Production of hepatitis B virus particles in Hep G2 cells transfected with cloned hepatitis B virus DNA

Discovery of Small Molecule Therapeutics for Treatment of Chronic HBV Infection

The chronic infection of hepatitis B virus (HBV) inflicts 250 million people worldwide representing a major public health threat. A significant subpopulation of patients eventually develop cirrhosis and hepatocellular carcinoma (HCC). Unfortunately, none of the current standard therapies for chronic hepatitis B (CHB) result in a satisfactory clinical cure rate. Driven by a highly unmet medical need, multiple pharmaceutical companies and research institutions have been engaged in drug discovery and development to improve the CHB functional cure rate, defined by sustainable viral suppression and HBsAg clearance after a finite treatment. This Review summarizes the recent advances in the discovery and development of novel anti-HBV small molecules. It is believed that an improved CHB functional cure rate may be accomplished via the combination of molecules with distinct MoAs. Thus, certain molecules may evolve into key components of a suitable combination therapy leading to superior outcome of clinical efficacy in the future.

Inhibition of pMAPK14 Overcomes Resistance to Sorafenib in Hepatoma Cells with Hepatitis B Virus

Hepatitis B virus (HBV) targets the liver and is a major driver for liver cancer. Clinical data suggest that HBV infection is associated with reduced response to treatment with the multi-kinase inhibitor sorafenib, the first available molecularly targeted anti-hepatocellular carcinoma (HCC) drug. Given that Raf is one of the major targets of sorafenib, we investigated the activation state of the Raf-Mek-Erk pathway in the presence of HBV and in response to sorafenib. Here we show that hepatoma cells with replicating HBV are less susceptible to sorafenib inhibitory effect as compared to cells in which HBV expression is suppressed. However, although HBV replication is associated with increased level of pErk, its blockade only modestly augments sorafenib effect. In contrast, the phosphorylated form of the pro-oncogenic Mitogen-Activated Protein Kinase 14 (pMAPK14), a protein kinase that was recently linked to sorafenib resistance, is induced in sorafenib-treated hepatoma cells in association with HBV X protein expression. Knocking down pMAPK14 results in augmentation of the therapeutic efficacy of sorafenib and largely alleviates resistance to sorafenib in the presence of HBV. Thus, this study suggests that HBV promotes HCC resistance to sorafenib. Combining pMAPK14 inhibitors with sorafenib may be beneficial in patients with HBV-associated HCC.

Novel stable HBV producing cell line systems for expression and screening antiviral inhibitor of hepatitis B virus in human hepatoma cell line

Chronic hepatitis B virus (HBV) infection is currently a major public health burden. Therefore, there is an urgent need for the development of novel antiviral inhibitors. The stable HBV-producing cell lines of genotype D are widely used to investigate the HBV life cycle and to evaluate antiviral agents. However, stable HBV-producing cell lines of different genotypes do not exist. To construct more convenient and efficient novel cell systems, stable cell lines of genotypes A, B, and C were established using a full-length HBV genome sequence isolated from chronic HBV patients in human hepatoma HepG2 cells. Novel HBV clones were identified and stable HBV-producing cell lines derived from these clones were constructed. HBV replication activities demonstrated time-dependent expression, and the novel cell lines were susceptible to several antiviral inhibitors with no cytotoxicity. Furthermore, infectious viruses were produced from these cell lines. In conclusion, we have established novel stable HBV-producing cell line systems of genotypes A, B, and C. These systems can provide valuable tools for screening antiviral agents and analyzing viral phenotypes in vitro.

C-terminal truncated hepatitis B virus X protein promotes hepatocellular carcinogenesis through induction of cancer and stem cell-like properties

Tumor relapse after chemotherapy typifies hepatocellular carcinoma (HCC) and is believed to be attributable to residual cancer stem cells (CSCs) that survive initial treatment. Chronic infection with hepatitis B virus (HBV) has long been linked to the development of HCC. Upon infection, random HBV genome integration can lead to truncation of hepatitis B virus X (HBx) protein at the C-terminus. The resulting C-terminal-truncated HBx (HBx-ΔC) was previously shown to confer enhanced invasiveness and diminished apoptotic response in HCC cells. Here, we found HBx-ΔC to promote the appearance of a CD133 liver CSC subset and confer cancer and stem cell-like features in HCC. HBx-ΔC was exclusively detected in HCC cell lines that were raised from patients presented with a HBV background with concomitant CD133 expression. Stable overexpression of the naturally occurring HBx-ΔC mutants, HBx-Δ14 or HBx-Δ35, in HCC cells Huh7 and immortalized normal liver cells MIHA resulted in a significant increase in the cells ability to self-renew, resist chemotherapy and targeted therapy, migrate and induce angiogenesis. MIHA cells with the mutants stably overexpressed also resulted in the induction of CD133, mediated through STAT3 activation. RNA sequencing profiling of MIHA cells with or without HBx-ΔC mutants stably overexpressed identified altered FXR activation. This, together with rescue experiments using a selective FXR inhibitor suggested that C-terminal truncated HBx can mediate cancer stemness via FXR activation. Collectively, we find C-terminal truncated HBx mutants to confer cancer and stem cell-like features in vitro and to play an important role in driving tumor relapse in HCC.

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.

A T7 Endonuclease I Assay to Detect Talen-Mediated Targeted Mutation of HBV cccDNA

Gene editing using designer nucleases is now widely used in many fields of molecular biology. The technology is being developed for the treatment of viral infections such as persistant hepatitis B virus (HBV). The replication intermediate of HBV comprising covalently closed circular DNA (cccDNA) is stable and resistant to available licensed antiviral agents. Advancing gene editing as a means of introducing targeted mutations into cccDNA thus potentially offers the means to cure infection by the virus. Essentially, targeted mutations are initiated by intracellular DNA cleavage, then error-prone nonhomologous end joining results in insertions and deletions (indels) at intended sites. Characterization of these mutations is crucial to confirm activity of potentially therapeutic nucleases. A convenient tool for evaluation of the efficiency of target cleavage is the single strand-specific endonuclease, T7EI. Assays employing this enzyme entail initial amplification of DNA encompassing the targeted region. Thereafter the amplicons are denatured and reannealed to allow hybridization between indel-containing and wild-type sequences. Heteroduplexes that contain mismatched regions are susceptible to action by T7EI and cleavage of the hybrid amplicons may be used as an indicator of efficiency of designer nucleases. The protocol described here provides a method of isolating cccDNA from transfected HepG2.2.15 cells and evaluation of the efficiency of mutation by a transcription activator-like effector nuclease that targets the surface open reading frame of HBV.

Current concepts on immunopathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) infection is a leading cause of liver damage and hepatic inflammation. Upon infection, effective antiviral responses by CD8+ T cells, CD4+ T cells, Natural killer (NK) cells, and monocytes can lead to partial or complete eradication of the viral infection. To date, many studies have shown that the production of inhibitory cytokines such as Interleukin 10 (IL-10), Transforming growth factor beta (TGF-β), along with dysfunction of the dendritic cells (DCs), and the absence of efficient innate immune responses could lead to T cell exhaustion, development of persistent infection, and inability to eradicate the viral infection from liver. Understanding the immunopathogenesis of the virus could be useful in providing further insights toward novel strategies in the eradication of HBV infection.

Luteolin-7-O-Glucoside Present in Lettuce Extracts Inhibits Hepatitis B Surface Antigen Production and Viral Replication by Human Hepatoma Cells in Vitro

Hepatitis B virus (HBV) infection is endemic in Asia and chronic hepatitis B (CHB) is a major public health issue worldwide. Current treatment strategies for CHB are not satisfactory as they induce a low rate of hepatitis B surface antigen (HBsAg) loss. Extracts were prepared from lettuce hydroponically cultivated in solutions containing glycine or nitrate as nitrogen sources. The lettuce extracts exerted potent anti-HBV effects in HepG2 cell lines in vitro, including significant HBsAg inhibition, HBV replication and transcription inhibition, without exerting cytotoxic effects. When used in combination interferon-alpha 2b (IFNα-2b) or lamivudine (3TC), the lettuce extracts synergistically inhibited HBsAg expression and HBV replication. By using differential metabolomics analysis, Luteolin-7-O-glucoside was identified and confirmed as a functional component of the lettuce extracts and exhibited similar anti-HBV activity as the lettuce extracts in vitro. The inhibition rate on HBsAg was up to 77.4%. Moreover, both the lettuce extracts and luteolin-7-O-glucoside functioned as organic antioxidants and, significantly attenuated HBV-induced intracellular reactive oxygen species (ROS) accumulation. Luteolin-7-O-glucoside also normalized ROS-induced mitochondrial membrane potential damage, which suggests luteolin-7-O-glucoside inhibits HBsAg and HBV replication via a mechanism involving the mitochondria. Our findings suggest luteolin-7-O-glucoside may have potential value for clinical application in CHB and may enhance HBsAg and HBV clearance when used as a combination therapy.

ZEB2 inhibits HBV transcription and replication by targeting its core promoter

Hepatitis B virus (HBV) infection is a major cause of liver diseases, especially liver cirrhosis and hepatocellular carcinoma. However, the interaction between host and HBV has not been fully elucidated. ZEB2 is a Smad-interacting, multi-zinc finger protein that acts as a transcription factor or repressor for several signaling pathways. This study found that the expression of ZEB2 was decreased in HBV-expressing cells. Overexpression of ZEB2 inhibited HBV DNA replicative intermediates, 3.5kb mRNA, core protein level, and the secretion of HBsAg and HBeAg. In contrast, ZEB2 knockdown promoted HBV replication. Furthermore, ZEB2 could bind to HBV core promoter and inhibit its promoter activity. Mutation at the ZEB2 binding site in HBV core promoter eradicated ZEB2-mediated inhibition of HBV replication. This study identifies ZEB2 as a novel host restriction factor that inhibits HBV replication in hepatocytes. These data may shed light on development of new antiviral strategies.

Detection of hepatitis B virus DNA and HBsAg from postmortem blood and bloodstains

A large number of accidental virus infections occur in medical and non-medical workers exposed to infectious individuals and materials. We evaluated whether postmortem blood and bloodstains containing hepatitis B virus (HBV) are infectious. HBV-infected blood and bloodstains were stored for up to 60 days at room temperature and subsequently screened for hepatitis B surface antigen (HBsAg) and HBV DNA. In addition, HBV-positive postmortem blood was added to a cell line and the production of HBV virions was examined over a period of 7 days. HBsAg and HBV DNA were detected in all samples stored for 60 days at room temperature. HBV-positive postmortem blood successfully infected the cell line and progeny viruses were produced for up to 6 days. Thus, it is crucial that due care is taken when handling not only living material infected with HBV, as well as other harmful viruses, but also blood or body fluids from cadavers or medical waste.

Viral Load Affects the Immune Response to HBV in Mice With Humanized Immune System and Liver

BACKGROUND & AIMS

Hepatitis B virus (HBV) infects hepatocytes, but the mechanisms of the immune response against the virus and how it affects disease progression are unclear.

METHODS

We performed studies with BALB/c Rag2^-/-Il2rg^-/-Sirpa^NODAlb-uPA^tg/tg mice, stably engrafted with human hepatocytes (HUHEP) with or without a human immune system (HIS). HUHEP and HIS-HUHEP mice were given an intraperitoneal injection of HBV. Mononuclear cells were isolated from spleen and liver for analysis by flow cytometry. Liver was analyzed by immunohistochemistry and mRNA levels were measured by quantitative reverse transcription polymerase chain reaction (PCR). Plasma levels of HBV DNA were quantified by PCR reaction, and antigen-specific antibodies were detected by immunocytochemistry of HBV-transfected BHK-21 cells.

RESULTS

Following HBV infection, a complete viral life cycle, with production of HBV DNA, hepatitis B e (HBe), core (HBc) and surface (HBs) antigens, and covalently closed circular DNA, was observed in HUHEP and HIS-HUHEP mice. HBV replicated unrestricted in HUHEP mice resulting in high viral titers without pathologic effects. In contrast, HBV-infected HIS-HUHEP mice developed chronic hepatitis with 10-fold lower titers and antigen-specific IgGs, (anti-HBs, anti-HBc), consistent with partial immune control. HBV-infected HIS-HUHEP livers contained infiltrating Kupffer cells, mature activated natural killer cells (CD69+), and PD-1+ effector memory T cells (CD45RO+). Reducing the viral inoculum resulted in more efficient immune control. Plasma from HBV-infected HIS-HUHEP mice had increased levels of inflammatory and immune-suppressive cytokines (C-X-C motif chemokine ligand 10 and interleukin 10), which correlated with populations of intrahepatic CD4+ T cells (CD45RO+PD-1+). Mice with high levels of viremia had HBV-infected liver progenitor cells. Giving the mice the nucleoside analogue entecavir reduced viral loads and decreased liver inflammation.

CONCLUSION

In HIS-HUHEP mice, HBV infection completes a full life cycle and recapitulates some of the immunopathology observed in patients with chronic infection. Inoculation with different viral loads led to different immune responses and levels of virus control. We found HBV to infect liver progenitor cells, which could be involved in hepatocellular carcinogenesis. This is an important new system to study anti-HBV immune responses and screen for combination therapies against hepatotropic viruses.

Engineered Livers for Infectious Diseases

Engineered liver systems come in a variety of platform models, from 2-dimensional cocultures of primary human hepatocytes and stem cell-derived progeny, to 3-dimensional organoids and humanized mice. Because of the species-specificity of many human hepatropic pathogens, these engineered systems have been essential tools for biologic discovery and therapeutic agent development in the context of liver-dependent infectious diseases. Although improvement of existing models is always beneficial, and the addition of a robust immune component is a particular need, at present, considerable progress has been made using this combination of research platforms. We highlight advances in the study of hepatitis B and C viruses and malaria-causing Plasmodium falciparum and Plasmodium vivax parasites, and underscore the importance of pairing the most appropriate model system and readout modality with the particular experimental question at hand, without always requiring a platform that recapitulates human physiology in its entirety.

Hepatitis B virus inhibits the in vivo and in vitro synthesis and secretion of apolipoprotein C3

BACKGROUND

Hepatitis B virus (HBV) infection in the body can damage liver cells and cause disorders in blood lipid metabolism. Apolipoprotein C3 (ApoC3) plays an important role in the regulation of lipid metabolism, but no study on the HBV regulation of ApoC3 has been reported. This purpose of this study was to investigate the effect of HBV on ApoC3 expression and its regulatory mechanism.

METHODS

The expression levels of ApoC3 mRNA and protein in the human hepatoma cell lines HepG2 and HepG2.2.15 were determined using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. The HepG2 cells were co-transfected with the ApoC3 gene promoter and either HBV-infected clone pHBV1.3 or its individual genes. The changes in luciferase activity were assayed. The expression levels of ApoC3 mRNA and protein were determined using RT-qPCR and Western blot. The content of ApoC3 in the supernatant of the cultured cells was determined using an enzyme-linked immunosorbent assay (ELISA). The sera were collected from 149 patients with HBV infection and 102 healthy subjects at physical examination as the normal controls. The serological levels of ApoC3 in the HBV group and the normal control group were determined using ELISA. The contents of serum triglyceride (TG) and very-low-density lipoprotein (VLDL) in the HBV patients and the normal control were determined using an automatic biochemical analyser.

RESULTS

The expression levels of ApoC3 mRNA and protein were lower in the HepG2.2.15 cells than in the HepG2 cells. pHBV1.3 and its X gene could inhibit the activity of the ApoC3 promoter and its mRNA and protein expression. The serum levels of ApoC3, VLDL and TG were 65.39 ± 7.48 μg/ml, 1.24 ± 0.49 mmol/L, and 0.46 ± 0.10 mmol/L in the HBV patients and 41.02 ± 6.88 μg/ml, 0.76 ± 0.21 mmol/L, 0.29 ± 0.05 mmol/L in the normal controls, respectively, statistical analysis revealed significantly lower serum levels of ApoC3, VLDL and TG in HBV patients than in the normal controls (P < 0.05).

CONCLUSION

HBV can inhibit the in vivo and in vitro synthesis and secretion of ApoC3.

HBsAg mRNA degradation induced by a dihydroquinolizinone compound depends on the HBV posttranscriptional regulatory element

In pursuit of novel therapeutics targeting the hepatitis B virus (HBV) infection, we evaluated a dihydroquinolizinone compound (DHQ-1) that in the nanomolar range reduced the production of virion and surface protein (HBsAg) in tissue culture. This compound also showed broad HBV genotype coverage, but was inactive against a panel of DNA and RNA viruses of other species. Oral administration of DHQ-1 in the AAV-HBV mouse model resulted in a significant reduction of serum HBsAg as soon as 4 days following the commencement of treatment. Reduction of HBV markers in both in vitro and in vivo experiments was related to the reduced amount of viral RNA including pre-genomic RNA (pgRNA) and 2.4/2.1 kb HBsAg mRNA. Nuclear run-on and subcellular fractionation experiments indicated that DHQ-1 mediated HBV RNA reduction was the result of accelerated viral RNA degradation in the nucleus, rather than the consequence of inhibition of transcription initiation. Through mutagenesis of HBsAg gene sequences, we found induction of HBsAg mRNA decay by DHQ-1 required the presence of the HBV posttranscriptional regulatory element (HPRE), with a 109 nucleotides sequence within the central region of the HPRE alpha sub-element being the most critical. Taken together, the current study shows that a small molecule can reduce the overall levels of HBV RNA, especially the HBsAg mRNA, and viral surface proteins. This may shed light on the development of a new class of HBV therapeutics.

Targeting blockage of STAT3 inhibits hepatitis B virus-related hepatocellular carcinoma

Hepatitis B virus (HBV) infection is a significant cause of liver disease pathogenesis, which results in the development of hepatic dysfunction, cirrhosis and hepatocellular carcinoma (HCC). Our previous studies showed that oncogene STAT3 might be an ideal target for HCC therapy. Here, we investigated whether targeting blockage of STAT3 signaling is efficient for HBV-related HCC. Based on the refractory of HCC and the persistence of HBV, in this study, we designed shRNAs targeting STAT3. The results showed that blocking STAT3 signaling by shRNAs could promote HBV positive HCC cell apoptosis and induce cell cycle arrest, resulting in HCC cell growth inhibition in vitro. Importantly, STAT3-shRNAs efficiently suppressed HBV replication, which would reduce HBV-derived stimulation to STAT3 signaling and augment STAT3-shRNAs-mediated anti-HCC effect. Finally, STAT3-shRNAs-mediated anti-HBV positive HCC effect was confirmed in xenograft nude mice. This study suggested that targeting STAT3 therapies such as STAT3-shRNAs may be an efficacious strategy for HBV-related HCC.

Transcriptional Elongation Control of Hepatitis B Virus Covalently Closed Circular DNA Transcription by Super Elongation Complex and BRD4

Chronic hepatitis B virus (HBV) infection can lead to liver cirrhosis and hepatocellular carcinoma. HBV reactivation during or after chemotherapy is a potentially fatal complication for cancer patients with chronic HBV infection. Transcription of HBV is a critical intermediate step of the HBV life cycle. However, factors controlling HBV transcription remain largely unknown. Here, we found that different P-TEFb complexes are involved in the transcription of the HBV viral genome. Both BRD4 and the super elongation complex (SEC) bind to the HBV genome. The treatment of bromodomain inhibitor JQ1 stimulates HBV transcription and increases the occupancy of BRD4 on the HBV genome, suggesting the bromodomain-independent recruitment of BRD4 to the HBV genome. JQ1 also leads to the increased binding of SEC to the HBV genome, and SEC is required for JQ1-induced HBV transcription. These findings reveal a novel mechanism by which the HBV genome hijacks the host P-TEFb-containing complexes to promote its own transcription. Our findings also point out an important clinical implication, that is, the potential risk of HBV reactivation during therapy with a BRD4 inhibitor, such as JQ1 or its analogues, which are a potential treatment for acute myeloid leukemia.

Functional association of cellular microtubules with viral capsid assembly supports efficient hepatitis B virus replication

Viruses exploit host factors and environment for their efficient replication. The virus-host interaction mechanisms for achieving an optimal hepatitis B virus (HBV) replication have been largely unknown. Here, a single cell cloning revealed that HepAD38 cells, a widely-used HBV-inducible cell line, contain cell clones with diverse permissiveness to HBV replication. The HBV permissiveness was impaired upon treatment with microtubule inhibitor nocodazole, which was identified as an HBV replication inhibitor from a pharmacological screening. In the microtubule-disrupted cells, the efficiency of HBV capsid assembly was remarkably decreased without significant change in pre-assembly process. We further found that HBV core interacted with tubulin and co-localized with microtubule-like fibriforms, but this association was abrogated upon microtubule-disassembly agents, resulting in attenuation of capsid formation. Our data thus suggest a significant role of microtubules in the efficient capsid formation during HBV replication. In line with this, a highly HBV permissive cell clone of HepAD38 cells showed a prominent association of core-microtubule and thus a high capacity to support the capsid formation. These findings provide a new aspect of virus-cell interaction for rendering efficient HBV replication.

Interference of Apoptosis by Hepatitis B Virus

Hepatitis B virus (HBV) causes liver diseases that have been a consistent problem for human health, leading to more than one million deaths every year worldwide. A large proportion of hepatocellular carcinoma (HCC) cases across the world are closely associated with chronic HBV infection. Apoptosis is a programmed cell death and is frequently altered in cancer development. HBV infection interferes with the apoptosis signaling to promote HCC progression and viral proliferation. The HBV-mediated alteration of apoptosis is achieved via interference with cellular signaling pathways and regulation of epigenetics. HBV X protein (HBX) plays a major role in the interference of apoptosis. There are conflicting reports on the HBV interference of apoptosis with the majority showing inhibition of and the rest reporting induction of apoptosis. In this review, we described recent studies on the mechanisms of the HBV interference with the apoptosis signaling during the virus infection and provided perspective.

Plasma MicroRNA Levels Are Associated With Hepatitis B e Antigen Status and Treatment Response in Chronic Hepatitis B Patients

Background

Hepatitis B virus (HBV) modulates microRNA (miRNA) expression to support viral replication. The aim of this study was to identify miRNAs associated with hepatitis B e antigen (HBeAg) status and response to antiviral therapy in patients with chronic hepatitis B (CHB) , and to assess if these miRNAs are actively secreted by hepatoma cells.

Methods

Plasma miRNA levels were measured by reverse-transcription quantitative polymerase chain reaction in healthy controls (n = 10) and pretreatment samples of an identification cohort (n = 24) and a confirmation cohort (n = 64) of CHB patients treated with peginterferon/nucleotide analogue combination therapy. Levels of HBV-associated miRNAs were measured in cells, extracellular vesicles, and hepatitis B surface antigen (HBsAg) particles of hepatoma cell lines.

Results

HBeAg-positive patients had higher plasma levels of miR-122-5p, miR-125b-5p, miR-192-5p, miR-193b-3p, and miR-194-5p compared to HBeAg-negative patients, and levels of these miRNAs were associated with HBV DNA and HBsAg levels. Pretreatment plasma levels of miR-301a-3p and miR-145-5p were higher in responders (combined response or HBsAg loss) compared to nonresponders. miR-192-5p, miR-193b-3p, and miR-194-5p were present in extracellular vesicles and HBsAg particles derived from hepatoma cells.

Conclusions

We identified miRNAs that are associated with HBeAg status, levels of HBV DNA and HBsAg, and treatment response in CHB patients. We demonstrated that several of these miRNAs are present in extracellular vesicles and HBsAg particles secreted by hepatoma cells.

Methyltransferase SETD2-Mediated Methylation of STAT1 Is Critical for Interferon Antiviral Activity

Interferon-α (IFNα) signaling is essential for antiviral response via induction of IFN-stimulated genes (ISGs). Through a non-biased high-throughput RNAi screening of 711 known epigenetic modifiers in cellular models of IFNα-mediated inhibition of HBV replication, we identified methyltransferase SETD2 as a critical amplifier of IFNα-mediated antiviral immunity. Conditional knockout mice with hepatocyte-specific deletion of Setd2 exhibit enhanced HBV infection. Mechanistically, SETD2 directly mediates STAT1 methylation on lysine 525 via its methyltransferase activity, which reinforces IFN-activated STAT1 phosphorylation and antiviral cellular response. In addition, SETD2 selectively catalyzes the tri-methylation of H3K36 on promoters of some ISGs such as ISG15, leading to gene activation. Our study identifies STAT1 methylation on K525 catalyzed by the methyltransferase SETD2 as an essential signaling event for IFNα-dependent antiviral immunity and indicates potential of SETD2 in controlling viral infections.

ssAAVs containing cassettes encoding SaCas9 and guides targeting hepatitis B virus inactivate replication of the virus in cultured cells

Management of infection with hepatitis B virus (HBV) remains a global health problem. Persistence of stable covalently closed circular DNA (cccDNA) during HBV replication is responsible for modest curative efficacy of currently licensed drugs. Novel gene editing technologies, such as those based on CRISPR/Cas9, provide the means for permanently disabling cccDNA. However, efficient delivery of antiviral sequences to infected hepatocytes is challenging. A limiting factor is the large size of sequences encoding Cas9 from Streptococcus pyogenes, and resultant incompatibility with the popular single stranded adeno-associated viral vectors (ssAAVs). We thus explored the utility of ssAAVs for delivery of engineered CRISPR/Cas9 of Staphylococcus aureus (Sa), which is encoded by shorter DNA sequences. Short guide RNAs (sgRNAs) were designed with cognates in the S open reading frame of HBV and incorporated into AAVs that also encoded SaCas9. Intended targeted mutation of HBV DNA was observed after transduction of cells with the all-in-one vectors. Efficacy against HBV-infected hNTCP-HepG2 cells indicated that inactivation of cccDNA was successful. Analysis of likely off-target mutagenesis revealed no unintended sequence changes. Use of ssAAVs to deliver all components required to disable cccDNA by SaCas9 is novel and the technology has curative potential for HBV infection.

Hepatitis B virus prevents excessive viral production via reduction of cell death-inducing DFF45-like effectors

The relationship between hepatitis B virus (HBV) infection and lipid accumulation remains largely unknown. In this study, we investigated the effect of HBV propagation on lipid droplet growth in HBV-infected cells and HBV-producing cell lines, HepG2.2.15 and HBV-inducible Hep38.7-Tet. The amount of intracellular triglycerides was significantly reduced in HBV-infected and HBV-producing cells compared with HBV-lacking control cells. Electron and immunofluorescent microscopic analyses showed that the average size of a single lipid droplet (LD) was significantly less in the HBV-infected and HBV-producing cells than in the HBV-lacking control cells. Cell death-inducing DFF45-like effectors (CIDEs) B and C (CIDEB and CIDEC), which are involved in LD expansion for the improvement of lipid storage, were expressed at a significantly lower level in HBV-infected or HBV-producing cells than in HBV-lacking control cells, while CIDEA was not detected in those cells regardless of HBV production. The activity of the CIDEB and CIDEC gene promoters was impaired in HBV-infected or HBV-producing cells compared to HBV-lacking control cells, while CIDEs potentiated HBV core promoter activity. The amount of HNF4α, that can promote the transcription of CIDEB was significantly lower in HBV-producing cells than in HBV-lacking control cells. Knockout of CIDEB or CIDEC significantly reduced the amount of supernatant HBV DNA, intracellular viral RNA and nucleocapsid-associated viral DNA, while the expression of CIDEB or CIDEC recovered HBV production in CIDEB- or CIDEC-knockout cells. These results suggest that HBV regulates its own viral replication via CIDEB and CIDEC.

HBV suppresses thapsigargin-induced apoptosis via inhibiting CHOP expression in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) accounts for a proportion of cancer-associated mortalities worldwide. Hepatitis B virus (HBV) infection is a major cause of HCC in China. Thapsigargin (TG) is a potential antitumor prodrug, eliciting endoplasmic reticulum (ER) stress via the inhibition of the ER calcium pump, effectively inducing apoptosis. The present study therefore examined the role of HBV in TG-induced apoptosis using two HCC cell lines, HBV positive HepG2.2.15 and HBV negative HepG2. When these two cell lines were treated with TG, HepG2.2.15 was less susceptible to apoptosis than HepG2. This phenomenon was confirmed by an MTT assay and Annexin V-FITC/propidium iodide staining. Reverse transcription quantitative polymerase chain reaction and western blotting were used to detect the expression levels of genes in the ER stress pathway subsequent to treatment with TG. Notably, the mRNA and protein levels of the apoptosis factor DNA damage inducible transcript 3 (CHOP) increased significantly in the HepG2 cells compared with the HepG2.2.15 cells. Additionally, the HepG2.2.15 cells treated with interferon-α exhibited higher levels of CHOP compared with the untreated cells. The overexpression or knockdown of CHOP microRNA in HepG2.2.15 or HepG2 cells may reduce the difference in apoptosis status between the two cell lines. These results suggest that HBV may inhibit the apoptosis induced by ER stress. These findings may be useful in the development of selective therapies for patients with HBV-positive tumors.

Long-term hepatitis B infection in a scalable hepatic co-culture system

Hepatitis B virus causes chronic infections in 250 million people worldwide. Chronic hepatitis B virus carriers are at risk of developing fibrosis, cirrhosis, and hepatocellular carcinoma. A prophylactic vaccine exists and currently available antivirals can suppress but rarely cure chronic infections. The study of hepatitis B virus and development of curative antivirals are hampered by a scarcity of models that mimic infection in a physiologically relevant, cellular context. Here, we show that cell-culture and patient-derived hepatitis B virus can establish persistent infection for over 30 days in a self-assembling, primary hepatocyte co-culture system. Importantly, infection can be established without antiviral immune suppression, and susceptibility is not donor dependent. The platform is scalable to microwell formats, and we provide proof-of-concept for its use in testing entry inhibitors and antiviral compounds.

The lack of models that mimic hepatitis B virus (HBV) infection in a physiologically relevant context has hampered drug development. Here, Winer et al. establish a self-assembling, primary hepatocyte co-culture system that can be infected with patient-derived HBV without further modifications.

Hepatitis B Virus Capsid Assembly Modulators, but Not Nucleoside Analogs, Inhibit the Production of Extracellular Pregenomic RNA and Spliced RNA Variants

The hepatitis B virus (HBV) core protein serves multiple essential functions in the viral life cycle, and antiviral agents that target the core protein are being developed. Capsid assembly modulators (CAMs) are compounds that target core and misdirect capsid assembly, resulting in the suppression of HBV replication and virion production. Besides HBV DNA, circulating HBV RNA has been detected in patient serum and can be associated with the treatment response. Here we studied the effect of HBV CAMs on the production of extracellular HBV RNA using infected HepaRG cells and primary human hepatocytes. Representative compounds from the sulfonamide carboxamide and heteroaryldihydropyrimidine series of CAMs were evaluated and compared to nucleos(t)ide analogs as inhibitors of the viral polymerase. The results showed that CAMs blocked extracellular HBV RNA with efficiencies similar to those with which they blocked pregenomic RNA (pgRNA) encapsidation, HBV DNA replication, and Dane particle production. Nucleos(t)ide analogs inhibited viral replication and virion production but not encapsidation or production of extracellular HBV RNA. Profiling of HBV RNA from both culture supernatants and patient serum showed that extracellular viral RNA consisted of pgRNA and spliced pgRNA variants with an internal deletion(s) but still retained the sequences at both the 5′ and 3′ ends. Similar variants were detected in the supernatants of infected cells with and without nucleos(t)ide analog treatment. Overall, our data demonstrate that HBV CAMs represent direct antiviral agents with a profile differentiated from that of nucleos(t)ide analogs, including the inhibition of extracellular pgRNA and spliced pgRNA.

Suppression of HBV replication by the expression of nickase- and nuclease dead-Cas9

Complete removal of hepatitis B virus (HBV) DNA from nuclei is difficult by the current therapies. Recent reports have shown that a novel genome-editing tool using Cas9 with a single-guide RNA (sgRNA) system can cleave the HBV genome in vitro and in vivo. However, induction of a double-strand break (DSB) on the targeted genome by Cas9 risks undesirable off-target cleavage on the host genome. Nickase-Cas9 cleaves a single strand of DNA, and thereby two sgRNAs are required for inducing DSBs. To avoid Cas9-induced off-target mutagenesis, we examined the effects of the expressions of nickase-Cas9 and nuclease dead Cas9 (d-Cas9) with sgRNAs on HBV replication. The expression of nickase-Cas9 with a pair of sgRNAs cleaved the target HBV genome and suppressed the viral-protein expression and HBV replication in vitro. Moreover, nickase-Cas9 with the sgRNA pair cleaved the targeted HBV genome in mouse liver. Interestingly, d-Cas9 expression with the sgRNAs also suppressed HBV replication in vitro without cleaving the HBV genome. These results suggest the possible use of nickase-Cas9 and d-Cas9 with a pair of sgRNAs for eliminating HBV DNA from the livers of chronic hepatitis B patients with low risk of undesirable off-target mutation on the host genome.

Hepatitis B Virus Activates Signal Transducer and Activator of Transcription 3 Supporting Hepatocyte Survival and Virus Replication

BACKGROUND & AIMS

The human hepatitis B virus (HBV) is a major cause of chronic hepatitis and hepatocellular carcinoma, but molecular mechanisms driving liver disease and carcinogenesis are largely unknown. We therefore studied cellular pathways altered by HBV infection.

METHODS

We performed gene expression profiling of primary human hepatocytes infected with HBV and proved the results in HBV-replicating cell lines and human liver tissue using real-time polymerase chain reaction and Western blotting. Activation of signal transducer and activator of transcription (STAT3) was examined in HBV-replicating human hepatocytes, HBV-replicating mice, and liver tissue from HBV-infected individuals using Western blotting, STAT3-luciferase reporter assay, and immunohistochemistry. The consequences of STAT3 activation on HBV infection and cell survival were studied by chemical inhibition of STAT3 phosphorylation and small interfering RNA-mediated knockdown of STAT3.

RESULTS

Gene expression profiling of HBV-infected primary human hepatocytes detected no interferon response, while genes encoding for acute phase and antiapoptotic proteins were up-regulated. This gene regulation was confirmed in liver tissue samples of patients with chronic HBV infection and in HBV-related hepatocellular carcinoma. Pathway analysis revealed activation of STAT3 to be the major regulator. Interleukin-6-dependent and -independent activation of STAT3 was detected in HBV-replicating hepatocytes in cell culture and in vivo. Prevention of STAT3 activation by inhibition of Janus tyrosine kinases as well as small interfering RNA-mediated knockdown of STAT3-induced apoptosis and reduced HBV replication and gene expression.

CONCLUSIONS

HBV activates STAT3 signaling in hepatocytes to foster its own replication but also to prevent apoptosis of infected cells. This very likely supports HBV-related carcinogenesis.

Expanding the Antiviral Spectrum of 3-Fluoro-2-(phosphonomethoxy)propyl Acyclic Nucleoside Phosphonates: Diamyl Aspartate Amidate Prodrugs

Acyclic nucleosides containing a 3-fluoro-2-(phosphonomethoxy)propyl (FPMP) side chain are known to be moderately potent antihuman immunodeficiency virus (HIV) agents, while being completely devoid of antiviral activity against a wide range of DNA viruses. The derivatization of the phosphonic acid functionality of FPMPs with a diamyl aspartate phenoxyamidate group led to a novel generation of compounds that not only demonstrate drastically improved antiretroviral potency but also are characterized by an expanded spectrum of activity that also covers hepatitis B and herpes viruses. The best compound, the (S)-FPMPA amidate prodrug, exerts anti-HIV-1 activity in TZM-bl and peripheral blood mononuclear cells at low nanomolar concentrations and displays excellent potency against hepatitis B virus (HBV) and varicella-zoster virus (VZV). This prodrug is stable in acid and human plasma media, but it is efficiently processed in human liver microsomes with a half-life of 2 min. The (R) isomeric guanine derivative emerged as a selectively active anti-HIV and anti-HBV inhibitor, while being nontoxic to human hepatoblastoma cells. Notably, the pyrimidine containing prodrug (S)-Asp-FPMPC is the only congener within this series to demonstrate micromolar antihuman cytomegalovirus (HCMV) potency.

Inhibition of hepatitis B viral entry by nucleic acid polymers in HepaRG cells and primary human hepatocytes

Hepatitis B virus (HBV) infection remains a major public health concern worldwide with 240 million individuals chronically infected and at risk of developing cirrhosis and hepatocellular carcinoma. Current treatments rarely cure chronic hepatitis B infection, highlighting the need for new anti-HBV drugs. Nucleic acid polymers (NAPs) are phosphorothioated oligonucleotides that have demonstrated a great potential to inhibit infection with several viruses. In chronically infected human patients, NAPs administration lead to a decline of blood HBsAg and HBV DNA and to HBsAg seroconversion, the expected signs of functional cure. NAPs have also been shown to prevent infection of duck hepatocytes with the Avihepadnavirus duck hepatitis B virus (DHBV) and to exert an antiviral activity against established DHBV infection in vitro and in vivo.

In this study, we investigated the specific anti-HBV antiviral activity of NAPs in the HepaRG human hepatoma cell line and primary cultures of human hepatocytes. NAPs with different chemical features (phosphorothioation, 2’O-methyl ribose, 5-methylcytidine) were assessed for antiviral activity when provided at the time of HBV inoculation or post-inoculation. NAPs dose-dependently inhibited HBV entry in a phosphorothioation-dependent, sequence-independent and size-dependent manner. This inhibition of HBV entry by NAPs was impaired by 2’O-methyl ribose modification. NAP treatment after viral inoculation did not elicit any antiviral activity.

Glycyrrhetic acid, but not glycyrrhizic acid, strengthened entecavir activity by promoting its subcellular distribution in the liver via efflux inhibition

Entecavir (ETV) is a superior nucleoside analogue used to treat hepatitis B virus (HBV) infection. Although its advantages over other agents include low viral resistance and the elicitation of a sharp decrease in HBV DNA, adverse effects such as hepatic steatosis, hepatic damage and lactic acidosis have also been reported. Glycyrrhizin has long been used as hepato-protective medicine. The clinical combination of ETV plus glycyrrhizin in China displays better therapeutic effects and lower rates of liver damage. However, there is little evidence explaining the probable synergistic mechanism that exists between these two drugs from a pharmacokinetics view. Here, alterations in the plasma pharmacokinetics, tissue distribution, subcellular distribution, and in vitro and in vivo antiviral activity of ETV after combination with glycyrrhizic acid (GL) were analysed to determine the synergistic mechanisms of these two drugs. Specific efflux transporter membrane vesicles were also used to elucidate their interactions. The primary active GL metabolite, glycyrrhetic acid (GA), did not affect the plasma pharmacokinetics of ETV but promoted its accumulation in hepatocytes, increasing its distribution in the cytoplasm and nucleus and augmenting the antiviral efficiency of ETV. These synergistic actions were primarily due to the inhibitory effect of GA on MRP4 and BCRP, which transport ETV out of hepatocytes. In conclusion, GA interacted with ETV at cellular and subcellular levels in the liver through MRP4 and BCRP inhibition, which enhanced the antiviral activity of ETV. Our results partially explain the synergistic mechanism of ETV and GL from a pharmacokinetics view, providing more data to support the use of these compounds together in clinical HBV treatment.

A novel entecavir analogue constructing with a spiro[2.4]heptane core structure in the aglycon moiety: Its synthesis and evaluation for anti-hepatitis B virus activity

Synthesis of a novel 2'-deoxy-guanine carbocyclic nucleoside 4 constructed with spiro[2.4]heptane core structure in the aglycon moiety was carried out. Radical-mediated 5-exo-dig mode cyclization and following cyclopropanation proceeded efficiently to furnish the spiro alcohol 10. Subsequent Mitsunobu-type glycosylation between 13 and 14, deoxygenation of the 2'-hydroxyl group of 16 and deprotection of 17 gave the title compound 4. Compound 4 demonstrated moderate anti-HBV activity (EC₅₀ value of 0.12 ± 0.02 µM) and no cytotoxicity against HepG2 cells was observed up to 100 µM.

Biological effects of bone marrow mesenchymal stem cells on hepatitis B virus in vitro

The aim of the present study was to explore the effects of co‑culturing bone marrow‑derived mesenchymal stem cells (BM-MSCs) cultured with hepatitis B virus (HBV)‑infected lymphocytes in vitro. BM‑MSCs and lymphocytes from Brown Norway rats were obtained from the bone marrow and spleen, respectively. Rats were divided into the following five experimental groups: Group 1, splenic lymphocytes (SLCs); group 2, HepG2.2.15 cells; group 3, BM‑MSCs + HepG2.2.15 cells; group 4, SLCs + HepG2.2.15 cells; and group 5, SLCs + BM‑MSCs + HepG2.2.15 cells. The viability of lymphocytes and HepG2.2.15 cells was assessed using the MTT assay at 24, 48 and 72 h, respectively. Levels of supernatant HBV DNA and intracellular HBV covalently closed circular DNA (cccDNA) were measured using quantitative polymerase chain reaction. Supernatant cytokine levels were measured by enzyme‑linked immunosorbent assay (ELISA). T cell subsets were quantified by flow cytometry using fluorescence‑labeled antibodies. In addition, the HBV genome sequence was analyzed by direct gene sequencing. Levels of HBV DNA and cccDNA in group 5 were lower when compared with those in group 3 or group 4, with a significant difference observed at 48 h. The secretion of interferon‑γ was negatively correlated with the level of HBV DNA, whereas secretion of interleukin (IL)‑10 and IL‑22 were positively correlated with the level of HBV DNA. Flow cytometry demonstrated that the percentage of CD3+CD8+ T cells was positively correlated with the levels of HBV DNA, and the CD3+CD4+/CD3+CD8+ ratio was negatively correlated with the level of HBV DNA. Almost no mutations in the HBV DNA sequence were detected in HepG2.2.15 cells co‑cultured with BM‑MSCs, SLCs, or in the two types of cells combined. BM‑MSCs inhibited the expression of HBV DNA and enhanced the clearance of HBV, which may have been mediated by the regulation of the Tc1/Tc2 cell balance and the mode of cytokine secretion to modulate cytokine expression.

Interplay between the Hepatitis B Virus and Innate Immunity: From an Understanding to the Development of Therapeutic Concepts

The hepatitis B virus (HBV) infects hepatocytes, which are the main cell type composing a human liver. However, the liver is enriched with immune cells, particularly innate cells (e.g., myeloid cells, natural killer and natural killer T-cells (NK/NKT), dendritic cells (DCs)), in resting condition. Hence, the study of the interaction between HBV and innate immune cells is instrumental to: (1) better understand the conditions of establishment and maintenance of HBV infections in this secondary lymphoid organ; (2) define the role of these innate immune cells in treatment failure and pathogenesis; and (3) design novel immune-therapeutic concepts based on the activation/restoration of innate cell functions and/or innate effectors. This review will summarize and discuss the current knowledge we have on this interplay between HBV and liver innate immunity.

Past, Current, and Future Developments of Therapeutic Agents for Treatment of Chronic Hepatitis B Virus Infection

For decades, treatment of hepatitis B virus (HBV) infection has been relying on interferon (IFN)-based therapies and nucleoside/nucleotide analogues (NAs) that selectively target the viral polymerase reverse transcriptase (RT) domain and thereby disrupt HBV viral DNA synthesis. We have summarized here the key steps in the HBV viral life cycle, which could potentially be targeted by novel anti-HBV therapeutics. A wide range of next-generation direct antiviral agents (DAAs) with distinct mechanisms of actions are discussed, including entry inhibitors, transcription inhibitors, nucleoside/nucleotide analogues, inhibitors of viral ribonuclease H (RNase H), modulators of viral capsid assembly, inhibitors of HBV surface antigen (HBsAg) secretion, RNA interference (RNAi) gene silencers, antisense oligonucleotides (ASOs), and natural products. Compounds that exert their antiviral activities mainly through host factors and immunomodulation, such as host targeting agents (HTAs), programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) inhibitors, and Toll-like receptor (TLR) agonists, are also discussed. In this Perspective, we hope to provide an overview, albeit by no means being comprehensive, for the recent development of novel therapeutic agents for the treatment of chronic HBV infection, which not only are able to sustainably suppress viral DNA but also aim to achieve functional cure warranted by HBsAg loss and ultimately lead to virus eradication and cure of hepatitis B.

Hepatitis B Virus Immunopathology, Model Systems, and Current Therapies

Most people develop acute hepatitis B virus (HBV)-related hepatitis that is controlled by both humoral and cellular immune responses following acute infection. However, a number of individuals in HBV-endemic areas fail to resolve the infection and consequently become chronic carriers. While a vaccine is available and new antiviral drugs are being developed, elimination of persistently infected cells is still a major issue. Standard treatment in HBV infection includes IFN-α, nucleoside, or nucleotide analogs, which has direct antiviral activity and immune modulatory capacities. However, immunological control of the virus is often not durable. A robust T-cell response is associated with control of HBV infection and liver damage; however, HBV-specific T cells are deleted, dysfunctional, or become exhausted in chronic hepatitis patients. As a result, efforts to restore virus-specific T-cell immunity in chronic HBV patients using antiviral therapy, immunomodulatory cytokines, or therapeutic vaccination have had little success. Adoptive cell transfer of T cells with specificity for HBV antigen⁺ cells represents an approach aiming to ultimately eliminate residual hepatocytes carrying HBV covalently closed circular DNA (cccDNA). Here, we discuss recent findings describing HBV immunopathology, model systems, and current therapies.

Discovery and Pre-Clinical Characterization of Third-Generation 4-H Heteroaryldihydropyrimidine (HAP) Analogues as Hepatitis B Virus (HBV) Capsid Inhibitors

Described herein are the discovery and structure-activity relationship (SAR) studies of the third-generation 4-H heteroaryldihydropyrimidines (4-H HAPs) featuring the introduction of a C6 carboxyl group as novel HBV capsid inhibitors. This new series of 4-H HAPs showed improved anti-HBV activity and better drug-like properties compared to the first- and second-generation 4-H HAPs. X-ray crystallographic study of analogue 12 (HAP_R01) with Cp149 Y132A mutant hexamer clearly elucidated the role of C6 carboxyl group played for the increased binding affinity, which formed strong hydrogen bonding interactions with capsid protein and coordinated waters. The representative analogue 10 (HAP_R10) was extensively characterized in vitro (ADMET) and in vivo (mouse PK and PD) and subsequently selected for further development as oral anti-HBV infection agent.

Interferon induces interleukin 8 and bone marrow stromal cell antigen 2 expression, inhibiting the production of hepatitis B virus surface antigen from human hepatocytes

Hepatitis B virus (HBV) surface antigen (HBsAg) loss is one of the treatment goals of chronic HBV infection. Bone marrow stromal cell antigen 2 (BST2) is one of the interferon (IFN)-stimulated genes (ISGs) and inhibits the release of various enveloped viruses. Here we examined the effects of antiviral treatment on HBsAg levels and its intracellular mechanism in HBsAg-producing hepatocytes. In PLC/PRF/5 and Huh1, IFNα-2a treatment decreased HBsAg levels in their conditioned media. Upregulation of interleukin 8 (IL8), toll-like receptor 2 (TLR2) and interferon gamma-induced protein 10 (IP10) mRNAs was associated with the reduction of HBsAg in both PLC/PRF/5 and Huh1. The HBsAg level was upregulated by knockdown of IL8, TLR2 or IP10. Exogenous addition of IL8 enhanced BST2 promoter activity and BST2 mRNA expression. Additionally, knockdown of IL8 could lead to the downregulation of BST2 mRNA. Transfection of poly(I-C) enhanced IL8 and BST2 mRNA expression and inhibited HBsAg secretion from PLC/PRF/5 cells. In conclusion, IL8 might play an important role in the enhancement of BST2 and be involved in HBsAg eradication.

Removal of Integrated Hepatitis B Virus DNA Using CRISPR-Cas9

The presence of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) and the permanent integration of HBV DNA into the host genome confers the risk of viral reactivation and hepatocellular carcinoma. Nucleoside/nucleotide analogs alone have little or no capacity to eliminate replicative HBV templates consisting of cccDNA or integrated HBV DNA. Recently, CRISPR/Cas9 technology has been widely applied as a promising genome-editing tool, and HBV-specific CRISPR-Cas9 systems were shown to effectively mediate HBV cccDNA disruption. However, the integrated HBV DNA fragments are considered as important pro-oncogenic properties and it serves as an important template for viral replication and expression in stable HBV cell line. In this study, we completely excised a full-length 3,175-bp integrated HBV DNA fragment and disrupted HBV cccDNA in a stable HBV cell line. In HBV-excised cell line, the HBV cccDNA inside cells, supernatant HBV DNA, HBsAg, and HBeAg remained below the negative critical values for more than 10 months. Besides, by whole genome sequencing, we analyzed off-target effects and excluded cell contamination. It is the first time that the HBV infection has been fully eradicated in a stable HBV cell line. These findings demonstrate that the CRISPR-Cas9 system is a potentially powerful tool capable of promoting a radical or “sterile” HBV cure.

Frequency and role of NKp46 and NKG2A in hepatitis B virus infection

Background and Aim

Natural Killer (NK) cells are involved in the control of viral infection. However, the role of NK cells in chronic hepatitis B (CHB) remains unclear. This study investigated the frequencies and roles of NK cells in CHB, with a focus on activating receptor NKp46 and inhibitory receptor NKG2A.

Patients/Method

Peripheral blood lymphocytes were obtained from 71 CHB patients and 37 healthy subjects (HS). The expressions of NKp46 and NKG2A were analyzed using flow cytometry. The role of NKp46-ligand was assessed using an in vitro co-culture system. Cytotoxicity and IFN-γ production in NK cells were evaluated using RT-PCR and flow cytometry.

Results

CHB patients were classified into treatment-naïve patients with low HBV DNA titer (CHB-L; n = 28), high HBV DNA titer (CHB-H; n = 24) by the cut-off level of serum HBV DNA 4 log copies/ml, and patients receiving nucleos(t)ide analogue (CHB-NA; n = 19). The expressions of NKp46 and NKG2A were higher in CHB-H than in HS/CHB-L/CHB-NA. HepG2.2.15 had higher NKp46-ligand expression than HepG2. When NK cells from HS were co-cultured with HepG2.2.15, inhibition of the NKp46 and NKp46-ligand interaction by anti-NKp46 antibody significantly reduced cytolysis of HepG2.2.15 and IFN-γ production. However, those reductions were not observed in co-culture with HepG2. Additionally, NK cells that highly expressed NKp46 also highly expressed NKG2A (NKp46^highNKG2A^high subset). The frequencies of NKp46^highNKG2A^high subset in CHB-H were higher than those in HS/CHB-L/CHB-NA. Among treatment-naïve CHB patients, the frequencies of NKp46^highNKG2A^high subset were positively correlated with serum ALT (P<0.01, r = 0.45) and HBV DNA (P<0.01, r = 0.59) levels. The expressions of Fas-L, STAT1, TRAIL and CD107a were higher and IFN-γ expression was lower in the NKp46^highNKG2A^high subset than in the other subsets.

Conclusion

The NKp46 and NKp46-ligand interaction contributes to NK cell activation. A novel NK cell subset, the NKp46^highNKG2A^high subset, may be associated with liver injury and HBV replication.

Human stem cell-derived hepatocytes as a model for hepatitis B virus infection, spreading and virus-host interactions

BACKGROUND & AIMS

One major obstacle of hepatitis B virus (HBV) research is the lack of efficient cell culture system permissive for viral infection and replication. The aim of our study was to establish a robust HBV infection model by using hepatocyte-like cells (HLCs) derived from human pluripotent stem cells.

METHODS

HLCs were differentiated from human embryonic stem cells and induced pluripotent stem cells. Maturation of hepatocyte functions was determined. After HBV infection, total viral DNA, cccDNA, total viral RNA, pgRNA, HBeAg and HBsAg were measured.

RESULTS

More than 90% of the HLCs expressed strong signals of human hepatocyte markers, like albumin, as well as known host factors required for HBV infection, suggesting that these cells possessed key features of mature hepatocytes. Notably, HLCs expressed the viral receptor sodium-taurocholate cotransporting polypeptide more stably than primary human hepatocytes (PHHs). HLCs supported robust infection and some spreading of HBV. Finally, by using this model, we identified two host-targeting agents, genistin and PA452, as novel antivirals.

CONCLUSIONS

Stem cell-derived HLCs fully support HBV infection. This novel HLC HBV infection model offers a unique opportunity to advance our understanding of the molecular details of the HBV life cycle; to further characterize virus-host interactions and to define new targets for HBV curative treatment.

LAY SUMMARY

Our study used human pluripotent stem cells to develop hepatocyte-like cells (HLCs) capable of expressing hepatocyte markers and host factors important for HBV infection. These cells fully support HBV infection and virus-host interactions, allowing for the identification of two novel antiviral agents. Thus, stem cell-derived HLCs provide a highly physiologically relevant system to advance our understanding of viral life cycle and provide a new tool for antiviral drug screening and development.

Efficient genome replication of hepatitis B virus using adenovirus vector: a compact pregenomic RNA-expression unit

The complicated replication mechanisms of hepatitis B virus (HBV) have impeded HBV studies and anti-HBV therapy development as well. Herein we report efficient genome replication of HBV applying adenovirus vectors (AdVs) showing high transduction efficiency. Even in primary hepatocytes derived from humanized mice the transduction efficiencies using AdVs were 450-fold higher compared than those using plasmids. By using an expression unit consisting of the CMV promoter, 1.03-copy HBV genome and foreign poly(A) signal, we successfully generated an improved AdV (HBV103-AdV) that efficiently provided 58 times more pregenomic RNA than previously reported AdVs. The HBV103-AdV-mediated HBV replication was easily and precisely detected using quantitative real-time PCR in primary hepatocytes as well as in HepG2 cells. Notably, when the AdV containing replication-defective HBV genome of 1.14 copy was transduced, we observed that HBV DNA-containing circular molecules (pseudo-ccc DNA) were produced, which were probably generated through homologous recombination. However, the replication-defective HBV103-AdV hardly yielded the pseudo-ccc, probably because the repeated sequences are vey short. Additionally, the efficacies of entecavir and lamivudine were quantitatively evaluated using this system at only 4 days postinfection with HBV103-AdVs. Therefore, this system offers high production of HBV genome replication and thus could become used widely.

Permissive, in vitro replication of hepatitis B virus genotype E

A cloned stable cell line, HepG2-HBVE6, was established following transfection of HepG2 cells with a retroviral plasmid into which a 1.1-fold genomic construct of hepatitis B virus (HBV) belonging to genotype E (HBV/E) was inserted. The cell line retains the entire HBV/E insert, and produces episomal HBV DNA. It expresses HBV pregenomic, preS1 and preS2/S transcripts, and sheds hepatitis B surface and e antigens as well as structures resembling HBV-subviral and Dane particles. The HepG2-HBVE6 cell line, in permitting recapitulation of the HBV life cycle, may be used for studying viral characteristics, therapeutic and preventative outcomes and for preparing reagents specific to HBV genotype E.

Human Liver Sinusoid on a Chip for Hepatitis B Virus Replication Study

We have developed a miniature human liver (liver-sinusoid-on-a-chip) model using a dual microchannel separated by a porous membrane. Primary human hepatocytes and immortalized bovine aortic endothelial cells were co-cultured on opposite sides of a microporous membrane in a dual microchannel with continuous perfusion. Primary human hepatocytes in this system retained their polygonal morphology for up to 26 days, while hepatocytes cultured in the absence of bovine aortic endothelial cells lost their morphology within a week. In order to demonstrate the utility of our human-liver-sinusoid-on-a-chip, human hepatocytes in this system were directly infected by Hepatitis B Virus (HBV). Expression of the HBV core antigen was detected in human hepatocytes in the microchannel system. HBV replication, measured by the presence of cell-secreted HBV DNA, was also detected. Importantly, HBV is hepatotropic, and expression of HBV RNA transcripts is dependent upon expression of hepatocyte-specific factors. Moreover, HBV infection requires expression of the human-hepatocyte-specific HBV cell surface receptor. Therefore, the ability to detect HBV replication and Hepatitis B core Antigen (HBcAg) expression in our microfluidic platform confirmed that hepatocyte differentiation and functions were retained throughout the time course of our studies. We believe that our human-liver-sinusoid-on-a-chip could have many applications in liver-related research and drug development.

NTCP-Reconstituted In Vitro HBV Infection System

Sodium taurocholate cotransporting polypeptide (NTCP) has been identified as a functional receptor for hepatitis B virus (HBV). Expressing human NTCP in human hepatoma HepG2 cells (HepG2-NTCP) renders these cells susceptible for HBV infection. The HepG2-NTCP stably transfected cell line provides a much-needed and easily accessible platform for studying the virus. HepG2-NTCP cells could also be used to identify chemicals targeting key steps of the virus life cycle including HBV covalent closed circular (ccc) DNA, and enable the development of novel antivirals against the infection.Many factors may contribute to the efficiency of HBV infection on HepG2-NTCP cells, with clonal differences among cell line isolates, the source of viral inoculum, and infection medium among the most critical ones. Here, we provide detailed protocols for efficient HBV infection of HepG2-NTCP cells in culture; generation and selection of single cell clones of HepG2-NTCP; production of infectious HBV virion stock through DNA transfection of recombinant plasmid that enables studying primary clinical HBV isolates; and assessing the infection with immunostaining of HBV antigens and Southern blot analysis of HBV cccDNA.

Recapitulation of treatment response patterns in a novel humanized mouse model for chronic hepatitis B virus infection

There are ~350 million chronic carriers of hepatitis B (HBV). While a prophylactic vaccine and drug regimens to suppress viremia are available, chronic HBV infection is rarely cured. HBV's limited host tropism leads to a scarcity of susceptible small animal models and is a hurdle to developing curative therapies. Mice that support engraftment with human hepatoctyes have traditionally been generated through crosses of murine liver injury models to immunodeficient backgrounds. Here, we describe the disruption of fumarylacetoacetate hydrolase directly in the NOD Rag1^-/- IL2RγNULL (NRG) background using zinc finger nucleases. The resultant human liver chimeric mice sustain persistent HBV viremia for >90 days. When treated with standard of care therapy, HBV DNA levels decrease below detection but rebound when drug suppression is released, mimicking treatment response observed in patients. Our study highlights the utility of directed gene targeting approaches in zygotes to create new humanized mouse models for human diseases.

In vitro antiviral activity of three enantiomeric sesquiterpene lactones from Senecio species against hepatitis B virus

Three enantiomeric sesquiterpene lactones were isolated under the bioguidance of the suppression of hepatitis B virus (HBV) surface antigen (HBsAg) from Senecio species, a widely distributed Chinese medicinal herb traditionally used for the treatment of hepatitis B, dermatosis and inflammation. The anti-HBV activity of the purified compounds was measured; all of them showed suppressive activity on the expression of HBsAg and HBV e antigen (HBeAg) in the HepG2.2.15 cell line. Realtime quantitative PCR analysis showed that the studied compounds decreased the number of infectious virions released, but did not inhibit the intracellular HBV DNA. The results suggest that enantiomeric sesquiterpene lactones may possess the potential to work synergistically with other antiviral compounds for the treatment of HBV infection.

Pseudolaric acid B inhibits the secretion of hepatitis B virus

High hepatitis B virus (HBV) load and chronic hepatitis B infection increase the risk of developing hepatocellular carcinoma (HCC), and is also associated with recurrence of HBV-related HCC. The aim of the present study was to investigate whether pseudolaric acid B (PAB), a diterpene acid isolated from the root and trunk bark of Pseudolarix kaempferi Gordon (Pinaceae), has an inhibitory role on the HBV secretion in HBV-related HCC. By detecting HBV surface antigen (HBsAg) by ELISA it was found that PAB inhibited HBV secretion in HepG2215 compared to control group, but did not decrease the intracellular HBV level, and the results were repeated in HepG2 cell transfect with HBV gene. Therefore, our results proved that PAB had the ability to inhibit HBV secretion. Moreover, it was shown that HepG2215 cells with HBV gene accumulated more in G0/G1 phase than HepG2 cells without HBV gene through detecting cell cycle distribution by flow cytometry, which indicated that HBV replication might favor the cell cycle environment of G0/G1 phase. However, HepG2 cells entered G2/M phase earlier than HepG2215 when PAB treatment induced G2/M arrest, therefore, HBV retarded the entry of G2/M to sustain the status of G0/G1 phase, while PAB finally changed the cell cycle environment favored by HBV virus. In addition, PAB also induced HepG2215 cell apoptosis, which would be helpful to kill the cells infected by HBV and help for devouring HBV by macrophage. Therefore, PAB inhibited HBV secretion through apoptosis and cell cycle arrest. The present findings contribute to a future potential chemotherapeutic drug in the treatment of HBV-related HCC.

Hepatitis B virus inhibits insulin receptor signaling and impairs liver regeneration via intracellular retention of the insulin receptor

Hepatitis B virus (HBV) causes severe liver disease but the underlying mechanisms are incompletely understood. During chronic HBV infection, the liver is recurrently injured by immune cells in the quest for viral elimination. To compensate tissue injury, liver regeneration represents a vital process which requires proliferative insulin receptor signaling. This study aims to investigate the impact of HBV on liver regeneration and hepatic insulin receptor signaling. After carbon tetrachloride-induced liver injury, liver regeneration is delayed in HBV transgenic mice. These mice show diminished hepatocyte proliferation and increased expression of fibrosis markers. This is in accordance with a reduced activation of the insulin receptor although HBV induces expression of the insulin receptor via activation of NF-E2-related factor 2. This leads to increased intracellular amounts of insulin receptor in HBV expressing hepatocytes. However, intracellular retention of the receptor simultaneously reduces the amount of functional insulin receptors on the cell surface and thereby attenuates insulin binding in vitro and in vivo. Intracellular retention of the insulin receptor is caused by elevated amounts of α-taxilin, a free syntaxin binding protein, in HBV expressing hepatocytes preventing proper targeting of the insulin receptor to the cell surface. Consequently, functional analyses of insulin responsiveness revealed that HBV expressing hepatocytes are less sensitive to insulin stimulation leading to delayed liver regeneration. This study describes a novel pathomechanism that uncouples HBV expressing hepatocytes from proliferative signals and thereby impedes compensatory liver regeneration after liver injury.

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.