Salmonella Typhimurium infection drives NK cell loss and conversion to ILC1-like cells, and CIS inhibition enhances antibacterial immunity

Abstract

Immunotherapy has revolutionized cancer therapy by reactivating tumor-resident cytotoxic lymphocytes. More recently, immunotherapy has emerged to restore immunity against infectious agents, including bacterial infections. Immunotherapy primarily targets inhibitory pathways in tumor-resident T cells, however interest in other effector populations, such as natural killer (NK) cells, is growing. We have previously discovered that NK cell metabolism, proliferation, and activation can be neutralized through the TGF-β immunosuppressive pathway by inducing plasticity of NK cells and differentiation into ILC1-like subsets. NK cells are also regulated through cytokine-inducible SH2-containing protein (CIS), which is induced by IL-15 and is a potent intracellular checkpoint suppressing NK cell survival and function. Targeting these two distinct pathways to restore NK cell function has shown promise is cancer models, but their application in bacterial infection remains unknown. Here, we investigate whether enhancement of NK cell function can improve anti-bacterial immunity, using Salmonella Typhimurium as a model. We identified conversion of NK cells to ILC1-like for the first time in the context of bacterial infection, however TGF-β signaling was curiously redundant in this plasticity. Future work should focus on identifying drivers of ILC1 plasticity and its functional implication in bacterial infection models. We further describe that CIS-deficient mice displayed enhanced pro-inflammatory function and dramatically enhanced anti-infection immunity. Inhibition of CIS may present as a viable therapeutic option to enhance immunity towards bacterial infection.