vaccine persists, especially in order to provide coverage of current non-responders.

Adefovir dipivoxil sensitizes colon cancer cells to vemurafenib by disrupting the KCTD12-CDK1 interaction

Vemurafenib is a B-Raf V600E inhibitor that exerts significant inhibitory effects in melanoma but not in colon cancer, and the mechanism of vemurafenib resistance remains unclear. In this study, bioinformatics analysis of gene profiles in cancer cells treated with vemurafenib or its analog revealed that cell cycle progression is significantly affected by vemurafenib. We found that CDK1 is stably activated in the vemurafenib-resistant (VR) colon cancer sublines that we established, indicating that CDK1 activation is responsible for vemurafenib resistance. As the KCTD12-CDK1 interaction is necessary for CDK1 activation, we screened an FDA-approved drug library consisting of 616 compounds and identified that adefovir dipivoxil (AD), a nucleoside analog for treatment of HBV infections, disrupts the CDK1-KCTD12 interaction and induces G2 phase arrest in the cell cycle. Functional assays demonstrated that AD significantly inhibited colon cancer cell proliferation and tumorigenesis both in vitro and in vivo with no observed side effects. Furthermore, AD sensitized vemurafenib-resistant colon cancer cells and tumor xenografts to vemurafenib. This study reveals that CDK1 activation induces vemurafenib resistance and that AD is a promising therapeutic strategy for colon cancer both as a single agent and in combination with vemurafenib.

A Role for the Host DNA Damage Response in Hepatitis B Virus cccDNA Formation-and Beyond?

Chronic hepatitis B virus (HBV) infection puts more than 250 million people at a greatly increased risk to develop end-stage liver disease. Like all hepadnaviruses, HBV replicates via protein-primed reverse transcription of a pregenomic (pg) RNA, yielding an unusually structured, viral polymerase-linked relaxed-circular (RC) DNA as genome in infectious particles. Upon infection, RC-DNA is converted into nuclear covalently closed circular (ccc) DNA. Associating with cellular proteins into an episomal minichromosome, cccDNA acts as template for new viral RNAs, ensuring formation of progeny virions. Hence, cccDNA represents the viral persistence reservoir that is not directly targeted by current anti-HBV therapeutics. Eliminating cccDNA will thus be at the heart of a cure for chronic hepatitis B. The low production of HBV cccDNA in most experimental models and the associated problems in reliable cccDNA quantitation have long hampered a deeper understanding of cccDNA molecular biology. Recent advancements including cccDNA-dependent cell culture systems have begun to identify select host DNA repair enzymes that HBV usurps for RC-DNA to cccDNA conversion. While this list is bound to grow, it may represent just one facet of a broader interaction with the cellular DNA damage response (DDR), a network of pathways that sense and repair aberrant DNA structures and in the process profoundly affect the cell cycle, up to inducing cell death if repair fails. Given the divergent interactions between other viruses and the DDR it will be intriguing to see how HBV copes with this multipronged host system.

Hepatitis B reactivation during or after direct acting antiviral therapy - implication for susceptible individuals

INTRODUCTION

The FDA issued a warning following 24 cases of HBV reactivation during DAA therapy for HCV, including individuals with inactive, occult and past HBV infection. Clinical presentations ranged from asymptomatic fluctuations in HBV DNA to fulminant hepatic failure, liver transplantation and death. The mechanism is unknown. Areas covered: HCV/HBV coinfection is common, particularly in regions endemic for HBV. HCV and HBV utilize host factors to support replication; both viruses evade/impair host immunity. Clinical presentations of HBV reactivation during DAAs are summarized. Other causes of HBV reactivation are revisited and recent data regarding HBV reactivation are presented. Expert opinion: HBV reactivation during DAAs for HCV occurs, with life-threatening consequences in some individuals. The risk of HBV reactivation is observed in all HBV stages. The rapid removal of HCV likely alters and liberates host-viral ± viral-viral interactions that lead to increased HBV replication. As immune reconstitution occurs with HCV removal, host recognition of HBV DNA likely ensues followed by vigorous host immune responses leading to liver injury (HBV flare). These cases highlight the importance of HBV testing prior to initiating DAA therapy, the need for close monitoring of HBV during therapy and timely administration of anti-HBV therapy to prevent serious sequelae.

Intrahepatic innate immune response pathways are downregulated in untreated chronic hepatitis B

BACKGROUND & AIMS

Hepatitis B virus (HBV) persistence and the pathobiology of chronic HBV (CHB) infections result from the interplay between viral replication and host immune responses. We aimed to comprehensively analyse the expression of intrahepatic host genes as well as serum and liver HBV markers in a large cohort of untreated CHB patients.

METHODS

One-hundred and five CHB patients untreated at the time of liver biopsy (34 HBeAg[+] and 71 HBeAg[-]) were analysed for the intrahepatic expression profile of 67 genes belonging to multiple innate immunity pathways. Results were correlated to serological (quantification of HBsAg [qHBsAg] and HBV DNA) and intrahepatic viral markers (total HBV DNA, pre-genomic RNA and covalently closed circular HBV DNA).

RESULTS

Intrahepatic gene expression profiling revealed a strong downregulation of antiviral effectors, interferon stimulated genes, Toll-like and pathogen recognition receptor pathways in CHB patients as compared to non-infected controls, which was not directly correlated to HBV replication. A subset of genes [CXCL10, GBP1, IFITM1, IFNB1, IL10, IL6, ISG15, TLR3, SOCS1, SOCS3] was more repressed in HBeAg(-) respect to HBeAg(+) patients (median of serum HBV DNA 7.9×10³vs. 7.9×10⁷IU/ml, respectively). Notably, HBeAg(-) patients with lower qHBsAg (<5×10³IU/ml) showed a relief of repression of genes belonging to multiple pathways.

CONCLUSIONS

Our results show a strong impairment of innate immune responses in the liver of CHB patients. The association of low levels of qHBsAg with gene repression, if confirmed, might prove useful for the identification of patients who would most benefit from immune-modulators and/or HBsAg targeting agents as strategies to restore immune responsiveness.

LAY SUMMARY

Chronic hepatitis B virus (HBV) infections represent a major public health problem worldwide. Over 200 million people are chronically infected and at risk of developing chronic hepatitis, liver cirrhosis and cancer. Our work aimed to understand the molecular consequences of chronic hepatitis B in the infected liver. It was conducted in a large cohort of untreated chronically infected HBV patients and analysed the expression of immunity and liver disease-related genes in the liver, with respect to markers of viral replication and persistence. Our results indicate that chronic HBV infection has a suppressive effect on immune responses, which was more pronounced with high levels of hepatitis B virus surface antigen (HBsAg). These data provide novel insight into the mechanisms of HBV persistence in the liver and suggest that approaches aimed at reducing HBsAg levels, may restore immune responsiveness against the virus.

DNA Polymerase κ Is a Key Cellular Factor for the Formation of Covalently Closed Circular DNA of Hepatitis B Virus

Hepatitis B virus (HBV) infection of hepatocytes begins by binding to its cellular receptor sodium taurocholate cotransporting polypeptide (NTCP), followed by the internalization of viral nucleocapsid into the cytoplasm. The viral relaxed circular (rc) DNA genome in nucleocapsid is transported into the nucleus and converted into covalently closed circular (ccc) DNA to serve as a viral persistence reservoir that is refractory to current antiviral therapies. Host DNA repair enzymes have been speculated to catalyze the conversion of rcDNA to cccDNA, however, the DNA polymerase(s) that fills the gap in the plus strand of rcDNA remains to be determined. Here we conducted targeted genetic screening in combination with chemical inhibition to identify the cellular DNA polymerase(s) responsible for cccDNA formation, and exploited recombinant HBV with capsid coding deficiency which infects HepG2-NTCP cells with similar efficiency of wild-type HBV to assure cccDNA synthesis is exclusively from de novo HBV infection. We found that DNA polymerase κ (POLK), a Y-family DNA polymerase with maximum activity in non-dividing cells, substantially contributes to cccDNA formation during de novo HBV infection. Depleting gene expression of POLK in HepG2-NTCP cells by either siRNA knockdown or CRISPR/Cas9 knockout inhibited the conversion of rcDNA into cccDNA, while the diminished cccDNA formation in, and hence the viral infection of, the knockout cells could be effectively rescued by ectopic expression of POLK. These studies revealed that POLK is a crucial host factor required for cccDNA formation during a de novo HBV infection and suggest that POLK may be a potential target for developing antivirals against HBV.

HBV chronically infects 240 million people worldwide. Persistent HBV infection relies on stable maintenance of the nuclear form of viral genome, the covalently closed circular (ccc) DNA. However, the molecular mechanism underlying the conversion of HBV genomic relaxed circular (rc) DNA into cccDNA remains elusive. Our studies reported herein provide unambiguous evidence suggesting that host DNA polymerase κ (POLK) is required for repairing the gap of rcDNA and formation of cccDNA in a de novo HBV infection. POLK is thus a potential therapeutic target for treatment of chronic hepatitis B.

Review article: novel therapies for hepatitis B virus cure - advances and perspectives

BACKGROUND

Current anti-viral therapies, interferon and nucleos(t)ide analogues, have been proven to reduce the progression of chronic hepatitis B (CHB). However, covalently closed circular DNA (cccDNA) of hepatitis B virus (HBV) persists, resulting in viral relapse after the discontinuation of treatment.

AIM

To discuss and review novel therapies for chronic hepatitis B infection.

METHODS

Recent published studies which searched from PubMed were comprehensive reviewed. The key words include chronic hepatitis B, hepatitis B virus cure, covalently closed circular DNA, direct acting anti-virals and host targeting agents.

RESULTS

Several novel agents through viral and host targets approaches are under investigations towards functional cure of HBV. On the one hand, direct acting anti-virals targeting virus itself, such as HBV new polymerase inhibitor, entry inhibitor, engineered site-specific nucleases and RNA interference, could inhibit amplification of cccDNA as well as intrahepatic HBV infection and eliminate or silence cccDNA transcription. Inhibitors of HBV nucleocapsid assembly suppress capsid formation and prevent synthesis of HBV DNA. On the other hand, host targeting agents (HTA) include lymphotoxin-β receptor agonist, toll-like receptor agonist, immune checkpoint inhibitors and adenovirus-based therapeutic vaccine. Through enhancing innate and adaptive immune responses, these agents could induce noncytolytic destruction of cccDNA or attack HBV-infected hepatocytes.

CONCLUSION

With these promising approaches, we hope to reach global hepatitis B virus control in the middle of this century.

Clinical relevance of the study of hepatitis B virus covalently closed circular DNA

Hepatitis B virus (HBV) remains a public health concern with 240 million people affected worldwide. HBV is an hepadnavirus that replicates its genome in hepatocytes. One of the key steps of the viral life cycle is the formation of cccDNA - covalently closed circular DNA - in the nucleus, the equivalent of a viral mini-chromosome that acts as a template for subsequent virus replication. Current antiviral medications are not effective in eradicating cccDNA, which can persist in the infected liver even in the absence of detectable HBV DNA or HBsAg in the blood. cccDNA cannot be measured in serum, and few surrogate markers have been proposed. Persistent cccDNA has been associated with various clinical events, including viral reactivation induced by immunosuppressive therapies, HBV recurrence after liver transplantation and hepatocellular carcinoma (HCC). cccDNA remains the main target to achieve a cure of HBV infection, thus extensive efforts are being made to develop new antiviral concepts to degrade or silence cccDNA.

Efficacy of tenofovir disoproxil fumarate therapy in Chinese chronic hepatitis B patients after multiple antiviral failures

AIM

In this prospective study, we aimed to evaluate the efficacy and safety of tenofovir disoproxil fumarate (TDF) in Chinese chronic hepatitis B (CHB) patients after multiple nucleoside/nucleotide analog (NA) treatment failures.

METHODS

A total of 115 Chinese CHB patients with suboptimal response to two or more NA treatments were included in this study. All patients were changed to TDF (300 mg/day, oral administration) antiviral treatment for at least 72 weeks. Hepatitis B virus (HBV) polymerase (P) gene mutation screening for each patient was performed. In addition, virological, biochemical responses and estimated glomerular filtration rate (eGFR) of each patient at weeks 12, 24, 48 and 72 of TDF treatment were evaluated.

RESULTS

Seventy-six out of 115 patients had drug-resistance mutations (R(+) ), including 27 with adefovir (ADV)-associated mutations (35.5%) and 49 with lamivudine (LMV)-associated mutations (64.5%). For all included patients, complete viral response (CVR) of HBV DNA (<100 IU/mL) was 57.4%, 69.6%, 74.8% and 86.1% at weeks 12, 24, 48 and 72 of TDF treatment, respectively. Alanine aminotransferase normalization and hepatitis B e-antigen seroclearance occurred in 77.3% and 23.2%, respectively, after 72-week TDF treatment. CVR at weeks 12, 24 and 48 was observed more commonly in patients with baseline HBV DNA of less than 10(6)  IU/mL. There was no significant reduction of eGFR induced by the TDF treatment.

CONCLUSION

Seventy-two-week treatment with TDF in Chinese CHB patients with previously multiple NA treatment failures exhibited effective and safe outcomes, which were independent of baseline mutations conferring ADV or LMV resistance.

Inhibitory effect of Phyllanthus urinaria L. extract on the replication of lamivudine-resistant hepatitis B virus in vitro

BACKGROUND

Long-term treatment of chronic hepatitis B (CHB) with nucleos(t)ide analogs results in the emergence of drug-resistant hepatitis B virus (HBV) harboring mutations in the polymerase (P) gene. The Phyllanthus extract has anti-HBV activity; however, its antiviral activity against lamivudine (LMV)-resistant mutants has not been examined.

METHODS

HBV harboring LMV-resistant mutations (rtM204I, rtM204V, and rtM204S) in the P gene at the YMDD ((203)tyrosine-methionine-aspartate-aspartate(206)) reverse transcriptase (RT) active site were generated and their sensitivity to Phyllanthus urinaria koreanis extract examined. Southern blotting and real-time PCR were used to determine the concentration of plant extract required to inhibit HBV DNA synthesis by 50 and 90% (EC50 and EC90, respectively). An enzyme-linked immunosorbent assay was used to measure the EC50 of HBV surface antigen (HBsAg) and HBV core antigen (HBcAg) secretion, and the 50% cytotoxic concentration of the extract was measured in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Real-time RT-PCR was used to measure mRNA expression levels.

RESULTS

The expression of intracellular HBV DNAs in HBV WT- or mutant-transfected HepG2 cells decreased upon treatment with Phyllanthus extract. The secretion of HBsAg and HBcAg also fell in a dose-dependent manner. Phyllanthus extract induced interferon-beta (IFN-β), cyclooxygenase-2 (COX-2), and interleukin-6 (IL-6) mRNA expression in HBV WT-transfected HepG2 cells, possibly via activation of extracellular signal-regulated kinases and c-jun N-terminal kinases and the induction of retinoic acid inducible gene-I, toll-like receptor 3, myeloid differentiation primary response gene 88, and/or tumor necrosis factor receptor-associated factor 6 gene expression. HBV transfection in the absence of extract or exposure of cells to extract alone did not trigger these signaling cascades.

CONCLUSIONS

Phyllanthus extract inhibited HBV DNA synthesis and HBsAg and HBcAg secretion by replicating cells harboring HBV wild-type and LMV-resistant mutants, likely by inducing the expression of IFN-β, COX-2, and IL-6. These data indicate that Phyllanthus extract may be useful as an alternative therapeutic agent for the treatment of drug-resistant CHB patients.

Effect of alcohol extract of Acanthus ilicifolius L. on anti-duck hepatitis B virus and protection of liver

ETHNOPHARMACOLOGICAL RELEVANCE

Acanthus ilicifolius L. is an important medicinal mangrove plant. It is popularly used for its anti-inflammatory, antioxidant activity and hepatoprotective effects. The present study was conducted to evaluate the effect of treatment with alcohol extract of Acanthus ilicifolius L. on duck hepatitis B.

MATERIALS AND METHODS

One-day-old Guangxi shelducks injected intraperitoneally with strong positive duck hepatitis B virus (DHBV) serum were used to establish a duck hepatitis B animal model in the study. The ducks were respectively administered in different groups with low-, middle- and high-dose alcohol extracts of Acanthus ilicifolius L., the positive control drug acyclovir (ACV) and double-distilled water. The levels of serum DHBV DNA were detected by fluorescence quantitative PCR (FQ-PCR). Duck hepatitis B surface antigen (DHBsAg) and duck hepatitis B e antigen (DHBeAg) OD values in the serum were measured by ELISA. The activity of Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) in the serum was measured, and the livers were taken for histopathological examination.

RESULTS

The levels of serum DHBV DNA and the values of DHBsAg and DHBeAg OD were not significant in any of the dose extract groups. However, the ALT activity was obviously lower in the middle- and high-dose extract groups. It was also found that a high dose of alcohol extract could reduce the activity of AST significantly and significantly improve hepatic pathological effects.

CONCLUSIONS

High-dose alcohol extract of Acanthus ilicifolius L. has an obvious protective effect on the liver function and liver tissue. However, the present study finds that Acanthus ilicifolius L. cannot inhibit the replication of duck hepatitis B virus.

Targeting the Achilles heel of the hepatitis B virus: a review of current treatments against covalently closed circular DNA

Chronic infection with hepatitis B virus (HBV) often leads to the development of liver cancer and cirrhosis, creating immense sociological, clinical and economic burdens worldwide. Although current anti-HBV medications manage to control the disease progression and help restore normal liver functions, they often fail to eliminate the virus completely. A major reason for this failure is the presence of a stable viral genome in the hepatocyte nucleus: the covalently closed circular DNA (cccDNA). Targeting HBV cccDNA is a promising approach that could lead to a complete cure. Here, we review various research approaches that are directed toward eliminating HBV cccDNA. This is a brief, yet comprehensive, summary of current state-of-the-art developments in this emerging area of interest.

Persistence of hepatitis B virus covalently closed circular DNA in hepatocytes: molecular mechanisms and clinical significance

Covalently closed circular DNA (cccDNA) is the transcriptional template of hepatitis B virus (HBV). Extensive research over the past decades has unveiled the important role of cccDNA in the natural history and antiviral treatment of chronic HBV infection. cccDNA can persist in patients recovering from acute HBV infection for decades. This explains why HBV reactivation occasionally occurs in patients with resolved hepatitis B receiving intensive immunosuppressive agents. In addition, although advances in antiviral treatment dramatically improve the adverse outcomes of chronic hepatitis B (CHB), accumulating evidence demonstrates that current antiviral treatments alone, be they nucleos(t)ide analogs (NAs) or interferon (IFN), fail to cure most CHB patients because of the persistent cccDNA. NA suppresses HBV replication by directly inhibiting viral polymerase, while IFN enhances host immunity against HBV infection. Viral rebound often occurs after discontinuation of antiviral treatment. The loss of cccDNA can be induced by non-cytolytic destruction of cccDNA or immune-mediated killing of infected hepatocytes. It is known that NA has no direct effect on viral transcription or cccDNA stability. Therefore, the long half-life of hepatocytes leads to a very slow decline in cccDNA in patients under antiviral therapy. Novel antiviral agents targeting cccDNA or cccDNA-containing hepatocytes are thus required for curing chronic HBV infection.

Potential of acyclic nucleoside phosphonates in the treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates [HPMPC: cidofovir, Vistide; PMEA: adefovir dipivoxil, Hepsera; and PMPA: tenofovir, Viread] have proven to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections, for example, cidofovir against herpesvirus [herpes simplex virus type 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, human herpesvirus type 6, 7 and 8), polyoma-, papilloma-, adeno- and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus and orf) infections; adefovir against herpesvirus, hepadnavirus [human hepatitis B virus] and retrovirus [HIV type-1 and 2, simian immunodeficiency virus and feline immunodeficiency virus] infections; and tenofovir against both hepadna- and retrovirus infections. Cidofovir has been officially approved for the treatment of cytomegalovirus retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) for the treatment of HIV infections (i.e., AIDS) and adefovir dipivoxil for the treatment of chronic hepatitis B.

Antiviral activity of methyl helicterate isolated from Helicteres angustifolia (Sterculiaceae) against hepatitis B virus

The anti-HBV effect of methyl helicterate (MH), a triterpenoid isolated from the Chinese herb Helicteres angustifolia, was explored both in vitro and in vivo. In the HBV-transfected cell line HepG2.2.15, the secretion of HBsAg/HBeAg, the levels of HBV DNA and cccDNA, and the amount of viral RNA were significantly decreased after treatment with MH for 144h. In addition, MH had no inhibitory effect on the mitochondrial DNA content. In DHBV-infected ducklings, MH significantly reduced the serum DHBV DNA, liver total viral DNA, and cccDNA levels. Furthermore, analysis of the liver pathological changes confirmed the hepatoprotective effect of MH. These results indicate that MH efficiently inhibits HBV replication both in vitro and in vivo and that MH may be a major bioactive ingredient in H. angustifolia.

An efficient antiviral strategy for targeting hepatitis B virus genome using transcription activator-like effector nucleases

The hepatitis B virus (HBV) is a DNA virus that can cause chronic hepatitis B (CHB) in humans. Current therapies for CHB infection are limited in efficacy and do not target the pre-existing viral genomic DNA, which are present in the nucleus as a covalently closed circular DNA (cccDNA) form. The transcription activator-like (TAL) effector nucleases (TALENs) are newly developed enzymes that can cleave sequence-specific DNA targets. Here, TALENs targeting the conserved regions of the viral genomic DNA among different HBV genotypes were constructed. The expression of TALENs in Huh7 cells transfected with monomeric linear full-length HBV DNA significantly reduced the viral production of HBeAg, HBsAg, HBcAg, and pgRNA, resulted in a decreased cccDNA level and misrepaired cccDNAs without apparent cytotoxic effects. The anti-HBV effect of TALENs was further demonstrated in a hydrodynamic injection-based mouse model. In addition, an enhanced antiviral effect with combinations of TALENs and interferon-α (IFN-α) treatment was observed and expression of TALENs restored HBV suppressed IFN-stimulated response element-directed transcription. Taken together, these data indicate that TALENs can specifically target and successfully inactivate the HBV genome and are potently synergistic with IFN-α, thus providing a potential therapeutic strategy for treating CHB infection.

Optimal management of chronic hepatitis B patients with treatment failure and antiviral drug resistance

The management of treatment failure in patients with chronic hepatitis B, remains a clinical concern. Incomplete viral suppression and the emergence of drug resistance are key determinants of treatment failure. The correct choice of a potent first-line therapy to achieve sustained long-term suppression of viral replication provides the best chance of preventing treatment failure and drug resistance. Clinical studies have demonstrated that drugs with a high barrier to resistance have significantly lower rates of resistance compared with those with a low barrier to resistance. Management of treatment failure requires precise clinical and virological monitoring as well as early treatment intervention with appropriate noncross-resistant antivirals. Long-term surveillance of treatment efficacy and possible emergence of drug resistance is necessary in patients who have been sequentially treated with multiple antivirals. The identification of novel treatment targets remains a major research goal to improve the efficacy of current antiviral therapy through combination therapy regimens.

Anti-hepatitis B virus activities of α-DDB-FNC, a novel nucleoside-biphenyldicarboxylate compound in cells and ducks, and its anti-immunological liver injury effect in mice

Infection with hepatitis B virus (HBV) continues to be a major global cause of acute and chronic liver disease with high mortality. Herein, we examined both the anti-HBV and hepatoprotective activity of α-DDB-FNC. In human HBV-transfected liver cell line HepG2.2.15, α-DDB-FNC effectively suppressed the secretion of HBV antigens in a time and dose-dependent manner with 25.11% inhibition on HBeAg and 43.68% on HBsAg at 2.5 μM on day 9. Consistent with the HBV antigen reduction, α-DDB-FNC (2.5 μM) also reduced HBV DNA level by 77.74% extracellularly and 78.94% intracellularly on day 9. In the duck hepatitis B virus (DHBV) infected ducks, after α-DDB-FNC was given once daily for 10 days, the serum and liver DHBV DNA levels were reduced markedly with 96.81% and 97.21% at 10 mgkg(-1) on day 10, respectively. In Con A-induced immunological liver-injury mice, α-DDB-FNC significantly inhibited the elevation of serum ALT, AST, TBiL and liver MDA, NO levels. Furthermore, significant improvement of the liver was observed after α-DDB-FNC treatment both in ducks and mice, as evaluated by the histopathological analysis. In conclusion, our results demonstrated that α-DDB-FNC possesses both antiviral activity against HBV and hepatoprotective effect to Con A-induced liver-injury mice.

Are novel combination therapies needed for chronic hepatitis B?

The treatment of chronic hepatitis B remains limited to monotherapy with pegInterferon-alpha or one of 5 different nucleoside analogues (NUC). While viral suppression can be achieved in approximately 95% of patients with new-generation NUCs, the rate of HBeAg seroconversion ranges from only 20% with NUCs to 30% with pegInterferon-alpha. HBsAg loss is achieved in only 10% of patients with both classes of drugs after a follow-up of 5years. Attempts to improve the response by administering two different NUCs or a combination of NUC and pegInterferon-alpha have been unsuccessful. This situation has led researchers to investigate a number of steps in the HBV replication cycle as potential targets for new antiviral drugs. Novel targets and compounds could readily be evaluated in in vitro and in vivo models of HBV infection. The addition of one or more new drugs to the current regimen should offer the prospect of markedly improving the response to therapy, reducing the future burden of drug resistance, cirrhosis and hepatocellular carcinoma.

Experimental models and therapeutic approaches for HBV

Liver disease associated to persistent infection with the hepatitis B virus (HBV) continues to be a major health problem of global impact. In spite of the existence of an effective vaccine, approximately 360 million people are chronically infected worldwide, who are at high risk of developing liver cirrhosis and hepatocellular carcinoma. Although current therapeutic regimens can efficiently suppress viral replication, the unique replication strategies employed by HBV permit the virus to persist within the infected hepatocytes. As a consequence, relapse of viral activity is commonly observed after cessation of treatment with polymerase inhibitors. The narrow host range of HBV has hindered progresses in understanding specific steps of HBV replication and the development of more effective therapeutic strategies aiming at achieving sustained viral control and, eventually, virus eradication. This review will focus on summarizing recent advances obtained with well-established and more innovative experimental models, giving emphasis on the strength of the different systems as tools for elucidating distinct aspects of HBV persistence and for the development of new therapeutic approaches.

Management of treatment failure in chronic hepatitis B

Antiviral therapy of chronic hepatitis B remains a clinical challenge. The primary goal of therapy is to prevent liver disease progression. Because of the mechanism of viral persistence in infected hepatocytes, long-term antiviral therapy is needed in the majority of patients. Incomplete viral suppression and emergence of drug resistance is a major concern. The correct choice of a first-line potent therapy to achieve sustained long-term suppression of viral replication provides the best chance of preventing treatment failure and drug resistance. Clinical studies have demonstrated that drugs with a high barrier to resistance, such as entecavir and tenofovir, have significantly lower rates of resistance when compared with those with a low barrier to resistance such as lamivudine, adefovir, or telbivudine. Management of treatment failure requires a precise clinical and accurate virologic monitoring as well as an early treatment intervention with appropriate complementary drugs with respect to their cross-resistance profile. Long-term surveillance for treatment efficacy and possible emergence of drug resistance is necessary for those patients who have been sequentially treated with multiple antivirals. Finally, the identification of novel treatment targets remains a major research challenge to improve the efficacy of current antiviral therapy.

Selection of chronic hepatitis B therapy with high barrier to resistance

Antiviral drug resistance is a crucial factor that frequently determines the success of long-term therapy for chronic hepatitis B. The development of resistance to nucleos(t)ide analogues has been associated with exacerbations in liver disease and increased risk of emergence of multidrug resistance. The selection of a potent nucleos(t)ide analogue with a high barrier to resistance as a first-line therapy, such as entecavir or tenofovir, provides the best chance of achieving long-term treatment goals and should be used wherever possible. The barrier to resistance of a given nucleos(t)ide analogue is influenced by genetic barrier, drug potency, patient adherence, pharmacological barrier, viral fitness, mechanism of action, and cross-resistance. In countries with limited health-care resources, the selection of a therapy with a high barrier to resistance is not always possible and alternative strategies for preventing resistance might be needed, although limited data are available to support these strategies.

In vitro anti-hepatitis B and SARS virus activities of a titanium-substituted-heteropolytungstate

A structural determined heteropolytungstate, [K₄(H₂O)₈Cl][K₄(H₂O)₄PTi₂W₁₀O₄₀]·NH₂OH 1, has been synthesized and evaluated for in vitro antiviral activities against hepatitis B (HBV) and SARS virus. The identity and high purity of compound 1 were confirmed by elemental analysis, NMR, IR analysis and single-crystal X-ray diffraction. The compound 1, evaluated in HepG 2.2.15 cells expressing permanently HBV, significantly reduced the levels of HBV antigens and HBV DNA in a dose-dependent and time-dependent manner. EC₅₀ values were determined to be 54 μM for HBeAg, 61 μM for HBsAg and 2.66 μM for supernatant HBV DNA, as compared to 1671, 1570, 169 μM, respectively, for the commercially-available hepatitis B drug adefovir dipivoxil (ADV). Intracellular cccDNA, pgRNA and HBcAg were also found to be decreased by compound 1 in a concentration-dependent manner. Cytotoxicity results showed that compound 1 has low toxicity in HepG 2 cells with CC₅₀ value of 515.20 μM. The results indicate that compound 1 can efficiently inhibit HBV replication in HepG 2.2.15 cells line in vitro. Additionally, compound 1 also shows high anti-SARS activity at an EC₅₀ of 7.08 μM and toxicity with a CC₅₀ of 118.6 μM against MDCK cells.

Development of cell cultures that express hepatitis B virus to high levels and accumulate cccDNA

Establishment of an infection with hepatitis B virus (HBV) requires synthesis and maintenance of a covalently closed circular DNA (cccDNA) form of the viral genome in the nucleus of host cells. To facilitate the investigation of the synthesis of cccDNA, cell cultures were developed that express HBV to high levels. Cell lines derived from hepatoma cells Huh7 and HepG2 were created that express Epstein-Barr virus (EBV) nuclear antigen-1 and a fusion protein of the Tet repressor and Kox1 transcriptional repression domain stably. Transfection of these cell lines with an expression plasmid for HBV that contains the origin of plasmid replication of EBV (oriP) led to increases in the intracellular levels of HBV core protein ( approximately 8- to 51-fold) and encapsidated HBV DNA ( approximately 3- to 12-fold) in comparison to Huh7 and HepG2 cells. Virion production was also increased ( approximately 3- to 12-fold) in these cell cultures and an increase in the level of cccDNA ( approximately 3-fold) was observed in the Huh7-derived cell lines. In addition, these cell lines maintained the HBV expression plasmid upon selection and expressed HBV conditionally. Thus, these cell cultures exhibit several features that facilitate study of the synthesis of cccDNA and other aspects of replication of HBV.

Hepatitis B virus resistance to nucleos(t)ide analogues

Patients with chronic hepatitis B (CHB) can be successfully treated using nucleos(t)ide analogs (NA), but drug-resistant hepatitis B virus (HBV) mutants frequently arise, leading to treatment failure and progression to liver disease. There has been much research into the mechanisms of resistance to NA and selection of these mutants. Five NA have been approved by the US Food and Drug Administration for treatment of CHB; it is unlikely that any more NA will be developed in the near future, so it is important to better understand mechanisms of cross-resistance (when a mutation that mediates resistance to one NA also confers resistance to another) and design more effective therapeutic strategies for these 5 agents. The genes that encode the polymerase and envelope proteins of HBV overlap, so resistance mutations in polymerase usually affect the hepatitis B surface antigen; these alterations affect infectivity, vaccine efficacy, pathogenesis of liver disease, and transmission throughout the population. Associations between HBV genotype and resistance phenotype have allowed cross-resistance profiles to be determined for many commonly detected mutants, so genotyping assays can be used to adapt therapy. Patients that experience virologic breakthrough or partial response to their primary therapy can often be successfully treated with a second NA, if this drug is given at early stages of these events. However, best strategies for preventing NA resistance include first-line use of the most potent antivirals with a high barrier to resistance. It is important to continue basic research into HBV replication and pathogenic mechanisms to identify new therapeutic targets, develop novel antiviral agents, design combination therapies that prevent drug resistance, and decrease the incidence of complications of CHB.

Control of cccDNA function in hepatitis B virus infection

The template of hepatitis B virus (HBV) transcription, the covalently closed circular DNA (cccDNA), plays a key role in the life cycle of the virus and permits the persistence of infection. Novel molecular techniques have opened new possibilities to investigate the organization and the activity of the cccDNA minichromosome in vivo, and recent advances have started to shed light on the complexity of the mechanisms controlling cccDNA function. Nuclear cccDNA accumulates in hepatocyte nuclei as a stable minichromosome organized by histone and non-histone viral and cellular proteins. Identification of the molecular mechanisms regulating cccDNA stability and its transcriptional activity at the RNA, DNA and epigenetic levels in the course of chronic hepatitis B (CH-B) infection may reveal new potential therapeutic targets for anti-HBV drugs and hence assist in the design of strategies aimed at silencing and eventually depleting the cccDNA reservoir.

Pathobiology of HBV mutants and clinical impact for treatment monitoring

HBV is the leading cause of liver cancer and frequently leads to cirrhosis and liver failure. The goals of nucleos(t)ide analog treatments are to suppress viral replication to as low as possible, to halt disease progression and to prevent the onset of complications. Due to the mechanism of viral genome persistence, chronic hepatitis B requires long-term therapy that exposes patients to the risk of selection of resistant mutants and treatment failure. Genotypic resistance is defined as the detection of resistant mutations that are known to confer resistance to antiviral drugs. Virologic rebound is defined as an increase in viral load of at least 1 log(10) copies/ml compared with the lowest value during therapy. Clinical breakthrough is defined as a rise in alanine aminotransferase levels and liver disease progression following the emergence of resistant mutants and the rise in viral load. Currently, the management of antiviral therapy should be based on precise virologic monitoring to enable an early diagnosis of partial response and treatment failure. An early treatment adaptation is recommended at least at the time of virologic breakthrough or in the case of insufficient viral suppression. The choice of drug for second-line therapy should be based on cross-resistance data to tailor therapy to the virologic situation of the patient. The addition of a complementary drug is the preferred strategy. Clinical experience shows that an optimal management of antiviral therapy allows the control of viral replication in the majority of patients in whom liver disease progression is halted.

Persistence of the hepatitis B virus covalently closed circular DNA in HepaRG human hepatocyte-like cells

The recently described hepatic cell line HepaRG is the sole hepatoma cell line susceptible to hepatitis B virus (HBV) infection. It provides a unique tool for investigating some unresolved issues of the virus' biology, particularly the formation of the viral mini-chromosome believed to be responsible for the persistence of infection. In this study, we characterized the main features of HBV infection: it is restricted to a subpopulation of differentiated hepatocyte-like cells that express albumin as a functional marker and represents around 10 % of all differentiated HepaRG cells. Infection may persist for more than 100 days in cells maintained at the differentiated state. Even though infected cells continued to produce infectious viral particles, very limited or no spreading of infection was observed. Low genetic variation was also observed in the viral DNA from viruses found in the supernatant of infected cells, although this cannot explain the lack of reinfection. HBV infection of HepaRG cells appears to be a very slow process: viral replication starts at around day 8 post-infection and reaches a maximum at day 13. Analysis of viral DNA showed slow and inefficient conversion of the input relaxed circular DNA into covalently closed circular (CCC) DNA, but no further amplification. Continuous lamivudine treatment inhibited viral replication, but neither prevented viral infection nor initial formation of CCC DNA. In conclusion, HBV infection in differentiated HepaRG cells is characterized by long-term persistence without a key feature of hepadnaviruses, the so-called 'CCC DNA amplification' described in the duck hepatitis B model.

Hepatitis B: reflections on the current approach to antiviral therapy

This article summarizes the current state of antiviral therapy of hepatitis B with special attention given to areas that remain controversial or poorly defined. Strict adherence to liver association practice guidelines may result in missed opportunities to treat patients with significant underlying liver disease. In particular, recommended ALT thresholds may not appropriately reflect disease activity or degree of fibrosis. There is growing evidence that an alternative treatment paradigm for preventing late-stage disease complications may be indicated in highly viremic patients with early life exposure to hepatitis B. Pegylated interferon therapy is often a better choice for young to middle-aged patients with genotype A and B because of the higher rate of HBeAg seroconversion and a greater chance for HBsAg seroconversion in both HBeAg-positive and -negative patients as compared to nucleoside analogs. Nucleoside analog monotherapy is the current standard of care for many patients. However, long-term monotherapy results in resistance to a variable degree and sequential monotherapy may result in multi-drug resistant virus. Which patients would specifically benefit from early combination therapy also remains poorly defined. The rapidity and robustness of the suppression of HBV DNA while on a nucleoside analog should be monitored relatively early during treatment because it affects treatment outcome and the rate of resistance. While great progress has been made in treating hepatitis B, many important issues require further study.

Development of a real-time quantitative reverse transcriptase PCR assay for detection of the Friend leukemia virus load in murine plasma

Friend leukemia virus (FLV), a murine retrovirus, has been used as a model for elucidation of human immunodeficiency virus (HIV) immunopathogenesis and evaluation of anti-HIV drug effects for several decades. However, no method for direct detection of the plasma viral load has yet been reported. In this study, a TaqMan real-time quantitative reverse transcriptase PCR (qRT-PCR) assay was established for the rapid detection and quantitation of FLV. Measurement of the absolute FLV load was achieved through synthesis of a standard RNA from within the FLV envelope gene for generation of a standard curve. The assay allows quantitation over a range from 20 to 2 x 10(8) RNA copies per reaction in a two-step real-time quantitative reverse transcriptase PCR protocol. The relationships between the initially injected FLV dose and the plasma FLV load and spleen index were explored. Following this, the in vivo effects of zidovudine, adefovir dipivoxil, and entecavir on mice infected with FLV were evaluated. The results showed that the plasma FLV load was not proportional to the spleen index over the same FLV injection dosage series, although a trend was observed. When evaluated using plasma viral load, high dose (15 mg/(kg d)) adefovir dipivoxil was capable of significant inhibition of FLV replication in mice. The qRT-PCR assay described here allows specific, sensitive and direct detection of FLV and may also provide more precise measurement of FLV load.

Efficacies of β-L-D4A against hepatitis B virus in 2.2.15 cells

AIM: To investigate the antiviral effect of beta-L-enantiomer of 2’,3’-didehydro-2’,3’-dideoxyadenosine (β-L-D4A) on 2.2.15 cells transfected with the hepatitis B virus (HBV) genome.

METHODS: Lamivudine (3TC) as a positive control. Then, HBV DNA in treated 2.2.15 cells and the Hepatitis B surface antigen (HBsAg) in the culture supernatants were detected to determine the inhibitory effect of β-L-D4A. At the same time, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was used to detect the survival ratio of 2.2.15 cells.

RESULTS: β-L-D4A has a dose-dependent inhibitory effect on HBV DNA replication; this effect was apparent when the concentration was above 1 mol/L. When β-L-D4A was at the highest concentration, 100 mol/L, the HBsAg inhibition ratio was above 50%. The Therapeutic index (TI) of β-L-D4A was above 2.1.

CONCLUSION: β-L-D4A has a dose-dependent inhibitory effect on the replication of HBV DNA and the secretion of HBsAg at low toxicity.

Switching patients with lamivudine resistant chronic hepatitis B virus from tenofovir to adefovir results in less potent HBV-DNA suppression

The nucleotide analogues, tenofovir disoproxil fumarate and adefovir dipivoxil, inhibit viral replication and are both effective against the hepatitis B virus (HBV). In our department, tenofovir was prescribed in addition to lamivudine for the treatment of lamivudine resistant chronic hepatitis B. After registration of adefovir, 10 patients were switched to adefovir monotherapy. We studied changes in HBV-DNA and alanine aminotransferase (ALT) in these patients. The median treatment duration with tenofovir was 78 weeks resulting in a median viral load reduction of 5.4 (range 6.8-2.3) log(10) copies/mL compared to baseline (P = 0.005). Two patients had an increase >1 log(10) copies/mL during tenofovir treatment. After the switch to adefovir, six out of 10 patients had an HBV-DNA >4 log(10) copies/mL and the median HBV-DNA increased from 2.8 to 4.5 log(10) copies/mL (P = 0.017). The factors associated with relapse were HBV-DNA PCR positivity at the time of switch and genotype B or D. ALT levels at the beginning of tenofovir treatment also might be a factor. Retreatment with tenofovir (n = 3) resulted in a rapid decline in HBV-DNA. Tenofovir is a potent antiviral drug. Switching to adefovir resulted in viral relapse in 60% of patients and retreatment with tenofovir resulted again in viral decline, which suggests that tenofovir is a more potent antiviral agent.

Antiviral-resistant hepatitis B virus: can we prevent this monster from growing?

Despite the recent progress in antiviral therapy of chronic hepatitis B, clinical experience has shown that antiviral drug resistance is inevitable with the administration of nucleoside analog monotherapy. The long-term persistence of the viral genome in infected cells and the high rate of spontaneous mutation is the basis for the selection of HBV mutants that are resistant to polymerase inhibitors. Selection of antiviral-resistant mutations leads to a rise in viral load and progression of liver disease. The incidence of antiviral resistance depends on the potency and genetic barrier to resistance of the antiviral drug, highlighting the importance of the choice if first line therapy. The determination of cross-resistance profile of each drug has allowed the design of rescue therapy for patients with virologic breakthrough. Early diagnosis and treatment intervention allow the majority of patients to maintain in clinical remission despite the occurrence of drug resistance. Clinical studies are ongoing to determine the best strategy to prevent or delay antiviral drug resistance and of its impact on liver disease.