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Solforosi L, Kuipers H, Jongeneelen M, Rosendahl Huber SK, van der Lubbe JE, Dekking L, Czapska-Casey DN, Izquierdo Gil A, Baert MR, Drijver J, Vaneman J, van Huizen E, Choi Y, Vreugdenhil J, Kroos S, de Wilde AH, Kourkouta E, Custers J, van der Vlugt R, Veldman D, Huizingh J, Kaszas K, Dalebout TJ, Myeni SK, Kikkert M, Snijder EJ, Barouch DH, Böszörményi KP, Stammes MA, Kondova I, Verschoor EJ, Verstrepen BE, Koopman G, Mooij P, Bogers WM, van Heerden M, Muchene L, Tolboom JT, Roozendaal R, Brandenburg B, Schuitemaker H, Wegmann F, Zahn RC. Immunogenicity and efficacy of one and two doses of Ad26.COV2.S COVID vaccine in adult and aged NHP. J Exp Med 2021; 218:e20202756. [PMID: 33909009 PMCID: PMC8085771 DOI: 10.1084/jem.20202756] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/25/2021] [Accepted: 04/08/2021] [Indexed: 12/22/2022] Open
Abstract
Safe and effective coronavirus disease-19 (COVID-19) vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one- and two-dose regimens of the Ad26.COV2.S vaccine candidate in adult and aged nonhuman primates (NHPs). A two-dose Ad26.COV2.S regimen induced higher peak binding and neutralizing antibody responses compared with a single dose. In one-dose regimens, neutralizing antibody responses were stable for at least 14 wk, providing an early indication of durability. Ad26.COV2.S induced humoral immunity and T helper cell (Th cell) 1-skewed cellular responses in aged NHPs that were comparable to those in adult animals. Aged Ad26.COV2.S-vaccinated animals challenged 3 mo after dose 1 with a SARS-CoV-2 spike G614 variant showed near complete lower and substantial upper respiratory tract protection for both regimens. Neutralization of variants of concern by NHP sera was reduced for B.1.351 lineages while maintained for the B.1.1.7 lineage independent of Ad26.COV2.S vaccine regimen.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Joke Drijver
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | - Joost Vaneman
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | - Ying Choi
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | - Sanne Kroos
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | | | - Jerome Custers
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | - Daniel Veldman
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | | | - Tim J. Dalebout
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Sebenzile K. Myeni
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Marjolein Kikkert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Dan H. Barouch
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | | | | | | | | | | | - Gerrit Koopman
- Biomedical Primate Research Centre, Rijswijk, Netherlands
| | - Petra Mooij
- Biomedical Primate Research Centre, Rijswijk, Netherlands
| | | | - Marjolein van Heerden
- Non-Clinical Safety Toxicology/Pathology, Janssen Research and Development, Beerse, Belgium
| | - Leacky Muchene
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | | | | | | | | | - Frank Wegmann
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | - Roland C. Zahn
- Janssen Vaccines and Prevention B.V., Leiden, Netherlands
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Bos R, Rutten L, van der Lubbe JEM, Bakkers MJG, Hardenberg G, Wegmann F, Zuijdgeest D, de Wilde AH, Koornneef A, Verwilligen A, van Manen D, Kwaks T, Vogels R, Dalebout TJ, Myeni SK, Kikkert M, Snijder EJ, Li Z, Barouch DH, Vellinga J, Langedijk JPM, Zahn RC, Custers J, Schuitemaker H. Ad26 vector-based COVID-19 vaccine encoding a prefusion-stabilized SARS-CoV-2 Spike immunogen induces potent humoral and cellular immune responses. NPJ Vaccines 2020; 5:91. [PMID: 33083026 PMCID: PMC7522255 DOI: 10.1038/s41541-020-00243-x] [Citation(s) in RCA: 235] [Impact Index Per Article: 58.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/10/2020] [Indexed: 11/16/2022] Open
Abstract
Development of effective preventative interventions against SARS-CoV-2, the etiologic agent of COVID-19 is urgently needed. The viral surface spike (S) protein of SARS-CoV-2 is a key target for prophylactic measures as it is critical for the viral replication cycle and the primary target of neutralizing antibodies. We evaluated design elements previously shown for other coronavirus S protein-based vaccines to be successful, e.g., prefusion-stabilizing substitutions and heterologous signal peptides, for selection of a S-based SARS-CoV-2 vaccine candidate. In vitro characterization demonstrated that the introduction of stabilizing substitutions (i.e., furin cleavage site mutations and two consecutive prolines in the hinge region of S2) increased the ratio of neutralizing versus non-neutralizing antibody binding, suggestive for a prefusion conformation of the S protein. Furthermore, the wild-type signal peptide was best suited for the correct cleavage needed for a natively folded protein. These observations translated into superior immunogenicity in mice where the Ad26 vector encoding for a membrane-bound stabilized S protein with a wild-type signal peptide elicited potent neutralizing humoral immunity and cellular immunity that was polarized towards Th1 IFN-γ. This optimized Ad26 vector-based vaccine for SARS-CoV-2, termed Ad26.COV2.S, is currently being evaluated in a phase I clinical trial (ClinicalTrials.gov Identifier: NCT04436276).
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Affiliation(s)
- Rinke Bos
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | - Lucy Rutten
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | | | | | | | - Frank Wegmann
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | | | | | | | | | | | - Ted Kwaks
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | - Ronald Vogels
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | - Tim J Dalebout
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Sebenzile K Myeni
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marjolein Kikkert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Zhenfeng Li
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215 USA
| | - Dan H Barouch
- Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215 USA
| | - Jort Vellinga
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | | | - Roland C Zahn
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
| | - Jerome Custers
- Janssen Vaccines & Prevention BV, Leiden, The Netherlands
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3
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Snijder EJ, Limpens RWAL, de Wilde AH, de Jong AWM, Zevenhoven-Dobbe JC, Maier HJ, Faas FFGA, Koster AJ, Bárcena M. A unifying structural and functional model of the coronavirus replication organelle: Tracking down RNA synthesis. PLoS Biol 2020; 18:e3000715. [PMID: 32511245 PMCID: PMC7302735 DOI: 10.1371/journal.pbio.3000715] [Citation(s) in RCA: 298] [Impact Index Per Article: 74.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/18/2020] [Accepted: 05/14/2020] [Indexed: 12/12/2022] Open
Abstract
Zoonotic coronavirus (CoV) infections, such as those responsible for the current severe acute respiratory syndrome-CoV 2 (SARS-CoV-2) pandemic, cause grave international public health concern. In infected cells, the CoV RNA-synthesizing machinery associates with modified endoplasmic reticulum membranes that are transformed into the viral replication organelle (RO). Although double-membrane vesicles (DMVs) appear to be a pan-CoV RO element, studies to date describe an assortment of additional CoV-induced membrane structures. Despite much speculation, it remains unclear which RO element(s) accommodate viral RNA synthesis. Here we provide detailed 2D and 3D analyses of CoV ROs and show that diverse CoVs essentially induce the same membrane modifications, including the small open double-membrane spherules (DMSs) previously thought to be restricted to gamma- and delta-CoV infections and proposed as sites of replication. Metabolic labeling of newly synthesized viral RNA followed by quantitative electron microscopy (EM) autoradiography revealed abundant viral RNA synthesis associated with DMVs in cells infected with the beta-CoVs Middle East respiratory syndrome-CoV (MERS-CoV) and SARS-CoV and the gamma-CoV infectious bronchitis virus. RNA synthesis could not be linked to DMSs or any other cellular or virus-induced structure. Our results provide a unifying model of the CoV RO and clearly establish DMVs as the central hub for viral RNA synthesis and a potential drug target in CoV infection.
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Affiliation(s)
- Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Ronald W. A. L. Limpens
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Adriaan H. de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Anja W. M. de Jong
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Jessika C. Zevenhoven-Dobbe
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Frank F. G. A. Faas
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Abraham J. Koster
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Montserrat Bárcena
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
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de Wilde AH, Pham U, Posthuma CC, Snijder EJ. Cyclophilins and cyclophilin inhibitors in nidovirus replication. Virology 2018; 522:46-55. [PMID: 30014857 PMCID: PMC7112023 DOI: 10.1016/j.virol.2018.06.011] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/13/2018] [Accepted: 06/18/2018] [Indexed: 12/12/2022]
Abstract
Cyclophilins (Cyps) belong to the family of peptidyl-prolyl isomerases (PPIases). The PPIase activity of most Cyps is inhibited by the immunosuppressive drug cyclosporin A and several of its non-immunosuppressive analogs, which can also block the replication of nidoviruses (arteriviruses and coronaviruses). Cyclophilins have been reported to play an essential role in the replication of several other RNA viruses, including human immunodeficiency virus-1, hepatitis C virus, and influenza A virus. Likewise, the replication of various nidoviruses was reported to depend on Cyps or other PPIases. This review summarizes our current understanding of this class of nidovirus-host interactions, including the potential function of in particular CypA and the inhibitory effect of Cyp inhibitors. Also the involvement of the FK-506-binding proteins and parvulins is discussed. The nidovirus data are placed in a broader perspective by summarizing the most relevant data on Cyp interactions and Cyp inhibitors for other RNA viruses. Nidovirus replication is inhibited by cyclophilin inhibitors. Arterivirus replication depends on cyclophilin A. Cyclosporin A blocks arterivirus RNA synthesis. Using cyclophilin inhibitors against nidoviruses in vivo needs more investigation.
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Affiliation(s)
- Adriaan H de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Uyen Pham
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Clara C Posthuma
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
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de Wilde AH, Falzarano D, Zevenhoven-Dobbe JC, Beugeling C, Fett C, Martellaro C, Posthuma CC, Feldmann H, Perlman S, Snijder EJ. Alisporivir inhibits MERS- and SARS-coronavirus replication in cell culture, but not SARS-coronavirus infection in a mouse model. Virus Res 2016; 228:7-13. [PMID: 27840112 PMCID: PMC7114565 DOI: 10.1016/j.virusres.2016.11.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 01/20/2023]
Abstract
In cell culture models, low-micromolar doses of alisporivir block SARS-CoV and MERS-CoV replication. Combination treatment with alisporivir and ribavirin increases the anti-MERS-CoV activity in cell culture. Combination treatment with alisporivir and ribavirin does not protect against SARS-CoV infection in a mouse model. Cyclophilin-binding drugs should be explored further in the context of host-directed anti-coronaviral strategies.
Currently, there is no registered treatment for infections with emerging zoonotic coronaviruses like SARS- and MERS-coronavirus. We here report that in cultured cells low-micromolar concentrations of alisporivir, a non-immunosuppressive cyclosporin A-analog, inhibit the replication of four different coronaviruses, including MERS- and SARS-coronavirus. Ribavirin was found to further potentiate the antiviral effect of alisporivir in these cell culture-based infection models, but this combination treatment was unable to improve the outcome of SARS-CoV infection in a mouse model. Nevertheless, our data provide a basis to further explore the potential of Cyp inhibitors as host-directed, broad-spectrum inhibitors of coronavirus replication.
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Affiliation(s)
- Adriaan H de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
| | - Darryl Falzarano
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, USA
| | - Jessika C Zevenhoven-Dobbe
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Corrine Beugeling
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Craig Fett
- Department of Microbiology, University of Iowa, Iowa City, USA
| | - Cynthia Martellaro
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, USA
| | - Clara C Posthuma
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Heinz Feldmann
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, USA
| | - Stanley Perlman
- Department of Microbiology, University of Iowa, Iowa City, USA
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
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6
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de Wilde AH, Raj VS, Oudshoorn D, Bestebroer TM, van Nieuwkoop S, Limpens RWAL, Posthuma CC, van der Meer Y, Bárcena M, Haagmans BL, Snijder EJ, van den Hoogen BG. MERS-coronavirus replication induces severe in vitro cytopathology and is strongly inhibited by cyclosporin A or interferon-α treatment. J Gen Virol 2013; 94:1749-1760. [PMID: 23620378 PMCID: PMC3749523 DOI: 10.1099/vir.0.052910-0] [Citation(s) in RCA: 274] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Coronavirus (CoV) infections are commonly associated with respiratory and enteric disease in humans and animals. The 2003 outbreak of severe acute respiratory syndrome (SARS) highlighted the potentially lethal consequences of CoV-induced disease in humans. In 2012, a novel CoV (Middle East Respiratory Syndrome coronavirus; MERS-CoV) emerged, causing 49 human cases thus far, of which 23 had a fatal outcome. In this study, we characterized MERS-CoV replication and cytotoxicity in human and monkey cell lines. Electron microscopy of infected Vero cells revealed extensive membrane rearrangements, including the formation of double-membrane vesicles and convoluted membranes, which have been implicated previously in the RNA synthesis of SARS-CoV and other CoVs. Following infection, we observed rapidly increasing viral RNA synthesis and release of high titres of infectious progeny, followed by a pronounced cytopathology. These characteristics were used to develop an assay for antiviral compound screening in 96-well format, which was used to identify cyclosporin A as an inhibitor of MERS-CoV replication in cell culture. Furthermore, MERS-CoV was found to be 50–100 times more sensitive to alpha interferon (IFN-α) treatment than SARS-CoV, an observation that may have important implications for the treatment of MERS-CoV-infected patients. MERS-CoV infection did not prevent the IFN-induced nuclear translocation of phosphorylated STAT1, in contrast to infection with SARS-CoV where this block inhibits the expression of antiviral genes. These findings highlight relevant differences between these distantly related zoonotic CoVs in terms of their interaction with and evasion of the cellular innate immune response.
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Affiliation(s)
- Adriaan H de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - V Stalin Raj
- Viroscience Lab, Erasmus MC, Rotterdam, The Netherlands
| | - Diede Oudshoorn
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | | | | | - Ronald W A L Limpens
- Section Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Clara C Posthuma
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Yvonne van der Meer
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Montserrat Bárcena
- Section Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
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de Wilde AH, Zevenhoven-Dobbe JC, van der Meer Y, Thiel V, Narayanan K, Makino S, Snijder EJ, van Hemert MJ. Cyclosporin A inhibits the replication of diverse coronaviruses. J Gen Virol 2011; 92:2542-2548. [PMID: 21752960 DOI: 10.1099/vir.0.034983-0] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Low micromolar, non-cytotoxic concentrations of cyclosporin A (CsA) strongly affected the replication of severe acute respiratory syndrome coronavirus (SARS-CoV), human coronavirus 229E and mouse hepatitis virus in cell culture, as was evident from the strong inhibition of GFP reporter gene expression and a reduction of up to 4 logs in progeny titres. Upon high-multiplicity infection, CsA treatment rendered SARS-CoV RNA and protein synthesis almost undetectable, suggesting an early block in replication. siRNA-mediated knockdown of the expression of the prominent CsA targets cyclophilin A and B did not affect SARS-CoV replication, suggesting either that these specific cyclophilin family members are dispensable or that the reduced expression levels suffice to support replication.
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Affiliation(s)
- Adriaan H de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Jessika C Zevenhoven-Dobbe
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Yvonne van der Meer
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Volker Thiel
- Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.,Institute of Immunobiology, Kantonal Hospital St Gallen, St Gallen, Switzerland
| | - Krishna Narayanan
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Shinji Makino
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Martijn J van Hemert
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
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van Hemert MJ, de Wilde AH, Gorbalenya AE, Snijder EJ. The in vitro RNA synthesizing activity of the isolated arterivirus replication/transcription complex is dependent on a host factor. J Biol Chem 2008; 283:16525-36. [PMID: 18411274 DOI: 10.1074/jbc.m708136200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytoplasmic replication of positive-stranded RNA viruses is associated with characteristic, virus-induced membrane structures that are derived from host cell organelles. We used the prototype arterivirus, equine arteritis virus (EAV), to gain insight into the structure and function of the replication/transcription complex (RTC) of nidoviruses. RTCs were isolated from EAV-infected cells, and their activity was studied using a newly developed in vitro assay for viral RNA synthesis, which reproduced the synthesis of both viral genome and subgenomic mRNAs. A detailed characterization of this system and its reaction products is described. RTCs isolated from cytoplasmic extracts by differential centrifugation were inactive unless supplemented with a cytosolic host protein factor, which, according to subsequent size fractionation analysis, has a molecular mass in the range of 59-70 kDa. This host factor was found to be present in a wide variety of eukaryotes. Several EAV replicase subunits cosedimented with newly made viral RNA in a heavy membrane fraction that contained all RNA-dependent RNA polymerase activity. This fraction contained the characteristic double membrane vesicles (DMVs) that were previously implicated in EAV RNA synthesis and could be immunolabeled for EAV nonstructural proteins (nsps). Replicase subunits directly involved in viral RNA synthesis (nsp9 and nsp10) or DMV formation (nsp2 and nsp3) exclusively cosedimented with the active RTC. Subgenomic mRNAs appeared to be released from the complex, whereas newly made genomic RNA remained more tightly associated. Taken together, our data strongly support a link between DMVs and the RNA-synthesizing machinery of arteriviruses.
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Affiliation(s)
- Martijn J van Hemert
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC E4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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