Evaluation of a microfluidic chip-based cell sorter in clinical manufacturing processes to deplete or isolate CD4 regulatory T cells.

Background: Clinical scale manufacturing for cell therapies requires reliable methods to purify specific cell types. Few microfluidic chip-based cell sorters have been integrated into manufacturing processes of therapeutic cells. Reports have highlighted the need to assess current requirements and explore areas for improvement.

Study design and methods: We evaluated Highway1, a new microfluidic chip-based cell sorter in the context of good manufacturing practice (GMP)-compliant manufacturing processes involving purification of CD4 T cell subsets. Tests explored throughput and processing time limits, as required in GMP-compliant purification of regulatory T cells (Tregs) and of CD4 T cells free of CD4 Tregs. Findings were used to establish conditions with the best balance between processing time and yield.

Results: Best average recovery (60%) was obtained when processed at 1-1.5 million cells/mL, purifying a target population of 33%. Weighing recovery against processing time, a sample concentration of 2.0 million cells/mL offers the optimum condition for sorting CD4 T cells free of CD4 Tregs from healthy blood. Similar tests also show that this device allows for shorter overall processing times to purify CD4 Tregs than previously reported for other microfluidic chip-based sorters, with the additional benefit of an essentially user intervention-free operation.

Discussion: The Highway1 allows for reliable selection of a highly pure subpopulation of CD4 T cells in a GMP-compliant, cell therapy manufacturing setting. As with conventional sorters, the purification process for Tregs still needs to be preceded by a pre-enrichment process to keep the total processing time within an acceptable range for clinical-grade cell manufacturing.