Abstract 7229: Humanized mouse models of γδ T engraftment for the testing of cell based anti-cancer therapeutics

Abstract One of the major hurdles of T cell-based immune therapy is identifying a T cell receptor that works for all patients. The γδ T cells, which express T cell receptors that can recognize several evolutionarily conserved cell surface molecules commonly become elevated in cancer cells, may solve this problem. There is currently no mouse model capable of expanding these γδ T cell subsets in vivo. Using human peripheral blood mononuclear cells (PBMC) engrafted NSG mouse strains, we compared γδ T cell engraftment in mice with or without irradiation to explore whether irradiation can aid the expansion of human γδ T cells and if so, which of our new NSG derivatives is best suited for human γδ T cells expansion. Non-irradiated or irradiated NSG-MHC I/II double knock-out (DKO), NSG-FLT3- MHC I/II DKO (FDKO), and NSG-SGM3-IL-15 × MHC I/II DKO (SDKO) mice were engrafted with PBMCs. For non-irradiated studies, 7 different donors were used. For irradiated studies, 3 different donors were used. In the irradiated studies, mice were taken down 9 days post engraftment. In the non-irradiated studies, human leukocyte engraftment was monitored via flow cytometry staining of retro-orbital blood for up to 93 days. At indicated time points following engraftment, tissue samples were collected to enumerate the frequency and number of γδ T cells. Robust and rapid γδ T cell expansion was observed in all irradiated NSG derivatives with the SDKO mice showing the highest concentration of circulating γδ T cells 9 days post engraftment (40-70 γδ T cells/µL of blood) followed by the FDKO mice (20-50 γδ T cells/µL of blood) with the DKO mice showing the lowest (1-10 γδ T cells/µL of blood). The frequency of γδ T cells within the hCD45 population was 1-5% in all three strains, which is physiologically similar to that in humans. In addition, γδ T cells were found in the spleen and mucosal sites (e.g. colon and lungs) of engrafted mice. In non-irradiated mice, both SDKO and FDKO mice showed higher γδ T cell engraftment rates relative to the DKO mice up to 93 days post engraftment. However, the expansion rate was slower than that of the irradiated mice: reaching the highest percentage of engraftment 28-42 days post engraftment. The γδ T cells could be recovered from the blood, spleen, and lungs of SDKO and FDKO mice but almost devoid in the DKO mice. Interestingly, with some donors, more γδ T cells were found in the SDKO mice whereas with other donors, in the FDKO mice. Irradiated SDKO mice showed maximal expansion and recovery of γδ T cells from the spleen, blood, and mucosal sites. By comparison, the γδ T cell expansion was slower in the blood, spleen, and lungs of SDKO and FDKO non-irradiated mice but remained detectable even up to 93 days post engraftment while up to 80% of the DKO mice had lost their γδ T cell engraftment. Studies to investigate anti-tumor capacity of γδ T cells are currently underway. Citation Format: Kevin Tsai, Nancy Zheng, Beau Parry, Destanie Rose, James G. Keck, Li-Chin Yao. Humanized mouse models of γδ T engraftment for the testing of cell based anti-cancer therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7229.