Production and purification of plasmid DNA vaccines: is there scope for further innovation?

Abstract

The demand for plasmid DNA (pDNA) has vastly increased over the past decade in response to significant advances that have been made in its application for gene therapy and vaccine development. Plasmid DNA-based vaccines are experiencing a resurgence due to success with prime-boost immunization strategies. The challenge has always been poor productivity and delivery of pDNA. Plasmid DNA-based vaccines have traditionally required milligram scale of GMP-grade product for vaccination due to the relatively low efficacy and duration of gene expression. However, efforts to increase pDNA vaccine effectiveness are evolving in genetic manipulations of bacterial host, improvements in product recovery and innovative delivery methods. This review summarizes recent advances in large-scale pDNA vaccine manufacturing, ranging from upstream processing, downstream processing and formulation, as such information is usually not available to the scientific community. The article will highlight technology gaps and offer insight on further scope of innovation.

Keywords::

• delivery
• downstream processing
• formulation
• manufacturing
• plasmid DNA vaccine
• process improvement
• purification
• technology gaps
• yield and recovery

Acknowledgements

Support from the following colleagues: George Adams, Claire Scanlan, Elina Gousseinov, Joe Orlando, Trish Greenhalgh, Benjamin Cacace, Michael Phillips, Christopher Gillespie, Chase Duclos-Orsello, David Beattie (EMD Millipore Corporation), Frédérique Klein, Nicolas Laroudie (Millipore SAS), Alex Eon-Duval (Merck Serono) are acknowledged.

We also acknowledge technical insights by Prof. Andrew Zydney (Pennsylvania State University), Dr. Dennis Panicali (Bavarian Nordic Immunotherapeutics), Dr. M. Susana Levy (consultant, previously at University College London), Prof. Ana Azevedo (Technical University of Lisbon).

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

Challenges emerge when scaling up the production and purification of plasmid DNA, especially if the projected high demand materializes. The key overall challenges that can be gleaned from the literature review are subsequently summarized.

• Low productivity of microbial fermentation due to copy number limitations in the relevant strains.

• Similarity of product and contaminants leading to low resolution in separations.

• High-viscosity product feed stream complicating downstream processing.

• Shear sensitivity of plasmids at mixing and filtration steps.

• Difficulty in achieving desired concentrations at the final TFF step.

• Need to eliminate multiple undesirable components from the process.

• Lack of platform process.

• Lack of integrated continuous process.