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Comes JDG, Doets K, Zegers T, Kessler M, Slits I, Ballesteros NA, van de Weem NMP, Pouwels H, van Oers MM, van Hulten MCW, Langereis M, Pijlman GP. Evaluation of bird-adapted self-amplifying mRNA vaccine formulations in chickens. Vaccine 2024; 42:2895-2908. [PMID: 38521674 DOI: 10.1016/j.vaccine.2024.03.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 03/11/2024] [Accepted: 03/13/2024] [Indexed: 03/25/2024]
Abstract
Each year, millions of poultry succumb to highly pathogenic avian influenza A virus (AIV) and infectious bursal disease virus (IBDV) infections. Conventional vaccines based on inactivated or live-attenuated viruses are useful tools for disease prevention and control, yet, they often fall short in terms of safety, efficacy, and development times. Therefore, versatile vaccine platforms are crucial to protect poultry from emerging viral pathogens. Self-amplifying (replicon) RNA vaccines offer a well-defined and scalable option for the protection of both animals and humans. The best-studied replicon platform, based on the Venezuelan equine encephalitis virus (VEEV; family Togaviridae) TC-83 vaccine strain, however, displays limited efficacy in poultry, warranting the exploration of alternative, avian-adapted, replicon platforms. In this study, we engineered two Tembusu virus (TMUV; family Flaviviridae) replicons encoding varying capsid gene lengths and compared these to the benchmark VEEV replicon in vitro. The TMUV replicon system exhibited a robust and prolonged transgene expression compared to the VEEV replicon system in both avian and mammalian cells. Moreover, the TMUV replicon induced a lesser cytopathic effect compared to the VEEV replicon RNA in vitro. DNA-launched versions of the TMUV and VEEV replicons (DREP) were also developed. The replicons successfully expressed the AIV haemagglutinin (HA) glycoproteins and the IBDV capsid protein (pVP2). To assess the immune responses elicited by the TMUV replicon system in chickens, a prime-boost vaccination trial was conducted using lipid nanoparticle (LNP)-formulated replicon RNA and DREP encoding the viral (glyco)proteins of AIV or IBDV. Both TMUV and VEEV replicon RNAs were unable to induce a humoral response against AIV. However, TMUV replicon RNA induced IBDV-specific seroconversion in vaccinated chickens, in contrast to VEEV replicon RNA, which showed no significant humoral response. In both AIV and IBDV immunization studies, VEEV DREP generated the highest (neutralizing) antibody responses, which underscores the potential for self-amplifying mRNA vaccine technology to combat emerging poultry diseases.
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Affiliation(s)
- Jerome D G Comes
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands
| | - Kristel Doets
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands; MSD Animal Health, Wim de Körverstraat 35, Boxmeer 5831AN, the Netherlands
| | - Thijmen Zegers
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands
| | - Merel Kessler
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands
| | - Irene Slits
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands
| | | | | | - Henk Pouwels
- MSD Animal Health, Wim de Körverstraat 35, Boxmeer 5831AN, the Netherlands
| | - Monique M van Oers
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands
| | | | - Martijn Langereis
- MSD Animal Health, Wim de Körverstraat 35, Boxmeer 5831AN, the Netherlands
| | - Gorben P Pijlman
- Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, Wageningen 6708PB, the Netherlands.
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2
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Ramanathan HN, Zhang S, Douam F, Mar KB, Chang J, Yang PL, Schoggins JW, Ploss A, Lindenbach BD. A Sensitive Yellow Fever Virus Entry Reporter Identifies Valosin-Containing Protein (VCP/p97) as an Essential Host Factor for Flavivirus Uncoating. mBio 2020; 11:e00467-20. [PMID: 32291299 PMCID: PMC7157815 DOI: 10.1128/mbio.00467-20] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 03/16/2020] [Indexed: 01/17/2023] Open
Abstract
While the basic mechanisms of flavivirus entry and fusion are understood, little is known about the postfusion events that precede RNA replication, such as nucleocapsid disassembly. We describe here a sensitive, conditionally replication-defective yellow fever virus (YFV) entry reporter, YFVΔSK/Nluc, to quantitively monitor the translation of incoming, virus particle-delivered genomes. We validated that YFVΔSK/Nluc gene expression can be neutralized by YFV-specific antisera and requires known flavivirus entry pathways and cellular factors, including clathrin- and dynamin-mediated endocytosis, endosomal acidification, YFV E glycoprotein-mediated fusion, and cellular LY6E and RPLP1 expression. The initial round of YFV translation was shown to require cellular ubiquitylation, consistent with recent findings that dengue virus capsid protein must be ubiquitylated in order for nucleocapsid uncoating to occur. Importantly, translation of incoming YFV genomes also required valosin-containing protein (VCP)/p97, a cellular ATPase that unfolds and extracts ubiquitylated client proteins from large complexes. RNA transfection and washout experiments showed that VCP/p97 functions at a postfusion, pretranslation step in YFV entry. Finally, VCP/p97 activity was required by other flaviviruses in mammalian cells and by YFV in mosquito cells. Together, these data support a critical role for VCP/p97 in the disassembly of incoming flavivirus nucleocapsids during a postfusion step in virus entry.IMPORTANCE Flaviviruses are an important group of RNA viruses that cause significant human disease. The mechanisms by which flavivirus nucleocapsids are disassembled during virus entry remain unclear. Here, we used a yellow fever virus entry reporter, which expresses a sensitive reporter enzyme but does not replicate, to show that nucleocapsid disassembly requires the cellular protein-disaggregating enzyme valosin-containing protein, also known as p97.
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Affiliation(s)
- Harish N Ramanathan
- Department of Microbial Pathogenesis, Yale University, New Haven, Connecticut, USA
| | - Shuo Zhang
- Department of Microbial Pathogenesis, Yale University, New Haven, Connecticut, USA
| | - Florian Douam
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Katrina B Mar
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jinhong Chang
- Department of Experimental Therapeutics, The Baruch S. Blumberg Institute, Doylestown, Pennsylvania, USA
| | - Priscilla L Yang
- Department of Microbiology and the Blavatnik Institute, Harvard Medical School, Boston, Massachusetts, USA
| | - John W Schoggins
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Alexander Ploss
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Brett D Lindenbach
- Department of Microbial Pathogenesis, Yale University, New Haven, Connecticut, USA
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3
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Zou J, Shi PY. Strategies for Zika drug discovery. Curr Opin Virol 2019; 35:19-26. [PMID: 30852345 DOI: 10.1016/j.coviro.2019.01.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Revised: 01/23/2019] [Accepted: 01/28/2019] [Indexed: 12/15/2022]
Abstract
Zika virus (ZIKV) can cause devastating congenital syndrome in fetuses from pregnant women and autoimmune disorder Guillain-Barré syndrome in adults. No clinically approved vaccine or drug is currently available for ZIKV. This unmet medical need has motivated a global effort to develop countermeasures. Several promising ZIKV vaccine candidates have already entered clinical trials. In contrast, antiviral development of ZIKV is lagging behind. Here, we review the overall strategies for ZIKV drug discovery, including (i) repurposing of clinically approved drugs, (ii) viral replication-based phenotypic screening for inhibitors, and (iii) targeted drug discovery of viral proteins. Along with vaccines, the development of antiviral treatment will provide a complementary means to control ZIKV infections.
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Affiliation(s)
- Jing Zou
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Pei-Yong Shi
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA; Department of Phamarcology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA; Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA; Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX, USA.
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4
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Kim YG, Baltabekova AZ, Zhiyenbay EE, Aksambayeva AS, Shagyrova ZS, Khannanov R, Ramanculov EM, Shustov AV. Recombinant Vaccinia virus-coded interferon inhibitor B18R: Expression, refolding and a use in a mammalian expression system with a RNA-vector. PLoS One 2017; 12:e0189308. [PMID: 29216299 PMCID: PMC5720773 DOI: 10.1371/journal.pone.0189308] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 11/22/2017] [Indexed: 12/24/2022] Open
Abstract
B18R protein of Vaccinia virus binds to type I interferons and inhibits activation of interferon-mediated signal transduction. Cells which have unimpaired interferon signaling such as primary cell cultures or some industrially important cell lines are capable of development of an antiviral state. An establishment of the antiviral state limits replication of RNA-viruses and can suppress replication of RNA vectors. The interferon inhibitor B18R effectively prevents the establishment of the antiviral state. For this reason, B18R has become a ubiquitous component of protocols for epigenetic reprogramming which use transfections of RNA replicons or mRNA. Despite wide practical applicability, commercially available B18R is predominantly produced in cell cultures and little information has been published on a production and use of bacterially expressed B18R. Objectives of this study were to produce B18R in an E.coli expression system and to confirm the product’s biological activity by using it to maintain RNA-vectors in cell cultures capable of the antiviral state. The described method allows the expression and efficient refolding to obtain 10–100 mg of B18R from a small-scale culture and the production process is economically attractive compared to a use of an eukaryotic expression. To check for a presence of the biological activity of bacterially-expressed B18R the protein was used to support persistence of an autonomously replicating RNA-vector in a cell culture which is capable of the antiviral state. A RNA-containing virus, Venezuelan equine encephalitis virus (VEE) can serve as an efficient vector for heterologous expression in cell cultures, although its replication is sensitive to the effects of type I interferons which limit a range of cell lines for a use with this vector. The VEE replicon was utilized to direct an expression of recombinant human granulocyte colony stimulating factor (G-CSF). The producing replicon could persist in HEK293 cells for sufficiently long time only in presence of B18R, whereas addition of B18R not only allowed persistence of the replicon but also increased production from the replicon. A model product granulocyte colony stimulating factor accumulated to 35.5 μg/ml during a 7 day experiment. This work describes efficacious expression and refolding of the viral cytokine inhibitor and demonstrates a utility of bacterially-expressed B18R.
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Affiliation(s)
- Yuriy G. Kim
- National Laboratory Astana, Nazarbayev University, Astana, Kazakhstan
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5
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Usme-Ciro JA, Lopera JA, Alvarez DA, Enjuanes L, Almazán F. Generation of a DNA-Launched Reporter Replicon Based on Dengue Virus Type 2 as a Multipurpose Platform. Intervirology 2017. [DOI: 10.1159/000476066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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6
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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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7
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Schott JW, Morgan M, Galla M, Schambach A. Viral and Synthetic RNA Vector Technologies and Applications. Mol Ther 2016; 24:1513-27. [PMID: 27377044 DOI: 10.1038/mt.2016.143] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 06/30/2016] [Indexed: 12/21/2022] Open
Abstract
Use of RNA is an increasingly popular method to transiently deliver genetic information for cell manipulation in basic research and clinical therapy. In these settings, viral and nonviral RNA platforms are employed for delivery of small interfering RNA and protein-coding mRNA. Technological advances allowing RNA modification for increased stability, improved translation and reduced immunogenicity have led to increased use of nonviral synthetic RNA, which is delivered in naked form or upon formulation. Alternatively, highly efficient viral entry pathways are exploited to transfer genes of interest as RNA incorporated into viral particles. Current viral RNA transfer technologies are derived from Retroviruses, nonsegmented negative-strand RNA viruses or positive-stranded Alpha- and Flaviviruses. In retroviral particles, the genes of interest can either be incorporated directly into the viral RNA genome or as nonviral RNA. Nonsegmented negative-strand virus-, Alpha- and Flavivirus-derived vectors support prolonged expression windows through replication of viral RNA encoding genes of interest. Mixed technologies combining viral and nonviral components are also available. RNA transfer is ideal for all settings that do not require permanent transgene expression and excludes potentially detrimental DNA integration into the target cell genome. Thus, RNA-based technologies are successfully applied for reprogramming, transdifferentiation, gene editing, vaccination, tumor therapy, and gene therapy.
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Affiliation(s)
- Juliane W Schott
- Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence REBIRTH, Hannover Medical School, Hannover, Germany
| | - Michael Morgan
- Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence REBIRTH, Hannover Medical School, Hannover, Germany
| | - Melanie Galla
- Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence REBIRTH, Hannover Medical School, Hannover, Germany
| | - Axel Schambach
- Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence REBIRTH, Hannover Medical School, Hannover, Germany.,Division of Hematology/Oncology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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8
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Miorin L, Maiuri P, Marcello A. Visual detection of Flavivirus RNA in living cells. Methods 2016; 98:82-90. [PMID: 26542763 PMCID: PMC7129942 DOI: 10.1016/j.ymeth.2015.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/29/2015] [Accepted: 11/01/2015] [Indexed: 12/24/2022] Open
Abstract
Flaviviruses include a wide range of important human pathogens delivered by insects or ticks. These viruses have a positive-stranded RNA genome that is replicated in the cytoplasm of the infected cell. The viral RNA genome is the template for transcription by the virally encoded RNA polymerase and for translation of the viral proteins. Furthermore, the double-stranded RNA intermediates of viral replication are believed to trigger the innate immune response through interaction with cytoplasmic cellular sensors. Therefore, understanding the subcellular distribution and dynamics of Flavivirus RNAs is of paramount importance to understand the interaction of the virus with its cellular host, which could be of insect, tick or mammalian, including human, origin. Recent advances on the visualization of Flavivirus RNA in living cells together with the development of methods to measure the dynamic properties of viral RNA are reviewed and discussed in this essay. In particular the application of bleaching techniques such as fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) are analysed in the context of tick-borne encephalitis virus replication. Conclusions driven by this approached are discussed in the wider context Flavivirus infection.
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MESH Headings
- Animals
- Cell Line
- Cricetinae
- Encephalitis Viruses, Tick-Borne/genetics
- Encephalitis Viruses, Tick-Borne/metabolism
- Encephalitis Viruses, Tick-Borne/ultrastructure
- Fluorescence Recovery After Photobleaching
- Fluorescent Dyes/chemistry
- Gene Expression Regulation, Viral
- Host-Pathogen Interactions
- Humans
- Molecular Imaging/methods
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Staining and Labeling/methods
- Ticks/virology
- Transcription, Genetic
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Affiliation(s)
- Lisa Miorin
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Paolo Maiuri
- IFOM - Istituto FIRC di Oncologia Molecolare, via Adamello 16, 20139 Milan, Italy
| | - Alessandro Marcello
- Laboratory of Molecular Virology, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34149 Trieste, Italy.
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10
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Rodríguez-Gascón A, del Pozo-Rodríguez A, Solinís MÁ. Development of nucleic acid vaccines: use of self-amplifying RNA in lipid nanoparticles. Int J Nanomedicine 2014; 9:1833-43. [PMID: 24748793 PMCID: PMC3986288 DOI: 10.2147/ijn.s39810] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Self-amplifying RNA or RNA replicon is a form of nucleic acid-based vaccine derived from either positive-strand or negative-strand RNA viruses. The gene sequences encoding structural proteins in these RNA viruses are replaced by mRNA encoding antigens of interest as well as by RNA polymerase for replication and transcription. This kind of vaccine has been successfully assayed with many different antigens as vaccines candidates, and has been shown to be potent in several animal species, including mice, nonhuman primates, and humans. A key challenge to realizing the broad potential of self-amplifying vaccines is the need for safe and effective delivery methods. Ideally, an RNA nanocarrier should provide protection from blood nucleases and extended blood circulation, which ultimately would increase the possibility of reaching the target tissue. The delivery system must then be internalized by the target cell and, upon receptor-mediated endocytosis, must be able to escape from the endosomal compartment into the cell cytoplasm, where the RNA machinery is located, while avoiding degradation by lysosomal enzymes. Further, delivery systems for systemic administration ought to be well tolerated upon administration. They should be safe, enabling the multiadministration treatment modalities required for improved clinical outcomes and, from a developmental point of view, production of large batches with reproducible specifications is also desirable. In this review, the concept of self-amplifying RNA vaccines and the most promising lipid-based delivery systems are discussed.
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Affiliation(s)
- Alicia Rodríguez-Gascón
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de Investigación Lascaray Ikergunea, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Ana del Pozo-Rodríguez
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de Investigación Lascaray Ikergunea, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - María Ángeles Solinís
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de Investigación Lascaray Ikergunea, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
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11
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Ulmer JB, Mason PW, Geall A, Mandl CW. RNA-based vaccines. Vaccine 2012; 30:4414-8. [DOI: 10.1016/j.vaccine.2012.04.060] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 04/10/2012] [Accepted: 04/18/2012] [Indexed: 02/07/2023]
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12
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Schrauf S, Kurz M, Taucher C, Mandl CW, Skern T. Generation and genetic stability of tick-borne encephalitis virus mutants dependent on processing by the foot-and-mouth disease virus 3C protease. J Gen Virol 2012; 93:504-515. [PMID: 22131310 PMCID: PMC3918513 DOI: 10.1099/vir.0.038398-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mature protein C of tick-borne encephalitis virus (TBEV) is cleaved from the polyprotein precursor by the viral NS2B/3 protease (NS2B/3(pro)). We showed previously that replacement of the NS2B/3(pro) cleavage site at the C terminus of protein C by the foot-and-mouth disease virus (FMDV) 2A StopGo sequence leads to the production of infectious virions. Here, we show that infectious virions can also be produced from a TBEV mutant bearing an inactivated 2A sequence through the expression of the FMDV 3C protease (3C(pro)) either in cis or in trans (from a TBEV replicon). Cleavage at the C terminus of protein C depended on the catalytic activity of 3C(pro) as well as on the presence of an optimized 3C(pro) cleavage site. Passage of the TBEV mutants bearing a 3C(pro) cleavage site either in the absence of 3C(pro) or in the presence of a catalytically inactive 3C(pro) led to the appearance of revertants in which protein C cleavage by NS2B/3(pro) had been regained. In three different revertants, a cleavage site for NS2B/3(pro), namely RR*C, was now present, leading to an elongated protein C. Furthermore, two revertants acquired additional mutations in the C terminus of protein C, eliminating two basic residues. Although these latter mutants showed wild-type levels of early RNA synthesis, their foci were smaller and an accumulation of protein C in the cytoplasm was observed. These findings suggest a role of the positive charge of the C terminus of protein C for budding of the nucleocapsid and further support the notion that TBEV protein C is a multifunctional protein.
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Affiliation(s)
- Sabrina Schrauf
- Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria
| | - Martina Kurz
- Max F. Perutz Laboratories, Medical University of Vienna, Dr. Bohr-Gasse 9/3, A-1030 Vienna, Austria
| | - Christian Taucher
- Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria
| | - Christian W. Mandl
- Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria
| | - Tim Skern
- Max F. Perutz Laboratories, Medical University of Vienna, Dr. Bohr-Gasse 9/3, A-1030 Vienna, Austria
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Zimmer G. RNA replicons - a new approach for influenza virus immunoprophylaxis. Viruses 2010; 2:413-434. [PMID: 21994644 PMCID: PMC3185613 DOI: 10.3390/v2020413] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Revised: 01/25/2010] [Accepted: 01/27/2010] [Indexed: 02/07/2023] Open
Abstract
RNA replicons are derived from either positive- or negative-strand RNA viruses. They represent disabled virus vectors that are not only avirulent, but also unable to revert to virulence. Due to autonomous RNA replication, RNA replicons are able to drive high level, cytosolic expression of recombinant antigens stimulating both the humoral and the cellular branch of the immune system. This review provides an update on the available literature covering influenza virus vaccines based on RNA replicons. The pros and cons of these vaccine strategies will be discussed and future perspectives disclosed.
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Affiliation(s)
- Gert Zimmer
- Institute of Virology and Immunoprophylaxis (IVI), Sensemattstrasse 293, CH-3147 Mittelhäusern, Switzerland
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14
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A trans-complementing recombination trap demonstrates a low propensity of flaviviruses for intermolecular recombination. J Virol 2010; 84:599-611. [PMID: 19864381 DOI: 10.1128/jvi.01063-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Intermolecular recombination between the genomes of closely related RNA viruses can result in the emergence of novel strains with altered pathogenic potential and antigenicity. Although recombination between flavivirus genomes has never been demonstrated experimentally, the potential risk of generating undesirable recombinants has nevertheless been a matter of concern and controversy with respect to the development of live flavivirus vaccines. As an experimental system for investigating the ability of flavivirus genomes to recombine, we developed a "recombination trap," which was designed to allow the products of rare recombination events to be selected and amplified. To do this, we established reciprocal packaging systems consisting of pairs of self-replicating subgenomic RNAs (replicons) derived from tick-borne encephalitis virus (TBEV), West Nile virus (WNV), and Japanese encephalitis virus (JEV) that could complement each other in trans and thus be propagated together in cell culture over multiple passages. Any infectious viruses with intact, full-length genomes that were generated by recombination of the two replicons would be selected and enriched by end point dilution passage, as was demonstrated in a spiking experiment in which a small amount of wild-type virus was mixed with the packaged replicons. Using the recombination trap and the JEV system, we detected two aberrant recombination events, both of which yielded unnatural genomes containing duplications. Infectious clones of both of these genomes yielded viruses with impaired growth properties. Despite the fact that the replicon pairs shared approximately 600 nucleotides of identical sequence where a precise homologous crossover event would have yielded a wild-type genome, this was not observed in any of these systems, and the TBEV and WNV systems did not yield any viable recombinant genomes at all. Our results show that intergenomic recombination can occur in the structural region of flaviviruses but that its frequency appears to be very low and that therefore it probably does not represent a major risk in the use of live, attenuated flavivirus vaccines.
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Rumyantsev AA, Zhang ZX, Gao QS, Moretti N, Brown N, Kleanthous H, Delagrave S, Guirakhoo F, Collett MS, Pugachev KV. Direct random insertion of an influenza virus immunologic determinant into the NS1 glycoprotein of a vaccine flavivirus. Virology 2010; 396:329-38. [DOI: 10.1016/j.virol.2009.10.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 10/13/2009] [Accepted: 10/20/2009] [Indexed: 01/19/2023]
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16
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Japanese encephalitis virus-based replicon RNAs/particles as an expression system for HIV-1 Pr55 Gag that is capable of producing virus-like particles. Virus Res 2009; 144:298-305. [PMID: 19406175 DOI: 10.1016/j.virusres.2009.04.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Revised: 04/16/2009] [Accepted: 04/20/2009] [Indexed: 11/23/2022]
Abstract
Ectopic expression of the structural protein Pr55(Gag) of HIV-1 has been limited by the presence of inhibitory sequences in the gag coding region that must normally be counteracted by HIV-1 Rev and RRE. Here, we describe a cytoplasmic RNA replicon based on the RNA genome of Japanese encephalitis virus (JEV) that is capable of expressing HIV-1 gag without requiring Rev/RRE. This replicon system was constructed by deleting all three JEV structural protein-coding regions (C, prM, and E) from the 5'-proximal region of the genome and simultaneously inserting an HIV-1 gag expression cassette driven by the internal ribosome entry site of encephalomyocarditis virus into the 3'-proximal noncoding region of the genome. Transfection of this JEV replicon RNA led to expression of Pr55(Gag) in the absence of Rev/RRE in the cytoplasm of hamster BHK-21, human HeLa, and mouse NIH/3T3 cells. Production of the Pr55(Gag) derived from this JEV replicon RNA appeared to be increased by approximately 3-fold when compared to that based on an alphavirus replicon RNA. Biochemical and morphological analyses demonstrated that the Pr55(Gag) proteins were released into the culture medium in the form of virus-like particles. We also observed that the JEV replicon RNAs expressing the Pr55(Gag) could be encapsidated into single-round infectious JEV replicon particles when transfected into a stable packaging cell line that provided the three JEV structural proteins in trans. This ectopic expression of the HIV-1 Pr55(Gag) by JEV-based replicon RNAs/particles in diverse cell types may represent a useful molecular platform for various biological applications in medicine and industry.
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Sub-genomic replicon and virus-like particles of Omsk hemorrhagic fever virus. Arch Virol 2009; 154:573-80. [PMID: 19277843 DOI: 10.1007/s00705-009-0345-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 02/24/2009] [Indexed: 10/21/2022]
Abstract
Omsk hemorrhagic fever virus (OHFV) is a member of the tick-borne encephalitis serocomplex of flaviviruses, and causes hemorrhagic disease in humans. To investigate the molecular mechanisms involved in OHFV pathogenesis, we constructed several subgenomic OHFV replicons containing large deletions in the structural region. Replicon RNA was introduced into BHK cells by transfection and the production of viral proteins was monitored by IFA. GFP and luciferase genes were inserted into the OHFV replicon, and these reporter genes were expressed in cells harboring replicating replicon RNA. OHFV replicons were packaged into single-round infectious virus-like particles (VLPs) by sequential transfection with replicon RNA and a plasmid expressing the viral structural proteins. Reporter genes were expressed in cells infected with VLPs, and the infection was inhibited by neutralizing antibodies. These replicon and VLP systems will be useful tools for investigating the molecular mechanism of OHFV pathogenicity.
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Miorin L, Maiuri P, Hoenninger V, Mandl C, Marcello A. Spatial and temporal organization of tick-borne encephalitis flavivirus replicated RNA in living cells. Virology 2008; 379:64-77. [DOI: 10.1016/j.virol.2008.06.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 04/10/2008] [Accepted: 06/18/2008] [Indexed: 10/21/2022]
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19
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Hoenninger VM, Rouha H, Orlinger KK, Miorin L, Marcello A, Kofler RM, Mandl CW. Analysis of the effects of alterations in the tick-borne encephalitis virus 3′-noncoding region on translation and RNA replication using reporter replicons. Virology 2008; 377:419-30. [DOI: 10.1016/j.virol.2008.04.035] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 04/19/2008] [Accepted: 04/25/2008] [Indexed: 10/22/2022]
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20
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Yun SI, Choi YJ, Yu XF, Song JY, Shin YH, Ju YR, Kim SY, Lee YM. Engineering the Japanese encephalitis virus RNA genome for the expression of foreign genes of various sizes: implications for packaging capacity and RNA replication efficiency. J Neurovirol 2008; 13:522-35. [PMID: 18097884 DOI: 10.1080/13550280701684651] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Using the RNA replication machinery of Japanese encephalitis virus (JEV), the authors have established and characterized three strategies for the expression of foreign genes. Initially, approximately 11 kb genomic RNA was engineered to express heterologous genes of various sizes by preferentially inserting a new cistron at the beginning of the 3' nontranslated variable region. RNA transfection yielded recombinant viruses that initiated foreign gene expression after infecting permissive cells. JEV was capable of packaging recombinant genomes as large as approximately 15 kb. However, larger genome size was inversely correlated with RNA replication efficiency and cytopathogenicity, with no significant change in infectivity. Second, a variety of self-replicating propagation-deficient viral replicons were constructed by introducing one to three in-frame deletions into the ectodomains of all the structural proteins of JEV. These replicons displayed a spectrum of RNA replication efficiency upon transfection, suggesting that remnant transmembrane domains play a suppressive role in this process. Third, the authors generated a panel of stable packaging cell lines (PCLs) providing all three JEV structural proteins in trans. These PCLs efficiently packaged viral replicon RNAs into single-round infectious viral replicon particles. These JEV-based virus/vector systems may provide useful tools for a variety of biological applications, including foreign gene expression, antiviral compound screening, and genetic immunization.
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Affiliation(s)
- Sang-Im Yun
- Department of Microbiology, College of Medicine and Medical Research Institute, Chungbuk National University, Cheongju, South Korea
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Orlinger KK, Kofler RM, Heinz FX, Hoenninger VM, Mandl CW. Selection and analysis of mutations in an encephalomyocarditis virus internal ribosome entry site that improve the efficiency of a bicistronic flavivirus construct. J Virol 2007; 81:12619-29. [PMID: 17855533 PMCID: PMC2168969 DOI: 10.1128/jvi.01017-07] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flaviviruses have a positive-stranded RNA genome, which simultaneously serves as an mRNA for translation of the viral proteins. All of the structural and nonstructural proteins are translated from a cap-dependent cistron as a single polyprotein precursor. In an earlier study (K. K. Orlinger, V. M. Hoenninger, R. M. Kofler, and C. W. Mandl, J. Virol. 80:12197-12208, 2006), it was demonstrated that an artificial bicistronic flavivirus genome, TBEV-bc, in which the region coding for the viral surface glycoproteins prM and E from tick-borne encephalitis virus (TBEV) had been removed from its natural context and inserted into the 3' noncoding region under the control of an internal ribosome entry site (IRES) from encephalomyocarditis virus (EMCV) produces viable, infectious virus when cells are transfected with this RNA. The rates of RNA replication and infectious particle formation were significantly lower with TBEV-bc, however, than with wild-type TBEV. In this study, we have identified two types of mutations, selected by passage in BHK-21 cells, that enhance the growth properties of TBEV-bc. The first type occurred in the E protein, and these most likely increase the affinity of the virus for heparan sulfate on the cell surface. The second type occurred in the inserted EMCV IRES, in the oligo(A) loop of the J-K stem-loop structure, a binding site for the eukaryotic translation initiation factor 4G. These included single-nucleotide substitutions as well as insertions of additional adenines in this loop. An A-to-C substitution in the oligo(A) loop decreased the efficiency of the IRES itself but nevertheless resulted in improved rates of virus particle formation and overall replication efficiency. These results demonstrate the need for proper balance in the competition for free template RNA between the viral RNA replication machinery and the cellular translation machinery at the two different start sites and also identify specific target sites for the improvement of bicistronic flavivirus expression vectors.
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Affiliation(s)
- Klaus K Orlinger
- Clinical Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095, Vienna, Austria
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22
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Reimann I, Semmler I, Beer M. Packaged replicons of bovine viral diarrhea virus are capable of inducing a protective immune response. Virology 2007; 366:377-86. [PMID: 17544049 DOI: 10.1016/j.virol.2007.05.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Revised: 04/12/2007] [Accepted: 05/04/2007] [Indexed: 12/17/2022]
Abstract
Bovine viral diarrhea virus (BVDV) replicons with deletions within the capsid, E(RNS) or E1 encoding region were constructed and efficiently packaged with a helper cell line. High titres of packaged replicons were observed as early as 24 h after transfection, whereas no virus progeny could be detected after transfection of non-complementing cells. Infection of bovine cell cultures with rescued viruses resulted in one cycle of replication without release of infectious virus particles, and no genetic reversion of the generated viruses was detected. Packaged replicons with a deletion within the capsid-coding region were characterized in vivo in immunization and challenge trials. Following immunization of calves with the replication-deficient virus, neither virus shedding nor viremia was detected. After challenge infection with virulent BVDV, all vaccinates were completely protected from disease as measured by the absence of viremia and shedding of challenge virus, which indicated that a 'sterilizing immunity' could be induced with the generated replication-deficient packaged replicons.
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Affiliation(s)
- Ilona Reimann
- Institute of Molecular Biology, Friedrich-Loeffler-Institut, Boddenblick 5a, 17493 Greifswald-Insel Riems, Germany
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23
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Bukreyev A, Skiadopoulos MH, Murphy BR, Collins PL. Nonsegmented negative-strand viruses as vaccine vectors. J Virol 2006; 80:10293-306. [PMID: 17041210 PMCID: PMC1641758 DOI: 10.1128/jvi.00919-06] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Alexander Bukreyev
- Building 50, Room 6505, NIAID, NIH, 50 South Dr., MSC 8007, Bethesda, MD 20892-8007, USA.
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Orlinger KK, Hoenninger VM, Kofler RM, Mandl CW. Construction and mutagenesis of an artificial bicistronic tick-borne encephalitis virus genome reveals an essential function of the second transmembrane region of protein e in flavivirus assembly. J Virol 2006; 80:12197-208. [PMID: 17035331 PMCID: PMC1676298 DOI: 10.1128/jvi.01540-06] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flaviviruses have a monopartite positive-stranded RNA genome, which serves as the sole mRNA for protein translation. Cap-dependent translation produces a polyprotein precursor that is co- and posttranslationally processed by proteases to yield the final protein products. In this study, using tick-borne encephalitis virus (TBEV), we constructed an artificial bicistronic flavivirus genome (TBEV-bc) in which the capsid protein and the nonstructural proteins were still encoded in the cap cistron but the coding region for the surface proteins prM and E was moved to a separate translation unit under the control of an internal ribosome entry site element inserted into the 3' noncoding region. Mutant TBEV-bc was shown to produce particles that packaged the bicistronic RNA genome and were infectious for BHK-21 cells and mice. Compared to wild-type controls, however, TBEV-bc was less efficient in both RNA replication and infectious particle formation. We took advantage of the separate expression of the E protein in this system to investigate the role in viral assembly of the second transmembrane region of protein E (E-TM2), a second copy of which was retained in the cap cistron to fulfill its other role as an internal signal sequence in the polyprotein. Deletion analysis and replacement of the entire TBEV E-TM2 region with its counterpart from another flavivirus revealed that this element, apart from its role as a signal sequence, is important for virion formation.
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Affiliation(s)
- Klaus K Orlinger
- Clinical Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria
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Fayzulin R, Scholle F, Petrakova O, Frolov I, Mason PW. Evaluation of replicative capacity and genetic stability of West Nile virus replicons using highly efficient packaging cell lines. Virology 2006; 351:196-209. [PMID: 16647099 DOI: 10.1016/j.virol.2006.02.036] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 02/23/2006] [Accepted: 02/25/2006] [Indexed: 11/16/2022]
Abstract
A stable cell system for high-efficiency packaging of West Nile virus (WNV) subgenomic replicons into virus-like particles (VLPs) was developed. VLPs could be propagated on these packaging cells and produced infectious foci similar to foci produced by WNV. Focus size correlated with the replicative capacity of WNV replicons, indicating that genome copy number, rather than amount of trans-complementing structural proteins, was rate-limiting in packaging of VLPs. Comparison of VLP production from replicon genomes encoding partial or complete C genes indicated that portions of C downstream of the cyclization sequence could improve genome replication or that cis expression of C could enhance packaging. Interestingly, a rapid loss of replicon-encoded reporter gene activity was detected within two serial passages of reporter gene-containing VLPs. The loss of reporter activity correlated with gene deletion and better VLP growth, indicating a powerful selection pressure for WNV genomes lacking reporter genes.
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Affiliation(s)
- Rafik Fayzulin
- Department of Pathology, 3.206B Mary Moody Northen Pavilion, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0436, USA
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Puig-Basagoiti F, Deas TS, Ren P, Tilgner M, Ferguson DM, Shi PY. High-throughput assays using a luciferase-expressing replicon, virus-like particles, and full-length virus for West Nile virus drug discovery. Antimicrob Agents Chemother 2006; 49:4980-8. [PMID: 16304161 PMCID: PMC1315944 DOI: 10.1128/aac.49.12.4980-4988.2005] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Many flaviviruses cause significant human disease worldwide. The development of flavivirus chemotherapy requires reliable high-throughput screening (HTS) assays. Although genetic systems have been developed for many flaviviruses, their usage in antiviral HTS assays has not been well explored. Here we compare three cell-based HTS assays for West Nile virus (WNV) drug discovery: (i) an assay that uses a cell line harboring a persistently replicating subgenomic replicon (containing a deletion of viral structural genes), (ii) an assay that uses packaged virus-like particles containing replicon RNA, and (iii) an assay that uses a full-length reporting virus. A Renilla luciferase gene was engineered into the replicon or into the full-length viral genome to monitor viral replication. Potential inhibitors could be identified through suppression of luciferase signals upon compound incubation. The antiviral assays were optimized in a 96-well format, validated with known WNV inhibitors, and proved useful in identifying a new inhibitor(s) through HTS of a compound library. In addition, because each assay encompasses multiple but discrete steps of the viral life cycle, the three systems could potentially be used to discriminate the mode of action of any inhibitor among viral entry (detected by assays ii and iii but not by assay i), replication (including viral translation and RNA synthesis; detected by assays i to iii), and virion assembly (detected by assay iii but not by assays i and ii). The approaches described in this study should be applicable to the development of cell-based assays for other flaviviruses.
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Affiliation(s)
- Francesc Puig-Basagoiti
- Wadsworth Center, New York State Department of Health, 120 New Scotland Avenue, Albany, New York 12208, USA
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Abstract
Tick-borne encephalitis virus (TBEV) is an important human pathogen that causes severe neurological illness in large areas of Europe and Asia. The neuropathogenesis of this disease agent is determined by its capacity to enter the central nervous system (CNS) after peripheral inoculation ("neuroinvasiveness") and its ability to replicate and cause damage within the CNS ("neurovirulence"). TBEV is a small, enveloped flavivirus with an unsegmented, positive-stranded RNA genome. Mutations affecting various steps of its natural replication cycle were shown to influence its neuropathogenic properties. This review describes experimental approaches and summarizes results on molecular determinants of neurovirulence and neuroinvasiveness that have been identified for this virus. It focuses on molecular mechanisms of three particular steps of the viral life cycle that have been studied in some detail for TBEV and two closely related tick-borne flaviviruses (Louping ill virus (LIV) and Langat virus (LGTV)), namely (i) the envelope protein E and its role in viral attachment to the cell surface, (ii) the 3'-noncoding region of the genome and its importance for viral RNA replication, and (iii) the capsid protein C and its role in the assembly process of infectious virus particles. Mutations affecting each of these three molecular targets significantly influence neuropathogenesis of TBEV, particularly its neuroinvasiveness. The understanding of molecular determinants of TBEV neuropathogenesis is relevant for vaccine development, also against other flaviviruses.
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Affiliation(s)
- Christian W Mandl
- Institute of Virology, Medical University of Vienna, Kinderspitalgasse 15, A-1095 Vienna, Austria.
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