1
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Shewring JR, Hodgson L, Bryant HL, Bullough PA, Weinstein JA, Verkade P. Refining a correlative light electron microscopy workflow using luminescent metal complexes. Methods Cell Biol 2021; 162:69-87. [PMID: 33707023 DOI: 10.1016/bs.mcb.2020.12.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The potential for increasing the application of Correlative Light Electron Microscopy (CLEM) technologies in life science research is hindered by the lack of suitable molecular probes that are emissive, photostable, and scatter electrons well. Most brightly fluorescent organic molecules are intrinsically poor electron-scatterers, while multi-metallic compounds scatter electrons well but are usually non-luminescent. Thus, the goal of CLEM to image the same object of interest on the continuous scale from hundreds of microns to nanometers remains a major challenge partially due to requirements for a single probe to be suitable for light (LM) and electron microscopy (EM). Some of the main CLEM probes, based on gold nanoparticles appended with fluorophores and quantum dots (QD) have presented significant drawbacks. Here we present an Iridium-based luminescent metal complex (Ir complex 1) as a probe and describe how we have developed a CLEM workflow based on such metal complexes.
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Affiliation(s)
| | - Lorna Hodgson
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom
| | - Helen L Bryant
- Department of Oncology, University of Sheffield, Sheffield, United Kingdom
| | - Per A Bullough
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom
| | - Julia A Weinstein
- Department of Chemistry, University of Sheffield, Sheffield, United Kingdom
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom.
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2
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Sachse M, Fernández de Castro I, Tenorio R, Risco C. The viral replication organelles within cells studied by electron microscopy. Adv Virus Res 2019; 105:1-33. [PMID: 31522702 PMCID: PMC7112055 DOI: 10.1016/bs.aivir.2019.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Transmission electron microscopy (TEM) has been crucial to study viral infections. As a result of recent advances in light and electron microscopy, we are starting to be aware of the variety of structures that viruses assemble inside cells. Viruses often remodel cellular compartments to build their replication factories. Remarkably, viruses are also able to induce new membranes and new organelles. Here we revise the most relevant imaging technologies to study the biogenesis of viral replication organelles. Live cell microscopy, correlative light and electron microscopy, cryo-TEM, and three-dimensional imaging methods are unveiling how viruses manipulate cell organization. In particular, methods for molecular mapping in situ in two and three dimensions are revealing how macromolecular complexes build functional replication complexes inside infected cells. The combination of all these imaging approaches is uncovering the viral life cycle events with a detail never seen before.
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Affiliation(s)
- Martin Sachse
- Unité Technologie et service BioImagerie Ultrastructurale, Institut Pasteur, Paris, France.
| | | | - Raquel Tenorio
- Cell Structure Laboratory, National Center for Biotechnology, CSIC, Madrid, Spain
| | - Cristina Risco
- Cell Structure Laboratory, National Center for Biotechnology, CSIC, Madrid, Spain.
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3
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Götte B, Panas MD, Hellström K, Liu L, Samreen B, Larsson O, Ahola T, McInerney GM. Separate domains of G3BP promote efficient clustering of alphavirus replication complexes and recruitment of the translation initiation machinery. PLoS Pathog 2019; 15:e1007842. [PMID: 31199850 PMCID: PMC6594655 DOI: 10.1371/journal.ppat.1007842] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 06/26/2019] [Accepted: 05/15/2019] [Indexed: 12/15/2022] Open
Abstract
G3BP-1 and -2 (hereafter referred to as G3BP) are multifunctional RNA-binding proteins involved in stress granule (SG) assembly. Viruses from diverse families target G3BP for recruitment to replication or transcription complexes in order to block SG assembly but also to acquire pro-viral effects via other unknown functions of G3BP. The Old World alphaviruses, including Semliki Forest virus (SFV) and chikungunya virus (CHIKV) recruit G3BP into viral replication complexes, via an interaction between FGDF motifs in the C-terminus of the viral non-structural protein 3 (nsP3) and the NTF2-like domain of G3BP. To study potential proviral roles of G3BP, we used human osteosarcoma (U2OS) cell lines lacking endogenous G3BP generated using CRISPR-Cas9 and reconstituted with a panel of G3BP1 mutants and truncation variants. While SFV replicated with varying efficiency in all cell lines, CHIKV could only replicate in cells expressing G3BP1 variants containing both the NTF2-like and the RGG domains. The ability of SFV to replicate in the absence of G3BP allowed us to study effects of different domains of the protein. We used immunoprecipitation to demonstrate that that both NTF2-like and RGG domains are necessary for the formation a complex between nsP3, G3BP1 and the 40S ribosomal subunit. Electron microscopy of SFV-infected cells revealed that formation of nsP3:G3BP1 complexes via the NTF2-like domain was necessary for clustering of cytopathic vacuoles (CPVs) and that the presence of the RGG domain was necessary for accumulation of electron dense material containing G3BP1 and nsP3 surrounding the CPV clusters. Clustered CPVs also exhibited localised high levels of translation of viral mRNAs as detected by ribopuromycylation staining. These data confirm that G3BP is a ribosomal binding protein and reveal that alphaviral nsP3 uses G3BP to concentrate viral replication complexes and to recruit the translation initiation machinery, promoting the efficient translation of viral mRNAs. In order to repel viral infections, cells activate stress responses. One such response involves inhibition of translation and restricted availability of the translation machinery via the formation of stress granules. However, the host translation machinery is absolutely essential for synthesis of viral proteins and consequently viruses have developed a broad spectrum of strategies to circumvent this restriction. Old World alphaviruses, such as Semliki Forest virus (SFV) and chikungunya virus (CHIKV), interfere with stress granule formation by sequestration of G3BP, a stress granule nucleating protein, mediated by the viral non-structural protein 3 (nsP3). Here we show that nsP3:G3BP complexes engage factors of the host translation machinery, which during the course of infection accumulate in the vicinity of viral replication complexes. Accordingly, we demonstrate that the nsP3:G3BP interaction is required for high localized translational activity around viral replication complexes. We find the RGG domain of G3BP to be essential for the recruitment of the host translation machinery. In cells expressing mutant G3BP lacking the RGG domain, SFV replication was attenuated, but detectable, while CHIKV was essentially non-viable. Our data demonstrate a novel mechanism by which viruses can recruit factors of the translation machinery in a G3BP-dependent manner.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Line, Tumor
- Chikungunya Fever/genetics
- Chikungunya Fever/metabolism
- Chikungunya Fever/pathology
- Chikungunya virus/physiology
- Cricetinae
- DNA Helicases/genetics
- DNA Helicases/metabolism
- Humans
- Peptide Chain Initiation, Translational
- Poly-ADP-Ribose Binding Proteins/genetics
- Poly-ADP-Ribose Binding Proteins/metabolism
- Protein Domains
- RNA Helicases/genetics
- RNA Helicases/metabolism
- RNA Recognition Motif Proteins/genetics
- RNA Recognition Motif Proteins/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- RNA-Binding Proteins
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Semliki forest virus/physiology
- Virus Replication
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Affiliation(s)
- Benjamin Götte
- Department of Microbiology, Tumor and Cell Biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Marc D. Panas
- Department of Microbiology, Tumor and Cell Biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Kirsi Hellström
- University of Helsinki, Department of Microbiology, Faculty of Agriculture and Forestry, Helsinki, Finland
| | - Lifeng Liu
- Department of Microbiology, Tumor and Cell Biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Baila Samreen
- Department of Oncology-Pathology, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Ola Larsson
- Department of Oncology-Pathology, Science for Life Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Tero Ahola
- University of Helsinki, Department of Microbiology, Faculty of Agriculture and Forestry, Helsinki, Finland
- * E-mail: (GMM); (TA)
| | - Gerald M. McInerney
- Department of Microbiology, Tumor and Cell Biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
- * E-mail: (GMM); (TA)
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4
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García-Serradilla M, Risco C, Pacheco B. Drug repurposing for new, efficient, broad spectrum antivirals. Virus Res 2019; 264:22-31. [PMID: 30794895 PMCID: PMC7114681 DOI: 10.1016/j.virusres.2019.02.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/18/2019] [Accepted: 02/18/2019] [Indexed: 12/26/2022]
Abstract
Emerging viruses are a major threat to human health. Recent outbreaks have emphasized the urgent need for new antiviral treatments. For several pathogenic viruses, considerable efforts have focused on vaccine development. However, during epidemics infected individuals need to be treated urgently. High-throughput screening of clinically tested compounds provides a rapid means to identify undiscovered, antiviral functions for well-characterized therapeutics. Repurposed drugs can bypass part of the early cost and time needed for validation and authorization. In this review we describe recent efforts to find broad spectrum antivirals through drug repurposing. We have chosen several candidates and propose strategies to understand their mechanism of action and to determine how resistance to antivirals develops in infected cells.
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Affiliation(s)
- Moisés García-Serradilla
- Cell Structure Laboratory, National Center for Biotechnology, National Research Council, CNB-CSIC, Darwin 3, UAM, campus de Cantoblanco, 28049 Madrid, Spain
| | - Cristina Risco
- Cell Structure Laboratory, National Center for Biotechnology, National Research Council, CNB-CSIC, Darwin 3, UAM, campus de Cantoblanco, 28049 Madrid, Spain.
| | - Beatriz Pacheco
- Cell Structure Laboratory, National Center for Biotechnology, National Research Council, CNB-CSIC, Darwin 3, UAM, campus de Cantoblanco, 28049 Madrid, Spain.
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5
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Richert-Pöggeler KR, Franzke K, Hipp K, Kleespies RG. Electron Microscopy Methods for Virus Diagnosis and High Resolution Analysis of Viruses. Front Microbiol 2019; 9:3255. [PMID: 30666247 PMCID: PMC6330349 DOI: 10.3389/fmicb.2018.03255] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 12/14/2018] [Indexed: 01/29/2023] Open
Abstract
The term "virosphere" describes both the space where viruses are found and the space they influence, and can extend to their impact on the environment, highlighting the complexity of the interactions involved. Studying the biology of viruses and the etiology of virus disease is crucial to the prevention of viral disease, efficient and reliable virus diagnosis, and virus control. Electron microscopy (EM) is an essential tool in the detection and analysis of virus replication. New EM methods and ongoing technical improvements offer a broad spectrum of applications, allowing in-depth investigation of viral impact on not only the host but also the environment. Indeed, using the most up-to-date electron cryomicroscopy methods, such investigations are now close to atomic resolution. In combination with bioinformatics, the transition from 2D imaging to 3D remodeling allows structural and functional analyses that extend and augment our knowledge of the astonishing diversity in virus structure and lifestyle. In combination with confocal laser scanning microscopy, EM enables live imaging of cells and tissues with high-resolution analysis. Here, we describe the pivotal role played by EM in the study of viruses, from structural analysis to the biological relevance of the viral metagenome (virome).
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Affiliation(s)
- Katja R. Richert-Pöggeler
- Federal Research Center for Cultivated Plants, Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute, Braunschweig, Germany
| | - Kati Franzke
- Institute of Infectiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Katharina Hipp
- Electron Microscopy Facility, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Regina G. Kleespies
- Federal Research Centre for Cultivated Plants, Institute for Biological Control, Julius Kühn Institute, Darmstadt, Germany
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6
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The RNA Capping Enzyme Domain in Protein A is Essential for Flock House Virus Replication. Viruses 2018; 10:v10090483. [PMID: 30205593 PMCID: PMC6165433 DOI: 10.3390/v10090483] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 09/05/2018] [Accepted: 09/05/2018] [Indexed: 01/18/2023] Open
Abstract
The nodavirus flock house virus (FHV) and the alphavirus Semliki Forest virus (SFV) show evolutionarily intriguing similarities in their replication complexes and RNA capping enzymes. In this study, we first established an efficient FHV trans-replication system in mammalian cells, which disjoins protein expression from viral RNA synthesis. Following transfection, FHV replicase protein A was associated with mitochondria, whose outer surface displayed pouch-like invaginations with a ‘neck’ structure opening towards the cytoplasm. In mitochondrial pellets from transfected cells, high-level synthesis of both genomic and subgenomic RNA was detected in vitro and the newly synthesized RNA was of positive polarity. Secondly, we initiated the study of the putative RNA capping enzyme domain in protein A by mutating the conserved amino acids H93, R100, D141, and W215. RNA replication was abolished for all mutants inside cells and in vitro except for W215A, which showed reduced replication. Transfection of capped RNA template did not rescue the replication activity of the mutants. Comparing the efficiency of SFV and FHV trans-replication systems, the FHV system appeared to produce more RNA. Using fluorescent marker proteins, we demonstrated that both systems could replicate in the same cell. This work may facilitate the comparative analysis of FHV and SFV replication.
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7
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Remenyi R, Gao Y, Hughes RE, Curd A, Zothner C, Peckham M, Merits A, Harris M. Persistent Replication of a Chikungunya Virus Replicon in Human Cells Is Associated with Presence of Stable Cytoplasmic Granules Containing Nonstructural Protein 3. J Virol 2018; 92:e00477-18. [PMID: 29875241 PMCID: PMC6069192 DOI: 10.1128/jvi.00477-18] [Citation(s) in RCA: 21] [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] [Received: 03/23/2018] [Accepted: 05/25/2018] [Indexed: 12/25/2022] Open
Abstract
Chikungunya virus (CHIKV), a mosquito-borne human pathogen, causes a disabling disease characterized by severe joint pain that can persist for weeks, months, or even years in patients. The nonstructural protein 3 (nsP3) plays essential roles during acute infection, but little is known about the function of nsP3 during chronic disease. Here, we used subdiffraction multicolor microscopy for spatial and temporal analysis of CHIKV nsP3 within human cells that persistently replicate replicon RNA. Round cytoplasmic granules of various sizes (i) contained nsP3 and stress granule assembly factors 1 and 2 (G3BP1/2), (ii) were next to double-stranded RNA foci and nsP1-positive structures, and (iii) were close to the nuclear membrane and the nuclear pore complex protein Nup98. Analysis of protein turnover and mobility by live-cell microscopy revealed that the granules could persist for hours to days, accumulated newly synthesized protein, and moved through the cytoplasm at various speeds. The granules also had a static internal architecture and were stable in cell lysates. Refractory cells that had cleared the noncytotoxic replicon regained the ability to respond to arsenite-induced stress. In summary, nsP3 can form uniquely stable granular structures that persist long-term within the host cell. This continued presence of viral and cellular protein complexes has implications for the study of the pathogenic consequences of lingering CHIKV infection and the development of strategies to mitigate the burden of chronic musculoskeletal disease brought about by a medically important arthropod-borne virus (arbovirus).IMPORTANCE Chikungunya virus (CHIKV) is a reemerging alphavirus transmitted by mosquitos and causes transient sickness but also chronic disease affecting muscles and joints. No approved vaccines or antivirals are available. Thus, a better understanding of the viral life cycle and the role of viral proteins can aid in identifying new therapeutic targets. Advances in microscopy and development of noncytotoxic replicons (A. Utt, P. K. Das, M. Varjak, V. Lulla, A. Lulla, A. Merits, J Virol 89:3145-3162, 2015, https://doi.org/10.1128/JVI.03213-14) have allowed researchers to study viral proteins within controlled laboratory environments over extended durations. Here we established human cells that stably replicate replicon RNA and express tagged nonstructural protein 3 (nsP3). The ability to track nsP3 within the host cell and during persistent replication can benefit fundamental research efforts to better understand long-term consequences of the persistence of viral protein complexes and thereby provide the foundation for new therapeutic targets to control CHIKV infection and treat chronic disease symptoms.
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Affiliation(s)
- Roland Remenyi
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Yanni Gao
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Ruth E Hughes
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Alistair Curd
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Carsten Zothner
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Michelle Peckham
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Mark Harris
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
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8
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The application of CorrSight™ in correlative light and electron microscopy of vitrified biological specimens. BIOPHYSICS REPORTS 2018. [DOI: 10.1007/s41048-018-0059-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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9
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Lutz M, Engelbrecht L, Laurie A, Dyayiya N. Using CLEM to investigate the distribution of nano-sized antimicrobial agents within an EVOH matrix. INTERNATIONAL JOURNAL OF POLYMER ANALYSIS AND CHARACTERIZATION 2018. [DOI: 10.1080/1023666x.2018.1426157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Marietjie Lutz
- Department of Chemistry and Polymer Science, Stellenbosch University, Stellenbosch, South Africa
| | - Lize Engelbrecht
- Central Analytical Facilities, Stellenbosch University, Stellenbosch, South Africa
| | - Angelique Laurie
- Central Analytical Facilities, Stellenbosch University, Stellenbosch, South Africa
| | - Nelisa Dyayiya
- Department of Chemistry and Polymer Science, Stellenbosch University, Stellenbosch, South Africa
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10
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Lowen RG, Bocan TM, Kane CD, Cazares LH, Kota KP, Ladner JT, Nasar F, Pitt L, Smith DR, Soloveva V, Sun MG, Zeng X, Bavari S. Countering Zika Virus: The USAMRIID Response. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1062:303-318. [PMID: 29845541 DOI: 10.1007/978-981-10-8727-1_21] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The United States Army Medical Research Institute of Infectious Diseases (USAMRIID) possesses an array of expertise in diverse capabilities for the characterization of emerging infectious diseases from the pathogen itself to human or animal infection models. The recent Zika virus (ZIKV) outbreak was a challenge and an opportunity to put these capabilities to work as a cohesive unit to quickly respond to a rapidly developing threat. Next-generation sequencing was used to characterize virus stocks and to understand the introduction and spread of ZIKV in the United States. High Content Imaging was used to establish a High Content Screening process to evaluate antiviral therapies. Functional genomics was used to identify critical host factors for ZIKV infection. An animal model using the temporal blockade of IFN-I in immunocompetent laboratory mice was investigated in conjunction with Positron Emission Tomography to study ZIKV. Correlative light and electron microscopy was used to examine ZIKV interaction with host cells in culture and infected animals. A quantitative mass spectrometry approach was used to examine the protein and metabolite type or concentration changes that occur during ZIKV infection in blood, cells, and tissues. Multiplex fluorescence in situ hybridization was used to confirm ZIKV replication in mouse and NHP tissues. The integrated rapid response approach developed at USAMRIID presented in this review was successfully applied and provides a new template pathway to follow if a new biological threat emerges. This streamlined approach will increase the likelihood that novel medical countermeasures could be rapidly developed, evaluated, and translated into the clinic.
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Affiliation(s)
- Robert G Lowen
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA.
| | - Thomas M Bocan
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Christopher D Kane
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Lisa H Cazares
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Krishna P Kota
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Jason T Ladner
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, USA
| | - Farooq Nasar
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Louise Pitt
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Darci R Smith
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Veronica Soloveva
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Mei G Sun
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Xiankun Zeng
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
| | - Sina Bavari
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, MD, USA
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11
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Richert-Pöggeler KR, Franzke K, Hipp K, Kleespies RG. Electron Microscopy Methods for Virus Diagnosis and High Resolution Analysis of Viruses. Front Microbiol 2018. [PMID: 30666247 DOI: 10.3389/fmicb.2018.03255.ecollection] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023] Open
Abstract
The term "virosphere" describes both the space where viruses are found and the space they influence, and can extend to their impact on the environment, highlighting the complexity of the interactions involved. Studying the biology of viruses and the etiology of virus disease is crucial to the prevention of viral disease, efficient and reliable virus diagnosis, and virus control. Electron microscopy (EM) is an essential tool in the detection and analysis of virus replication. New EM methods and ongoing technical improvements offer a broad spectrum of applications, allowing in-depth investigation of viral impact on not only the host but also the environment. Indeed, using the most up-to-date electron cryomicroscopy methods, such investigations are now close to atomic resolution. In combination with bioinformatics, the transition from 2D imaging to 3D remodeling allows structural and functional analyses that extend and augment our knowledge of the astonishing diversity in virus structure and lifestyle. In combination with confocal laser scanning microscopy, EM enables live imaging of cells and tissues with high-resolution analysis. Here, we describe the pivotal role played by EM in the study of viruses, from structural analysis to the biological relevance of the viral metagenome (virome).
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Affiliation(s)
- Katja R Richert-Pöggeler
- Federal Research Center for Cultivated Plants, Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute, Braunschweig, Germany
| | - Kati Franzke
- Institute of Infectiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Katharina Hipp
- Electron Microscopy Facility, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Regina G Kleespies
- Federal Research Centre for Cultivated Plants, Institute for Biological Control, Julius Kühn Institute, Darmstadt, Germany
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12
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Partially Uncleaved Alphavirus Replicase Forms Spherule Structures in the Presence and Absence of RNA Template. J Virol 2017; 91:JVI.00787-17. [PMID: 28701392 DOI: 10.1128/jvi.00787-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 06/30/2017] [Indexed: 12/14/2022] Open
Abstract
Alphaviruses are positive-strand RNA viruses expressing their replicase as a polyprotein, P1234, which is cleaved to four final products, nonstructural proteins nsP1 to nsP4. The replicase proteins together with viral RNA and host factors form membrane invaginations termed spherules, which act as the replication complexes producing progeny RNAs. We have previously shown that the wild-type alphavirus replicase requires a functional RNA template and active polymerase to generate spherule structures. However, we now find that specific partially processed forms of the replicase proteins alone can give rise to membrane invaginations in the absence of RNA or replication. The minimal requirement for spherule formation was the expression of properly cleaved nsP4, together with either uncleaved P123 or with the combination of nsP1 and uncleaved P23. These inactive spherules were morphologically less regular than replication-induced spherules. In the presence of template, nsP1 plus uncleaved P23 plus nsP4 could efficiently assemble active replication spherules producing both negative-sense and positive-sense RNA strands. P23 alone did not have membrane affinity, but could be recruited to membrane sites in the presence of nsP1 and nsP4. These results define the set of viral components required for alphavirus replication complex assembly and suggest the possibility that it could be reconstituted from separately expressed nonstructural proteins.IMPORTANCE All positive-strand RNA viruses extensively modify host cell membranes to serve as efficient platforms for viral RNA replication. Alphaviruses and several other groups induce protective membrane invaginations (spherules) as their genome factories. Most positive-strand viruses produce their replicase as a polyprotein precursor, which is further processed through precise and regulated cleavages. We show here that specific cleavage intermediates of the alphavirus replicase can give rise to spherule structures in the absence of viral RNA. In the presence of template RNA, the same intermediates yield active replication complexes. Thus, partially cleaved replicase proteins play key roles that connect replication complex assembly, membrane deformation, and the different stages of RNA synthesis.
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13
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Chikungunya virus infectivity, RNA replication and non-structural polyprotein processing depend on the nsP2 protease's active site cysteine residue. Sci Rep 2016; 6:37124. [PMID: 27845418 PMCID: PMC5109220 DOI: 10.1038/srep37124] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/24/2016] [Indexed: 11/23/2022] Open
Abstract
Chikungunya virus (CHIKV), genus Alphavirus, family Togaviridae, has a positive-stand RNA genome approximately 12 kb in length. In infected cells, the genome is translated into non-structural polyprotein P1234, an inactive precursor of the viral replicase, which is activated by cleavages carried out by the non-structural protease, nsP2. We have characterized CHIKV nsP2 using both cell-free and cell-based assays. First, we show that Cys478 residue in the active site of CHIKV nsP2 is indispensable for P1234 processing. Second, the substrate requirements of CHIKV nsP2 are quite similar to those of nsP2 of related Semliki Forest virus (SFV). Third, substitution of Ser482 residue, recently reported to contribute to the protease activity of nsP2, with Ala has almost no negative effect on the protease activity of CHIKV nsP2. Fourth, Cys478 to Ala as well as Trp479 to Ala mutations in nsP2 completely abolished RNA replication in CHIKV and SFV trans-replication systems. In contrast, trans-replicases with Ser482 to Ala mutation were similar to wild type counterparts. Fifth, Cys478 to Ala as well as Trp479 to Ala mutations in nsP2 abolished the rescue of infectious virus from CHIKV RNA transcripts while Ser482 to Ala mutation had no effect. Thus, CHIKV nsP2 is a cysteine protease.
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Onouchi T, Shiogama K, Mizutani Y, Takaki T, Tsutsumi Y. Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: III. Correlative Light and Electron Microscopic Study. Acta Histochem Cytochem 2016; 49:141-147. [PMID: 27917008 PMCID: PMC5130345 DOI: 10.1267/ahc.16028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 09/16/2016] [Indexed: 02/06/2023] Open
Abstract
Neutrophil extracellular traps (NETs) released from dead neutrophils at the site of inflammation represent webs of neutrophilic DNA stretches dotted with granule-derived antimicrobial proteins, including lactoferrin, and play important roles in innate immunity against microbial infection. We have shown the coexistence of NETs and fibrin meshwork in varied fibrinopurulent inflammatory lesions at both light and electron microscopic levels. In the present study, correlative light and electron microscopy (CLEM) employing confocal laser scanning microscopy and scanning electron microscopy was performed to bridge light and electron microscopic images of NETs and fibrin fibrils in formalin-fixed, paraffin-embedded, autopsied lung sections of legionnaire’s pneumonia. Lactoferrin immunoreactivity and 4'-6-diamidino-2-phenylindole (DAPI) reactivity were used as markers of NETs, and fibrin was probed by fibrinogen gamma chain. Of note is that NETs light microscopically represented as lactoferrin and DAPI-colocalized dots, 2.5 μm in diameter. CLEM gave super-resolution images of NETs and fibrin fibrils: “Dotted” NETs were ultrastructurally composed of fine filaments and masses of 58 nm-sized globular materials. A fibrin fibril consisted of clusters of smooth-surfaced filaments. NETs filaments (26 nm in diameter) were significantly thinner than fibrin filaments (295 nm in diameter). Of note is that CLEM was applicable to formalin-fixed, paraffin-embedded sections of autopsy material.
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Affiliation(s)
- Takanori Onouchi
- Department of Pathology, Fujita Health University School of Medicine
| | - Kazuya Shiogama
- Department of Pathology, Fujita Health University School of Medicine
| | | | - Takashi Takaki
- Techinical Support Center, JEOL Ltd
- Department of Pathology, Tohoku University Graduate School of Medicine
| | - Yutaka Tsutsumi
- Department of Pathology, Fujita Health University School of Medicine
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Bell-Sakyi L, Weisheit S, Rückert C, Barry G, Fazakerley J, Fragkoudis R. Microscopic Visualisation of Zoonotic Arbovirus Replication in Tick Cell and Organ Cultures Using Semliki Forest Virus Reporter Systems. Vet Sci 2016; 3:vetsci3040028. [PMID: 29056736 PMCID: PMC5606593 DOI: 10.3390/vetsci3040028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/09/2016] [Accepted: 09/22/2016] [Indexed: 11/25/2022] Open
Abstract
Ticks are vectors and reservoirs of many arboviruses pathogenic for humans or domestic animals; in addition, during bloodfeeding they can acquire and harbour pathogenic arboviruses normally transmitted by other arthropods such as mosquitoes. Tick cell and organ cultures provide convenient tools for propagation and study of arboviruses, both tick-borne and insect-borne, enabling elucidation of virus-tick cell interaction and yielding insight into the mechanisms behind vector competence and reservoir potential for different arbovirus species. The mosquito-borne zoonotic alphavirus Semliki Forest virus (SFV), which replicates well in tick cells, has been isolated from Rhipicephalus, Hyalomma, and Amblyomma spp. ticks removed from mammalian hosts in East Africa; however nothing is known about any possible role of ticks in SFV epidemiology. Here we present a light and electron microscopic study of SFV infecting cell lines and organ cultures derived from African Rhipicephalus spp. ticks. As well as demonstrating the applicability of these culture systems for studying virus-vector interactions, we provide preliminary evidence to support the hypothesis that SFV is not normally transmitted by ticks because the virus does not infect midgut cells.
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Affiliation(s)
- Lesley Bell-Sakyi
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - Sabine Weisheit
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - Claudia Rückert
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - Gerald Barry
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - John Fazakerley
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
| | - Rennos Fragkoudis
- The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK.
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16
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Hellström K, Kallio K, Meriläinen HM, Jokitalo E, Ahola T. Ability of minus strands and modified plus strands to act as templates in Semliki Forest virus RNA replication. J Gen Virol 2016; 97:1395-1407. [DOI: 10.1099/jgv.0.000448] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Kirsi Hellström
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Katri Kallio
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Hanna-Mari Meriläinen
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Tero Ahola
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
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17
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Bykov YS, Cortese M, Briggs JAG, Bartenschlager R. Correlative light and electron microscopy methods for the study of virus-cell interactions. FEBS Lett 2016; 590:1877-95. [PMID: 27008928 DOI: 10.1002/1873-3468.12153] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Revised: 03/09/2016] [Accepted: 03/22/2016] [Indexed: 12/21/2022]
Abstract
Electron microscopy (EM) is an invaluable tool to study the interactions of viruses with cells, and the ultrastructural changes induced in host cells by virus infection. Light microscopy (LM) is a complementary tool with the potential to locate rare events, label specific components, and obtain dynamic information. The combination of LM and EM in correlative light and electron microscopy (CLEM) is particularly powerful. It can be used to complement a static EM image with dynamic data from live imaging, identify the ultrastructure observed in LM, or, conversely, provide molecular specificity data for a known ultrastructure. Here, we describe methods and strategies for CLEM, discuss their advantages and limitations, and review applications of CLEM to study virus-host interactions.
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Affiliation(s)
- Yury S Bykov
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Mirko Cortese
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Germany
| | - John A G Briggs
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Germany
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18
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Yamauchi Y, Greber UF. Principles of Virus Uncoating: Cues and the Snooker Ball. Traffic 2016; 17:569-92. [PMID: 26875443 PMCID: PMC7169695 DOI: 10.1111/tra.12387] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 02/10/2016] [Accepted: 02/10/2016] [Indexed: 12/17/2022]
Abstract
Viruses are spherical or complex shaped carriers of proteins, nucleic acids and sometimes lipids and sugars. They are metastable and poised for structural changes. These features allow viruses to communicate with host cells during entry, and to release the viral genome, a process known as uncoating. Studies have shown that hundreds of host factors directly or indirectly support this process. The cell provides molecules that promote stepwise virus uncoating, and direct the virus to the site of replication. It acts akin to a snooker player who delivers accurate and timely shots (cues) to the ball (virus) to score. The viruses, on the other hand, trick (snooker) the host, hijack its homeostasis systems, and dampen innate immune responses directed against danger signals. In this review, we discuss how cellular cues, facilitators, and built‐in viral mechanisms promote uncoating. Cues come from receptors, enzymes and chemicals that act directly on the virus particle to alter its structure, trafficking and infectivity. Facilitators are defined as host factors that are involved in processes which indirectly enhance entry or uncoating. Unraveling the mechanisms of virus uncoating will continue to enhance understanding of cell functions, and help counteracting infections with chemicals and vaccines.
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Affiliation(s)
- Yohei Yamauchi
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Urs F Greber
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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Utt A, Quirin T, Saul S, Hellström K, Ahola T, Merits A. Versatile Trans-Replication Systems for Chikungunya Virus Allow Functional Analysis and Tagging of Every Replicase Protein. PLoS One 2016; 11:e0151616. [PMID: 26963103 PMCID: PMC4786200 DOI: 10.1371/journal.pone.0151616] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/01/2016] [Indexed: 02/06/2023] Open
Abstract
Chikungunya virus (CHIKV; genus Alphavirus, family Togaviridae) has recently caused several major outbreaks affecting millions of people. There are no licensed vaccines or antivirals, and the knowledge of the molecular biology of CHIKV, crucial for development of efficient antiviral strategies, remains fragmentary. CHIKV has a 12 kb positive-strand RNA genome, which is translated to yield a nonstructural (ns) or replicase polyprotein. CHIKV structural proteins are expressed from a subgenomic RNA synthesized in infected cells. Here we have developed CHIKV trans-replication systems, where replicase expression and RNA replication are uncoupled. Bacteriophage T7 RNA polymerase or cellular RNA polymerase II were used for production of mRNAs for CHIKV ns polyprotein and template RNAs, which are recognized by CHIKV replicase and encode for reporter proteins. CHIKV replicase efficiently amplified such RNA templates and synthesized large amounts of subgenomic RNA in several cell lines. This system was used to create tagged versions of ns proteins including nsP1 fused with enhanced green fluorescent protein and nsP4 with an immunological tag. Analysis of these constructs and a matching set of replicon vectors revealed that the replicases containing tagged ns proteins were functional and maintained their subcellular localizations. When cells were co-transfected with constructs expressing template RNA and wild type or tagged versions of CHIKV replicases, formation of characteristic replicase complexes (spherules) was observed. Analysis of mutations associated with noncytotoxic phenotype in CHIKV replicons showed that a low level of RNA replication is not a pre-requisite for reduced cytotoxicity. The CHIKV trans-replicase does not suffer from genetic instability and represents an efficient, sensitive and reliable tool for studies of different aspects of CHIKV RNA replication process.
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Affiliation(s)
- Age Utt
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Tania Quirin
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Sirle Saul
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Kirsi Hellström
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Tero Ahola
- Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, 50411, Estonia
- * E-mail:
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20
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Follain G, Mercier L, Osmani N, Harlepp S, Goetz JG. Seeing is believing: multi-scale spatio-temporal imaging towards in vivo cell biology. J Cell Sci 2016; 130:23-38. [DOI: 10.1242/jcs.189001] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
ABSTRACT
Life is driven by a set of biological events that are naturally dynamic and tightly orchestrated from the single molecule to entire organisms. Although biochemistry and molecular biology have been essential in deciphering signaling at a cellular and organismal level, biological imaging has been instrumental for unraveling life processes across multiple scales. Imaging methods have considerably improved over the past decades and now allow to grasp the inner workings of proteins, organelles, cells, organs and whole organisms. Not only do they allow us to visualize these events in their most-relevant context but also to accurately quantify underlying biomechanical features and, so, provide essential information for their understanding. In this Commentary, we review a palette of imaging (and biophysical) methods that are available to the scientific community for elucidating a wide array of biological events. We cover the most-recent developments in intravital imaging, light-sheet microscopy, super-resolution imaging, and correlative light and electron microscopy. In addition, we illustrate how these technologies have led to important insights in cell biology, from the molecular to the whole-organism resolution. Altogether, this review offers a snapshot of the current and state-of-the-art imaging methods that will contribute to the understanding of life and disease.
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Affiliation(s)
- Gautier Follain
- Microenvironmental Niche in Tumorigenesis and Targeted Therapy, Inserm U1109, MN3T, Strasbourg F-67200, France
- Université de Strasbourg, Strasbourg F-67000, France
- LabEx Medalis, Université de Strasbourg, Strasbourg, F-67000, France
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg F-67000, France
| | - Luc Mercier
- Microenvironmental Niche in Tumorigenesis and Targeted Therapy, Inserm U1109, MN3T, Strasbourg F-67200, France
- Université de Strasbourg, Strasbourg F-67000, France
- LabEx Medalis, Université de Strasbourg, Strasbourg, F-67000, France
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg F-67000, France
| | - Naël Osmani
- Microenvironmental Niche in Tumorigenesis and Targeted Therapy, Inserm U1109, MN3T, Strasbourg F-67200, France
- Université de Strasbourg, Strasbourg F-67000, France
- LabEx Medalis, Université de Strasbourg, Strasbourg, F-67000, France
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg F-67000, France
| | - Sébastien Harlepp
- Université de Strasbourg, Strasbourg F-67000, France
- DON: Optique ultrarapide et nanophotonique, IPCMS UMR7504, Strasbourg 67000, France
- LabEx NIE, Université de Strasbourg, Strasbourg F-67000, France
| | - Jacky G. Goetz
- Microenvironmental Niche in Tumorigenesis and Targeted Therapy, Inserm U1109, MN3T, Strasbourg F-67200, France
- Université de Strasbourg, Strasbourg F-67000, France
- LabEx Medalis, Université de Strasbourg, Strasbourg, F-67000, France
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), Strasbourg F-67000, France
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21
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Mossman K. Methods related to molecular virology. Methods 2015; 90:1-2. [PMID: 26589248 DOI: 10.1016/j.ymeth.2015.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Karen Mossman
- Department of Biochemistry and Biomedical Sciences, McMaster Immunology Research Center, Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada; Department of Pathology and Molecular Medicine, McMaster Immunology Research Center, Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
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