A novel iNKT-mediated vaccine maneuver overcomes PD-1-mediated T cell exhaustion in cancer (165.13)

Abstract Our immune system plays an important role in preventing cancer. However, tumor-derived immuno-suppression hinders effective anti-tumor immunity. T cell dysfunction or exhaustion in tumor-bearing hosts is one such mechanism. Numerous studies have identified PD-1 and Tim-3 as markers of exhausted T cells, and antibodies blocking PD-1 and Tim-3 have been shown to partially restore T cell function. We have found that both Tim-3 and PD-1 are expressed on CD8+ tumor-infiltrating lymphocytes (TILs) in an animal model of B cell lymphoma and that these cells represent the predominant fraction of T cells infiltrating tumors. We find that iNKT stimulation using the ligand, alpha-galactosylceramide, combined with TLR9 stimulation using the ligand, CpG, can down-regulate Tim-3 and PD-1 expression in TILs, restore TIL function as measured by proliferation and production of TNF and IFNg in response to tumor, and induce long-lasting therapeutic immune responses in mice with large advanced (>1cm2) tumors.