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Werner AD, Schauflinger M, Norris MJ, Klüver M, Trodler A, Herwig A, Brandstädter C, Dillenberger M, Klebe G, Heine A, Saphire EO, Becker K, Becker S. The C-terminus of Sudan ebolavirus VP40 contains a functionally important CX nC motif, a target for redox modifications. Structure 2023; 31:1038-1051.e7. [PMID: 37392738 DOI: 10.1016/j.str.2023.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 05/10/2023] [Accepted: 06/06/2023] [Indexed: 07/03/2023]
Abstract
The Ebola virus matrix protein VP40 mediates viral budding and negatively regulates viral RNA synthesis. The mechanisms by which these two functions are exerted and regulated are unknown. Using a high-resolution crystal structure of Sudan ebolavirus (SUDV) VP40, we show here that two cysteines in the flexible C-terminal arm of VP40 form a stabilizing disulfide bridge. Notably, the two cysteines are targets of posttranslational redox modifications and interact directly with the host`s thioredoxin system. Mutation of the cysteines impaired the budding function of VP40 and relaxed its inhibitory role for viral RNA synthesis. In line with these results, the growth of recombinant Ebola viruses carrying cysteine mutations was impaired and the released viral particles were elongated. Our results revealed the exact positions of the cysteines in the C-terminal arm of SUDV VP40. The cysteines and/or their redox status are critically involved in the differential regulation of viral budding and viral RNA synthesis.
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Affiliation(s)
| | | | - Michael J Norris
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Michael Klüver
- Institute for Virology, Philipps-University of Marburg, Marburg, Germany
| | - Anna Trodler
- Institute for Virology, Philipps-University of Marburg, Marburg, Germany
| | - Astrid Herwig
- Institute for Virology, Philipps-University of Marburg, Marburg, Germany
| | - Christina Brandstädter
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University Giessen, Giessen, Germany
| | - Melissa Dillenberger
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University Giessen, Giessen, Germany
| | - Gerhard Klebe
- Institute for Pharmaceutical Chemistry, Philipps-University of Marburg, Marburg, Germany
| | - Andreas Heine
- Institute for Pharmaceutical Chemistry, Philipps-University of Marburg, Marburg, Germany
| | | | - Katja Becker
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University Giessen, Giessen, Germany
| | - Stephan Becker
- Institute for Virology, Philipps-University of Marburg, Marburg, Germany.
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von Creytz I, Gerresheim GK, Lier C, Schneider J, Schauflinger M, Benz M, Kämper L, Rohde C, Eickmann M, Biedenkopf N. Rescue and characterization of the first West African Marburg virus 2021 from Guinea. Heliyon 2023; 9:e19613. [PMID: 37810116 PMCID: PMC10558868 DOI: 10.1016/j.heliyon.2023.e19613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 10/10/2023] Open
Abstract
Marburg virus (MARV) is a causative agent of a severe hemorrhagic fever with high fatality rates endemic in central Africa. Current outbreaks of MARV in Equatorial Guinea and Tanzania underline the relevance of MARV as a public health emergency pathogen. In 2021, the first known human MARV case was confirmed in Guinea, West Africa. Since no infectious virus could be isolated from that fatal case in 2021, we generated recombinant (rec) MARV Guinea by reverse genetics in order to study and characterize this new MARV, which occurred in West Africa for the first time, in terms of its growth properties, detection by antibodies, and therapeutic potential compared to known MARV strains. Our results showed a solid viral replication of recMARV Guinea in human, bat, and monkey cell lines in comparison to other known MARV strains. We further demonstrated that replication of recMARV Guinea in cells can be inhibited by the nucleoside analogue remdesivir. Taken together, we could successfully reconstitute de novo the first West African MARV from Guinea showing similar replication kinetics in cells compared to other central African MARV strains. Our reverse genetics approach has proven successful in characterizing emerging viruses, especially when virus isolates are missing and viral genome sequences are incomplete.
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Affiliation(s)
- Isabel von Creytz
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | | | - Clemens Lier
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Jana Schneider
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | | | - Marcel Benz
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Lennart Kämper
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Cornelius Rohde
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
- German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35043 Marburg, Germany
| | - Markus Eickmann
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Nadine Biedenkopf
- Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany
- German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35043 Marburg, Germany
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Becker DJ, Banerjee A. Coupling field and laboratory studies of immunity and infection in zoonotic hosts. THE LANCET. MICROBE 2023; 4:e285-e287. [PMID: 36878243 PMCID: PMC9984197 DOI: 10.1016/s2666-5247(23)00032-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 03/06/2023]
Affiliation(s)
- Daniel J Becker
- Department of Biology, University of Oklahoma, Norman, OK 73019, USA.
| | - Arinjay Banerjee
- Vaccine and Infectious Disease Organization and Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada; Department of Biology, University of Waterloo, Waterloo, ON, Canada; Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
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Jayaprakash AD, Ronk AJ, Prasad AN, Covington MF, Stein KR, Schwarz TM, Hekmaty S, Fenton KA, Geisbert TW, Basler CF, Bukreyev A, Sachidanandam R. Marburg and Ebola Virus Infections Elicit a Complex, Muted Inflammatory State in Bats. Viruses 2023; 15:350. [PMID: 36851566 PMCID: PMC9958679 DOI: 10.3390/v15020350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/21/2023] [Accepted: 01/24/2023] [Indexed: 01/28/2023] Open
Abstract
The Marburg and Ebola filoviruses cause a severe, often fatal, disease in humans and nonhuman primates but have only subclinical effects in bats, including Egyptian rousettes, which are a natural reservoir of Marburg virus. A fundamental question is why these viruses are highly pathogenic in humans but fail to cause disease in bats. To address this question, we infected one cohort of Egyptian rousette bats with Marburg virus and another cohort with Ebola virus and harvested multiple tissues for mRNA expression analysis. While virus transcripts were found primarily in the liver, principal component analysis (PCA) revealed coordinated changes across multiple tissues. Gene signatures in kidney and liver pointed at induction of vasodilation, reduction in coagulation, and changes in the regulation of iron metabolism. Signatures of immune response detected in spleen and liver indicated a robust anti-inflammatory state signified by macrophages in the M2 state and an active T cell response. The evolutionary divergence between bats and humans of many responsive genes might provide a framework for understanding the differing outcomes upon infection by filoviruses. In this study, we outline multiple interconnected pathways that respond to infection by MARV and EBOV, providing insights into the complexity of the mechanisms that enable bats to resist the disease caused by filoviral infections. The results have the potential to aid in the development of new strategies to effectively mitigate and treat the disease caused by these viruses in humans.
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Affiliation(s)
| | - Adam J. Ronk
- Department of Pathology, the University Texas Medical Branch, Galveston, TX 77555, USA
- Galveston National Laboratory, the University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Abhishek N. Prasad
- Department of Pathology, the University Texas Medical Branch, Galveston, TX 77555, USA
- Galveston National Laboratory, the University of Texas Medical Branch, Galveston, TX 77555, USA
| | | | - Kathryn R. Stein
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Toni M. Schwarz
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Saboor Hekmaty
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Karla A. Fenton
- Galveston National Laboratory, the University of Texas Medical Branch, Galveston, TX 77555, USA
- Department Microbiology & Immunology, the University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Thomas W. Geisbert
- Galveston National Laboratory, the University of Texas Medical Branch, Galveston, TX 77555, USA
- Department Microbiology & Immunology, the University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Christopher F. Basler
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Alexander Bukreyev
- Department of Pathology, the University Texas Medical Branch, Galveston, TX 77555, USA
- Galveston National Laboratory, the University of Texas Medical Branch, Galveston, TX 77555, USA
- Department Microbiology & Immunology, the University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Ravi Sachidanandam
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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Abstract
Ebola virus (EBOV) VP30 regulates viral genome transcription and replication by switching its phosphorylation status. However, the importance of VP30 phosphorylation and dephosphorylation in other viral replication processes such as nucleocapsid and virion assembly is unclear. Interestingly, VP30 is predominantly dephosphorylated by cellular phosphatases in viral inclusions, while it is phosphorylated in the released virions. Thus, uncertainties regarding how VP30 phosphorylation in nucleocapsids is achieved and whether VP30 phosphorylation provides any advantages in later steps in viral replication have arisen. In the present study, to characterize the roles of VP30 phosphorylation in nucleocapsid formation, we used electron microscopic analyses and live cell imaging systems. We identified VP30 localized to the surface of protrusions surrounding nucleoprotein (NP)-forming helical structures in the nucleocapsid, suggesting the involvement in assembly and transport of nucleocapsids. Interestingly, VP30 phosphorylation facilitated its association with nucleocapsid-like structures (NCLSs). On the contrary, VP30 phosphorylation does not influence the transport characteristics and NCLS number leaving from and coming back into viral inclusions, indicating that the phosphorylation status of VP30 is not a prerequisite for NCLS departure. Moreover, the phosphorylation status of VP30 did not cause major differences in nucleocapsid transport in authentic EBOV-infected cells. In the following budding step, the association of VP30 and its phosphorylation status did not influence the budding efficiency of virus-like particles. Taken together, it is plausible that EBOV may utilize the phosphorylation of VP30 for its selective association with nucleocapsids, without affecting nucleocapsid transport and virion budding processes. IMPORTANCE Ebola virus (EBOV) causes severe fevers with unusually high case fatality rates. The nucleocapsid provides the template for viral genome transcription and replication. Thus, understanding the regulatory mechanism behind its formation is important for the development of novel therapeutic approaches. Previously, we established a live-cell imaging system based on the ectopic expression of viral fluorescent fusion proteins, allowing the visualization and characterization of intracytoplasmic transport of nucleocapsid-like structures. EBOV VP30 is an essential transcriptional factor for viral genome synthesis, and, although its role in viral genome transcription and replication is well understood, the functional importance of VP30 phosphorylation in assembly of nucleocapsids is still unclear. Our work determines the localization of VP30 at the surface of ruffled nucleocapsids, which differs from the localization of polymerase in EBOV-infected cells. This study sheds light on the novel role of VP30 phosphorylation in nucleocapsid assembly, which is an important prerequisite for virion formation.
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Bokelmann M, Vogel U, Debeljak F, Düx A, Riesle-Sbarbaro S, Lander A, Wahlbrink A, Kromarek N, Neil S, Couacy-Hymann E, Prescott J, Kurth A. Tolerance and Persistence of Ebola Virus in Primary Cells from Mops condylurus, a Potential Ebola Virus Reservoir. Viruses 2021; 13:v13112186. [PMID: 34834992 PMCID: PMC8622823 DOI: 10.3390/v13112186] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/14/2021] [Accepted: 10/26/2021] [Indexed: 11/16/2022] Open
Abstract
Although there have been documented Ebola virus disease outbreaks for more than 40 years, the natural reservoir host has not been identified. Recent studies provide evidence that the Angolan free-tailed bat (Mops condylurus), an insectivorous microbat, is a possible ebolavirus reservoir. To investigate the potential role of this bat species in the ecology of ebolaviruses, replication, tolerance, and persistence of Ebola virus (EBOV) were investigated in 10 different primary bat cell isolates from M. condylurus. Varying EBOV replication kinetics corresponded to the expression levels of the integral membrane protein NPC1. All primary cells were highly tolerant to EBOV infection without cytopathic effects. The observed persistent EBOV infection for 150 days in lung primary cells, without resultant selective pressure leading to virus mutation, indicate the intrinsic ability of EBOV to persist in this bat species. These results provide further evidence for this bat species to be a likely reservoir of ebolaviruses.
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Affiliation(s)
- Marcel Bokelmann
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Uwe Vogel
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Franka Debeljak
- Department of Infectious Diseases, King’s College London, London WC2R 2LS, UK; (F.D.); (S.N.)
| | - Ariane Düx
- Epidemiology of Highly Pathogenic Microorganisms, Robert Koch Institute, 13353 Berlin, Germany;
| | - Silke Riesle-Sbarbaro
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Angelika Lander
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Annette Wahlbrink
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Nicole Kromarek
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Stuart Neil
- Department of Infectious Diseases, King’s College London, London WC2R 2LS, UK; (F.D.); (S.N.)
| | - Emmanuel Couacy-Hymann
- Laboratoire National d’Appui au Développement Agricole, Bingerville BP 206, Côte d’Ivoire;
| | - Joseph Prescott
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
| | - Andreas Kurth
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany; (M.B.); (U.V.); (S.R.-S.); (A.L.); (A.W.); (N.K.); (J.P.)
- Correspondence:
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Seifert SN, Letko MC, Bushmaker T, Laing ED, Saturday G, Meade-White K, van Doremalen N, Broder CC, Munster VJ. Rousettus aegyptiacus Bats Do Not Support Productive Nipah Virus Replication. J Infect Dis 2020; 221:S407-S413. [PMID: 31682727 PMCID: PMC7199784 DOI: 10.1093/infdis/jiz429] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Nipah virus (NiV) is a bat-borne zoonotic pathogen that can cause severe respiratory distress and encephalitis upon spillover into humans. NiV is capable of infecting a broad range of hosts including humans, pigs, ferrets, dogs, cats, hamsters, and at least 2 genera of bats. Little is known about the biology of NiV in the bat reservoir. In this study, we evaluate the potential for the Egyptian fruit bat (EFB), Rousettus aegyptiacus, to serve as a model organism for studying NiV in bats. Our data suggest that NiV does not efficiently replicate in EFBs in vivo. Furthermore, we show no seroconversion against NiV glycoprotein and a lack of viral replication in primary and immortalized EFB-derived cell lines. Our data show that despite using a conserved target for viral entry, NiV replication is limited in some bat species. We conclude that EFBs are not an appropriate organism to model NiV infection or transmission in bats.
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Affiliation(s)
- Stephanie N Seifert
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Michael C Letko
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Trenton Bushmaker
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Eric D Laing
- Uniformed Services University, Bethesda, Maryland, USA
| | - Greg Saturday
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Kimberly Meade-White
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Neeltje van Doremalen
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | | | - Vincent J Munster
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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The Integrity of the YxxL Motif of Ebola Virus VP24 Is Important for the Transport of Nucleocapsid-Like Structures and for the Regulation of Viral RNA Synthesis. J Virol 2020; 94:JVI.02170-19. [PMID: 32102881 DOI: 10.1128/jvi.02170-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 02/15/2020] [Indexed: 12/15/2022] Open
Abstract
While it is well appreciated that late domains in the viral matrix proteins are crucial to mediate efficient virus budding, little is known about roles of late domains in the viral nucleocapsid proteins. Here, we characterized the functional relevance of a YxxL motif with potential late-domain function in the Ebola virus nucleocapsid protein VP24. Mutations in the YxxL motif had two opposing effects on the functions of VP24. On the one hand, the mutation affected the regulatory function of VP24 in viral RNA transcription and replication, which correlated with an increased incorporation of minigenomes into released transcription- and replication-competent virus-like particles (trVLPs). Consequently, cells infected with those trVLPs showed higher levels of viral transcription. On the other hand, mutations of the YxxL motif greatly impaired the intracellular transport of nucleocapsid-like structures (NCLSs) composed of the viral proteins NP, VP35, and VP24 and the length of released trVLPs. Attempts to rescue recombinant Ebola virus expressing YxxL-deficient VP24 failed, underlining the importance of this motif for the viral life cycle.IMPORTANCE Ebola virus (EBOV) causes a severe fever with high case fatality rates and, so far, no available specific therapy. Understanding the interplay between viral and host proteins is important to identify new therapeutic approaches. VP24 is one of the essential nucleocapsid components and is necessary to regulate viral RNA synthesis and condense viral nucleocapsids before their transport to the plasma membrane. Our functional analyses of the YxxL motif in VP24 suggested that it serves as an interface between nucleocapsid-like structures (NCLSs) and cellular proteins, promoting intracellular transport of NCLSs in an Alix-independent manner. Moreover, the YxxL motif is necessary for the inhibitory function of VP24 in viral RNA synthesis. A failure to rescue EBOV encoding VP24 with a mutated YxxL motif indicated that the integrity of the YxxL motif is essential for EBOV growth. Thus, this motif might represent a potential target for antiviral interference.
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Ebola Virus Produces Discrete Small Noncoding RNAs Independently of the Host MicroRNA Pathway Which Lack RNA Interference Activity in Bat and Human Cells. J Virol 2020; 94:JVI.01441-19. [PMID: 31852785 DOI: 10.1128/jvi.01441-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 12/06/2019] [Indexed: 02/07/2023] Open
Abstract
The question as to whether RNA viruses produce bona fide microRNAs (miRNAs) during infection has been the focus of intense research and debate. Recently, several groups using computational prediction methods have independently reported possible miRNA candidates produced by Ebola virus (EBOV). Additionally, efforts to detect these predicted RNA products in samples from infected animals and humans have produced positive results. However, these studies and their conclusions are predicated on the assumption that these RNA products are actually processed through, and function within, the miRNA pathway. In the present study, we performed the first rigorous assessment of the ability of filoviruses to produce miRNA products during infection of both human and bat cells. Using next-generation sequencing, we detected several candidate miRNAs from both EBOV and the closely related Marburg virus (MARV). Focusing our validation efforts on EBOV, we found evidence contrary to the idea that these small RNA products function as miRNAs. The results of our study are important because they highlight the potential pitfalls of relying on computational methods alone for virus miRNA discovery.IMPORTANCE Here, we report the discovery, via deep sequencing, of numerous noncoding RNAs (ncRNAs) derived from both EBOV and MARV during infection of both bat and human cell lines. In addition to identifying several novel ncRNAs from both viruses, we identified two EBOV ncRNAs in our sequencing data that were near-matches to computationally predicted viral miRNAs reported in the literature. Using molecular and immunological techniques, we assessed the potential of EBOV ncRNAs to function as viral miRNAs. Importantly, we found little evidence supporting this hypothesis. Our work is significant because it represents the first rigorous assessment of the potential for EBOV to encode viral miRNAs and provides evidence contrary to the existing paradigm regarding the biological role of computationally predicted EBOV ncRNAs. Moreover, our work highlights further avenues of research regarding the nature and function of EBOV ncRNAs.
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Abstract
The largest Ebola virus (EBOV) epidemic in West Africa ever caused more than 28,000 cases and 11,000 deaths, and the current EBOV epidemic in the Democratic Republic of the Congo continues, with more than 3,000 cases to date. Therefore, it is essential to develop antivirals against EBOV. Recently, an inhibitor of the cellular phosphatase PP2A-mediated dephosphorylation of the EBOV transcription factor VP30 has been shown to suppress the spread of Ebola virus. Here, we identified the protein kinase SRPK1 as a VP30-specific kinase that phosphorylates serine 29, the same residue that is dephosphorylated by PP2A. SRPK1-mediated phosphorylation of serine 29 enabled primary viral transcription. Mutation of the SRPK1 recognition motif in VP30 resulted in significant growth inhibition of EBOV. Similarly, elevation of the phosphorylation status of serine 29 by overexpression of SRPK1 inhibited EBOV growth, highlighting the importance of reversible phosphorylation of VP30 as a potential therapeutic target. Ebola virus (EBOV) causes a severe and often fatal disease for which no approved vaccines or antivirals are currently available. EBOV VP30 has been described as a viral phosphoprotein, and nonphosphorylated VP30 is essential and sufficient to support secondary transcription in an EBOV-specific minigenome system; however, phosphorylatable serine residues near the N terminus of VP30 are required to support primary viral transcription as well as the reinitiation of VP30-mediated transcription at internal EBOV genes. While the dephosphorylation of VP30 by the cellular phosphatase PP2A was found to be mediated by nucleoprotein, the VP30-specific kinases and the role of phosphorylation remain unknown. Here, we report that serine-arginine protein kinase 1 (SRPK1) and SRPK2 phosphorylate serine 29 of VP30, which is located in an N-terminal R26xxS29 motif. Interaction with VP30 via the R26xxS29 motif recruits SRPK1 into EBOV-induced inclusion bodies, the sites of viral RNA synthesis, and an inhibitor of SRPK1/SRPK2 downregulates primary viral transcription. When the SRPK1 recognition motif of VP30 was mutated in a recombinant EBOV, virus replication was severely impaired. It is presumed that the interplay between SRPK1 and PP2A in the EBOV inclusions provides a comprehensive regulatory circuit to ensure the activity of VP30 in EBOV transcription. Thus, the identification of SRPK1 is an important mosaic stone that completes our picture of the players involved in Ebola virus transcription regulation.
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11
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Bokelmann M, Edenborough K, Hetzelt N, Kreher P, Lander A, Nitsche A, Vogel U, Feldmann H, Couacy-Hymann E, Kurth A. Utility of primary cells to examine NPC1 receptor expression in Mops condylurus, a potential Ebola virus reservoir. PLoS Negl Trop Dis 2020; 14:e0007952. [PMID: 31961874 PMCID: PMC6994141 DOI: 10.1371/journal.pntd.0007952] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 01/31/2020] [Accepted: 11/20/2019] [Indexed: 12/17/2022] Open
Abstract
The significance of the integral membrane protein Niemann-Pick C1 (NPC1) in the ebolavirus entry process has been determined using various cell lines derived from humans, non-human primates and fruit bats. Fruit bats have long been purported as the potential reservoir host for ebolaviruses, however several studies provide evidence that Mops condylurus, an insectivorous microbat, is also an ebolavirus reservoir. NPC1 receptor expression in the context of ebolavirus replication in microbat cells remains unstudied. In order to study Ebola virus (EBOV) cellular entry and replication in M. condylurus, we derived primary and immortalized cell cultures from 12 different organs. The NPC1 receptor expression was characterized by confocal microscopy and flow cytometry comparing the expression levels of M. condylurus primary and immortalized cells, HeLa cells, human embryonic kidney cells and cells from a European microbat species. EBOV replication kinetics was studied for four representative cell cultures using qRT-PCR. The aim was to elucidate the suitability of primary and immortalized cells from different tissues for studying NPC1 receptor expression levels and their potential influence on EBOV replication. The NPC1 receptor expression level in M. condylurus primary cells differed depending on the organ they were derived from and was for most cell types significantly lower than in human cell lines. Immortalized cells showed for most cell types higher expression levels than their corresponding primary cells. Concluding from our infection experiments with EBOV we suggest a potential correlation between NPC1 receptor expression level and virus replication rate in vitro. Although there have been Ebola virus (EBOV) outbreaks for more than 40 years, the animal natural reservoir that maintains this virus in nature has not been identified. Viruses and their respective reservoirs coevolve over millions of years, often without causing diseases in the reservoir itself. Upon entering a new host, infection can have devastating consequences, as in the case of EBOV. To gain entry into cells prior to replication, all ebolaviruses utilize the cellular receptor Niemann-Pick C1 (NPC1). In this study the authors focus their work on the Angolan free-tailed bat (Mops condylurus) as a potential reservoir for EBOV. Cells from various organs of this bat were isolated in culture and tested for the presence of NPC1. Most bat cell types had a lower amount of NPC1 compared to the tested human cells. These bat cells were also less efficiently infected by EBOV, indicating adaptation to EBOV. These results suggest low levels of virus replication in the respective tissues of M. condylurus and might be indicative of a virus-natural reservoir relationship.
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Affiliation(s)
- Marcel Bokelmann
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Kathryn Edenborough
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Nicole Hetzelt
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Petra Kreher
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Angelika Lander
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Andreas Nitsche
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Uwe Vogel
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Heinz Feldmann
- Laboratory of Virology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States of America
| | | | - Andreas Kurth
- Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
- * E-mail:
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12
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Takadate Y, Kondoh T, Igarashi M, Maruyama J, Manzoor R, Ogawa H, Kajihara M, Furuyama W, Sato M, Miyamoto H, Yoshida R, Hill TE, Freiberg AN, Feldmann H, Marzi A, Takada A. Niemann-Pick C1 Heterogeneity of Bat Cells Controls Filovirus Tropism. Cell Rep 2020; 30:308-319.e5. [PMID: 31940478 PMCID: PMC11075117 DOI: 10.1016/j.celrep.2019.12.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 09/15/2019] [Accepted: 12/12/2019] [Indexed: 11/18/2022] Open
Abstract
Fruit bats are suspected to be natural hosts of filoviruses, including Ebola virus (EBOV) and Marburg virus (MARV). Interestingly, however, previous studies suggest that these viruses have different tropisms depending on the bat species. Here, we show a molecular basis underlying the host-range restriction of filoviruses. We find that bat-derived cell lines FBKT1 and ZFBK13-76E show preferential susceptibility to EBOV and MARV, respectively, whereas the other bat cell lines tested are similarly infected with both viruses. In FBKT1 and ZFBK13-76E, unique amino acid (aa) sequences are found in the Niemann-Pick C1 (NPC1) protein, one of the cellular receptors interacting with the filovirus glycoprotein (GP). These aa residues, as well as a few aa differences between EBOV and MARV GPs, are crucial for the differential susceptibility to filoviruses. Taken together, our findings indicate that the heterogeneity of bat NPC1 orthologs is an important factor controlling filovirus species-specific host tropism.
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Affiliation(s)
- Yoshihiro Takadate
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Tatsunari Kondoh
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Manabu Igarashi
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan; Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0020, Japan
| | - Junki Maruyama
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Rashid Manzoor
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Hirohito Ogawa
- Hokudai Center for Zoonosis Control in Zambia, School of Veterinary Medicine, University of Zambia, Lusaka 10101, Zambia; Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka 10101, Zambia
| | - Masahiro Kajihara
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Wakako Furuyama
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, MT 59840, USA
| | - Masahiro Sato
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Hiroko Miyamoto
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Reiko Yoshida
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan
| | - Terence E Hill
- Department of Pathology, The University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Alexander N Freiberg
- Department of Pathology, The University of Texas Medical Branch, Galveston, TX 77555, USA
| | - 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 59840, USA
| | - Andrea Marzi
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, MT 59840, USA
| | - Ayato Takada
- Division of Global Epidemiology, Research Center for Zoonosis Control, Hokkaido University, Sapporo 001-0020, Japan; Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0020, Japan; Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka 10101, Zambia.
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13
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Rohde C, Becker S, Krähling V. Marburg virus regulates the IRE1/XBP1-dependent unfolded protein response to ensure efficient viral replication. Emerg Microbes Infect 2020; 8:1300-1313. [PMID: 31495285 PMCID: PMC6746283 DOI: 10.1080/22221751.2019.1659552] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Viruses regulate cellular signalling pathways to ensure optimal viral replication. During Marburg virus (MARV) infection, large quantities of the viral glycoprotein GP are produced in the ER; this may result in the activation of the unfolded protein response (UPR). The most conserved pathway to trigger UPR is initiated by IRE1. Activation of IRE1 results in auto-phosphorylation, splicing of the XBP1 mRNA and translation of the XBP1s protein. XBP1s binds cis-acting UPR elements (UPRE) which leads to the enhanced expression of genes which should restore ER homeostasis. XBP1u protein is translated, if IRE1 is not activated. Here we show that ectopic expression of MARV GP activated the IRE1-XBP1 axis of UPR as monitored by UPRE luciferase assays. However, while at 24 h of infection with MARV IRE1 was phosphorylated, expression of XBP1s was only slightly enhanced and UPRE activity was not detected. The IRE1-XBP1 axis was not active at 48 h p.i. Co-expression studies of MARV proteins demonstrated that the MARV protein VP30 suppressed UPRE activation. Co-immunoprecipitation analyses revealed an RNA-dependent interaction of VP30 with XBP1u. Knock-out of IRE1 supported MARV infection at late time points. Taken together, these results suggest that efficient MARV propagation requires specific regulation of IRE1 activity.
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Affiliation(s)
- Cornelius Rohde
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
| | - Verena Krähling
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
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14
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Activation of RNase L in Egyptian Rousette Bat-Derived RoNi/7 Cells Is Dependent Primarily on OAS3 and Independent of MAVS Signaling. mBio 2019; 10:mBio.02414-19. [PMID: 31719180 PMCID: PMC6851283 DOI: 10.1128/mbio.02414-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Many RNA viruses that are highly pathogenic in humans are relatively apathogenic in their bat reservoirs, making it important to compare innate immune responses in bats to those well characterized in humans. One such antiviral response is the OAS-RNase L pathway. OASs, upon sensing dsRNA, produce 2-5A, leading to activation of RNase L which degrades viral and host RNA, limiting viral replication. Analysis of Egyptian Rousette bat sequences revealed three OAS genes expressing OAS1, OAS2, and OAS3 proteins. Interferon treatment or viral infection induces all three bat OAS mRNAs. In these bat cells as in human cells, RNase L activation and its antiviral activity are dependent primarily on OAS3 while MAVS signaling is not required. Importantly, our findings indicate the OAS-RNase L system is a primary response to virus rather than a secondary effect of interferon signaling and therefore can be activated early in infection or while interferon signaling is antagonized. Bats are reservoirs for many RNA viruses that are highly pathogenic in humans yet relatively apathogenic in the natural host. It has been suggested that differences in innate immunity are responsible. The antiviral OAS-RNase L pathway is well characterized in humans, but there is little known about its activation and antiviral activity in bats. During infection, OASs, upon sensing double-stranded RNA (dsRNA), produce 2′-5′ oligoadenylates (2-5A), leading to activation of RNase L which degrades viral and host RNA, limiting viral replication. Humans encode three active OASs (OAS1 to -3). Analysis of the Egyptian Rousette bat genome combined with mRNA sequencing from bat RoNi/7 cells revealed three homologous OAS proteins. Interferon alpha treatment or viral infection induced all three OAS mRNAs, but RNase L mRNA is constitutively expressed. Sindbis virus (SINV) or vaccinia virus (VACVΔE3L) infection of wild-type (WT) or OAS1-KO (knockout), OAS2-KO, or MAVS-KO RoNi/7 cells, but not RNase L-KO or OAS3-KO cells, induces robust RNase L activation. SINV replication is 100- to 200-fold higher in the absence of RNase L or OAS3 than in WT cells. However, MAVS-KO had no detectable effect on RNA degradation or replication. Thus, in RoNi/7 bat cells, as in human cells, activation of RNase L during infection and its antiviral activity are dependent primarily on OAS3 while MAVS signaling is not required for the activation of RNase L and restriction of infection. Our findings indicate that OAS proteins serve as pattern recognition receptors (PRRs) to recognize viral dsRNA and that this pathway is a primary response to virus rather than a secondary effect of interferon signaling.
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15
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Wendt L, Bostedt L, Hoenen T, Groseth A. High-throughput screening for negative-stranded hemorrhagic fever viruses using reverse genetics. Antiviral Res 2019; 170:104569. [PMID: 31356830 DOI: 10.1016/j.antiviral.2019.104569] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 06/28/2019] [Accepted: 07/25/2019] [Indexed: 02/06/2023]
Abstract
Viral hemorrhagic fevers (VHFs) cause thousands of fatalities every year, but the treatment options for their management remain very limited. In particular, the development of therapeutic interventions is restricted by the lack of commercial viability of drugs targeting individual VHF agents. This makes approaches like drug repurposing and/or the identification of broad range therapies (i.e. those directed at host responses or common proviral factors) highly attractive. However, the identification of candidates for such antiviral repurposing or of host factors/pathways important for the virus life cycle is reliant on high-throughput screening (HTS). Recently, such screening work has been increasingly facilitated by the availability of reverse genetics-based approaches, including tools such as full-length clone (FLC) systems to generate reporter-expressing viruses or various life cycle modelling (LCM) systems, many of which have been developed and/or greatly improved during the last years. In particular, since LCM systems are capable of modelling specific steps in the life cycle, they are a valuable tool for both targeted screening (i.e. for inhibitors of a specific pathway) and mechanism of action studies. This review seeks to summarize the currently available reverse genetics systems for negative-sense VHF causing viruses (i.e. arenaviruses, bunyaviruses and filoviruses), and to highlight the recent advancements made in applying these systems for HTS to identify either antivirals or new virus-host interactions that might hold promise for the development of future treatments for the infections caused by these deadly but neglected virus groups.
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Affiliation(s)
- Lisa Wendt
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald, Insel Riems, Germany
| | - Linus Bostedt
- Junior Research Group - Arenavirus Biology, Friedrich-Loeffler-Institut, Greifswald, Insel Riems, Germany
| | - Thomas Hoenen
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald, Insel Riems, Germany.
| | - Allison Groseth
- Junior Research Group - Arenavirus Biology, Friedrich-Loeffler-Institut, Greifswald, Insel Riems, Germany.
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16
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Naturally Occurring Single Mutations in Ebola Virus Observably Impact Infectivity. J Virol 2018; 93:JVI.01098-18. [PMID: 30333174 PMCID: PMC6288345 DOI: 10.1128/jvi.01098-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Accepted: 10/04/2018] [Indexed: 12/25/2022] Open
Abstract
During the Ebola virus (EBOV) disease outbreak in West Africa in 2014–2016, it was discovered that several mutations in the virus emerged and became prevalent in the human population. This suggests that these mutations may play a role impacting viral fitness. We investigated three of these previously identified mutations (in the glycoprotein [GP], nucleoprotein [NP], or RNA-dependent RNA polymerase [L]) in cell culture, as well as in mice and ferrets, by generating recombinant viruses (based on an early West African EBOV strain) each carrying one of these mutations. The NP and L mutations appear to decrease virulence, whereas the GP mutation slightly increases virulence but mainly impacts viral tropism. Our results show that these single mutations can impact EBOV virulence in animals and have implications for the rational design of efficacious antiviral therapies against these infections. Sequencing of Ebola virus (EBOV) genomes during the 2014–2016 epidemic identified several naturally occurring, dominant mutations potentially impacting virulence or tropism. In this study, we characterized EBOV variants carrying one of the following substitutions: A82V in the glycoprotein (GP), R111C in the nucleoprotein (NP), or D759G in the RNA-dependent RNA polymerase (L). Compared with the wild-type (WT) EBOV C07 isolate, NP and L mutants conferred a replication advantage in monkey Vero E6, human A549, and insectivorous bat Tb1.Lu cells, while L mutants displayed a disadvantage in human Huh7 cells. The replication of the GP mutant was significantly delayed in Tb1.Lu cells and similar to that of the WT in other cells. The L mutant was less virulent, as evidenced by increased survival for mice and a significantly delayed time to death for ferrets, but increased lengths of the period of EBOV shedding may have contributed to the prolonged epidemic. Our results show that single substitutions can have observable impacts on EBOV pathogenicity and provide a framework for the study of other mutations. IMPORTANCE During the Ebola virus (EBOV) disease outbreak in West Africa in 2014–2016, it was discovered that several mutations in the virus emerged and became prevalent in the human population. This suggests that these mutations may play a role impacting viral fitness. We investigated three of these previously identified mutations (in the glycoprotein [GP], nucleoprotein [NP], or RNA-dependent RNA polymerase [L]) in cell culture, as well as in mice and ferrets, by generating recombinant viruses (based on an early West African EBOV strain) each carrying one of these mutations. The NP and L mutations appear to decrease virulence, whereas the GP mutation slightly increases virulence but mainly impacts viral tropism. Our results show that these single mutations can impact EBOV virulence in animals and have implications for the rational design of efficacious antiviral therapies against these infections.
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17
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Mittler E, Schudt G, Halwe S, Rohde C, Becker S. A Fluorescently Labeled Marburg Virus Glycoprotein as a New Tool to Study Viral Transport and Assembly. J Infect Dis 2018; 218:S318-S326. [DOI: 10.1093/infdis/jiy424] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Eva Mittler
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Gordian Schudt
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Sandro Halwe
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- German Center of Infection Research, Partner Site Giessen-Marburg-Langen, Marburg, Germany
| | - Cornelius Rohde
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- German Center of Infection Research, Partner Site Giessen-Marburg-Langen, Marburg, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- German Center of Infection Research, Partner Site Giessen-Marburg-Langen, Marburg, Germany
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18
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Banerjee A, Misra V, Schountz T, Baker ML. Tools to study pathogen-host interactions in bats. Virus Res 2018; 248:5-12. [PMID: 29454637 PMCID: PMC7114677 DOI: 10.1016/j.virusres.2018.02.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 02/01/2018] [Accepted: 02/12/2018] [Indexed: 11/06/2022]
Abstract
Bats are important reservoir hosts for emerging zoonotic viruses. Viruses detected in bats are difficult to isolate using traditional cell lines. Bat cell lines provide critical tools to dissect host pathogen interactions. Little is known about immune cell populations and their responses in bats. Sharing reagents and cell lines will accelerate research and virus discovery.
Bats are natural reservoirs for a variety of emerging viruses that cause significant disease in humans and domestic animals yet rarely cause clinical disease in bats. The co-evolutionary history of bats with viruses has been hypothesized to have shaped the bat-virus relationship, allowing both to exist in equilibrium. Progress in understanding bat-virus interactions and the isolation of bat-borne viruses has been accelerated in recent years by the development of susceptible bat cell lines. Viral sequences similar to severe acute respiratory syndrome corona virus (SARS-CoV) have been detected in bats, and filoviruses such as Marburg virus have been isolated from bats, providing definitive evidence for the role of bats as the natural host reservoir. Although viruses can be readily detected in bats using molecular approaches, virus isolation is far more challenging. One of the limitations in using traditional culture systems from non-reservoir species is that cell types and culture conditions may not be compatible for isolation of bat-borne viruses. There is, therefore, a need to develop additional bat cell lines that correspond to different cell types, including less represented cell types such as immune cells, and culture them under more physiologically relevant conditions to study virus host interactions and for virus isolation. In this review, we highlight the current progress in understanding bat-virus interactions in bat cell line systems and some of the challenges and limitations associated with cell lines. Future directions to address some of these challenges to better understand host-pathogen interactions in these intriguing mammals are also discussed, not only in relation to viruses but also other pathogens carried by bats including bacteria and fungi.
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Affiliation(s)
- Arinjay Banerjee
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Vikram Misra
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Tony Schountz
- Department of Microbiology, Immunology and Pathology, Arthropod-borne and Infectious Diseases laboratory, Colorado State University, Fort Collins, USA
| | - Michelle L Baker
- CSIRO, Health and Biosecurity Business Unit, Australian Animal Health Laboratory, Geelong, Australia.
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19
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Hoenen T, Brandt J, Caì Y, Kuhn JH, Finch C. Reverse Genetics of Filoviruses. Curr Top Microbiol Immunol 2017; 411:421-445. [PMID: 28918537 DOI: 10.1007/82_2017_55] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Reverse genetics systems are used for the generation of recombinant viruses. For filoviruses, this technology has been available for more than 15 years and has been used to investigate questions regarding the molecular biology, pathogenicity, and host adaptation determinants of these viruses. Further, reporter-expressing, recombinant viruses are increasingly used as tools for screening for and characterization of candidate medical countermeasures. Thus, reverse genetics systems represent powerful research tools. Here we provide an overview of available reverse genetics systems for the generation of recombinant filoviruses, potential applications, and the achievements that have been made using these systems.
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Affiliation(s)
- Thomas Hoenen
- Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany.
| | - Janine Brandt
- Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Yíngyún Caì
- Integrated Research Facility at Fort Detrick (IRF-Frederick), Division of Clinical Research (DCR), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), B-8200 Research Plaza, Fort Detrick, Frederick, MD, 21702, USA
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick (IRF-Frederick), Division of Clinical Research (DCR), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), B-8200 Research Plaza, Fort Detrick, Frederick, MD, 21702, USA.
| | - Courtney Finch
- Integrated Research Facility at Fort Detrick (IRF-Frederick), Division of Clinical Research (DCR), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), B-8200 Research Plaza, Fort Detrick, Frederick, MD, 21702, USA
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20
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Biedenkopf N, Lange-Grünweller K, Schulte FW, Weißer A, Müller C, Becker D, Becker S, Hartmann RK, Grünweller A. The natural compound silvestrol is a potent inhibitor of Ebola virus replication. Antiviral Res 2016; 137:76-81. [PMID: 27864075 DOI: 10.1016/j.antiviral.2016.11.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/10/2016] [Accepted: 11/11/2016] [Indexed: 12/31/2022]
Abstract
The DEAD-box RNA helicase eIF4A, which is part of the heterotrimeric translation initiation complex in eukaryotes, is an important novel drug target in cancer research because its helicase activity is required to unwind extended and highly structured 5'-UTRs of several proto-oncogenes. Silvestrol, a natural compound isolated from the plant Aglaia foveolata, is a highly efficient, non-toxic and specific inhibitor of eIF4A. Importantly, 5'-capped viral mRNAs often contain structured 5'-UTRs as well, which may suggest a dependence on eIF4A for their translation by the host protein synthesis machinery. In view of the recent Ebola virus (EBOV) outbreak in West Africa, the identification of potent antiviral compounds is urgently required. Since Ebola mRNAs are 5'-capped and harbor RNA secondary structures in their extended 5'-UTRs, we initiated a BSL4 study to analyze silvestrol in EBOV-infected Huh-7 cells and in primary human macrophages for its antiviral activity. We observed that silvestrol inhibits EBOV infection at low nanomolar concentrations, as inferred from large reductions of viral titers. This correlated with an almost complete disappearance of EBOV proteins, comparable in effect to the translational shutdown of expression of the proto-oncoprotein PIM1, a cellular kinase known to be affected by silvestrol. Effective silvestrol concentrations were non-toxic in the tested cell systems. Thus, silvestrol appears to be a promising first-line drug for the treatment of acute EBOV and possibly other viral infections.
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Affiliation(s)
- Nadine Biedenkopf
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Str. 2, 35043, Marburg, Germany; Deutsches Zentrum für Infektionsforschung (DZIF) at the Partner Site Gießen-Marburg-Langen, Germany
| | - Kerstin Lange-Grünweller
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037, Marburg, Germany
| | - Falk W Schulte
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037, Marburg, Germany
| | - Aileen Weißer
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037, Marburg, Germany
| | - Christin Müller
- Institut für Medizinische Virologie, Justus-Liebig-Universität Gießen, Schubertstraße 81, 35392, Gießen, Germany; Deutsches Zentrum für Infektionsforschung (DZIF) at the Partner Site Gießen-Marburg-Langen, Germany
| | - Dirk Becker
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Str. 2, 35043, Marburg, Germany; Deutsches Zentrum für Infektionsforschung (DZIF) at the Partner Site Gießen-Marburg-Langen, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Str. 2, 35043, Marburg, Germany; Deutsches Zentrum für Infektionsforschung (DZIF) at the Partner Site Gießen-Marburg-Langen, Germany
| | - Roland K Hartmann
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037, Marburg, Germany
| | - Arnold Grünweller
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037, Marburg, Germany.
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21
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Banadyga L, Dolan MA, Ebihara H. Rodent-Adapted Filoviruses and the Molecular Basis of Pathogenesis. J Mol Biol 2016; 428:3449-66. [PMID: 27189922 PMCID: PMC5010511 DOI: 10.1016/j.jmb.2016.05.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/04/2016] [Accepted: 05/06/2016] [Indexed: 11/29/2022]
Abstract
Ebola, Marburg, and Ravn viruses, all filoviruses, are the causative agents of severe hemorrhagic fever. Much of what we understand about the pathogenesis of filovirus disease is derived from work with animal models, including nonhuman primates, which are considered the "gold standard" filovirus model since they faithfully recapitulate the clinical hallmarks of filovirus disease. However, rodent models, including the mouse, guinea pig, and hamster, also exist for Ebola, Marburg, and Ravn viruses, and although they may not reproduce all the clinical signs of filovirus disease, thanks to their relative ease of use and low cost, they are often the first choice for initial descriptions of virus pathogenesis and evaluation of antiviral prophylactics and therapeutics. Since filoviruses do not cause significant disease in adult, immunocompetent rodents, these models rely on "rodent-adapted" viruses that have been passaged several times through their host until virulence and lethality are achieved. In the process of adaptation, the viruses acquire numerous nucleotide/amino acid mutations that contribute to virulence in their rodent host. Interestingly, virus protein 24 (VP24) and nucleoprotein (NP) appear to be major virulence factors for ebolaviruses in rodents, whereas VP40 appears to be the major virulence factor for marburgviruses. By characterizing these mutations and understanding the molecular mechanisms that lead to the acquisition of virulence, we can gain better insight into the pathogenic processes that underlie filovirus disease in humans. These processes, and the viral and/or cellular proteins that contribute to them, will make attractive targets for the development of novel therapeutics and counter-measures.
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Affiliation(s)
- Logan Banadyga
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA
| | - Michael A Dolan
- Bioinformatics and Computational Biosciences Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hideki Ebihara
- Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
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22
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Schmidt KM, Mühlberger E. Marburg Virus Reverse Genetics Systems. Viruses 2016; 8:E178. [PMID: 27338448 PMCID: PMC4926198 DOI: 10.3390/v8060178] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 12/16/2022] Open
Abstract
The highly pathogenic Marburg virus (MARV) is a member of the Filoviridae family and belongs to the group of nonsegmented negative-strand RNA viruses. Reverse genetics systems established for MARV have been used to study various aspects of the viral replication cycle, analyze host responses, image viral infection, and screen for antivirals. This article provides an overview of the currently established MARV reverse genetic systems based on minigenomes, infectious virus-like particles and full-length clones, and the research that has been conducted using these systems.
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Affiliation(s)
- Kristina Maria Schmidt
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Novel and Emerging Infectious Diseases, Greifswald-Insel Riems 17493, Germany.
| | - Elke Mühlberger
- Department of Microbiology, School of Medicine, Boston University, 620 Albany Street, Boston, MA 02118, USA.
- National Emerging Infectious Diseases Laboratories (NEIDL), Boston University, 620 Albany Street, Boston, MA 02118, USA.
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Ehlen L, Tödtmann J, Specht S, Kallies R, Papies J, Müller MA, Junglen S, Drosten C, Eckerle I. Epithelial cell lines of the cotton rat (Sigmodon hispidus) are highly susceptible in vitro models to zoonotic Bunya-, Rhabdo-, and Flaviviruses. Virol J 2016; 13:74. [PMID: 27142375 PMCID: PMC4855710 DOI: 10.1186/s12985-016-0531-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 04/24/2016] [Indexed: 01/27/2023] Open
Abstract
Background Small mammals such as bats and rodents have been increasingly recognized as reservoirs of novel potentially zoonotic pathogens. However, few in vitro model systems to date allow assessment of zoonotic viruses in a relevant host context. The cotton rat (Sigmodon hispidus) is a New World rodent species that has a long-standing history as an experimental animal model due to its unique susceptibility to human viruses. Furthermore, wild cotton rats are associated with a large variety of known or potentially zoonotic pathogens. Methods A method for the isolation and culture of airway epithelial cell lines recently developed for bats was applied for the generation of rodent airway and renal epithelial cell lines from the cotton rat. Continuous cell lines were characterized for their epithelial properties as well as for their interferon competence. Susceptibility to members of zoonotic Bunya-, Rhabdo-, and Flaviviridae, in particular Rift Valley fever virus (RVFV), vesicular stomatitis virus (VSV), West Nile virus (WNV), and tick-borne encephalitis virus (TBEV) was tested. Furthermore, novel arthropod-derived viruses belonging to the families Bunya-, Rhabdo-, and Mesoniviridae were tested. Results We successfully established airway and kidney epithelial cell lines from the cotton rat, and characterized their epithelial properties. Cells were shown to be interferon-competent. Viral infection assays showed high-titre viral replication of RVFV, VSV, WNV, and TBEV, as well as production of infectious virus particles. No viral replication was observed for novel arthropod-derived members of the Bunya-, Rhabdo-, and Mesoniviridae families in these cell lines. Conclusion In the current study, we showed that newly established cell lines from the cotton rat can serve as host-specific in vitro models for viral infection experiments. These cell lines may also serve as novel tools for virus isolation, as well as for the investigation of virus-host interactions in a relevant host species.
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Affiliation(s)
- Lukas Ehlen
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Jan Tödtmann
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Sabine Specht
- Institute for Medical Microbiology, Immunology & Parasitology (IMMIP), University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany.,Present address: Institute of Laboratory Animal Science, University of Zurich, Zurich, Switzerland
| | - René Kallies
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany.,Present address: Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Jan Papies
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Marcel A Müller
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Sandra Junglen
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Christian Drosten
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany
| | - Isabella Eckerle
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127, Bonn, Germany.
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Dynamic Phosphorylation of VP30 Is Essential for Ebola Virus Life Cycle. J Virol 2016; 90:4914-4925. [PMID: 26937028 DOI: 10.1128/jvi.03257-15] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 02/21/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Ebola virus is the causative agent of a severe fever with high fatality rates in humans and nonhuman primates. The regulation of Ebola virus transcription and replication currently is not well understood. An important factor regulating viral transcription is VP30, an Ebola virus-specific transcription factor associated with the viral nucleocapsid. Previous studies revealed that the phosphorylation status of VP30 impacts viral transcription. Together with NP, L, and the polymerase cofactor VP35, nonphosphorylated VP30 supports viral transcription. Upon VP30 phosphorylation, viral transcription ceases. Phosphorylation weakens the interaction between VP30 and the polymerase cofactor VP35 and/or the viral RNA. VP30 thereby is excluded from the viral transcription complex, simultaneously leading to increased viral replication which is supported by NP, L, and VP35 alone. Here, we use an infectious virus-like particle assay and recombinant viruses to show that the dynamic phosphorylation of VP30 is critical for the cotransport of VP30 with nucleocapsids to the sites of viral RNA synthesis, where VP30 is required to initiate primary viral transcription. We further demonstrate that a single serine residue at amino acid position 29 was sufficient to render VP30 active in primary transcription and to generate a recombinant virus with characteristics comparable to those of wild-type virus. In contrast, the rescue of a recombinant virus with a single serine at position 30 in VP30 was unsuccessful. Our results indicate critical roles for phosphorylated and dephosphorylated VP30 during the viral life cycle. IMPORTANCE The current Ebola virus outbreak in West Africa has caused more than 28,000 cases and 11,000 fatalities. Very little is known regarding the molecular mechanisms of how the Ebola virus transcribes and replicates its genome. Previous investigations showed that the transcriptional support activity of VP30 is activated upon VP30 dephosphorylation. The current study reveals that the situation is more complex and that primary transcription as well as the rescue of recombinant Ebola virus also requires the transient phosphorylation of VP30. VP30 encodes six N-proximal serine residues that serve as phosphorylation acceptor sites. The present study shows that the dynamic phosphorylation of serine at position 29 alone is sufficient to activate primary viral transcription. Our results indicate a series of phosphorylation/dephosphorylation events that trigger binding to and release from the nucleocapsid and transcription complex to be essential for the full activity of VP30.
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Experimental Inoculation of Egyptian Fruit Bats (Rousettus aegyptiacus) with Ebola Virus. Viruses 2016; 8:v8020029. [PMID: 26805873 PMCID: PMC4776184 DOI: 10.3390/v8020029] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 12/30/2015] [Accepted: 01/06/2016] [Indexed: 12/22/2022] Open
Abstract
Colonized Egyptian fruit bats (Rousettus aegyptiacus), originating in South Africa, were inoculated subcutaneously with Ebola virus (EBOV). No overt signs of morbidity, mortality, or gross lesions were noted. Bats seroconverted by Day 10–16 post inoculation (p.i.), with the highest mean anti-EBOV IgG level on Day 28 p.i. EBOV RNA was detected in blood from one bat. In 16 other tissues tested, viral RNA distribution was limited and at very low levels. No seroconversion could be demonstrated in any of the control bats up to 28 days after in-contact exposure to subcutaneously-inoculated bats. The control bats were subsequently inoculated intraperitoneally, and intramuscularly with the same dose of EBOV. No mortality, morbidity or gross pathology was observed in these bats. Kinetics of immune response was similar to that in subcutaneously-inoculated bats. Viral RNA was more widely disseminated to multiple tissues and detectable in a higher proportion of individuals, but consistently at very low levels. Irrespective of the route of inoculation, no virus was isolated from tissues which tested positive for EBOV RNA. Viral RNA was not detected in oral, nasal, ocular, vaginal, penile and rectal swabs from any of the experimental groups.
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A Single Amino Acid Change in the Marburg Virus Matrix Protein VP40 Provides a Replicative Advantage in a Species-Specific Manner. J Virol 2015; 90:1444-54. [PMID: 26581998 DOI: 10.1128/jvi.02670-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 11/12/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Marburg virus (MARV) induces severe hemorrhagic fever in humans and nonhuman primates but only transient nonlethal disease in rodents. However, sequential passages of MARV in rodents boosts infection leading to lethal disease. Guinea pig-adapted MARV contains one mutation in the viral matrix protein VP40 at position 184 (VP40D184N). The contribution of the D184N mutation to the efficacy of replication in a new host is unknown. In the present study, we demonstrated that recombinant MARV containing the D184N mutation in VP40 [rMARVVP40(D184N)] grew to higher titers than wild-type recombinant MARV (rMARVWT) in guinea pig cells. Moreover, rMARVVP40(D184N) displayed higher infectivity in guinea pig cells. Comparative analysis of VP40 functions indicated that neither the interferon (IFN)-antagonistic function nor the membrane binding capabilities of VP40 were affected by the D184N mutation. However, the production of VP40-induced virus-like particles (VLPs) and the recruitment of other viral proteins to the budding site was improved by the D184N mutation in guinea pig cells, which resulted in the higher infectivity of VP40D184N-induced infectious VLPs (iVLPs) compared to that of VP40-induced iVLPs. In addition, the function of VP40 in suppressing viral RNA synthesis was influenced by the D184N mutation specifically in guinea pig cells, thus allowing greater rates of transcription and replication. Our results showed that the improved viral fitness of rMARVVP40(D184N) in guinea pig cells was due to the better viral assembly function of VP40D184N and its lower inhibitory effect on viral transcription and replication rather than modulation of the VP40-mediated suppression of IFN signaling. IMPORTANCE The increased virulence achieved by virus passaging in a new host was accompanied by mutations in the viral genome. Analyzing how these mutations affect the functions of viral proteins and the ability of the virus to grow within new host cells helps in the understanding of the molecular mechanisms increasing virulence. Using a reverse genetics approach, we demonstrated that a single mutation in MARV VP40 detected in a guinea pig-adapted MARV provided a replicative advantage of rMARVVP40(D184N) in guinea pig cells. Our studies show that this replicative advantage of rMARV VP40D184N was based on the improved functions of VP40 in iVLP assembly and in the regulation of transcription and replication rather than on the ability of VP40 to combat the host innate immunity.
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Experimental Inoculation of Egyptian Rousette Bats (Rousettus aegyptiacus) with Viruses of the Ebolavirus and Marburgvirus Genera. Viruses 2015; 7:3420-42. [PMID: 26120867 PMCID: PMC4517108 DOI: 10.3390/v7072779] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 06/12/2015] [Accepted: 06/16/2015] [Indexed: 02/07/2023] Open
Abstract
The Egyptian rousette bat (Rousettus aegyptiacus) is a natural reservoir for marburgviruses and a consistent source of virus spillover to humans. Cumulative evidence suggests various bat species may also transmit ebolaviruses. We investigated the susceptibility of Egyptian rousettes to each of the five known ebolaviruses (Sudan, Ebola, Bundibugyo, Taï Forest, and Reston), and compared findings with Marburg virus. In a pilot study, groups of four juvenile bats were inoculated with one of the ebolaviruses or Marburg virus. In ebolavirus groups, viral RNA tissue distribution was limited, and no bat became viremic. Sudan viral RNA was slightly more widespread, spurring a second, 15-day Sudan virus serial euthanasia study. Low levels of Sudan viral RNA disseminated to multiple tissues at early time points, but there was no viremia or shedding. In contrast, Marburg virus RNA was widely disseminated, with viremia, oral and rectal shedding, and antigen in spleen and liver. This is the first experimental infection study comparing tissue tropism, viral shedding, and clinical and pathologic effects of six different filoviruses in the Egyptian rousette, a known marburgvirus reservoir. Our results suggest Egyptian rousettes are unlikely sources for ebolaviruses in nature, and support a possible single filovirus-single reservoir host relationship.
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28
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El Najjar F, Lampe L, Baker ML, Wang LF, Dutch RE. Analysis of cathepsin and furin proteolytic enzymes involved in viral fusion protein activation in cells of the bat reservoir host. PLoS One 2015; 10:e0115736. [PMID: 25706132 PMCID: PMC4338073 DOI: 10.1371/journal.pone.0115736] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/18/2014] [Indexed: 12/12/2022] Open
Abstract
Bats of different species play a major role in the emergence and transmission of highly pathogenic viruses including Ebola virus, SARS-like coronavirus and the henipaviruses. These viruses require proteolytic activation of surface envelope glycoproteins needed for entry, and cellular cathepsins have been shown to be involved in proteolysis of glycoproteins from these distinct virus families. Very little is currently known about the available proteases in bats. To determine whether the utilization of cathepsins by bat-borne viruses is related to the nature of proteases in their natural hosts, we examined proteolytic processing of several viral fusion proteins in cells derived from two fruit bat species, Pteropus alecto and Rousettus aegyptiacus. Our work shows that fruit bat cells have homologs of cathepsin and furin proteases capable of cleaving and activating both the cathepsin-dependent Hendra virus F and the furin-dependent parainfluenza virus 5 F proteins. Sequence analysis comparing Pteropus alecto furin and cathepsin L to proteases from other mammalian species showed a high degree of conservation; however significant amino acid variation occurs at the C-terminus of Pteropus alecto furin. Further analysis of furin-like proteases from fruit bats revealed that these proteases are catalytically active and resemble other mammalian furins in their response to a potent furin inhibitor. However, kinetic analysis suggests that differences may exist in the cellular localization of furin between different species. Collectively, these results indicate that the unusual role of cathepsin proteases in the life cycle of bat-borne viruses is not due to the lack of active furin-like proteases in these natural reservoir species; however, differences may exist between furin proteases present in fruit bats compared to furins in other mammalian species, and these differences may impact protease usage for viral glycoprotein processing.
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Affiliation(s)
- Farah El Najjar
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Levi Lampe
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Michelle L. Baker
- CSIRO Australian Animal Health Laboratory, East Geelong, Victoria, Australia
| | - Lin-Fa Wang
- CSIRO Australian Animal Health Laboratory, East Geelong, Victoria, Australia
- Program in Emerging Infectious Diseases, Duke–National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Rebecca Ellis Dutch
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
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29
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Dolnik O, Kolesnikova L, Welsch S, Strecker T, Schudt G, Becker S. Interaction with Tsg101 is necessary for the efficient transport and release of nucleocapsids in marburg virus-infected cells. PLoS Pathog 2014; 10:e1004463. [PMID: 25330247 PMCID: PMC4199773 DOI: 10.1371/journal.ppat.1004463] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 09/11/2014] [Indexed: 11/18/2022] Open
Abstract
Endosomal sorting complex required for transport (ESCRT) machinery supports the efficient budding of Marburg virus (MARV) and many other enveloped viruses. Interaction between components of the ESCRT machinery and viral proteins is predominantly mediated by short tetrapeptide motifs, known as late domains. MARV contains late domain motifs in the matrix protein VP40 and in the genome-encapsidating nucleoprotein (NP). The PSAP late domain motif of NP recruits the ESCRT-I protein tumor susceptibility gene 101 (Tsg101). Here, we generated a recombinant MARV encoding NP with a mutated PSAP late domain (rMARV(PSAPmut)). rMARV(PSAPmut) was attenuated by up to one log compared with recombinant wild-type MARV (rMARV(wt)), formed smaller plaques and exhibited delayed virus release. Nucleocapsids in rMARV(PSAPmut)-infected cells were more densely packed inside viral inclusions and more abundant in the cytoplasm than in rMARV(wt)-infected cells. A similar phenotype was detected when MARV-infected cells were depleted of Tsg101. Live-cell imaging analyses revealed that Tsg101 accumulated in inclusions of rMARV(wt)-infected cells and was co-transported together with nucleocapsids. In contrast, rMARV(PSAPmut) nucleocapsids did not display co-localization with Tsg101, had significantly shorter transport trajectories, and migration close to the plasma membrane was severely impaired, resulting in reduced recruitment into filopodia, the major budding sites of MARV. We further show that the Tsg101 interacting protein IQGAP1, an actin cytoskeleton regulator, was recruited into inclusions and to individual nucleocapsids together with Tsg101. Moreover, IQGAP1 was detected in a contrail-like structure at the rear end of migrating nucleocapsids. Down regulation of IQGAP1 impaired release of MARV. These results indicate that the PSAP motif in NP, which enables binding to Tsg101, is important for the efficient actin-dependent transport of nucleocapsids to the sites of budding. Thus, the interaction between NP and Tsg101 supports several steps of MARV assembly before virus fission.
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Affiliation(s)
- Olga Dolnik
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
| | | | - Sonja Welsch
- EMBL Structural and Computational Biology Unit, Heidelberg, Germany
| | - Thomas Strecker
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
| | - Gordian Schudt
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps Universität Marburg, Marburg, Germany
- DZIF, Deutsches Zentrum für Infektionsforschung, Marburg, Germany
- * E-mail:
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30
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Uebelhoer LS, Albariño CG, McMullan LK, Chakrabarti AK, Vincent JP, Nichol ST, Towner JS. High-throughput, luciferase-based reverse genetics systems for identifying inhibitors of Marburg and Ebola viruses. Antiviral Res 2014; 106:86-94. [PMID: 24713118 DOI: 10.1016/j.antiviral.2014.03.018] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 03/28/2014] [Accepted: 03/29/2014] [Indexed: 12/27/2022]
Abstract
Marburg virus (MARV) and Ebola virus (EBOV), members of the family Filoviridae, represent a significant challenge to global public health. Currently, no licensed therapies exist to treat filovirus infections, which cause up to 90% mortality in human cases. To facilitate development of antivirals against these viruses, we established two distinct screening platforms based on MARV and EBOV reverse genetics systems that express secreted Gaussia luciferase (gLuc). The first platform is a mini-genome replicon to screen viral replication inhibitors using gLuc quantification in a BSL-2 setting. The second platform is complementary to the first and expresses gLuc as a reporter gene product encoded in recombinant infectious MARV and EBOV, thereby allowing for rapid quantification of viral growth during treatment with antiviral compounds. We characterized these viruses by comparing luciferase activity to virus production, and validated luciferase activity as an authentic real-time measure of viral growth. As proof of concept, we adapt both mini-genome and infectious virus platforms to high-throughput formats, and demonstrate efficacy of several antiviral compounds. We anticipate that both approaches will prove highly useful in the development of anti-filovirus therapies, as well as in basic research on the filovirus life cycle.
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Affiliation(s)
| | | | | | | | - Joel P Vincent
- Centers for Disease Control and Prevention, Atlanta, USA
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31
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Kuhn JH, Bào Y, Bavari S, Becker S, Bradfute S, Brauburger K, Brister JR, Bukreyev AA, Caì Y, Chandran K, Davey RA, Dolnik O, Dye JM, Enterlein S, Gonzalez JP, Formenty P, Freiberg AN, Hensley LE, Hoenen T, Honko AN, Ignatyev GM, Jahrling PB, Johnson KM, Klenk HD, Kobinger G, Lackemeyer MG, Leroy EM, Lever MS, Mühlberger E, Netesov SV, Olinger GG, Palacios G, Patterson JL, Paweska JT, Pitt L, Radoshitzky SR, Ryabchikova EI, Saphire EO, Shestopalov AM, Smither SJ, Sullivan NJ, Swanepoel R, Takada A, Towner JS, van der Groen G, Volchkov VE, Volchkova VA, Wahl-Jensen V, Warren TK, Warfield KL, Weidmann M, Nichol ST. Virus nomenclature below the species level: a standardized nomenclature for filovirus strains and variants rescued from cDNA. Arch Virol 2014; 159:1229-37. [PMID: 24190508 PMCID: PMC4010566 DOI: 10.1007/s00705-013-1877-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 09/30/2013] [Indexed: 12/12/2022]
Abstract
Specific alterations (mutations, deletions, insertions) of virus genomes are crucial for the functional characterization of their regulatory elements and their expression products, as well as a prerequisite for the creation of attenuated viruses that could serve as vaccine candidates. Virus genome tailoring can be performed either by using traditionally cloned genomes as starting materials, followed by site-directed mutagenesis, or by de novo synthesis of modified virus genomes or parts thereof. A systematic nomenclature for such recombinant viruses is necessary to set them apart from wild-type and laboratory-adapted viruses, and to improve communication and collaborations among researchers who may want to use recombinant viruses or create novel viruses based on them. A large group of filovirus experts has recently proposed nomenclatures for natural and laboratory animal-adapted filoviruses that aim to simplify the retrieval of sequence data from electronic databases. Here, this work is extended to include nomenclature for filoviruses obtained in the laboratory via reverse genetics systems. The previously developed template for natural filovirus genetic variant naming, (/)///-, is retained, but we propose to adapt the type of information added to each field for cDNA clone-derived filoviruses. For instance, the full-length designation of an Ebola virus Kikwit variant rescued from a plasmid developed at the US Centers for Disease Control and Prevention could be akin to "Ebola virus H.sapiens-rec/COD/1995/Kikwit-abc1" (with the suffix "rec" identifying the recombinant nature of the virus and "abc1" being a placeholder for any meaningful isolate designator). Such a full-length designation should be used in databases and the methods section of publications. Shortened designations (such as "EBOV H.sap/COD/95/Kik-abc1") and abbreviations (such as "EBOV/Kik-abc1") could be used in the remainder of the text, depending on how critical it is to convey information contained in the full-length name. "EBOV" would suffice if only one EBOV strain/variant/isolate is addressed.
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Affiliation(s)
- Jens H. Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | - Yīmíng Bào
- Information Engineering Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Sina Bavari
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | | | - Kristina Brauburger
- Department of Microbiology and National Emerging Infectious Diseases Laboratory, Boston University School of Medicine, Boston, Massachusetts, USA
| | - J. Rodney Brister
- Information Engineering Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
| | - Alexander A. Bukreyev
- Department of Pathology and Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, USA
| | - Yíngyún Caì
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Robert A. Davey
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Olga Dolnik
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - John M. Dye
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Sven Enterlein
- Integrated BioTherapeutics, Inc., Gaithersburg, Maryland, USA
| | - Jean-Paul Gonzalez
- Health Department, Institut de Recherche pour le Développement, Marseille, France
- Metabiota, Inc., San Francisco, California, USA
| | | | - Alexander N. Freiberg
- Department of Pathology and Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, USA
| | - Lisa E. Hensley
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | - Thomas Hoenen
- Laboratory for Virology, Division of Intramural Research, National Institute for Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA
| | - Anna N. Honko
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Georgy M. Ignatyev
- Federal State Unitary Company “Microgen Scientific Industrial Company for Immunobiological Medicines”, Ministry of Health of the Russian Federation, Moscow, Russia
| | - Peter B. Jahrling
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | | | - Hans-Dieter Klenk
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Gary Kobinger
- Special Pathogens Program, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada
| | - Matthew G. Lackemeyer
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | - Eric M. Leroy
- Centre International de Recherches Médicales de Franceville, Franceville, Gabon
| | - Mark S. Lever
- Biomedical Sciences Department, Dstl, Porton Down, Salisbury, Wiltshire, UK
| | - Elke Mühlberger
- Department of Microbiology and National Emerging Infectious Diseases Laboratory, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Sergey V. Netesov
- Novosibirsk State University, Novosibirsk, Novosibirsk Region, Russia
| | - Gene G. Olinger
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Gustavo Palacios
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Jean L. Patterson
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Janusz T. Paweska
- Center for Emerging and Zoonotic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Sandringham-Johannesburg, Gauteng, South Africa
| | - Louise Pitt
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Sheli R. Radoshitzky
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | - Elena I. Ryabchikova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Novosibirsk Region, Russia
| | - Erica Ollmann Saphire
- Department of Immunology and Microbial Science and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, USA
| | - Aleksandr M. Shestopalov
- Novosibirsk State University, Novosibirsk, Novosibirsk Region, Russia
- State Research Center of Virology and Biotechnology “Vector”, Koltsovo, Novosibirsk Region, Russia
| | - Sophie J. Smither
- Biomedical Sciences Department, Dstl, Porton Down, Salisbury, Wiltshire, UK
| | - Nancy J. Sullivan
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Robert Swanepoel
- Zoonoses Research Unit, University of Pretoria, Pretoria, South Africa
| | - Ayato Takada
- Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan
| | - Jonathan S. Towner
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | | | - Viktor E. Volchkov
- Laboratoire des Filovirus, Inserm U758, Université de Lyon, UCB-Lyon-1, Ecole-Normale-Supérieure de Lyon, Lyon, France
| | - Valentina A. Volchkova
- Laboratoire des Filovirus, Inserm U758, Université de Lyon, UCB-Lyon-1, Ecole-Normale-Supérieure de Lyon, Lyon, France
| | - Victoria Wahl-Jensen
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, Maryland, USA
| | - Travis K. Warren
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland, USA
| | | | - Manfred Weidmann
- Universitätsmedizin Göttingen, Abteilung Virologie, Göttingen, Germany
| | - Stuart T. Nichol
- Viral Special Pathogens Branch, Division of High-Consequence Pathogens Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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32
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Eckerle I, Lenk M, Ulrich RG. More novel hantaviruses and diversifying reservoir hosts--time for development of reservoir-derived cell culture models? Viruses 2014; 6:951-67. [PMID: 24576845 PMCID: PMC3970132 DOI: 10.3390/v6030951] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/11/2014] [Accepted: 02/15/2014] [Indexed: 12/21/2022] Open
Abstract
Due to novel, improved and high-throughput detection methods, there is a plethora of newly identified viruses within the genus Hantavirus. Furthermore, reservoir host species are increasingly recognized besides representatives of the order Rodentia, now including members of the mammalian orders Soricomorpha/Eulipotyphla and Chiroptera. Despite the great interest created by emerging zoonotic viruses, there is still a gross lack of in vitro models, which reflect the exclusive host adaptation of most zoonotic viruses. The usually narrow host range and genetic diversity of hantaviruses make them an exciting candidate for studying virus-host interactions on a cellular level. To do so, well-characterized reservoir cell lines covering a wide range of bat, insectivore and rodent species are essential. Most currently available cell culture models display a heterologous virus-host relationship and are therefore only of limited value. Here, we review the recently established approaches to generate reservoir-derived cell culture models for the in vitro study of virus-host interactions. These successfully used model systems almost exclusively originate from bats and bat-borne viruses other than hantaviruses. Therefore we propose a parallel approach for research on rodent- and insectivore-borne hantaviruses, taking the generation of novel rodent and insectivore cell lines from wildlife species into account. These cell lines would be also valuable for studies on further rodent-borne viruses, such as orthopox- and arenaviruses.
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Affiliation(s)
- Isabella Eckerle
- Institute of Virology, University of Bonn Medical Centre, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany.
| | - Matthias Lenk
- Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Rainer G Ulrich
- Institute for Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
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Live-cell imaging of Marburg virus-infected cells uncovers actin-dependent transport of nucleocapsids over long distances. Proc Natl Acad Sci U S A 2013; 110:14402-7. [PMID: 23940347 DOI: 10.1073/pnas.1307681110] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Transport of large viral nucleocapsids from replication centers to assembly sites requires contributions from the host cytoskeleton via cellular adaptor and motor proteins. For the Marburg and Ebola viruses, related viruses that cause severe hemorrhagic fevers, the mechanism of nucleocapsid transport remains poorly understood. Here we developed and used live-cell imaging of fluorescently labeled viral and host proteins to characterize the dynamics and molecular requirements of nucleocapsid transport in Marburg virus-infected cells under biosafety level 4 conditions. The study showed a complex actin-based transport of nucleocapsids over long distances from the viral replication centers to the budding sites. Only after the nucleocapsids had associated with the matrix viral protein VP40 at the plasma membrane were they recruited into filopodia and cotransported with host motor myosin 10 toward the budding sites at the tip or side of the long cellular protrusions. Three different transport modes and velocities were identified: (i) Along actin filaments in the cytosol, nucleocapsids were transported at ∼200 nm/s; (ii) nucleocapsids migrated from one actin filament to another at ∼400 nm/s; and (iii) VP40-associated nucleocapsids moved inside filopodia at 100 nm/s. Unique insights into the spatiotemporal dynamics of nucleocapsids and their interaction with the cytoskeleton and motor proteins can lead to novel classes of antivirals that interfere with the trafficking and subsequent release of the Marburg virus from infected cells.
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Sandekian V, Lim D, Prud'homme P, Lemay G. Transient high level mammalian reovirus replication in a bat epithelial cell line occurs without cytopathic effect. Virus Res 2013; 173:327-35. [PMID: 23352882 DOI: 10.1016/j.virusres.2013.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/14/2013] [Accepted: 01/15/2013] [Indexed: 02/07/2023]
Abstract
Mammalian reoviruses exhibit a large host range and infected cells are generally killed; however, most studies examined only a few cell types and host species, and are probably not representative of all possible interactions between virus and host cell. Many questions thus remain concerning the nature of cellular factors that affect viral replication and cell death. In the present work, it was observed that replication of the classical mammalian reovirus serotype 3 Dearing in a bat epithelial cell line, Tb1.Lu, does not result in cell lysis and is rapidly reduced to very low levels. Prior uncoating of virions by chymotrypsin treatment, to generate infectious subviral particles, increased the initial level of infection but without any significant effect on further viral replication or cell survival. Infected cells remain resistant to virus reinfection and secrete an antiviral factor, most likely interferon, that is protective against the unrelated encephalomyocarditis virus. Although, the transformed status of a cell is believed to promote reovirus replication and viral "oncolysis", resistant Tb1.Lu cells exhibit a classical phenotype of transformed cells by forming colonies in semisolid soft agar medium. Further transduction of Tb.Lu cells with a constitutively active Ras oncogene does not seem to affect cell growth or reovirus effect on these cells. Infected Tb1.Lu cells can produce low-level of infectious virus for a long time without any apparent effect, although these cells are resistant to reinfection. The results suggest that Tb1.Lu cells can mount an unusual antiviral response. Specific properties of bat cells may thus be in part responsible for the ability of the animals to act as reservoirs for viruses in general and for novel reoviruses in particular. Their peculiar resistance to cell lysis also makes Tb1.Lu cells an attractive model to study the cellular and viral factors that determine the ability of reovirus to replicate and destroy infected cells.
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Affiliation(s)
- Véronique Sandekian
- Département de microbiologie et immunologie, Université de Montréal, Montréal, Canada H3C 3J7
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Mittler E, Kolesnikova L, Herwig A, Dolnik O, Becker S. Assembly of the Marburg virus envelope. Cell Microbiol 2012. [PMID: 23186212 DOI: 10.1111/cmi.12076] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The key player to assemble the filamentous Marburg virus particles is the matrix protein VP40 which orchestrates recruitment of nucleocapsid complexes and the viral glycoprotein GP to the budding sites at the plasma membrane. Here, VP40 induces the formation of the viral particles, determines their morphology and excludes cellular proteins from the virions. Budding takes place at filopodia in non-polarized cells and at the basolateral cell pole in polarized epithelial cells. Molecular basis of how VP40 exerts its multifunctional role in these different processes is currently under investigation. Here we summarize recent data on structure-function relationships of VP40 and GP in connection with their function in assembly. Questions concerning the complex particle assembly, budding and release remaining enigmatic are addressed. Cytoplasmic domains of viral surface proteins often serve as a connection to the viral matrix protein or as binding sites for further viral or cellular proteins. A cooperation of MARV GP and VP40 building up the viral envelope can be proposed and is discussed in more detail in this review, as the cytoplasmic domain of GP represents an obvious interaction candidate because of its localization adjacent to the VP40 layer. Interestingly, truncation of the short cytoplasmic domain of GP neither inhibited interaction with VP40 nor incorporation of GP into progeny viral particles. Based on reverse genetics we generated recombinant virions expressing a GP mutant without the cytoplasmic tail. Investigations revealed attenuation in virus growth and an obvious defect in entry. Further investigations showed that the truncation of the cytoplasmic domain of GP impaired the structural integrity of the ectodomain, whichconsequently had impact on entry steps downstream of virus binding. Our data indicated that changes in the cytoplasmic domain are relayed over the lipid membrane to alter the function of the ectodomain.
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Affiliation(s)
- Eva Mittler
- Institute of Virology, Philipps University Marburg, Hans-Meerwein-Strasse 2, 35043 Marburg, Germany
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Jordan I, Munster VJ, Sandig V. Authentication of the R06E fruit bat cell line. Viruses 2012; 4:889-900. [PMID: 22754654 PMCID: PMC3386627 DOI: 10.3390/v4050889] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 05/18/2012] [Accepted: 05/21/2012] [Indexed: 11/16/2022] Open
Abstract
Fruit bats and insectivorous bats are believed to provide a natural reservoir for a wide variety of infectious diseases. Several lines of evidence, including the successful isolation of infectious viruses, indicate that Marburg virus and Ravn virus have found a major reservoir in colonies of the Egyptian rousette (Rousettus aegyptiacus). To facilitate molecular studies on virus-reservoir host interactions and isolation of viruses from environmental samples, we established cell lines from primary cells of this animal. The cell lines were given to several laboratories until we realized that a contamination with Vero cells in one of the cultures had occurred. Here we describe a general diagnostic procedure for identification of cross-species contamination with the focus on Vero and Rousettus cell lines, and summarize newly discovered properties of the cell lines that may pertain to pathogen discovery.
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Affiliation(s)
- Ingo Jordan
- ProBioGen AG, Goethestr. 54, Berlin 13086, Germany;
- Author to whom correspondence should be addressed; ; Tel.: +49 30 924006-71; Fax: +49 30 914006-49
| | - Vincent J. Munster
- Rocky Mountain Laboratories, NIAID, NIH, 903 S 4th Street, Hamilton, MT 59840, USA;
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Schmidt KM, Schümann M, Olejnik J, Krähling V, Mühlberger E. Recombinant Marburg virus expressing EGFP allows rapid screening of virus growth and real-time visualization of virus spread. J Infect Dis 2011; 204 Suppl 3:S861-70. [PMID: 21987762 DOI: 10.1093/infdis/jir308] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The generation of recombinant enhanced green fluorescent protein (EGFP)-expressing viruses has significantly improved the study of their life cycle and opened up the possibility for the rapid screening of antiviral drugs. Here we report rescue of a recombinant Marburg virus (MARV) expressing EGFP from an additional transcription unit (ATU). The ATU was inserted between the second and third genes, encoding VP35 and VP40, respectively. Live-cell imaging was used to follow virus spread in real time. EGFP expression was detected at 32 hours postinfection (hpi), and infection of neighboring cells was monitored at 55 hpi. Compared to the parental virus, production of progeny rMARV-EGFP was reduced 4-fold and lower protein levels of VP40, but not nucleoprotein, were observed, indicating a decrease in downstream protein expression due to the insertion of an ATU. Interestingly, EGFP concentrated in viral inclusions in infected cells. This was reproduced by transient expression of both EGFP and other fluorescent proteins along with filovirus nucleocapsid proteins, and may suggest that a general increase in protein synthesis occurs at viral inclusion sites. In conclusion, the EGFP-expressing MARV will be a useful tool not only to monitor virus spread and screen for antiviral compounds, but also to investigate the biology of inclusion body formation.
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Stoltz M, Sundström KB, Hidmark Å, Tolf C, Vene S, Ahlm C, Lindberg AM, Lundkvist Å, Klingström J. A model system for in vitro studies of bank vole borne viruses. PLoS One 2011; 6:e28992. [PMID: 22194969 PMCID: PMC3241689 DOI: 10.1371/journal.pone.0028992] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Accepted: 11/17/2011] [Indexed: 12/24/2022] Open
Abstract
The bank vole (Myodes glareolus) is a common small mammal in Europe and a natural host for several important emerging zoonotic viruses, e.g. Puumala hantavirus (PUUV) that causes hemorrhagic fever with renal syndrome (HFRS). Hantaviruses are known to interfere with several signaling pathways in infected human cells, and HFRS is considered an immune-mediated disease. There is no in vitro-model available for infectious experiments in bank vole cells, nor tools for analyses of bank vole immune activation and responses. Consequently, it is not known if there are any differences in the regulation of virus induced responses in humans compared to natural hosts during infection. We here present an in vitro-model for studies of bank vole borne viruses and their interactions with natural host cell innate immune responses. Bank vole embryonic fibroblasts (VEFs) were isolated and shown to be susceptible for PUUV-infection, including a wild-type PUUV strain (only passaged in bank voles). The significance of VEFs as a model system for bank vole associated viruses was further established by infection studies showing that these cells are also susceptible to tick borne encephalitis, cowpox and Ljungan virus. The genes encoding bank vole IFN-β and Mx2 were partially sequenced and protocols for semi-quantitative RT-PCR were developed. Interestingly, PUUV did not induce an increased IFN-β or Mx2 mRNA expression. Corresponding infections with CPXV and LV induced IFN-β but not Mx2, while TBEV induced both IFN-β and Mx2. In conclusion, VEFs together with protocols developed for detection of bank vole innate immune activation provide valuable tools for future studies of how PUUV and other zoonotic viruses affect cells derived from bank voles compared to human cells. Notably, wild-type PUUV which has been difficult to cultivate in vitro readily infected VEFs, suggesting that embryonic fibroblasts from natural hosts might be valuable for isolation of wild-type hantaviruses.
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Affiliation(s)
- Malin Stoltz
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
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Kuhn JH, Dodd LE, Wahl-Jensen V, Radoshitzky SR, Bavari S, Jahrling PB. Evaluation of perceived threat differences posed by filovirus variants. Biosecur Bioterror 2011; 9:361-71. [PMID: 22070137 DOI: 10.1089/bsp.2011.0051] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the United States, filoviruses (ebolaviruses and marburgviruses) are listed as National Institute of Allergy and Infectious Diseases (NIAID) Category A Priority Pathogens, Select Agents, and Centers for Disease Control and Prevention (CDC) Category A Bioterrorism Agents. In recent months, U.S. biodefense professionals and policy experts have initiated discussions on how to optimize filovirus research in regard to medical countermeasure (ie, diagnostics, antiviral, and vaccine) development. Standardized procedures and reagents could accelerate the independent verification of research results across government agencies and establish baselines for the development of animal models acceptable to regulatory entities, such as the Food and Drug Administration (FDA), while being fiscally responsible. At the root of standardization lies the question of which filovirus strains, variants, or isolates ought to be the prototypes for product development, evaluation, and validation. Here we discuss a rationale for their selection. We conclude that, based on currently available data, filovirus biodefense research ought to focus on the classical taxonomic filovirus prototypes: Marburg virus Musoke in the case of marburgviruses and Ebola virus Mayinga in the case of Zaire ebolaviruses. Arguments have been made in various committees in favor of other variants, such as Marburg virus Angola, Ci67 or Popp, or Ebola virus Kikwit, but these rationales seem to be largely based on anecdotal or unpublished and unverified data, or they may reflect a lack of awareness of important facts about the variants' isolation history and genomic properties.
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Affiliation(s)
- Jens H Kuhn
- National Institutes of Health, National Institute of Allergy and Infectious Diseases, Division of Clinical Research, Integrated Research Facility at Fort Detrick, Frederick, Maryland, USA
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40
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Kühl A, Hoffmann M, Müller MA, Munster VJ, Gnirss K, Kiene M, Tsegaye TS, Behrens G, Herrler G, Feldmann H, Drosten C, Pöhlmann S. Comparative analysis of Ebola virus glycoprotein interactions with human and bat cells. J Infect Dis 2011; 204 Suppl 3:S840-9. [PMID: 21987760 PMCID: PMC3189982 DOI: 10.1093/infdis/jir306] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Infection with Ebola virus (EBOV) causes hemorrhagic fever in humans with high case-fatality rates. The EBOV-glycoprotein (EBOV-GP) facilitates viral entry and promotes viral release from human cells. African fruit bats are believed not to develop disease upon EBOV infection and have been proposed as a natural reservoir of EBOV. We compared EBOV-GP interactions with human cells and cells from African fruit bats. We found that susceptibility to EBOV-GP-dependent infection was not limited to bat cells from potential reservoir species, and we observed that GP displayed similar biological properties in human and bat cells. The only exception was GP localization, which was to a greater extent intracellular in bat cells as compared to human cells. Collectively, our results suggest that GP interactions with fruit bat and human cells are similar and do not limit EBOV tropism for certain bat species.
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Affiliation(s)
- Annika Kühl
- Institute of Virology, Hannover Medical School, Germany
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Hoenen T, Groseth A, de Kok-Mercado F, Kuhn JH, Wahl-Jensen V. Minigenomes, transcription and replication competent virus-like particles and beyond: reverse genetics systems for filoviruses and other negative stranded hemorrhagic fever viruses. Antiviral Res 2011; 91:195-208. [PMID: 21699921 DOI: 10.1016/j.antiviral.2011.06.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 06/02/2011] [Accepted: 06/08/2011] [Indexed: 12/27/2022]
Abstract
Reverse-genetics systems are powerful tools enabling researchers to study the replication cycle of RNA viruses, including filoviruses and other hemorrhagic fever viruses, as well as to discover new antivirals. They include full-length clone systems as well as a number of life cycle modeling systems. Full-length clone systems allow for the generation of infectious, recombinant viruses, and thus are an important tool for studying the virus replication cycle in its entirety. In contrast, life cycle modeling systems such as minigenome and transcription and replication competent virus-like particle systems can be used to simulate and dissect parts of the virus life cycle outside of containment facilities. Minigenome systems are used to model viral genome replication and transcription, whereas transcription and replication competent virus-like particle systems also model morphogenesis and budding as well as infection of target cells. As such, these modeling systems have tremendous potential to further the discovery and screening of new antivirals targeting hemorrhagic fever viruses. This review provides an overview of currently established reverse genetics systems for hemorrhagic fever-causing negative-sense RNA viruses, with a particular emphasis on filoviruses, and the potential application of these systems for antiviral research.
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Affiliation(s)
- Thomas Hoenen
- Laboratory of Virology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA; Department of Virology, Philipps University Marburg, Marburg, Germany
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