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Multidose Transient Transfection of HEK293 Cells Modulates rAAV2/5 Rep Protein Expression and Influences the Enrichment Fraction of Filled Capsids
  • +14
  • Richard Braatz,
  • Prasanna Srinivasan,
  • Christopher T. Canova,
  • Sha Sha,
  • Tam N. T. Nguyen,
  • John Joseph,
  • Jose Sangerman,
  • Andrew J. Maloney,
  • Georgios Katsikis,
  • Rui Wen Ou,
  • Moo Sun Hong,
  • Jaclyn Ng,
  • Caleb Neufeld,
  • Jacqueline Wolfrum,
  • Paul Barone,
  • Anthony Sinskey,
  • Stacy Springs
Richard Braatz
Massachusetts Institute of Technology

Corresponding Author:[email protected]

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Prasanna Srinivasan
Massachusetts Institute of Technology
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Christopher T. Canova
Massachusetts Institute of Technology Department of Chemical Engineering
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Sha Sha
Ultragenyx Pharmaceutical Inc
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Tam N. T. Nguyen
BioNTech US Inc
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John Joseph
Massachusetts Institute of Technology
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Jose Sangerman
Massachusetts Institute of Technology
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Andrew J. Maloney
Amgen Inc Cambridge MA
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Georgios Katsikis
Anthology
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Rui Wen Ou
Massachusetts Institute of Technology Department of Biology
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Moo Sun Hong
Seoul National University
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Jaclyn Ng
Stanford University
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Caleb Neufeld
Massachusetts Institute of Technology
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Jacqueline Wolfrum
Massachusetts Institute of Technology
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Paul Barone
Massachusetts Institute of Technology
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Anthony Sinskey
Massachusetts Institute of Technology Department of Biology
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Stacy Springs
Massachusetts Institute of Technology
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Abstract

Recombinant adeno-associated virus (rAAV) is a commonly used in vivo gene therapy vector because of its non-pathogenicity, long-term transgene expression, broad tropism, and ability to transduce both dividing and non-dividing cells. However, rAAV vector production via transient transfection of mammalian cells typically yields a low fraction of filled-to-total capsids (~1–30% of total capsids produced). Analysis of our previously developed mechanistic model for rAAV2/5 production attributed these low fill fractions to a poorly coordinated timeline between capsid synthesis and viral DNA replication and the repression of later phase capsid formation by Rep proteins. Here, we extend the model by quantifying the expression dynamics of total Rep proteins and their influence on the key steps of rAAV2/5 production using a multiple dosing transfection of human embryonic kidney 293 (HEK293) cells. We report that the availability of pre-formed empty capsids and viral DNA copies per cell are not limiting to the capsid filling reaction. However, optimal expression of Rep proteins (< 240 ± 13 ag per cell) enables enrichment of the filled capsid population (> 12% of total capsids/cell) upstream. Our analysis suggests increased enrichment of filled capsids via regulating the expression of Rep proteins is possible but at the expense of per cell capsid titer in a triple plasmid transfection. Our study reveals an intrinsic limitation of scaling rAAV2/5 vector genome (vg) production and underscores the need for approaches that allow for regulating the expression of Rep proteins to maximize vg titer per cell upstream.
05 Feb 2024Submitted to Biotechnology and Bioengineering
05 Feb 2024Submission Checks Completed
05 Feb 2024Assigned to Editor
05 Feb 2024Review(s) Completed, Editorial Evaluation Pending
29 Feb 2024Reviewer(s) Assigned
12 Apr 2024Editorial Decision: Revise Major
23 Jul 2024Reviewer(s) Assigned
04 Aug 2024Review(s) Completed, Editorial Evaluation Pending
04 Aug 2024Editorial Decision: Accept