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Rethinking the Purification Process of Viral-based Biotherapeutics

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Friday, February 14, 2020 1:00pm

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This is a past event.

Chemical Engineering Grain Processing Seminar Series

Pratik Joshi

PhD Candidate
Department of Chemical Engineering
Michigan Technological University

Abstract: The demand for high throughput methods of viral-based biotherapeutics to fight viral and other incurable diseases has increased tremendously over the past two decades. The outreach of these vaccines and therapies is impeded by limited production capacity and slow production processes. Great progress in upstream processing has led to significantly higher titers of immunizing or therapeutic viruses. However, the manufacturing community has realized the need to upgrade the traditional downstream strategy. Current downstream methods, chromatography and filtration, are not optimal to efficiently process comparatively fragile and complex viral particles. The lack of platform technologies for downstream processing of viral therapeutics has led to a search for alternative approaches.

In regards to finding a solution, our approach is a liquid-liquid extraction based - aqueous two-phase system (ATPS). ATPS formed by two partially miscible aqueous solutions are known for being inexpensive, environmentally-friendly, provide mild environment for biologics, and can be easily scaled-up and processed continu-ously. Our work has explored an aqueous biocompatible polymer (polyethylene glycol, PEG) and citrate-based system with the goal to preferentially partition virions in the PEG-rich phase and contaminants in the citrate-rich phase. However, the challenge of not fully understanding the partitioning mechanism had resulted in a large experimental setup. Tie-line describes thermodynamically similar systems, separating into similar phase compositions. We have developed an optimization strategy by relating viral physiochemical characteristics (hydrophobicity and charge) and partitioning behavior of multiple viruses using a tie-line framework in the PEG 12kDa-citrate system. Virus partitioning behavior with increasing tie-line lengths provided an insight in the preferential driving forces for virus recovery as well as stability of viruses. Deduction of major influences of hydrophobic and electrostatic interactions between the viruses and phases allowed us to reduce the experimental designs for other viruses. Each virus exhibits different level of fragility and the optimum processing parameters might not be feasible for recovering functional virions, thus making viral processing more intricate. Impact of environmental stress on viral viability will be discussed. The following study employed naturally-occurring, water molecule-rearranging compounds called osmolytes in the ATPS to ease processability and generalize the virus purification process. Osmolytes restructure the relative phase behavior to selectively enhance the driving forces to elevate virus recovery. Our results provided circumstantial evidence on an underlying debate about the osmolyte stabilizing mechanism and supplements the growing theory of viruses being relatively more hydrophobic than smaller proteins.

Overall, our work is directed towards platforming downstream processing of vaccines using ATPS and currently a multivariate database is being generated for empirical predictions to accelerate process development of viral-based biotherapeutics. Interpretations of the current study on distinctive biophysical behavior of viruses allows for future innovations in vaccine candidate designs.

Bio: Pratik is a PhD candidate in the chemical engineering department, advised by Dr. Caryn Heldt. He finished his undergraduate degree in Petrochemical Engineering at University of Pune, India and joined the Heldt Bioseparations Laboratory in 2016. He has published or submitted 5 peer-reviewed journal papers during his graduate studies and has presented his research work in more than 10 regional, national, and international conferences during his graduate studies.

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