HBsAg Secretion Research Articles

Interferon-stimulated gene (ISG12a) suppresses hepatitis B virus replication in Huh 7 cells line

Hepatitis B virus (HBV) and its associated chronic liver disease pose a significant health hazard. Chronic HBV infection is a major contributor to the development of liver cirrhosis, liver fibrosis, and liver cancer. This study focused on ISG12a and its inhibitory effect in Huh7 cells on HBV gene expression and replication. The mammalian hepatoma cells Huh7 were transfected with the pHBV1.3 vector (pCAGGS) or HA-tagged ISG12a to determine the overexpression, to test this hypothesis further, we did knockdown or silencing by transducing Huh7 cells with lentiviruses containing shRNAs targeting ISG12a or scramble control shRNA (shControl). The expression of ISG12a was evaluated through western blot analysis. The HBsAg and HBeAg secretion in the Huh7 cells’ culture media was examined using an ELISA test. The qRT-PCR confirmed the mRNA and 3.5 mRNA Kb of ISG12a. The HBV total RNA was extracted and evaluated through a Northern blot. The isolated DNA was detected through qPCR. Additionally, a mechanistic study of enhancer II (EnhII/Cp) was examined through luciferase reporter testing. Our research findings indicate that ISG12a, an interferon-stimulated gene (ISG), plays a crucial role in suppressing the replication and gene expression of HBV. According to our study using the Huh7 cell system, overexpression of ISG12a resulted in a notable reduction in HBV protein levels as well as intracellular core-associated DNA and RNA levels. On the other hand, silencing ISG12a in Huh7 cells resulted in increased HBV RNA transcripts, DNA, and secreted proteins, indicating that ISG12a plays a role in suppressing HBV replication. Additionally, the research revealed that ISG12a inhibits the function of the EnhII/Cp promoter, which results in reduced HBV gene expression. The EnhII/Cp promoter is involved in regulating HBV gene expression, and the study showed that ISG12a restricts its activity. ISG12a may have a regulatory role in controlling the expression of HBV genes. These findings highlight the importance of ISG12a in HBV gene expression and provide valuable insights for understanding its antiviral function.

Lappanolides A−N, fourteen undescribed sesquiterpenoids from Saussurea costus (Syn. Saussurea lappa) and their anti HBV activity

Lappanolides A−N (1–14), 14 undescribed sesquiterpenoids, along with 23 known ones (15–37), were isolated from the roots of Saussurea costus, which were primarily categorized into eudesmane, guaiane, and germacrane types. Lappanolide A (1) possessed an unprecedented pseudo-disesquiterpenoids. Their structures and absolute configurations were established using physical data analyses (HRESIMS, IR, 1D and 2D NMR) and ECD calculations. All isolated compounds were tested for anti-hepatitis B virus (anti-HBV) activity. Ten compounds (1, 9, 11, 12, 19, 22, 28, 29, 31, and 36) exhibited activities against HBsAg secretions as determined by ELISA assay, with IC50 values ranging from 5.2 to 45.7 μM. In particular, compounds 28 and 29 showed inhibition of HBsAg secretion with IC50 values of 5.28 and 5.30 μM, and CC50 values of 9.85 and 6.37 μM, respectively, though they all exhibited low selectivity. Several compounds displayed cytotoxicity in the MTT assay. Among them, compound 28 was the most notable and was chosen for further study using flow cytometry. The result showed that it significantly induced HepG2 cell arrest in the S phase and induced apoptosis.

M133S mutation possibly involve in the ER stress and mitophagy pathway in maintenance hemodialysis patients with occult hepatitis B infection

Occult hepatitis B virus infection (OBI) is characterized by the presence of HBV DNA in the absence of detectable HBsAg. OBI is an important risk factor for cirrhosis and hepatocellular carcinoma, but its pathogenesis has not been fully elucidated. Mutations in the HBV preS/S genes can lead to impaired secretion of either HBsAg or S-protein resulting in the accumulation of defective viruses or S protein in cells. In our previous work, the M133S mutation was present in the HBV S gene of maintenance hemodialysis (MHD) patients with OBI. In this study, we investigated the potential role of amino acid substitutions in S proteins in S protein production and secretion through the construction of mutant S gene plasmids, structural prediction, transcriptome sequencing analysis, and in vitro functional studies. Protein structure prediction showed that the S protein M133S mutant exhibited hydrophilic modifications, with greater aggregation and accumulation of the entire structure within the membrane phospholipid bilayer. Differential gene enrichment analysis of transcriptome sequencing data showed that differentially expressed genes were mainly concentrated in protein processing in the endoplasmic reticulum (ER). The expression of heat shock family proteins and ER chaperone molecules was significantly increased in the wild-type and mutant groups, whereas the expression of mitochondria-associated proteins was decreased. Immunofluorescence staining and protein blotting showed that the endoplasmic reticulum-associated protein PDI, the autophagy marker LC3, and the lysosome-associated protein LAMP2 co-localized with the S proteins in the wild-type and mutant strains, and their expression was increased. The mitochondria-associated TOMM20 protein was also co-expressed with the S protein, but expression was significantly reduced in the mutant. The M133S mutation in the S gene is expressed as a defective and misfolded protein that accumulates in the endoplasmic reticulum causing secretion-impaired endoplasmic reticulum stress, which in turn triggers mitochondrial autophagy and recruits lysosomes to fuse with the autophagosome, leading to mitochondrial clearance. This study preliminarily demonstrated that the mutation of M133S in the S gene can cause OBI and is associated with disease progression, providing a theoretical basis for the diagnosis and treatment of OBI.

Exploration of 1-(indolin-1-yl)-2-(thiazol-2-yl)ethan-1-one derivatives as novel anti-HBV agent with potential TLR7-agonistic effect

Hepatitis B virus (HBV) infection, as a serious global public health issue, is closely related to the immune dysfunction. Herein, thirty-seven 1-(indolin-1-yl)-2-(thiazol-4-yl)ethan-1-one derivatives were prepared as potential immunomodulatory anti-HBV agents. Anti-HBV activity evaluation confirmed compound 11a could significantly suppress the HBV DNA replication in both wild and resistant HBV stains, with IC50 values of 0.13 μM and 0.36 μM, respectively. Preliminary action mechanism studies showed that 11a had an inhibitory effect on cellular HBsAg secretion and could effectively activate TLR7, thereby inducing the secretion of TLR7-regulated cytokines IL-12, TNF-α and IFN-α in human PBMC cells. SPR analysis confirmed that 11a could bind to TLR7 protein with an affinity of 7.06 μM. MD simulation predicted that 11a could form tight interactions with residues in the binding pocket of TLR7. Physicochemical parameters perdition and pharmacokinetic analysis indicated that 11a displayed relatively favorable drug-like properties. Considering all the results, compound 11a might be a promising lead for developing novel immunomodulatory anti-HBV agents.

Synthesis and evaluation of pentacyclic triterpenoids conjugates as novel HBV entry inhibitors targeting NTCP receptor

Chronic liver diseases caused by hepatitis B virus (HBV) are the accepted main cause leading to liver cirrhosis, hepatic fibrosis, and hepatic carcinoma. Sodium taurocholate cotransporting polypeptide (NTCP), a specific membrane receptor of hepatocytes for triggering HBV infection, is a promising target against HBV entry. In this study, pentacyclic triterpenoids (PTs) including glycyrrhetinic acid (GA), oleanolic acid (OA), ursolic acid (UA) and betulinic acid (BA) were modified via molecular hybridization with podophyllotoxin respectively, and resulted in thirty-two novel conjugates. The anti-HBV activities of conjugates were evaluated in HepG2.2.15 cells. The results showed that 66% of the conjugates exhibited lower toxicity to the host cells and had significant inhibitory effects on the two HBV antigens, especially HBsAg. Notably, the compounds BA-PPT1, BA-PPT3, BA-PPT4, and UA-PPT3 not only inhibited the secretion of HBsAg but also suppressed HBV DNA replication. A significant difference in the binding of active conjugates to NTCP compared to the HBV PreS1 antigen was observed by SPR assays. The mechanism of action was found to be the competitive binding of these compounds to the NTCP 157–165 epitopes, blocking HBV entry into host cells. Molecular docking results indicated that BA-PPT3 interacted with the amino acid residues of the target protein mainly through π-cation, hydrogen bond and hydrophobic interaction, suggesting its potential as a promising HBV entry inhibitor targeting the NTCP receptor.

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.

Oxymatrine Inhibition of Hepatitis B Virus Replication Through ERK1/2 Pathway and HNF1α and HNF4α Block in vitro.

To explore the molecular mechanism of oxymatrine (OM) by increasing the phosphorylation of ERK1/2 signal factor and blocking the transcription factors HNF1α and HNF4α expression against hepatitis B virus (HBV) antigen secretion and HBV DNA replication in HepG2.2.15 cells. An experimental study. Place and Duration of the Study: Department of Laboratory Medicine,First Affiliated Hospital of Gannan Medical University, Jiangxi, China, between May 2020 and December 2022. HepG2.2.15 cells, known for stably expressing HBV particles, were utilised as a cell-based model to explore potential pathways pertaining to the OM inhibition of HBV replication. An MTT assay was utilised to measure cytotoxicity. HBsAg or HBeAg content was measured using an enzyme-linked immunosorbent assay kit. HBV DNA in cell-free culture media was examined using a fluorescent quantitative PCR kit. Real-time PCR was utilised to analyse HNF1α and HNF4α mRNA expression, whereas Western blotting was performed to evaluate HNF1α, HNF4α, and ERK1/2 protein expression. OM inhibited HBV DNA copy number in the cell supernatant, 3.5-kb RNA gene expression in cells, and HBsAg and HBeAg secretion. OM upregulated p-ERK1/2 protein and significantly downregulated HNF1α and HNF4α gene transcription and protein translation. OM may inhibit the replication of HBV by inducing the phosphorylation of ERK1/2 and blocking the transcription factors HNF1α and HNF4α expression that are essential for viral replication. Oxymatrine, ERK1/2, Hepatocyte nuclear factor, Anti-HBV.

Hepatitis B doubly spliced protein (HBDSP) promotes hepatocellular carcinoma cell apoptosis via ETS1/GATA2/YY1-mediated p53 transcription.

Hepatitis B virus (HBV) spliced variants are associated with viral persistence or pathogenicity. Hepatitis B doubly spliced protein (HBDSP), which has been previously reported as a pleiotropic transactivator protein, can potentially serve as an HBV virulence factor. However, the underlying mechanisms of HBDSP in HBV-associated liver diseases remain to be elucidated. In this study, we revealed that HBDSP promotes cellular apoptosis and induces wt-p53-dependent apoptotic signaling pathway in wt-p53 hepatocellular cells by transactivating p53 transcription, and increases the release of HBV progeny. Therefore, HBDSP may promote the HBV particles release through wt-p53-dependent hepatocellular apoptosis. Our findings suggest that blocking HBDSP-induced wt-p53-dependent apoptosis might have therapeutic values for chronic hepatitis B.

Structural insights into modeling of hepatitis B virus reverse transcriptase and identification of its inhibitors from potential medicinal plants of Western Ghats: an in silico and in vitro study

The present study was proposed to model full-length HBV-RT and investigate the intermolecular interactions of known inhibitor and libraries of phytocompounds to probe the potential natural leads by in silico and in vitro studies. Homology modeling of RT was performed by Phyre2 and Modeller and virtual screening of ligands implemented through POAP pipeline. Molecular dynamics (MD) simulation (100 ns) and MM-GBSA calculations were performed using Schrodinger Desmond and Prime, respectively. Phytocompounds probable host protein targets gene set pathway enrichment and network analysis were executed by KEGG database and Cytoscape software. Prioritized plant extracts/enriched fraction LC-MS analysis was performed and along with pure compound, RT inhibitory activity, time-dependent HBsAg and HBeAg secretion, and intracellular HBV DNA, and pgRNA by qRT-PCR was performed in HepG2.2.15 cell line. Among the screened chemical library of 268 phytocompounds from 18 medicinal plants, 15 molecules from Terminalia chebula (6), Bidens pilosa (5), and Centella asiatica (4)) were identified as potential inhibitors of YMDD and RT1 motif of HBV-RT. MD simulation demonstrated stable interactions of 15 phytocompounds with HBV-RT, of which 1,2,3,4,6-Pentagalloyl Glucose (PGG) was identified as lead molecule. Out of 15 compounds, 11 were predicted to modulate 39 proteins and 15 molecular pathways associated with HBV infection. TCN and TCW (500 µg/mL) showed potent RT inhibition, decreased intracellular HBV DNA, and pgRNA, and time-dependent inhibition of HBsAg and HBeAg levels compared to PGG and Tenofovir Disoproxil Fumarate. We propose that the identified lead molecules from T. chebula as promising and cost-effective moieties for the management of HBV infection. Communicated by Ramaswamy H. Sarma

RNA binding protein TIAR modulates HBV replication by tipping the balance of pgRNA translation

The pregenomic RNA (pgRNA) of hepatitis B virus (HBV) serves not only as a bicistronic message RNA to translate core protein (Cp) and DNA polymerase (Pol), but also as the template for reverse transcriptional replication of viral DNA upon packaging into nucleocapsid. Although it is well known that pgRNA translates much more Cp than Pol, the molecular mechanism underlying the regulation of Cp and Pol translation efficiency from pgRNA remains elusive. In this study, we systematically profiled HBV nucleocapsid- and pgRNA-associated cellular proteins by proteomic analysis and identified TIA-1-related protein (TIAR) as a novel cellular protein that binds pgRNA and promotes HBV DNA replication. Interestingly, loss- and gain-of-function genetic analyses showed that manipulation of TIAR expression did not alter the levels of HBV transcripts nor the secretion of HBsAg and HBeAg in human hepatoma cells supporting HBV replication. However, Ribo-seq and PRM-based mass spectrometry analyses demonstrated that TIAR increased the translation of Pol but decreased the translation of Cp from pgRNA. RNA immunoprecipitation (RIP) and pulldown assays further revealed that TIAR directly binds pgRNA at the 5’ stem-loop (ε). Moreover, HBV replication or Cp expression induced the increased expression and redistribution of TIAR from the nucleus to the cytoplasm of hepatocytes. Our results thus imply that TIAR is a novel cellular factor that regulates HBV replication by binding to the 5’ ε structure of pgRNA to tip the balance of Cp and Pol translation. Through induction of TIAR translocation from the nucleus to the cytoplasm, Cp indirectly regulates the Pol translation and balances Cp and Pol expression levels in infected hepatocytes to ensure efficient viral replication.

Host immunity and HBV S gene mutation in HBsAg-negative HBV-infected patients.

Clinically, some patients whose HBsAg becomes negative owing to antiviral therapy or spontaneously still show a low level of HBV DNA persistence in serum. T-lymphocyte subsets, cytokine levels and HBV S gene sequences were analyzed in this study. A total of 52 HBsAg-negative and HBV DNA-positive patients(HBsAg-/HBV DNA+ patients), 52 persistently HBsAg-positive patients(HBsAg+/HBV DNA+ patients) and 16 healthy people were evaluated. T-lymphocyte subsets of these patients were detected by flow cytometry, serum cytokines and chemokines were detected by the Luminex technique, and the HBV S region was evaluated by Sanger sequencing. T%, T-lymphocyte, CD8+ and CD4+T lymphocyte were lower in the HBsAg-negative group than in the HC group. Compared with the HBsAg-positive group, the HBsAg-negative group had lower levels in T lymphocyte %, CD8+T lymphocyte %, CD8+T lymphocyte and CD4/CD8. These difference were statistically significant (P<0.05). Serum IFN-γ, IFN-α and FLT-3L levels were significantly higher in the HBsAg-negative group than in the HBsAg-positive group (P<0.05). However, levels of many cytokines related to inflammation (i.e., IL-6, IL-8, IL10, IL-12, IL-17A) were lower in the HBsAg-negative group. Fifty-two HBsAg-negative samples were sequenced, revealing high-frequency amino acid substitution sites in the HBV S protein, including immune escape mutations (i.e., Y100C, S114T, C124Y, P127L, G130R, T131N, M133T, C137S, G145A) and TMD region substitutions (i.e., E2K/R/D, G7D/R, G10D, A17R, F20L/S, L21V, L22V). According to the results of T-lymphocyte subsets and serum cytokines, it can be deduced that the cellular immune function of HBsAg-negative patients is superior to that of HBsAg-positive patients, with attenuation of liver inflammation. HBsAg-negative patients may show a variety of mutations and amino acid replacement sites at high frequency in the HBV S region, and these mutations may lead to undetectable HBsAg, HBsAg antigenic changes or secretion inhibition.

Peptide YY inhibits transcription and replication of hepatitis B virus by suppressing promoter/enhancer activity.

Hepatitis B virus (HBV) infection is a noteworthy cause of liver diseases, especially cirrhosis and hepatocellular carcinomas. However, the interaction between the host and HBV has not been fully elucidated. Peptide YY (PYY) is a 36-amino-acid gastrointestinal hormone that is mainly involved in the regulation of the human digestive system. This study found that PYY expression was reduced in HBV-expressing hepatocytes and HBV patients. Overexpression of PYY could significantly inhibit HBV RNA, DNA levels, and the secretion of HBsAg. In addition, PYY inhibits HBV RNA dependent on transcription through reducing the activities of CP/Enh I/II, SP1 and SP2. Meanwhile, PYY blocks HBV replication independent on core, polymerase protein and ε structure of pregenomic RNA. These results suggest that PYY can impair HBV replication by suppressing viral promoters/enhancers in hepatocytes. Our data shed light on a novel role for PYY as anti-HBV restriction factor.

Undescribed amino acid-sesquiterpene lactone adducts and sesquiterpene glycosides from the roots of Saussurea lappa and their anti-HBV activity

Saussurea lappa (Asteraceae family), a traditional Chinese medicine, has been found to possess anti-inflammatory, immune-promoting, antibacterial, antitumor, anti-HBV, cholestatic, and hepatoprotective activities. Herein, two undescribed amino acid-sesquiterpene lactone adducts, saussureamines G and H (1 and 2), and two new sesquiterpene glycosides, saussunosids F and G (3 and 4), along with 26 known sesquiterpenoids (5–30) have been isolated from the roots of S. lappa. Their structures and absolute configurations of these compounds were established by physical data analyses such as HRESIMS, IR, 1D and 2D NMR and ECD calculations. All isolated compounds were tested for anti-hepatitis B virus (anti-HBV) activity. Ten compounds (5, 6, 12, 13, 17, 19, 23, 26, 29, and 30) exhibited activities against the secretions of HBsAg and HBeAg. In particular, compound 6 showed inhibition of HBsAg and HBeAg secretion with IC50 values of 11.24 and 15.12 μM, with SI values of 1.25 and 0.93, respectively. Molecular docking studies were also conducted on the anti-HBV compounds. Overall, this study provides insights into the potential therapeutic uses of the compounds found in the roots of S. lappa, particularly in the treatment of hepatitis B virus infections.

Unexpected rise in the circulation of complex HBV variants enriched of HBsAg vaccine-escape mutations in HBV genotype-D: potential impact on HBsAg detection/quantification and vaccination strategies

ABSTRACT Specific HBsAg mutations are known to hamper HBsAg recognition by neutralizing antibodies thus challenging HBV-vaccination efficacy. Nevertheless, information on their impact and spreading over time is limited. Here, we characterize the circulation of vaccine-escape mutations from 2005 to 2019 and their correlation with virological parameters in a large cohort of patients infected with HBV genotype-D (N = 947), dominant in Europe. Overall, 17.7% of patients harbours ≥1 vaccine-escape mutation with the highest prevalence in subgenotype-D3. Notably, complex profiles (characterized by ≥2 vaccine-escape mutations) are revealed in 3.1% of patients with a prevalence rising from 0.4% in 2005–2009 to 3.0% in 2010–2014 and 5.1% in 2015–2019 (P = 0.007) (OR[95%CI]:11.04[1.42–85.58], P = 0.02, by multivariable-analysis). The presence of complex profiles correlates with lower HBsAg-levels (median[IQR]:40[0–2905]IU/mL for complex profiles vs 2078[115–6037]IU/ml and 1881[410–7622]IU/mL for single or no vaccine-escape mutation [P < 0.02]). Even more, the presence of complex profiles correlates with HBsAg-negativity despite HBV-DNA positivity (HBsAg-negativity in 34.8% with ≥2 vaccine-escape mutations vs 6.7% and 2.3% with a single or no vaccine-escape mutation, P < 0.007). These in-vivo findings are in keeping with our in-vitro results showing the ability of these mutations in hampering HBsAg secretion or HBsAg recognition by diagnostic antibodies. In conclusion, vaccine-escape mutations, single or in complex profiles, circulate in a not negligible fraction of HBV genotype-D infected patients with an increasing temporal trend, suggesting a progressive enrichment in the circulation of variants able to evade humoral responses. This should be considered for a proper clinical interpretation of HBsAg-results and for the development of novel vaccine formulations for prophylactic and therapeutic purposes.

Dihydromyricetin inhibits Hepatitis B virus replication by activating NF-κB, MAPKs, and autophagy in HepG2.2.15 cells.

Hepatitis B virus (HBV) infection is a severe global health problem, and there has been no effective method to eliminate HBV. This study was designed to explore the pharmacological mechanism of Dihydromyricetin (DHM) treatment on HBV replication in vitro. DHM is a flavonoid compound from Ampelopsis grossedentata. Using HepG2.2.15 cells, which can stably express HBV in vitro, we demonstrated that DHM treatment dramatically reduced HBV replication and secretions of HBsAg and HBeAg. Meanwhile, DHM inhibited mRNA expression of HBV RNAs in HepG2.2.15 cells, including Total HBV RNA, HBV pregenomic RNA (pgRNA), and HBV precore mRNA (pcRNA). Also, DHM elevated the mRNA expressions of inflammatory cytokines and antiviral effectors. In contrast, DHM decreased the mRNA level of HNF4α, which positively correlated with HBV replication. Further studies show that the activation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway played a critical role in DHM-initiated inhibition of HBV replication in HepG2.2.15 cells. Besides, activated autophagy was another contributor that may accelerate the clearance of HBV components. In summary, DHM could suppress HBV replication by activating NF-κB, MAPKs, and autophagy in HepG2.2.15 cells. Our studies shed light on the future application of DHM for the clinical treatment of HBV infection.

Synthesis and evaluation of 3-phenylisoxazoline derivatives as non-nucleoside hepatitis B virus inhibitors

A series of new 3-phenylisoxazoline derivatives were designed and synthesized. These compounds were assayed with HepG2 2.15 cell to evaluate their anti-hepatitis B virus (HBV) activities. Results of evaluation showed that most of the compounds were effective to inhibit HBV and more effective than 3 TC (Lamivudine). Compound 33, 34, 36 and 27 among them showed strong anti-HBV activities on inhibiting secretion of HBsAg with IC50 in 4.87 μM (SI = 11.71), 7.36 μM (SI = 25.25), 37.00 μM (SI = 8.69) and 37.30 μM (SI = 13.98) respectively. Compounds 23, 37, 39 and 36 strongly inhibited secretion of HBeAg with IC50 in 12.03 μM (SI = 2.91), 15.3 μM (SI = 1.36), 16.22 μM (SI = 1.60) and 47.99 μM (SI = 6.71) respectively. As non-nucleoside agents, these compounds inhibited replication of HBV DNA. Results of molecular docking study revealed bioactive compounds bound to HBV core protein with strong interaction. Our work may provide a new group of non-nucleoside compounds as anti-HBV agents.

The hepatitis delta virus and chronic hepatitis D.

The hepatitis delta virus and chronic hepatitis D.

Occult infection with hepatitis B virus PreS variants synergistically promotes hepatocellular carcinoma development in a high-fat diet context by generating abnormal ceramides

BackgroundSome occult hepatitis B virus (HBV) infections are resulted from PreS mutations that reduce secretion of envelope protein (HBsAg). We investigated the ceramide amounts and species in hepatocytes infected with PreS variants that were isolated from HBsAg-seronegative patients with hepatocellular carcinoma (HCC) and the ceramide effects on autochthonous HCC development in murine models.MethodsHBV PreS/S regions from 35 HBsAg-seronegative HCC patients were sequenced. Hepatocyte cell lines and male C57BL/6J mouse livers were transfected with two PreS variant representatives. The ceramides with variated lengths of fatty acyl chains were quantified. Tumour development was examined in the HBV-transfected mice fed different diet types.ResultsIn HBsAg-seronegative HCC patients, nonneoplastic liver tissues harboured HBsAg and replication-competent HBV. The most frequently detected PreS/S variants carried mutations of altered amino acid properties in HBsAg compared with an isolate from one HBsAg-seronegative HCC patient. Hepatocyte infection with PreS variants caused HBsAg retention within the endoplasmic reticulum and generated more amounts of ceramides with C16:0 ceramide elevated the highest. Saturated fatty acids aggravated the PreS variant-infected hepatocytes to generate abnormal amounts and species of ceramides, which with HBV proteins synergistically activated NLRP3 inflammasome in liver inflammatory macrophages. Liver tumours were only detected in HBV-transfected mice fed high-fat diet, with higher tumour loads in the PreS variant-transfected, associated with abnormal ceramide generation.ConclusionsHBV PreS mutations which altered amino acid properties of envelope proteins inhibited HBsAg secretion. Hepatocyte infection with PreS variants generated abnormal ceramides which with HBV proteins coactivated NLRP3 inflammasome in liver macrophages to promote autochthonous HCC development.

Future anti-HDV treatment strategies, including those aimed at HBV functional cure.

HDV is a defective virus that uses the HBV surface antigen to enter hepatocytes. It is associated with an accelerated course of liver fibrosis progression and an increased risk of hepatocellular carcinoma. Negative HDV RNA 24 weeks after the end of therapy has been proposed as an endpoint but late relapses make this endpoint suboptimal, hence HBsAg loss appears to be more appropriate. Current HBV antiviral agents have poor activity against HDV hence the search for improved therapy. Drugs only active against HDV, such as lonafarnib, have shown efficacy in combination with nucleoside analogues and peginterferon, but do not lead to HBsAg loss. HBsAg loss sustained 24 weeks after the end of therapy with negative HBV DNA is termed functional cure. Agents that are being investigated for functional cure include those that inhibit replication such as entry inhibitors, polymerase inhibitors and capsid assembly modulators but seldom lead to functional cure. Agents that reduce HBV antigen load such as RNA interference and inhibitors of HBsAg secretion are promising. Immunomodulators on their own seldom achieve functional cure, hence these agents in combination to assess the optimal combination are being investigated. Consequently, agents leading to functional cure of HBV are ideal for both HBV and HDV.

Role of S protein transmembrane domain mutations in the development of occult hepatitis B virus infection

ABSTRACT Occult HBV infection (OBI) is a special infection status during Hepatitis B virus (HBV) infection. The underlying mechanism of its occurrence remains unclear. This study conducted sequencing analysis on 104 OBI plasma samples and 524 HBsAg positive samples from 29 blood centres, and searched for high-frequency mutations in transmembrane domain (TMD) of S protein in the OBI population. Plasmids with TMD high-frequency mutations were constructed, in vivo and in vitro functional experiments were performed to investigate possible molecular mechanisms of OBI occurrence. We found 22 high-frequency TMD mutations in genotype B OBI strains. Among them, five mutations can lead to impairment of HBsAg secretion; seven mutations had accumulated intracellular HBsAg while extracellular HBsAg didn’t decrease compared to wildtype. This study chose C85R from TMD2, F220C, and F220Y from TMD4 for further exploration. Protein structure predication showed these three mutant HBsAg displayed changed hydrophilic properties and tended to accumulate in the phospholipid bilayer of cell membrane. Mutant HBsAg’s secretion disorder may induce OBI. On the other hand, V168A + V177A from TMD3 expressed increased HBsAg both in intracellular and extracellular levels. This mutation had most unstable natural conformation and may be inclined to transition into V177A or V168A + S174N + V177A. These three mutations were more prone to mixed infection, presenting a state of coexistence, thus approaching the impaired secretion pattern of OBI. This study demonstrated TMD mutations could contribute to the occurrence of OBI and provided a theoretical basis for OBI study and the functional cure of chronic hepatitis B virus infection.