Activated iNKT cells exert both cytotoxic and helper functions. Importantly, they activate/recruit immune cells and have been implicated in tumour rejection and tumour immuno-surveillance. Our goal is to exploit iNKT cell anti-tumour properties in adoptive cell therapy and redirect their specificity towards tumour-associated antigens (TAAs) through T cell receptor (TCR) engineering. We hypothesize that engineered iNKT cells will be more effective than conventional CD8 T cells and provide long-term immunity.

We currently use the OT-I model TCR, which recognizes a peptide from the chicken ovalbumin (OVA) presented by MHC class-I. Expanded CD8 T cells and iNKT cells were transduced with retroviruses encoding the OT-I TCR. Engineered iNKT cells, but not CD8 T cells, showed an early robust response to OVA peptide presented by dendritic cells (DCs) by producing IFN-γ and TNF-α. Moreover, engineered iNKT cells also produce granzyme B and upregulate FasL, indicative of their cytotoxic properties. The kinetics and magnitude of their response towards OVA peptide were similar to their response towards cognate lipid antigens, suggesting that their innate functions were preserved. We are conducting in vitro cytotoxic assays to demonstrate direct cytotoxic function of our engineered iNKT cells to OVA-expressing B16F10 melanoma and EL4 lymphoma cell lines.

In adoptive cell therapy, protection correlates with the persistence of transferred cells in the host and their ability to traffic to tumour sites. Adoptive transfer experiments demonstrate that engineered iNKT cells not only persist in the host, but they also traffic to various organs. Moving forward, we will assess the short and long-term response of engineered iNKTs in vivo, as well as their ability to promote the rejection of B16F10-OVA or EL4-OVA cells and compare to that of engineered CD8 T cells.

Ultimately, we propose TCR-engineered iNKT cells will constitute a safe and more effective therapy for cancer treatment.