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Seyed N, Taheri T, Rafati S. Live attenuated-nonpathogenic Leishmania and DNA structures as promising vaccine platforms against leishmaniasis: innovations can make waves. Front Microbiol 2024; 15:1326369. [PMID: 38633699 PMCID: PMC11021776 DOI: 10.3389/fmicb.2024.1326369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 03/12/2024] [Indexed: 04/19/2024] Open
Abstract
Leishmaniasis is a vector-borne disease caused by the protozoan parasite of Leishmania genus and is a complex disease affecting mostly tropical regions of the world. Unfortunately, despite the extensive effort made, there is no vaccine available for human use. Undoubtedly, a comprehensive understanding of the host-vector-parasite interaction is substantial for developing an effective prophylactic vaccine. Recently the role of sandfly saliva on disease progression has been uncovered which can make a substantial contribution in vaccine design. In this review we try to focus on the strategies that most probably meet the prerequisites of vaccine development (based on the current understandings) including live attenuated/non-pathogenic and subunit DNA vaccines. Innovative approaches such as reverse genetics, CRISP/R-Cas9 and antibiotic-free selection are now available to promisingly compensate for intrinsic drawbacks associated with these platforms. Our main goal is to call more attention toward the prerequisites of effective vaccine development while controlling the disease outspread is a substantial need.
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Affiliation(s)
- Negar Seyed
- Department of Immunotherapy and Leishmania Vaccine Research, Pasteur Institute of Iran, Tehran, Iran
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Pastor M, Quiviger M, Pailloux J, Scherman D, Marie C. Reduced Heterochromatin Formation on the pFAR4 Miniplasmid Allows Sustained Transgene Expression in the Mouse Liver. MOLECULAR THERAPY. NUCLEIC ACIDS 2020; 21:28-36. [PMID: 32505001 PMCID: PMC7270507 DOI: 10.1016/j.omtn.2020.05.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/30/2020] [Accepted: 05/14/2020] [Indexed: 12/22/2022]
Abstract
Non-viral gene delivery into the liver generally mediates a transient transgene expression. A comparative analysis was performed using two gene vectors, pFAR4 and pKAR4, which differ by the absence or presence of an antibiotic resistance marker, respectively. Both plasmids carried the same eukaryotic expression cassette composed of a sulfamidase (Sgsh) cDNA expressed from the human alpha antitrypsin liver-specific promoter. Hydrodynamic injection of the pFAR4 construct resulted in prolonged sulfamidase secretion from the liver, whereas delivery of the pKAR4 construct led to a sharp decrease in circulating enzyme. After induction of hepatocyte division, a rapid decline of sulfamidase expression occurred, indicating that the pFAR4 derivative was mostly episomal. Quantification analyses revealed that both plasmids were present at similar copy numbers, whereas Sgsh transcript levels remained high only in mice infused with the pFAR4 construct. Using a chromatin immunoprecipitation assay, it was established that the 5' end of the expression cassette carried by pKAR4 exhibited a 7.9-fold higher heterochromatin-to-euchromatin ratio than the pFAR4 construct, whereas a bisulfite treatment did not highlight any obvious differences in the methylation status of the two plasmids. Thus, by preventing transgene expression silencing, the pFAR4 gene vector allows a sustained transgene product secretion from the liver.
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Affiliation(s)
- Marie Pastor
- Université de Paris, UTCBS, CNRS, INSERM, 4, avenue de l'Observatoire, 75006 Paris, France
| | - Mickäel Quiviger
- Université de Paris, UTCBS, CNRS, INSERM, 4, avenue de l'Observatoire, 75006 Paris, France
| | - Julie Pailloux
- Université de Paris, UTCBS, CNRS, INSERM, 4, avenue de l'Observatoire, 75006 Paris, France
| | - Daniel Scherman
- Université de Paris, UTCBS, CNRS, INSERM, 4, avenue de l'Observatoire, 75006 Paris, France
| | - Corinne Marie
- Université de Paris, UTCBS, CNRS, INSERM, 4, avenue de l'Observatoire, 75006 Paris, France; Chimie ParisTech, PSL Research University, 75005 Paris, France.
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Plavec TV, Berlec A. Safety Aspects of Genetically Modified Lactic Acid Bacteria. Microorganisms 2020; 8:E297. [PMID: 32098042 PMCID: PMC7074969 DOI: 10.3390/microorganisms8020297] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/11/2020] [Accepted: 02/17/2020] [Indexed: 02/07/2023] Open
Abstract
Lactic acid bacteria (LAB) have a long history of use in the food industry. Some species are part of the normal human microbiota and have beneficial properties for human health. Their long-standing use and considerable biotechnological potential have led to the development of various systems for their engineering. Together with novel approaches such as CRISPR-Cas, the established systems for engineering now allow significant improvements to LAB strains. Nevertheless, genetically modified LAB (GM-LAB) still encounter disapproval and are under extensive regulatory requirements. This review presents data on the prospects for LAB to obtain 'generally recognized as safe' (GRAS) status. Genetic modification of LAB is discussed, together with problems that can arise from their engineering, including their dissemination into the environment and the spread of antibiotic resistance markers. Possible solutions that would allow the use of GM-LAB are described, such as biocontainment, alternative selection markers, and use of homologous DNA. The use of GM-LAB as cell factories in closed systems that prevent their environmental release is the least problematic aspect, and this is also discussed.
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Affiliation(s)
- Tina Vida Plavec
- Department of Biotechnology, Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia;
- Faculty of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - Aleš Berlec
- Department of Biotechnology, Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia;
- Faculty of Pharmacy, University of Ljubljana, SI-1000 Ljubljana, Slovenia
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The Antibiotic-free pFAR4 Vector Paired with the Sleeping Beauty Transposon System Mediates Efficient Transgene Delivery in Human Cells. MOLECULAR THERAPY. NUCLEIC ACIDS 2017; 11:57-67. [PMID: 29858090 PMCID: PMC5852330 DOI: 10.1016/j.omtn.2017.12.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 12/22/2017] [Accepted: 12/22/2017] [Indexed: 12/16/2022]
Abstract
The anti-angiogenic and neurogenic pigment epithelium-derived factor (PEDF) demonstrated a potency to control choroidal neovascularization in age-related macular degeneration (AMD) patients. The goal of the present study was the development of an efficient and safe technique to integrate, ex vivo, the PEDF gene into retinal pigment epithelial (RPE) cells for later transplantation to the subretinal space of AMD patients to allow continuous PEDF secretion in the vicinity of the affected macula. Because successful gene therapy approaches require efficient gene delivery and stable gene expression, we used the antibiotic-free pFAR4 mini-plasmid vector to deliver the hyperactive Sleeping Beauty transposon system, which mediates transgene integration into the genome of host cells. In an initial study, lipofection-mediated co-transfection of HeLa cells with the SB100X transposase gene and a reporter marker delivered by pFAR4 showed a 2-fold higher level of genetically modified cells than when using the pT2 vectors. Similarly, with the pFAR4 constructs, electroporation-mediated transfection of primary human RPE cells led to 2.4-fold higher secretion of recombinant PEDF protein, which was still maintained 8 months after transfection. Thus, our results show that the pFAR4 plasmid is a superior vector for the delivery and integration of transgenes into eukaryotic cells.
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Hardee CL, Arévalo-Soliz LM, Hornstein BD, Zechiedrich L. Advances in Non-Viral DNA Vectors for Gene Therapy. Genes (Basel) 2017; 8:E65. [PMID: 28208635 PMCID: PMC5333054 DOI: 10.3390/genes8020065] [Citation(s) in RCA: 223] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/01/2017] [Indexed: 01/08/2023] Open
Abstract
Uses of viral vectors have thus far eclipsed uses of non-viral vectors for gene therapy delivery in the clinic. Viral vectors, however, have certain issues involving genome integration, the inability to be delivered repeatedly, and possible host rejection. Fortunately, development of non-viral DNA vectors has progressed steadily, especially in plasmid vector length reduction, now allowing these tools to fill in specifically where viral or other non-viral vectors may not be the best options. In this review, we examine the improvements made to non-viral DNA gene therapy vectors, highlight opportunities for their further development, address therapeutic needs for which their use is the logical choice, and discuss their future expansion into the clinic.
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Affiliation(s)
- Cinnamon L. Hardee
- Interdepartmental Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA;
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (L.M.A.-S.); (B.D.H.)
| | - Lirio Milenka Arévalo-Soliz
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (L.M.A.-S.); (B.D.H.)
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Benjamin D. Hornstein
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (L.M.A.-S.); (B.D.H.)
| | - Lynn Zechiedrich
- Interdepartmental Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA;
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (L.M.A.-S.); (B.D.H.)
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA
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Mignon C, Sodoyer R, Werle B. Antibiotic-free selection in biotherapeutics: now and forever. Pathogens 2015; 4:157-81. [PMID: 25854922 PMCID: PMC4493468 DOI: 10.3390/pathogens4020157] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/09/2015] [Accepted: 03/23/2015] [Indexed: 11/16/2022] Open
Abstract
The continuously improving sophistication of molecular engineering techniques gives access to novel classes of bio-therapeutics and new challenges for their production in full respect of the strengthening regulations. Among these biologic agents are DNA based vaccines or gene therapy products and to a lesser extent genetically engineered live vaccines or delivery vehicles. The use of antibiotic-based selection, frequently associated with genetic manipulation of microorganism is currently undergoing a profound metamorphosis with the implementation and diversification of alternative selection means. This short review will present examples of alternatives to antibiotic selection and their context of application to highlight their ineluctable invasion of the bio-therapeutic world.
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Affiliation(s)
- Charlotte Mignon
- Technology Research Institute Bioaster, 317 avenue Jean-Jaurés, 69007 Lyon, France.
| | - Régis Sodoyer
- Technology Research Institute Bioaster, 317 avenue Jean-Jaurés, 69007 Lyon, France.
| | - Bettina Werle
- Technology Research Institute Bioaster, 317 avenue Jean-Jaurés, 69007 Lyon, France.
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Wright O, Stan GB, Ellis T. Building-in biosafety for synthetic biology. Microbiology (Reading) 2013; 159:1221-1235. [DOI: 10.1099/mic.0.066308-0] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Oliver Wright
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
- Centre for Synthetic Biology and Innovation, Imperial College London, London SW7 2AZ, UK
| | - Guy-Bart Stan
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
- Centre for Synthetic Biology and Innovation, Imperial College London, London SW7 2AZ, UK
| | - Tom Ellis
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
- Centre for Synthetic Biology and Innovation, Imperial College London, London SW7 2AZ, UK
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Scaling-up recombinant plasmid DNA for clinical trial: current concern, solution and status. Vaccine 2012; 30:5914-20. [PMID: 22406276 DOI: 10.1016/j.vaccine.2012.02.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/17/2012] [Accepted: 02/23/2012] [Indexed: 01/11/2023]
Abstract
Gene therapy and vaccines are rapidly developing field in which recombinant nucleic acids are introduced in mammalian cells for enhancement, restoration, initiation or silencing biochemical function. Beside simplicity in manipulation and rapid manufacture process, plasmid DNA-based vaccines have inherent features that make them promising vaccine candidates in a variety of diseases. This present review focuses on the safety concern of the genetic elements of plasmid such as propagation and expression units as well as their host genome for the production of recombinant plasmid DNA. The highlighted issues will be beneficial in characterizing and manufacturing plasmid DNA for save clinical use. Manipulation of regulatory units of plasmid will have impact towards addressing the safety concerns raised in human vaccine applications. The gene revolution with plasmid DNA by alteration of their plasmid and production host genetics will be promising for safe delivery and obtaining efficient outcomes.
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Abstract
Plasmid DNA (pDNA) is the base for promising DNA vaccines and gene therapies against many infectious, acquired, and genetic diseases, including HIV-AIDS, Ebola, Malaria, and different types of cancer, enteric pathogens, and influenza. Compared to conventional vaccines, DNA vaccines have many advantages such as high stability, not being infectious, focusing the immune response to only those antigens desired for immunization and long-term persistence of the vaccine protection. Especially in developing countries, where conventional effective vaccines are often unavailable or too expensive, there is a need for both new and improved vaccines. Therefore the demand of pDNA is expected to rise significantly in the near future. Since the injection of pDNA usually only leads to a weak immune response, several milligrams of DNA vaccine are necessary for immunization protection. Hence, there is a special interest to raise the product yield in order to reduce manufacturing costs. In this chapter, the different stages of plasmid DNA production are reviewed, from the vector design to downstream operation options. In particular, recent advances on cell engineering for improving plasmid DNA production are discussed.
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Affiliation(s)
- Alvaro R Lara
- Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana-Cuajimalpa, Mexico City, Mexico.
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Carnes AE, Luke JM, Vincent JM, Anderson S, Schukar A, Hodgson CP, Williams JA. Critical design criteria for minimal antibiotic-free plasmid vectors necessary to combine robust RNA Pol II and Pol III-mediated eukaryotic expression with high bacterial production yields. J Gene Med 2011; 12:818-31. [PMID: 20806425 DOI: 10.1002/jgm.1499] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND For safety considerations, regulatory agencies recommend the elimination of antibiotic resistance markers and non-essential sequences from plasmid DNA-based gene medicines. In the present study, we analyzed antibiotic-free (AF) vector design criteria impacting upon bacterial production and mammalian transgene expression. METHODS Both CMV-HTLV-I R RNA Pol II promoter (protein transgene) and murine U6 RNA Pol III promoter (RNA transgene) vector designs were studied. Plasmid production yield was assessed through inducible fed-batch fermentation. RNA Pol II-directed enhanced green fluorescent protein and RNA Pol III-directed RNA expression were quantified by fluorometry and quantitative real-time polymerase chain reaction, respectively, after transfection of human HEK293 cells. RESULTS Sucrose-selectable minimalized protein and therapeutic RNA expression vector designs that combined an RNA-based AF selection with highly productive fermentation manufacturing (>1000 mg/l plasmid DNA) and high-level in vivo expression of encoded products were identified. The AF selectable marker was also successfully applied to convert existing kanamycin-resistant DNA vaccine plasmids gWIZ and pVAX1 into AF vectors, demonstrating a general utility for retrofitting existing vectors. A minimum vector size for high yield plasmid fermentation was identified. A strategy for stable fermentation of plasmid dimers with improved vector potency and fermentation yields up to 1740 mg/l was developed. CONCLUSIONS We report the development of potent high yield AF gene medicine expression vectors for protein or RNA (e.g. short hairpin RNA or microRNA) products. These AF expression vectors were optimized to exceed a newly-identified size threshold for high copy plasmid replication and direct higher transgene expression levels than alternative vectors.
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Kroll J, Klinter S, Schneider C, Voss I, Steinbüchel A. Plasmid addiction systems: perspectives and applications in biotechnology. Microb Biotechnol 2010; 3:634-57. [PMID: 21255361 PMCID: PMC3815339 DOI: 10.1111/j.1751-7915.2010.00170.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 02/17/2010] [Indexed: 11/26/2022] Open
Abstract
Biotechnical production processes often operate with plasmid-based expression systems in well-established prokaryotic and eukaryotic hosts such as Escherichia coli or Saccharomyces cerevisiae, respectively. Genetically engineered organisms produce important chemicals, biopolymers, biofuels and high-value proteins like insulin. In those bioprocesses plasmids in recombinant hosts have an essential impact on productivity. Plasmid-free cells lead to losses in the entire product recovery and decrease the profitability of the whole process. Use of antibiotics in industrial fermentations is not an applicable option to maintain plasmid stability. Especially in pharmaceutical or GMP-based fermentation processes, deployed antibiotics must be inactivated and removed. Several plasmid addiction systems (PAS) were described in the literature. However, not every system has reached a full applicable state. This review compares most known addiction systems and is focusing on biotechnical applications.
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Affiliation(s)
- Jens Kroll
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität, D-48149 Münster, Germany
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Peubez I, Chaudet N, Mignon C, Hild G, Husson S, Courtois V, De Luca K, Speck D, Sodoyer R. Antibiotic-free selection in E. coli: new considerations for optimal design and improved production. Microb Cell Fact 2010; 9:65. [PMID: 20822537 PMCID: PMC2941680 DOI: 10.1186/1475-2859-9-65] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 09/07/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The increasing regulatory requirements to which biological agents are subjected will have a great impact in the field of industrial protein expression and production. There is an expectation that in a near future, there may be "zero tolerance" towards antibiotic-based selection and production systems. Besides the antibiotic itself, the antibiotic resistance gene is an important consideration. The complete absence of antibiotic-resistance gene being the only way to ensure that there is no propagation in the environment or transfer of resistance to pathogenic strains. RESULTS In a first step, we have designed a series of vectors, containing a stabilization element allowing a complete elimination of antibiotics during fermentation. Vectors were further improved in order to include alternative selection means such as the well known poison/antidote stabilization system. Eventually we propose an elegant positive pressure of selection ensuring the elimination of the antibiotic-resistance gene through homologous recombination. In addition, we have shown that the presence of an antibiotic resistance gene can indirectly reduce the amount of expressed protein, since even in absence of selection pressure the gene would be transcribed and account for an additional stress for the host during the fermentation process. CONCLUSIONS We propose a general strategy combining plasmid stabilization and antibiotic-free selection. The proposed host/vector system, completely devoid of antibiotic resistance gene at the end of construction, has the additional advantage of improving recombinant protein expression and/or plasmid recovery.
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Affiliation(s)
- Isabelle Peubez
- Research Department, Sanofi Pasteur, Marcel Mérieux, 69280 Marcy l'Etoile, France
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Marie C, Vandermeulen G, Quiviger M, Richard M, Préat V, Scherman D. pFARs, plasmids free of antibiotic resistance markers, display high-level transgene expression in muscle, skin and tumour cells. J Gene Med 2010; 12:323-32. [PMID: 20209487 DOI: 10.1002/jgm.1441] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Nonviral gene therapy requires a high yield and a low cost production of eukaryotic expression vectors that meet defined criteria such as biosafety and quality of pharmaceutical grade. To fulfil these objectives, we designed a novel antibiotic-free selection system. METHODS The proposed strategy relies on the suppression of a chromosomal amber mutation by a plasmid-borne function. We first introduced a nonsense mutation into the essential Escherichia coli thyA gene, resulting in thymidine auxotrophy. The bacterial strain was optimized for the production of small and novel plasmids free of antibiotic resistance markers (pFARs) and encoding an amber suppressor t-RNA. Finally, the potentiality of pFARs as eukaryotic expression vectors was assessed by monitoring luciferase activities after electrotransfer of LUC-encoding plasmids into various tissues. RESULTS The introduction of pFARs into the optimized bacterial strain restored normal growth to the auxotrophic mutant and allowed an efficient production of monomeric supercoiled plasmids. The electrotransfer of LUC-encoding pFAR into muscle led to high luciferase activities, demonstrating an efficient gene delivery. In transplanted tumours, transgene expression levels were superior after electrotransfer of the pFAR derivative compared to a plasmid carrying a kanamycin resistance gene. Finally, in skin, whereas luciferase activities decreased within 3 weeks after intradermal electrotransfer of a conventional expression vector, sustained luciferase expression was observed with the pFAR plasmid. CONCLUSIONS Thus, we have designed a novel strategy for the efficient production of biosafe plasmids and demonstrated their potentiality for nonviral gene delivery and high-level transgene expression in several tissues.
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Affiliation(s)
- Corinne Marie
- Université Paris Descartes, Faculté de Pharmacie, Unité de Pharmacologie Chimique et Génétique et d'Imagerie, Ecole Nationale Supérieure de Chimie de Paris, INSERM U1022, CNRS UMR8151, Paris, France.
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Use of mchI encoding immunity to the antimicrobial peptide microcin H47 as a plasmid selection marker in attenuated bacterial live vectors. Infect Immun 2008; 76:4422-30. [PMID: 18663003 DOI: 10.1128/iai.00487-08] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Live attenuated bacterial strains expressing heterologous antigens represent an attractive vaccine development strategy. However, the use of drug resistance genes for the selection of expression plasmids introduced into live vectors poses theoretical health risks. Therefore, we developed a novel approach for plasmid selection based on immunity to the antimicrobial peptide microcin H47 (MccH47). Two expression plasmids encoding the reporter green fluorescent protein (GFPuv) were constructed; selection markers comprised either mchI, conferring immunity to MccH47 (pGEN222I), or bla (encoding beta-lactamase), conferring conventional resistance to ampicillin (pGEN222). GFPuv-specific serum immunoglobulin G (IgG) antibody responses were analyzed in mice immunized intranasally either with Salmonella enterica serovar Typhi CVD 908-htrA or Shigella flexneri 2a CVD 1208S live vector and were boosted parenterally with purified GFPuv. Similar IgG antibody responses were observed for both pGEN222 and pGEN222I when either CVD 1208S or CVD 908-htrA(pGEN222I) was used as the carrier. Interestingly, CVD 908-htrA(pGEN222I) elicited a significantly higher IgG response than CVD 908-htrA(pGEN222). We also compared the priming potential of homologous priming either with CVD 908-htrA(pGEN222I) or CVD 1208S(pGEN222I) to heterologous priming first with CVD 908-htrA(pGEN222I) and then with CVD 1208S(pGEN222I) and vice versa. Immunization with two unrelated live vectors significantly enhanced the IgG responses compared to responses engendered by homologous CVD 908-htrA(pGEN222I) but not to those of CVD 1208S(pGEN222I). MccH47 offers an alternate system for plasmid selection in bacterial live vectors that greatly improves their clinical acceptability. Furthermore, the success of the heterologous priming strategy supports the feasibility of the future development of multivalent live vector-based immunization strategies against multiple human pathogens.
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Rational vector design for efficient non-viral gene delivery: challenges facing the use of plasmid DNA. Mol Biotechnol 2008; 39:97-104. [PMID: 18327557 DOI: 10.1007/s12033-008-9046-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Although non-viral gene delivery is a very straightforward technology, there are currently no FDA-approved gene medicinal products available. Therefore, improving potency, safety, and efficiency of current plasmid DNA vectors will be a major task for the near future. This article will provide an overview on factors influencing production yield and quality as well as safety issues that emerge from the vector design itself. Special focus will be on generating bacterial pDNA vectors by circumventing the use of antibiotic resistance genes, to generate safer gene medicinal products as well as smaller, more efficient DNA vectors.
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Mairhofer J, Pfaffenzeller I, Merz D, Grabherr R. A novel antibiotic free plasmid selection system: advances in safe and efficient DNA therapy. Biotechnol J 2008; 3:83-9. [PMID: 17806101 DOI: 10.1002/biot.200700141] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The presence of antibiotic resistance genes in the delivered plasmids is one of the drawbacks of modern gene therapy and DNA vaccine applications. Here, we describe a strategy that allows for plasmid selection in bacterial hosts, without the requirement of any selection marker. Several bacterial strains were modified, so that the plasmid's replicational inhibitor RNA I could suppress the translation of a growth essential gene by RNA-RNA antisense reaction. An essential gene (murA) was modified such that a repressor protein (tetR) would hamper its expression. Only in the presence of plasmid and, hence, RNA I, was tetR turned down and murA expressed. Different commercially available plasmids could be selected by various modified Escherichia coli strains. We further designed a minimalistic plasmid devoid of any selection marker. All of the clones (n=6) examined, when the modified strain JM109-murselect was used for selection, contained plasmids. Thus, we have designed bacterial host strains that for the first time serve to select and maintain plasmids without the use of any selection marker or other additional sequence on the plasmid. Consequently, such plasmids may not only be safer, but due to their decreased size, advantages for the manufacturer and higher transfection efficiencies are anticipated.
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Affiliation(s)
- Jürgen Mairhofer
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
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