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Howe G, Bal M, Wasmuth M, Massaro G, Rahim AA, Ali S, Rivera M, Schofield DM, Omotosho A, Ward J, Keshavarz-Moore E, Mason C, Nesbeth DN. An autonucleolytic suspension HEK293F host cell line for high-titer serum-free AAV5 and AAV9 production with reduced levels of DNA impurity. Mol Ther Methods Clin Dev 2024; 32:101317. [PMID: 39257529 PMCID: PMC11385518 DOI: 10.1016/j.omtm.2024.101317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 08/07/2024] [Indexed: 09/12/2024]
Abstract
We sought to engineer mammalian cells to secrete nuclease activity as a step toward removing the need to purchase commercial nucleases as process additions in bioprocessing of AAV5 and AAV9 as gene therapy vectors. Engineering HeLa cells with a serratial nuclease transgene did not bring about nuclease activity in surrounding media whereas engineering serum-free, suspension-adapted HEK293F cells with a staphylococcal nuclease transgene did result in detectable nuclease activity in surrounding media of the resultant stable transfectant cell line, "NuPro-1S." When cultivated in serum-free media, NuPro-1S cells yielded 3.06 × 1010 AAV5 viral genomes (vg)/mL via transient transfection, compared with 3.85 × 109 vg/mL from the parental HEK293F cell line. AAV9 production, followed by purification by ultracentrifugation, yielded 1.8 × 1013 vg/mL from NuPro-1S cells compared with 7.35 × 1012 vg/mL from HEK293F cells. AAV9 from both HEK293F and NuPro-1S showed almost identical ability to transduce cells embedded in a scaffold tissue mimic or cells of mouse neonate brain tissue in vivo. Comparison of agarose gel data indicated that the DNA content of AAV5 and AAV9 process streams from NuPro-1S cells was reduced by approximately 60% compared with HEK293F cells. A similar reduction in HEK293F cells was only achievable with a 50 U/mL Benzonase treatment.
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Affiliation(s)
- Geoffrey Howe
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Mehtap Bal
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Matt Wasmuth
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Giulia Massaro
- UCL School of Pharmacy, University College London, London WC1N 1AX, UK
| | - Ahad A Rahim
- UCL School of Pharmacy, University College London, London WC1N 1AX, UK
| | - Sadfer Ali
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Milena Rivera
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Desmond M Schofield
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Aminat Omotosho
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - John Ward
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Eli Keshavarz-Moore
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Chris Mason
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Darren N Nesbeth
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
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Ali S, Rivera M, Ward J, Keshavarz-Moore E, Mason C, Nesbeth DN. Serum-free lentiviral vector production is compatible with medium-resident nuclease activity arising from adherent HEK293T host cells engineered with a nuclease-encoding transgene. Heliyon 2023; 9:e17067. [PMID: 37484388 PMCID: PMC10361239 DOI: 10.1016/j.heliyon.2023.e17067] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 07/25/2023] Open
Abstract
At present lentiviral vector production for cell and gene therapy commonly involves transient plasmid transfection of mammalian cells cultivated in serum-containing media and addition of exogenous nuclease to reduce host cell and plasmid DNA impurities. Switching from serum-containing media to chemically-defined, serum free media, and minimising the number of process additions, are both increasingly regarded as necessary steps for simplifying and potentially automating lentiviral vector bioprocessing in future. Here we adapted human embryonic kidney 293T (HEK293T) cells to grow in serum-free media and also modified these cells with transgenes designed to encode a secreted nuclease activity. Stable transfection of HEK293T cells with transgenes encoding the Staphylococcus aureus nuclease B (NucB) open reading frame with either its native secretion signal peptide, the murine Igκ chain leader sequence or a novel viral transport fusion protein, all resulted in qualitatively detectable nuclease activity in serum-free media. Serum-free transient transfection of human embryonic kidney HEK293T cells stably harbouring the transgene for NucB with its native secretion signal produced active lentivirus in the presence of medium-resident nuclease activity. This lentivirus material was able to transduce the AGF-T immortal T cell line with a green fluorescent protein reporter payload at a level of 2.05 × 105 TU/mL (±3.34 × 104 TU/mL). Sufficient nuclease activity was present in 10 μL of this unconcentrated lentivirus material to degrade 1.5 μg DNA within 2 h at 37 °C, without agitation - conditions compatible with lentivirus production. These observations demonstrate that lentiviral vector production, by transient transfection, is compatible with host cells harbouring a nuclease transgene and evidencing nuclease activity in their surrounding growth media. This work provides a solid basis for future investigations, beyond the scope of this present study, in which commercial and academic groups can apply this approach to therapeutic payloads and potentially omit exogenous nuclease bioprocess additions.
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Challenges in Expression and Purification of Functional Fab Fragments in E. coli: Current Strategies and Perspectives. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8040175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Microbial host systems remain the most efficient and cost-effective chassis for biotherapeutics production. Escherichia coli is often the preferred host due to ease of cloning, scale-up, high product yields, and most importantly, cost-effective cultivation. E. coli often experience difficulties in producing biologically active therapeutics such as Fab fragments, which require protein folding and subsequent three-dimensional structure development. This paper outlines the recent improvements in upstream and downstream unit operations for producing Fab fragments in E. coli. Monoclonal antibody fragments (Fab) are a rising class of biotherapeutics and their production has been optimised using coexpression of molecular chaperones such as DsbC or DnaK–DnaJ–GrpE, as well as strain engineering for post-translational modifications such as disulphide bridging. Different media systems such as EnBase and combining nitrogen source supplementation with low-temperature cultivation have resulted in improvement in cell integrity, protein expression, and protein refolding. The recovery of native proteins from insoluble inclusion bodies can be improved by adjusting refolding conditions, as well as by incorporating multimodal and affinity chromatography for achieving high product yields in purification. Recent developments summarised in this review may tune the E. coli expression system to produce more complex and glycosylated proteins for therapeutic use in the near future.
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Slater SL, Mavridou DAI. Harnessing the potential of bacterial oxidative folding to aid protein production. Mol Microbiol 2021; 116:16-28. [PMID: 33576091 DOI: 10.1111/mmi.14700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 02/09/2021] [Indexed: 11/30/2022]
Abstract
Protein folding is central to both biological function and recombinant protein production. In bacterial expression systems, which are easy to use and offer high protein yields, production of the protein of interest in its native fold can be hampered by the limitations of endogenous posttranslational modification systems. Disulfide bond formation, entailing the covalent linkage of proximal cysteine amino acids, is a fundamental posttranslational modification reaction that often underpins protein stability, especially in extracytoplasmic environments. When these bonds are not formed correctly, the yield and activity of the resultant protein are dramatically decreased. Although the mechanism of oxidative protein folding is well understood, unwanted or incorrect disulfide bond formation often presents a stumbling block for the expression of cysteine-containing proteins in bacteria. It is therefore important to consider the biochemistry of prokaryotic disulfide bond formation systems in the context of protein production, in order to take advantage of the full potential of such pathways in biotechnology applications. Here, we provide a critical overview of the use of bacterial oxidative folding in protein production so far, and propose a practical decision-making workflow for exploiting disulfide bond formation for the expression of any given protein of interest.
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Affiliation(s)
- Sabrina L Slater
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
| | - Despoina A I Mavridou
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
- John Ring LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, TX, USA
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