Resting natural killer cell homeostasis relies on tryptophan/NAD+^{+} metabolism and HIF-1α

Natural killer (NK) cells are forced to cope with different oxygen environments even under resting conditions. The adaptation to low oxygen is regulated by oxygen-sensitive transcription factors, the hypoxia-inducible factors (HIFs). The function of HIFs for NK cell activation and metabolic rewiring remains controversial. Activated NK cells are predominantly glycolytic, but the metabolic programs that ensure the maintenance of resting NK cells are enigmatic. By combining in situ metabolomic and transcriptomic analyses in resting murine NK cells, our study defines HIF-1α as a regulator of tryptophan metabolism and cellular nicotinamide adenine dinucleotide (NAD$^{+}$ ) levels. The HIF-1α/NAD$^{+}$ axis prevents ROS production during oxidative phosphorylation (OxPhos) and thereby blocks DNA damage and NK cell apoptosis under steady-state conditions. In contrast, in activated NK cells under hypoxia, HIF-1α is required for glycolysis, and forced HIF-1α expression boosts glycolysis and NK cell performance in vitro and in vivo. Our data highlight two distinct pathways by which HIF-1α interferes with NK cell metabolism. While HIF-1α-driven glycolysis is essential for NK cell activation, resting NK cell homeostasis relies on HIF-1α-dependent tryptophan/NAD$^{+}$ metabolism

Rôle de la nucléoprotéine des Morbillivirus dans la modulation de la réponse immunitaire

L infection induite par le virus de la rougeole est associée à un intriguant paradoxe immunologique, caractérisé par une réponse immunitaire très efficace, conduisant à l élimination du virus et à une immunité à vie contre toute réinfection, mais également l induction d une immunosuppression transitoire mais sévère. De plus un nombre grandissant d études suggère que ce phénomène serait retrouvé pour l ensemble des infections Morbilleuses. De récents travaux menés sur le virus de la rougeole ont mis en évidence un rôle direct des protéines virales dans l affaiblissement des défenses immunitaires de l hôte. Parmi ces protéines, la nucléoprotéine (N) induit une réponse immunitaire spécifique massive et précoce pour l ensemble des Morbillivirus, tandis que la N du virus de la rougeole est également capable d induire une immunosuppression chez l homme et la souris. L objectif de ce travail fut de préciser et d étudier les mécanismes cellulaires et moléculaires gouvernant cette modulation de la réponse immunitaire liée à la N. Dans un premier temps à l aide des N recombinantes du virus de la rougeole, du virus de la maladie de Carré, du virus de la peste bovine et du virus de la peste des petits ruminants, nous avons mis en évidence que l immunosuppression induite par cette protéine serait un mécanisme conservé par l ensemble des virus de ce genre, soulignant donc son importance. De plus, en collaboration avec le laboratoire du Dr Mallat, il a été montré que cette propriété immunosuppressive de la N permet de limiter la progression de l athérosclérose dans un modèle de souris développant spontanément cette pathologie. Enfin, en collaboration avec l équipe du Dr Kaiserlian, il a été mis en évidence que les propriétés immunostimulatrices de la N du virus de la rougeole sont gouvernées par des mécanismes dépendant de la molécule MyD88. Ces résultats montrent donc que les mécanismes d immunostimulation et d immunosuppression induit par la N sont clairement distincts et sont respectivement dépendant de la molécule MyD88 d une part, et des récepteurs RFcg d autre part. L ensemble de ces résultats suggèrent donc que la N est au cœur du paradoxe immunologique induit lors de l infection par le virus de la rougeole et vraisemblablement de l ensemble des infections morbilleuses. Par ailleurs, ils mettent également en évidence la dissociation des mécanismes qui le gouvernent. Enfin, ils suggèrent que ces protéines ou des fragments de ces protéines, pourraient avoir différentes applications thérapeutiques potentielles.Measles virus infection is associated with an intriguing immunological paradox, characterized by a strong specific immune response, leading to virus clearance and lifelong immunity against reinfection, but also by the induction of a transient but profound immune suppression. Moreover, a growing numbers of studies suggest that this phenomenon may be found for all Morbillivirus infections. Recent works on measles virus highlight a direct role of viral proteins in the suppression of immune defences. Among these proteins, the nucleoprotein (N) induces a massive and fast specific immune response for all Morbilliviruses, although measles virus N is able to induce an immune suppression in humans and mice. The aim of this work was to study the cellular and molecular mechanisms governing this immune paradox linked to N. First, with help of recombinant N from measles virus, Canine distemper Virus, Rinderpest virus and peste des petits ruminants virus, we present evidences that N-mediated immune suppression may be a conserved mechanism among Morbillivirus, highlighting its important role. Moreover, in collaboration with Dr Mallat, it has been shown that this immunosuppressive property of N allowed to limits atherosclerosis progression in a mice model which spontaneously develop this pathology. Finally, in collaboration with Dr Kaiserlian, it has been shown that immunostimulatory and immunosuppressive properties of measles N are governed by clearly distinct mechanisms, respectively dependant of the MyD88 molecule on one side, and by Fcg receptors on the other side. Altogether, these results suggest that N has a central role in the immunological paradox induced during measles infection and presumably for all Morbilliviruses infections. Furthermore, they highlight the dissociation between the mechanisms leading to it. Finally, they suggest that proteins or peptides derived from them may have multiple potential therapeutic applications.LYON-ENS Sciences (693872304) / SudocSudocFranceF

Highly Specialized Role of Forkhead Box O Transcription Factors in the Immune System

Recent studies have highlighted a fundamental role for Forkhead box O (Foxo) transcription factors in immune system homeostasis. Initial reports designed to dissect function of individual Foxo isoforms in the immune system were based on in vitro overexpression systems, and these experiments suggested that Foxo1 and Foxo3 are important for growth factor withdrawal-induced cell death. Moreover, Foxo factors importantly regulate basic cell cycle progression, and so the implication was that these factors may control lymphocyte homeostasis, including a critical function in the termination and resolution of an immune response. Most recently, cell-type-specific loss mutants for the different Foxo isoforms have revealed unexpected and highly specialized functions in the control of multiple cell types in the immune system, but they have yet to reveal a role in cell death or proliferation. This review will focus on the recent advances made in the understanding of the many ways that Foxo factors regulate the immune system, including a discussion of how the specialized versus redundant functions of Foxo transcription factors impact immune system homeostasis. Antioxid. Redox Signal. 14, 663–674

Natural killer cell immunotherapies against cancer: checkpoint inhibitors and more

International audienceAfter many years of research, recent advances have shed new light on the role of the immune system in advanced-stage cancer. Various types of immune cells may be useful for therapeutic purposes, along with chemical molecules and engineered monoclonal antibodies. The immune effectors suitable for manipulation for adoptive transfer or drug targeting in vivo include natural killer (NK) cells. These cells are of particular interest because they are tightly regulated by an array of inhibitory and activating receptors, enabling them to kill tumor cells while sparing normal cells. New therapeutic antibodies blocking the interactions of inhibitory receptors (immune checkpoint inhibitors, ICI) with their ligands have been developed and can potentiate NK cell functions in vivo

Tissue-specific transcriptional profiles and heterogeneity of natural killer cells and group 1 innate lymphoid cells

International audienceNatural killer (NK) cells and type 1 innate lymphoid cells (ILC1s) are populations of non-T, non-B lymphocytes in peripheral tissues. Although NK and ILC1 subsets have been described, their identification and characteristics remain unclear. We performed single-cell RNA sequencing and CITE-seq to explore NK and ILC1 heterogeneity between tissues. We observed that although NK1 and NK2 subsets are conserved in spleen and liver, ILC1s are heterogeneous across tissues. We identified sets of genes expressed by related subsets or characterizing unique ILC1 populations in each organ. The syndecan-4 appeared as a marker discriminating murine ILC1 from NK cells across organs. Finally, we revealed that the expressions of EOMES, GZMA, IRF8, JAK1, NKG7, PLEK, PRF1, and ZEB2 define NK cells and that IL7R, LTB, and RGS1 differentiate ILC1s from NK cells in mice and humans. Our data constitute an important resource to improve our understanding of NK-ILC1 origin, phenotype, and biology

Lessons from NK Cell Deficiencies in the Mouse

International audienceSince their discovery in the late 1970s, in vivo studies on mouse natural killer (NK) cell almost entirely relied on the use of depleting antibodies and were associated with significant limitations. More recently, large-scale gene-expression analyses allowed the identification of NKp46 as one of the best markers of NK cells across mammalian species. Since then, NKp46 has been shown to be expressed on other subsets of innate lymphoid cells (ILCs) such as the closely related ILC1 and the mucosa-associated NCR+ ILC3. Based on this marker, several mouse models specifically targeting NKp46-expressing cell have recently been produced. Here, we review recent advances in the generation of models of deficiency in NKp46-expressing cells and their use to address the role of NK cells in immunity, notably on the regulation of adaptive immune responses

NK cells in hypoxic skin mediate a trade-off between wound healing and antibacterial defence

During skin injury, immune response and repair mechanisms have to be coordinated for rapid skin regeneration and the prevention of microbial infections. Natural Killer (NK) cells infiltrate hypoxic skin lesions and Hypoxia-inducible transcription factors (HIFs) mediate adaptation to low oxygen. We demonstrate that mice lacking the Hypoxia-inducible factor (HIF)-1α isoform in NK cells show impaired release of the cytokines Interferon (IFN)-γ and Granulocyte Macrophage - Colony Stimulating Factor (GM-CSF) as part of a blunted immune response. This accelerates skin angiogenesis and wound healing. Despite rapid wound closure, bactericidal activity and the ability to restrict systemic bacterial infection are impaired. Conversely, forced activation of the HIF pathway supports cytokine release and NK cell-mediated antibacterial defence including direct killing of bacteria by NK cells despite delayed wound closure. Our results identify, HIF-1α in NK cells as a nexus that balances antimicrobial defence versus global repair in the skin

Loss of HIF-1α in natural killer cells inhibits tumour growth by stimulating non-productive angiogenesis

Productive angiogenesis, a prerequisite for tumour growth, depends on the balanced release of angiogenic and angiostatic factors by different cell types within hypoxic tumours. Natural killer (NK) cells kill cancer cells and infiltrate hypoxic tumour areas. Cellular adaptation to low oxygen is mediated by Hypoxia-inducible factors (HIFs). We found that deletion of HIF-1α in NK cells inhibited tumour growth despite impaired tumour cell killing. Tumours developing in these conditions were characterised by a high-density network of immature vessels, severe haemorrhage, increased hypoxia, and facilitated metastasis due to non-productive angiogenesis. Loss of HIF-1α in NK cells increased the bioavailability of the major angiogenic cytokine vascular endothelial growth factor (VEGF) by decreasing the infiltration of NK cells that express angiostatic soluble VEGFR-1. In summary, this identifies the hypoxic response in NK cells as an inhibitor of VEGF-driven angiogenesis, yet, this promotes tumour growth by allowing the formation of functionally improved vessels

Immunomodulatory properties of morbillivirus nucleoproteins.

International audienceMorbillivirus infections have been known for a long time to be associated with an acute immunosuppression in their natural hosts. Here, we show that recombinant Morbillivirus nucleoproteins from canine distemper virus, peste-des-petits-ruminants virus, and Rinderpest virus bind B-lymphocytes from dogs, goats, and cattle, respectively, similarly to measles virus nucleoprotein in humans. The use of surface plasmon resonance imaging allowed the real time detection of differential interactions between Morbillivirus nucleoproteins and FcgammaRIIb (CD32). Moreover, those nucleoproteins which bind murine Fcgamma receptor inhibited the inflammatory immune responses in mice in a Fc receptor- dependent manner. In contrast, nucleoprotein from closely related Henipavirus genus, belonging to the Paramyxoviridae family as Morbillivirus, was devoid of capacity either to bind FcgammaRIIb or to inhibit inflammatory response. Altogether, these results suggest that nucleoprotein-FcR interaction is a common mechanism used by different Morbilliviruses to modulate the immune response

Type 1 Innate Lymphoid Cells Limit the Antitumoral Immune Response

International audienceNatural killer (NK) cells are known to be able to kill established tumor cell lines, but important caveats remain regarding their roles in the detection and elimination of developing primary tumors. Using a genetic model of selective ILC1 and NK cell deficiency, we showed that these cells were dispensable for tumor immunosurveillance and immunoediting in the MCA-induced carcinogenesis model. However, we were able to generate primary cell lines derived from MCA-induced tumors with graded sensitivity to NK1.1 + cells (including NK cells and ILC1). This differential sensitivity was associated neither with a modulation of intratumoral NK cell frequency, nor the capacity of tumor cells to activate NK cells. Instead, ILC1 infiltration into the tumor was found to be a critical determinant of NK1.1 + cell-dependent tumor growth. Finally, bulk tumor RNAseq analysis identified a gene expression signature associated with tumor sensitivity to NK1.1 + cells. ILC1 therefore appear to play an active role in inhibiting the antitumoral immune response, prompting to evaluate the differential tumor infiltration of ILC1 and NK cells in patients to optimize the harnessing of immunity in cancer therapies