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John M Taylor - One of the best experts on this subject based on the ideXlab platform.
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pathogenesis by subviral agents viroids and Hepatitis Delta Virus
Current Opinion in Virology, 2016Co-Authors: Ricardo Flores, Robert A Owens, John M TaylorAbstract:The viroids of plants are the simplest known infectious genetic elements. They have RNA genomes of up to 400 nucleotides in length and no protein encoding capacity. Hepatitis Delta Virus (HDV), an infectious agent found only in humans co-infected with Hepatitis B Virus (HBV), is just slightly more complex, with an RNA genome of about 1700 nucleotides, and the ability to express just one small protein. Viroid and HDV RNAs share several features that include circular structure, compact folding, and replication via a rolling-circle mechanism. Both agents were detected because of their obvious pathogenic effects. Their simplicity demands a greater need than conventional RNA or DNA Viruses to redirect host components for facilitating their infectious cycle, a need that directly and indirectly incites pathogenic effects. The mechanisms by which these pathogenic effects are produced are the topic of this review. In this context, RNA silencing mediates certain aspects of viroid pathogenesis.
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intrinsic disorder and oligomerization of the Hepatitis Delta Virus antigen
Virology, 2010Co-Authors: Carolina Alves, Hong Cheng, Heinrich Roder, John M TaylorAbstract:The 195 amino acid basic protein (δAg) of Hepatitis Delta Virus (HDV) is essential for replication of the HDV RNA genome. Numerous properties have been mapped to full-length δAg and attempts made to link these to secondary, tertiary and quaternary structures. Here, for the full-size δAg, extensive intrinsic disorder was predicted using PONDR-FIT, a meta-predictor of intrinsic disorder, and evidenced by circular dichroism measurements. Most δAg amino acids are in disordered configurations with no more than 30% adopting an α-helical structure. In addition, dynamic light scattering studies indicated that purified δAg assembled into structures of as large as dodecamers. Cross-linking followed by denaturing polyacrylamide gel electrophoresis revealed hexamers to octamers for this purified δAg and at least this size for δAg found in Virus-like particles. Oligomers of purified δAg were resistant to elevated NaCl and urea concentrations, and bound without specificity to RNA and single- and double-stranded DNAs.
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primary human hepatocytes are susceptible to infection by Hepatitis Delta Virus assembled with envelope proteins of woodchuck Hepatitis Virus
Journal of Virology, 2008Co-Authors: Severin O Gudima, William S. Mason, Yiping He, Ning Chai, Volker Bruss, Stephan Urban, John M TaylorAbstract:Hepatitis B Virus (HBV) and Hepatitis Delta Virus (HDV) share the HBV envelope proteins. When woodchucks chronically infected with woodchuck Hepatitis Virus (WHV) are superinfected with HDV, they produce HDV with a WHV envelope, wHDV. Several lines of evidence are provided that wHDV infects not only cultured primary woodchuck hepatocytes (PWH) but also primary human hepatocytes (PHH). Surprisingly, HBV-enveloped HDV (hHDV) and wHDV infected PHH with comparable efficiencies; however, hHDV did not infect PWH. The basis for these host range specificities was investigated using as inhibitors peptides bearing species-specific pre-S (where S is the small envelope protein) sequences. It was found that pre-S1 contributed to the ability of wHDV to infect both PHH and PWH. In addition, the inability of hHDV to infect PWH was not overcome using a chimeric form of hHDV containing WHV S protein, again supporting the essential role of pre-S1 in infection of target cells. One interpretation of these data is that host range specificity of HDV is determined entirely by pre-S1 and that the WHV and HBV pre-S1 proteins recognize different receptors on PHH.
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replication of the human Hepatitis Delta Virus genome is initiated in mouse hepatocytes following intravenous injection of naked dna or rna sequences
Journal of Virology, 2001Co-Authors: Jinhong Chang, Luis J Sigal, Anthony Lerro, John M TaylorAbstract:As early as 5 days after DNA copies of the Hepatitis Delta Virus (HDV) genome or even in vitro -transcribed HDV RNA sequences were injected into the mouse tail vein using the hydrodynamics-based transfection procedure of F. Liu et al. (Gene Ther. 6:1258–1266, 1999), it was possible to detect in the liver by Northern analyses of RNA, immunoblots of protein, and immunostaining of liver sections what were considered typical features of HDV genome replication. This transfection strategy should have valuable applications for in vivo studies of HDV replication and pathogenesis and may also be useful for studies of other hepatotropic Viruses.
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unique properties of the large antigen of Hepatitis Delta Virus
Journal of Virology, 1999Co-Authors: Gloria Moraleda, James C Otto, Steven H Seeholzer, V V Bichko, Roland L Dunbrack, John M TaylorAbstract:The large form of the Hepatitis Delta Virus (HDV) protein (L) can be isoprenylated near its C terminus, and this modification is considered essential for particle assembly. Using gel electrophoresis, we separated L into two species of similar mobilities. The slower species could be labeled by the incorporation of [(14)C]mevalonolactone and is interpreted to be isoprenylated L (L(i)). In serum particles, infected liver, transfected cells, and assembled particles, 25 to 85% of L was isoprenylated. Isoprenylation was also demonstrated by (14)C incorporation in vitro with a rabbit reticulocyte coupled transcription-translation system. However, the species obtained migrated even slower than that detected by labeling in vivo. Next, in studies of HDV particle assembly in the presence of the surface proteins of human Hepatitis B Virus, we observed the following. (i) Relative to L, L(i) was preferentially assembled into Virus-like particles. (ii) L(i) could coassemble the unmodified L and the small Delta protein, S. (iii) In contrast, a form of L with a deletion in the dimerization domain was both isoprenylated and assembled, but it could not support the coassembly of S. Finally, to test the expectation that the isoprenylation of L would increase its hydrophobicity, we applied a phase separation strategy based on micelle formation with the nonionic detergent Triton X-114. We showed the following. (i) The unique C-terminal 19 amino acids present on L relative to S caused a significant increase in the hydrophobicity. (ii) This increase was independent of isoprenylation. (iii) In contrast, other, artificial modifications at either the N or C terminus of S did not increase the hydrophobicity. (iv) The increased hydrophobicity was not sufficient for particle assembly; nevertheless, we speculate that it might facilitate virion assembly.
Camille Sureau - One of the best experts on this subject based on the ideXlab platform.
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the Hepatitis Delta Virus replication and pathogenesis
Journal of Hepatology, 2016Co-Authors: Camille Sureau, Francesco NegroAbstract:Hepatitis Delta Virus (HDV) is a defective Virus and a satellite of the Hepatitis B Virus (HBV). Its RNA genome is unique among animal Viruses, but it shares common features with some plant viroids, including a replication mechanism that uses a host RNA polymerase. In infected cells, HDV genome replication and formation of a nucleocapsid-like ribonucleoprotein (RNP) are independent of HBV. But the RNP cannot exit, and therefore propagate, in the absence of HBV, as the latter supplies the propagation mechanism, from coating the HDV RNP with the HBV envelope proteins for cell egress to delivery of the HDV virions to the human hepatocyte target. HDV is therefore an obligate satellite of HBV; it infects humans either concomitantly with HBV or after HBV infection. HDV affects an estimated 15 to 20 million individuals worldwide, and the clinical significance of HDV infection is more severe forms of viral Hepatitis--acute or chronic--, and a higher risk of developing cirrhosis and hepatocellular carcinoma in comparison to HBV monoinfection. This review covers molecular aspects of HDV replication cycle, including its interaction with the helper HBV and the pathogenesis of infection in humans.
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role of n glycosylation of Hepatitis b Virus envelope proteins in morphogenesis and infectivity of Hepatitis Delta Virus
Journal of Virology, 2003Co-Authors: Camille Sureau, Chantal Fournierwirth, Patrick MaurelAbstract:Hepatitis Delta Virus (HDV) particles are coated with the large (L), middle (M), and small (S) Hepatitis B Virus envelope proteins. In the present study, we constructed glycosylation-defective envelope protein mutants and evaluated their capacity to assist in the maturation of infectious HDV in vitro. We observed that the removal of N-linked carbohydrates on the S, M, and L proteins was tolerated for the assembly of subviral Hepatitis B Virus (HBV) particles but was partially inhibitory for the formation of HDV virions. However, when assayed on primary cultures of human hepatocytes, virions coated with S, M, and L proteins lacking N-linked glycans were infectious. Furthermore, in the absence of M, HDV particles coated with nonglycosylated S and L proteins retained infectivity. These results indicate that carbohydrates on the HBV envelope proteins are not essential for the in vitro infectivity of HDV.
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production of infectious Hepatitis Delta Virus in vitro and neutralization with antibodies directed against Hepatitis b Virus pre s antigens
Journal of Virology, 1992Co-Authors: Camille Sureau, A M Moriarty, G B Thornton, Robert E LanfordAbstract:Hepatitis Delta Virus (HDV) particles were produced in Huh7 human hepatoma cells by transfection with cloned Hepatitis B Virus (HBV) DNA and HDV cDNA. The particles were characterized by their buoyant density, the presence of encapsidated viral RNA, and their ability to infect primary cultures of chimpanzee hepatocytes. Successful infection was evidenced by the appearance of increasing amounts of intracellular HDV RNA after exposure to particles. Infection was prevented when particles were incubated with antibodies directed against synthetic peptides specific for epitopes of the pre-S1 or pre-S2 domains of the HBV envelope proteins before exposure to hepatocytes. These data demonstrate that HDV particles produced in vitro are infectious and indicate (i) that infectious particles are coated with HBV envelope proteins that contain the pre-S1 and pre-S2 regions, (ii) that epitopes of the pre-S1 and pre-S2 domains of HBV envelope proteins are exposed at the surface of HDV particles, and (iii) that antibodies directed against those epitopes have neutralizing activity against HDV.
Martin Pelchat - One of the best experts on this subject based on the ideXlab platform.
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The Hepatitis Delta Virus accumulation requires paraspeckle components and affects NEAT1 level and PSP1 localization
Scientific Reports, 2018Co-Authors: Yasnee Beeharry, Gabrielle Goodrum, Christian J. Imperiale, Martin PelchatAbstract:The Hepatitis Delta Virus (HDV) relies mainly on host proteins for its replication. We previously identified that PSF and p54nrb associate with the HDV RNA genome during viral replication. Together with PSP1, these proteins are part of paraspeckles, which are subnuclear bodies nucleated by the long non-coding RNA NEAT1 . In this work, we established the requirement for PSF, p54nrb and PSP1 in HDV replication using RNAi-mediated knockdown in HEK-293 cells replicating the HDV RNA genome. We determined that HDV replication induces the delocalization of PSP1 to cytoplasmic foci containing PABP and increases NEAT1 level causing an enlargement of NEAT1 foci. Overall, our data support a role for the main paraspeckles proteins in HDV life cycle and indicate that HDV replication causes a cellular stress and induces both a delocalization of the PSP1 to the cytoplasm and a disruption of paraspeckles.
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identification of a binding site for asf sf2 on an rna fragment derived from the Hepatitis Delta Virus genome
PLOS ONE, 2013Co-Authors: Dorota Sikora, Dajiang Zhang, Teodora Bojic, Yasnee Beeharry, Ali Tanara, Martin PelchatAbstract:The Hepatitis Delta Virus (HDV) is a small (~1700 nucleotides) RNA pathogen which encodes only one open reading frame. Consequently, HDV is dependent on host proteins to replicate its RNA genome. Recently, we reported that ASF/SF2 binds directly and specifically to an HDV-derived RNA fragment which has RNA polymerase II promoter activity. Here, we localized the binding site of ASF/SF2 on the HDV RNA fragment by performing binding experiments using purified recombinant ASF/SF2 combined with deletion analysis and site-directed mutagenesis. In addition, we investigated the requirement of ASF/SF2 for HDV RNA replication using RNAi-mediated knock-down of ASF/SF2 in 293 cells replicating HDV RNA. Overall, our results indicate that ASF/SF2 binds to a purine-rich region distant from both the previously published initiation site of HDV mRNA transcription and binding site of RNAP II, and suggest that this protein is not involved in HDV replication in the cellular system used.
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binding of the polypyrimidine tract binding protein associated splicing factor psf to the Hepatitis Delta Virus rna
Virology, 2006Co-Authors: Valerie S Grecostewart, Catherine Stlaurent Thibault, Martin PelchatAbstract:The Hepatitis Delta Virus (HDV) has a very limited protein coding capacity and must rely on host proteins for its replication. A ribonucleoprotein complex was detected following UV cross-linking between HeLa nuclear proteins and an RNA corresponding to the right terminal stem-loop domain of HDV genomic RNA. Mass spectrometric analysis of the complex revealed the polypyrimidine tract-binding protein-associated splicing factor (PSF) as a novel HDV RNA-interacting protein. Co-immunoprecipitation demonstrated the interaction between HDV RNA and PSF both in vitro in HeLa nuclear extract and in vivo within HeLa cells containing both polarities of the HDV genome. Analysis of the binding of various HDV-derived RNAs to purified, recombinant PSF further confirmed the specificity of the interaction and revealed that PSF directly binds to the terminal stem-loop domains of both polarities of HDV RNA. Our findings provide evidence of the involvement of a host mRNA processing protein in the HDV life cycle.
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the subviral rna database a toolbox for viroids the Hepatitis Delta Virus and satellite rnas research
BMC Microbiology, 2006Co-Authors: Lynda Rocheleau, Martin PelchatAbstract:Background Viroids, satellite RNAs, satellites Viruses and the human Hepatitis Delta Virus form the 'brotherhood' of the smallest known infectious RNA agents, known as the subviral RNAs. For most of these species, it is generally accepted that characteristics such as cell movement, replication, host specificity and pathogenicity are encoded in their RNA sequences and their resulting RNA structures. Although many sequences are indexed in publicly available databases, these sequence annotation databases do not provide the advanced searches and data manipulation capability for identifying and characterizing subviral RNA motifs.
Ricardo Flores - One of the best experts on this subject based on the ideXlab platform.
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pathogenesis by subviral agents viroids and Hepatitis Delta Virus
Current Opinion in Virology, 2016Co-Authors: Ricardo Flores, Robert A Owens, John M TaylorAbstract:The viroids of plants are the simplest known infectious genetic elements. They have RNA genomes of up to 400 nucleotides in length and no protein encoding capacity. Hepatitis Delta Virus (HDV), an infectious agent found only in humans co-infected with Hepatitis B Virus (HBV), is just slightly more complex, with an RNA genome of about 1700 nucleotides, and the ability to express just one small protein. Viroid and HDV RNAs share several features that include circular structure, compact folding, and replication via a rolling-circle mechanism. Both agents were detected because of their obvious pathogenic effects. Their simplicity demands a greater need than conventional RNA or DNA Viruses to redirect host components for facilitating their infectious cycle, a need that directly and indirectly incites pathogenic effects. The mechanisms by which these pathogenic effects are produced are the topic of this review. In this context, RNA silencing mediates certain aspects of viroid pathogenesis.
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viroids and Hepatitis Delta Virus
Seminars in Liver Disease, 2012Co-Authors: Ricardo Flores, Susana Ruizruiz, Pedro SerraAbstract:There is a subviral world, whose most prominent representatives are viroids. Despite being solely composed by a circular, highly structured RNA of ~250 to 400 nucleotides without protein-coding ability (all Viruses code for one or more proteins), viroids can infect and incite specific diseases in higher plants. The RNA of human Hepatitis Delta Virus (HDV), the smallest genome of an animal Virus, displays striking similarities with viroids: It is circular, folds into a rodlike secondary structure, and replicates through a rolling-circle mechanism catalyzed by host enzymes and cis-acting ribozymes. However, HDV RNA is larger (~1700 nucleotides), encodes a protein in its antigenomic polarity (the ∂ antigen), and depends for transmission on Hepatitis B Virus. The presence of ribozymes in some viroids and in HDV RNA, along with their structural simplicity, makes them candidates for being molecular fossils of the RNA world that presumably preceded our extant world based on DNA and proteins.
John L. Casey - One of the best experts on this subject based on the ideXlab platform.
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a prenylation inhibitor prevents production of infectious Hepatitis Delta Virus particles
Journal of Virology, 2002Co-Authors: Bruno B Bordier, John L. Casey, Patricia L Marion, Kazuo Ohashi, Mark A Kay, Harry B Greenberg, Jeffrey S GlennAbstract:Hepatitis Delta Virus (HDV) causes both acute and chronic liver disease throughout the world. Effective medical therapy is lacking. Previous work has shown that the assembly of HDV Virus-like particles (VLPs) could be abolished by BZA-5B, a compound with farnesyltransferase inhibitory activity. Here we show that FTI-277, another farnesyltransferase inhibitor, prevented the production of complete, infectious HDV virions of two different genotypes. Thus, in spite of the added complexity and assembly determinants of infectious HDV virions compared to VLPs, the former are also sensitive to pharmacological prenylation inhibition. Moreover, production of HDV genotype III virions, which is associated with particularly severe clinical disease, was as sensitive to prenylation inhibition as was that of HDV genotype I virions. Farnesyltransferase inhibitors thus represent an attractive potential class of novel antiviral agents for use against HDV, including the genotypes associated with most severe disease.
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geographic distribution and genetic variability of Hepatitis Delta Virus genotype i
Virology, 1997Co-Authors: John L Gerin, Obaid A Shakil, Stephanos J Hadziyannis, Jay H Hoofnagle, Adrian M Di Bisceglie, John L. CaseyAbstract:Abstract Three genotypes of Hepatitis Delta Virus (HDV) have been identified, each with different geographic distributions and disease associations. To better define the geographic distribution and genetic variability of HDV genotype I, and to evaluate the extent of genome variability in populations with different patterns of HDV infection, we have analyzed the sequence of HDV RNA in the sera of 72 patients from different areas. Patients were primarily residents of the United States and areas in and around Greece, including Archangelos, Rhodes. All sequences obtained belonged to HDV genotype I, confirming the wide geographic distribution of this genotype and its predominance in Europe and the United States. In contrast to previous studies, phylogenetic analysis of this large and diverse group of sequences, along with all available previously published HDV sequences, showed no well-defined subtypes within genotype I. Low sequence diversity was found for isolates from the United States, Archangelos, Turkey, and Albania, suggesting that HDV was introduced more recently and/or from fewer sources into these areas as compared to mainland Greece, Italy, and north Africa, where sequence diversity is much greater. The low sequence diversity among isolates from Archangelos is particularly interesting in light of the unusually mild pattern of HDV disease found in this community. Comparison of nucleic acid and amino acid sequences within and among genotypes indicated both highly conserved regions as well as genotype-specific sequences that could be related to functional differences. The most distinctive of the latter was that corresponding to the C-terminal 19–20 amino acids of the long form of Hepatitis Delta antigen, which is highly conserved within each genotype but considerably diverged among them.
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rna editing of Hepatitis Delta Virus antigenome by dsrna adenosine deaminase
Nature, 1996Co-Authors: Andrew G. Polson, John L. CaseyAbstract:Hepatitis Delta Virus (HDV) is a subviral human pathogen that requires Hepatitis B Virus (HBV) for packaging1,2. Concurrent infection by HBV and HDV increases the risk of severe liver disease compared to infection with HBV alone3. The HDV genome is a closed circular RNA of about 1,700 bases which is replicated through an RNA intermediate, the antigenome4. Both RNAs can be folded into highly base-paired, rod-shaped structures, similar to the plant viroid RNAs5. Two forms of the sole HDV protein, Hepatitis Delta antigen, are derived from a single open reading frame by RNA editing; the enzymes responsible for the editing have not been characterized. Here we report that the purified enzyme dsRAD (for double-stranded-RNA-adenosine deaminase) can edit HDV antigenomic RNA in vitro. Most important, we observe that mutations in critical sequences of the antigenome have identical effects on in vitro and in vivo editing, suggesting that dsRAD, or a closely related enzyme, is responsible for editing HDV RNA in vivo.