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Hogan V, Johnson WE. Unique Structure and Distinctive Properties of the Ancient and Ubiquitous Gamma-Type Envelope Glycoprotein. Viruses 2023; 15:v15020274. [PMID: 36851488 PMCID: PMC9967133 DOI: 10.3390/v15020274] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/13/2023] [Accepted: 01/15/2023] [Indexed: 01/20/2023] Open
Abstract
After the onset of the AIDS pandemic, HIV-1 (genus Lentivirus) became the predominant model for studying retrovirus Env glycoproteins and their role in entry. However, HIV Env is an inadequate model for understanding entry of viruses in the Alpharetrovirus, Gammaretrovirus and Deltaretrovirus genera. For example, oncogenic model system viruses such as Rous sarcoma virus (RSV, Alpharetrovirus), murine leukemia virus (MLV, Gammaretrovirus) and human T-cell leukemia viruses (HTLV-I and HTLV-II, Deltaretrovirus) encode Envs that are structurally and functionally distinct from HIV Env. We refer to these as Gamma-type Envs. Gamma-type Envs are probably the most widespread retroviral Envs in nature. They are found in exogenous and endogenous retroviruses representing a broad spectrum of vertebrate hosts including amphibians, birds, reptiles, mammals and fish. In endogenous form, gamma-type Envs have been evolutionarily coopted numerous times, most notably as placental syncytins (e.g., human SYNC1 and SYNC2). Remarkably, gamma-type Envs are also found outside of the Retroviridae. Gp2 proteins of filoviruses (e.g., Ebolavirus) and snake arenaviruses in the genus Reptarenavirus are gamma-type Env homologs, products of ancient recombination events involving viruses of different Baltimore classes. Distinctive hallmarks of gamma-type Envs include a labile disulfide bond linking the surface and transmembrane subunits, a multi-stage attachment and fusion mechanism, a highly conserved (but poorly understood) "immunosuppressive domain", and activation by the viral protease during virion maturation. Here, we synthesize work from diverse retrovirus model systems to illustrate these distinctive properties and to highlight avenues for further exploration of gamma-type Env structure and function.
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Goldstein T, Anthony SJ, Gbakima A, Bird BH, Bangura J, Tremeau-Bravard A, Belaganahalli MN, Wells HL, Dhanota JK, Liang E, Grodus M, Jangra RK, DeJesus VA, Lasso G, Smith BR, Jambai A, Kamara BO, Kamara S, Bangura W, Monagin C, Shapira S, Johnson CK, Saylors K, Rubin EM, Chandran K, Lipkin WI, Mazet JAK. The discovery of Bombali virus adds further support for bats as hosts of ebolaviruses. Nat Microbiol 2018; 3:1084-1089. [PMID: 30150734 PMCID: PMC6557442 DOI: 10.1038/s41564-018-0227-2] [Citation(s) in RCA: 211] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 07/25/2018] [Indexed: 11/08/2022]
Abstract
Here we describe the complete genome of a new ebolavirus, Bombali virus (BOMV) detected in free-tailed bats in Sierra Leone (little free-tailed (Chaerephon pumilus) and Angolan free-tailed (Mops condylurus)). The bats were found roosting inside houses, indicating the potential for human transmission. We show that the viral glycoprotein can mediate entry into human cells. However, further studies are required to investigate whether exposure has actually occurred or if BOMV is pathogenic in humans.
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Affiliation(s)
- Tracey Goldstein
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA.
| | - Simon J Anthony
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA.
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA.
- EcoHealth Alliance, New York, NY, USA.
| | - Aiah Gbakima
- Metabiota, Inc. Sierra Leone, Freetown, Sierra Leone
| | - Brian H Bird
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - James Bangura
- Metabiota, Inc. Sierra Leone, Freetown, Sierra Leone
| | - Alexandre Tremeau-Bravard
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Manjunatha N Belaganahalli
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Heather L Wells
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Jasjeet K Dhanota
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Eliza Liang
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA
- EcoHealth Alliance, New York, NY, USA
| | - Michael Grodus
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Rohit K Jangra
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Veronica A DeJesus
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Gorka Lasso
- Department of Systems Biology, Irving Cancer Research Center, Columbia University, New York, NY, USA
| | - Brett R Smith
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Amara Jambai
- Ministry of Health and Sanitation, Freetown, Sierra Leone
| | | | - Sorie Kamara
- Livestock and Veterinary Services Division, Ministry of Agriculture, Forestry and Food Security, Freetown, Sierra Leone
| | - William Bangura
- Forestry and Wildlife Division, Ministry of Agriculture, Forestry and Food Security, Freetown, Sierra Leone
| | - Corina Monagin
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
- Metabiota, Inc., San Francisco, CA, USA
| | - Sagi Shapira
- Department of Systems Biology, Irving Cancer Research Center, Columbia University, New York, NY, USA
- Department of Microbiology & Immunology, Columbia University, New York, NY, USA
| | - Christine K Johnson
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
| | | | | | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - W Ian Lipkin
- Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Jonna A K Mazet
- One Health Institute & Karen C. Drayer Wildlife Health Center, School of Veterinary Medicine, University of California, Davis, CA, USA
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Sizikova TE, Lebedev VN, Karulina NV, Borisevich SV. LLOVIU VIRUS - A NOVEL FILOVIRUS, ENDEMIC IN EUROPE. Vopr Virusol 2018; 63:58-61. [PMID: 36494922 DOI: 10.18821/0507-4088-2018-63-2-58-61] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Indexed: 12/13/2022]
Abstract
The data on a recently revealed novel filovirus (Lloviu virus, family Filoviridae, genera Cuevavirus) in Europe are viewed in this issue. The molecular-biological properties of genome fragments of Lloviu virus were isolated from perished bats (Miniopterus sсhreibersii). Because infectious Lloviu virus has not been isolated yet, the capacity of virus to infect cells of different species and its potential to cause disease in humans is unclear. The recombinant vectors (vesicular stomatitis virus and plasmids) expressing structural proteins of Lloviu virus were used to study different elements of the virus. The question of interaction of structural proteins of Lloviu virus expressed by recombinant vectors with receptors of bat and human cells is considered. The possibility of pathogenicity of the novel agent for humans is considered. The conclusion is made about the necessity of continuous epidemical and epizootical monitoring of the new filovirus infection.
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4
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Filovirus proteins for antiviral drug discovery: Structure/function of proteins involved in assembly and budding. Antiviral Res 2018; 150:183-192. [DOI: 10.1016/j.antiviral.2017.12.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 12/20/2017] [Accepted: 12/28/2017] [Indexed: 01/30/2023]
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Abstract
The Filoviridae are a family of negative-strand RNA viruses that include several important human pathogens. Ebola virus (EBOV) and Marburg virus are well-known filoviruses which cause life-threatening viral hemorrhagic fever in human and nonhuman primates. In addition to severe pathogenesis, filoviruses also exhibit a propensity for human-to-human transmission by close contact, posing challenges to containment and crisis management. Past outbreaks, in particular the recent West African EBOV epidemic, have been responsible for thousands of deaths and vaulted the filoviruses into public consciousness. Both national and international health agencies continue to regard potential filovirus outbreaks as critical threats to global public health. To develop effective countermeasures, a basic understanding of filovirus biology is needed. This review encompasses the epidemiology, ecology, molecular biology, and evolution of the filoviruses.
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Affiliation(s)
- Jackson Emanuel
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States
| | - Andrea Marzi
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States
| | - Heinz Feldmann
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States.
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Proteolytic Processing of Filovirus Glycoproteins. ACTIVATION OF VIRUSES BY HOST PROTEASES 2018. [PMCID: PMC7122482 DOI: 10.1007/978-3-319-75474-1_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Filoviruses (Marburg virus and Ebola virus) have a single envelope glycoprotein (GP) that initiates infection. GP is a class I fusion protein that forms trimeric spikes composed of heterodimers of the subunits GP1 and GP2. GP1 and GP2 are derived from the precursor pre-GP by furin cleavage during exocytosis. GP1 contains a receptor-binding core topped by a glycan cap and a heavily glycosylated mucin-like domain, while GP2 contains a fusion loop and a membrane anchor. After entering cells by macropinocytosis, the glycan cap and the mucin-like domain are removed from GP1 by endosomal cathepsins B and L exposing the binding site for the Niemann-Pick C1 receptor. It appears that there is no strict requirement for specific proteases involved in GP processing. Thus, furin is not indispensible for GP1-2 cleavage, and GP1 may be trimmed not only by cathepsins B and L but also by other endosomal proteases. Two soluble glycoproteins of Ebola virus are also processed by host proteases. A significant amount of GP1,2 is cleaved by the metalloprotease TACE and shed from the surface of infected cells (GP1,2 delta). The secreted protein sGP is derived from the precursor pre-sGP by furin cleavage.
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Blinov VM, Zverev VV, Krasnov GS, Filatov FP, Shargunov AV. Viral component of the human genome. Mol Biol 2017; 51:205-215. [PMID: 32214476 PMCID: PMC7089383 DOI: 10.1134/s0026893317020066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 04/27/2016] [Indexed: 12/17/2022]
Abstract
Relationships between viruses and their human host are traditionally described from the point of view taking into consideration hosts as victims of viral aggression, which results in infectious diseases. However, these relations are in fact two-sided and involve modifications of both the virus and host genomes. Mutations that accumulate in the populations of viruses and hosts may provide them advantages such as the ability to overcome defense barriers of host cells or to create more efficient barriers to deal with the attack of the viral agent. One of the most common ways of reinforcing anti-viral barriers is the horizontal transfer of viral genes into the host genome. Within the host genome, these genes may be modified and extensively expressed to compete with viral copies and inhibit the synthesis of their products or modulate their functions in other ways. This review summarizes the available data on the horizontal gene transfer between viral and human genomes and discusses related problems.
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Affiliation(s)
- V M Blinov
- 1Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064 Russia
| | - V V Zverev
- 1Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064 Russia
| | - G S Krasnov
- 1Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064 Russia.,2Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 111911 Russia.,3Orekhovich Research Institute of Biomedical Chemistry, Moscow, 119121 Russia
| | - F P Filatov
- 1Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064 Russia.,Gamaleya Research Center of Epidemiology and Microbiology, Moscow, 123098 Russia
| | - A V Shargunov
- 1Mechnikov Research Institute of Vaccines and Sera, Moscow, 105064 Russia
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Groseth A, Hoenen T. Forty Years of Ebolavirus Molecular Biology: Understanding a Novel Disease Agent Through the Development and Application of New Technologies. Methods Mol Biol 2017; 1628:15-38. [PMID: 28573608 DOI: 10.1007/978-1-4939-7116-9_2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Molecular biology is a broad discipline that seeks to understand biological phenomena at a molecular level, and achieves this through the study of DNA, RNA, proteins, and/or other macromolecules (e.g., those involved in the modification of these substrates). Consequently, it relies on the availability of a wide variety of methods that deal with the collection, preservation, inactivation, separation, manipulation, imaging, and analysis of these molecules. As such the state of the art in the field of ebolavirus molecular biology research (and that of all other viruses) is largely intertwined with, if not driven by, advancements in the technical methodologies available for these kinds of studies. Here we review of the current state of our knowledge regarding ebolavirus biology and emphasize the associated methods that made these discoveries possible.
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Affiliation(s)
- Allison Groseth
- Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany.
| | - Thomas Hoenen
- Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
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Ning YJ, Deng F, Hu Z, Wang H. The roles of ebolavirus glycoproteins in viral pathogenesis. Virol Sin 2016; 32:3-15. [PMID: 27853993 PMCID: PMC6791933 DOI: 10.1007/s12250-016-3850-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 10/09/2016] [Indexed: 12/20/2022] Open
Abstract
Ebolaviruses are highly dangerous pathogens exhibiting extreme virulence in humans and nonhuman primates. The majority of ebolavirus species, most notably Zaire ebolavirus, can cause Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, in humans. EVD is associated with case-fatality rates as high as 90%, and there is currently no specific treatment or licensed vaccine available against EVD. Understanding the molecular biology and pathogenesis of ebolaviruses is important for the development of antiviral therapeutics. Ebolavirus encodes several forms of glycoproteins (GPs), which have some interesting characteristics, including the transcriptional editing coding strategy and extensive O-glycosylation modification, clustered in the mucin-like domain of GP1, full-length GP (GP1,2), and shed GP. In addition to the canonical role of the spike protein, GP1,2, in viral entry, ebolavirus GPs appear to have multiple additional functions, likely contributing to the complex pathogenesis of the virus. Here, we review the roles of ebolavirus GPs in viral pathogenesis.
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Affiliation(s)
- Yun-Jia Ning
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Fei Deng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Zhihong Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Hualin Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
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El Sayed SM, Abdelrahman AA, Ozbak HA, Hemeg HA, Kheyami AM, Rezk N, El-Ghoul MB, Nabo MMH, Fathy YM. Updates in diagnosis and management of Ebola hemorrhagic fever. JOURNAL OF RESEARCH IN MEDICAL SCIENCES 2016; 21:84. [PMID: 28163730 PMCID: PMC5244689 DOI: 10.4103/1735-1995.192500] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/22/2016] [Accepted: 05/01/2016] [Indexed: 12/13/2022]
Abstract
Ebola hemorrhagic fever is a lethal viral disease transmitted by contact with infected people and animals. Ebola infection represents a worldwide health threat causing enormous mortality rates and fatal epidemics. Major concern is pilgrimage seasons with possible transmission to Middle East populations. In this review, we aim to shed light on Ebola hemorrhagic fever as regard: virology, transmission, biology, pathogenesis, clinical picture, and complications to get the best results for prevention and management. We also aim to guide future research to new therapeutic perspectives to precise targets. Our methodology was to review the literature extensively to make an overall view of the biology of Ebola virus infection, its serious health effects and possible therapeutic benefits using currently available remedies and future perspectives. Key findings in Ebola patients are fever, hepatic impairment, hepatocellular necrosis, lymphopenia (for T-lymphocyte and natural killer cells) with lymphocyte apoptosis, hemorrhagic manifestations, and complications. Pathogenesis in Ebola infection includes oxidative stress, immune suppression of both cell-mediated and humoral immunities, hepatic and adrenal impairment and failure, hemorrhagic fever, activation of deleterious inflammatory pathways, for example, tumor necrosis factor-related apoptosis-inducing ligand, and factor of apoptotic signal death receptor pathways causing lymphocyte depletion. Several inflammatory mediators and cytokines are involved in pathogenesis, for example, interleukin-2, 6, 8, and 10 and others. In conclusion, Ebola hemorrhagic fever is a serious fatal viral infection that can be prevented using strict health measures and can be treated to some extent using some currently available remedies. Newer treatment lines, for example, prophetic medicine remedies as nigella sativa may be promising.
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Affiliation(s)
- Salah Mohamed El Sayed
- Department of Clinical Biochemistry and Molecular Medicine, Taibah College of Medicine, Taibah University, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia; Department of Clinical Biochemistry, Sohag Faculty of Medicine, Sohag University, Sohag, Egypt
| | - Ali A Abdelrahman
- Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Hani Adnan Ozbak
- Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Hassan Abdullah Hemeg
- Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Ali Mohammed Kheyami
- Molecular Virology Unit, Central Laboratories and Blood Bank, Directorate of Health, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Nasser Rezk
- Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Mohamed Baioumy El-Ghoul
- Department of Medicine, Uhud General Hospital, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
| | - Manal Mohamed Helmy Nabo
- Department of Pediatrics, Sohag Teaching Hospital, Sohag, Egypt; Department of Pediatrics, Division of Pediatric Cardiology, Maternity and Children Hospital, King Abdullah Medical City, Al-Madinah Al-Munawwarah, Kingdom of Saudi Arabia
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Denner J. Treatment of Ebola virus infections with inhibitors of TLR4. Med Hypotheses 2015; 85:253-7. [PMID: 26003830 DOI: 10.1016/j.mehy.2015.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 05/04/2015] [Accepted: 05/10/2015] [Indexed: 01/25/2023]
Abstract
Ebola virus (EBOV) infection is associated with modulation of cytokine expression in infected patients. EBOV has been shown to interact directly with immune cells (at minimum with macrophages and dendritic cells) and modulation of cytokine expression has also been observed in vitro, which is similar to that in vivo. The modulation of cytokine expression observed in vitro was independent of virus infection and the glycoprotein GP1,2 was shown to be necessary and sufficient for cytokine modulation. Interestingly, similar changes in gene expression were observed in cells treated with lipopolysaccharide (LPS). As evidence suggests that GP1,2 and LPS use the same receptor, it is tempting to evaluate whether compounds that can inhibit signal transduction by LPS, e.g., TAK-242, can also reduce EBOV-induced pathogenesis.
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12
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Gallaher WR, Garry RF. Modeling of the Ebola virus delta peptide reveals a potential lytic sequence motif. Viruses 2015; 7:285-305. [PMID: 25609303 PMCID: PMC4306839 DOI: 10.3390/v7010285] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/12/2015] [Accepted: 01/16/2015] [Indexed: 12/24/2022] Open
Abstract
Filoviruses, such as Ebola and Marburg viruses, cause severe outbreaks of human infection, including the extensive epidemic of Ebola virus disease (EVD) in West Africa in 2014. In the course of examining mutations in the glycoprotein gene associated with 2014 Ebola virus (EBOV) sequences, a differential level of conservation was noted between the soluble form of glycoprotein (sGP) and the full length glycoprotein (GP), which are both encoded by the GP gene via RNA editing. In the region of the proteins encoded after the RNA editing site sGP was more conserved than the overlapping region of GP when compared to a distant outlier species, Tai Forest ebolavirus. Half of the amino acids comprising the “delta peptide”, a 40 amino acid carboxy-terminal fragment of sGP, were identical between otherwise widely divergent species. A lysine-rich amphipathic peptide motif was noted at the carboxyl terminus of delta peptide with high structural relatedness to the cytolytic peptide of the non-structural protein 4 (NSP4) of rotavirus. EBOV delta peptide is a candidate viroporin, a cationic pore-forming peptide, and may contribute to EBOV pathogenesis.
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Affiliation(s)
- William R Gallaher
- Mockingbird Nature Research Group, PO Box 568, Pearl River, LA 70452, USA.
| | - Robert F Garry
- Department of Microbiology and Immunology, Tulane University Medical Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
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Less is more: Ebola virus surface glycoprotein expression levels regulate virus production and infectivity. J Virol 2014; 89:1205-17. [PMID: 25392212 DOI: 10.1128/jvi.01810-14] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
UNLABELLED The Ebola virus (EBOV) surface glycoprotein (GP1,2) mediates host cell attachment and fusion and is the primary target for host neutralizing antibodies. Expression of GP1,2 at high levels disrupts normal cell physiology, and EBOV uses an RNA-editing mechanism to regulate expression of the GP gene. In this study, we demonstrate that high levels of GP1,2 expression impair production and release of EBOV virus-like particles (VLPs) as well as infectivity of GP1,2-pseudotyped viruses. We further show that this effect is mediated through two mechanisms. First, high levels of GP1,2 expression reduce synthesis of other proteins needed for virus assembly. Second, viruses containing high levels of GP1,2 are intrinsically less infectious, possibly due to impaired receptor binding or endosomal processing. Importantly, proteolysis can rescue the infectivity of high-GP1,2-containing viruses. Taken together, our findings indicate that GP1,2 expression levels have a profound effect on factors that contribute to virus fitness and that RNA editing may be an important mechanism employed by EBOV to regulate GP1,2 expression in order to optimize virus production and infectivity. IMPORTANCE The Ebola virus (EBOV), as well as other members of the Filoviridae family, causes severe hemorrhagic fever that is highly lethal, with up to 90% mortality. The EBOV surface glycoprotein (GP1,2) plays important roles in virus infection and pathogenesis, and its expression is tightly regulated by an RNA-editing mechanism during virus replication. Our study demonstrates that the level of GP1,2 expression profoundly affects virus particle production and release and uncovers a new mechanism by which Ebola virus infectivity is regulated by the level of GP1,2 expression. These findings extend our understanding of EBOV infection and replication in adaptation of host environments, which will aid the development of countermeasures against EBOV infection.
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Misasi J, Sullivan NJ. Camouflage and misdirection: the full-on assault of ebola virus disease. Cell 2014; 159:477-86. [PMID: 25417101 DOI: 10.1016/j.cell.2014.10.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Indexed: 01/30/2023]
Abstract
Ebolaviruses cause a severe hemorrhagic fever syndrome that is rapidly fatal to humans and nonhuman primates. Ebola protein interactions with host cellular proteins disrupt type I and type II interferon responses, RNAi antiviral responses, antigen presentation, T-cell-dependent B cell responses, humoral antibodies, and cell-mediated immunity. This multifaceted approach to evasion and suppression of innate and adaptive immune responses in their target hosts leads to the severe immune dysregulation and "cytokine storm" that is characteristic of fatal ebolavirus infection. Here, we highlight some of the processes by which Ebola interacts with its mammalian hosts to evade antiviral defenses.
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Affiliation(s)
- John Misasi
- Boston Children's Hospital, Department of Medicine, Division of Infectious Diseases, Boston, MA 02115, USA
| | - Nancy J Sullivan
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Abstract
UNLABELLED Ebola virus (EBOV) entry requires the virion surface-associated glycoprotein (GP) that is composed of a trimer of heterodimers (GP1/GP2). The GP1 subunit contains two heavily glycosylated domains, the glycan cap and the mucin-like domain (MLD). The glycan cap contains only N-linked glycans, whereas the MLD contains both N- and O-linked glycans. Site-directed mutagenesis was performed on EBOV GP1 to systematically disrupt N-linked glycan sites to gain an understanding of their role in GP structure and function. All 15 N-glycosylation sites of EBOV GP1 could be removed without compromising the expression of GP. The loss of these 15 glycosylation sites significantly enhanced pseudovirion transduction in Vero cells, which correlated with an increase in protease sensitivity. Interestingly, exposing the receptor-binding domain (RBD) by removing the glycan shield did not allow interaction with the endosomal receptor, NPC1, indicating that the glycan cap/MLD domains mask RBD residues required for binding. The effects of the loss of GP1 N-linked glycans on Ca(2+)-dependent (C-type) lectin (CLEC)-dependent transduction were complex, and the effect was unique for each of the CLECs tested. Surprisingly, EBOV entry into murine peritoneal macrophages was independent of GP1 N-glycans, suggesting that CLEC-GP1 N-glycan interactions are not required for entry into this important primary cell. Finally, the removal of all GP1 N-glycans outside the MLD enhanced antiserum and antibody sensitivity. In total, our results provide evidence that the conserved N-linked glycans on the EBOV GP1 core protect GP from antibody neutralization despite the negative impact the glycans have on viral entry efficiency. IMPORTANCE Filovirus outbreaks occur sporadically throughout central Africa, causing high fatality rates among the general public and health care workers. These unpredictable hemorrhagic fever outbreaks are caused by multiple species of Ebola viruses, as well as Marburg virus. While filovirus vaccines and therapeutics are being developed, there are no licensed products. The sole viral envelope glycoprotein, which is a principal immunogenic target, contains a heavy shield of glycans surrounding the conserved receptor-binding domain. We find that disruption of this shield through targeted mutagenesis leads to an increase in cell entry, protease sensitivity, and antiserum/antibody sensitivity but is not sufficient to allow virion binding to the intracellular receptor NPC1. Therefore, our studies provide evidence that filoviruses maintain glycoprotein glycosylation to protect against proteases and antibody neutralization at the expense of efficient entry. Our results unveil interesting insights into the unique entry process of filoviruses and potential immune evasion tactics of the virus.
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Abstract
Ebola is a highly virulent pathogen causing severe hemorrhagic fever with a high case fatality rate in humans and non-human primates (NHPs). Although safe and effective vaccines or other medicinal agents to block Ebola infection are currently unavailable, a significant effort has been put forth to identify several promising candidates for the treatment and prevention of Ebola hemorrhagic fever. Among these, recombinant adenovirus-based vectors have been identified as potent vaccine candidates, with some affording both pre- and post-exposure protection from the virus. Recently, Investigational New Drug (IND) applications have been approved by the US Food and Drug Administration (FDA) and phase I clinical trials have been initiated for two small-molecule therapeutics: anti-sense phosphorodiamidate morpholino oligomers (PMOs: AVI-6002, AVI-6003) and lipid nanoparticle/small interfering RNA (LNP/siRNA: TKM-Ebola). These potential alternatives to vector-based vaccines require multiple doses to achieve therapeutic efficacy, which is not ideal with regard to patient compliance and outbreak scenarios. These concerns have fueled a quest for even better vaccination and treatment strategies. Here, we summarize recent advances in vaccines or post-exposure therapeutics for prevention of Ebola hemorrhagic fever. The utility of novel pharmaceutical approaches to refine and overcome barriers associated with the most promising therapeutic platforms are also discussed.
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Affiliation(s)
- Jin Huk Choi
- Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, TX, 78712, U.S.A
| | - Maria A. Croyle
- Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, TX, 78712, U.S.A
- Institute of Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, 78712, U.S.A
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Blinov VM, Krasnov GS, Shargunov AV, Shurdov MA, Zverev VV. Immunosuppressive domains of retroviruses: Cell mechanisms of the effect on the human immune system. Mol Biol 2013. [DOI: 10.1134/s0026893313050026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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The lack of maturation of Ebola virus-infected dendritic cells results from the cooperative effect of at least two viral domains. J Virol 2013; 87:7471-85. [PMID: 23616668 DOI: 10.1128/jvi.03316-12] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ebola virus (EBOV) infections are characterized by deficient T lymphocyte responses, T lymphocyte apoptosis, and lymphopenia in the absence of direct infection of T lymphocytes. In contrast, dendritic cells (DC) are infected but fail to mature appropriately, thereby impairing the T cell response. We investigated the contributions of EBOV proteins in modulating DC maturation by generating recombinant viruses expressing enhanced green fluorescent protein and carrying mutations affecting several potentially immunomodulating domains. They included envelope glycoprotein (GP) domains, as well as innate response antagonist domains (IRADs) previously identified in the VP24 and VP35 proteins. GP expressed by an unrelated vector, but not the wild-type EBOV, was found to strongly induce DC maturation, and infections with recombinant EBOV carrying mutations disabling GP functional domains did not restore DC maturation. In contrast, each of the viruses carrying mutations disabling any IRAD in VP35 induced a dramatic upregulation of DC maturation markers. This was dependent on infection, but not interaction with GP. Disabling of IRADs also resulted in up to a several hundredfold increase in secretion of cytokines and chemokines. Furthermore, these mutations induced formation of homotypic DC clusters, which represent close correlates of their maturation and presumably facilitate transfer of antigen from migratory DC to lymph node DC. Thus, an individual IRAD is insufficient to suppress DC maturation; rather, the suppression of DC maturation and the "immune paralysis" observed during EBOV infections results from a cooperative effect of two or more individual IRADs.
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Shurtleff AC, Nguyen TL, Kingery DA, Bavari S. Therapeutics for filovirus infection: traditional approaches and progress towards in silico drug design. Expert Opin Drug Discov 2012; 7:935-54. [PMID: 22873527 DOI: 10.1517/17460441.2012.714364] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
INTRODUCTION Ebolaviruses and marburgviruses cause severe and often lethal human hemorrhagic fevers. As no FDA-approved therapeutics are available for these infections, efforts to discover new therapeutics are important, especially because these pathogens are considered biothreats and emerging infectious diseases. All methods for discovering new therapeutics should be considered, including compound library screening in vitro against virus and in silico structure-based drug design, where possible, if sufficient biochemical and structural information is available. AREAS COVERED This review covers the structure and function of filovirus proteins, as they have been reported to date, as well as some of the current antiviral screening approaches. The authors discuss key studies mapping small-molecule modulators that were found through library and in silico screens to potential sites on viral proteins or host proteins involved in virus trafficking and pathogenesis. A description of ebolavirus and marburgvirus diseases and available animal models is also presented. EXPERT OPINION To discover novel therapeutics with potent efficacy using sophisticated computational methods, more high-resolution crystal structures of filovirus proteins and more details about the protein functions and host interaction will be required. Current compound screening efforts are finding active antiviral compounds, but an emphasis on discovery research to investigate protein structures and functions enabling in silico drug design would provide another avenue for finding antiviral molecules. Additionally, targeting of protein-protein interactions may be a future avenue for drug discovery since disrupting catalytic sites may not be possible for all proteins.
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Affiliation(s)
- Amy C Shurtleff
- U.S. Army Medical Research Institute of Infectious Diseases, Integrated Toxicology Division, Fort Detrick, 1425 Porter Street, Frederick, MD 21702, USA.
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Groseth A, Marzi A, Hoenen T, Herwig A, Gardner D, Becker S, Ebihara H, Feldmann H. The Ebola virus glycoprotein contributes to but is not sufficient for virulence in vivo. PLoS Pathog 2012; 8:e1002847. [PMID: 22876185 PMCID: PMC3410889 DOI: 10.1371/journal.ppat.1002847] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Accepted: 06/22/2012] [Indexed: 12/28/2022] Open
Abstract
Among the Ebola viruses most species cause severe hemorrhagic fever in humans; however, Reston ebolavirus (REBOV) has not been associated with human disease despite numerous documented infections. While the molecular basis for this difference remains unclear, in vitro evidence has suggested a role for the glycoprotein (GP) as a major filovirus pathogenicity factor, but direct evidence for such a role in the context of virus infection has been notably lacking. In order to assess the role of GP in EBOV virulence, we have developed a novel reverse genetics system for REBOV, which we report here. Together with a previously published full-length clone for Zaire ebolavirus (ZEBOV), this provides a unique possibility to directly investigate the role of an entire filovirus protein in pathogenesis. To this end we have generated recombinant ZEBOV (rZEBOV) and REBOV (rREBOV), as well as chimeric viruses in which the glycoproteins from these two virus species have been exchanged (rZEBOV-RGP and rREBOV-ZGP). All of these viruses could be rescued and the chimeras replicated with kinetics similar to their parent virus in tissue culture, indicating that the exchange of GP in these chimeric viruses is well tolerated. However, in a mouse model of infection rZEBOV-RGP demonstrated markedly decreased lethality and prolonged time to death when compared to rZEBOV, confirming that GP does indeed contribute to the full expression of virulence by ZEBOV. In contrast, rREBOV-ZGP did not show any signs of virulence, and was in fact slightly attenuated compared to rREBOV, demonstrating that GP alone is not sufficient to confer a lethal phenotype or exacerbate disease in this model. Thus, while these findings provide direct evidence that GP contributes to filovirus virulence in vivo, they also clearly indicate that other factors are needed for the acquisition of full virulence.
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Affiliation(s)
- Allison Groseth
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
- Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Andrea Marzi
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
| | - Thomas Hoenen
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
| | - Astrid Herwig
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
| | - Don Gardner
- Rocky Mountain Veterinary Branch, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Stephan Becker
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
| | - Hideki Ebihara
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
| | - Heinz Feldmann
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
- Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
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Abstract
Marburg and Ebola viruses cause a severe hemorrhagic disease in humans with high fatality rates. Early target cells of filoviruses are monocytes, macrophages, and dendritic cells. The infection spreads to the liver, spleen and later other organs by blood and lymph flow. A hallmark of filovirus infection is the depletion of non-infected lymphocytes; however, the molecular mechanisms leading to the observed bystander lymphocyte apoptosis are poorly understood. Also, there is limited knowledge about the fate of infected cells in filovirus disease. In this review we will explore what is known about the intracellular events leading to virus amplification and cell damage in filovirus infection. Furthermore, we will discuss how cellular dysfunction and cell death may correlate with disease pathogenesis.
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Affiliation(s)
- Judith Olejnik
- Department of Microbiology, School of Medicine, Boston University, 72 East Concord Street, Boston, MA 02118, USA; E-Mails: (J.O.); (R.B.C.)
- National Emerging Infectious Diseases Laboratories Institute, Boston University, 72 East Concord Street, Boston, MA 02118, USA
| | - Elena Ryabchikova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Science, Pr. Lavrent’eva, 8, Novosibirsk 630090, Russian Federation; E-Mail:
| | - Ronald B. Corley
- Department of Microbiology, School of Medicine, Boston University, 72 East Concord Street, Boston, MA 02118, USA; E-Mails: (J.O.); (R.B.C.)
- National Emerging Infectious Diseases Laboratories Institute, Boston University, 72 East Concord Street, Boston, MA 02118, USA
| | - Elke Mühlberger
- Department of Microbiology, School of Medicine, Boston University, 72 East Concord Street, Boston, MA 02118, USA; E-Mails: (J.O.); (R.B.C.)
- National Emerging Infectious Diseases Laboratories Institute, Boston University, 72 East Concord Street, Boston, MA 02118, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-617-638-0336; Fax: +1-617-638-4286
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22
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Reynard O, Mokhonov V, Mokhonova E, Leung J, Page A, Mateo M, Pyankova O, Georges-Courbot MC, Raoul H, Khromykh AA, Volchkov VE. Kunjin virus replicon-based vaccines expressing Ebola virus glycoprotein GP protect the guinea pig against lethal Ebola virus infection. J Infect Dis 2011; 204 Suppl 3:S1060-5. [PMID: 21987742 DOI: 10.1093/infdis/jir347] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Pre- or postexposure treatments against the filoviral hemorrhagic fevers are currently not available for human use. We evaluated, in a guinea pig model, the immunogenic potential of Kunjin virus (KUN)-derived replicons as a vaccine candidate against Ebola virus (EBOV). Virus like particles (VLPs) containing KUN replicons expressing EBOV wild-type glycoprotein GP, membrane anchor-truncated GP (GP/Ctr), and mutated GP (D637L) with enhanced shedding capacity were generated and assayed for their protective efficacy. Immunization with KUN VLPs expressing full-length wild-type and D637L-mutated GPs but not membrane anchor-truncated GP induced dose-dependent protection against a challenge of a lethal dose of recombinant guinea pig-adapted EBOV. The surviving animals showed complete clearance of the virus. Our results demonstrate the potential for KUN replicon vectors as vaccine candidates against EBOV infection.
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Affiliation(s)
- O Reynard
- Filovirus Laboratory, INSERM U758, Human Virology Department, Claude Bernard University Lyon-1, Université de Lyon, Ecole Normale Supérieure de Lyon, Lyon, France
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23
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Negredo A, Palacios G, Vázquez-Morón S, González F, Dopazo H, Molero F, Juste J, Quetglas J, Savji N, de la Cruz Martínez M, Herrera JE, Pizarro M, Hutchison SK, Echevarría JE, Lipkin WI, Tenorio A. Discovery of an ebolavirus-like filovirus in europe. PLoS Pathog 2011; 7:e1002304. [PMID: 22039362 PMCID: PMC3197594 DOI: 10.1371/journal.ppat.1002304] [Citation(s) in RCA: 277] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 08/23/2011] [Indexed: 12/04/2022] Open
Abstract
Filoviruses, amongst the most lethal of primate pathogens, have only been reported as natural infections in sub-Saharan Africa and the Philippines. Infections of bats with the ebolaviruses and marburgviruses do not appear to be associated with disease. Here we report identification in dead insectivorous bats of a genetically distinct filovirus, provisionally named Lloviu virus, after the site of detection, Cueva del Lloviu, in Spain. A novel filovirus, provisionally named Lloviu virus (LLOV), was detected during the investigation of Miniopterus schreibersii die-offs in Cueva del Lloviu in southern Europe. LLOV is genetically distinct from other marburgviruses and ebolaviruses and is the first filovirus detected in Europe that was not imported from an endemic area in Africa. Filoviruses, amongst the most lethal of primate pathogens, have only been reported as natural infections in sub-Saharan Africa and the Philippines. Infections of bats with the ebolaviruses and marburgviruses do not appear to be associated with disease. Here we report identification of genetically distinct filovirus in dead insectivorous bats in caves in Spain.
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Affiliation(s)
- Ana Negredo
- National Center of Microbiology, (ISCIII), Madrid, Spain
| | - Gustavo Palacios
- Center for Infection and Immunity, and WHO Collaborating Centre for Diagnostics, Surveillance and Immunotherapeutics for Emerging Infectious and Zoonotic Diseases, Mailman School of Public Health of Columbia University, New York, New York, United States of America
- * E-mail:
| | | | - Félix González
- Grupo Asturiano para el Estudio y Conservacion de los Murciélagos, Posada de Llanera, Principado de Asturias, Spain
| | - Hernán Dopazo
- Evolutionary Genomics Laboratory, Centro de Investigación Príncipe Felipe, Valencia, Spain
| | | | - Javier Juste
- Evolutionary Biology Unit, Estación Biológica Doñana (CSIC), Sevilla, Spain
| | - Juan Quetglas
- Evolutionary Biology Unit, Estación Biológica Doñana (CSIC), Sevilla, Spain
| | - Nazir Savji
- Center for Infection and Immunity, and WHO Collaborating Centre for Diagnostics, Surveillance and Immunotherapeutics for Emerging Infectious and Zoonotic Diseases, Mailman School of Public Health of Columbia University, New York, New York, United States of America
| | | | - Jesus Enrique Herrera
- Center for Infection and Immunity, and WHO Collaborating Centre for Diagnostics, Surveillance and Immunotherapeutics for Emerging Infectious and Zoonotic Diseases, Mailman School of Public Health of Columbia University, New York, New York, United States of America
| | - Manuel Pizarro
- Service of Pathology, Veterinary Teaching Hospital, Veterinary School, Complutense University, Madrid, Spain
| | | | | | - W. Ian Lipkin
- Center for Infection and Immunity, and WHO Collaborating Centre for Diagnostics, Surveillance and Immunotherapeutics for Emerging Infectious and Zoonotic Diseases, Mailman School of Public Health of Columbia University, New York, New York, United States of America
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24
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Leroy EM, Gonzalez JP, Baize S. Ebola and Marburg haemorrhagic fever viruses: major scientific advances, but a relatively minor public health threat for Africa. Clin Microbiol Infect 2011; 17:964-76. [PMID: 21722250 DOI: 10.1111/j.1469-0691.2011.03535.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ebola and Marburg viruses are the only members of the Filoviridae family (order Mononegavirales), a group of viruses characterized by a linear, non-segmented, single-strand negative RNA genome. They are among the most virulent pathogens for humans and great apes, causing acute haemorrhagic fever and death within a matter of days. Since their discovery 50 years ago, filoviruses have caused only a few outbreaks, with 2317 clinical cases and 1671 confirmed deaths, which is negligible compared with the devastation caused by malnutrition and other infectious diseases prevalent in Africa (malaria, cholera, AIDS, dengue, tuberculosis …). Yet considerable human and financial resourses have been devoted to research on these viruses during the past two decades, partly because of their potential use as bioweapons. As a result, our understanding of the ecology, host interactions, and control of these viruses has improved considerably.
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Affiliation(s)
- E M Leroy
- Centre International de Recherches Médicales de Franceville, Franceville, Gabon.
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25
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Usami K, Matsuno K, Igarashi M, Denda-Nagai K, Takada A, Irimura T. Involvement of viral envelope GP2 in Ebola virus entry into cells expressing the macrophage galactose-type C-type lectin. Biochem Biophys Res Commun 2011; 407:74-8. [PMID: 21362405 DOI: 10.1016/j.bbrc.2011.02.110] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 02/22/2011] [Indexed: 11/24/2022]
Abstract
Ebola virus (EBOV) infection is initiated by the interaction of the viral surface envelope glycoprotein (GP) with the binding sites on target cells. Differences in the mortality among different species of the Ebola viruses, i.e., Zaire ebolavirus (ZEBOV) and Reston ebolavirus (REBOV), correspond to the in vitro infectivity of the pseudo-typed virus constructed with the GPs in cells expressing macrophage galactose-type calcium-type lectin (MGL/CD301). Through mutagenesis of GP2, the transmembrane-anchored subunit of GP, we found that residues 502-527 of the GP2 sequence determined the different infectivity between VSV-ZEBOV GP and -REBOV GP in MGL/CD301-expressing cells and a histidine residue at position 516 of ZEBOV GP2 appeared essential in the differential infectivity. These findings may provide a clue to clarify a molecular basis of different pathogenicity among EBOV species.
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Affiliation(s)
- Katsuaki Usami
- Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan
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26
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Abstract
Ebola viruses are the causative agents of a severe form of viral haemorrhagic fever in man, designated Ebola haemorrhagic fever, and are endemic in regions of central Africa. The exception is the species Reston Ebola virus, which has not been associated with human disease and is found in the Philippines. Ebola virus constitutes an important local public health threat in Africa, with a worldwide effect through imported infections and through the fear of misuse for biological terrorism. Ebola virus is thought to also have a detrimental effect on the great ape population in Africa. Case-fatality rates of the African species in man are as high as 90%, with no prophylaxis or treatment available. Ebola virus infections are characterised by immune suppression and a systemic inflammatory response that causes impairment of the vascular, coagulation, and immune systems, leading to multiorgan failure and shock, and thus, in some ways, resembling septic shock.
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Affiliation(s)
- Heinz Feldmann
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, MT, USA.
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27
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Wauquier N, Becquart P, Padilla C, Baize S, Leroy EM. Human fatal zaire ebola virus infection is associated with an aberrant innate immunity and with massive lymphocyte apoptosis. PLoS Negl Trop Dis 2010; 4:e837. [PMID: 20957152 PMCID: PMC2950153 DOI: 10.1371/journal.pntd.0000837] [Citation(s) in RCA: 275] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 09/03/2010] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Ebolavirus species Zaire (ZEBOV) causes highly lethal hemorrhagic fever, resulting in the death of 90% of patients within days. Most information on immune responses to ZEBOV comes from in vitro studies and animal models. The paucity of data on human immune responses to this virus is mainly due to the fact that most outbreaks occur in remote areas. Published studies in this setting, based on small numbers of samples and limited panels of immunological markers, have given somewhat different results. METHODOLOGY/PRINCIPAL FINDINGS Here, we studied a unique collection of 56 blood samples from 42 nonsurvivors and 14 survivors, obtained during the five outbreaks that occurred between 1996 and 2003 in Gabon and Republic of Congo. Using Luminex technology, we assayed 50 cytokines in all 56 samples and performed phenotypic analyses by flow cytometry. We found that fatal outcome was associated with hypersecretion of numerous proinflammatory cytokines (IL-1β, IL-1RA, IL-6, IL-8, IL-15 and IL-16), chemokines and growth factors (MIP-1α, MIP-1β, MCP-1, M-CSF, MIF, IP-10, GRO-α and eotaxin). Interestingly, no increase of IFNα2 was detected in patients. Furthermore, nonsurvivors were also characterized by very low levels of circulating cytokines produced by T lymphocytes (IL-2, IL-3, IL-4, IL-5, IL-9, IL-13) and by a significant drop of CD3+CD4+ and CD3+CD8+ peripheral cells as well as a high increase in CD95 expression on T lymphocytes. CONCLUSIONS/SIGNIFICANCE This work, the largest study to be conducted to date in humans, showed that fatal outcome is associated with aberrant innate immune responses and with global suppression of adaptive immunity. The innate immune reaction was characterized by a "cytokine storm," with hypersecretion of numerous proinflammatory cytokines, chemokines and growth factors, and by the noteworthy absence of antiviral IFNα2. Immunosuppression was characterized by very low levels of circulating cytokines produced by T lymphocytes and by massive loss of peripheral CD4 and CD8 lymphocytes, probably through Fas/FasL-mediated apoptosis.
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Affiliation(s)
- Nadia Wauquier
- Unité des Maladies Virales Émergentes, Centre International de Recherches Médicales de Franceville, Franceville, Gabon
| | - Pierre Becquart
- Unité des Maladies Virales Émergentes, Centre International de Recherches Médicales de Franceville, Franceville, Gabon
- UMR190 Emergence des Pathologies Virales, Université Aix-Marseille II and Institut de Recherche pour le Développement, Marseille, France
| | - Cindy Padilla
- Unité des Maladies Virales Émergentes, Centre International de Recherches Médicales de Franceville, Franceville, Gabon
| | - Sylvain Baize
- Unité de Biologie des Infections Virales Emergentes, Institut Pasteur, IFR128-Biosciences Gerland-Lyon Sud, Lyon, France
| | - Eric M. Leroy
- Unité des Maladies Virales Émergentes, Centre International de Recherches Médicales de Franceville, Franceville, Gabon
- UMR190 Emergence des Pathologies Virales, Université Aix-Marseille II and Institut de Recherche pour le Développement, Marseille, France
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29
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Abstract
The glycoprotein (GP) of Ebola is the sole structural protein that forms the spikes on the viral envelope. The GP contains two subunits, GP1 and GP2, linked by a disulfide bond, which are responsible for receptor binding and membrane fusion, respectively. In this study, the full length of GP gene of Ebola Zaire species, 2028 base pairs in length, was synthesized using 38 overlapping oligonucleotides by multiple rounds of polymerase chain reaction (PCR). The synthesized GP gene was shown to be efficiently expressed in mammalian cells. Furthermore, an efficient HIV-based pseudotyping system was developed using the synthetic GP gene, providing a safe approach to dissecting the entry mechanism of Ebola viruses. Using this pseudotyping system and mutational analysis, the role of the charged residues in the GP2 helical regions was examined. It was found that substitutions of the most charged residues in the regions did not adversely affect GP expression, processing, or viral incorporation, however, most of the mutations greatly impaired the ability of GP to mediate efficient viral infection. These results demonstrate that these charged residues of GP2 play an important role in GP-mediated Ebola entry into its host cells. We propose that these charged residues are involved in forming the intermediate conformation(s) of GP in membrane fusion and Ebola entry.
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30
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Ascenzi P, Bocedi A, Heptonstall J, Capobianchi MR, Di Caro A, Mastrangelo E, Bolognesi M, Ippolito G. Ebolavirus and Marburgvirus: insight the Filoviridae family. Mol Aspects Med 2007; 29:151-85. [PMID: 18063023 DOI: 10.1016/j.mam.2007.09.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 09/28/2007] [Indexed: 11/26/2022]
Abstract
Ebolavirus and Marburgvirus (belonging to the Filoviridae family) emerged four decades ago and cause epidemics of haemorrhagic fever with high case-fatality rates. The genome of filoviruses encodes seven proteins. No significant homology is observed between filovirus proteins and any known macromolecule. Moreover, Marburgvirus and Ebolavirus show significant differences in protein homology. The natural maintenance cycle of filoviruses is unknown, the natural reservoir, the mode of transmission, the epidemic disease generation, and temporal dynamics are unclear. Lastly, Ebolavirus and Marburgvirus are considered as potential biological weapons. Vaccine appears the unique therapeutic frontier. Here, molecular and clinical aspects of filoviral haemorrhagic fevers are summarized.
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Affiliation(s)
- Paolo Ascenzi
- National Institute for Infectious Diseases IRCCS Lazzaro Spallanzani, Via Portuense 292, I-00149 Roma, Italy
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31
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Amberg SM, Netter RC, Simmons G, Bates P. Expanded tropism and altered activation of a retroviral glycoprotein resistant to an entry inhibitor peptide. J Virol 2007; 80:353-9. [PMID: 16352560 PMCID: PMC1317511 DOI: 10.1128/jvi.80.1.353-359.2006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The envelope of class I viruses can be a target for potent viral inhibitors, such as the human immunodeficiency virus type 1 (HIV-1) inhibitor enfuvirtide, which are derived from the C-terminal heptad repeat (HR2) of the transmembrane (TM) subunit. Resistance to an HR2-based peptide inhibitor of a model retrovirus, subgroup A of the Avian Sarcoma and Leukosis Virus genus (ASLV-A), was studied by examining mutants derived by viral passage in the presence of inhibitor. Variants with reduced sensitivity to inhibitor were readily selected in vitro. Sensitivity determinants were identified for 13 different isolates, all of which mapped to the TM subunit. These determinants were identified in two regions: (i) the N-terminal heptad repeat (HR1) and (ii) the N-terminal segment of TM, between the subunit cleavage site and the fusion peptide. The latter class of mutants identified a region outside of the predicted HR2-binding site that can significantly alter sensitivity to inhibitor. A subset of the HR1 mutants displayed the unanticipated ability to infect nonavian cells. This expanded tropism was associated with increased efficiency of envelope triggering by soluble receptor at low temperatures, as measured by protease sensitivity of the surface subunit (SU) of envelope. In addition, expanded tropism was linked for the most readily triggered mutants with increased sensitivity to neutralization by SU-specific antiserum. These observations depict a class of HR2 peptide-selected mutations with a reduced activation threshold, thereby allowing the utilization of alternative receptors for viral entry.
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Affiliation(s)
- Sean M Amberg
- Department of Microbiology, University of Pennsylvania School of Medicine, 225 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104-6076, USA
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Yaddanapudi K, Palacios G, Towner JS, Chen I, Sariol CA, Nichol ST, Lipkin WI. Implication of a retrovirus-like glycoprotein peptide in the immunopathogenesis of Ebola and Marburg viruses. FASEB J 2006; 20:2519-30. [PMID: 17023517 DOI: 10.1096/fj.06-6151com] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Ebola and Marburg viruses can cause hemorrhagic fever (HF) outbreaks with high mortality in primates. Whereas Marburg (MARV), Ebola Zaire (ZEBOV), and Ebola Sudan (SEBOV) viruses are pathogenic in humans, apes, and monkeys, Ebola Reston (REBOV) is pathogenic only in monkeys. Early immunosuppression may contribute to pathogenesis by facilitating viral replication. Lymphocyte depletion, intravascular apoptosis, and cytokine dysregulation are prominent in fatal cases. Here we functionally characterize a 17 amino acid domain in filoviral glycoproteins that resembles an immunosuppressive motif in retroviral envelope proteins. Activated human or rhesus peripheral blood mononuclear cells (PBMC) were exposed to inactivated ZEBOV or a panel of 17mer peptides representing all sequenced strains of filoviruses, then analyzed for CD4+ and CD8+ T cell activation, apoptosis, and cytokine expression. Exposure of human and rhesus PBMC to ZEBOV, SEBOV, or MARV peptides or inactivated ZEBOV resulted in decreased expression of activation markers on CD4 and CD8 cells; CD4 and CD8 cell apoptosis as early as 12 h postexposure; inhibition of CD4 and CD8 cell cycle progression; decreased interleukin (IL)-2, IFN-gamma, and IL12-p40 expression; and increased IL-10 expression. In contrast, only rhesus T cells were sensitive to REBOV peptides. These findings are consistent with the observation that REBOV is not pathogenic in humans and have implications for understanding the pathogenesis of filoviral HF.
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Affiliation(s)
- Kavitha Yaddanapudi
- Jerome L. and Dawn Greene Infectious Disease Laboratory, Mailman School of Public Health, Columbia University, 722 West 168th St., New York, NY 10032, USA
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Towner JS, Khristova ML, Sealy TK, Vincent MJ, Erickson BR, Bawiec DA, Hartman AL, Comer JA, Zaki SR, Ströher U, Gomes da Silva F, del Castillo F, Rollin PE, Ksiazek TG, Nichol ST. Marburgvirus genomics and association with a large hemorrhagic fever outbreak in Angola. J Virol 2006; 80:6497-516. [PMID: 16775337 PMCID: PMC1488971 DOI: 10.1128/jvi.00069-06] [Citation(s) in RCA: 222] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In March 2005, the Centers for Disease Control and Prevention (CDC) investigated a large hemorrhagic fever (HF) outbreak in Uige Province in northern Angola, West Africa. In total, 15 initial specimens were sent to CDC, Atlanta, Ga., for testing for viruses associated with viral HFs known to be present in West Africa, including ebolavirus. Marburgvirus was also included despite the fact that the origins of all earlier outbreaks were linked directly to East Africa. Surprisingly, marburgvirus was confirmed (12 of 15 specimens) as the cause of the outbreak. The outbreak likely began in October 2004 and ended in July 2005, and it included 252 cases and 227 (90%) fatalities (report from the Ministry of Health, Republic of Angola, 2005), making it the largest Marburg HF outbreak on record. A real-time quantitative reverse transcription-PCR assay utilized and adapted during the outbreak proved to be highly sensitive and sufficiently robust for field use. Partial marburgvirus RNA sequence analysis revealed up to 21% nucleotide divergence among the previously characterized East African strains, with the most distinct being Ravn from Kenya (1987). The Angolan strain was less different ( approximately 7%) from the main group of East African marburgviruses than one might expect given the large geographic separation. To more precisely analyze the virus genetic differences between outbreaks and among viruses within the Angola outbreak itself, a total of 16 complete virus genomes were determined, including those of the virus isolates Ravn (Kenya, 1987) and 05DRC, 07DRC, and 09DRC (Democratic Republic of Congo, 1998) and the reference Angolan virus isolate (Ang1379v). In addition, complete genome sequences were obtained from RNAs extracted from 10 clinical specimens reflecting various stages of the disease and locations within the Angolan outbreak. While the marburgviruses exhibit high overall genetic diversity (up to 22%), only 6.8% nucleotide difference was found between the West African Angolan viruses and the majority of East African viruses, suggesting that the virus reservoir species in these regions are not substantially distinct. Remarkably few nucleotide differences were found among the Angolan clinical specimens (0 to 0.07%), consistent with an outbreak scenario in which a single (or rare) introduction of virus from the reservoir species into the human population was followed by person-to-person transmission with little accumulation of mutations. This is in contrast to the 1998 to 2000 marburgvirus outbreak, where evidence of several virus genetic lineages (with up to 21% divergence) and multiple virus introductions into the human population was found.
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Affiliation(s)
- Jonathan S Towner
- Special Pathogens Branch, Centers for Disease Control and Prevention, 1600 Clifton Road, Mailstop G14, Atlanta, GA 30333, USA
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Marzi A, Wegele A, Pöhlmann S. Modulation of virion incorporation of Ebolavirus glycoprotein: effects on attachment, cellular entry and neutralization. Virology 2006; 352:345-56. [PMID: 16777170 DOI: 10.1016/j.virol.2006.04.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 02/23/2006] [Accepted: 04/27/2006] [Indexed: 01/09/2023]
Abstract
The filoviruses Ebolavirus (EBOV) and Marburgvirus (MARV) cause severe hemorrhagic fever in humans and are potential agents of biological warfare. The envelope glycoprotein (GP) of filoviruses mediates viral entry into cells and is an attractive target for therapeutic intervention and vaccine design. Here, we asked if the efficiency of virion incorporation of EBOV-GP impacts attachment and entry into target cells and modulates susceptibility to neutralizing antibodies. In order to control the level of EBOV-GP expression, we generated cell lines expressing the GPs of the four known EBOV subspecies in an inducible fashion. Regulated expression of GP on the cell surface allowed production of reporter viruses harboring different amounts of GP. A pronounced reduction of virion incorporation of EBOV-GP had relatively little effect on virion infectivity, suggesting that only a few copies of GP might be sufficient for efficient engagement of cellular receptors. In contrast, optimal interactions with cellular attachment factors like the DC-SIGN protein required incorporation of high amounts of GP. Antibody-mediated neutralization of virions bearing high amounts of GP was slightly more efficient than neutralization of virions harboring low amounts of GP, suggesting that the efficiency of GP incorporation into virions might modulate susceptibility to neutralizing antibodies. Finally, regulated expression of GP in permissive 293 cells did not reduce EBOV-GP-driven infection but diminished vesicular stomatitis virus GP (VSV-G) and amphotropic murine leukemia virus (A-MLV) GP mediated entry in a dose-dependent manner. Therefore, intracellular GP does not seem to downmodulate expression of its receptor(s) but might alter expression and/or function of molecules involved in VSV-G and A-MLV-GP-dependent entry. Our results suggest that the efficiency of virion incorporation of GP could impact EBOV attachment to target cells and might modulate control of viral spread by the humoral immune response.
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Affiliation(s)
- Andrea Marzi
- Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, 91054 Erlangen, Germany
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Hoenen T, Groseth A, Falzarano D, Feldmann H. Ebola virus: unravelling pathogenesis to combat a deadly disease. Trends Mol Med 2006; 12:206-15. [PMID: 16616875 DOI: 10.1016/j.molmed.2006.03.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 02/24/2006] [Accepted: 03/27/2006] [Indexed: 10/24/2022]
Abstract
Ebola virus (EBOV) causes severe haemorrhagic fever leading to up to 90% lethality. Increasingly frequent outbreaks and the placement of EBOV in the category A list of potential biothreat agents have boosted interest in this virus. Furthermore, development of new technologies (e.g. reverse genetics systems) and extensive studies on Ebola haemorrhagic fever (EHF) in animal models have substantially expanded the knowledge on the pathogenic mechanisms that underlie this disease. Two major factors in EBOV pathogenesis are the impairment of the immune response and vascular dysfunction. Here, we attempt to summarize the current knowledge on EBOV pathogenesis focusing on these two factors and on recent progress in the development of vaccines and potential therapeutics.
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Affiliation(s)
- Thomas Hoenen
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington St., Winnipeg, MB R3E 3R2, Canada
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36
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Philipp-Staheli J, Marquardt T, Thouless ME, Bruce AG, Grant RF, Tsai CC, Rose TM. Genetic variability of the envelope gene of Type D simian retrovirus-2 (SRV-2) subtypes associated with SAIDS-related retroperitoneal fibromatosis in different macaque species. Virol J 2006; 3:11. [PMID: 16515713 PMCID: PMC1450265 DOI: 10.1186/1743-422x-3-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Accepted: 03/06/2006] [Indexed: 11/21/2022] Open
Abstract
Background D-type simian retrovirus-2 (SRV-2) causes an AIDS-like immune deficiency syndrome (SAIDS) in various macaque species. SAIDS is often accompanied by retroperitoneal fibromatosis (RF), an aggressive fibroproliferative disorder reminiscent of Kaposi's sarcoma in patients with HIV-induced AIDS. In order to determine the association of SRV-2 subtypes with SAIDS-RF, and study the evolution and transmission of SRV-2 in captive macaque populations, we have molecularly characterized the env gene of a number of SRV-2 isolates from different macaque species with and without RF. Results We sequenced the env gene from eighteen SRV-2 isolates and performed sequence comparisons and phylogenetic analyses. Our studies revealed the presence of six distinct subtypes of SRV-2, three of which were associated with SAIDS-RF cases. We found no association between SRV-2 subtypes and a particular macaque species. Little sequence variation was detected in SRV-2 isolates from the same individual, even after many years of infection, or from macaques housed together or related by descent from a common infected parent. Seventy-two amino acid changes were identified, most occurring in the larger gp70 surface protein subunit. In contrast to the lentiviruses, none of the amino acid variations involved potential N-linked glycosylation sites. Structural analysis of a domain within the gp22/gp20 transmembrane subunit that was 100% conserved between SRV-2 subtypes, revealed strong similarities to a disulfide-bonded loop that is crucial for virus-cell fusion and is found in retroviruses and filoviruses. Conclusion Our study suggests that separate introductions of at least six parental SRV-2 subtypes into the captive macaque populations in the U.S. have occurred with subsequent horizontal transfer between macaque species and primate centers. No specific association of a single SRV-2 subtype with SAIDS-RF was seen. The minimal genetic variability of the env gene within a subtype over time suggests that a strong degree of adaptation to its primate host has occurred during evolution of the virus.
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Affiliation(s)
- Jeannette Philipp-Staheli
- Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA
| | - Taya Marquardt
- Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA
| | - Margaret E Thouless
- Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA
| | | | - Richard F Grant
- Washington National Primate Research Center, University of Washington, Seattle, Washington, USA
| | - Che-Chung Tsai
- Washington National Primate Research Center, University of Washington, Seattle, Washington, USA
| | - Timothy M Rose
- Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA
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37
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Abstract
The agents causing viral hemorrhagic fever (VHF) are a taxonomically diverse group of viruses that may share commonalities in the process whereby they produce systemic and frequently fatal disease. Significant progress has been made in understanding the biology of the Ebola virus, one of the best known examples. This knowledge has guided our thinking about other VHF agents, including Marburg, Lassa, the South American arenaviruses, yellow fever, Crimean-Congo and Rift Valley fever viruses. Comparisons among VHFs show that a common pathogenic feature is their ability to disable the host immune response by attacking and manipulating the cells that initiate the antiviral response. Of equal importance, these comparisons highlight critical gaps in our knowledge of these pathogens.
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Affiliation(s)
- Thomas W Geisbert
- Virology Division, US Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, Maryland 21702-5011, USA.
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38
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Volchkov VE, Volchkova VA, Dolnik O, Feldmann H, Klenk HD. Polymorphism of Filovirus Glycoproteins. Adv Virus Res 2005; 64:359-81. [PMID: 16139600 DOI: 10.1016/s0065-3527(05)64011-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Viktor E Volchkov
- Biologie des Filovirus, Claude Bernard University Lyon, INSERM U412 69365 Lyon, France
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39
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Netter RC, Amberg SM, Balliet JW, Biscone MJ, Vermeulen A, Earp LJ, White JM, Bates P. Heptad repeat 2-based peptides inhibit avian sarcoma and leukosis virus subgroup a infection and identify a fusion intermediate. J Virol 2004; 78:13430-9. [PMID: 15564453 PMCID: PMC533931 DOI: 10.1128/jvi.78.24.13430-13439.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fusion proteins of enveloped viruses categorized as class I are typified by two distinct heptad repeat domains within the transmembrane subunit. These repeats are important structural elements that assemble into the six-helix bundles characteristic of the fusion-activated envelope trimer. Peptides derived from these domains can be potent and specific inhibitors of membrane fusion and virus infection. To facilitate our understanding of retroviral entry, peptides corresponding to the two heptad repeat domains of the avian sarcoma and leukosis virus subgroup A (ASLV-A) TM subunit of the envelope protein were characterized. Two peptides corresponding to the C-terminal heptad repeat (HR2), offset from one another by three residues, were effective inhibitors of infection, while two overlapping peptides derived from the N-terminal heptad repeat (HR1) were not. Analysis of envelope mutants containing substitutions within the HR1 domain revealed that a single amino acid change, L62A, significantly reduced sensitivity to peptide inhibition. Virus bound to cells at 4 degrees C became sensitive to peptide within the first 5 min of elevating the temperature to 37 degrees C and lost sensitivity to peptide after 15 to 30 min, consistent with a transient intermediate in which the peptide binding site is exposed. In cell-cell fusion experiments, peptide inhibitor sensitivity occurred prior to a fusion-enhancing low-pH pulse. Soluble receptor for ASLV-A induces a lipophilic character in the envelope which can be measured by stable liposome binding, and this activation was found to be unaffected by inhibitory HR2 peptide. Finally, receptor-triggered conformational changes in the TM subunit were also found to be unaffected by inhibitory peptide. These changes are marked by a dramatic shift in mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, from a subunit of 37 kDa to a complex of about 80 kDa. Biotinylated HR2 peptide bound specifically to the 80-kDa complex, demonstrating a surprisingly stable envelope conformation in which the HR2 binding site is exposed. These experiments support a model in which receptor interaction promotes formation of an envelope conformation in which the TM subunit is stably associated with its target membrane and is able to bind a C-terminal peptide.
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Affiliation(s)
- Robert C Netter
- Department of Microbiology, University of Pennsylvania School of Medicine, 225 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104-6076, USA
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40
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Sanders DA. Ebola virus glycoproteins: guidance devices for targeting gene therapy vectors. Expert Opin Biol Ther 2004; 4:329-36. [PMID: 15006727 DOI: 10.1517/14712598.4.3.329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Replacing the native viral envelope protein on the surface of a retrovirus or lentivirus with the glycoprotein of a foreign enveloped virus, a process called pseudotyping, can expand the set of potential target cells for a viral vector or can restrict entry to specific cells. The Ebola virus glycoprotein, because of its evolutionary origins and the route of viral entry promoted by it, possesses distinct advantages in forming the outer shell of such pseudotyped retroviruses for gene therapy applications. Studies of the transduction of human airway epithelia by lentivirus pseudotyped with a modified Ebola virus glycoprotein from which the region of O- glycosylation has been removed have demonstrated that such recombinant viruses possess particular promise for the treatment of cystic fibrosis. This result highlights the synergism between basic studies of virus entry and gene therapy advances.
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Affiliation(s)
- David A Sanders
- Markey Center for Structural Biology, Department of Biological Sciences, Lilly Hall, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, USA.
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41
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Abstract
Infection by all enveloped viruses occurs via the fusion of viral and cellular membranes and delivery of the viral nucleocapsid into the cell cytoplasm, after association of the virus with cognate receptors at the cell surface. This process is mediated by viral fusion proteins anchored in the viral envelope and can be defined based on the requirement for low pH to trigger membrane fusion. In viruses that utilize a pH-dependent entry mechanism, such as influenza virus, viral fusion is triggered by the acidic environment of intracellular organelles after uptake of the virus from the cell surface and trafficking to a low-pH compartment. In contrast, in viruses that utilize a pH-independent entry mechanism, such as most retroviruses, membrane fusion is triggered solely by the interaction of the envelope glycoprotein with cognate receptors, often at the cell surface. However, recent work has indicated that the alpharetrovirus, avian sarcoma and leukosis virus (ASLV), utilizes a novel entry mechanism that combines aspects of both pH-independent and pH-dependent entry. In ASLV infection, the interaction of the envelope glycoprotein (Env) with cognate receptors at the cell surface causes an initial conformational change that primes (activates) Env and renders it sensitive to subsequent low-pH triggering from an intracellular compartment. Thus unlike other pH-dependent viruses, ASLV Env is only sensitive to low-pH triggering following interaction with its cognate receptor. In this manuscript we review current research on ASLV Env-receptor interactions and focus on the specific molecular requirements of both the viral fusion protein and cognate receptors for ASLV entry. In addition, we review data pertaining to the novel two-step entry mechanism of ASLV entry and propose a model by which ASLV Env elicits membrane fusion.
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Affiliation(s)
- R J O Barnard
- McArdle Laboratories for Cancer Research, Department of Oncology, University of Wisconsin Madison, 1400 University Ave, Madison, WI 53706, USA
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42
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Abstract
Ebola virus, being highly pathogenic for humans and non-human primates and the subject of former weapons programmes, is now one of the most feared pathogens worldwide. In addition, the lack of pre- and post-exposure interventions makes the development of rapid diagnostics, new antiviral agents and protective vaccines a priority for many nations. Further insight into the ecology, immunology and pathogenesis of Ebola virus will promote the delivery of these urgently required tools.
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Affiliation(s)
- Heinz Feldmann
- Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
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43
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Abstract
The role of covalent modifications of the Ebola virus glycoprotein (GP) and the significance of the sequence identity between filovirus and avian retrovirus GPs were investigated through biochemical and functional analyses of mutant GPs. The expression and processing of mutant GPs with altered N-linked glycosylation, substitutions for conserved cysteine residues, or a deletion in the region of O-linked glycosylation were analyzed, and virus entry capacities were assayed through the use of pseudotyped retroviruses. Cys-53 was the only GP(1) ( approximately 130 kDa) cysteine residue whose replacement resulted in the efficient secretion of GP(1), and it is therefore proposed that it participates in the formation of the only disulfide bond linking GP(1) to GP(2) ( approximately 24 kDa). We propose a complete cystine bridge map for the filovirus GPs based upon our analysis of mutant Ebola virus GPs. The effect of replacement of the conserved cysteines in the membrane-spanning region of GP(2) was found to depend on the nature of the substitution. Mutations in conserved N-linked glycosylation sites proved generally, with a few exceptions, innocuous. Deletion of the O-linked glycosylation region increased GP processing, incorporation into retrovirus particles, and viral transduction. Our data support a common evolutionary origin for the GPs of Ebola virus and avian retroviruses and have implications for gene transfer mediated by Ebola virus GP-pseudotyped retroviruses.
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Affiliation(s)
- Scott A Jeffers
- Department of Biological Sciences, Purdue University, 1392 Lilly Hall, West Lafayette, IN 47907, USA
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44
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Feldmann H, Volchkov VE, Volchkova VA, Ströher U, Klenk HD. Biosynthesis and role of filoviral glycoproteins. J Gen Virol 2001; 82:2839-2848. [PMID: 11714958 DOI: 10.1099/0022-1317-82-12-2839] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Heinz Feldmann
- Canadian Science Centre for Human and Animal Health, 1015 Arlington Street, Winnipeg, Manitoba, CanadaR3E 3R21
| | - Viktor E Volchkov
- Biologie des Filovirus, Claude Bernard University Lyon-1, 46 Allée d'Italie, 69007 Lyon, France2
| | - Valentina A Volchkova
- Biologie des Filovirus, Claude Bernard University Lyon-1, 46 Allée d'Italie, 69007 Lyon, France2
| | - Ute Ströher
- Institut für Virologie, Philipps-Universität, Robert-Koch-Str. 17, D-35037 Marburg, Germany3
| | - Hans-Dieter Klenk
- Institut für Virologie, Philipps-Universität, Robert-Koch-Str. 17, D-35037 Marburg, Germany3
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45
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Abstract
Ebola virus causes lethal hemorrhagic disease in humans, yet there are still no satisfactory biological explanations to account for its extreme virulence. This review focuses on recent findings relevant to understanding the pathogenesis of Ebola virus infection and developing vaccines and effective therapy. The available data suggest that the envelope glycoprotein and the interaction of some viral proteins with the immune system are likely to play important roles in the extraordinary pathogenicity of this virus. There are also indications that genetically engineered vaccines, including plasmid DNA and viral vectors expressing Ebola virus proteins, and passive transfer of neutralizing antibodies could be feasible options for the control of Ebola virus-associated disease.
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Affiliation(s)
- A Takada
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
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46
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Volchkov VE, Volchkova VA, Muhlberger E, Kolesnikova LV, Weik M, Dolnik O, Klenk HD. Recovery of infectious Ebola virus from complementary DNA: RNA editing of the GP gene and viral cytotoxicity. Science 2001; 291:1965-9. [PMID: 11239157 DOI: 10.1126/science.1057269] [Citation(s) in RCA: 219] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
To study the mechanisms underlying the high pathogenicity of Ebola virus, we have established a system that allows the recovery of infectious virus from cloned cDNA and thus permits genetic manipulation. We created a mutant in which the editing site of the gene encoding envelope glycoprotein (GP) was eliminated. This mutant no longer expressed the nonstructural glycoprotein sGP. Synthesis of GP increased, but most of it accumulated in the endoplasmic reticulum as immature precursor. The mutant was significantly more cytotoxic than wild-type virus, indicating that cytotoxicity caused by GP is down-regulated by the virus through transcriptional RNA editing and expression of sGP.
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Affiliation(s)
- V E Volchkov
- Institut für Virologie, Philipps-Universität, Robert-Koch-Strasse 17, 35037 Marburg, Germany.
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47
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Abstract
Hemagglutinin (HA) is the receptor-binding and membrane fusion glycoprotein of influenza virus and the target for infectivity-neutralizing antibodies. The structures of three conformations of the ectodomain of the 1968 Hong Kong influenza virus HA have been determined by X-ray crystallography: the single-chain precursor, HA0; the metastable neutral-pH conformation found on virus, and the fusion pH-induced conformation. These structures provide a framework for designing and interpreting the results of experiments on the activity of HA in receptor binding, the generation of emerging and reemerging epidemics, and membrane fusion during viral entry. Structures of HA in complex with sialic acid receptor analogs, together with binding experiments, provide details of these low-affinity interactions in terms of the sialic acid substituents recognized and the HA residues involved in recognition. Neutralizing antibody-binding sites surround the receptor-binding pocket on the membrane-distal surface of HA, and the structures of the complexes between neutralizing monoclonal Fabs and HA indicate possible neutralization mechanisms. Cleavage of the biosynthetic precursor HA0 at a prominent loop in its structure primes HA for subsequent activation of membrane fusion at endosomal pH (Figure 1). Priming involves insertion of the fusion peptide into a charged pocket in the precursor; activation requires its extrusion towards the fusion target membrane, as the N terminus of a newly formed trimeric coiled coil, and repositioning of the C-terminal membrane anchor near the fusion peptide at the same end of a rod-shaped molecule. Comparison of this new HA conformation, which has been formed for membrane fusion, with the structures determined for other virus fusion glycoproteins suggests that these molecules are all in the fusion-activated conformation and that the juxtaposition of the membrane anchor and fusion peptide, a recurring feature, is involved in the fusion mechanism. Extension of these comparisons to the soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) protein complex of vesicle fusion allows a similar conclusion.
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Affiliation(s)
- J J Skehel
- National Institute for Medical Research, London NW7 1AA, England
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48
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Sänger C, Mühlberger E, Ryabchikova E, Kolesnikova L, Klenk HD, Becker S. Sorting of Marburg virus surface protein and virus release take place at opposite surfaces of infected polarized epithelial cells. J Virol 2001; 75:1274-83. [PMID: 11152500 PMCID: PMC114033 DOI: 10.1128/jvi.75.3.1274-1283.2001] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Marburg virus, a filovirus, causes severe hemorrhagic fever with hitherto poorly understood molecular pathogenesis. We have investigated here the vectorial transport of the surface protein GP of Marburg virus in polarized epithelial cells. To this end, we established an MDCKII cell line that was able to express GP permanently (MDCK-GP). The functional integrity of GP expressed in these cells was analyzed using vesicular stomatitis virus pseudotypes. Further experiments revealed that GP is transported in MDCK-GP cells mainly to the apical membrane and is released exclusively into the culture medium facing the apical membrane. When MDCKII cells were infected with Marburg virus, the majority of GP was also transported to the apical membrane, suggesting that the protein contains an autonomous apical transport signal. Release of infectious progeny virions, however, took place exclusively at the basolateral membrane of the cells. Thus, vectorial budding of Marburg virus is presumably determined by factors other than the surface protein.
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Affiliation(s)
- C Sänger
- Institut für Virologie, Philipps-Universität Marburg, D-35037 Marburg, Germany
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49
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Volchkov VE, Chepurnov AA, Volchkova VA, Ternovoj VA, Klenk HD. Molecular characterization of guinea pig-adapted variants of Ebola virus. Virology 2000; 277:147-55. [PMID: 11062045 DOI: 10.1006/viro.2000.0572] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Serial passage of initially nonlethal Ebola virus (EBOV) in outbred guinea pigs resulted in the selection of variants with high pathogenicity. Nucleotide sequence analysis of the complete genome of the guinea pig-adapted variant 8mc revealed that it differed from wild-type virus by eight mutations. No mutations were identified in nontranscribed regions, including leader, trailer, and intragenic sequences. Among noncoding regions the only base change was found in the VP30 gene. Two silent base changes were found in the open reading frame (ORF) encoding NP protein. Nucleotide changes resulting in single-amino-acid exchanges were identified in both NP and L genes. Three other mutations found in VP24 caused amino acid substitutions, which are responsible for larger structural changes of this protein, as indicated by an alteration in electrophoretic mobility. A highly pathogenic EBOV variant K5 from another passaging series showed an amino acid substitution at nearly the same location in the VP24 gene, suggesting the importance of this protein in the adaptation process. In addition, sequence variability of the GP gene was found when plaque-purified clones of EBOV-8mc were analyzed. Three of five viral clones showed insertion of one uridine residue at the GP gene-editing site, which led to a significant change in the expression of virus glycoproteins. This observation suggests that the editing site is a hot spot for insertion and deletion of nucleotides, not only at the level of transcription but also of genome replication. Irrespective of the number of uridine residues at the editing site, all plaque-purified clones of EBOV variant 8mc resembled each other in their pathogenicity for guinea pigs, indicating either the absence or only supportive role of mutations in the GP gene on the adaptation process.
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Affiliation(s)
- V E Volchkov
- Institut für Virologie, Philipps-Universität, Robert-Koch-Strasse 17, Marburg, 35037, Germany.
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Watanabe S, Takada A, Watanabe T, Ito H, Kida H, Kawaoka Y. Functional importance of the coiled-coil of the Ebola virus glycoprotein. J Virol 2000; 74:10194-201. [PMID: 11024148 PMCID: PMC102058 DOI: 10.1128/jvi.74.21.10194-10201.2000] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ebola virus contains a single glycoprotein (GP) that is responsible for receptor binding and membrane fusion and is proteolytically cleaved into disulfide-linked GP1 and GP2 subunits. The GP2 subunit possesses a coiled-coil motif, which plays an important role in the oligomerization and fusion activity of other viral GPs. To determine the functional significance of the coiled-coil motif of GP2, we examined the effects of peptides corresponding to the coiled-coil motif of GP2 on the infectivity of a mutant vesicular stomatitis virus (lacking the receptor-binding/fusion protein) pseudotyped with the Ebola virus GP. A peptide corresponding to the C-terminal helix reduced the infectivity of the pseudotyped virus. We next introduced alanine substitutions into hydrophobic residues in the coiled-coil motif to identify residues important for GP function. None of the substitutions affected GP oligomerization, but some mutations, two in the N-terminal helix and all in the C-terminal helix, reduced the ability of GP to confer infectivity to the mutant vesicular stomatitis virus without affecting the transport of GP to the cell surface, its incorporation into virions, and the production of virus particles. These results indicate that the coiled-coil motif of GP2 plays an important role in facilitating the entry of Ebola virus into host cells and that peptides corresponding to this region could act as efficient antiviral agents.
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Affiliation(s)
- S Watanabe
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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