Characterization of memory Natural Killer cell responses and their application in a cell-targeted cancer immunotherapy

Abstract

Numerous research studies have underscored the adaptive immune characteristics exhibited by NK cells in response to various stimuli, ranging from cytokines to viral ligands and haptens. This has fueled considerable interest in leveraging NK cell memory for cancer immunotherapies. Our study adds to this understanding by demonstrating that NK cells primed against tumour antigens can evoke robust and enduring anti-tumour responses in Rag1-/- mice devoid of adaptive T and B cells. We further identified a selective expansion of NK1.1+ cells within tumours and livers, with the latter being suggested as a niche for memory NK cells in existing literature. Through scRNA-seq analysis, we delineated at least four distinct tumour-infiltrating NK1.1+ NKp46+ cell populations in T & B cell deficient mice, with this heterogeneous pool of NK cells expanding notably in tumours from R9F-vaccinated Rag1-/- mice.Moreover, our investigation pinpointed the essential role of class-I MHC Ly49 receptors, particularly Ly49C/I, in mediating NK cell-mediated adaptive responses in mice. By transgenically introducing the inhibitory Ly49I receptor into mice lacking either the entire Ly49 family or Ly49C/I, we confirmed the sufficiency of this receptor in mediating NK-cell adaptive responses. Our study showcases the high antigen specificity of these NK cell-mediated memory responses both in vivo and in vitro, enabling memory NK cells to discern distinct antigens presented by target cells. We introduced an innovative approach to capture antigen-specific memory NK cells using MHC-I/peptide dextramer complexes in the livers and tumours of R9F-vaccinated, tumour-bearing Rag1-/- mice. Notably, we demonstrated that the memory effector functions of these dextramer+ tumour-infiltrating NK cells can be transferred to naïve recipients, resulting in superior antitumour responses compared to conventional dextramer- NK cells. Finally, our findings highlight the presence of antigen-specific NK cells even in the context of the adaptive immune system, underscoring the biological relevance of the observed memory responses in Rag1-/- mice.