Bromohydrin pyrophosphate-stimulated Vγ9δ2 T cells expanded ex vivo from patients with poor-prognosis neuroblastoma lyse autologous primary tumor cells

Gamma/delta T cells (Vγ9δ2) contribute to innate immunity and exert natural cytotoxicity against a variety of tumors. Using a synthetic phosphoantigen (Bromohydrin Pyrophosphate, BrHPP), we amplified Vγ9δ2 T cells in vitro from neuroblastoma patients. In the presence of BrHPP and low doses of IL-2, robust proliferation of Vγ9δ2 T cells was obtained from peripheral blood mononuclear cells (PBMC) harvested at diagnosis. Moderate proliferation was observed from PBMC harvested after stem cell transplantation, whereas modest levels of Vγ9δ2 T cells were obtained from PBMC harvested after induction therapy. Proliferation was observed after a single in vitro stimulation with BrHPP. After 21 days in culture, Vγ9δ2 T cells represented more than 80% of cultured cells (a 50-fold expansion from baseline). Moreover, BrHPP-amplified Vγ9δ2 T cells from patients-expressed activation markers and were able to lyse allogeneic and autologous neuroblasts. This cytotoxic activity was γδ T-cell receptor-dependent. Clinical trials using BrHPP are warranted in patients with poor-prognosis neuroblastoma, either to expand patient-derived Vγ9δ2 T cells ex vivo or by direct administration to in vivo to boost the pool of resident Vγ9δ2 T cells in vivo.