Human γδ T cells expressing Vγ2Vδ2 TCRs monitor foreign- and self-prenyl pyrophosphate metabolites in isoprenoid biosynthesis to mediate immunity to microbes and tumors. Vγ2Vδ2 cells have been used for adoptive cancer immunotherapy with some partial and complete remissions. Most trials have used continuous zoledronate exposure to expand Vγ2Vδ2 cells. Zoledronate inhibits farnesyl pyrophosphate synthase causing isopentenyl pyrophosphate to accumulate that then stimulates Vγ2Vδ2 cells. Because zoledronate exposure is toxic, we hypothesized that a short period of exposure would reduce T cell toxicity but still be sufficient for monocytes uptake. Supporting this hypothesis, pulse zoledronate exposure with IL-2 resulted in more uniform expansion of Vγ2Vδ2 cells with higher purity and cell numbers as compared with continuous exposure. These Vγ2Vδ2 cells had higher levels of CD107a and perforin and slightly increased tumor cytotoxicity. Importantly, adoptive immunotherapy with Vγ2Vδ2 cells derived by pulse stimulation controlled human PC-3 prostate cancer tumors in immunodeficient NSG mice significantly better (halting tumor growth) than those derived by continuous stimulation. Pulse zoledronate stimulation of Vγ2Vδ2 cells with IL-15 also resulted in higher purity and cell numbers. Like with CD8 αβ T cells, IL-15 preserved early memory Vγ2Vδ2 T cell subsets better than IL-2. However, adoptive immunotherapy with Vγ2Vδ2 cells derived with IL-15 showed similar inhibition of PC-3 tumor growth as those derived with IL-2. Thus, pulse zoledronate stimulation maximizes the purity, quantity, and quality of expanded Vγ2Vδ2 cells. This simple modification to existing protocols would likely enhance the effectiveness of adoptively transferred Vγ2Vδ2 T cells.
University of Iowa / Veterans Health Care System