Peptide:MHC dependent activation of natural killer cells through KIR2DS2 generates anti-tumor responses

Abstract

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.

Activating receptor KIR2DS2 bound to HLA‐C1 reveals the novel recognition features of activating receptor

“…'AT' motif at p7 and p8 of peptide is a conserved sequence when KIR2DS2 recognizes highly conserved flaviviruses and hepatitis C peptides found by Salim et al [24]. Currently, three peptides were validated to be involved in the recognition between KIR2DS2 and HLA-C*0102, LNPSVAATL (from HCV), IVDLMCHATF (from Dengue or Zika) and NAPLVHATL (from XPO1 protein) [24,45]. All three peptides have AT motif in p7 and p8.…”

“…The importance of this recognition motif is outlined in our study and may be used as a guide for the identification of antigenic peptides for NK cells in future. When those peptides are used in peptide-based KIRtargeting DNA vaccine, the 'AT' motif is indispensable, and if 'AT' is replaced with 'AA', it will not show any effect [45]. Overall, we argue the sequence of peptides and the recognition machines are vital for exploring novel antiviral or anti-tumour treatments.…”

“…This provides more opportunities for the selection and design of peptide products in immunotherapy when targeting NK cells [16,32]. In the case of KIR2DS2, using a crossing-reactive peptide also brought a surprisingly positive result of triggering a tumour-specific immune response [45]. At the same time, this cross-reactivity poses a potentially dangerous side effect, which warrants attention in future research and clinical trials.…”

“…Overall, we argue the sequence of peptides and the recognition machines are vital for exploring novel antiviral or anti-tumour treatments. Peptide-based KIR-targeting DNA vaccines have shown surprising anti-tumour effects and are providing new directions for immunotherapy [45]. However, due to the limited structural study of complexes containing activating KIRs and its ligands, many details remain ambiguous.…”

“…A series of peptides derived from these viruses were identified, such as LNPSVAATL (pLNP, from HCV) and IVDLMCHATF (pIVD, from dengue virus and Zika virus). These peptides were used as a naked DNA vaccine to immunize KIR transgenic mice and elicit a specific anti-tumourassociated antigen response [45]. However, the specific recognition mechanism of KIR2DS2 to the pHLA is not clear.…”