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Ebola virus disease: In vivo protection provided by the PAMP restricted TLR3 agonist rintatolimod and its mechanism of action. Antiviral Res 2023; 212:105554. [PMID: 36804324 DOI: 10.1016/j.antiviral.2023.105554] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/30/2023] [Accepted: 02/06/2023] [Indexed: 02/18/2023]
Abstract
Ebola virus (EBOV) is a highly infectious and lethal pathogen responsible for sporadic self-limiting clusters of Ebola virus disease (EVD) in Central Africa capable of reaching epidemic status. 100% protection from lethal EBOV-Zaire in Balb/c mice was achieved by rintatolimod (Ampligen) at the well tolerated human clinical dose of 6 mg/kg. The data indicate that the mechanism of action is rintatolimod's dual ability to act as both a competitive decoy for the IID domain of VP35 blocking viral dsRNA sequestration and as a pathogen-associated molecular pattern (PAMP) restricted agonist for direct TLR3 activation but lacking RIG-1-like cytosolic helicase agonist properties. These data show promise for rintatolimod as a prophylactic therapy against human Ebola outbreaks.
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2
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Zinzula L, Mereu AM, Orsini M, Seeleitner C, Bracher A, Nagy I, Baumeister W. Ebola and Marburg virus VP35 coiled-coil validated as antiviral target by tripartite split-GFP complementation. iScience 2022; 25:105354. [PMID: 36325051 PMCID: PMC9619376 DOI: 10.1016/j.isci.2022.105354] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 09/29/2022] [Accepted: 10/11/2022] [Indexed: 11/30/2022] Open
Abstract
Ebola virus (EBOV) and Marburg virus (MARV) are highly pathogenic viruses in humans, against which approved antivirals are lacking. During EBOV and MARV infection, coiled-coil mediated oligomerization is essential for the virion protein 35 (VP35) polymerase co-factor function and type I interferon antagonism, making VP35 coiled-coil an elective drug target. We established a tripartite split-green fluorescent protein (GFP) fluorescence complementation (FC) system based on recombinant GFP-tagged EBOV and MARV VP35, which probes VP35 coiled-coil assembly by monitoring fluorescence on E. coli colonies, or in vitro in 96/384-multiwell. Oligomerization-defective VP35 mutants showed that correct coiled-coil knobs-into-holes pairing within VP35 oligomer is pre-requisite for GFP tags and GFP detector to reconstitute fluorescing full-length GFP. The method was validated by screening a small compound library, which identified Myricetin and 4,5,6,7-Tetrabromobenzotriazole as inhibitors of EBOV and MARV VP35 oligomerization-dependent FC with low-micromolar IC50 values. These findings substantiate the VP35 coiled-coil value as antiviral target. Ebola and Marburg virus VP35 oligomerize via trimeric and tetrameric coiled-coil VP35 coiled-coil assembly triggers fluorescence of a tripartite split-GFP system Mutations perturbing VP35 coiled-coil hamper split-GFP complementation Myricetin and TBBT inhibit split-GFP complementation mediated by VP35 coiled-coil
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Affiliation(s)
- Luca Zinzula
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
- Corresponding author
| | - Angela Maria Mereu
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Massimiliano Orsini
- Istituto Zooprofilattico Sperimentale delle Venezie, Department of Risk Analysis and Public Health Surveillance, Viale dell’Università 10, 35020 Legnaro, Italy
| | - Christine Seeleitner
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Andreas Bracher
- The Max-Planck Institute of Biochemistry, Department of Cellular Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - István Nagy
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Wolfgang Baumeister
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
- Corresponding author
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3
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Corona A, Fanunza E, Salata C, Morwitzer MJ, Distinto S, Zinzula L, Sanna C, Frau A, Daino GL, Quartu M, Taglialatela-Scafati O, Rigano D, Reid S, Mirazimi A, Tramontano E. Cynarin blocks Ebola virus replication by counteracting VP35 inhibition of interferon-beta production. Antiviral Res 2022; 198:105251. [DOI: 10.1016/j.antiviral.2022.105251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 12/16/2021] [Accepted: 01/17/2022] [Indexed: 11/02/2022]
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4
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Fanunza E, Frau A, Corona A, Tramontano E. Insights into Ebola Virus VP35 and VP24 Interferon Inhibitory Functions and their Initial Exploitation as Drug Targets. Infect Disord Drug Targets 2020; 19:362-374. [PMID: 30468131 DOI: 10.2174/1871526519666181123145540] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/14/2018] [Accepted: 11/16/2018] [Indexed: 12/15/2022]
Abstract
Upon viral infection, the interferon (IFN) system triggers potent antiviral mechanisms limiting viral growth and spread. Hence, to sustain their infection, viruses evolved efficient counteracting strategies to evade IFN control. Ebola virus (EBOV), member of the family Filoviridae, is one of the most virulent and deadly pathogen ever faced by humans. The etiological agent of the Ebola Virus Disease (EVD), EBOV can be undoubtedly considered the perfect example of a powerful inhibitor of the host organism immune response activation. Particularly, the efficacious suppression of the IFN cascade contributes to disease progression and severity. Among the EBOVencoded proteins, the Viral Proteins 35 (VP35) and 24 (VP24) are responsible for the EBOV extreme virulence, representing the core of such inhibitory function through which EBOV determines its very effective shield to the cellular immune defenses. VP35 inhibits the activation of the cascade leading to IFN production, while VP24 inhibits the activation of the IFN-stimulated genes. A number of studies demonstrated that both VP35 and VP24 is validated target for drug development. Insights into the structural characteristics of VP35 and VP24 domains revealed crucial pockets exploitable for drug development. Considered the lack of therapy for EVD, restoring the immune activation is a promising approach for drug development. In the present review, we summarize the importance of VP35 and VP24 proteins in counteracting the host IFN cellular response and discuss their potential as druggable viral targets as a promising approach toward attenuation of EBOV virulence.
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Affiliation(s)
- Elisa Fanunza
- Department of Life and Environmental Sciences, University of Cagliari, Sardinia, Italy
| | - Aldo Frau
- Department of Life and Environmental Sciences, University of Cagliari, Sardinia, Italy
| | - Angela Corona
- Department of Life and Environmental Sciences, University of Cagliari, Sardinia, Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Sardinia, Italy.,Genetics and Biomedical Research Institute, National Research Council, Monserrato, Italy
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5
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Shu T, Gan T, Bai P, Wang X, Qian Q, Zhou H, Cheng Q, Qiu Y, Yin L, Zhong J, Zhou X. Ebola virus VP35 has novel NTPase and helicase-like activities. Nucleic Acids Res 2019; 47:5837-5851. [PMID: 31066445 PMCID: PMC6582406 DOI: 10.1093/nar/gkz340] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 04/21/2019] [Accepted: 04/25/2019] [Indexed: 12/13/2022] Open
Abstract
Ebola virus (EBOV) is a non-segmented, negative-sense RNA virus (NNSV) in the family Filoviridae, and is recognized as one of the most lethal pathogens in the planet. For RNA viruses, cellular or virus-encoded RNA helicases play pivotal roles in viral life cycles by remodelling viral RNA structures and/or unwinding viral dsRNA produced during replication. However, no helicase or helicase-like activity has ever been found to associate with any NNSV-encoded proteins, and it is unknown whether the replication of NNSVs requires the participation of any viral or cellular helicase. Here, we show that despite of containing no conserved NTPase/helicase motifs, EBOV VP35 possesses the NTPase and helicase-like activities that can hydrolyse all types of NTPs and unwind RNA helices in an NTP-dependent manner, respectively. Moreover, guanidine hydrochloride, an FDA-approved compound and inhibitor of certain viral helicases, inhibited the NTPase and helicase-like activities of VP35 as well as the replication/transcription of an EBOV minigenome replicon in cells, highlighting the importance of VP35 helicase-like activity during EBOV life cycle. Together, our findings provide the first demonstration of the NTPase/helicase-like activity encoded by EBOV, and would foster our understanding of EBOV and NNSVs.
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Affiliation(s)
- Ting Shu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Tianyu Gan
- Unit of Viral Hepatitis, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, CAS, Shanghai 200031, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Peng Bai
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Xiaotong Wang
- University of Chinese Academy of Sciences, Beijing 100049, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences (CAS), Wuhan, Hubei 430071, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
| | - Qi Qian
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences (CAS), Wuhan, Hubei 430071, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
| | - Hui Zhou
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences (CAS), Wuhan, Hubei 430071, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
| | - Qi Cheng
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Yang Qiu
- University of Chinese Academy of Sciences, Beijing 100049, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences (CAS), Wuhan, Hubei 430071, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
| | - Lei Yin
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Jin Zhong
- Unit of Viral Hepatitis, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, CAS, Shanghai 200031, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
| | - Xi Zhou
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.,University of Chinese Academy of Sciences, Beijing 100049, China.,State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences (CAS), Wuhan, Hubei 430071, China.,Wuhan National Biosafety Laboratory, Mega-Science Center for Bio-Safety Research, CAS, Wuhan, Hubei 430071, China
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6
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Flego M, Frau A, Accardi L, Mallano A, Ascione A, Gellini M, Fanunza E, Vella S, Di Bonito P, Tramontano E. Intracellular human antibody fragments recognizing the VP35 protein of Zaire Ebola filovirus inhibit the protein activity. BMC Biotechnol 2019; 19:64. [PMID: 31488108 PMCID: PMC6727353 DOI: 10.1186/s12896-019-0554-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 08/09/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Ebola hemorrhagic fever is caused by the Ebola filovirus (EBOV), which is one of the most aggressive infectious agents known worldwide. The EBOV pathogenesis starts with uncontrolled viral replication and subversion of both the innate and adaptive host immune response. The multifunctional viral VP35 protein is involved in this process by exerting an antagonistic action against the early antiviral alpha/beta interferon (IFN-α/β) response, and represents a suitable target for the development of strategies to control EBOV infection. Phage display technology permits to select antibodies as single chain Fragment variable (scFv) from an artificial immune system, due to their ability to specifically recognize the antigen of interest. ScFv is ideal for genetic manipulation and to obtain antibody constructs useful for targeting either antigens expressed on cell surface or intracellular antigens if the scFv is expressed as intracellular antibody (intrabody) or delivered into the cells. RESULTS Monoclonal antibodies (mAb) in scFv format specific for the EBOV VP35 were isolated from the ETH-2 library of human recombinant antibodies by phage display technology. Five different clones were identified by sequencing, produced in E.coli and expressed in CHO mammalian cells to be characterized in vitro. All the selected scFvs were able to react with recombinant VP35 protein in ELISA, one of the scFvs being also able to react in Western Blot assay (WB). In addition, all scFvs were expressed in cell cytoplasm as intrabodies; a luciferase reporter gene inhibition assay performed in A549 cells showed that two of the scFvs can significantly hamper the inhibition of the IFN-β-induced RIG-I signaling cascade mediated by EBOV VP35. CONCLUSION Five antibodies in scFv format recognize an active form of EBOV VP35 in ELISA, while one antibody also recognizes VP35 in WB. Two of these scFvs were also able to interfere with the intracellular activity of VP35 in a cell system in vitro. These findings suggest that such antibodies in scFv format might be employed to develop therapeutic molecules able to hamper EBOV infections.
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Affiliation(s)
- Michela Flego
- Istituto Superiore di Sanità (ISS), National Center for Global Health, Viale Regina Elena 299, 00161, Rome, Italy.
| | - Aldo Frau
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554 09042 Monserrato, Cagliari, Italy
| | - Luisa Accardi
- Department of Infectious Diseases, Viral Hepatitis, Oncoviruses and Retroviruses (EVOR) unit, Istituto Superiore di Sanità (ISS), Viale Regina Elena 299, 00161, Rome, Italy
| | - Alessandra Mallano
- Istituto Superiore di Sanità (ISS), National Center for Global Health, Viale Regina Elena 299, 00161, Rome, Italy
| | - Alessandro Ascione
- Istituto Superiore di Sanità (ISS), National Center for Global Health, Viale Regina Elena 299, 00161, Rome, Italy
| | - Mara Gellini
- Istituto Superiore di Sanità (ISS), National Center for Global Health, Viale Regina Elena 299, 00161, Rome, Italy
| | - Elisa Fanunza
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554 09042 Monserrato, Cagliari, Italy
| | - Stefano Vella
- Istituto Superiore di Sanità (ISS), National Center for Global Health, Viale Regina Elena 299, 00161, Rome, Italy
| | - Paola Di Bonito
- Department of Infectious Diseases, Viral Hepatitis, Oncoviruses and Retroviruses (EVOR) unit, Istituto Superiore di Sanità (ISS), Viale Regina Elena 299, 00161, Rome, Italy.
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554 09042 Monserrato, Cagliari, Italy.
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7
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Di Palma F, Daino GL, Ramaswamy VK, Corona A, Frau A, Fanunza E, Vargiu AV, Tramontano E, Ruggerone P. Relevance of Ebola virus VP35 homo-dimerization on the type I interferon cascade inhibition. Antivir Chem Chemother 2019; 27:2040206619889220. [PMID: 31744306 PMCID: PMC6883671 DOI: 10.1177/2040206619889220] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 08/13/2019] [Indexed: 01/10/2023] Open
Abstract
Ebola virus high lethality relies on its ability to efficiently bypass the host innate antiviral response, which senses the viral dsRNA through the RIG-I receptor and induces type I interferon α/β production. In the bypassing action, the Ebola virus protein VP35 plays a pivotal role at multiple levels of the RIG-I cascade, masking the viral 5′-triphosphorylated dsRNA from RIG-I, and interacting with other cascade components. The VP35 type I interferon inhibition is exerted by the C-terminal domain, while the N-terminal domain, containing a coiled-coil region, is primarily required for oligomerization. However, mutations at key VP35 residues L90/93/107A (VP35-3m) in the coiled-coil region were reported to affect oligomerization and reduce type I interferon antagonism, indicating a possible but unclear role of homo-oligomerization on VP35 interaction with the RIG-I pathway components. In this work, we investigated the VP35 dimerization thermodynamics and its contribution to type I interferon antagonism by computational and biological methods. Focusing on the coiled-coil region, we combined coarse-grained and all-atom simulations on wild type VP35 and VP35-3m homo-dimerization. According to our results, wild type VP35 coiled-coil is able to self-assemble into dimers, while VP35-3m coiled-coil shows poor propensity to even dimerize. Free-energy calculations confirmed the key role of L90, L93 and L107 in stabilizing the coiled-coil homo-dimeric structure. In vitro type I interferon antagonism studies, using full-length wild type VP35 and VP35-3m, revealed that VP35 homo-dimerization is an essential preliminary step for dsRNA binding, which appears to be the main factor of the VP35 RIG-I cascade inhibition, while it is not essential to block the other steps.
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Affiliation(s)
- Francesco Di Palma
- Department of Physics, University of Cagliari, Cittadella
Universitaria, Monserrato, Italy
| | - Gian Luca Daino
- Department of Life and Environmental Sciences, University of
Cagliari, Cittadella Universitaria, Monserrato, Italy
| | | | - Angela Corona
- Department of Life and Environmental Sciences, University of
Cagliari, Cittadella Universitaria, Monserrato, Italy
| | - Aldo Frau
- Department of Life and Environmental Sciences, University of
Cagliari, Cittadella Universitaria, Monserrato, Italy
| | - Elisa Fanunza
- Department of Life and Environmental Sciences, University of
Cagliari, Cittadella Universitaria, Monserrato, Italy
| | - Attilio V Vargiu
- Department of Physics, University of Cagliari, Cittadella
Universitaria, Monserrato, Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of
Cagliari, Cittadella Universitaria, Monserrato, Italy
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale
delle Ricerche (CNR), Monserrato, Italy
| | - Paolo Ruggerone
- Department of Physics, University of Cagliari, Cittadella
Universitaria, Monserrato, Italy
- Istituto Officina dei Materiali (CNR-IOM), UOS Cagliari SLACS,
Monserrato, Italy
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8
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Zinzula L, Nagy I, Orsini M, Weyher-Stingl E, Bracher A, Baumeister W. Structures of Ebola and Reston Virus VP35 Oligomerization Domains and Comparative Biophysical Characterization in All Ebolavirus Species. Structure 2018; 27:39-54.e6. [PMID: 30482729 DOI: 10.1016/j.str.2018.09.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 07/18/2018] [Accepted: 09/19/2018] [Indexed: 12/12/2022]
Abstract
The multifunctional virion protein 35 (VP35) of ebolaviruses is a critical determinant of virulence and pathogenesis indispensable for viral replication and host innate immune evasion. Essential for VP35 function is homo-oligomerization via a coiled-coil motif. Here we report crystal structures of VP35 oligomerization domains from the prototypic Ebola virus (EBOV) and the non-pathogenic Reston virus (RESTV), together with a comparative biophysical characterization of the domains from all known species of the Ebolavirus genus. EBOV and RESTV VP35 oligomerization domains form bipartite parallel helix bundles with a canonical coiled coil in the N-terminal half and increased plasticity in the highly conserved C-terminal half. The domain assembles into trimers and tetramers in EBOV, whereas it exclusively forms tetramers in all other ebolavirus species. Substitution of coiled-coil leucine residues critical for immune antagonism leads to aberrant oligomerization. A conserved arginine involved in inter-chain salt bridges stabilizes the VP35 oligomerization domain and modulates between coiled-coil oligomeric states.
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Affiliation(s)
- Luca Zinzula
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - István Nagy
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Massimiliano Orsini
- Istituto Zooprofilattico dell'Abruzzo e del Molise, Campo Boario, 64100 Teramo, Italy
| | - Elisabeth Weyher-Stingl
- The Max-Planck Institute of Biochemistry, Core Facility, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Andreas Bracher
- The Max-Planck Institute of Biochemistry, Department of Cellular Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| | - Wolfgang Baumeister
- The Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, Am Klopferspitz 18, 82152 Martinsried, Germany.
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9
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Daino GL, Frau A, Sanna C, Rigano D, Distinto S, Madau V, Esposito F, Fanunza E, Bianco G, Taglialatela-Scafati O, Zinzula L, Maccioni E, Corona A, Tramontano E. Identification of Myricetin as an Ebola Virus VP35-Double-Stranded RNA Interaction Inhibitor through a Novel Fluorescence-Based Assay. Biochemistry 2018; 57:6367-6378. [PMID: 30298725 DOI: 10.1021/acs.biochem.8b00892] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ebola virus (EBOV) is a filovirus that causes a severe and rapidly progressing hemorrhagic syndrome; a recent epidemic illustrated the urgent need for novel therapeutic agents because no drugs have been approved for treatment of Ebola virus. A key contribution to the high lethality observed during EBOV outbreaks comes from viral evasion of the host antiviral innate immune response in which viral protein VP35 plays a crucial role, blocking interferon type I production, first by masking the viral double-stranded RNA (dsRNA) and preventing its detection by the pattern recognition receptor RIG-I. Aiming to identify inhibitors of the interaction of VP35 with the viral dsRNA, counteracting the VP35 viral innate immune evasion, we established a new methodology for high-yield recombinant VP35 (rVP35) expression and purification and a novel and robust fluorescence-based rVP35-RNA interaction assay ( Z' factor of 0.69). Taking advantage of such newly established methods, we screened a small library of Sardinian natural extracts, identifying Limonium morisianum as the most potent inhibitor extract. A bioguided fractionation led to the identification of myricetin as the component that can inhibit rVP35-dsRNA interaction with an IC50 value of 2.7 μM. Molecular docking studies showed that myricetin interacts with the highly conserved region of the VP35 RNA binding domain, laying the basis for further structural optimization of potent inhibitors of VP35-dsRNA interaction.
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Affiliation(s)
- Gian Luca Daino
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Aldo Frau
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Cinzia Sanna
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Daniela Rigano
- Department of Pharmacy, School of Medicine and Surgery , University of Naples Federico II , Naples 80131 , Italy
| | - Simona Distinto
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Veronica Madau
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Francesca Esposito
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Elisa Fanunza
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Giulia Bianco
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Orazio Taglialatela-Scafati
- Department of Pharmacy, School of Medicine and Surgery , University of Naples Federico II , Naples 80131 , Italy
| | - Luca Zinzula
- The Max-Planck Institute of Biochemistry , Department of Molecular Structural Biology , Martinsried 82152 , Germany
| | - Elias Maccioni
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Angela Corona
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences , University of Cagliari , Cagliari 09042 , Italy.,Istituto di Ricerca Genetica e Biomedica , Consiglio Nazionale delle Ricerche (CNR) , Monserrato 09042 , Italy
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10
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Insights into the homo-oligomerization properties of N-terminal coiled-coil domain of Ebola virus VP35 protein. Virus Res 2018; 247:61-70. [PMID: 29427597 DOI: 10.1016/j.virusres.2018.02.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/30/2018] [Accepted: 02/06/2018] [Indexed: 12/31/2022]
Abstract
The multifunctional Ebola virus (EBOV) VP35 protein is a key determinant of virulence. VP35 is essential for EBOV replication, is a component of the viral RNA polymerase and participates in nucleocapsid formation. Furthermore, VP35 contributes to EBOV evasion of the host innate immune response by suppressing RNA silencing and blocking RIG-I like receptors' pathways that lead to type I interferon (IFN) production. VP35 homo-oligomerization has been reported to be critical for its replicative function and to increase its IFN-antagonism properties. Moreover, homo-oligomerization is mediated by a predicted coiled-coil (CC) domain located within its N-terminal region. Here we report the homo-oligomerization profile of full-length recombinant EBOV VP35 (rVP35) assessed by size-exclusion chromatography and native polyacrylamide gel electrophoresis. Based on our biochemical results and in agreement with previous experimental observations, we have built an in silico 3D model of the so-far structurally unsolved EBOV VP35 CC domain and performed self-assembly homo-oligomerization simulations by means of molecular dynamics. Our model advances the understanding of how VP35 may associate in different homo-oligomeric species, a crucial process for EBOV replication and pathogenicity.
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11
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Di Petrillo A, Fais A, Pintus F, Santos-Buelga C, González-Paramás AM, Piras V, Orrù G, Mameli A, Tramontano E, Frau A. Broad-range potential of Asphodelus microcarpus leaves extract for drug development. BMC Microbiol 2017; 17:159. [PMID: 28709400 PMCID: PMC5513112 DOI: 10.1186/s12866-017-1068-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 07/10/2017] [Indexed: 02/07/2023] Open
Abstract
Background Many plants have been used in traditional medicine for their antibacterial, antifungal, antiprotozoal, antiviral, antidiarrhoeal, analgesic, antimalarial, antioxidant, anti-inflammatory and anticancer activities. In order to find novel antimicrobial and antiviral agents, the aim of the present study was the evaluation of the antibacterial and antibiofilm susceptibility of Asphodelus microcarpus leaves extract. Moreover, the antiviral activity and the phytochemical composition of the active extract were also determined. Methods Antimicrobial and antibiofilm activities of leaves ethanol extract of A. microcarpus were evaluated on 13 different microbial strains. We selected three different sets of microorganisms: (i) Gram-positive bacteria, (ii) Gram-negative bacteria and (iii) yeasts. The potential antiviral activity of A. microcarpus leaves ethanol extract was evaluated with a luciferase reporter gene assay in which the dsRNA-dependent RIG-I-mediated IFN-β activation was inducted or inhibited by the Ebola virus VP35 protein. HPLC-DAD-MS was used to identify phenolic profile of the active extract. Results A. microcarpus leaves extract showed a potent inhibitory activity on Gram-positive bacteria while only a reduced inhibition was observed on Gram-negative bacteria. No activity was detected against Yeasts. The extract also showed an interesting antibiofilm motif on various bacterial strains (E. coli, S. aureus, S. haemolyticus and B. clausii). Moreover, this extract significantly affected the Ebola virus VP35 inhibition of the viral RNA (vRNA) induced IFN response. Conclusions The overall results provide supportive data on the use of A. microcarpus as antimicrobial agent and a potential source of anti-viral natural products. Data collected set the bases for further studies for the identification of single active components and the development of new pharmaceuticals.
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Affiliation(s)
- Amalia Di Petrillo
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, SS 554, Bivio per Sestu, I-09042, Cagliari, Monserrato, Italy
| | - Antonella Fais
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, SS 554, Bivio per Sestu, I-09042, Cagliari, Monserrato, Italy.
| | - Francesca Pintus
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, SS 554, Bivio per Sestu, I-09042, Cagliari, Monserrato, Italy
| | - Celestino Santos-Buelga
- Grupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Facultad de Farmacia, Universidad de Salamanca, Salamanca, Spain
| | - Ana M González-Paramás
- Grupo de Investigación en Polifenoles, Unidad de Nutrición y Bromatología, Facultad de Farmacia, Universidad de Salamanca, Salamanca, Spain
| | - Vincenzo Piras
- Department of Surgical Science, University of Cagliari, 09124, Cagliari, Italy
| | - Germano Orrù
- Department of Surgical Science, University of Cagliari, 09124, Cagliari, Italy
| | - Antonello Mameli
- Department of Surgical Science, University of Cagliari, 09124, Cagliari, Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, SS 554, Bivio per Sestu, I-09042, Cagliari, Monserrato, Italy
| | - Aldo Frau
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, SS 554, Bivio per Sestu, I-09042, Cagliari, Monserrato, Italy
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12
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RNA Binding of Ebola Virus VP30 Is Essential for Activating Viral Transcription. J Virol 2016; 90:7481-7496. [PMID: 27279615 DOI: 10.1128/jvi.00271-16] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 05/31/2016] [Indexed: 01/17/2023] Open
Abstract
UNLABELLED The template for Ebola virus (EBOV) transcription and replication is the helical viral nucleocapsid composed of the viral negative-sense (-) RNA genome, which is complexed by the nucleoprotein (NP), VP35, polymerase L, VP24, and VP30. While viral replication is exerted by polymerase L and its cofactor VP35, EBOV mRNA synthesis is regulated by the viral nucleocapsid protein VP30, an essential EBOV-specific transcription factor. VP30 is a homohexameric phosphoprotein containing a nonconventional zinc finger. The transcriptional support activity of VP30 is strongly influenced by its phosphorylation state. We studied here how RNA binding contributed to VP30's function in transcriptional activation. Using a novel mobility shift assay and the 3'-terminal 154 nucleotides of the EBOV genome as a standard RNA substrate, we detected that RNA binding of VP30 was severely impaired by VP30 mutations that (i) destroy the protein's capability to form homohexamers, (ii) disrupt the integrity of its zinc finger domain, (iii) mimic its fully phosphorylated state, or (iv) alter the putative RNA binding region. RNA binding of the mutant VP30 proteins correlated strongly with their transcriptional support activity. Furthermore, we showed that the interaction between VP30 and the polymerase cofactor VP35 is RNA dependent, while formation of VP30 homohexamers and VP35 homotetramers is not. Our data indicate that RNA binding of VP30 is essential for its transcriptional support activity and stabilizes complexes of VP35/L polymerase with the (-) RNA template to favor productive transcriptional initiation in the presence of termination-active RNA secondary structures. IMPORTANCE Ebola virus causes severe fevers with unusually high case fatality rates. The recent outbreak of Ebola virus in West Africa claimed more than 11,000 lives and threatened to destabilize a whole region because of its dramatic effects on the public health systems. It is currently not completely understood how Ebola virus manages to balance viral transcription and replication in the infected cells. This study shows that transcriptional support activity of the Ebola virus transcription factor VP30 is highly correlated with its ability to bind viral RNA. The interaction between VP30 and VP35, the Ebola virus polymerase cofactor, is dependent on the presence of RNA as well. Our data contribute to the understanding of the dynamic interplay between nucleocapsid proteins and the viral RNA template in order to promote viral RNA synthesis.
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Cannas V, Daino GL, Corona A, Esposito F, Tramontano E. A Luciferase Reporter Gene Assay to Measure Ebola Virus Viral Protein 35-Associated Inhibition of Double-Stranded RNA-Stimulated, Retinoic Acid-Inducible Gene 1-Mediated Induction of Interferon β. J Infect Dis 2015; 212 Suppl 2:S277-81. [PMID: 25926684 DOI: 10.1093/infdis/jiv214] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
During Ebola virus (EBOV) infection, the type I interferon α/β (IFN-α/β) innate immune response is suppressed by EBOV viral protein 35 (VP35), a validated drug target. Identification of EBOV VP35 inhibitors requires a cellular system able to assess the VP35-based inhibitory functions of viral double-stranded RNA (dsRNA) IFN-β induction. We established a miniaturized luciferase gene reporter assay in A549 cells that measures IFN-β induction by viral dsRNA and is dose-dependently inhibited by VP35 expression. When compared to influenza A virus NS1 protein, EBOV VP35 showed improved inhibition of viral dsRNA-based IFN-β induction. This assay can be used to screen for EBOV VP35 inhibitors.
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Affiliation(s)
- Valeria Cannas
- Department of Life and Environmental Sciences, University of Cagliari, Italy
| | - Gian Luca Daino
- Department of Life and Environmental Sciences, University of Cagliari, Italy
| | - Angela Corona
- Department of Life and Environmental Sciences, University of Cagliari, Italy
| | - Francesca Esposito
- Department of Life and Environmental Sciences, University of Cagliari, Italy
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Italy
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14
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Krug RM. Viral proteins that bind double-stranded RNA: countermeasures against host antiviral responses. J Interferon Cytokine Res 2015; 34:464-8. [PMID: 24905203 DOI: 10.1089/jir.2014.0005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Several animal viruses encode proteins that bind double-stranded RNA (dsRNA) to counteract host dsRNA-dependent antiviral responses. This article discusses the structure and function of the dsRNA-binding proteins of influenza A virus and Ebola viruses (EBOVs).
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Affiliation(s)
- Robert M Krug
- Molecular Biosciences, Center of Infectious Disease, Institute for Cellular and Molecular Biology, University of Texas at Austin , Austin, Texas
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15
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Albariño CG, Wiggleton Guerrero L, Spengler JR, Uebelhoer LS, Chakrabarti AK, Nichol ST, Towner JS. Recombinant Marburg viruses containing mutations in the IID region of VP35 prevent inhibition of Host immune responses. Virology 2014; 476:85-91. [PMID: 25531184 PMCID: PMC6461211 DOI: 10.1016/j.virol.2014.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 11/22/2014] [Accepted: 12/02/2014] [Indexed: 12/02/2022]
Abstract
Previous in vitro studies have demonstrated that Ebola and Marburg virus (EBOV and MARV) VP35 antagonize the host cell immune response. Moreover, specific mutations in the IFN inhibitory domain (IID) of EBOV and MARV VP35 that abrogate their interaction with virus-derived dsRNA, lack the ability to inhibit the host immune response. To investigate the role of MARV VP35 in the context of infectious virus, we used our reverse genetics system to generate two recombinant MARVs carrying specific mutations in the IID region of VP35. Our data show that wild-type and mutant viruses grow to similar titers in interferon deficient cells, but exhibit attenuated growth in interferon-competent cells. Furthermore, in contrast to wild-type virus, both MARV mutants were unable to inhibit expression of various antiviral genes. The MARV VP35 mutants exhibit similar phenotypes to those previously described for EBOV, suggesting the existence of a shared immune-modulatory strategy between filoviruses.
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Mitchell WM, Carter WA. The quest for effective Ebola treatment: Ebola VP35 is an evidence-based target for dsRNA drugs. Emerg Microbes Infect 2014; 3:e77. [PMID: 26038500 PMCID: PMC4217096 DOI: 10.1038/emi.2014.77] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 09/22/2014] [Indexed: 12/15/2022]
Affiliation(s)
- William M Mitchell
- Department of Pathology, Microbiology and Immunology, Vanderbilt University , Nashville, TN 37232, USA
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Zinzula L, Tramontano E. Strategies of highly pathogenic RNA viruses to block dsRNA detection by RIG-I-like receptors: hide, mask, hit. Antiviral Res 2013; 100:615-35. [PMID: 24129118 PMCID: PMC7113674 DOI: 10.1016/j.antiviral.2013.10.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/24/2013] [Accepted: 10/04/2013] [Indexed: 12/24/2022]
Abstract
dsRNA species are byproducts of RNA virus replication and/or transcription. Prompt detection of dsRNA by RIG-I like receptors (RLRs) is a hallmark of the innate immune response. RLRs activation triggers production of the type I interferon (IFN)-based antiviral response. Highly pathogenic RNA viruses encode proteins that block the RLRs pathway. Hide, mask and hit are 3 strategies of RNA viruses to avoid immune system activation.
Double-stranded RNA (dsRNA) is synthesized during the course of infection by RNA viruses as a byproduct of replication and transcription and acts as a potent trigger of the host innate antiviral response. In the cytoplasm of the infected cell, recognition of the presence of viral dsRNA as a signature of “non-self” nucleic acid is carried out by RIG-I-like receptors (RLRs), a set of dedicated helicases whose activation leads to the production of type I interferon α/β (IFN-α/β). To overcome the innate antiviral response, RNA viruses encode suppressors of IFN-α/β induction, which block RLRs recognition of dsRNA by means of different mechanisms that can be categorized into: (i) dsRNA binding and/or shielding (“hide”), (ii) dsRNA termini processing (“mask”) and (iii) direct interaction with components of the RLRs pathway (“hit”). In light of recent functional, biochemical and structural findings, we review the inhibition mechanisms of RLRs recognition of dsRNA displayed by a number of highly pathogenic RNA viruses with different disease phenotypes such as haemorrhagic fever (Ebola, Marburg, Lassa fever, Lujo, Machupo, Junin, Guanarito, Crimean-Congo, Rift Valley fever, dengue), severe respiratory disease (influenza, SARS, Hendra, Hantaan, Sin Nombre, Andes) and encephalitis (Nipah, West Nile).
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Affiliation(s)
- Luca Zinzula
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella di Monserrato, SS554, 09042 Monserrato (Cagliari), Italy.
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