Natural killer (NK) cells are increasingly being recognized as agents for cancer immunotherapy. KIR2DS2 is an activating killer-cell immunoglobulin-like receptor (KIR) expressed by NK cells, which has been associated with protective responses to cancer and viral infections. KIR2DS2 binds conserved viral peptides in the context of MHC class I, but to date no cancer-associated peptide ligands that bind activating KIR have been described. In order to determine if targeting KIR was a feasible strategy for mobilizing anti-cancer immune responses we established a peptide-based KIR targeting DNA vaccine. Immunizing KIR-Tg mice with the vaccine construct generated in vivo peptide-specific activation of KIR2DS2-positive NK cells leading to canonical and cross-reactive peptide specific immune responses in vitro. Using immunopeptidomics we identified the nuclear export protein XPO1, which has been associated with poor prognosis in multiple cancers, as providing an HLA-C restricted cancer-associated peptide ligand for KIR2DS2-positive NK cells. DNA vaccination of KIR-Tg mice led to both peptide specific and non-specific tumor cell killing, and protective anti-cancer responses in vivo. We thus show the feasibility of targeting KIR as a strategy that activates NK cells to generate in vivo anti-cancer immune responses, and identify XPO1 as a novel target for NK cells.### Competing Interest StatementUniversity of Southampton (SIK, MDB, PR and RF) have a patent application pending for peptide-based immunotherapy. All other authors declared that no conflict of interests exist.

A DNA vaccine strategy to activate natural killer cells for therapeutic targeting of XPO1-positive tumors