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Nguyen TN, Sha S, Hong MS, Maloney AJ, Barone PW, Neufeld C, Wolfrum J, Springs SL, Sinskey AJ, Braatz RD. Mechanistic model for production of recombinant adeno-associated virus via triple transfection of HEK293 cells. Mol Ther Methods Clin Dev 2021; 21:642-655. [PMID: 34095346 PMCID: PMC8143981 DOI: 10.1016/j.omtm.2021.04.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/08/2021] [Indexed: 02/08/2023]
Abstract
Manufacturing of recombinant adeno-associated virus (rAAV) viral vectors remains challenging, with low yields and low full:empty capsid ratios in the harvest. To elucidate the dynamics of recombinant viral production, we develop a mechanistic model for the synthesis of rAAV viral vectors by triple plasmid transfection based on the underlying biological processes derived from wild-type AAV. The model covers major steps starting from exogenous DNA delivery to the reaction cascade that forms viral proteins and DNA, which subsequently result in filled capsids, and the complex functions of the Rep protein as a regulator of the packaging plasmid gene expression and a catalyst for viral DNA packaging. We estimate kinetic parameters using dynamic data from literature and in-house triple transient transfection experiments. Model predictions of productivity changes as a result of the varied input plasmid ratio are benchmarked against transfection data from the literature. Sensitivity analysis suggests that (1) the poorly coordinated timeline of capsid synthesis and viral DNA replication results in a low ratio of full virions in harvest, and (2) repressive function of the Rep protein could be impeding capsid production at a later phase. The analyses from the mathematical model provide testable hypotheses for evaluation and reveal potential process bottlenecks that can be investigated.
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Affiliation(s)
- Tam N.T. Nguyen
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Sha Sha
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Moo Sun Hong
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Andrew J. Maloney
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Paul W. Barone
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Caleb Neufeld
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jacqueline Wolfrum
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Stacy L. Springs
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Anthony J. Sinskey
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Richard D. Braatz
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Center for Biomedical Innovation, Massachusetts Institute of Technology, Cambridge, MA, USA
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Analysis of the Level of Plasmid-Derived mRNA in the Presence of Residual Plasmid DNA by Two-Step Quantitative RT-PCR. Methods Protoc 2020; 3:mps3020040. [PMID: 32456168 PMCID: PMC7359704 DOI: 10.3390/mps3020040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/19/2020] [Accepted: 05/21/2020] [Indexed: 11/17/2022] Open
Abstract
In transfection experiments with mammalian cells aiming to overexpress a specific protein, it is often necessary to correctly quantify the level of the recombinant and the corresponding endogenous mRNA. In our case, mouse calvarial osteoblasts were transfected with a vector containing the complete Pex11β cDNA (plasmid DNA). The Pex11β mRNA level, as calculated using the RT-qPCR product, was unrealistically higher (>1000-fold) in transfected compared to non-transfected cells, and we assumed that there were large amounts of contaminating plasmid DNA in the RNA sample. Thus, we searched for a simple way to distinguish between plasmid-derived mRNA, endogenous genome-derived mRNA and plasmid DNA, with minimal changes to standard RT-PCR techniques. We succeeded by performing a plasmid mRNA-specific reverse transcription, and the plasmid cDNA was additionally tagged with a nonsense tail. A subsequent standard qPCR was conducted using appropriate PCR primers annealing to the plasmid cDNA and to the nonsense tail. Using this method, we were able to determine the specific amount of mRNA derived from the transfected plasmid DNA in comparison to the endogenous genome-derived mRNA, and thus the transfection and transcription efficiency.
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Schlaeger TM. Nonintegrating Human Somatic Cell Reprogramming Methods. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2018; 163:1-21. [PMID: 29075799 DOI: 10.1007/10_2017_29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Traditional biomedical research and preclinical studies frequently rely on animal models and repeatedly draw on a relatively small set of human cell lines, such as HeLa, HEK293, HepG2, HL60, and PANC1 cells. However, animal models often fail to reproduce important clinical phenotypes and conventional cell lines only represent a small number of cell types or diseases, have very limited ethnic/genetic diversity, and either senesce quickly or carry potentially confounding immortalizing mutations. In recent years, human pluripotent stem cells have attracted a lot of attention, in part because these cells promise more precise modeling of human diseases. Expectations are also high that pluripotent stem cell technologies can deliver cell-based therapeutics for the cure of a wide range of degenerative and other diseases. This review focuses on episomal and Sendai viral reprogramming modalities, which are the most popular methods for generating transgene-free human induced pluripotent stem cells (hiPSCs) from easily accessible cell sources. Graphical Abstract.
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Affiliation(s)
- Thorsten M Schlaeger
- Stem Cell Program, Boston Children's Hospital, Karp RB09213, 1 Blackfan Circle, Boston, MA, 02446, USA.
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Roelse M, Henquet MGL, Verhoeven HA, de Ruijter NCA, Wehrens R, van Lenthe MS, Witkamp RF, Hall RD, Jongsma MA. Calcium Imaging of GPCR Activation Using Arrays of Reverse Transfected HEK293 Cells in a Microfluidic System. SENSORS 2018; 18:s18020602. [PMID: 29462903 PMCID: PMC5855233 DOI: 10.3390/s18020602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 02/06/2018] [Accepted: 02/12/2018] [Indexed: 11/16/2022]
Abstract
Reverse-transfected cell arrays in microfluidic systems have great potential to perform large-scale parallel screening of G protein-coupled receptor (GPCR) activation. Here, we report the preparation of a novel platform using reverse transfection of HEK293 cells, imaging by stereo-fluorescence microscopy in a flowcell format, real-time monitoring of cytosolic calcium ion fluctuations using the fluorescent protein Cameleon and analysis of GPCR responses to sequential sample exposures. To determine the relationship between DNA concentration and gene expression, we analyzed cell arrays made with variable concentrations of plasmid DNA encoding fluorescent proteins and the Neurokinin 1 (NK1) receptor. We observed pronounced effects on gene expression of both the specific and total DNA concentration. Reverse transfected spots with NK1 plasmid DNA at 1% of total DNA still resulted in detectable NK1 activation when exposed to its ligand. By varying the GPCR DNA concentration in reverse transfection, the sensitivity and robustness of the receptor response for sequential sample exposures was optimized. An injection series is shown for an array containing the NK1 receptor, bitter receptor TAS2R8 and controls. Both receptors were exposed 14 times to alternating samples of two ligands. Specific responses remained reproducible. This platform introduces new opportunities for high throughput screening of GPCR libraries.
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Affiliation(s)
- Margriet Roelse
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
- Laboratory of Plant Physiology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.
| | - Maurice G L Henquet
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
| | - Harrie A Verhoeven
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
| | - Norbert C A de Ruijter
- Laboratory of Cell Biology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.
| | - Ron Wehrens
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
- BU Biometris, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.
| | - Marco S van Lenthe
- BU Biometris, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.
| | - Renger F Witkamp
- Human Nutrition and Health, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - Robert D Hall
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
- Laboratory of Plant Physiology, Wageningen University and Research, 6708 PB Wageningen, The Netherlands.
| | - Maarten A Jongsma
- BU Bioscience, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
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