Expansion and enrichment of gamma-delta (γδ) t cells from apheresed human product

Abstract

Although Vγ9Vδ2 T cells are a minor subset of T lymphocytes, this population is sought after for its ability to recognize antigens in a major histocompatibility complex (MHC)-independent manner and develop strong cytolytic effector function that makes it an ideal candidate for cancer immunotherapy. Due to the low frequency of Gamma-Delta (γδ) T cells in the peripheral blood, we developed an effective protocol to greatly expand a highly pure γδ T cells drug product for first-in-human use of allogeneic γδ T cells in patients with acute myeloid leukemia (AML). Using healthy donor apheresis as an allogenic cell source, the lymphocytes are isolated using a validated device for a counterflow centrifugation method of separating cells by size and density. The lymphocyte-rich fraction is utilized, and the γδ T cells are preferentially activated with zoledronic acid (FDA-approved) and interleukin (IL)-2 for 7 days. Following the preferential expansion of γδ T cells, a clinical-grade magnetic cell-separation device and TCRαβ beads are used to deplete contaminating T-cell receptor (TCR)αβ T cells. The highly enriched γδ T cells then undergo a second expansion using engineered artificial antigen-presenting cells (aAPCs) derived from K562 cells-genetically engineered to express single-chain variable fragment (scFv) for CD3 and CD28, 41BBL (CD137L) and IL15-RA-together with zoledronic acid and IL-2. Seeding all day-7 enriched γδ T cells in co-culture with the aAPCs facilitates the manufacture of highly pure γδ T cells with an average fold expansion of >229,000-fold from healthy donor blood.