Vγ9Vδ2 T Cells Concurrently Kill Cancer Cells and Cross-Present Tumor Antigens

The human V gamma 9V delta 2 T cell is a unique cell type that holds great potential in immunotherapy of cancer. In particular, the therapeutic potential of this cell type in adoptive cell therapy (ACT) has gained interest. In this regard optimization of in vitro expansion methods and functional characterization is desirable. We show that V gamma 9V delta 2 T cells, expanded in vitro with zoledronic acid (Zometa or ZOL) and Interleukin-2 (IL-2), are efficient cancer cell killers with a trend towards increased killing efficacy after prolonged expansion time. Thus, V gamma 9V delta 2 T cells expanded for 25 days in vitro killed prostate cancer cells more efficiently than V gamma 9V delta 2 T cells expanded for 9 days. These data are supported by phenotype characteristics, showing increased expression of CD56 and NKG2D over time, reaching above 90% positive cells after 25 days of expansion. At the early stage of expansion, we demonstrate that V gamma 9V delta 2 T cells are capable of cross-presenting tumor antigens. In this regard, our data show that V gamma 9V delta 2 T cells can take up tumor-associated antigens (TAA) gp100, MART-1 and MAGE-A3 - either as long peptide or recombinant protein - and then present TAA-derived peptides on the cell surface in the context of HLA class I molecules, demonstrated by their recognition as targets by peptide-specific CD8 T cells. Importantly, we show that cross-presentation is impaired by the proteasome inhibitor lactacystin. In conclusion, our data indicate that V gamma 9V delta 2 T cells are broadly tumor-specific killers with the additional ability to cross-present MHC class I-restricted peptides, thereby inducing or supporting tumor-specific alpha beta TCR CD8 T cell responses. The dual functionality is dynamic during in vitro expansion, yet, both functions are of interest to explore in ACT for cancer therapy.

Automated summary

Human Vγ9Vδ2 T cells expanded in vitro efficiently kill cancer cells, have the ability to cross-present MHC class I-restricted peptides, and support tumor-specific CD8 T cell responses.