T-Cell Expansion Using Perfusion in Closed-System Bioreactors
The ability to culture T-cells for Cell Therapeutic use is a critical tool for clinical applications. It is desirable to have the entire cell culture work-flow as closed as possible to prevent the introduction of contamination. The Wave Bioreactor System (GE Healthcare) for cell expansion is a closed-system that is the next generation means to culture cells (T-cells, NK-cells, Tregs, eg.) for Cell Therapy applications. Replacing flask-based protocols, perfusion can be used to remove spent media and add fresh media as often as the operator requires, all in a single closed bioreactor.
Instead of media changes in multiple flasks, the Wave perfusion system allows media to be fed into the cell bags during incubation. A “lily pad” floating filter within the culture allows media to be added or withdrawn, leaving the cells behind. Typically, 1 or 5 liters of volume is the final cell culture volume required prior to harvesting. Using a mass-balance, the perfusion software allows you to designate the desired volume (typically 250ml, 500ml, 750ml or 1L) to be perfused out (spent media) and in (fresh media) during a time course of the culture. A simple connection of the media bag to the perfusion tubing allows the pumps to perform the addition/removal. No handling or open flasks in the hood is required. As an economic value, monitored perfusion saves costly media and growth factor supplements required for cell culture expansion. Also multiple flasks and incubator space are not required. Although this perfusion application has been used for many years in antibody and virus production, its application for Cell Therapy is only in its infancy. Two recent publication highly recognized in the field have used Wave perfusion for T-cell (Kalos and Levine, et al. 2011, http://stm.sciencemag.org/content/3/95/95ra73.short) and tumor-infiltrating lymphocyte (Sadeghi et al., 2010, http://www.sciencedirect.com/science/article/pii/S0022175910003431) expansion. Currently only suspension cells can be expanded in this system, but many groups are working on alterations to the existing technique to allow for adherent cell expansion (primarily MSCs).
Upon completion of the culture, the Wave ReadyCircuit cell harvesting system can be used to volume-reduce the final product, allowing easy connections between the cell bag and the harvesting line. This system only requires two separate Watson-Marlow pumps; no expensive and bulky equipment is used. This reduces cost and space in a GMP facility. The pumps simply drive the cells and media through a single hollow-fiber membrane, allowing media to “wick” through the membrane walls while allowing the cells to pass through the system in a circular-loop fashion. High cell recoveries are seen, and its simple connection to the cell bag allows reduced contamination risks.