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Hepatitis B Research Review: May

This month, researchers at Jilin University in Changchun, China have discovered an anti-HBV role of the HIV-1 host restriction factor SERINC5. At Seoul National University in South Korea, HBV researchers have elucidated a mechanism by which HBV hijacks host transcription regulation. Researchers from the Paul Ehrlich Institute in Langen, Germany have demonstrated that HBV DNA can be sensed by the cGAS/STING pathway, but is not in the context of natural hepatocyte infection.  

  • SERINC5 Inhibits the Secretion of Complete and Genome-Free Hepatitis B Virions Through Interfering with the Glycosylation of the HBV Envelope – Frontiers in Microbiology

This paper from Jilin University in Changchun, China reveals the protein serine incorporator 5 (SERINC5) as a host restriction factor for HBV virion secretion. The SERINC family of proteins facilitate lipid biosynthesis and transport in mammalian cells. SERINC5 was recently shown to restrict the replication of HIV-1 and other retroviruses by incorporating into the membrane of budding virions and preventing their entry into target cells. Additionally, the HIV-1 protein NEF as well as the structurally unrelated murine leukemia virus (MLV) protein glycogag have been shown to down-regulate SERINC5 expression on cell surfaces. In this paper, the role of SERINC5 in HBV replication was examined. SERINC5 was found to inhibit HBV virion secretion but not affect intracellular core particle-associated DNA or RNA. Furthermore, the group found that SERINC5 decreased the glycosylation levels of the HBV surface antigens (HBsAg) LHB, MHB, and SHB (large, medium, and small). In order to determine the possible role of SERINC proteins in HBV replication, SERINC proteins 1, 3, and 5, were each transfected into cells alongside an HBV expression vector using Lipofectamine 2000. Transfection of SERINC plasmids was performed in a dose-responsive manner and was confirmed using Western blot. Transfected cell supernatants were then analyzed using an ELISA for HBsAg. Cells transfected with SERINC5 showed a reduction of HBsAg in the supernatant with increasing amounts of SERINC5. Extracellular HBsAg levels in cells transfected with SERINC1 or SERINC3 were unaffected. Furthermore, compared to cells transfected with a control vector, cells transfected with SERINC5 had less HBV virion DNA in the supernatant as measured by qPCR following immunoprecipitation with an anti-HBsAg antibody. Those cells transfected with SERINC1 or SERINC3 showed no change in extracellular HBV virion DNA compared to the control. Interestingly, intracellular levels of HBV DNA and HBV RNA as measured by Southern blot and Northern blot respectively, showed no change between cells transfected with the control vector or any of the SERINC proteins. Additionally, siRNA knockdown of SERINC5 in HepG2 cells concomitantly transfected with an HBV expression vector yielded increased secretion of HBsAg as measured by ELISA and HBV viron DNA as measured by qPCR following immunoprecipitation with an anti-HBsAg antibody. Next, in order to understand the mechanism of SERINC5-mediated HBV secretion inhibition, flag-tagged LHB, MHB, or SHB were transfected into HepG2 cells alongside either a plasmid expressing HA-tagged SERINC5 or a control vector. Interestingly, the glycosylated forms of all three HBsAg proteins were reduced in cells co-transfected with SERINC5 as measured by Western blot. The group then found that SERINC5 colocalizes with LHB in the Golgi apparatus. This was accomplished by co-transfecting HepG2 cells with LHB fused to enhanced cyan fluorescent protein (LHB-ECFP) alongside HA-tagged SERINC5. Cells were then subjected to immunofluorescence dual staining with an antibody against HA as well as an antibody against GM130, a resident protein of the Golgi. These three signals overlapped, implying that SERINC5 interacts with LHB in the Golgi. This finding was further validated by co-immunoprecipitation experiments showing the interaction of SERINC5 with LHB, MHB, and SHB. The group also found, using mutagenesis studies that the fourth to sixth domains of SERINC5 are required for inhibition of HBV secretion. These domains are different than those involved in HIV-1 inhibition, and the group has concluded that SERINC5 inhibits HBV by a completely different mechanism than it does HIV-1. While SERINC5 inhibits HIV-1 by inducing conformational changes on the viral envelope, it inhibits HBV secretion by preventing glycosylation of HBsAg. This publication demonstrates that SERINC5 is a potential anti-HBV host factor. Stimulation of SERINC5 may be a possible treatment for chronic HBV and SERINC5 may prove useful as a diagnostic marker if it is found to correlate with HBV viral load and chronicity.

  • Viral hijacking of the TENT4–ZCCHC14 complex protects viral RNAs via mixed tailing – Nature Structural & Molecular Biology

This paper from Seoul National University in South Korea identifies the TENT4-ZCCHC14 complex as a host factor which protects viral messenger RNA (mRNA) transcripts from degradation. Terminal nucleotidyltransferases (TENTs) are noncanonical poly(A) polymerases. These enzymes add many adenine residues as well as occasional non-adenosine residues to the 3′ end of mRNA molecules. TENT4A and TENT4B (also known as PAPD7 and PAPD5) extend mRNA poly(A) tails with the occasional non-adenosine residue which is typically a guanosine. The results are mRNAs bearing “mixed tails”. Deadenylases are enzymes which trim poly(A) tails to initiate mRNA degradation. The carbon catabolite repression 4–negative on TATA-less (CCR4-NOT or CNOT) complex is the main cytoplasmic deadenylase complex. CNOT trims mRNA poly(A) tails, but its activity is hindered when it encounters a guanosine reside. Therefore, mixed tails protect mRNAs from being targeted for degradation. Interestingly, the inhibitor of HBV called DHQ-1 was recently found to interact with TENT4A and TENT4B. The protein called zinc finger CCHC domain-containing protein 14 (ZCCHC14) was previously found to be an essential host factor for HBV surface antigen production in a genome-wide CRISPR screen. This publication demonstrates that ZCCHC14 recognizes a pentaloop motif in the HBV post-transcriptional regulatory element (PRE) of HBV mRNAs and in turn recruits TENT4A or TENT4B which provide the mRNAs with a protective mixed tail. Additionally, it was demonstrated that viral mRNAs of the human cytomegalovirus (HCMV) contain a similar pentaloop motif and also receive protective mixed tails. This group used a method which they developed previously called TAIL-seq. This method allows for sequencing of 3′ tails on mRNAs as well as identification of the transcript. First, total RNA is extracted from cells. Ribosomal RNA (rRNA) is removed using an rRNA depletion kit in which ssDNA probes are specifically bound to rRNA which are then digested by RNase H. Next, a biotinylated adaptor sequence is ligated to the 3′ end of RNAs. A low concentration of RNase T1 is then used to partially digest the transcripts. Next, the RNAs are pulled down, using streptavidin, phosphorylated, and gel purified to obtain fragments which are 500-1000 nucleotides in length. This size fractionation step removes small non-coding RNAs such as tRNA, snRNA, snoRNA, and miRNA. Next, a second adaptor sequence is added to the 5′ end of the mRNAs. Finally, the mRNAs are subjected to next generation sequencing (NGS) on an Illumina HiSeq 2500 platform. Two reads are obtained for each mRNA, one from the 3′ adaptor and one from the 5′ adaptor. Sequence information derived from these reads reveals the specific composition of mRNA poly(A) tails. In this publication, TAIL-seq was employed to investigate viral mRNA tailing. HepG2.2.15 cells which express the HBV genome, as well as human foreskin fibroblasts (HEF) infected with HCMV were subjected to TAIL-seq. mRNA 3′ tails of both viruses were found to be guanylated significantly more than cellular mRNAs. Additionally, viral mRNA 3′ tails were longer than cellular ones, indicating slower net deadenylation. To check the mechanism of viral mixed tailing, the noncanonical poly(A) polymerases TENT4A and TENT4B were knocked down using siRNA. TAIL-seq showed a significant reduction of viral mRNA 3′ tail guanylation in TENT4-knockdown cells. Additionally, the half-lives of HBV mRNAs were shown to decrease in TENT4-knockdown HepG2.2.15 cells as measured by RT-qPCR at intervals following the addition of the transcription blocker actinomycin D. In order to determine how HBV mRNAs recruit TENT4A and TENT4B, formaldehyde-based crosslinking and immunoprecipitation sequencing (fCLIP-seq) was employed on HepG2.2.15 cells. fCLIP-seq reveals what RNA sequences proteins bind to. In fCLIP-seq, formaldehyde is used to crosslink RNA-protein interactions. RNA-protein complexes are then “pulled down” using an antibody and run on a gel. The protein may then be degraded using proteinase K and RNA molecules may be sequenced. RNA sequencing reads from fCLIP-seq of the HBV genome were enriched in lysates pulled down using antibodies against TENT4A or TENT4B compared to input cell lysate and that pulled down using normal mouse IgG. Importantly, the greatest enrichment occurred specifically in the PRE region of HBV mRNAs. The group goes on to show that the sterile alpha motif (SAM) of ZCCHC14 binds to the stem loop  region of the PRE and recruits TENT4 proteins. This publication demonstrates that both HBV and HCMV have taken advantage of host mRNA transcription regulation to prolong transcript half-life. ZCCHC14, TENT4A, and TENT4B may be possible host targets for HBV or HCMV antiviral treatments.

 
  • Hepatitis B Virus DNA is a Substrate for the cGAS/STING Pathway but is not Sensed in Infected Hepatocytes – Viruses   This paper from the Paul Ehrlich Institute in Langen, Germany shows that HBV DNA is sensed by cGAS, but not in natural HBV infection of hepatocytes. Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS), is a pattern recognition receptor (PRR) that senses cytoplasmic double-stranded DNA (dsDNA). In response to dsDNA binding, cGAS catalyzes the production of 2’3′-cGAMP, a cyclic dinucleotide (CDN) which activates stimulator of interferon genes (STING) by direct binding. Once activated, STING signaling results in the activation of transcription factors promoting the production of type I interferons (IFN-I) and proinflammatory cytokines including tumor necrosis factor alpha (TNFα). IFN-I production and secretion lead to the activation of numerous IFN-stimulated genes (ISGs) which induce a robust antiviral state in the cell. The cGAS/STING pathway is a key component of innate immunity, protecting cells from bacterial and viral infections. How viruses interact with host innate immune sensors such as cGAS is important for understanding their pathogenesis. While the innate immune mechanisms activated by HBV infection remain disputed, HBV is largely considered to be a stealth virus in that it bypasses host innate immunity. Some groups have postulated that the HBV X protein (HBx) or HBV polymerase may inhibit innate immune responses. In this publication it is demonstrated that HBV RNAs are not immunostimulatory, however HBV DNA does elicit an innate immune response mediated by the cGAS/STING pathway. In order to test the immunostimmulatory potential of HBV nucleic acids, they were transfected at multiple concentrations into monocyte-derived dendritic cells (MDDCs) generated from primary human peripheral blood mononuclear cells (PBMCs). Following transfection, mRNA of the gene ISG54 was measured by RT-qPCR. ISG54 was selected as the read-out for innate immune signaling because it is a direct target of the transcription factor IRF3 which is activated downstream of both RIG-I (RNA-sensing) and cGAS/STING (DNA-sensing) pathways. HBV nucleic acids were extracted from HBV virions and quantified prior to transfection. Some groups of nucleic acids were subjected to either DNase or RNase digestion, leaving only HBV RNA or DNA respectively. Total HBV nucleic acids stimulated ISG54 transcription in a dose-dependent manner. Similarly, HBV DNA also stimulated ISG54 transcription. However, transfection of HBV RNA alone did not activate ISG54 transcription, implying that only HBV DNA elicits an innate immune response. In order to test which specific innate immune pathway senses HBV DNA, the human monocytic leukemia cell line THP-1 was used. CRISPR/Cas9 genome editing was used in THP-1 cells to knockout (KO) cGAS, STING, or mitochondrial antiviral-signaling protein (MAVS), which is a key node downstream of the RNA-sensing RIG-I-like receptor (RLR) protein family. Transfection with HBV nucleic acids caused a high level of ISG54 transcription in wild type (WT) and MAVS KO cells which was abrogated when HBV nucleic acids were treated with DNase prior to transfection. However, HBV nucleic acids caused no measurable ISG54 transcription in either cGAS KO or STING KO cells. Next, the group wanted to determine if HBV activates the cGAS/STING pathway in its natural infection of hepatocytes. The levels of cGAS, STING, and other PRRs in a panel of cells were determined using RT-qPCR. The hepatocellular carcinoma cell line HepG2 as well as primary human hepatocytes (PHH) were shown to express less cGAS and STING than Kupffer cells, MDDCs, THP-1 cells, or monocyte derived macrophages (MDMs). Next, HepG2 cells expressing the human sodium taurocholate cotransporting polypeptide used for HBV cell entry (HepG2-hNTCP) and PHHs were transfected with HBV nucleic acids. Both hepatocyte types showed a dose-responsive increase in ISG54 transcription when transfected. Finally, HepG2-hNTCP cells and PHHs were infected with HBV and HBV RNA and ISG54 mRNA were quantified by RT-qPCR. Although both cell types were efficiently infected, they showed no induction of ISG54 across several days. These results indicate that although hepatocytes are capable of sensing transfected HBV genomic DNA via cGAS, they are not able to do so in the context of a natural infection. One possible explanation for the failure of hepatocytes to sense HBV nucleic acids is that they are shielded by the viral nucleocapsid upon infection and during the formation of replication intermediates. Another possibility is that the level of HBV nucleic acids in a natural infection is too low to activate cGAS/ STING, given that these proteins are sparse in hepatocytes. This publication demonstrated for the first time that HBV RNAs are not immunostimulatory, while HBV DNAs activate the cGAS/STING pathway. This finding shows that it may be possible to utilize the cGAS/STING pathway in order to eradicate chronic HBV infection. Perhaps small molecules which destabilize HBV nucleocapsids may be used to expose the DNA of intracellular HBV virions, leading to the activation of the cGAS/STING pathway and an innate antiviral response.

Meet our guest blogger, David Schad, B.Sc., Junior Research Fellow at the Baruch S. Blumberg Institute studying programmed cell death such as   apoptosis and necroptosis in the context of hepatitis B infection under the direction of PI Dr. Roshan Thapa. David also mentors high school students from local area schools as part of an after-school program in the new teaching lab at the PA Biotech Center. His passion is learning, teaching and collaborating with others to conduct research to better understand nature.

 

Hepatitis B Research Review: February

 

Welcome to the Hepatitis B Research Review! This monthly blog shares recent scientific findings with members of Baruch S. Blumberg Institute (BSBI) labs and the hepatitis B (HBV) community. Technical articles concerning HBV, Hepatocellular Carcinoma, and STING protein will be highlighted as well as scientific breakthroughs in cancer, immunology, and virology. For each article, a brief synopsis reporting key points is provided as the BSBI does not enjoy the luxury of a library subscription. The hope is to disseminate relevant articles across our labs and the hep B community. 

 Summary: This month, researchers in Beijing, China have reported that a therapeutic vaccine composed of polylactic acid microparticles loaded with HBV surface antigen and the mouse STING agonist DMXAA showed efficacy in clearing HBV infection in a mouse model. Researchers from Wuhan, China have reported that SOX2, a transcription factor important for cell proliferation is also a host restriction factor for HBV infection. Also, researchers from the University of Boulder in conjunction with Dr. James Chen’s lab in Dallas have reported the synthesis of two potent cGAS inhibitors.

The incorporation of cationic property and immunopotentiator in poly (lactic acid) microparticles promoted the immune response against chronic hepatitis B – Journal of Controlled Release

This paper from the Chinese Academy of Sciences in Beijing, introduces a microparticle vaccine which may be used to treat chronic HBV infection (CHB). The 1μm diameter microparticle is made from polylactic acid (PLA), which is a biodegradable polymer typically synthesized from plant starch. The microparticle also contains didodecyldimethylammonium bromide (DDAB) which is a double-chain cationic surfactant. This group has previously shown that DDAB may be used as a carrier for the HBV surface protein (HBsAg). DDAB also gives the microparticle a positive charge, which accelerates its phagocytosis into antigen-presenting cells (APCs) and facilitates its escape from lysosomal degradation once in the cell. Additionally, the group loaded microparticles with the mouse STING agonist  5,6-dimethylxanthenone-4-acetic acid (DMXAA). The microparticles were refereed to as DDAB-PLA (DP) and DDAB-PLA-DMXAA (DP-D) respectively. Both types of microparticle were saturated with HBV surface antigen (HBsAg). The microparticles were first tested on mouse bone marrow dendritic cells (BMDCs). Administration of microparticles caused less than a 20% reduction of cell viability in these cultures. BMDCs treated with DP-D microparticles had at least ten-fold more expression of IRF-7 and IFN-β mRNA as measured by RT-qPCR than those treated with HBsAg or DP microparticles alone. Surprisingly, the DP-D microparticle-treated cells also had about twice the expression of these genes compared to the positive control HBsAg + DMXAA, which contained ten times more DMXAA than the microparticles. This indicates that the DP-D microparticles induced the STING pathway with high efficiency due to their bioavailability. Next, the group found that DP-D microparticles induced the highest level of chemokine expression (measured via RT-qPCR) and immune cell recruitment (measured via flow cytometry) at the site of injection in inoculated mice compared with HBsAg alone, HBsAg with aluminum salts (traditional vaccine adjuvant), and DP microparticles. This result shows that the DP-D microparticles induced both an innate immune response and an adaptive immune response in mice. Further, the group showed that BMDCs treated with DP-D microparticles had a high level of maturation, expressing CD40, CD86, and MHCII molecules on their surface as measured by flow cytometry. Finally, the group administered the HBsAg-primed microparticles to mice infected with recombinant HBV (rAAV-1.3HBV virus, serotype ayw). Mice treated with both types of microparticles showed a higher cytokine response as well as a higher titer of anti-HBsAg antibody as measured by ELISA. Mice treated with the DP-D microparticles had the most profound immune cell activation and  fastest clearance of serum HBsAg. The microparticle vaccine introduced in this publication is promising because it is highly efficient in delivering antigen to immune cells. The microparticles are unique in that they contain a small molecule STING agonist inside. This design is clever because this vaccine stimulates the innate immune system by activating STING and the adaptive immune system by displaying HBsAg to APCs. This promotes HBV clearance in a multifaceted approach: immune cells produce cytokines through the STING pathway, T cells recognize and destroy infected cells, and B cells secrete anti-HBsAg antibodies to neutralize newly formed viruses. This publication highlights the versatility of biodegradable microparticle technology in designing unique approaches to combat infection. Micro- and nanoparticle delivery systems represent a promising avenue for future drugs to combat HBV and other viruses.

SOX2 Represses Hepatitis B Virus Replication by Binding to the Viral EnhII/Cp and Inhibiting the Promoter Activation – Viruses
This paper from Wuhan University in China identifies the protein sex determining region Y box 2 (SOX2) as a host factor that restricts HBV replication. SOX2 is a transcription factor critical for cell proliferation and the tumorigenecity of solid tumors. In 2006, expression of SOX2 along with three other transcription factors was shown to convert somatic cells into induced pluripotent stem cells. Overexpression of SOX2 indicates poor prognosis in patients undergoing resection of HCC. In HCC cells, SOX2 has also been found to induce the expression of programmed death ligand-1 (PD-L1), leading to the tumor’s evasion of the host immune system. Previously, it has been demonstrated that HBV infection induces increased expression of SOX2 in hepatocytes. This study demonstrates that SOX2 inhibits HBV replication by binding to the Enhancer II (EnhII) and Core Promoter (Cp) regions of the HBV genome. By binding to the EnhII/Cp region, SOX2 disrupts the transcription of the mRNA species precore, core, polymerase, and pgRNA. This reduction of mRNA transcription results in reduced levels of core-associated DNA, HBV surface antigen (HBsAg), and HBV e antigen (HBeAg). To learn this, the group co-transfected both HepG2 and Huh7 cells with a fixed concentration of  HBV 1.3-mer plasmid DNA alongside variable concentrations of Flag-tagged SOX2 in pcDNA3.1 plasmid DNA. Cells transfected with higher concentrations of SOX2 plasmid DNA showed reduced levels of HBV mRNAs (3.5, 2.4, and 2.1 kb) via Northern blotting. SOX2-transfected cells also showed reduced levels of HBV core-associated DNA via qPCR as well as reduced levels of both HBsAg and HBeAg via ELISA. Next, in order to learn  if SOX2 interacts directly with an HBV promoter, a dual-luciferase reporter assay was implemented. Here, four vectors were used, each containing one of the HBV enhancer and/or promoter sequences (preS1, preS2, EnhⅡ/Cp, and EnhⅠ/Xp) upstream of a firefly luciferase reporter. Each of these firefly luciferase reporter vectors were co-transfected into HepG2 cells alongside variable concentrations of SOX2 plasmid DNA. A plasmid encoding Renilla luciferase was also included at a constant concentration in each transfection as a control for transfection efficiency. While firefly luciferase has an emission of 625 nm (red), Renilla luciferase has an emission of 525 nm (green). Therefore, levels of red fluorescence were used to measure the activity of the HBV enhancer/promoter sequences and levels of green fluorescence were utilized as a control for transfection efficiency. Co-transfection with SOX2 significantly diminished the luciferase activity of the EnhII/Cp reporter only and in a dose-responsive manner, indicating its interaction with that region of the HBV genome. Further, using HBV-producing HepAD38 cells, chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) was used to isolate SOX2 protein and then determine what DNA sequence it was bound to. The EnhII/Cp sequence was found to be highly enriched on SOX2 protein. In order to determine which part of the SOX2 protein is required for binding to the EnhII/Cp region, truncated forms of SOX2 were generated in the pcDNA3.1 plasmid. Using the assays described above, it was found that only SOX2 mutants lacking the high mobility group (HMG) domain were unable to bind to the EnhII/Cp region and suppress HBV products. Interestingly, it was found that SOX2 mutants lacking the transcription activation (TA) domain were still able to bind to the EnhII/Cp region. Further, it was demonstrated by Western blot of subcellular fractions and immunofluorescence that SOX2 mutants lacking the HMG domain were unable to enter the nucleus. Finally, studies were performed in an in vivo BALB/c mouse model. Mice were given a hydrodynamic injection of an adeno-associated viral vector conferring HBV (pAAV-HBV1.3) alongside pcDNA3.1 plasmid DNA conferring SOX, SOX2 lacking HMG domain ( SOXΔHMG), or empty vector. Levels of HBsAG and HBeAg in the blood at days two and four were reduced only in mice given the full length SOX2 plasmid. Additionally, mice given the full length SOX2 plasmid had a reduction of 3.5kb HBV mRNA in liver tissues as measured by qPCR and a lower abundance of HBV core antigen (HBcAg) in liver tissues as measured by immunohistochemical staining. This study shows that SOX2 protein, previously shown to be upregulated by HBV, plays an anti-HBV role in the liver. SOX2 is therefore a new host restriction factor of HBV replication. SOX2 may be one protein which contributes to HBV-induced hepatocarcinogenesis, given its role in promoting the transcription of genes involved in cell proliferation. In the future, SOX2 may be utilized for its anti-HBV activity or targeted for the treatment of HCC.

 Discovery of Small Molecule Cyclic GMP-AMP Synthase Inhibitors – The Journal of Organic Chemistry

This paper from the University of Colorado Boulder introduces the development of novel small molecule inhibitors of the protein cyclic GMP-AMP synthase (cGAS). This publication is in conjunction with Dr. James Chen’s laboratory at the University of Texas Southwestern Medical Center in Dallas, Texas. Dr. Chen’s lab discovered cGAS in 2012. cGAS is a cytosolic, double-stranded DNA (dsDNA)-sensing protein. It belongs to the nucleotidyltransferase family of enzymes which transfer nucleoside monophosphates, the substituents of nucleic acids. When cGAS recognizes dsDNA, it synthesizes the cyclic dinucleotide cyclic GMP-AMP (cGAMP). cGAMP acts as a second messenger and activates the stimulator of interferon genes protein (STING). Once activated, STING triggers TBK1- and IKK-mediated activation of the transcription factors interferon regulatory factor 3 (IRF3) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB). In the nucleus, IRF3 and NF-kB induce the expression of type I interferons and other inflammatory cytokines. cGAS is essential for detecting foreign pathogens which contain dsDNA and triggering an innate immune response to clear them. However, excessive or dysfunctional cGAS activity may lead to chronic inflammation and/or autoimmunity. Pharmacologic inhibition of cGAS may provide treatments for diseases including Aicardi-Goutiés syndrome (AGS), lupus erythematosus, and cancer. Current small molecule inhibitors of cGAS are limited by poor specificity and/or cellular activity. In this study, a high throughput virtual screen (HTVS) was utilized to screen about 1.75 million drug-like compounds for activity against the dimer-forming and DNA-binding faces of mouse cGAS (mcGAS). mcGAS was utilized for the in silico screen because the human cGAS (hcGAS)-DNA complex was only recently published. From this virtual screen, ten compounds were further investigated, leading to the selection of one lead compound. This lead was further optimized for greater potency through chemical modifications resulting in the analogues CU-32 and CU-76. The IC50 of both compounds is below 1µM. To test these compounds’ selectivity for cGAS, human monocyte cells THP-1 were either transfected with  interferon-stimulatory DNA (ISD) or infected with Sendai virus (SeV). ISD is a 45-basepair DNA known to activate cGAS, while SeV is a single-stranded RNA (ssRNA) virus known to activate the RIG-I-MAVS pathway; both stimuli are known to result in IRF3 activation and dimerization. Following treatment with both compounds, Western blot of the cells was conducted probing for the formation of IRF3 dimers. In ISD-treated cells, CU-32 and CU-76 inhibited the formation of IRF3 dimers in a dose responsive manner. Neither compound had any effect on IRF3 dimer formation in SeV-infected cells. This result indicates that these inhibitors are selective to cGAS. Using in silico molecular docking studies, the group speculates that these compounds disrupt the interface of the cGAS dimer, allosterically inhibiting dimerization. The discovery of novel cGAS inhibitors is exciting and important for multiple reasons. These compounds, if made commercially available will allow for improved experimentation investigating the cGAS/STING pathway. If these compounds or their derivatives are found to be safe and effective in humans, they may be promising candidates for the treatment of autoimmune disorders or cancer.

 

Meet our guest blogger, David Schad, B.Sc., Junior Research Fellow at the Baruch S. Blumberg Institute studying programmed cell death such as apoptosis and necroptosis in the context of hepatitis B infection under the direction of PI Dr. Roshan Thapa. David also mentors high school students from local area schools as part of an after-school program in the new teaching lab at the PA Biotech Center. His passion is learning, teaching and collaborating with others to conduct research to better understand nature.

 

We Will No Longer Be Invisible

The Hepatitis B Foundation and the Hep B United coalition are excited to partner with the All of Us Research Program, a program funded by the National Institutes of Health (NIH) to advance precision medicine – health care that is tailored to each person. All of Us will enroll and engage 1 million or more people across the country, from all walks of life, to contribute to research that could improve health for generations to come.

We are partnering with All of Us to increase representation of Asian American and Pacific Islander communities in biomedical research. Diversity and inclusion in health research is critical to understanding how certain diseases or treatments affect individuals differently and helping transform health care to be more customized and effective for each person.

In the U.S., over half of the 2.2 million people living with chronic hepatitis B are Asian Americans and Pacific Islanders. Join All of Us to help researchers better understand the causes and risk factors for chronic conditions like hepatitis B and make health equity a reality.

Visit JoinAllofUs.org to learn more about the All of Us Research Program.

Additional resources:

Fact Sheet: All of Us Research Program 

Infographic: All of Us Research Program 

Flyer : How do I sign up for this research program?

Nearly 1 in 4 Romanians with Hepatitis B also Infected with Hepatitis D

 

By Sierra Pellechio, Hepatitis Delta Connect Coordinator

Since the 1990’s most of Eastern Europe has seen a decline in the prevalence of hepatitis D, a dangerous coinfection of hepatitis B, attributed to successful vaccination programs and government prioritization. Romania, which has the highest hepatitis B prevalence in the EU, has not seen such declines of hepatitis D, which affects 23% of its hepatitis B patients. Hepatitis D coinfection is considered hyperendemic to the country, and has some of the highest rates of coinfection globally1. Seventy percent of these 200,000 patients will progress to cirrhosis, often within only 10  years2, and face barriers to receiving effective treatment and management. Although the country enacted a national hepatitis B vaccination program for all newborns in 1995 and a catch-up program for school-age children in 1999, older populations already infected with hepatitis B and inadequately immunized young people represent susceptible groups for coinfection with hepatitis B and disease.1,3. Additionally; lack of hepatitis B vaccination recommendations for high risk groups, low implementation of hepatitis B screening during pregnancy, supply shortages and vaccine hesitancy, have created opportunities for hepatitis B and D transmission. Exposure to infected blood or sexual fluids through blood transfusions or surgeries (before the 1990’s), tattoos, piercings, injection drug use, or sexual contact with an infected person, can expose people already living with hepatitis B to hepatitis D, or expose those who have not received the full hepatitis B vaccine series to both viruses. Control of hepatitis B and D coinfection has also been hindered by the lack of a national registry and surveillance system thus preventing an understanding of the accurate prevalence and public health burden1.

With health expenditure and life expectancy the lowest in the EU, Romania is battling large system-wide failures that have fostered the persistence of hepatitis B and D in its population5.

Dr. Florin Caruntu, of the National Institute of Infectious Diseases in Bucharest, has suggested that there is a general low level of awareness and screening among health care providers in Romania, which has led to late diagnoses and cost many patient lives. For patients who are diagnosed, investigational testing is not covered by the national insurance house, placing a financial burden on patients to pay out of pocket for the additional testing necessary to manage their coinfection. With pegylated interferon injections as the only semi-effective treatment option, even diagnosed patients struggle to effectively control their coinfection and even less are connected to clinical trials. Although there are 7 new drugs in clinical trials, progress has lagged behind patient need for new therapies, many of whom are living with cirrhosis.

Increased government investment in the healthcare system, including medical training and education programs for provider awareness, updated protocols and coverage of investigational testing, would pave the way for increased patient identification and navigation to successful care. As clinical trials continue to progress, it is critical that Romania be a top consideration for clinical trial sites, as patients anxiously await more effective treatment options.

For more information on HDV in Romania, please watch our webinar featuring expert speaker, Dr. Florin Caruntu, of the National Institute of Infectious Diseases in Bucharest, Romania.

For more information about hepatitis B/D coinfection and the Hepatitis Delta Connect program, please visit www.hepdconnect.org or email us at connect@hepdconnect.org. If you are a hepatitis delta patient, and wish to receive information about upcoming clinical trials, please enter your information here. Hepatitis Delta Connect seeks to provide information, resources and support for hepatitis B/D patients and their families through its website, social media, fact sheets, webinars  and hepatitis D liver specialist directory.

1. Hepatitis delta virus infection in Romania: Prevalence and risk factors. (2015). Journal of Gastrointestinal and Liver Diseases, 24(4) doi:10.15403/jgld.2014.1121.244.dtv

2. Noureddin, M., & Gish, R. (2014). Hepatitis delta: Epidemiology, diagnosis and management 36 Years after discovery. Current Gastroenterology Reports, 16(1), 1-8. doi:10.1007/s11894-013-0365-x

3. Ruta, S. M., Matusa, R. F., Sultana, C., Manolescu, L., Kozinetz, C. A., Kline, M. W., & Cernescu, C. (2005). High prevalence of hepatitis B virus markers in Romanian adolescents with human immunodeficiency virus infection. Journal of the International AIDS Society, 7(1), 68-68. doi:10.1186/1758-2652-7-1-68

4. Gheorghe, L., Csiki, I. E., Iacob, S., & Gheorghe, C. (2013). The prevalence and risk factors of hepatitis B virus infection in an adult population in Romania: A nationwide survey. European Journal of Gastroenterology & Hepatology, 25(1), 56.

5. OECD/European Observatory on Health Systems and Policies (2017), Romania: Country Health Profile 2017, State of Health in the EU,OECD Publishing, Paris/European Observatory on Health Systems and Policies, Brussels. http://dx.doi.org/10.1787/9789264283534-en

 

Where is Hepatitis D? High Prevalence of Hepatitis B/D Coinfection in Central Africa

By Sierra Pellechio, Hepatitis Delta Connect Coordinator

While hepatitis B is known to be highly endemic to sub-Saharan Africa and is estimated to affect 5-20% of the general population, the burden of hepatitis D, a dangerous coinfection of hepatitis B, has largely been left undescribed. Since the virus’s discovery 40 years ago, Africa has faced structural barriers that have contributed to the ongoing prevalence of the virus in this region. Widespread instability, under-resourced health systems, and poor surveillance have contributed to inadequate research and a lack of understanding about the health burden of hepatitis D on hepatitis B patients, particularly in Central Africa.

New data, however, reveals pockets of hepatitis B/D coinfection in this region, particularly in countries such as Cameroon, Central African Republic and Gabon. In a recently published study of nearly 2,000 hepatitis B infected blood samples from 2010-2016 in Cameroon, 46.7% tested positive for hepatitis D antibodies, a marker of past or current hepatitis D coinfection. Another study of 233 chronic hepatitis B carriers from 2008-2009 found a 17.6% positivity for hepatitis D antibodies. Other small studies from the Central African Republic have revealed 68.2% prevalence in hepatitis B patients, 50% coinfection in liver cancer patients and an 18.8% coinfection in hepatitis B infected pregnant women. Not only are new studies revealing evidence that there are groups at higher risk for hepatitis D, but a 2008 study on 124 community members in Gabon found 66% of them had markers for hepatitis D, proving this virus can also be circulating in the general population. Globally, hepatitis D is thought to affect about 5-10% of hepatitis B patients, making Central Africa an area of extremely high prevalence.

A diagnosis with hepatitis B and D can increase the risk for cirrhosis and liver cancer by nearly three times, and with only one available treatment, the future for coinfected patients if often uncertain. Although hepatitis B and D can be safely prevented by completing the hepatitis B vaccine series, which is available in many countries throughout Africa, the birth dose of the hepatitis B vaccine is often not given within the recommended 24 hours of birth. Lack of awareness, availability, and high cost mean many infants will not begin the vaccine series until 6 weeks of age, creating a window for exposure to hepatitis B. Greater than 95% of babies infected with hepatitis B will go on to develop chronic hepatitis B infections, leaving them susceptible to a future hepatitis D infection. Spread the same way as hepatitis B, through direct contact with infected blood and sexual fluids, hepatitis D can be contracted through unsterile medical and dental equipment and procedures, blood transfusions, shared razors and unprotected sex. Although the severity of disease varies greatly by hepatitis D genotype, coinfection always requires expert management by a knowledgeable liver specialist, which are often difficult to find.

As an increasing number of studies continue to describe the widespread endemicity of hepatitis B/D coinfection and its public health burden, researchers and the Hepatitis Delta International Network are calling on the World Health Organization (WHO) to declare hepatitis D a “threat” in this region in order to promote increased priority and awareness. Addressing hepatitis B/D coinfection prevention and management will be complex and require a multi-pronged approach through methods such as government prioritization, increased funding for health systems, hepatitis B vaccination awareness programs, birth dose prioritization, better sterilization techniques in hospitals, clinics, and barbers, and public awareness of the disease.

For more information about hepatitis B/D coinfection and the Hepatitis Delta Connect program, please visit www.hepdconnect.org or email us at connect@hepdconnect.org. Hepatitis Delta Connect seeks to provide information, resources and support for hepatitis B/D patients and their families through its website, social media, fact sheets, webinars and hepatitis D liver specialist directory.

Is a Cure for Hepatitis B Coming? Experts Say Yes

How far are we from finding a cure for hepatitis B? We are close, said Timothy Block, PhD, president and co-founder of the Hepatitis B Foundation and its research arm, the Baruch S. Blumberg Institute. He points out that hepatitis C, once thought to be incurable, is today cured with new combination treatments.

Image courtesy of suphakit73 at FreeDigitalPhotos.net.
Image courtesy of suphakit73 at FreeDigitalPhotos.net.

Experts believe a cure for hepatitis B will also soon be developed. And the need for a cure has never been greater, with more than 240 million people worldwide living with chronic hepatitis B, causing 1 million deaths per year from related liver failure and liver cancer.

“Treatments are available,” explained Block, “but we have become a little too comfortable with the medications that are currently approved for use.” While these drugs are effective, interferon has many side effects and daily antivirals require lifelong use. These drugs work in only half of the infected population and reduce death rates by only about 40 to 70 percent.

What will a cure look like?

The available antivirals are similar and combining them offers no advantage. They have limited effectiveness against cccDNA, the seemingly indestructible “mini-chromosome” of the hepatitis B virus that continues to produce virus particles in infected liver cells, even in people being treated. A cure, therefore, would have to destroy or silence cccDNA and provide long-term immunity. Because one-drug treatments can lead to drug resistance, a cure would almost certainly involve combination therapy, similar to hepatitis C. Continue reading "Is a Cure for Hepatitis B Coming? Experts Say Yes"

Can People with HBeAg-Negative Hepatitis B Ever Stop Taking Antivirals?

Image courtesy of rakratchada torsap, at FreeDigitalPhotos.net.
Image courtesy of rakratchada torsap, at FreeDigitalPhotos.net.

Medical guidelines suggest that individuals with HBeAg-negative hepatitis B with signs of liver damage face an “indefinite” or even lifetime commitment to taking daily antiviral pills.

In this week’s blog, we explore when—if ever—individuals with hard-to-treat HBeAg-negative hepatitis B can ever stop taking antivirals.

First of all, what is HBeAg-negative hepatitis B? Many people infected with hepatitis B at birth and who remain infected into their 40s, 50s or 60s, develop HBeAg-negative hepatitis B. Researchers believe that over time the virus mutates to evade the immune system. Though individuals may have lost the hepatitis B “e” antigen (HBeAg) and developed the “e” antibody, this mutated virus develops the ability to keep replicating despite the loss of HBeAg. And this mutated virus is capable of putting people at higher risk of liver damage.

Generally, doctors recommend treatment to HBeAg-negative patients when their viral load exceeds 2,000 IU/ML and their ALT liver enzyme levels, which rise when liver cells are damaged, are even moderately elevated. (Normal ALT levels are less than 30 for men and 19 for women.)

The most common antiviral treatments are either entecavir (Baraclude) or tenofovir (Viread). These two are considered the most powerful at quickly reducing viral load (HBV DNA) and have a very low risk of causing drug resistance, which is critical considering the long-term treatment required by HBeAg-negative patients.

But can individuals with HBeAg-negative hepatitis B ever stop treatment? Antivirals are expensive, without insurance tenofovir costs about $1,000 a month and generic entecavir costs about $407 in the U.S. Additionally, long-term antiviral treatment can cause bone loss.

Late last year, hepatitis B experts with the American Association for the Study of Liver Disease (AASLD) tackled this question and reviewed recent studies that followed HBeAg-negative hepatitis B patients who stopped antivirals. They found that even when these patients enjoyed two years of undetectable viral load and normal ALT levels during treatment, when they stopped only half of them were able to maintain a low viral low (below 2,000 IU/mL) and normal ALT levels.

The risk of dangerous “flares” after stopping treatment, “requires careful weighing of potential for harm and benefit,” the experts wrote. This is important because many HBeAg-negative patients are older and more vulnerable to liver damage and cancer.

In their new recommendations, AASLD experts make clear their findings are “conditional” and the quality of evidence found in the studies they reviewed is “low.” However, this is what they tentatively recommend:

  • Stopping treatment, “may be considered in persons who have (lost) the hepatitis B surface antigen (HBsAg). However, there is currently insufficient evidence to definitively guide treatment decisions for such persons.”
  • And, anyone who stops antiviral therapy should be monitored every three months for at least one year to see if their viral load rebounds or if they have signs of liver damage, including ALT flares.

Given the knowledge-gap about the long-term health consequences of HBeAg-negative hepatitis B, more research with longer durations of monitoring are needed, experts recommended. “Alternative treatment strategies for patients on long-term antiviral therapy, such as adding or switching to (pegylated interferon), warrant further study,” they concluded.

 

There’s Hope for a Hepatitis B Cure at the HEP DART 2015 Conference

IMG_1387This year’s  HEP DART conference brought together liver specialists and researchers from around the world to review and brainstorm about the latest research to find a cure for hepatitis B.

Biopharmaceutical companies presented data that showed their cutting-edge treatments, which use micro-RNAs and other innovative approaches to reduce the virus, appear promising. Much of this research, however, is in early, pre-clinical stages and focuses on laboratory-grown liver cells or laboratory animals, though a few are in Phase I and Phase II trials.

Joan Block, co-founder and executive director of the Hepatitis B Foundation, reported the following news in hepatitis B research from the conference, which was held in Hawaii from Dec. 6-10.

HepDart 2015 marks the 20th anniversary of this conference, and about 600 attendees from 20 countries attended. In opening remarks, Dr. Patrick Marcellin of France noted that the cure for hepatitis C is a huge medical breakthrough, now, he noted we are faced with finding a cure for hepatitis B.

This year’s HepDart meeting included nearly two days devoted to hepatitis B drug development—which shows the new momentum around finding a cure hepatitis B by the scientific community. During previous HepDart meetings, there was almost no discussion about new hepatitis B treatment. But this year, there are more than five companies presenting new hepatitis B drug findings, Block reported.

Researchers at the conference continued to lament the lack of resources spent to research and develop a cure for hepatitis B. They noted the U.S. government has spent $17.5 billion treating HIV. A fraction of that has been spent on finding cures for hepatitis B and C, which infects up to 6 million Americans.

Despite the lack of financial investment in finding a cure, Joan Block reports that the consensus at the conference is that a cure is indeed possible. Despite barriers to achieving a cure because of the complexity of the hepatitis B virus, “the feeling is that there are many targets in the life cycle of the virus and that a combination of a direct-acting antiviral along with an immunomodulator (to boost the immune system) will be the most likely route to success,” she reported.

In the short term, experts may be looking at a “functional” cure. For example, some of the new experimental drugs appear to increase the chances of clearing the hepatitis B surface antigen (HBsAg) with a finite duration of treatment. “Although this wouldn’t take care of (lingering) cccDNA or viral integration into liver cells, it would be a significant advance in treatment,” she said.

Day 2 of HepDart focused on targets within the virus, new therapies and possible cures. Experts explored whether any of the new drugs could produce a functional cure (similar to a resolved hepatitis B infection with loss of surface antigen) versus producing a complete cure that totally eradicates the virus from the liver (including cccDNA). Loss of cccDNA is referred to as the holy grail of the HBV cure.

“The parsing of the word ‘cure’ is frustrating to patient advocates,” she reported, “but the feeling is that the hepatitis B virus life cycle is very complex so an incremental or functional approach might be most feasible.

“Everyone wants a complete cure, including the scientists working on hepatitis B,” she noted, “however, a functional cure might be the most realistic goal in the next 10 years.”

A functional cure means patients will have to take one of the new drugs for only a limited period of time–compared to the current long-term reliance on antivirals that patients take in order to keep their viral loads down and prevent liver damage.

The downside of a functional cure is the potential for reactivation if a person, later in life, needs to take immune-suppressing drugs, such as chemotherapy, to fight cancer. However, this can be managed with antivirals if necessary. This is a similar situation to those who spontaneously recover from an infection.

To underscore the complexity of finding a cure, the image below shows the different targets in the hepatitis B virus life cycle that companies are examining to find a cure.

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There are many promising targets that are being pursued by scientists in academia, NIH, biotech companies and the Hepatitis B Foundation. At this point, the small interfering RNA (siRNA) technology is most advanced. However there are compounds in the pipeline for each category (see below), which is very exciting. Please refer to the Hepatitis B Foundation’s Drug Watch Page for complete list of drugs in development.

“The research work continues,” Joan Block reported, “and there is reason for optimism.”

Dr. Marion Peters - HepDart 2015
Dr. Marion Peters – HepDart 2015

The Hepatitis B Foundation president, Dr. Tim Block chaired a special session at HepDART to discuss what new endpoints will be needed to evaluate the efficacy of the new drugs coming down the pipeline. This will include immunological, virologic, and clinical endpoints for both a functional cure and complete cure.  The clinical endpoint goals might differ based on the phase (immune tolerant, immune active and inactive phase) the patient is in at the time of treatment with these newer agents.

HBF president, Dr. Tim Block
HBF president, Dr. Tim Block

Late breaking update from HepDART!

  • Arrowhead’s hepatitis B surface antigen (HBsAg)-lowering drug (ARC 520) looks promising according to the company’s presentation at HepDart. A single injection of the siRNA first in class type drug lowered HBsAg 10-fold in hepatitis B “e” antigen (HBeAg) positive people. The study was small (a few individuals) but impressive.
  • Arrowhead’s ARC 520 may also be telling us something about chronic HBeAg-positive hepatitis B versus HBeAg-negative hepatitis B. They suggest that the amount of HBsAg in the blood of people with HBeAg-negative hepatitis B may come from “integrated” hepatitis B in the liver, not from “cccDNA.”  This has profound implications for treatment.
  • Novira’s oral drug is a first-in-class capisd inhibitor and was able to lower HBV DNA levels by as much as 100-fold in the small number of people in the initial human trial, according to their presentation at HepDart. Novira was recently acquired by the pharma giant J&J.

“Excitement is really building as the first new hepatitis B drugs come into the clinic,” said Joan Block.

New Hepatitis B Treatment Guidelines Revealed at AASLD 2015 Conference

IMG_1369

The American Association for the Study of Liver Disease (AASLD), the organization that defines how doctors should treat hepatitis B and other liver ailments, unveiled new hepatitis B treatment guidelines this week at its annual conference in San Francisco.

The new guidelines are published here.  Patients should review them and discuss any updates that address their individual conditions with their physicians. Continue reading "New Hepatitis B Treatment Guidelines Revealed at AASLD 2015 Conference"

HBV Journal Review – June 2015

ChrisKHBF is pleased to connect our blog readers to Christine Kukka’s monthly HBV Journal Review that she writes for the HBV Advocate. The journal presents the
 latest in hepatitis B research, treatment, and prevention from recent academic and medical journals. This month, the following topics are explored:

  • HBV Liver Cancer Requires Aggressive Treatment from the Start
  • Experts: Treat Cirrhotic Patients, Even if Viral Load Is Low
  • Some Patients Can Safely Stop Antiviral After Four Years
  • Tenofovir Safe and Effective in Pregnant Women with Drug Resistance
  • Researchers Discover Why Children Become Chronically Infected
  • Expert Recommends Treatment for Mental Confusion from Cirrhosis
  • Antivirals Increase Survival After Liver Cancer Treatment
  • HBV Patients with Diabetes Have a Higher Risk of Liver Cancer
  • Long-term Antiviral Use Increases Hip Fracture Rates Slightly
  • Second Vaccine Series May Be Needed for Children with Celiac Disease
  • Researchers Find HBV B Strain in Cuba Did Not Come from Africa

Continue reading "HBV Journal Review – June 2015"