Expansion of Human Peripheral Blood γδ T Cells using Zoledronate

Human gamma delta T cells can recognize and respond to a wide variety of stress-induced antigens, thereby developing innate broad anti-tumor and anti-infective activity. (1) The majority of gamma delta T cells in peripheral blood have the V gamma 9V delta 2 T cell receptor. These cells recognize antigen in a major histocompatibility complex-independent manner and develop strong cytolytic and Th1-like effector functions. (1)Therefore, gamma delta T cells are attractive candidate effector cells for cancer immunotherapy. V gamma 9V delta 2 T cells respond to phosphoantigens such as (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), which is synthesized in bacteria via isoprenoid biosynthesis; 2 and isopentenyl pyrophosphate (IPP), which is produced in eukaryotic cells through the mevalonate pathway. (3) In physiological condition, the generation of IPP in nontransformed cell is not sufficient for the activation of gamma delta T cells. Dysregulation of mevalonate pathway in tumor cells leads to accumulation of IPP and gamma delta T cells activation. (3) Because aminobisphosphonates (such as pamidronate or zoledronate) inhibit farnesyl pyrophosphate synthase (FPPS), the enzyme acting downstream of IPP in the mevalonate pathway, intracellular levels of IPP and sensitibity to gamma delta T cells recognition can be therapeutically increased by aminobisphosphonates. IPP accumulation is less efficient in nontransfomred cells than tumor cells with a pharmacologically relevant concentration of aminobisphosphonates, that allow us immunotherapy for cancer by activating gamma delta T cells with aminobisphosphonates. (4) Interestingly, IPP accumulates in monocytes when PBMC are treated with aminobisphosphonates, because of efficient drug uptake by these cells. (5) Monocytes that accumulate IPP become antigen-presenting cells and stimulate V gamma 9V delta 2 T cells in the peripheral blood. (6) Based on these mechanisms, we developed a technique for large-scale expansion of gamma delta T cell cultures using zoledronate and interleukin-2 (IL-2).(7) Other methods for expansion of gamma delta T cells utilize the synthetic phosphoantigens bromohydrin pyrophosphate (BrHPP) (8) or 2-methyl-3-butenyl-1-pyrophosphate (2M3B1PP).(9) All of these methods allow ex vivo expansion, resulting in large numbers of gamma delta T cells for use in adoptive immunotherapy. However, only zoledronate is an FDA-approved commercially available reagent. Zoledronate-expanded gamma delta T cells display CD27(-)CD45RA(-) effector memory phenotype and thier function can be evaluated by IFN-gamma production assay.(7)