Adding Help to an HLA-A*24:02 Tumor-Reactive γδTCR Increases Tumor Control

gamma delta T cell receptors (gamma delta TCRs) recognize a broad range of malignantly transformed cells in mainly a major histocompatibility complex (MHC)-independent manner, making them valuable additions to the engineered immune effector cell therapy that currently focuses primarily on alpha beta TCRs and chimeric antigen receptors (CARs). As an exception to the rule, we have previously identified a gamma delta TCR, which exerts antitumor reactivity against HLA-A*24:02-expressing malignant cells, however without the need for defined HLA-restricted peptides, and without exhibiting any sign of off-target toxicity in humanized HLA-A*24:02 transgenic NSG (NSG-A24:02) mouse models. This particular tumor-HLA-A*24:02-specific V gamma 5V delta 1TCR required CD8 alpha alpha co-receptor for its tumor reactive capacity when introduced into alpha beta T cells engineered to express a defined gamma delta TCR (TEG), referred to as TEG011; thus, it was only active in CD8(+) TEG011. We subsequently explored the concept of additional redirection of CD4(+) T cells through co-expression of the human CD8 alpha gene into CD4(+) and CD8(+) TEG011 cells, later referred as TEG011_CD8 alpha. Adoptive transfer of TEG011_CD8 alpha cells in humanized HLA-A*24:02 transgenic NSG (NSG-A24:02) mice injected with tumor HLA-A*24:02(+) cells showed superior tumor control in comparison to TEG011, and to mock control groups. The total percentage of mice with persisting TEG011_CD8 alpha cells, as well as the total number of TEG011_CD8 alpha cells per mice, was significantly improved over time, mainly due to a dominance of CD4(+)CD8(+) double-positive TEG011_CD8 alpha, which resulted in higher total counts of functional T cells in spleen and bone marrow. We observed that tumor clearance in the bone marrow of TEG011_CD8 alpha-treated mice associated with better human T cell infiltration, which was not observed in the TEG011-treated group. Overall, introduction of transgenic human CD8 alpha receptor on TEG011 improves antitumor reactivity against HLA-A*24:02(+) tumor cells and further enhances in vivo tumor control.