Cutting Edge: Bispecific gd T Cell Engager Containing Heterodimeric BTN2A1 and BTN3A1 Promotes Targeted Activation of Vg9Vd2+T Cells in the Presence of Costimulation by CD28 or NKG2D

Vg9Vd2+ T cell-targeted immunotherapy is of interest to harness its MHC-independent cytotoxic potential against a variety of cancers. Recent studies have identified heterodimeric butyrophilin (BTN) 2A1 and BTN3A1 as the molecular entity providing signal 1 to the Vg9Vd2 TCR, but signal 2 costimulatory requirements remain unclear. Using a tumor cell-free assay, we demonstrated that a BTN2A1/3A1 heterodimeric fusion protein acti-vated human Vg9Vd2+ T cells, but only in the presence of costimulatory signal via CD28 or NK group 2 member D. Nonetheless, addition of a bispecific gd T cell engager BTN2A1/3A1-Fc-CD19scFv alone enhanced granzyme B-mediated killing of human CD19+ lymphoma cells when cocultured with Vg9Vd2+ T cells, suggesting expression of costimulatory ligand(s) on tumor cells is sufficient to satisfy the signal 2 requirement. These results highlight the parallels of signal 1 and signal 2 requirements in ab and gd T cell activation and demonstrate the utility of heterodimeric BTNs to pro -mote targeted activation of gd T cells.

Automated summary

Vg9Vd2+ T cell-targeted immunotherapy is a promising approach for cancer treatment. This study identified BTN2A1 and BTN3A1 as signal 1 molecules for Vg9Vd2 TCR activation and found that a costimulatory signal is required for optimal activation. Furthermore, a bispecific gd T cell engager BTN2A1/3A1-Fc-CD19scFv was shown to enhance killing of CD19+ lymphoma cells, indicating the importance of costimulatory ligands on tumor cells. These findings highlight the similarities between signal 1 and signal 2 requirements in ab and gd T cell activation and demonstrate the potential of heterodimeric BTNs for targeted activation of gd T cells.