Increased GABA signaling in liver macrophage promotes HBV replication in HBV-carrier mice

Gamma-aminobutyric acid (GABA) signals in various non-neuronal cells including hepatocytes and some immune cells. Studies, including ours, show that type A GABA receptors (GABAARs)-mediated signaling occurs in macrophages regulating tissue-specific functions. Our recent study reveals that activation of GABAARs in liver macrophages promotes their M2-like polarization and increases HBV replication in mice. This short article briefly summarizes the GABA signaling system in macrophages and discusses potential mechanisms by which GABA signaling promotes HBV replication.

A mutual regulatory loop between transcription factor Yin Yang 1 and hepatitis B virus replication influences chronic hepatitis B

Hepatitis B virus (HBV) infections pose a major threat to human health. HBV can upregulate the expression of the transcription factor Yin Yang 1 (YY1) in in vitro cytological experiments, suggesting an association between YY1 and HBV infection. However, data on YY1 expression in chronic hepatitis B (CHB) patients are lacking. In this study, we aimed to assess the correlation between YY1 expression and HBV infection. We detected serum YY1 levels in 420 patients with chronic HBV infection, 30 patients with chronic hepatitis C virus infection, and 32 healthy controls using an enzyme-linked immunosorbent assay. The correlation between YY1 levels and clinical parameters was analyzed. Meanwhile, the changes of YY1 before and after interferon or entecavir treatment were analyzed. YY1 levels in the liver tissues were detected using immunofluorescence staining. The expression of YY1 in HBV-expressing cells was detected through western blotting. Meanwhile, we explored the effects of YY1 on HBV replication and gene expression. We found that YY1 was highly expressed in the serum and liver tissues of CHB patients. Serum YY1 levels positively correlated with HBV DNA and hepatitis B surface antigen (HBsAg). Additionally, HBV DNA levels increased but HBsAg levels decreased after HBV-expressing cells overexpress YY1. In conclusion, our study demonstrates that YY1 plays an important role in HBV replication and gene expression, providing a potential target for the treatment of CHB.

HBV PreC interacts with SUV39H1 to induce viral replication by blocking the proteasomal degradation of viral polymerase

Hepatitis B e antigen (HBeAg) seropositivity during the natural history of chronic hepatitis B (CHB) is known to coincide with significant increases in serum and intrahepatic HBV DNA levels. However, the precise underlying mechanism remains unclear. In this study, we found that PreC (HBeAg precursor) genetic ablation leads to reduced viral replication both in vitro and in vivo. Furthermore, PreC impedes the proteasomal degradation of HBV polymerase, promoting viral replication. We discovered that PreC interacts with SUV39H1, a histone methyltransferase, resulting in a reduction in the expression of Cdt2, an adaptor protein of CRL4 E3 ligase targeting HBV polymerase. SUV39H1 induces H3K9 trimethylation of the Cdt2 promoter in a PreC-induced manner. CRISPR-mediated knockout of endogenous SUV39H1 or pharmaceutical inhibition of SUV39H1 decreases HBV loads in the mouse liver. Additionally, genetic depletion of Cdt2 in the mouse liver abrogates PreC-related HBV replication. Interestingly, a negative correlation of intrahepatic Cdt2 with serum HBeAg and HBV DNA load was observed in CHB patient samples. Our study thus sheds light on the mechanistic role of PreC in inducing HBV replication and identifies potential therapeutic targets for HBV treatment.

Furanocoumarins promote proteasomal degradation of viral HBx protein and down-regulate cccDNA transcription and replication of hepatitis B virus

Nucleot(s)ide analogues, the current antiviral treatments against chronic hepatitis B (CHB) infection, are non-curative due to their inability to eliminate covalently closed circular DNA (cccDNA) from the infected hepatocytes. Preclinical studies have shown that coumarin derivatives can effectively reduce the HBV DNA replication. We evaluated the antiviral efficacy of thirty new coumarin derivatives in cell culture models for studying HBV. Furanocoumarins Fc-20 and Fc-31 suppressed the levels of pre-genomic RNA as well as cccDNA, and reduced the secretion of virions, HBsAg and HBeAg. The antiviral efficacies of Fc-20 and Fc31 improved further when used in combination with the hepatitis B antiviral drug Entecavir. There was a marked reduction in the intracellular HBx level in the presence of these furanocoumarins due to proteasomal degradation resulting in the down-regulation of HBx-dependent viral genes. Importantly, both Fc-20 and Fc-31 were non-cytotoxic to cells even at high concentrations. Further, our molecular docking studies confirmed a moderate to high affinity interaction between furanocoumarins and viral HBx via residues Ala3, Arg26 and Lys140. These data suggest that furanocoumarins could be developed as a new therapeutic for CHB infection.

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

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

JMJD2D stabilises and cooperates with HBx protein to promote HBV transcription and replication

Background & Aims

HBV infection is a global health burden. Covalently closed circular DNA (cccDNA) transcriptional regulation is a major cause of poor cure rates of chronic hepatitis B (CHB) infection. Herein, we evaluated whether targeting host factors to achieve functional silencing of cccDNA may represent a novel strategy for the treatment of HBV infection.

Methods

To evaluate the effects of Jumonji C domain-containing (JMJD2) protein subfamily JMJD2A-2D proteins on HBV replication, we used lentivirus-based RNA interference to suppress the expression of isoforms JMJD2A-2D in HBV-infected cells. JMJD2D-knockout mice were generated to obtain an HBV-injected model for in vivo experiments. Co-immunoprecipitation and ubiquitylation assays were used to detect JMJD2D-HBx interactions and HBx stability modulated by JMJD2D. Chromatin immunoprecipitation assays were performed to investigate JMJD2D-cccDNA and HBx-cccDNA interactions.

Results

Among the JMJD2 family members, JMJD2D was significantly upregulated in mouse livers and human hepatoma cells. Downregulation of JMJD2D inhibited cccDNA transcription and HBV replication. Molecularly, JMJD2D sustained HBx stability by suppressing the TRIM14-mediated ubiquitin-proteasome degradation pathway and acted as a key co-activator of HBx to augment HBV replication. The JMJD2D-targeting inhibitor, 5C-8-HQ, suppressed cccDNA transcription and HBV replication.

Conclusion

Our study clarified the mechanism by which JMJD2D regulates HBV transcription and replication and identified JMJD2D as a potential diagnostic biomarker and promising drug target against CHB, and HBV-associated hepatocarcinoma.

Impact and implications

HBV cccDNA is central to persistent infection and is a major obstacle to healing CHB. In this study, using cellular and animal HBV models, JMJD2D was found to stabilise and cooperate with HBx to augment HBV transcription and replication. This study reveals a potential novel translational target for intervention in the treatment of chronic hepatitis B infection.

The hepatic GABAergic system promotes liver macrophage M2 polarization and mediates HBV replication in mice

Macrophages display functional phenotypic plasticity. Hepatitis B virus (HBV) infection induces polarizations of liver macrophages either to M1-like pro-inflammatory phenotype or to M2-like anti-inflammatory phenotype. Gamma-aminobutyric acid (GABA) signaling exists in various non-neuronal cells including hepatocytes and some immune cells. Here we report that macrophages express functional GABAergic signaling components and activation of type A GABA receptors (GABAARs) promotes M2-polarization thus advancing HBV replication. Notably, intraperitoneal injection of GABA or the GABAAR agonist muscimol increased HBV replication in HBV-carrier mice that were generated by hydrodynamical injection of adeno-associated virus/HBV1.2 plasmids (pAAV/HBV1.2). The GABA-augmented HBV replication in HBV-carrier mice was significantly reduced by the GABAAR inhibitor picrotoxin although picrotoxin had no significant effect on serum HBsAg levels in control HBV-carrier mice. Depletion of liver macrophages by liposomal clodronate treatment also significantly reduced the GABA-augmented HBV replication. Yet adoptive transfer of liver macrophages isolated from GABA-treated donor HBV-carrier mice into the liposomal clodronate-pretreated recipient HBV-carrier mice restored HBV replication. Moreover, GABA or muscimol treatment increased the expression of "M2" cytokines in macrophages, but had no direct effect on HBV replication in the HepG2.2.15 cells, HBV1.3-transfected Huh7, HepG2, or HepaRG cells, or HBV-infected Huh7-NTCP cells. Taken together, these results suggest that increasing GABA signaling in the liver promotes HBV replication in HBV-carrier mice by suppressing the immunity of liver macrophages, but not by increasing the susceptibility of hepatocytes to HBV infection. Our study shows that a previously unknown GABAergic system in liver macrophage has an essential role in HBV replication.

Peptidyl-prolyl cis/trans isomerase Pin1 interacts with hepatitis B virus core particle, but not with HBc protein, to promote HBV replication

Here, we demonstrate that the peptidyl-prolyl cis/trans isomerase Pin1 interacts noncovalently with the hepatitis B virus (HBV) core particle through phosphorylated serine/threonine-proline (pS/TP) motifs in the carboxyl-terminal domain (CTD) but not with particle-defective, dimer-positive mutants of HBc. This suggests that neither dimers nor monomers of HBc are Pin1-binding partners. The ¹⁶²TP, ¹⁶⁴SP, and ¹⁷²SP motifs within the HBc CTD are important for the Pin1/core particle interaction. Although Pin1 dissociated from core particle upon heat treatment, it was detected as an opened-up core particle, demonstrating that Pin1 binds both to the outside and the inside of the core particle. Although the amino-terminal domain S/TP motifs of HBc are not involved in the interaction, ⁴⁹SP contributes to core particle stability, and ¹²⁸TP might be involved in core particle assembly, as shown by the decreased core particle level of S49A mutant through repeated freeze and thaw and low-level assembly of the T128A mutant, respectively. Overexpression of Pin1 increased core particle stability through their interactions, HBV DNA synthesis, and virion secretion without concomitant increases in HBV RNA levels, indicating that Pin1 may be involved in core particle assembly and maturation, thereby promoting the later stages of the HBV life cycle. By contrast, parvulin inhibitors and PIN1 knockdown reduced HBV replication. Since more Pin1 proteins bound to immature core particles than to mature core particles, the interaction appears to depend on the stage of virus replication. Taken together, the data suggest that physical association between Pin1 and phosphorylated core particles may induce structural alterations through isomerization by Pin1, induce dephosphorylation by unidentified host phosphatases, and promote completion of virus life cycle.

PPIases Par14/Par17 Affect HBV Replication in Multiple Ways

Human parvulin 14 (Par14) and parvulin 17 (Par17) are peptidyl-prolyl cis/trans isomerases that upregulate hepatitis B virus (HBV) replication by binding to the conserved ¹³³Arg-Pro¹³⁴ (RP) motif of HBc and core particles, and ¹⁹RP²⁰-²⁸RP²⁹ motifs of HBx. In the absence of HBx, Par14/Par17 have no effect on HBV replication. Interaction with Par14/Par17 enhances the stability of HBx, core particles, and HBc. Par14/Par17 binds outside and inside core particles and is involved in HBc dimer-dimer interaction to facilitate core particle assembly. Although HBc RP motif is important for HBV replication, R133 residue is solely important for its interaction with Par14/Par17. Interaction of Par14 and Par17 with HBx involves two substrate-binding residues, Glu46/Asp74 (E46/D74) and E71/D99, respectively, and promotes HBx translocation to the nucleus and mitochondria. In the presence of HBx, Par14/Par17 are efficiently recruited to cccDNA and promote transcriptional activation via specific DNA-binding residues Ser19/44 (S19/44). S19 and E46/D74 of Par14, and S44 and E71/D99 of Par17, are also involved in the recruitment of HBc onto cccDNA. Par14/Par17 upregulate HBV replication via various effects that are mediated in part through the HBx-Par14/Par17-cccDNA complex and triple HBc, Par14/Par17, and cccDNA interactions in the nucleus, as well as via core particle-Par14/Par17 interactions in the cytoplasm.

Significant metabolic alterations in patients with hepatitis B virus replication observed via serum untargeted metabolomics shed new light on hepatitis B virus infection

Until now, the metabolic effects of hepatitis B virus (HBV) replication on the progression of hepatic diseases (hepatitis, cirrhosis, and liver cancer) and liver functions have remained unexplored. Thus, a total of 199 hepatic disease patients with active and inactive HBV were enrolled in this study to explore serum metabolic characteristics using untargeted metabolomics. Multiple analyses, including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), volcano plot and pathway analysis, were used for metabolic data analysis. Additionally, differential metabolites were analysed by commercial databases. A decrease of approximately 0.8-fold in amino acids (L-glutamic acid, D-glutamine and L-tyrosine) and an increase of 2-fold in phosphatidylcholines (PCs) and lysophosphatidylcholines (LPCs) were observed in hepatic disease patients with HBV replication. Moreover, downregulation of arachidonic acid, PC 34:2, sn-glycerol-3-phosphocholine, 1-palmitoylglycerophosphoinositol, and 1-oleoylglycerophosphoinositol by 0.6-fold was also found in the serum of patients with HBV replication. In addition, liver function was significantly different between cirrhosis patients with or without HBV replication (p < .05). In summary, this is the first study to focus on the metabolic changes induced by HBV replication in patients and to compare metabolic alterations in the progression of hepatic disease induced by HBV infection. High levels of amino acid depletion and PC and LPC biosynthesis were primarily observed, which may shed new light on the pathogenesis and treatment of HBV infection.

Efficient Inhibition of Hepatitis B Virus (HBV) Replication and cccDNA Formation by HBV Ribonuclease H Inhibitors during Infection

The hepatitis B virus (HBV) ribonuclease H (RNase H) is an attractive but unexploited drug target. Here, we addressed three limitations to the current state of RNase H inhibitor development: (a) Efficacy has been assessed only in transfected cell lines. (b) Cytotoxicity data are from transformed cell lines rather than primary cells. (c) It is unknown how the compounds work against nucleos(t)ide analog resistant HBV strains. Three RNase H inhibitors from different chemotypes, 110 (α-hydroxytropolone), 1133 (N-hydroxypyridinedione), and 1073 (N-hydroxynapthyridinone), were tested in HBV-infected HepG2-NTCP cells for inhibition of cccDNA accumulation and HBV product formation. 50% effective concentrations (EC₅₀s) were 0.049-0.078 μM in the infection studies compared to 0.29-1.6 μM in transfected cells. All compounds suppressed cccDNA formation by >98% at 5 μM when added shortly after infection. HBV RNA, intracellular and extracellular DNA, and HBsAg secretion were all robustly suppressed. The greater efficacy of the inhibitors when added shortly after infection is presumably due to blocking amplification of the HBV cccDNA, which suppresses events downstream of cccDNA formation. The compounds had 50% cytotoxic concentrations (CC₅₀s) of 16-100 μM in HepG2-derived cell lines but were nontoxic in primary human hepatocytes, possibly due to the quiescent state of the hepatocytes. The compounds had similar EC₅₀s against replication of wild-type, lamivudine-resistant, and adefovir/lamivudine-resistant HBV, as expected because the RNase H inhibitors do not target the viral reverse transcriptase active site. These studies expand confidence in inhibiting the HBV RNase H as a drug strategy and support inclusion of RNase H inhibitors in novel curative drug combinations for HBV.

Hepatitis B virus evades immune recognition via RNA adenosine deaminase ADAR1-mediated viral RNA editing in hepatocytes

HBV is considered as a "stealth" virus that does not invoke interferon (IFN) responses; however, the mechanisms by which HBV bypasses innate immune recognition are poorly understood. In this study, we identified adenosine deaminases acting on RNA 1 (ADAR1), which is a key factor in HBV evasion from IFN responses in hepatocytes. Mechanically, ADAR1 interacted with HBV RNAs and deaminated adenosine (A) to generate inosine (I), which disrupted host immune recognition and thus promoted HBV replication. Loss of ADAR1 or its deficient deaminase activity promoted IFN responses and inhibited HBV replication in hepatocytes, and blocking the IFN signaling pathways released the inhibition of HBV replication caused by ADAR1 deficiency. Notably, the HBV X protein (HBx) transcriptionally promoted ADAR1 expression to increase the threshold required to trigger intrinsic immune activation, which in turn enhanced HBV escape from immune recognition, leading to persistent infection. Supplementation with 8-azaadenosine, an ADAR1 inhibitor, efficiently enhanced liver immune activation to promote HBV clearance in vivo and in vitro. Taken together, our results delineate a molecular mechanism by which HBx promotes ADAR1-derived HBV immune escape and suggest a targeted therapeutic intervention for HBV infection.

Hepatitis D Virus and Hepatocellular Carcinoma

Hepatitis D virus (HDV) is a small, defective RNA virus that depends on hepatitis B virus (HBV) for virion assembly and transmission. It replicates within the nucleus of hepatocytes and interacts with several cellular proteins. Chronic hepatitis D is a severe and progressive disease, leading to cirrhosis in up to 80% of cases. A high proportion of patients die of liver decompensation or hepatocellular carcinoma (HCC), but the lack of large prospective studies has made it difficult to precisely define the rate of these long-term complications. In particular, the question of whether HDV is an oncogenic virus has been a matter of debate. Studies conducted over the past decade provided evidence that HDV is associated with a significantly higher risk of developing HCC compared to HBV monoinfection. However, the mechanisms whereby HDV promotes liver cancer remain elusive. Recent data have demonstrated that the molecular profile of HCC-HDV is unique and distinct from that of HBV-HCC, with an enrichment of upregulated genes involved in cell-cycle/DNA replication, and DNA damage and repair, which point to genome instability as an important mechanism of HDV hepatocarcinogenesis. These data suggest that HBV and HDV promote carcinogenesis by distinct molecular mechanisms despite the obligatory dependence of HDV on HBV.

A primary human hepatocyte/hepatic stellate cell co-culture system for improved in vitro HBV replication

Primary human hepatocytes (PHHs) are considered the gold standard for the in vitro study of HBV replication as they directly reflect the metabolism and functionality of the human liver. However, several limitations of this system include PHH donor-to-donor variability, limited life span and low permissiveness to HBV infection, which precludes long-term infection studies and viral passaging. Here, an easy-to-set-up co-culture platform that combines PHH with hepatic stellate cells (HSCs) was developed. This platform does not rely on chemical supplementation to sustain robust HBV replication and viral antigen secretion making it a more physiologically relevant system for in vitro HBV infection studies compared to the traditional short-lived PHH monocultures.

NFATc3 inhibits hepatocarcinogenesis and HBV replication via positively regulating RIG-I-mediated interferon transcription

Nuclear factor of activated T cells 3 (NFATc3) has been reported to upregulate type I interferons (IFNs) expression, and the abnormal expression and activation of NFATc3 were closely related to tumorigenesis. However, the potential function of NFATc3 in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) remains to be elucidated. In this study, we found that NFATc3 gene was frequently deleted and downregulated in HCC tumor tissues, and that the downregulation of NFATc3 was associated with poor prognosis of HCC patients. The gain- and loss-of-function experiments demonstrated that NFATc3 inhibited HCC cell proliferation and invasion, as well as HBV replication. Mechanistically, NFATc3 could bind to the promoters of IFNL1 and IFNB1 genes and prompt the production of IFNs and interferon-stimulated genes. Furthermore, retinoic acid-inducible gene-I (RIG-I) pathway activation increased NFATc3 expression and nuclear localization, and activated NFATc3 further enhanced RIG-I-mediated IFN responses. Collectively, our findings reveal a novel regulatory signaling cascade, the RIG-I/NFATc3/IFNs axis, which inhibits hepatocarcinogenesis and HBV replication by enhancing the immune response in hepatocytes, and this functional axis might potentially be exploited for therapeutic benefits in the clinical treatment of HBV-related HCC.

The microRNA-155 mediates hepatitis B virus replication by reinforcing SOCS1 signalling-induced autophagy

As small conserved RNAs without a coding function, microRNAs are expressed in multicellular organisms and contribute to the modulation of multiple cellular reactions, such as viral replication, as well as autophagy. microRNAs can regulate host gene expression and inhibit or reinforce hepatitis B virus (HBV) replication. Hepatic cells express miR-155 noticeably. Consequently, our study explored miR-155 modulation of HBV replication and investigated the potential mechanism involved. miR-155 was inhibited on HBV infection. miR-155 transfection remarkably reinforced HBV replication, antigen expression, and progeny secretion in HepG2215 cells. Moreover, miR-155 impaired the inhibition of the cytokine signalling 1 (SOCS1)/Akt/mTOR axis and reinforced HepG2215 autophagy. Additionally, the autophagy inhibitor (3-MA) eliminated HBsAg secretion triggered by miR-155. Taken together, miR-155 reinforced HBV replication by reinforcing SOCS1-triggered autophagy. SIGNIFICANCE OF THE STUDY: The research studied the potential mechanism involved in HBV replication and miR-155 that miR-155 reinforces HBV replication by reinforcing the SOCS1/Akt/mTOR axis-stimulated autophagy, and therefore, it can provide medical practitioners with the inspiration that chronic HBV might be cured or improved by regulating the activation of miR-155 in cells. In the study, the experiments show that autophagy inhibitors (3-MA) counteracted miR-155 contribution to HBV replication, and it might be a practicable way to improve HBV through some therapies that can repress the autophagy in related cells.

miR-146a-5p enhances hepatitis B virus replication through autophagy to promote aggravation of chronic hepatitis B

The objective of this study was to investigate the mechanism by which miR-146a-5p mediated autophagy and hepatitis B virus (HBV) replication. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the mRNA expression levels of miR-146a-5p and X-linked inhibitor of apoptosis (XIAP) and HBV DNA and RNA. The protein expression levels of XIAP, IκB-α, murine double minute 2 oncoprotein (MDM2) and p53, the phosphorylation of p65, and the conversion of light chain 3 (LC3)-I to LC3-II were detected by Western blotting. The expression levels of XIAP, HBV-related pro-inflammatory cytokines, and serum markers were detected by enzyme-linked immunosorbent assay (ELISA). miR-146a-5p was highly expressed in patients with chronic hepatitis B (CHB) and HBV-expressing hepatocytes. HBV core protein (HBc) and HBV X protein (HBx) were responsible for its effects on miR-146a-5p expression through the nuclear factor-κB pathway. Furthermore, the miR-146a-5p inhibitor suppressed autophagic response and HBV replication as well as MDM2/p53 expression. Luciferase reporter assay confirmed that XIAP was a direct target of miR-146a-5p. We therefore demonstrated that miR-146a-5p mediated positive feedback loop by regulating autophagy-induced HBV replication via targeting the XIAP-mediated MDM2/p53 axis. © 2019 IUBMB Life, 71(9):1336-1346, 2019.

Parvulin 14 and Parvulin 17 Bind to HBx and cccDNA and Upregulate Hepatitis B Virus Replication from cccDNA to Virion in an HBx-Dependent Manner. J Virol. 2019;93. [PMID: 30567987 DOI: 10.1128/jvi.01840-18]

The parvulin 14 (Par14) and parvulin 17 (Par17) proteins, which are both encoded by the PIN4 gene, play roles in protein folding, chromatin remodeling, DNA binding, ribosome biogenesis, and cell cycle progression. However, the effects of Par14 and Par17 on viral replication have never been explored. In this study, we found that, in the presence of HBx, either Par14 or Par17 could upregulate hepatitis B virus (HBV) replication, whereas in the absence of HBx, neither Par14 nor Par17 had any effect on replication. Overexpression of Par14/Par17 markedly increased the formation of covalently closed circular DNA (cccDNA), synthesis of HBV RNA and DNA, and virion secretion. Conversely, PIN4 knockdown significantly decreased HBV replication in HBV-transfected and -infected cells. Coimmunoprecipitation revealed that Par14/Par17 engaged in direct physical interactions with HBx in the cytoplasm, nucleus, and mitochondria, possibly mediated through substrate-binding residues on Par14/Par17 (E46/D74 and E71/D99, respectively) and conserved ¹⁹R²⁰P-²⁸R²⁹P motifs on HBx. Furthermore, these interactions enhanced HBx stability, promoted HBx translocation to the nuclear and mitochondrial fractions, and increased HBV replication. Chromatin immunoprecipitation assays revealed that, in the presence of HBx, Par14/Par17 were efficiently recruited to cccDNA and promoted transcriptional activation via specific DNA-binding residues (S19/44). In contrast, in the absence of HBx, Par14/Par17 bound cccDNA only at the basal level and did not promote transcriptional activation. Taken together, our results demonstrate that Par14 and Par17 upregulate HBV RNA transcription and DNA synthesis, thereby increasing the HBV cccDNA level, through formation of the cccDNA-Par14/17-HBx complex.IMPORTANCE The HBx protein plays an essential regulatory role in HBV replication. We found that substrate-binding residues on the human parvulin peptidylprolyl cis/trans isomerase proteins Par14 and Par17 bound to conserved arginine-proline (RP) motifs on HBx in the cytoplasm, nucleus, and mitochondria. The HBx-Par14/Par17 interaction stabilized HBx; promoted its translocation to the nucleus and mitochondria; and stimulated multiple steps of HBV replication, including cccDNA formation, HBV RNA and DNA synthesis, and virion secretion. In addition, in the presence of HBx, the Par14 and Par17 proteins bound to cccDNA and promoted its transcriptional activation. Our results suggest that inhibition or knockdown of Par14 and Par17 may represent a novel therapeutic option against HBV infection.

Effects of miR-101, miR-345 on HBV replication regulation and on the growth of liver cancer cells

The aim of the study was to investigate the effects of miRNA-101 and miRNA-345 on HBV replication and liver cancer cell growth. qPCR was performed to detect the expression of miRNA-101 and miRNA-345. The expression of HBV RNA was detected by PCR. The expression of HbsAg was detected using ELISA. BEL-7404 cell line proliferation was detected by MTT assay. The expression levels of miR-101 and miR-345 in BEL-7404 pSUPER.neo-miR-101 group and BEL-7404 pSUPER.neo-miR-345 group were significantly higher than those in BEL-7404 pSUPER.neo group (P<0.05). The expression levels of miR-101 and miR-345 in MHCC97-L pSUPER.neo-miR-101 group and MHCC97-L pSUPER.neo-miR-345 group were significantly higher than those in MHCC97-L pSUPER.neo group (P<0.05). The expression of HBV DNA in MHCC97-L pSUPER.neo-miR-101 group was significantly lower than that in MHCC97-L pSUPER.neo group (P<0.05), and the expression of HBV DNA in MHCC97-L pSUPER.neo-miR-345 group was significantly higher than that in MHCC97-L pSUPER.neo group (P<0.05). The expression of HbsAg in MHCC97-L pSUPER.neo-miR-101 group was significantly lower than that in MHCC97-L pSUPER.neo group (P<0.05), and the expression of HbsAg in MHCC97-L pSUPER.neo-miR-345 group was significantly higher than that in MHCC97-L pSUPER.neo group (P<0.05). There was a significant difference in terms of HbsAg expression between the MHCC97-L pSUPER.neo-miR-101 and MHCC97-L pSUPER.neo-miR-345 groups (P<0.05). The proliferation of BEL-7404 cells in the BEL-7404 pSUPER.neo-miR-101 group was significantly lower than that in the BEL-7404 pSUPER.neo group (P<0.05). The proliferation of BEL-7404 cells in the BEL-7404 pSUPER.neo-miR-345 group was significantly higher than that in the BEL-7404 pSUPER.neo group (P<0.05). The proliferation of BEL-7404 cells in BEL-7404 pSUPER.neo-miR-101 group was different from that in BEL-7404 pSUPER.neo-miR-345 group (P<0.05). miR-101 reduced the level of HBV replication, and inhibited the proliferation of liver cancer cells. miR-345 also upregulated the level of HBV replication, and promoted the proliferation of liver cancer cells.

Sirtuin 2 Isoform 1 Enhances Hepatitis B Virus RNA Transcription and DNA Synthesis through the AKT/GSK-3β/β-Catenin Signaling Pathway

Sirtuin 2 (Sirt2), a NAD⁺-dependent protein deacetylase, is overexpressed in many hepatocellular carcinomas (HCCs) and can deacetylate many proteins, including tubulins and AKT, prior to AKT activation. Here, we found that endogenous Sirt2 was upregulated in wild-type hepatitis B virus (HBV WT)-replicating cells, leading to tubulin deacetylation; however, this was not the case in HBV replication-deficient-mutant-transfected cells and 1.3-mer HBV WT-transfected and reverse transcriptase inhibitor (entecavir or lamivudine)-treated cells, but all HBV proteins were expressed. In HBV WT-replicating cells, upregulation of Sirt2 induced AKT activation, which consequently downregulated glycogen synthase kinase 3β (GSK-3β) and increased β-catenin levels; however, downregulation of Sirt2 in HBV-nonreplicating cells impaired AKT/GSK-3β/β-catenin signaling. Overexpression of Sirt2 isoform 1 stimulated HBV transcription and consequently HBV DNA synthesis, which in turn activated AKT and consequently increased β-catenin levels, possibly through physical interactions with Sirt2 and AKT. Knockdown of Sirt2 by short hairpin RNAs (shRNAs), inhibition by 2-cyano-3-[5-(2,5-dichlorophenyl)-2-furanyl]-N-5-quinolinyl-2-propenamide (AGK2), or dominant negative mutant expression inhibited HBV replication, reduced AKT activation, and decreased β-catenin levels. Through HBV infection, we demonstrated that Sirt2 knockdown inhibited HBV replication from transcription. Although HBx itself activates AKT and upregulates β-catenin, Sirt2-mediated signaling and upregulated HBV replication were HBx independent. Since constitutively active AKT inhibits HBV replication, the results suggest that upregulated Sirt2 and activated AKT may balance HBV replication to prolong viral replication, eventually leading to the development of HCC. Also, the results indicate that Sirt2 inhibition may be a new therapeutic option for controlling HBV infection and preventing HCC.IMPORTANCE Even though Sirt2, a NAD⁺-dependent protein deacetylase, is overexpressed in many HCCs, and overexpressed Sirt2 promotes hepatic fibrosis and associates positively with vascular invasion by primary HCCs through AKT/GSK-3β/β-catenin signaling, the relationship between Sirt2, HBV, HBx, and/or HBV-associated hepatocarcinogenesis is unclear. Here, we show that HBV DNA replication, not HBV expression, correlates positively with Sirt2 upregulation and AKT activation. We demonstrate that overexpression of Sirt2 further increases HBV replication, increases AKT activation, downregulates GSK-3β, and increases β-catenin levels. Conversely, inhibiting Sirt2 decreases HBV replication, reduces AKT activation, and decreases β-catenin levels. Although HBx activates AKT to upregulate β-catenin, Sirt2-mediated effects were not dependent on HBx. The results also indicate that a Sirt2 inhibitor may control HBV infection and prevent the development of hepatic fibrosis and HCC.

Amino acid substitutions Q129N and T131N/M133T in hepatitis B surface antigen (HBsAg) interfere with the immunogenicity of the corresponding HBsAg or viral replication ability

Variants of hepatitis B surface antigen (HBsAg) influenced its antigenicity and immunogenicity. In our study, we aim to investigate biological significance of amino acid (aa) substitutions in HBsAg, Q129 N and T131 N/M133 T, for glycosylation, antigenicity and immunogenicity of variant HBsAg (vtHBsAg) and viral replication. Expression plasmids of vtHBsAg with aa substitutions Q129 L, T123 N, Q129 N and T131 N/M133 T were constructed. Immunofluorescence (IF) staining and Western blot were simultaneously utilized to examine expression of vtHBsAg proteins in Huh7 cells transfected with vtHBsAg constructs. vtHBsAg of Q129 N and T131 N/M133 T created new N-glycosylation and displayed perinuclear distribution by IF staining with the anti-HA. Antigenicity of vtHBsAg of Q129 N and T131 N/M133 T was reduced compared with wild type (wt) HBsAg. In addition, we discovered impaired ability to induce anti-HBs responses against wtHBsAg in mice immunized with plasmids pHBsAg- Q129 N and T131 N/M133 T. Even so, efficient protective response toward wild type HBV can be primed by the two vtHBsAgs in mice. Further, we discovered that vtHBsAg with Q129 N distinctly impaired HBV replication capacity, but vtHBsAg with T131 N/M133 T had no impact on viral replication. Thus, we conclude that vtHBsAg with Q129 N or T131 N/M133 T creates new N-glycosylation and interferes with both the antigenicity and immunogenicity of vtHBsAg. And vtHBsAg with Q129 N impaired HBV replication ability.

Comparison of hepatitis B viral loads and viral antigen levels in child-bearing age women with and without pregnancy

BACKGROUND

Pregnancy is a unique physiological condition with the cellular immune functions compromised at some extents to allow the mature of growing fetus. Whether pregnancy may influence the replication of hepatitis B virus (HBV) is less studied. The present study aimed to investigate the influence of pregnancy on the replication of HBV and expression of viral antigens by comparing the levels of HBV DNA and viral antigens in pregnant and non-pregnant women.

METHODS

A total of 727 HBsAg-positive serum samples, collected from 214 pregnant women and 513 non-pregnant women of childbearing age, were included. Based on the pregnancy status, subjects were divided into four groups: nulliparous (n = 158), pregnant (n = 214), 7-12 months postpartum (n = 170), and 2-5 years postpartum (n = 185). The levels of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) were quantitatively measured with microparticle enzyme immunoassay. HBV DNA levels were detected by fluorescent real-time PCR.

RESULTS

The median ages of four groups were 25.0, 25.3, 26.2 and 29.3 years, respectively (p < 0.01). HBeAg-positive proportions were 34.2, 33.6, 35.3 and 29.2%, respectively (p = 0.624). HBV DNA levels in HBeAg-positive women were higher than those in HBeAg-negative women (7.88 vs 2.62 log IU/ml, p < 0.001). HBV DNA levels in the four groups with positive HBeAg were 7.8, 7.7, 8.0 and 8.0 log IU/ml, respectively (p = 0.057), while HBsAg titers were 4.4, 4.5, 4.6 and 4.8 log IU/ml (p = 0.086) and HBeAg titers were 3.1, 3.0, 3.1 and 3.0 log S/CO (p = 0.198). In the four groups with negative HBeAg, HBV DNA levels were 2.3, 2.6, 2.5 and 2.8 log IU/ml, respectively (p = 0.085), while HBsAg titers were 3.1, 3.3, 3.3 and 3.0 log IU/ml (p = 0.06).

CONCLUSIONS

Serum levels of HBV DNA and viral antigens showed no significant changes in nulliparous, pregnant, and postpartum women, regardless of the HBeAg status. The results indicate that pregnancy has little influence on the replication of HBV and the expression of viral antigens.

Tim-3 blockade promotes iNKT cell function to inhibit HBV replication

Increased expression of T cell immunoglobulin and mucin domain-3 (Tim-3) on invariant natural killer T (iNKT) cells is reported in chronic hepatitis B virus (HBV) infection. However, whether Tim-3 regulates iNKT cells in chronic HBV condition remains unclear. In this study, our results showed that the expression of Tim-3 was up-regulated on hepatic iNKT cells from HBV-transgenic (Tg) mice or iNKT cells stimulated with α-galactosylceramide (α-Galcer). Compared with Tim-3- iNKT cells, Tim-3+ iNKT cells expressed more IFN-γ, IL-4 and CD107a, indicating a strong relationship between Tim-3 and iNKT cell activation. Constantly, treatment of Tim-3 blocking antibodies significantly enhanced the production of IFN-γ, TNF-α, IL-4 and CD107a in iNKT cells both in vivo and in vitro. This Tim-3- mediated suppression of iNKT cells was further confirmed in Tim-3 knockout (KO) mice. Moreover, Tim-3 blockade promoted α-Galcer-triggered inhibition of HBV replication, displaying as the decreased HBV DNA and HBsAg level in serum, and down-regulated pgRNA expression in liver tissues. Collectively, our data, for the first time, demonstrated the potential role of Tim-3 blockade in promoting iNKT cell-mediated HBV inhibition. Therefore, combination of α-Galcer with Tim-3 blockade might be a promising approach in chronic hepatitis B therapy.

Mechanisms and Effects on HBV Replication of the Interaction between HBV Core Protein and Cellular Filamin B

Hepatitis B virus (HBV) infection is one of the major problems that threatens global health. There have been many studies on HBV, but the relationship between HBV and host factors is largely unexplored and more studies are needed to clarify these interactions. Filamin B is an actin-binding protein that acts as a cytoskeleton protein, and it is involved in cell development and several signaling pathways. In this study, we showed that filamin B interacted with HBV core protein, and the interaction promoted HBV replication. The interaction between filamin B and core protein was observed in HEK 293T, Huh7 and HepG2 cell lines by co-immunoprecipitation and co-localization immnofluoresence. Overexpression of filamin B increased the levels of HBV total RNAs and pre-genome RNA (pgRNA), and improved the secretion level of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg). In contrast, filamin B knockdown inhibited HBV replication, decreased the level of HBV total RNAs and pgRNA, and reduced the secretion level of HBsAg and HBeAg. In addition, we found that filamin B and core protein may interact with each other via four blocks of argentine residues at the C-terminus of core protein. In conclusion, we identify filamin B as a novel host factor that can interact with core protein to promote HBV replication in hepatocytes. Our study provides new insights into the relationship between HBV and host factors and may provide new strategies for the treatment of HBV infection.

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.

The role of microRNAs in hepatocyte metabolism and hepatitis B virus replication

Though efficient vaccines against hepatitis B virus (HBV) and antiviral therapies are available, chronic HBV infection is still a global health problem. The process of HBV infection and HBV life cycle are extensively studied in last decades, however, the mechanisms of HBV-induced alterations of host cell metabolisms and host factors involved in modulating of viral replication are not fully understood. Thus, it is an important issue to examine these specific HBV-host interactions for development of novel strategies for antiviral therapies. Recently, microRNAs (miRNAs), a class of post-transcriptional regulatory small RNA, seem to be the relevant fine tuning factors of various cellular activities and pathways, including cell growth, metabolism, and viral replication. In this review, we summarize the up to date knowledge concerning the virus-host interactions and emphasizing on the role of miRNAs in regulation of HBV replication and host cell metabolism.

Cleaved c-FLIP mediates the antiviral effect of TNF-α against hepatitis B virus by dysregulating hepatocyte nuclear factors

BACKGROUND & AIMS

Cytokines are key molecules implicated in the defense against virus infection. Tumor necrosis factor-alpha (TNF-α) is well known to block the replication of hepatitis B virus (HBV). However, the molecular mechanism and the downstream effector molecules remain largely unknown.

METHODS

In this study, we investigated the antiviral effect and mechanism of p22-FLIP (FLICE-inhibitory protein) by ectopic expression in vitro and in vivo. In addition, to provide the biological relevance of our study, we examined that the p22-FLIP is involved in TNF-α-mediated suppression of HBV in primary human hepatocytes.

RESULTS

We found that p22-FLIP, a newly discovered c-FLIP cleavage product, inhibited HBV replication at the transcriptional level in both hepatoma cells and primary human hepatocytes, and that c-FLIP conversion to p22-FLIP was stimulated by the TNF-α/NF-κB pathway. p22-FLIP inhibited HBV replication through the upregulation of HNF3β but downregulation of HNF4α, thus inhibiting both HBV enhancer elements. Finally, p22-FLIP potently inhibited HBV DNA replication in a mouse model of HBV replication.

CONCLUSIONS

Taken together, these findings suggest that the anti-apoptotic p22-FLIP serves a novel function of inhibiting HBV transcription, and mediates the antiviral effect of TNF-α against HBV replication.

Cyclin D2 plays a regulatory role in HBV replication

Hepatitis B virus (HBV) infection is the leading cause of liver diseases. However, the molecular mechanisms of HBV infection and carcinogenesis have not been fully elucidated. In this study, we found that cyclin D2 was upregualted in HBV-expressing cells and liver tissues of HBV-transgenic mice. Gene silencing of cyclin D2 inhibited HBV DNA replicative intermediates, 3.5 kb mRNA, core protein level, as well as the secretions of HBsAg and HBeAg. On the contrary, overexpression of cyclin D2 promoted HBV replication. Furthermore, cyclin D2 regulated HBV replication by enhancing the activity of HBV core and Sp1 promoters by targeting transcription factor CREB2. Silencing of CREB2 abolished enhancement of HBV replication induced by cyclin D2. Together, our study has uncovered a positive role of cyclin D2 in HBV replication. It is conceivable that therapeutic application of cyclin D2 inhibitor in HBV infection therapy.

Reduced ADP-ribosylation by PARP1 natural polymorphism V762A and by PARP1 inhibitors enhance Hepatitis B virus replication

HepG2 and Huh7 cell lines are frequently used as models to study viral hepatitis and hepatocellular carcinoma. However, they exhibit significantly different capacities in their ability to support hepatitis B virus (HBV) replication. To investigate the basis for this, transcription factor-binding motifs at the HBV core promoter (HBVCP) were tested in luciferase reporter constructs to identify the possible role of host factors. Among the transcription factors screened: PARP1, SP1, HNF4α, HNF3, hB1F and HNF1, deletion of the PARP1 binding motif abrogated transcriptional activity at the HBVCP in HepG2 but not Huh7 cells. Sequencing of the PARP1 gene revealed that HepG2 cells carried an Ala762 allele which has low ADP-ribosylation activity, which was shown to have increased PARP1 binding affinity to its cognate motif thus resulting in higher transcriptional activity. PARP1 inhibitors that are being developed as broad cancer therapeutics also target PARP1 ADP-ribosylation enzymatic function. Four PARP1 inhibitors: PJ-34, ABT888, AZD2281 and AG014699 were tested for their effect on HBV replication. All four small molecules effectively enhanced HBV replication in vitro, confirming the role of PARP1 in HBV replication and that alteration of ADP-ribosylation by mutation or drugs can affect HBV replication. Our data demonstrate that natural polymorphisms in the host affecting proteins such as PARP1 can have a significant effect on HBV replication. Hence, patients who are infected with HBV and are on clinical trials involving PARP1 inhibitors may be at risk from unintended side-effects such as exacerbation of HBV replication.

Relevance of interleukin-10RB to chronic hepatitis B virus infection and biological activities of interferon-λ and interleukin-22

Purpose

The association of a single nucleotide polymorphism of interleukin (IL)-10RB codon 47 with the chronic hepatitis B virus (HBV) infection has been reported in two ethnic populations with different results, but not in a Korean population. IL-10RB is a subunit of receptor complexes for interferon-lambda (IFN-λ) and IL-22, which have antiviral and hepatocyte-protective activity, respectively. This study examined the association of IL-10RB K47E with the outcomes of HBV infection in Korean subjects and the cellular response to these cytokines.

Methods

Genotypes of IL-10RB and the outcomes of HBV infection were analyzed in 1,000 Korean patients. The effect of IFN-λ or IL-22 on HBV replication and cell viability was assessed in hepatoma cells expressing IL-10RB K47 or E47. The transcript level of IL-10RB was examined in Epstein Barr virus-transformed B cells and hepatoma cells.

Results

IL-10RB K47E was associated with chronic HBV infection but not with hepatoma in the Korean population. IL-10RB K47E was associated with the transcript level of IL-10RB in transformed B cells but not with the responses in hepatoma cells to IFN-λ or IL-22. HBV replication or 5-fluorouracil-induced cell death was suppressed by treatment of IFN-λ or IL-22 in an IL-10RB K47E-independent manner.

Conclusions

IL-10RB K47E is related to chronic HBV infection in a Korean population, but not to cellular responsiveness to IFN-λ and IL-22.

Electronic supplementary material

The online version of this article (doi:10.1007/s12072-012-9361-8) contains supplementary material, which is available to authorized users.

Role of HBx and truncated HBx in HBV replication

As one of the principal causes of liver diseases, such as chronic hepatitis B, hepatic cirrhosis and hepatocellular carcinoma (HCC), hepatitis B virus (HBV) infection has been a major health problem worldwide. It is estimated that more than 500 million individuals have been infected with HBV worldwide and 1 million die of HBV infection-associated diseases annually. HBV X protein (HBx) is a multifunctional protein that can modulate various cellular processes and plays a crucial role in the pathogenesis of HCC. In recent years, the role of HBx in HBV replication has been more or less confirmed. In addition, more and more natural HBx truncated mutants and their roles in HBV replication have been found. This review aims to elucidate the roles of HBx and truncated HBx in HBV replication.