401
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Kapsch AM, Farcet MR, Antoine G, Kreil TR. A nonenveloped virus with a lipid envelope: hepatitis A virus as used in virus-reduction studies. Transfusion 2017; 57:1433-1439. [DOI: 10.1111/trf.14091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/24/2017] [Accepted: 02/01/2017] [Indexed: 11/28/2022]
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402
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Aguilera ER, Erickson AK, Jesudhasan PR, Robinson CM, Pfeiffer JK. Plaques Formed by Mutagenized Viral Populations Have Elevated Coinfection Frequencies. mBio 2017; 8:e02020-16. [PMID: 28292984 PMCID: PMC5350468 DOI: 10.1128/mbio.02020-16] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 02/14/2017] [Indexed: 02/05/2023] Open
Abstract
The plaque assay is a common technique used to measure virus concentrations and is based upon the principle that each plaque represents a single infectious unit. As such, the number of plaques is expected to correlate linearly with the virus dilution plated, and each plaque should be formed by a single founder virus. Here, we examined whether more than one virus can contribute to plaque formation. By using genetic and phenotypic assays with genetically marked polioviruses, we found that multiple parental viruses are present in 5 to 7% of plaques, even at an extremely low multiplicity of infection. We demonstrated through visual and biophysical assays that, like many viral stocks, our viral stocks contain both single particles and aggregates. These data suggest that aggregated virions are capable of inducing coinfection and chimeric plaque formation. In fact, inducing virion aggregation via exposure to low pH increased coinfection in a flow cytometry-based assay. We hypothesized that plaques generated by viruses with high mutation loads may have higher coinfection frequencies due to processes restoring fitness, such as complementation and recombination. Indeed, we found that coinfection frequency correlated with mutation load, with 17% chimeric plaque formation for heavily mutagenized viruses. Importantly, the frequency of chimeric plaques may be underestimated by up to threefold, since coinfection with the same parental virus cannot be scored in our assay. This work indicates that more than one virus can contribute to plaque formation and that coinfection may assist plaque formation in situations where the amount of genome damage is high.IMPORTANCE One of the most common methods to quantify viruses is the plaque assay, where it is generally presumed that each plaque represents a single infectious virus. Using genetically marked polioviruses, we demonstrate that a plaque can contain more than one parental virus, likely due to aggregates within virus stocks that induce coinfection of a cell. A relatively small number of plaques are the products of coinfection for our standard virus stocks. However, mutagenized virus stocks with increased genome damage give rise to a higher amount of plaques that are chimeric. These results suggest that coinfection may aid plaque formation of viruses with genome damage, possibly due to processes such as complementation and recombination. Overall, our results suggest that the relationship between viral dilution and plaque number may not be linear, particularly for mutagenized viral populations.
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Affiliation(s)
- Elizabeth R Aguilera
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Andrea K Erickson
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Palmy R Jesudhasan
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Christopher M Robinson
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Julie K Pfeiffer
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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403
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Collective Infectious Units in Viruses. Trends Microbiol 2017; 25:402-412. [PMID: 28262512 DOI: 10.1016/j.tim.2017.02.003] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/13/2016] [Accepted: 02/06/2017] [Indexed: 01/15/2023]
Abstract
Increasing evidence indicates that viruses do not simply propagate as independent virions among cells, organs, and hosts. Instead, viral spread is often mediated by structures that simultaneously transport groups of viral genomes, such as polyploid virions, aggregates of virions, virion-containing proteinaceous structures, secreted lipid vesicles, and virus-induced cell-cell contacts. These structures increase the multiplicity of infection, independently of viral population density and transmission bottlenecks. Collective infectious units may contribute to the maintenance of viral genetic diversity, and could have implications for the evolution of social-like virus-virus interactions. These may include various forms of cooperation such as immunity evasion, genetic complementation, division of labor, and relaxation of fitness trade-offs, but also noncooperative interactions such as negative dominance and interference, potentially leading to conflict.
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404
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Altan-Bonnet N. Lipid Tales of Viral Replication and Transmission. Trends Cell Biol 2017; 27:201-213. [PMID: 27838086 PMCID: PMC5318230 DOI: 10.1016/j.tcb.2016.09.011] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 09/26/2016] [Accepted: 09/29/2016] [Indexed: 12/22/2022]
Abstract
Positive-strand RNA viruses are the largest group of RNA viruses on Earth and cellular membranes are critical for all aspects of their life cycle, from entry and replication to exit. In particular, membranes serve as platforms for replication and as carriers to transmit these viruses to other cells, the latter either as an envelope surrounding a single virus or as the vesicle containing a population of viruses. Notably, many animal and human viruses appear to induce and exploit phosphatidylinositol 4-phosphate/cholesterol-enriched membranes for replication, whereas many plant and insect-vectored animal viruses utilize phosphatidylethanolamine/cholesterol-enriched membranes for the same purpose; and phosphatidylserine-enriched membrane carriers are widely used by both single and populations of viruses for transmission. Here I discuss the implications for viral pathogenesis and therapeutic development of this remarkable convergence on specific membrane lipid blueprints for replication and transmission.
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Affiliation(s)
- Nihal Altan-Bonnet
- Laboratory of Host-Pathogen Dynamics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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405
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Infectious Bursal Disease Virus Subverts Autophagic Vacuoles To Promote Viral Maturation and Release. J Virol 2017; 91:JVI.01883-16. [PMID: 27974565 DOI: 10.1128/jvi.01883-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/07/2016] [Indexed: 01/30/2023] Open
Abstract
Autophagy functions as an intrinsic antiviral defense. However, some viruses can subvert or even enhance host autophagic machinery to increase viral replication and pathogenesis. The role of autophagy during avibirnavirus infection, especially late stage infection, remains unclear. In this study, infectious bursal disease virus (IBDV) was used to investigate the role of autophagy in avibirnavirus replication. We demonstrated IBDV induction of autophagy as a significant increase in puncta of LC3+ autophagosomes, endogenous levels of LC3-II, and ultrastructural characteristics typical of autophagosomes during the late stage of infection. Induction of autophagy enhances IBDV replication, whereas inhibition of autophagy impairs viral replication. We also demonstrated that IBDV infection induced autophagosome-lysosome fusion, but without active degradation of their contents. Moreover, inhibition of fusion or of lysosomal hydrolysis activity significantly reduced viral replication, indicating that virions utilized the low-pH environment of acidic organelles to facilitate viral maturation. Using immuno-transmission electron microscopy (TEM), we observed that a large number of intact IBDV virions were arranged in a lattice surrounded by p62 proteins, some of which lay between virions. Additionally, many virions were encapsulated within the vesicular membranes, with an obvious release stage observed by TEM. The autophagic endosomal pathway facilitates low-pH-mediated maturation of viral proteins and membrane-mediated release of progeny virions.IMPORTANCE IBDV is the most extensively studied virus in terms of molecular characteristics and pathogenesis; however, mechanisms underlying the IBDV life cycle require further exploration. The present study demonstrated that autophagy enhances viral replication at the late stage of infection, and the autophagy pathway facilitates IBDV replication complex function and virus assembly, which is critical to completion of the virus life cycle. Moreover, the virus hijacks the autophagic vacuoles to mature in an acidic environment and release progeny virions in a membrane-mediated cell-to-cell manner. This autophagic endosomal pathway is proposed as a new mechanism that facilitates IBDV maturation, release, and reinternalization. This report presents a concordance in exit strategies among some RNA and DNA viruses, which exploit autophagy pathway for their release from cells.
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406
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CD63 Regulates Epstein-Barr Virus LMP1 Exosomal Packaging, Enhancement of Vesicle Production, and Noncanonical NF-κB Signaling. J Virol 2017; 91:JVI.02251-16. [PMID: 27974566 DOI: 10.1128/jvi.02251-16] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 12/06/2016] [Indexed: 12/13/2022] Open
Abstract
Latent membrane protein 1 (LMP1) is an Epstein-Barr virus (EBV)-encoded oncoprotein that is packaged into small extracellular vesicles (EVs) called exosomes. Trafficking of LMP1 into multivesicular bodies (MVBs) alters the content and function of exosomes. LMP1-modified exosomes enhance the growth, migration, and invasion of malignant cells, demonstrating the capacity to manipulate the tumor microenvironment and enhance the progression of EBV-associated cancers. Despite the growing evidence surrounding the significance of LMP1-modified exosomes in cancer, very little is understood about the mechanisms that orchestrate LMP1 incorporation into these vesicles. Recently, LMP1 was shown to be copurified with CD63, a conserved tetraspanin protein enriched in late endosomal and lysosomal compartments. Here, we demonstrate the importance of CD63 presence for exosomal packaging of LMP1. Nanoparticle tracking analysis and gradient purification revealed an increase in extracellular vesicle secretion and exosomal proteins following LMP1 expression. Immunoisolation of CD63-positive exosomes exhibited accumulation of LMP1 in this vesicle population. Functionally, CRISPR/Cas9 knockout of CD63 resulted in a reduction of LMP1-induced particle secretion. Furthermore, LMP1 packaging was severely impaired in CD63 knockout cells, concomitant with a disruption in the perinuclear localization of LMP1. Importantly, LMP1 trafficking to lipid rafts and activation of NF-κB and PI3K/Akt pathways remained intact following CD63 knockout, while mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and noncanonical NF-κB activation were observed to be increased. These results suggest that CD63 is a critical player in LMP1 exosomal trafficking and LMP1-mediated enhancement of exosome production and may play further roles in limiting downstream LMP1 signaling.IMPORTANCE EBV is a ubiquitous gamma herpesvirus linked to malignancies such as nasopharyngeal carcinoma, Burkitt's lymphoma, and Hodgkin's lymphoma. In the context of cancer, EBV hijacks the exosomal pathway to modulate cell-to-cell signaling by secreting viral components such as an oncoprotein, LMP1, into host cell membrane-bound EVs. Trafficking of LMP1 into exosomes is associated with increased oncogenicity of these secreted vesicles. However, we have only a limited understanding of the mechanisms surrounding exosomal cargo packaging, including viral proteins. Here, we describe a role of LMP1 in EV production that requires CD63 and provide an extensive demonstration of CD63-mediated exosomal LMP1 release that is distinct from lipid raft trafficking. Finally, we present further evidence of the role of CD63 in limiting LMP1-induced noncanonical NF-κB and ERK activation. Our findings have implications for future investigations of physiological and pathological mechanisms of exosome biogenesis, protein trafficking, and signal transduction, especially in viral-associated tumorigenesis.
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407
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Abstract
Virtually all cells in the organism secrete extracellular vesicles (EVs), a heterogeneous population of lipid bilayer membrane-enclosed vesicles that transport and deliver payloads of proteins and nucleic acids to recipient cells, thus playing central roles in cell-cell communications. Exosomes, nanosized EVs of endosomal origin, regulate many pathophysiological processes including immune responses and inflammation, tumour growth, and infection. Healthy subjects and patients with different diseases release exosomes with different RNA and protein contents into the circulation, which can be measured as biomarkers. The discovery of exosomes as natural carriers of functional small RNA and proteins has raised great interest in the drug delivery field, as it may be possible to harness these vesicles for therapeutic delivery of miRNA, siRNA, mRNA, lncRNA, peptides, and synthetic drugs. However, systemically delivered exosomes accumulate in liver, kidney, and spleen. Targeted exosomes can be obtained by displaying targeting molecules, such as peptides or antibody fragments recognizing target antigens, on the outer surface of exosomes. Display of glycosylphosphatidylinositol (GPI)-anchored nanobodies on EVs is a novel technique that enables EV display of a variety of proteins including antibodies, reporter proteins, and signaling molecules. However, naturally secreted exosomes show limited pharmaceutical acceptability. Engineered exosome mimetics that incorporate desirable components of natural exosomes into synthetic liposomes or nanoparticles, and are assembled using controllable procedures may be more acceptable pharmaceutically. In this communication, we review the current understanding of physiological and pathophysiological roles of exosomes, their potential applications as diagnostic markers, and current efforts to develop improved exosome-based drug delivery systems.
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Affiliation(s)
- Lucio Barile
- Laboratory of Cellular and Molecular Cardiology, Cardiocentro Ticino Foundation, Lugano, Swiss Institute for Regenerative Medicine (SIRM), Taverne, Switzerland.
| | - Giuseppe Vassalli
- Laboratory of Cellular and Molecular Cardiology, Cardiocentro Ticino Foundation, Lugano, Swiss Institute for Regenerative Medicine (SIRM), Taverne, Switzerland; Dept. of Cardiology, University of Lausanne Medical Hospital (CHUV), Lausanne, Switzerland.
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408
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Potent neutralization of hepatitis A virus reveals a receptor mimic mechanism and the receptor recognition site. Proc Natl Acad Sci U S A 2017; 114:770-775. [PMID: 28074040 PMCID: PMC5278457 DOI: 10.1073/pnas.1616502114] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Hepatitis A virus (HAV) infects ∼1.4 million people annually and, although there is a vaccine, there are no licensed therapeutic drugs. HAV is unusually stable (making disinfection problematic) and little is known of how it enters cells and releases its RNA. Here we report a potent HAV-specific monoclonal antibody, R10, which neutralizes HAV infection by blocking attachment to the host cell. High-resolution cryo-EM structures of HAV full and empty particles and of the complex of HAV with R10 Fab reveal the atomic details of antibody binding and point to a receptor recognition site at the pentamer interface. These results, together with our observation that the R10 Fab destabilizes the capsid, suggest the use of a receptor mimic mechanism to neutralize virus infection, providing new opportunities for therapeutic intervention.
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409
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Hepatitis E virus ORF3 is a functional ion channel required for release of infectious particles. Proc Natl Acad Sci U S A 2017; 114:1147-1152. [PMID: 28096411 DOI: 10.1073/pnas.1614955114] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) is the leading cause of enterically transmitted viral hepatitis globally. Of HEV's three ORFs, the function of ORF3 has remained elusive. Here, we demonstrate that via homophilic interactions ORF3 forms multimeric complexes associated with intracellular endoplasmic reticulum (ER)-derived membranes. HEV ORF3 shares several structural features with class I viroporins, and the function of HEV ORF3 can be maintained by replacing it with the well-characterized viroporin influenza A virus (IAV) matrix-2 protein. ORF3's ion channel function is further evidenced by its ability to mediate ionic currents when expressed in Xenopus laevis oocytes. Furthermore, we identified several positions in ORF3 critical for its formation of multimeric complexes, ion channel activity, and, ultimately, release of infectious particles. Collectively, our data demonstrate a previously undescribed function of HEV ORF3 as a viroporin, which may serve as an attractive target in developing direct-acting antivirals.
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410
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Méndez F, Romero N, Cubas LL, Delgui LR, Rodríguez D, Rodríguez JF. Non-Lytic Egression of Infectious Bursal Disease Virus (IBDV) Particles from Infected Cells. PLoS One 2017; 12:e0170080. [PMID: 28095450 PMCID: PMC5240931 DOI: 10.1371/journal.pone.0170080] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 12/28/2016] [Indexed: 11/30/2022] Open
Abstract
Infectious bursal disease virus (IBDV), a member of the Birnaviridae family, is responsible for a devastating immunosuppressive disease affecting juvenile domestic chickens. IBDV particles are naked icosahedrons enclosing a bipartite double-stranded RNA genome harboring three open reading frames (ORF). One of these ORFs codes for VP5, a non-structural polypeptide dispensable for virus replication in tissue culture but essential for IBDV pathogenesis. Using two previously described recombinant viruses, whose genomes differ in a single nucleotide, expressing or not the VP5 polypeptide, we have analyzed the role of this polypeptide during the IBDV replication process. Here, we show that VP5 is not involved in house-keeping steps of the virus replication cycle; i.e. genome transcription/replication, protein translation and virus assembly. Although infection with the VP5 expressing and non-expressing viruses rendered similar intracellular infective progeny yields, striking differences were detected on the ability of their progenies to exiting infected cells. Experimental data shows that the bulk of the VP5-expressing virus progeny efficiently egresses infected cells during the early phase of the infection, when viral metabolism is peaking and virus-induced cell death rates are as yet minimal, as determined by qPCR, radioactive protein labeling and quantitative real-time cell death analyses. In contrast, the release of the VP5-deficient virus progeny is significantly abridged and associated to cell death. Taken together, data presented in this report show that IBDV uses a previously undescribed VP5-dependent non-lytic egress mechanism significantly enhancing the virus dissemination speed. Ultrastructural analyses revealed that newly assembled IBDV virions associate to a vesicular network apparently facilitating their trafficking from virus assembly factories to the extracellular milieu, and that this association requires the expression of the VP5 polypeptide.
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Affiliation(s)
- Fernando Méndez
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | - Nicolás Romero
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | - Liliana L. Cubas
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | - Laura R. Delgui
- Instituto de Histología y Embriología de Mendoza - CONICET, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Dolores Rodríguez
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | - José F. Rodríguez
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
- * E-mail:
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411
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Gerold G, Bruening J, Weigel B, Pietschmann T. Protein Interactions during the Flavivirus and Hepacivirus Life Cycle. Mol Cell Proteomics 2017; 16:S75-S91. [PMID: 28077444 DOI: 10.1074/mcp.r116.065649] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 01/11/2017] [Indexed: 12/28/2022] Open
Abstract
Protein-protein interactions govern biological functions in cells, in the extracellular milieu, and at the border between cells and extracellular space. Viruses are small intracellular parasites and thus rely on protein interactions to produce progeny inside host cells and to spread from cell to cell. Usage of host proteins by viruses can have severe consequences e.g. apoptosis, metabolic disequilibria, or altered cell proliferation and mobility. Understanding protein interactions during virus infection can thus educate us on viral infection and pathogenesis mechanisms. Moreover, it has led to important clinical translations, including the development of new therapeutic and vaccination strategies. Here, we will discuss protein interactions of members of the Flaviviridae family, which are small enveloped RNA viruses. Dengue virus, Zika virus and hepatitis C virus belong to the most prominent human pathogenic Flaviviridae With a genome of roughly ten kilobases encoding only ten viral proteins, Flaviviridae display intricate mechanisms to engage the host cell machinery for their purpose. In this review, we will highlight how dengue virus, hepatitis C virus, Japanese encephalitis virus, tick-borne encephalitis virus, West Nile virus, yellow fever virus, and Zika virus proteins engage host proteins and how this knowledge helps elucidate Flaviviridae infection. We will specifically address the protein composition of the virus particle as well as the protein interactions during virus entry, replication, particle assembly, and release from the host cell. Finally, we will give a perspective on future challenges in Flaviviridae interaction proteomics and why we believe these challenges should be met.
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Affiliation(s)
- Gisa Gerold
- From the Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
| | - Janina Bruening
- From the Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
| | - Bettina Weigel
- From the Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
| | - Thomas Pietschmann
- From the Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
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412
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Chevaliez S, Pawlotsky JM. Hepatitis Viruses. Infect Dis (Lond) 2017. [DOI: 10.1016/b978-0-7020-6285-8.00165-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022] Open
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413
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Davey RA, Shtanko O, Anantpadma M, Sakurai Y, Chandran K, Maury W. Mechanisms of Filovirus Entry. Curr Top Microbiol Immunol 2017; 411:323-352. [PMID: 28601947 DOI: 10.1007/82_2017_14] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Filovirus entry into cells is complex, perhaps as complex as any viral entry mechanism identified to date. However, over the past 10 years, the important events required for filoviruses to enter into the endosomal compartment and fuse with vesicular membranes have been elucidated (Fig. 1). Here, we highlight the important steps that are required for productive entry of filoviruses into mammalian cells.
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Affiliation(s)
- R A Davey
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - O Shtanko
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - M Anantpadma
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Y Sakurai
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - K Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - W Maury
- Department of Microbiology, The University of Iowa, Iowa City, IA, USA.
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414
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Zhao X, Xie Y, Liu J. Evaluating Exosome Protein Content Changes Induced by Virus Activity Using SILAC Labeling and LC-MS/MS. Methods Enzymol 2017; 586:193-209. [DOI: 10.1016/bs.mie.2016.10.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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415
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Karaji N, Sattentau QJ. Efferocytosis of Pathogen-Infected Cells. Front Immunol 2017; 8:1863. [PMID: 29312342 PMCID: PMC5743670 DOI: 10.3389/fimmu.2017.01863] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 12/07/2017] [Indexed: 12/20/2022] Open
Abstract
The prompt and efficient clearance of unwanted and abnormal cells by phagocytes is termed efferocytosis and is crucial for organism development, maintenance of tissue homeostasis, and regulation of the immune system. Dying cells are recognized by phagocytes through pathways initiated via "find me" signals, recognition via "eat me" signals and down-modulation of regulatory "don't eat me" signals. Pathogen infection may trigger cell death that drives phagocytic clearance in an immunologically silent, or pro-inflammatory manner, depending on the mode of cell death. In many cases, efferocytosis is a mechanism for eliminating pathogens and pathogen-infected cells; however, some pathogens have subverted this process and use efferocytic mechanisms to avoid innate immune detection and assist phagocyte infection. In parallel, phagocytes can integrate signals received from infected dying cells to elicit the most appropriate effector response against the infecting pathogen. This review focuses on pathogen-induced cell death signals that drive infected cell recognition and uptake by phagocytes, and the outcomes for the infected target cell, the phagocyte, the pathogen and the host.
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Affiliation(s)
- Niloofar Karaji
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, United Kingdom
| | - Quentin J Sattentau
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford, United Kingdom
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416
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Abstract
Hepatitis A virus (HAV) is an unusual picornavirus that is released from cells cloaked in host-derived membranes. These quasi-enveloped virions (eHAV) are the only particle type circulating in blood during infection, whereas only nonenveloped virions are shed in feces. The reason for this is uncertain. Hepatocytes, the only cell type known to support HAV replication in vivo, are highly polarized epithelial cells with basolateral membranes facing onto hepatic (blood) sinusoids and apical membranes abutting biliary canaliculi from which bile is secreted to the gut. To assess whether eHAV and nonenveloped virus egress from cells via vectorially distinct pathways, we studied infected polarized cultures of Caco-2 and HepG2-N6 cells. Most (>99%) progeny virions were released apically from Caco-2 cells, whereas basolateral (64%) versus apical (36%) release was more balanced with HepG2-N6 cells. Both apically and basolaterally released virions were predominantly enveloped, with no suggestion of differential vectorial release of eHAV versus naked virions. Basolateral to apical transcytosis of either particle type was minimal (<0.02%/h) in HepG2-N6 cells, arguing against this as a mechanism for differences in membrane envelopment of serum versus fecal virus. High concentrations of human bile acids converted eHAV to nonenveloped virions, whereas virus present in bile from HAV-infected Ifnar1−/−Ifngr1−/− and Mavs−/− mice banded over a range of densities extending from that of eHAV to that of nonenveloped virions. We conclude that nonenveloped virions shed in feces are derived from eHAV released across the canalicular membrane and stripped of membranes by the detergent action of bile acids within the proximal biliary canaliculus. HAV is a hepatotropic, fecally/orally transmitted picornavirus that can cause severe hepatitis in humans. Recent work reveals that it has an unusual life cycle. Virus is found in cell culture supernatant fluids in two mature, infectious forms: one wrapped in membranes (quasi-enveloped) and another that is nonenveloped. Membrane-wrapped virions circulate in blood during acute infection and are resistant to neutralizing antibodies, likely facilitating HAV dissemination within the liver. On the other hand, virus shed in feces is nonenveloped and highly stable, facilitating epidemic spread and transmission to naive hosts. Factors controlling the biogenesis of these two distinct forms of the virus in infected humans are not understood. Here we characterize vectorial release of quasi-enveloped virions from polarized epithelial cell cultures and provide evidence that bile acids strip membranes from eHAV following its secretion into the biliary tract. These results enhance our understanding of the life cycle of this unusual picornavirus.
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417
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Designed proteins induce the formation of nanocage-containing extracellular vesicles. Nature 2016; 540:292-295. [PMID: 27919066 DOI: 10.1038/nature20607] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/31/2016] [Indexed: 01/26/2023]
Abstract
Complex biological processes are often performed by self-organizing nanostructures comprising multiple classes of macromolecules, such as ribosomes (proteins and RNA) or enveloped viruses (proteins, nucleic acids and lipids). Approaches have been developed for designing self-assembling structures consisting of either nucleic acids or proteins, but strategies for engineering hybrid biological materials are only beginning to emerge. Here we describe the design of self-assembling protein nanocages that direct their own release from human cells inside small vesicles in a manner that resembles some viruses. We refer to these hybrid biomaterials as 'enveloped protein nanocages' (EPNs). Robust EPN biogenesis requires protein sequence elements that encode three distinct functions: membrane binding, self-assembly, and recruitment of the endosomal sorting complexes required for transport (ESCRT) machinery. A variety of synthetic proteins with these functional elements induce EPN biogenesis, highlighting the modularity and generality of the design strategy. Biochemical analyses and cryo-electron microscopy reveal that one design, EPN-01, comprises small (~100 nm) vesicles containing multiple protein nanocages that closely match the structure of the designed 60-subunit self-assembling scaffold. EPNs that incorporate the vesicular stomatitis viral glycoprotein can fuse with target cells and deliver their contents, thereby transferring cargoes from one cell to another. These results show how proteins can be programmed to direct the formation of hybrid biological materials that perform complex tasks, and establish EPNs as a class of designed, modular, genetically-encoded nanomaterials that can transfer molecules between cells.
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418
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Minicircle HBV cccDNA with a Gaussia luciferase reporter for investigating HBV cccDNA biology and developing cccDNA-targeting drugs. Sci Rep 2016; 6:36483. [PMID: 27819342 PMCID: PMC5098228 DOI: 10.1038/srep36483] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 09/12/2016] [Indexed: 12/17/2022] Open
Abstract
Chronic Hepatitis B Virus (HBV) infection is generally not curable with current anti-viral drugs. Virus rebounds after stopping treatment from the stable HBV covalently-closed-circular DNA (cccDNA). The development of drugs that directly target cccDNA is hampered by the lack of robust HBV cccDNA models. We report here a novel HBV cccDNA technology that will meet the need. We engineered a minicircle HBV cccDNA with a Gaussia Luciferase reporter (mcHBV-GLuc cccDNA), which serves as a surrogate to measure cccDNA activity. The mcHBV-GLuc cccDNA was easily produced in bacteria, and it formed minichromosomes as HBV cccDNA episome DNA does when it was transfected into human hepatocytes. Compared to non-HBV minicircle plasmids, mcHBV-GLuc cccDNA showed persistent HBV-GLuc activity and HBx-dependent gene expression. Importantly, the mcHBV-GLuc cccDNA showed resistance to interferons (IFN) treatment, indicating its unique similarity to HBV cccDNA that is usually resistant to long-term IFN treatment in chronic HBV patients. Most importantly, GLuc illuminates cccDNA as a surrogate of cccDNA activity, providing a very sensitive and quick method to detect trace amount of cccDNA. The mcHBV-GLuc cccDNA model is independent of HBV infection, and will be valuable for investigating HBV cccDNA biology and for developing cccDNA-targeting drugs.
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419
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Barouch-Bentov R, Neveu G, Xiao F, Beer M, Bekerman E, Schor S, Campbell J, Boonyaratanakornkit J, Lindenbach B, Lu A, Jacob Y, Einav S. Hepatitis C Virus Proteins Interact with the Endosomal Sorting Complex Required for Transport (ESCRT) Machinery via Ubiquitination To Facilitate Viral Envelopment. mBio 2016; 7:e01456-16. [PMID: 27803188 PMCID: PMC5090039 DOI: 10.1128/mbio.01456-16] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 10/07/2016] [Indexed: 02/07/2023] Open
Abstract
Enveloped viruses commonly utilize late-domain motifs, sometimes cooperatively with ubiquitin, to hijack the endosomal sorting complex required for transport (ESCRT) machinery for budding at the plasma membrane. However, the mechanisms underlying budding of viruses lacking defined late-domain motifs and budding into intracellular compartments are poorly characterized. Here, we map a network of hepatitis C virus (HCV) protein interactions with the ESCRT machinery using a mammalian-cell-based protein interaction screen and reveal nine novel interactions. We identify HRS (hepatocyte growth factor-regulated tyrosine kinase substrate), an ESCRT-0 complex component, as an important entry point for HCV into the ESCRT pathway and validate its interactions with the HCV nonstructural (NS) proteins NS2 and NS5A in HCV-infected cells. Infectivity assays indicate that HRS is an important factor for efficient HCV assembly. Specifically, by integrating capsid oligomerization assays, biophysical analysis of intracellular viral particles by continuous gradient centrifugations, proteolytic digestion protection, and RNase digestion protection assays, we show that HCV co-opts HRS to mediate a late assembly step, namely, envelopment. In the absence of defined late-domain motifs, K63-linked polyubiquitinated lysine residues in the HCV NS2 protein bind the HRS ubiquitin-interacting motif to facilitate assembly. Finally, ESCRT-III and VPS/VTA1 components are also recruited by HCV proteins to mediate assembly. These data uncover involvement of ESCRT proteins in intracellular budding of a virus lacking defined late-domain motifs and a novel mechanism by which HCV gains entry into the ESCRT network, with potential implications for other viruses. IMPORTANCE Viruses commonly bud at the plasma membrane by recruiting the host ESCRT machinery via conserved motifs termed late domains. The mechanism by which some viruses, such as HCV, bud intracellularly is, however, poorly characterized. Moreover, whether envelopment of HCV and other viruses lacking defined late domains is ESCRT mediated and, if so, what the entry points into the ESCRT pathway are remain unknown. Here, we report the interaction network of HCV with the ESCRT machinery and a critical role for HRS, an ESCRT-0 complex component, in HCV envelopment. Viral protein ubiquitination was discovered to be a signal for HRS binding and HCV assembly, thereby functionally compensating for the absence of late domains. These findings characterize how a virus lacking defined late domains co-opts ESCRT to bud intracellularly. Since the ESCRT machinery is essential for the life cycle of multiple viruses, better understanding of this virus-host interplay may yield targets for broad-spectrum antiviral therapies.
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Affiliation(s)
- Rina Barouch-Bentov
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Gregory Neveu
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Fei Xiao
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Melanie Beer
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Elena Bekerman
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Stanford Schor
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Joseph Campbell
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Jim Boonyaratanakornkit
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
| | - Brett Lindenbach
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, Connecticut, USA
| | - Albert Lu
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA
| | - Yves Jacob
- Département de Virologie, Unité de Génétique Moléculaire des Virus ARN (GMVR), Institut Pasteur, Centre national de la recherche scientifique, and Université Paris Diderot, Paris, France
| | - Shirit Einav
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA
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420
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Abstract
All cells possess signaling pathways designed to trigger antiviral responses, notably characterized by type I interferon (IFN) production, upon recognition of invading viruses. Especially, host sensors recognize viral nucleic acids. Nonetheless, virtually all viruses have evolved potent strategies that preclude host responses within the infected cells. The plasmacytoid dendritic cell (pDC) is an immune cell type known as a robust type I IFN producer in response to viral infection. Evidence suggests that such functionality of the pDCs participates in viral clearance. Nonetheless, their contribution, which is likely complex and varies depending on the pathogen, is still enigmatic for many viruses. pDCs are not permissive to most viral infections, and consistently, recent examples suggest that pDCs respond to immunostimulatory viral RNA transferred via noninfectious and/or noncanonical viral/cellular carriers. Therefore, the pDC response likely bypasses innate signaling blockages induced by virus within infected cells. Importantly, the requirement for cell-cell contact is increasingly recognized as a hallmark of the pDC-mediated antiviral state, triggered by evolutionarily divergent RNA viruses.
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421
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Sanada T, Hirata Y, Naito Y, Yamamoto N, Kikkawa Y, Ishida Y, Yamasaki C, Tateno C, Ochiya T, Kohara M. Transmission of HBV DNA Mediated by Ceramide-Triggered Extracellular Vesicles. Cell Mol Gastroenterol Hepatol 2016; 3:272-283. [PMID: 28275693 PMCID: PMC5331779 DOI: 10.1016/j.jcmgh.2016.10.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 10/14/2016] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS An extracellular vesicle (EV) is a nanovesicle that shuttles proteins, nucleic acids, and lipids, thereby influencing cell behavior. A recent crop of reports have shown that EVs are involved in infectious biology, influencing host immunity and playing a role in the viral life cycle. In the present work, we investigated the EV-mediated transmission of hepatitis B virus (HBV) infection. METHODS We investigated the EV-mediated transmission of HBV infection by using a HBV infectious culture system that uses primary human hepatocytes derived from humanized chimeric mice (PXB-cells). Purified EVs were isolated by ultracentrifugation. To analyze the EVs and virions, we used stimulated emission depletion microscopy. RESULTS Purified EVs from HBV-infected PXB-cells were shown to contain HBV DNA and to be capable of transmitting HBV DNA to naive PXB-cells. These HBV-DNA-transmitting EVs were shown to be generated through a ceramide-triggered EV production pathway. Furthermore, we showed that these HBV-DNA-transmitting EVs were resistant to antibody neutralization; stimulated emission depletion microscopy showed that EVs lacked hepatitis B surface antigen, the target of neutralizing antibodies. CONCLUSIONS These findings suggest that EVs harbor a DNA cargo capable of transmitting viral DNA into hepatocytes during HBV infection, representing an additional antibody-neutralization-resistant route of HBV infection.
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Key Words
- BSA, bovine serum albumin
- ESCRT, endosomal sorting complexes required for transport
- EV, extracellular vesicle
- Extracellular Vesicles
- GEq, genome equivalent
- HA, hemagglutinin
- HBIG, hepatitis B immune globulin
- HBV
- HBV, hepatitis B virus
- HBc, hepatitis B core
- HBcAg, hepatitis B core antigen
- HBsAg, hepatitis B surface antigen
- MVB, multivesicular body
- PBS, phosphate-buffered saline
- PXB-cells, primary human hepatocytes derived from chimeric mice with human liver
- STED, stimulated emission depletion
- Transmission Pathway
- anti-HBs, antibody to hepatitis B surface antigen
- mRNA, messenger RNA
- nSMase, neutral sphingomyelinase
- nts, nucleotides
- qPCR, quantitative real-time polymerase chain reaction
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Affiliation(s)
- Takahiro Sanada
- Department of Microbiology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan
| | - Yuichi Hirata
- Department of Microbiology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan
| | - Yutaka Naito
- Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
| | - Naoki Yamamoto
- Department of Microbiology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan
| | - Yoshiaki Kikkawa
- Mammalian Genetics Project, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan
| | - Yuji Ishida
- PhoenixBio Co, Ltd, Higashi-Hiroshima, Hiroshima, Japan
| | | | - Chise Tateno
- PhoenixBio Co, Ltd, Higashi-Hiroshima, Hiroshima, Japan
| | - Takahiro Ochiya
- Division of Molecular and Cellular Medicine, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
| | - Michinori Kohara
- Department of Microbiology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo, Japan,Correspondence Address correspondence to: Michinori Kohara, PhD, Department of Microbiology and Cell Biology, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan. fax: (81) 3-5316-3137.Department of Microbiology and Cell BiologyTokyo Metropolitan Institute of Medical Science2-1-6 KamikitazawaSetagaya-kuTokyo 156-8506Japan
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422
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von Nordheim M, Boinay M, Leisi R, Kempf C, Ros C. Cutthroat Trout Virus-Towards a Virus Model to Support Hepatitis E Research. Viruses 2016; 8:v8100289. [PMID: 27775612 PMCID: PMC5086621 DOI: 10.3390/v8100289] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/07/2016] [Accepted: 10/07/2016] [Indexed: 12/16/2022] Open
Abstract
Cutthroat trout virus (CTV) is a non-pathogenic fish virus belonging to the Hepeviridae family, and it is distantly related to hepatitis E virus (HEV). Here, we report the development of an efficient cell culture system where CTV can consistently replicate to titers never observed before with a hepevirus. By using the rainbow trout gill (RTGill-W1) cell line, CTV reaches 1010 geq/mL intracellularly and 109 geq/mL extracellularly within 5–6 days in culture. We additionally established a qPCR system to investigate CTV infectivity, and developed a specific antibody directed against the viral capsid protein encoded by ORF2. With these methods, we were able to follow the progressive accumulation of viral RNA and the capsid protein, and their intracellular distribution during virus replication. Virus progeny purified through iodixanol density gradients indicated—that similar to HEV—CTV produced in cell culture is also lipid-associated. The lack of an efficient cell culture system has greatly impeded studies with HEV, a major human pathogen that causes hepatitis worldwide. Although several cell culture systems have recently been established, the replication efficiency of HEV is not robust enough to allow studies on different aspects of the virus replication cycle. Therefore, a surrogate virus that can replicate easily and efficiently in cultured cells would be helpful to boost research studies with hepeviruses. Due to its similarities, but also its key differences to HEV, CTV represents a promising tool to elucidate aspects of the replication cycle of Hepeviridae in general, and HEV in particular.
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Affiliation(s)
- Marcus von Nordheim
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland.
| | - Michel Boinay
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland.
| | - Remo Leisi
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland.
| | - Christoph Kempf
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland.
- CSL Behring AG, Bern 3014, Switzerland.
| | - Carlos Ros
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland.
- CSL Behring AG, Bern 3014, Switzerland.
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423
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Moradpour D, Grakoui A, Manns MP. Future landscape of hepatitis C research - Basic, translational and clinical perspectives. J Hepatol 2016; 65:S143-S155. [PMID: 27641984 DOI: 10.1016/j.jhep.2016.07.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 07/22/2016] [Accepted: 07/22/2016] [Indexed: 12/14/2022]
Abstract
With the latest all-oral interferon- and ribavirin-free regimens based on direct acting antivirals against the hepatitis C virus (HCV), sustained virological response rates of >90% are achieved, which is equivalent to cure. This has become possible for all genotypes and all subgroups of patients, including many of the most difficult-to-treat populations so far. Since a prophylactic HCV vaccine is not yet available, control of HCV infection will for the time being have to rely on the use of effective and safe antiviral treatments as well as their accessibility and affordability. Different approaches may apply to different parts of the world, eradication of HCV representing a major long-term goal. Whether hepatitis C becomes the first chronic viral infection to be eradicated without a prophylactic vaccine remains to be shown. Here, we briefly summarize advances in the molecular virology of hepatitis C, highlight lessons of biological relevance that were learned through the study of HCV, and its translational and clinical implications. We have also listed selected unsolved challenges, emphasizing that HCV is a unique model and that advances in this direction may yield knowledge of broad biological significance, novel technologies and insights into related important human pathogens.
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Affiliation(s)
- Darius Moradpour
- Division of Gastroenterology and Hepatology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
| | - Arash Grakoui
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine and Yerkes National Primate Research Center, Emory Vaccine Center, Atlanta, GA, USA.
| | - Michael P Manns
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Germany; German Centre for Infection Research (DZIF), partner site Hannover-Braunschweig, Germany.
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424
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Hirai-Yuki A, Hensley L, McGivern DR, González-López O, Das A, Feng H, Sun L, Wilson JE, Hu F, Feng Z, Lovell W, Misumi I, Ting JPY, Montgomery S, Cullen J, Whitmire JK, Lemon SM. MAVS-dependent host species range and pathogenicity of human hepatitis A virus. Science 2016; 353:1541-1545. [PMID: 27633528 PMCID: PMC5068972 DOI: 10.1126/science.aaf8325] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 09/02/2016] [Indexed: 12/24/2022]
Abstract
Hepatotropic viruses are important causes of human disease, but the intrahepatic immune response to hepatitis viruses is poorly understood because of a lack of tractable small- animal models. We describe a murine model of hepatitis A virus (HAV) infection that recapitulates critical features of type A hepatitis in humans. We demonstrate that the capacity of HAV to evade MAVS-mediated type I interferon responses defines its host species range. HAV-induced liver injury was associated with interferon-independent intrinsic hepatocellular apoptosis and hepatic inflammation that unexpectedly resulted from MAVS and IRF3/7 signaling. This murine model thus reveals a previously undefined link between innate immune responses to virus infection and acute liver injury, providing a new paradigm for viral pathogenesis in the liver.
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Affiliation(s)
- Asuka Hirai-Yuki
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Lucinda Hensley
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - David R McGivern
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Medicine, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Olga González-López
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Anshuman Das
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Hui Feng
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Lu Sun
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Justin E Wilson
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Genetics, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Fengyu Hu
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Zongdi Feng
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA
| | - William Lovell
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Ichiro Misumi
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Genetics, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Jenny P-Y Ting
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Genetics, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Stephanie Montgomery
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27517, USA
| | - John Cullen
- Department of Population Health and Pathobiology, North Carolina State University College of Veterinary Medicine, Raleigh, NC 27607, USA
| | - Jason K Whitmire
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Genetics, University of North Carolina, Chapel Hill, NC 27517, USA
| | - Stanley M Lemon
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Medicine, University of North Carolina, Chapel Hill, NC 27517, USA.
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425
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Exocytosis of Varicella-Zoster Virus Virions Involves a Convergence of Endosomal and Autophagy Pathways. J Virol 2016; 90:8673-85. [PMID: 27440906 PMCID: PMC5021422 DOI: 10.1128/jvi.00915-16] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 07/13/2016] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Varicella-zoster virus (VZV) is an extremely cell-associated herpesvirus with limited egress of viral particles. The induction of autophagy in VZV-infected monolayers is easily detectable; inhibition of autophagy leads to decreased VZV glycoprotein biosynthesis and diminished viral titers. To explain how autophagic flux could exert a proviral effect on the VZV infectious cycle, we postulated that the VZV exocytosis pathway following secondary envelopment may converge with the autophagy pathway. This hypothesis depended on known similarities between VZV gE and autophagy-related (Atg) Atg9/Atg16L1 trafficking pathways. Investigations were carried out with highly purified fractions of VZV virions. When the virion fraction was tested for the presence of autophagy and endosomal proteins, microtubule-associated protein 1 light chain (MAP1LC3B) and Ras-like GTPase 11 (Rab11) were detected. By two-dimensional (2D) and 3D imaging after immunolabeling, both proteins also colocalized with VZV gE in a proportion of cytoplasmic vesicles. When purified VZV virions were enumerated after immunoelectron microscopy, gold beads were detected on viruses following incubation with antibodies to VZV gE (∼100%), Rab11 (50%), and LC3B (30%). Examination of numerous electron micrographs demonstrated that enveloped virions were housed in single-membraned vesicles; viral particles were not observed in autophagosomes. Taken together, our data suggested that some viral particles after secondary envelopment accumulated in a heterogeneous population of single-membraned vesicular compartments, which were decorated with components from both the endocytic pathway (Rab11) and the autophagy pathway (LC3B). The latter cytoplasmic viral vesicles resembled an amphisome. IMPORTANCE VZV infection leads to increased autophagic flux, while inhibition of autophagy leads to a marked reduction in virus spread. In this investigation of the proviral role of autophagy, we found evidence for an intersection of viral exocytosis and autophagy pathways. Specifically, both LC3-II and Rab11 proteins copurified with some infectious VZV particles. The results suggested that a subpopulation of VZV particles were carried to the cell surface in single-walled vesicles with attributes of an amphisome, an organelle formed from the fusion of an endosome and an autophagosome. Our results also addressed the interpretation of autophagy/xenophagy results with mutated herpes simplex virus lacking its ICP34.5 neurovirulence gene (HSVΔ34.5). The VZV genome lacks an ICP34.5 ortholog, yet we found no evidence of VZV particles housed in a double-membraned autophagosome. In other words, xenophagy, a degradative process documented after infection with HSVΔ34.5, was not observed in VZV-infected cells.
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426
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427
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Wu YW, Mettling C, Wu SR, Yu CY, Perng GC, Lin YS, Lin YL. Autophagy-associated dengue vesicles promote viral transmission avoiding antibody neutralization. Sci Rep 2016; 6:32243. [PMID: 27558165 PMCID: PMC4997566 DOI: 10.1038/srep32243] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 08/04/2016] [Indexed: 12/26/2022] Open
Abstract
One of the major defense mechanisms against virus spread in vivo is the blocking of viral infectibility by neutralizing antibodies. We describe here the identification of infectious autophagy-associated dengue vesicles released from infected cells. These vesicles contain viral proteins E, NS1, prM/M, and viral RNA, as well as host lipid droplets and LC3-II, an autophagy marker. The viral RNA can be protected within the autophagic organelles since anti-dengue neutralizing antibodies do not have an effect on the vesicle-mediated transmission that is able to initiate a new round of infection in target cells. Importantly, such infectious vesicles were also detected in a patient serum. Our study suggests that autophagy machinery plays a new role in dengue virus transmission. This discovery explains the inefficiency of neutralizing antibody upon dengue infection as a potential immune evasion mechanism in vivo.
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Affiliation(s)
- Yan-Wei Wu
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | | | - Shang-Rung Wu
- Institute of Oral Medicine, College of Medicine and Hospital, National Cheng Kung University, Tainan, Taiwan
| | - Chia-Yi Yu
- Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Guey-Chuen Perng
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Yee-Shin Lin
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Yea-Lih Lin
- Institute of Human Genetics, CNRS-UPR1142, Montpellier, France
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428
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Yin X, Li X, Feng Z. Role of Envelopment in the HEV Life Cycle. Viruses 2016; 8:v8080229. [PMID: 27548201 PMCID: PMC4997591 DOI: 10.3390/v8080229] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 08/02/2016] [Accepted: 08/11/2016] [Indexed: 12/12/2022] Open
Abstract
Hepatitis E virus (HEV), an enterically transmitted hepatotropic virus, was thought to be non-enveloped for decades. However, recent studies have revealed that the virus circulating in the patient’s blood is completely cloaked in host membranes and resistant to neutralizing antibodies. The discovery of this novel enveloped form of HEV has raised a series of questions about the fundamental biology of HEV and the way this virus, which has been understudied in the past, interacts with its host. Here, we review recent advances towards understanding this phenomenon and discuss its potential impact on various aspects of the HEV life cycle and immunity.
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Affiliation(s)
- Xin Yin
- Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.
| | - Xinlei Li
- Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.
| | - Zongdi Feng
- Center for Vaccines and Immunity, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA.
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH 43205, USA.
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429
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Tabata K, Arimoto M, Arakawa M, Nara A, Saito K, Omori H, Arai A, Ishikawa T, Konishi E, Suzuki R, Matsuura Y, Morita E. Unique Requirement for ESCRT Factors in Flavivirus Particle Formation on the Endoplasmic Reticulum. Cell Rep 2016; 16:2339-47. [PMID: 27545892 DOI: 10.1016/j.celrep.2016.07.068] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 07/05/2016] [Accepted: 07/25/2016] [Indexed: 11/28/2022] Open
Abstract
Flavivirus infection induces endoplasmic reticulum (ER) membrane rearrangements to generate a compartment for replication of the viral genome and assembly of viral particles. Using quantitative mass spectrometry, we identified several ESCRT (endosomal sorting complex required for transport) proteins that are recruited to sites of virus replication on the ER. Systematic small interfering RNA (siRNA) screening revealed that release of both dengue virus and Japanese encephalitis virus was dramatically decreased by single depletion of TSG101 or co-depletion of specific combinations of ESCRT-III proteins, resulting in ≥1,000-fold titer reductions. By contrast, release was unaffected by depletion of some core ESCRTs, including VPS4. Reintroduction of ESCRT proteins to siRNA-depleted cells revealed interactions among ESCRT proteins that are crucial for flavivirus budding. Electron-microscopy studies revealed that the CHMP2 and CHMP4 proteins function directly in membrane deformation at the ER. Thus, a unique and specific subset of ESCRT contributes to ER membrane biogenesis during flavivirus infection.
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Affiliation(s)
- Keisuke Tabata
- Laboratory of Viral Infection, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
| | - Masaru Arimoto
- Laboratory of Viral Infection, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
| | - Masashi Arakawa
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Atsuki Nara
- Faculty of Bioscience, Nagahama Institute of Bio-science and Technology, Nagahama 526-0829, Japan
| | - Kazunobu Saito
- Core Instrumentation Facility, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
| | - Hiroko Omori
- Core Instrumentation Facility, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
| | - Arisa Arai
- Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan
| | - Tomohiro Ishikawa
- Department of Microbiology, Dokkyo Medical University School of Medicine, Tochigi 321-0293 Japan
| | - Eiji Konishi
- BIKEN Endowed Department of Dengue Vaccine Development, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; BIKEN Endowed Department of Dengue Vaccine Development, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
| | - Ryosuke Suzuki
- Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
| | - Yoshiharu Matsuura
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
| | - Eiji Morita
- Laboratory of Viral Infection, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan; Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan.
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430
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Liou AT, Wu SY, Liao CC, Chang YS, Chang CS, Shih C. A new animal model containing human SCARB2 and lacking stat-1 is highly susceptible to EV71. Sci Rep 2016; 6:31151. [PMID: 27499235 PMCID: PMC4976353 DOI: 10.1038/srep31151] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 07/14/2016] [Indexed: 12/04/2022] Open
Abstract
Enterovirus 71 (EV71) is a major threat to children worldwide. Children infected with EV71 could develop subclinical infection and hand-foot-and -mouth disease (HFMD). In severe cases, patients could develop encephalitis, paralysis, pulmonary edema, and death. A more user-friendly and robust animal model is essential to investigating EV71 pathogenesis. Here, we established a hybrid (hSCARB2(+/+)/stat-1(-/-)) mouse strain from crossbreeding SCARB2 transgenic and stat-1 KO mice, and compared the susceptibilities to EV71 infection and pathogenesis between parental and hybrid mice. Virus-encoded VP1 protein can be detected in the streaking nerve fibers in brain and spinal cord. This hybrid mouse strain at 2-week-old age can still be infected with different genotypes of EV71 at 1000-fold lower titer via an ip route. Infected hybrid mice developed earlier onset of CNS disease, paralysis, and death at a higher incidence. These advantages of this novel model meet the urgent need from the scientific community in basic and preclinical research in therapeutics and pathogenesis.
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Affiliation(s)
- An-Ting Liou
- Taiwan International Graduate Program (TIGP) in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan
| | - Szu-Yao Wu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
| | - Chun-Che Liao
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Ya-Shu Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Chih-Shin Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
| | - Chiaho Shih
- Taiwan International Graduate Program (TIGP) in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
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431
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Wilks J, Lien E, Jacobson AN, Fischbach MA, Qureshi N, Chervonsky AV, Golovkina TV. Mammalian Lipopolysaccharide Receptors Incorporated into the Retroviral Envelope Augment Virus Transmission. Cell Host Microbe 2016; 18:456-62. [PMID: 26468748 DOI: 10.1016/j.chom.2015.09.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/23/2015] [Accepted: 09/11/2015] [Indexed: 11/25/2022]
Abstract
The orally transmitted retrovirus mouse mammary tumor virus (MMTV) requires the intestinal microbiota for persistence. Virion-associated lipopolysaccharide (LPS) activates Toll-like receptor 4 (TLR4), stimulating production of the immunosuppressive cytokine IL-10 and MMTV evasion of host immunity. However, the mechanisms by which MMTV associates with LPS remain unknown. We find that the viral envelope contains the mammalian LPS-binding factors CD14, TLR4, and MD-2, which, in conjunction with LPS-binding protein (LBP), bind LPS to the virus and augment transmission. MMTV isolated from infected mice lacking these LBPs cannot engage LPS or stimulate TLR4 and have a transmission defect. Furthermore, MMTV incorporation of a weak agonist LPS from Bacteroides, a prevalent LPS source in the gut, significantly enhances the ability of this LPS to stimulate TLR4, suggesting that MMTV intensifies these immunostimulatory properties. Thus, an orally transmitted retrovirus can capture, modify, and exploit mammalian receptors for bacterial ligands to ensure successful transmission.
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Affiliation(s)
- Jessica Wilks
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA
| | - Egil Lien
- Division of Infectious Diseases and Immunology, Program in Innate Immunity, Department of Medicine, University of Massachusetts, Worcester, MA 01605, USA; Center of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
| | - Amy N Jacobson
- Department of Bioengineering and Therapeutic Sciences and California Institute of Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Michael A Fischbach
- Department of Bioengineering and Therapeutic Sciences and California Institute of Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Nilofer Qureshi
- Shock and Trauma Research Center, Medical School, University of Missouri, Kansas City, MO 64108, USA
| | | | - Tatyana V Golovkina
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA.
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432
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Abstract
Extracellular vesicles (EVs) released by various cells are small phospholipid membrane-enclosed entities that can carry miRNA. They are now central to research in many fields of biology because they seem to constitute a new system of cell-cell communication. Physical and chemical characteristics of many EVs, as well as their biogenesis pathways, resemble those of retroviruses. Moreover, EVs generated by virus-infected cells can incorporate viral proteins and fragments of viral RNA, being thus indistinguishable from defective (noninfectious) retroviruses. EVs, depending on the proteins and genetic material incorporated in them, play a significant role in viral infection, both facilitating and suppressing it. Deciphering the mechanisms of EV-cell interactions may facilitate the design of EVs that inhibit viral infection and can be used as vehicles for targeted drug delivery.
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433
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Abstract
Viruses have developed a spectrum of ways to modify cellular pathways to hijack the cell machinery for the synthesis of their nucleic acid and proteins. Similarly, they use intracellular vesicular mechanisms of trafficking for their assembly and eventual release, with a number of viruses acquiring their envelope from internal or plasma cell membranes. There is an increasing number of reports on viral exploitation of cell secretome pathways to avoid recognition and stimulation of the immune response. Extracellular vesicles (EV) containing viral particles have been shown to shield viruses after exiting the host cell, in some cases challenging the boundaries between viral groups traditionally characterised as enveloped and non-enveloped. Apart from viral particles, EV can spread the virus also carrying viral genome and can modify the target cells through their cargo of virus-coded miRNAs and proteins as well as selectively packaged cellular mRNAs, miRNAs, proteins and lipids, differing in composition and quantities from the cell of origin.
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Affiliation(s)
- Juraj Petrik
- Scottish National Blood Transfusion Service and University of Edinburgh, Edinburgh, UK.
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434
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Abstract
Hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV) are responsible for most cases of viral hepatitis. Infection by each type of virus results in a different typical natural disease course and clinical outcome that are determined by virological and immunological factors. HCV tends to establish a chronic persistent infection, whereas HAV does not. HBV is effectively controlled in adults, although it persists for a lifetime after neonatal infection. In this Review, we discuss the similarities and differences in immune responses to and immunopathogenesis of HAV, HBV and HCV infections, which may explain the distinct courses and outcomes of each hepatitis virus infection.
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435
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Update on hepatitis E virology: Implications for clinical practice. J Hepatol 2016; 65:200-212. [PMID: 26966047 DOI: 10.1016/j.jhep.2016.02.045] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 02/15/2016] [Accepted: 02/21/2016] [Indexed: 12/18/2022]
Abstract
Hepatitis E virus (HEV) is a positive-strand RNA virus transmitted by the fecal-oral route. The 7.2kb genome encodes three open reading frames (ORF) which are translated into (i) the ORF1 polyprotein, representing the viral replicase, (ii) the ORF2 protein, corresponding to the viral capsid, and (iii) the ORF3 protein, a small protein involved in particle secretion. Although HEV is a non-enveloped virus in bile and feces, it circulates in the bloodstream wrapped in cellular membranes. HEV genotypes 1 and 2 infect only humans and cause mainly waterborne outbreaks. HEV genotypes 3 and 4 are widely represented in the animal kingdom and are transmitted as a zoonosis mainly via contaminated meat. HEV infection is usually self-limited but may persist and cause chronic hepatitis in immunocompromised patients. Reduction of immunosuppressive treatment or antiviral therapy with ribavirin have proven effective in most patients with chronic hepatitis E but therapy failures have been reported. Alternative treatment options are needed, therefore. Infection with HEV may also cause a number of extrahepatic manifestations, especially neurologic complications. Progress in the understanding of the biology of HEV should contribute to improved control and treatment of HEV infection.
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436
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Abstract
Viruses have evolved many mechanisms by which to evade and subvert the immune system to ensure survival and persistence. However, for each method undertaken by the immune system for pathogen removal, there is a counteracting mechanism utilized by pathogens. The new and emerging role of microvesicles in immune intercellular communication and function is no different. Viruses across many different families have evolved to insert viral components in exosomes, a subtype of microvesicle, with many varying downstream effects. When assessed cumulatively, viral antigens in exosomes increase persistence through cloaking viral genomes, decoying the immune system, and even by increasing viral infection in uninfected cells. Exosomes therefore represent a source of viral antigen that can be used as a biomarker for disease and targeted for therapy in the control and eradication of these disorders. With the rise in the persistence of new and reemerging viruses like Ebola and Zika, exploring the role of exosomes become more important than ever.
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Affiliation(s)
- Monique R Anderson
- National Institutes of Health, National Institute of Neurological Disorders and Stroke, Neuroimmunology Branch, Viral Immunology Section, Bethesda, MD, 20892, USA.
- Department of Pathology Molecular and Cellular Basis of Disease Graduate Program, University of Virginia School of Medicine, Charlottesville, VA, 22903, USA.
| | - Fatah Kashanchi
- George Mason University, National Center for Biodefense and Infectious Disease, Laboratory of Molecular Virology, Manassas, VA, 20110, USA
| | - Steven Jacobson
- National Institutes of Health, National Institute of Neurological Disorders and Stroke, Neuroimmunology Branch, Viral Immunology Section, Bethesda, MD, 20892, USA
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437
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van Dongen HM, Masoumi N, Witwer KW, Pegtel DM. Extracellular Vesicles Exploit Viral Entry Routes for Cargo Delivery. Microbiol Mol Biol Rev 2016; 80:369-86. [PMID: 26935137 PMCID: PMC4867369 DOI: 10.1128/mmbr.00063-15] [Citation(s) in RCA: 188] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Extracellular vesicles (EVs) have emerged as crucial mediators of intercellular communication, being involved in a wide array of key biological processes. Eukaryotic cells, and also bacteria, actively release heterogeneous subtypes of EVs into the extracellular space, where their contents reflect their (sub)cellular origin and the physiologic state of the parent cell. Within the past 20 years, presumed subtypes of EVs have been given a rather confusing diversity of names, including exosomes, microvesicles, ectosomes, microparticles, virosomes, virus-like particles, and oncosomes, and these names are variously defined by biogenesis, physical characteristics, or function. The latter category, functions, in particular the transmission of biological signals between cells in vivo and how EVs control biological processes, has garnered much interest. EVs have pathophysiological properties in cancer, neurodegenerative disorders, infectious disease, and cardiovascular disease, highlighting possibilities not only for minimally invasive diagnostic applications but also for therapeutic interventions, like macromolecular drug delivery. Yet, in order to pursue therapies involving EVs and delivering their cargo, a better grasp of EV targeting is needed. Here, we review recent progress in understanding the molecular mechanisms underpinning EV uptake by receptor-ligand interactions with recipient cells, highlighting once again the overlap of EVs and viruses. Despite their highly heterogeneous nature, EVs require common viral entry pathways, and an unanticipated specificity for cargo delivery is being revealed. We discuss the challenges ahead in delineating specific roles for EV-associated ligands and cellular receptors.
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Affiliation(s)
- Helena M van Dongen
- Department of Pathology, Exosomes Research Group, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Niala Masoumi
- Department of Pathology, Exosomes Research Group, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Kenneth W Witwer
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - D Michiel Pegtel
- Department of Pathology, Exosomes Research Group, Cancer Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
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438
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Altan-Bonnet N. Extracellular vesicles are the Trojan horses of viral infection. Curr Opin Microbiol 2016; 32:77-81. [PMID: 27232382 DOI: 10.1016/j.mib.2016.05.004] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 05/03/2016] [Indexed: 02/06/2023]
Abstract
Extracellular vesicles have recently emerged as a novel mode of viral propagation exploited by both enveloped and non-enveloped viruses. In particular non-enveloped viruses utilize the hosts' production of extracellular vesicles to exit from cells non-lytically and to hide and manipulate the immune system. Moreover, challenging the long held idea that viruses behave as independent genetic units, extracellular vesicles enable multiple viral particles and genomes to collectively traffic in and out of cells, which can promote genetic cooperativity among viral quasispecies and enhance the fitness of the overall viral population.
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Affiliation(s)
- Nihal Altan-Bonnet
- Laboratory of Host-Pathogen Dynamics, Cell Biology and Physiology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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439
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Late Maturation Steps Preceding Selective Nuclear Export and Egress of Progeny Parvovirus. J Virol 2016; 90:5462-74. [PMID: 27009963 DOI: 10.1128/jvi.02967-15] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 03/17/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Although the mechanism is not well understood, growing evidence indicates that the nonenveloped parvovirus minute virus of mice (MVM) may actively egress before passive release through cell lysis. We have dissected the late maturation steps of the intranuclear progeny with the aims of confirming the existence of active prelytic egress and identifying critical capsid rearrangements required to initiate the process. By performing anion-exchange chromatography (AEX), we separated intranuclear progeny particles by their net surface charges. Apart from empty capsids (EC), two distinct populations of full capsids (FC) arose in the nuclei of infected cells. The earliest population of FC to appear was infectious but, like EC, could not be actively exported from the nucleus. Further maturation of this early population, involving the phosphorylation of surface residues, gave rise to a second, late population with nuclear export potential. While capsid surface phosphorylation was strictly associated with nuclear export capacity, mutational analysis revealed that the phosphoserine-rich N terminus of VP2 (N-VP2) was dispensable, although it contributed to passive release. The reverse situation was observed for the incoming particles, which were dephosphorylated in the endosomes. Our results confirm the existence of active prelytic egress and reveal a late phosphorylation event occurring in the nucleus as a selective factor for initiating the process. IMPORTANCE In general, the process of egress of enveloped viruses is active and involves host cell membranes. However, the release of nonenveloped viruses seems to rely more on cell lysis. At least for some nonenveloped viruses, an active process before passive release by cell lysis has been reported, although the underlying mechanism remains poorly understood. By using the nonenveloped model parvovirus minute virus of mice, we could confirm the existence of an active process of nuclear export and further characterize the associated capsid maturation steps. Following DNA packaging in the nucleus, capsids required further modifications, involving the phosphorylation of surface residues, to acquire nuclear export potential. Inversely, those surface residues were dephosphorylated on entering capsids. These spatially controlled phosphorylation-dephosphorylation events concurred with the nuclear export-import potential required to complete the infectious cycle.
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440
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The Large Marseillevirus Explores Different Entry Pathways by Forming Giant Infectious Vesicles. J Virol 2016; 90:5246-55. [PMID: 26984730 DOI: 10.1128/jvi.00177-16] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 03/10/2016] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Triggering the amoebal phagocytosis process is a sine qua non condition for most giant viruses to initiate their replication cycle and consequently to promote their progeny formation. It is well known that the amoebal phagocytosis process requires the recognition of particles of >500 nm, and most amoebal giant viruses meet this requirement, such as mimivirus, pandoravirus, pithovirus, and mollivirus. However, in the context of the discovery of amoebal giant viruses in the last decade, Marseillevirus marseillevirus (MsV) has drawn our attention, because despite its ability to successfully replicate in Acanthamoeba, remarkably it does not fulfill the >500-nm condition, since it presents an ∼250-nm icosahedrally shaped capsid. We deeply investigated the MsV cycle by using a set of methods, including virological, molecular, and microscopic (immunofluorescence, scanning electron microscopy, and transmission electron microscopy) assays. Our results revealed that MsV is able to form giant vesicles containing dozens to thousands of viral particles wrapped by membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggested that these giant vesicles are able to stimulate amoebal phagocytosis and to trigger the MsV replication cycle by an acidification-independent process. Also, we observed that MsV entry may occur by the phagocytosis of grouped particles (without surrounding membranes) and by an endosome-stimulated pathway triggered by single particles. Taken together, not only do our data deeply describe the main features of MsV replication cycle, but this is the first time, to our knowledge, that the formation of giant infective vesicles related to a DNA virus has been described. IMPORTANCE Triggering the amoebal phagocytosis process is a sine qua non condition required by most giant viruses to initiate their replication cycle. This process requires the recognition of particles of >500 nm, and many giant viruses meet this requirement. However, MsV is unusual, as despite having particles of ∼250 nm it is able to replicate in Acanthamoeba Our results revealed that MsV is able to form giant vesicles, containing dozens to thousands of viral particles, wrapped in membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggest that these giant vesicles are able to stimulate phagocytosis using an acidification-independent process. Our work not only describes the main features of the MsV replication cycle but also describes, for the first time to our knowledge, the formation of huge infective vesicles in a large DNA viruses.
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441
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Evans GL, Caller LG, Foster V, Crump CM. Anion homeostasis is important for non-lytic release of BK polyomavirus from infected cells. Open Biol 2016; 5:rsob.150041. [PMID: 26246492 PMCID: PMC4554916 DOI: 10.1098/rsob.150041] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BK polyomavirus (BKPyV) is a member of a family of potentially oncogenic viruses, whose reactivation can cause severe pathological conditions in transplant patients, leading to graft rejection. As with many non-enveloped viruses, it is assumed that virus release occurs through lysis of the host cell. We now show the first evidence for a non-lytic release pathway for BKPyV and that this pathway can be blocked by the anion channel inhibitor DIDS. Our data show a dose-dependent effect of DIDS on the release of BKPyV virions. We also observed an accumulation of viral capsids in large LAMP-1-positive acidic organelles within the cytoplasm of cells upon DIDS treatment, suggesting potential late endosome or lysosome-related compartments are involved in non-lytic BKPyV release. These data highlight a novel mechanism by which polyomaviruses can be released from infected cells in an active and non-lytic manner, and that anion homeostasis regulation is important in this pathway.
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Affiliation(s)
- Gareth L Evans
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Laura G Caller
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Victoria Foster
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Colin M Crump
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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442
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Viruses exploit the tissue physiology of the host to spread in vivo. Curr Opin Cell Biol 2016; 41:81-90. [PMID: 27149407 DOI: 10.1016/j.ceb.2016.04.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 04/11/2016] [Accepted: 04/20/2016] [Indexed: 02/07/2023]
Abstract
Viruses are pathogens that strictly depend on their host for propagation. Over years of co-evolution viruses have become experts in exploiting the host cell biology and physiology to ensure efficient replication and spread. Here, we will first summarize the concepts that have emerged from in vitro cell culture studies to understand virus spread. We will then review the results from studies in living animals that reveal how viruses exploit the natural flow of body fluids, specific tissue architecture, and patterns of cell circulation and migration to spread within the host. Understanding tissue physiology will be critical for the design of antiviral strategies that prevent virus dissemination.
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443
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Gouttenoire J, Moradpour D. A mouse model for hepatitis E virus infection. J Hepatol 2016; 64:1003-1005. [PMID: 26892936 DOI: 10.1016/j.jhep.2016.02.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 02/08/2016] [Indexed: 12/04/2022]
Affiliation(s)
- Jérôme Gouttenoire
- Division of Gastroenterology and Hepatology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
| | - Darius Moradpour
- Division of Gastroenterology and Hepatology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
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444
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Kalamvoki M, Deschamps T. Extracellular vesicles during Herpes Simplex Virus type 1 infection: an inquire. Virol J 2016; 13:63. [PMID: 27048572 PMCID: PMC4822280 DOI: 10.1186/s12985-016-0518-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 03/29/2016] [Indexed: 12/21/2022] Open
Abstract
Extracellular vesicles are defined as a heterogeneous group of vesicles that are released by prokaryotic to higher eukaryotic cells and by plant cells in an evolutionary conserved manner. The significance of these vesicles lies in their capacity to transfer selected cargo composed of proteins, lipids and nucleic acids to both recipient and parent cells and to influence various physiological and pathological functions. Microorganisms such as parasites, fungi and protozoa and even single cell organisms such as bacteria generate extracellular vesicles. In addition, several viruses have evolved strategies to hijack the extracellular vesicles for egress or to alter the surrounding environment. The thesis of this article is that: a) during HSV-1 infection vesicles are delivered from infected to uninfected cells that influence the infection; b) the cargo of these vesicles consists of viral and host transcripts (mRNAs, miRNAs and non-coding RNAs) and proteins including innate immune components, such as STING; and c) the viral vesicles carry the tetraspanins CD9, CD63 and CD81, which are considered as markers of exosomes. Therefore, we assume that the STING-carrying vesicles, produced during HSV-1 infection, are reminiscent to exosomes. The presumed functions of the exosomes released from HSV-1 infected cells include priming the recipient cells and accelerating antiviral responses to control the dissemination of the virus. This may be one strategy used by the virus to prevent the elimination by the host and establish persistent infection. In conclusion, the modification of the cargo of exosomes appears to be part of the strategy that HSV-1 has evolved to establish lifelong persistent infections into the human body to ensure successful dissemination between individuals.
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Affiliation(s)
- Maria Kalamvoki
- Department Microbiology, Molecular Genetics Immunology, University of Kansas Medical Center, 3901 Rainbow Blvd, Building Hixon, room 3009, Kansas City, KS, 66160, USA.
| | - Thibaut Deschamps
- Department Microbiology, Molecular Genetics Immunology, University of Kansas Medical Center, 3901 Rainbow Blvd, Building Hixon, room 3009, Kansas City, KS, 66160, USA
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445
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Abstract
Why some viruses are enveloped while others lack an outer lipid bilayer is a major question in viral evolution but one that has received relatively little attention. The viral envelope serves several functions, including protecting the RNA or DNA molecule(s), evading recognition by the immune system, and facilitating virus entry. Despite these commonalities, viral envelopes come in a wide variety of shapes and configurations. The evolution of the viral envelope is made more puzzling by the fact that nonenveloped viruses are able to infect a diverse range of hosts across the tree of life. We reviewed the entry, transmission, and exit pathways of all (101) viral families on the 2013 International Committee on Taxonomy of Viruses (ICTV) list. By doing this, we revealed a strong association between the lack of a viral envelope and the presence of a cell wall in the hosts these viruses infect. We were able to propose a new hypothesis for the existence of enveloped and nonenveloped viruses, in which the latter represent an adaptation to cells surrounded by a cell wall, while the former are an adaptation to animal cells where cell walls are absent. In particular, cell walls inhibit viral entry and exit, as well as viral transport within an organism, all of which are critical waypoints for successful infection and spread. Finally, we discuss how this new model for the origin of the viral envelope impacts our overall understanding of virus evolution.
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446
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Zappulli V, Friis KP, Fitzpatrick Z, Maguire CA, Breakefield XO. Extracellular vesicles and intercellular communication within the nervous system. J Clin Invest 2016; 126:1198-207. [PMID: 27035811 DOI: 10.1172/jci81134] [Citation(s) in RCA: 169] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Extracellular vesicles (EVs, including exosomes) are implicated in many aspects of nervous system development and function, including regulation of synaptic communication, synaptic strength, and nerve regeneration. They mediate the transfer of packets of information in the form of nonsecreted proteins and DNA/RNA protected within a membrane compartment. EVs are essential for the packaging and transport of many cell-fate proteins during development as well as many neurotoxic misfolded proteins during pathogenesis. This form of communication provides another dimension of cellular crosstalk, with the ability to assemble a "kit" of directional instructions made up of different molecular entities and address it to specific recipient cells. This multidimensional form of communication has special significance in the nervous system. How EVs help to orchestrate the wiring of the brain while allowing for plasticity associated with learning and memory and contribute to regeneration and degeneration are all under investigation. Because they carry specific disease-related RNAs and proteins, practical applications of EVs include potential uses as biomarkers and therapeutics. This Review describes our current understanding of EVs and serves as a springboard for future advances, which may reveal new important mechanisms by which EVs in coordinate brain and body function and dysfunction.
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447
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Pitt JM, Kroemer G, Zitvogel L. Extracellular vesicles: masters of intercellular communication and potential clinical interventions. J Clin Invest 2016; 126:1139-43. [PMID: 27035805 DOI: 10.1172/jci87316] [Citation(s) in RCA: 344] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Intercellular signaling via extracellular vesicles (EVs) is an underappreciated modality of cell-cell crosstalk that enables cells to convey packages of complex instructions to specific recipient cells. EVs transmit these instructions through their cargoes of multiple proteins, nucleic acids, and specialized lipids, which are derived from their cells of origin and allow for combinatorial effects upon recipient cells. This Review series brings together the recent progress in our understanding of EV signaling in physiological and pathophysiological conditions, highlighting how certain EVs, particularly exosomes, can promote or regulate infections, host immune responses, development, and various diseases - notably cancer. Given the diverse nature of EVs and their abilities to profoundly modulate host cells, this series puts particular emphasis on the clinical applications of EVs as therapeutics and as diagnostic biomarkers.
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448
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Yamauchi Y, Greber UF. Principles of Virus Uncoating: Cues and the Snooker Ball. Traffic 2016; 17:569-92. [PMID: 26875443 PMCID: PMC7169695 DOI: 10.1111/tra.12387] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/10/2016] [Accepted: 02/10/2016] [Indexed: 12/17/2022]
Abstract
Viruses are spherical or complex shaped carriers of proteins, nucleic acids and sometimes lipids and sugars. They are metastable and poised for structural changes. These features allow viruses to communicate with host cells during entry, and to release the viral genome, a process known as uncoating. Studies have shown that hundreds of host factors directly or indirectly support this process. The cell provides molecules that promote stepwise virus uncoating, and direct the virus to the site of replication. It acts akin to a snooker player who delivers accurate and timely shots (cues) to the ball (virus) to score. The viruses, on the other hand, trick (snooker) the host, hijack its homeostasis systems, and dampen innate immune responses directed against danger signals. In this review, we discuss how cellular cues, facilitators, and built‐in viral mechanisms promote uncoating. Cues come from receptors, enzymes and chemicals that act directly on the virus particle to alter its structure, trafficking and infectivity. Facilitators are defined as host factors that are involved in processes which indirectly enhance entry or uncoating. Unraveling the mechanisms of virus uncoating will continue to enhance understanding of cell functions, and help counteracting infections with chemicals and vaccines.
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Affiliation(s)
- Yohei Yamauchi
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Urs F Greber
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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449
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Distinct Entry Mechanisms for Nonenveloped and Quasi-Enveloped Hepatitis E Viruses. J Virol 2016; 90:4232-4242. [PMID: 26865708 DOI: 10.1128/jvi.02804-15] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Accepted: 02/04/2016] [Indexed: 12/16/2022] Open
Abstract
UNLABELLED The hepatitis E virus (HEV) sheds into feces as nonenveloped virions but circulates in the blood in a membrane-associated, quasi-enveloped form (eHEV). Since the eHEV virions lack viral proteins on the surface, we investigated the entry mechanism for eHEV. We found that compared to nonenveloped HEV virions, eHEV attachment to the cell was much less efficient, requiring a longer inoculation time to reach its maximal infectivity. A survey of cellular internalization pathways identified clathrin-mediated endocytosis as the main route for eHEV entry. Unlike nonenveloped HEV virions, eHEV entry requires Rab5 and Rab7, small GTPases involved in endosomal trafficking, and blocking endosomal acidification abrogated eHEV infectivity. However, low pH alone was not sufficient for eHEV uncoating, suggesting that additional steps are required for entry. Supporting this concept, eHEV infectivity was substantially reduced in cells depleted of Niemann-Pick disease type C1, a lysosomal protein required for cholesterol extraction from lipid, or in cells treated with an inhibitor of lysosomal acid lipase. These data support a model in which the quasi-envelope is degraded within the lysosome prior to virus uncoating, a potentially novel mechanism for virus entry. IMPORTANCE The recent discovery of quasi-enveloped viruses has shifted the paradigm of virus-host interactions. The impact of quasi-envelopment in the virus life cycle and pathogenesis is largely unknown. HEV is a highly relevant model to study these questions. HEV circulates as quasi-enveloped virions in the blood that are hidden from neutralizing antibodies. eHEV particles most likely are responsible for the cell-to-cell spread of the virus. Given the increasing concerns about persistent HEV infection and its potential for transmission via the blood supply, understanding how eHEV infects cells is important for understanding its pathogenesis and developing therapies. Our data provide evidence that eHEV uses a potentially novel mechanism for cellular entry. Several steps critical to eHEV entry were identified and may provide a basis for developing treatments for hepatitis E. Because quasi-enveloped viruses resemble exosomes, these data also may provide insights into the exosome-mediated intercellular communications.
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450
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Fat(al) attraction: Picornaviruses Usurp Lipid Transfer at Membrane Contact Sites to Create Replication Organelles. Trends Microbiol 2016; 24:535-546. [PMID: 27020598 PMCID: PMC7126954 DOI: 10.1016/j.tim.2016.02.017] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/23/2016] [Accepted: 02/25/2016] [Indexed: 12/23/2022]
Abstract
All viruses that carry a positive-sense RNA genome (+RNA), such as picornaviruses, hepatitis C virus, dengue virus, and SARS- and MERS-coronavirus, confiscate intracellular membranes of the host cell to generate new compartments (i.e., replication organelles) for amplification of their genome. Replication organelles (ROs) are membranous structures that not only harbor viral proteins but also contain a specific array of hijacked host factors that create a unique lipid microenvironment optimal for genome replication. While some lipids may be locally synthesized de novo, other lipids are shuttled towards ROs. In picornavirus-infected cells, lipids are exchanged at membrane contact sites between ROs and other organelles. In this paper, we review recent advances in our understanding of how picornaviruses exploit host membrane contact site machinery to generate ROs, a mechanism that is used by some other +RNA viruses as well. Picornaviruses create replication organelles with a unique protein and lipid composition to amplify their genome. Picornaviruses hijack membrane contact site machinery to shuttle lipids to their replication organelles. Picornaviruses from different genera employ a cholesterol/PI4P counterflux mechanism to accumulate cholesterol at replication organelles.
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