Background Human γδ T cells are ideal candidates for tumor immunotherapy because of their natural tropism for tumor microenvironment, elicit rapid innate-like immune responses upon tumor recognition and the ability to orchestrate other tumor-infiltrating immune cells for tumor cell killing.¹ Our group has recently defined aspects of the mechanism of T-cell receptor (TCR) dependent activation of Vγ9Vδ2⁺ T cells by tumors following the presentation of phosphoantigens via the B7 immunoglobulin family-like butyrophilin 2A1 (BTN2A1) and BTN3A1.² Dysregulation of the mevalonate pathway in tumors can cause activation of Vγ9Vδ2⁺ T cells via phosphoantigen accumulation and induces γδ T cell chemotaxis toward tumor cells.^{3, 4} Most clinical studies so far have used aminobisphosphonates (to promote accumulation of phosphoantigens in cells) or synthetic phosphoantigen analogues such as bromohydrin pyrophosphate (BrHPP) and 2-methyl-3-butenyl-1-pyrophosphate (2M3B1PP) to activate Vγ9Vδ2⁺ T cells in cancer patients.^5–8 More recently, agonist antibodies against BTN3A (e.g., clone 20.1, ICT-01 and CTX-2026) have been identified and used as a phosphoantigen-independent approach to activate Vγ9Vδ2⁺ T cells for targeted cell killing.¹

Methods We are currently characterizing a number of anti-BTN2A1 antibodies that can potentially be used to modulate the activity of Vγ9Vδ2⁺ T cells in in vitro assays.

Results We have also established a pre-clinical humanized tumor model using NOD scid gamma (NSG) mice and showed delayed tumor growth in mice that received 4 rounds of human Vδ2⁺ γδ T cell adoptive cell transfer in combination with clone 20.1 agonist antibody, which will allow further characterization of our anti-BTN2A1 antibodies.

Conclusions Taken together, our study has demonstrated the potential to target BTN2A1 and BTN3A1 for Vγ9Vδ2⁺ T cell-based cancer immunotherapy development.

References

1. Chan KF, Da Gama Duarte J, Ostrouska S, Behren A. Gamma-delta T cells in the tumor microenvironment–interactions with other immune cells. Frontiers in Immunology. 2022;13:3598.

2. Rigau M, Ostrouska S, Fulford TS, Johnson DN, Woods K, Ruan Z, et al. Butyrophilin 2A1 is essential for phosphoantigen reactivity by γδ T cells. Science. 2020;367(6478):eaay5516.

3. Benzaïd I, Mönkkönen H, Stresing V, Bonnelye E, Green J, Mönkkönen J, et al. High phosphoantigen levels in bisphosphonate-treated human breast tumors promote Vγ9Vδ2 T-cell chemotaxis and cytotoxicity in vivo. Cancer research. 2011;71(13):4562–72.

4. Ashihara E, Munaka T, Kimura S, Nakagawa S, Nakagawa Y, Kanai M, et al. Isopentenyl pyrophosphate secreted from Zoledronate-stimulated myeloma cells, activates the chemotaxis of γδT cells. Biochemical and biophysical research communications. 2015;463(4):650–5.

5. Abe Y, Muto M, Nieda M, Nakagawa Y, Nicol A, Kaneko T, et al. Clinical and immunological evaluation of zoledronate-activated Vγ9γδ T-cell-based immunotherapy for patients with multiple myeloma. Experimental Hematology. 2009;37(8):956–68.

6. Meraviglia S, Eberl M, Vermijlen D, Todaro M, Buccheri S, Cicero G, et al. In vivo manipulation of Vγ9Vδ2 T cells with zoledronate and low-dose interleukin-2 for immunotherapy of advanced breast cancer patients. Clinical & Experimental Immunology. 2010;161(2):290–7.

7. Sebestyen Z, Prinz I, Déchanet-Merville J, Silva-Santos B, Kuball J. Translating gammadelta (γδ) T cells and their receptors into cancer cell therapies. Nature Reviews Drug Discovery. 2020;19(3):169–84.

8. Yazdanifar M, Barbarito G, Bertaina A, Airoldi I. γδ T cells: the ideal tool for cancer immunotherapy. Cells. 2020;9(5):1305.

Ethics Approval ‘This study was approved by Australian Red Cross for the isolation of human Vδ2+ γδ T cells from healthy donors’ peripheral blood mononuclear cells, agreement number: 21–07VIC-09.’

‘This study was approved by Austin Health Animal Ethics Committee for adoptive cell transfer of human Vδ2+ γδ T cells into NSG mice, AEC Reference number: A2020/05661.’