Payload-delivering engineered γδ T cells display enhanced cytotoxicity, persistence, and efficacy in preclinical models of osteosarcoma.

T cell–based cancer immunotherapy has typically relied on membrane-bound cytotoxicity enhancers such as chimeric antigen receptors expressed in autologous αβ T cells. These approaches are limited by tonic signaling of synthetic constructs and costs associated with manufacturing. γδ T cells are an emerging alternative for cellular therapy, having innate antitumor activity, potent antibody-dependent cellular cytotoxicity, and minimal alloreactivity. We present an immunotherapeutic platform technology built around the innate properties of the Vγ9Vδ2 T cell, harnessing specific characteristics of this cell type and offering an allocompatible cellular therapy that recruits bystander immunity. We engineered γδ T cells to secrete synthetic tumor-targeting opsonins in the form of an scFv-Fc fusion protein and a mitogenic IL-15Rα–IL-15 fusion protein (stIL15). Using GD2 as a model antigen, we show that GD2-specific opsonin-secreting Vγ9Vδ2 T cells (stIL15-OPS-γδ T cells) have enhanced cytotoxicity and promote bystander activity of other lymphoid and myeloid cells. Secretion of stIL-15 abrogated the need for exogenous cytokine supplementation and further mediated activation of bystander natural killer cells. Compared with unmodified γδ T cells, stIL15-OPS-γδ T cells exhibited superior in vivo control of subcutaneous tumors and persistence in the blood. Moreover, stIL15-OPS-γδ T cells were efficacious against patient-derived osteosarcomas in animal models and in vitro, where efficacy could be boosted with the addition of zoledronic acid. Together, the data identify stIL15-OPS-γδ T cells as a candidate allogeneic cell therapy platform combining direct cytolysis with bystander activation to promote tumor control. Editor's summary: Both tumor antigen-specific antibodies and cellular therapies based on those antibodies, such as chimeric antigen receptor (CAR) T cells, have shown promise as cancer therapies. Here, Fowler et al. opted to combine the two and added a third feature—the use of γδ T cells instead of their αβ counterparts. The authors engineered γδ T cells, which have the potential to be used as an allogeneic therapy, to secrete opsonins that bound the tumor antigen GD2 and activated Fc receptors on immune cells. They also included an IL-15Rα–IL-15 fusion protein to further improve γδ T cell function and persistence. The opsonins produced by the γδ T cells activated the engineered cells and bystander immune cells in vitro and in vivo. This resulted in efficacy against multiple tumor models in vivo, including orthotopic patient-derived osteosarcomas, particularly when zoledronic acid was used as well. Together, these data support further development of opsonin-secreting γδ T cells as a cancer immunotherapy. —Courtney Malo [ABSTRACT FROM AUTHOR]