Automatic Generation of Alloreactivity-Reduced Donor Lymphocytes and Hematopoietic Stem Cells from the Same Mobilized Apheresis Product

INTRODUCTION: In vitro or in vivo depletion of alloreactive T cells can facilitate haplo-identical hematopoietic stem cell transplantation (HSCT). Very satisfactory transplant outcomes were thus reported for TCRαβ/CD19-depleted hematopoietic stem/progenitor cell (HSPC) grafts. However, the current semi-automatic manufacturing process, although robust, still requires a significant amount of time to be completed. Towards advancing and further facilitating large scale cell processing, a new TCRαβ/CD19 depletion module combined with a, previously described, CD45RA depletion module (to serve as allo-reactivity attenuated donor lymphocyte infusion) was established on the CliniMACS Prodigy.

METHODS: We evaluated six apheresis products from G-CSF-mobilized volunteer donors which were split, one portion each depleted of CD45RA⁺ or of TCRα/β⁺ and CD19⁺ cells. Products were assessed for recovery of HSPCs and other mature subsets, as well as depletion of targeted cells using flow cytometry. Effects of apheresis and product age post 48 hours storage at 2‑8 °C as well as freeze-thawing on product viability and recovery of WBC and HPSCs were assessed by flow cytometry.

RESULTS: Ten sequential depletions were technically uneventful, proceeding automatically with minimal hands-on time beyond tubing set installation. Depletion of CD45RA⁺, TCRα/β⁺ and CD19⁺ cells was nearly complete, and at least equivalent to previous reports, achieving mean depletions of 4 log of targeted cells for both products. HSPC products retained TCRγ/δ⁺ and NK cells. 48 hours storage of apheresis product was associated with the expected modest loss of HSPCs, but depletions proceeded efficiently. Depleted products were stable until at least 72 hours after apheresis with stem cell viabilities >90%. Freeze-thawing resulted in loss of NK cells; post-thaw recovery of viable CD45⁺ and HSPCs was >70% and in line with expectation.

CONCLUSION: The closed, GMP-compatible process generates two separate medicinal products from the same mobilized apheresis product. The CD45RA-depleted products contained functional memory T cells, whereas the TCRαβ/CD19-depleted products included HSPCs, TCRγ/δ⁺ and NK cells . Both products are predicted to be effectively depleted of GvH-reactivity while providing immunological surveillance, in support of haplo-identical HSCT.