Large Scale Ex Vivo Expansion of Γδ T Cells Using Artificial Antigen Presenting Cells for the Treatment of Acute Myeloid Leukemia

Patients with relapsed or refractory acute myeloid leukemia (AML) are at increased risk of mortality. Higher γδ T cell count in a bone marrow or peripheral blood of patients with leukemia is associated with better survival. However, γδ T cells are rare in the blood and functionally impaired or exhausted in patients with malignancies. Promising results are reported on the treatment of various malignancies with in vivo expansion of autologous γδ T cells using zoledronic acid (zol) and IL-2. Here we demonstrated that zol and IL-2, in combination with a novel genetically engineered K562 CD3/CD137L/CD28/IL15RA quadruplet artificial antigen presenting cell (aAPC), efficiently expand allogeneic donor-derived γδ T cells using a GMP-compliant protocol sufficient to achieve cell doses for future clinical use. We achieved a 633-fold expansion of γδ T cells after day 10 of co-culture with aAPC, the majority of which exhibited central (47%) and effector (43%) memory phenotypes. Additionally, >90% of the expanded γδ T cells expressed NKG2D, while they have low cell surface expression of PD1 and LAG2 inhibitory checkpoint receptors. In vitro real-time cytotoxicity analysis showed that expanded, previously cryopreserved, γδ T cells were effective in killing target cells. Our results demonstrate that large scale ex vivo expansion of donor-derived γδ T cells can be achieved with the use of CD3/CD137L/CD28/IL15RA quadruplet aAPC and zol/IL-2 for clinical application as promising antineoplastic immunotherapy.

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