Targeted Co-delivery of Tumor Antigen and α-Galactosylceramide to CD141 Dendritic Cells Induces a Potent Tumor Antigen-Specific Human CD8 T Cell Response in Human Immune System Mice.

Active co-delivery of tumor antigens (Ag) and α-galactosylceramide (α-GalCer), a potent agonist for invariant Natural Killer T (NKT) cells, to cross-priming CD8α dendritic cells (DCs) was previously shown to promote strong anti-tumor responses in mice. Here, we designed a nanoparticle-based vaccine able to target human CD141 (BDCA3) DCs - the equivalent of murine CD8α DCs - and deliver both tumor Ag (Melan A) and α-GalCer. This nanovaccine was inoculated into humanized mice that mimic the human immune system (HIS) and possess functional NKT cells and CD8 T cells, called HIS-CD8/NKT mice. We found that multiple immunizations of HIS-CD8/NKT mice with the nanovaccine resulted in the activation and/or expansion of human CD141 DCs and NKT cells and ultimately elicited a potent Melan-A-specific CD8 T cell response, as determined by tetramer staining and ELISpot assay. Single-cell proteomics further detailed the highly polyfunctional CD8 T cells induced by the nanovaccine and revealed their predictive potential for vaccine potency. This finding demonstrates for the first time the unique ability of human NKT cells to license cross-priming DCs and adds a new dimension to the current strategy of cancer vaccine development.