My PhD project has been conducted in the context of cancer immunotherapy which aims to manipulate the immune system of the cancer patient against his tumor.
More specifically, my thesis work has focused on three projects related to cancer immunotherapy. In the first project, I have studied the mechanisms underlying the onset of anergy in invariant Natural Killer T lymphocytes (iNKT) after a single injection of the CD1d ligand α-galactosylceramide (αGalCer). Our comparative study of various analogs of αGalCer has shown that rather polar ligands known to generate a Th2 type of iNKT cell response were also inducing less anergy than the apolar Th1 type αGalCer ligands. We also observed that all antigen presenting cells (APCs) induced similar levels of iNKT cell anergy when loaded with Th1 glycosphingolipids (GSLs). Finally, we observed that enriched GSL presentation within lipid raft domains of APCs, which is a hallmark of Th1 GSLs, is likely not required to induce iNKT cell anergy. Our hypothesis is that the induction of iNKT cell anergy might rather depend on the iNKT T cell receptor (TCR) recognition of the glycolipid.
My second project aimed at improving the adjuvant activity of the iNKT cell agonist glycolipid αGalCer, when formulated as a dendritic cell (DC) vaccine against cancer. In this concept, I chose a Th1-type αGalCer analog, as we demonstrated their superior capacity to induce the transactivation of DCs by iNKT cells. I could confirm the efficacy of αGalCer-loaded DCs to generate an antitumor CD8 T cell response. Importantly, I revealed the superior antitumor activity of the combined iNKT/DC vaccine with Programmed cell death protein 1 (PD1) blockade, known to restore the functionality of intratumoral T cells, as compared to the treatments alone. My results also showed that the combined antitumor activity between DC/αGalCer vaccine and anti-PD1 depended on the immunogenicity of the tumor model. Finally, my last project investigated the functionality of the resident TCR in CD8 T cells transduced with a chimeric antigen receptor (CAR). We observed that CAR CD8 T cells undergo massive apoptosis in vivo when activated via their TCR in the context of a bacterial or viral infection. Furthermore, CAR T cells, but not mock-transduced T cells, express high levels of Fas and FasL from day 6 post infection. Finally, the in vivo CAR T cell deletion upon TCR stimulation could not be rescued by the blockade of Fas signalling, suggesting that parallel signalling pathways contribute to the apoptosis of TCR-engaged CAR T cells. Altogether, my results have improved the comprehension of iNKT cells and in particular their potential for therapeutic cancer vaccines. Moreover, the results of the third project have revealed an important mechanism in CAR T cell therapy, which may allow new improvements for its application to solid tumors.