Memory NK Cells Research Articles

Overview of Memory NK Cells in Viral Infections: Possible Role in SARS-CoV-2 Infection

NK cells have usually been defined as cells of the innate immune system, although they are also involved in adaptative responses. These cells belong to the innate lymphocyte cells (ILC) family. They remove unwanted cells, tumoral cells and pathogens. NK cells are essential for viral infection clearance and are involved in tolerogenic responses depending on the dynamic balance of the repertoire of activating and inhibitory receptors. NK plasticity is crucial for tissue function and vigilant immune responses. They directly eliminate virus-infected cells by recognising viral protein antigens using a non-MHC dependent mechanism, recognising viral glycan structures and antigens by NCR family receptors, inducing apoptosis by Fas-Fas ligand interaction, and killing cells by antibody-dependent cell cytotoxicity via the FcγIII receptor. Activating receptors are responsible for the clearance of virally infected cells, while inhibitory KIR receptor activation impairs NK responses and facilitates virus escape. Effective NK memory cells have been described and characterised by a low NKG2A and high NKG2C or NKG2D expression. NK cells have also been used in cell therapy. In SARS-CoV-2 infection, several contradicting reports about the role of NK cells have been published. A careful analysis of the current data and possible implications will be discussed.

NK and CD8+ T cell phenotypes predict onset and control of CMV viremia after kidney transplant.

CMV causes mostly asymptomatic but lifelong infection. Primary infection or reactivation in immunocompromised individuals can be life-threatening. CMV viremia often occurs in solid organ transplant recipients and associates with decreased graft survival and higher mortality. Furthering understanding of impaired immunity that allows CMV reactivation is critical to guiding antiviral therapy and examining the effect of CMV on solid organ transplant outcomes. This study characterized longitudinal immune responses to CMV in 31 kidney transplant recipients with CMV viremia and matched, nonviremic recipients. Recipients were sampled 3 and 12 months after transplant, with additional samples 1 week and 1 month after viremia. PBMCs were stained for NK and T cell markers. PBMC transcriptomes were characterized by RNA-Seq. Plasma proteins were quantified by Luminex. CD8+ T cell transcriptomes were characterized by single-cell RNA-Seq. Before viremia, patients had high levels of IL-15 with concurrent expansion of immature CD56bright NK cells. After viremia, mature CD56dim NK cells and CD28–CD8+ T cells upregulating inhibitory and NK-associated receptors were expanded. Memory NK cells and NK-like CD28–CD8+ T cells were associated with control of viremia. These findings suggest that signatures of innate activation may be prognostic for CMV reactivation after transplant, while CD8+ T cell functionality is critical for effective control of CMV.

Target modulation and pharmacokinetics/pharmacodynamics translation of the BTK inhibitor poseltinib for model-informed phase II dose selection

The selective Bruton tyrosine kinase (BTK) inhibitor poseltinib has been shown to inhibit the BCR signal transduction pathway and cytokine production in B cells (Park et al.Arthritis Res. Ther.18, 91, https://doi.org/10.1186/s13075-016-0988-z, 2016). This study describes the translation of nonclinical research studies to a phase I clinical trial in healthy volunteers in which pharmacokinetics (PKs) and pharmacodynamics (PDs) were evaluated for dose determination. The BTK protein kinase inhibitory effects of poseltinib in human peripheral blood mononuclear cells (PBMCs) and in rats with collagen-induced arthritis (CIA) were evaluated. High-dimensional phosphorylation analysis was conducted on human immune cells such as B cells, CD8 + memory cells, CD4 + memory cells, NK cells, neutrophils, and monocytes, to map the impact of poseltinib on BTK/PLC and AKT signaling pathways. PK and PD profiles were evaluated in a first-in-human study in healthy donors, and a PK/PD model was established based on BTK occupancy. Poseltinib bound to the BTK protein and modulated BTK phosphorylation in human PBMCs. High-dimensional phosphorylation analysis of 94 nodes showed that poseltinib had the highest impact on anti-IgM + CD40L stimulated B cells, however, lower impacts on anti-CD3/CD-28 stimulated T cells, IL-2 stimulated CD4 + T cells and NK cells, M-CSF stimulated monocytes, or LPS-induced granulocytes. In anti-IgM + CD40L stimulated B cells, poseltinib inhibited the phosphorylation of BTK, AKT, and PLCγ2. Moreover, poseltinib dose dependently improved arthritis disease severity in CIA rat model. In a clinical phase I trial for healthy volunteers, poseltinib exhibited dose-dependent and persistent BTK occupancy in PBMCs of all poseltinib-administrated patients in the study. More than 80% of BTK occupancy at 40 mg dosing was maintained for up to 48 h after the first dose. A first-in-human healthy volunteer study of poseltinib established target engagement with circulating BTK protein. Desirable PK and PD properties were observed, and a modeling approach was used for rational dose selection for subsequent trials. Poseltinib was confirmed as a potential BTK inhibitor for the treatment of autoimmune diseases.Trial registration: This article includes the results of a clinical intervention on human participants [NCT01765478].

Abstract SY30-02: NK cells remember: Engineering NK cell memory-like responses for cancer immunotherapy

Abstract Natural killer (NK) cells are innate lymphoid cells that protect against infection and mediate anti-tumor immune responses. NK cell immunotherapy is a promising cellular therapy approach for leukemia, lymphoma, and other cancers. Multiple laboratories have advanced our understanding of innate NK cell memory and memory-like responses over the past decade, with a unifying definition of enhanced response to re-stimulation after an initial activation event. We identified that human cytokine-induced memory-like (memory) NK cells differentiate after a brief activation with IL-12, IL-15, and IL-18 and mediate enhanced responses against leukemia and other cancer targets. Pre-clinical studies have demonstrated their enhanced anti-tumor potential in vitro, and in vivo in syngeneic murine models and human xenografts. We translated this concept into a first-in-human clinical trial that demonstrated safe adoptive transfer of donor memory NK cells for patients with relapsed or refractory acute myeloid leukemia (AML) resulting in complete remissions. Correlative mass cytometry from this phase 1 study revealed the memory NK cell multidimensional phenotype and identified NKG2A as a major checkpoint for memory NK cell response to AML. Additional clinical trials of donor memory NK cells the HCT setting have demonstrated safety and anti-leukemia activity the immune compatible setting and has provided insights into persistence. Memory NK cells functionally persist for more than 60 days with a unique multidimensional phenotype in two clinical trials in leukemia patients. Further, CITE-seq single cell profiling reveals a unique memory NK cell transcriptomic signature. We have also developed approaches to gene edit and engineer memory-like NK cells with chimeric antigen receptors, expanding the spectrum of cancers for memory-like NK cellular therapy. CAR memory NK cells exhibit enhanced responses, compared with CAR conventional NK cells. Further, pairing with tumor targeting monoclonal antibodies can result in CAR-like responses via CD16/FcγRIIIa, providing additional activating signals that direct memory NK cell response. These studies identify a promising memory NK cell platform for cancer immunotherapy and highlight the importance of correlative studies during clinical trials to advance our understanding of human immunology. Citation Format: Todd A. Fehniger. NK cells remember: Engineering NK cell memory-like responses for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr SY30-02.

Immunocartography: Charting vaccine-driven immunity by applying single cell proteomics to an in vitro human model

The ability to measure immunomodulatory effects of a vaccine is crucial for novel vaccine design. While traditional animal models have been effective, a better understanding of the response in humans to new vaccines in pre-clinical development is critical for advancement to clinical trials. A translational methodology that can capture the complexity of a vaccine-driven response in a human model, which does not require human exposure, is needed. Here we have designed a platform that uses fresh human whole blood as a key component to study the adaptive immune memory response to vaccine formulations. The response is monitored by high-parameter single cell analysis using mass cytometry (Helios, CyTOF System), allowing for a rapid, in-depth characterization of antigen specific proliferation and expansion of preexisting memory T cells in concert with an innate adjuvant-driven response. In this work we demonstrate the capability of this platform to characterize biologically relevant changes in the cellular response across memory T-cells, B cells, monocytes, and NK cells, at an unprecedented level of detail. This approach that we call Immunocartography has the potential to transform the way new vaccines can be assessed before and throughout clinical development.

Phenotypic and Functional Characteristics of a Novel Influenza Virus Hemagglutinin-Specific Memory NK Cell.

Immune memory represents the most efficient defense against invasion and transmission of infectious pathogens. In contrast to memory T and B cells, the roles of innate immunity in recall responses remain inconclusive. In this study, we identified a novel mouse spleen NK cell subset expressing NKp46 and NKG2A induced by intranasal influenza virus infection. These memory NK cells specifically recognize N-linked glycosylation sites on influenza hemagglutinin (HA) protein. Different from memory-like NK cells reported previously, these NKp46+ NKG2A+ memory NK cells exhibited HA-specific silence of cytotoxicity but increase of gamma interferon (IFN-γ) response against influenza virus-infected cells, which could be reversed by pifithrin-μ, a p53-heat shock protein 70 (HSP70) signaling inhibitor. During recall responses, splenic NKp46+ NKG2A+ NK cells were recruited to infected lung and modulated viral clearance of virus and CD8+ T cell distribution, resulting in improved clinical outcomes. This long-lived NK memory bridges innate and adaptive immune memory response and promotes the homeostasis of local environment during recall response.IMPORTANCE In this study, we demonstrate a novel hemagglutinin (HA)-specific NKp46+ NKG2A+ NK cell subset induced by influenza A virus infection. These memory NK cells show virus-specific decreased cytotoxicity and increased gamma interferon (IFN-γ) on reencountering the same influenza virus antigen. In addition, they modulate host recall responses and CD8 T cell distribution, thus bridging the innate immune and adaptive immune responses during influenza virus infection.

A phase 1 study of RTX-321, an engineered red blood cell as an artificial antigen-presenting cell expressing HLA-A*02 with the HPV-16 E7 peptide and 4-1BB ligand with membrane-bound IL-12 for the treatment of HPV 16-positive cancers.

TPS2664 Background: High-risk strains of HPV (HPV 16/18) have been associated with the development of multiple cancers, and the associated viral antigens are validated targets from immunotherapy approaches. We engineered red blood cells into allogeneic, off-the-shelf, artificial antigen-presenting cells (aAPCs) that express a human papillomavirus (HPV) 16 E7 peptide bound to human leukocyte antigen (HLA)-A*02:01, the costimulatory molecule 4-1BB ligand (L), and the cytokine interleukin (IL)-12 on the cell surface. This aAPC, RTX-321, activated HPV specific T-cells and promoted effector function in vitro. In animal models using a murine surrogate system, this aAPC approach resulted in robust antigen-specific T-cell expansion, NK cell expansion, tumor control, memory formation and antigen spreading, which led to a broad and robust antitumor immune response . The presence of 4-1BBL and IL-12 induced minimal toxicities in these models due to restriction of the biodistribution of the aAPC to the vasculature and spleen. RTX-321 is a potential in vivo cellular immunotherapy for treating HPV 16-positive cancers including cervical, head and neck and anal cancers. Methods: The RTX-321-01 study is a phase 1 multi-center, dose-escalation study of RTX-321 administered intravenously every 3 weeks in HLA-A*02:01-positive patients with relapsed or refractory HPV 16-positive cancers of the cervix or anal canal, or squamous cell cancers of the head and neck (HNSCC). Patients with cervical cancer or HNSCC will undergo testing for the presence of the HPV 16 virus or provide confirmation from archival tumor tissue prior to enrollment. Patients with anal cancer will not be required to have prospective determination of HPV 16-positive status prior to enrollment given the high incidence in this indication (approximately 80-85 percent of anal cancers). Approximately 18 patients will be enrolled across dose level cohorts to identify the recommended phase 2 dose (RP2D) of RTX-321, followed by RP2D expansion cohorts in specific indications. The starting dose is 1 billion (1x109) cells administered intravenously every 3 weeks (Q3W) and the dose will escalate by half-log increments, following a Bayesian logarithmic regression model (BLRM) with overdose control. Translational studies will investigate the activation and expansion of HPV16 E7 antigen-specific responses as well as broad innate and adaptive responses in multiple peripheral blood samples over the first 3 cycles of therapy as well as in optional paired tumor biopsies. At this time, the study is open and enrolling patients in the first dose escalation cohort (NCT04672980). Clinical trial information: NCT04672980.

Harnessing CD16-Mediated NK Cell Functions to Enhance Therapeutic Efficacy of Tumor-Targeting mAbs.

Simple SummaryNatural Killer (NK) cells play a major role in cancer immunotherapy based on tumor-targeting mAbs. NK cell-mediated tumor cell killing and cytokine secretion are powerfully stimulated upon interaction with IgG-opsonized tumor cells, through the aggregation of FcγRIIIA/CD16 IgG receptor. Advances in basic and translational NK cell biology have led to the development of strategies that, by improving mAb-dependent antitumor responses, may overcome the current limitations of antibody therapy attributable to tolerance, immunosuppressive microenvironment, and genotypic factors. This review provides an overview of the immunotherapeutic strategies being pursued to improve the efficacy of mAb-induced NK antitumor activity. The exploitation of antibody combinations, antibody-based molecules, used alone or combined with adoptive NK cell therapy, will be uncovered. Within the landscape of NK cell heterogeneity, we stress the role of memory NK cells as promising effectors in the next generation of immunotherapy with the aim to obtain long-lasting tumor control.Natural killer (NK) cells hold a pivotal role in tumor-targeting monoclonal antibody (mAb)-based activity due to the expression of CD16, the low-affinity receptor for IgG. Indeed, beyond exerting cytotoxic function, activated NK cells also produce an array of cytokines and chemokines, through which they interface with and potentiate adaptive immune responses. Thus, CD16-activated NK cells can concur to mAb-dependent “vaccinal effect”, i.e., the development of antigen-specific responses, which may be highly relevant in maintaining long-term protection of treated patients. On this basis, the review will focus on strategies aimed at potentiating NK cell-mediated antitumor functions in tumor-targeting mAb-based regimens, represented by (a) mAb manipulation strategies, aimed at augmenting recruitment and efficacy of NK cells, such as Fc-engineering, and the design of bi- or trispecific NK cell engagers and (b) the possible exploitation of memory NK cells, whose distinctive characteristics (enhanced responsiveness to CD16 engagement, longevity, and intrinsic resistance to the immunosuppressive microenvironment) may maximize therapeutic mAb antitumor efficacy.

Clinical Relevance of CD4 Cytotoxic T Cells in High-Risk Neuroblastoma.

Neuroblastoma is the most common extracranial childhood solid tumor. The majority of high-risk neuroblastoma is resistant/refractory to the current high intensity therapy, and the survival of these patients remains poor for the last three decades. To effectively treat these extremely unfavorable neuroblastomas, innovative immunotherapy approaches would be the most promising. In this article, we discuss the identity of tumor-infiltrating effector cells and immunosuppressive cells in high-risk neuroblastoma. Neuroblastoma is unique in that it expresses little or no classical HLA Class I and II. In contrast, high-risk neuroblastomas express the stress-responsive non-classical Class I, HLA-E molecule. HLA-E is the ligand of activating receptors NKG2C/E that are expressed on memory NK cells, CD8+T cells and CD4 CTLs. By examining a comprehensive RNA-seq gene expression dataset, we detected relatively high levels of CD4 expression in high-risk neuroblastoma tissues. The majority of CD4+ cells were CD3+, and thus they were likely tumor-associated CD4+T cells. In addition, high-level of both CD4 and NKG2C/E expression was associated with prolonged survival of the high-risk neuroblastoma patients, but CD8 levels were not, further suggesting that the CD4+ NKG2C/E+ T cells or CD4 CTL conferred cytotoxicity against the neuroblastoma cells. However, this T cell mediated- “protective effect” declined over time, in part due to the progressive formation of immunosuppressive tumor microenvironment. These observations suggest that to improve survival of high-risk neuroblastoma patients, it is essential to gain insights into how to enhance CD4 CTL cytotoxicity and control the immunosuppressive tumor microenvironment during the course of the disease.

Human NK cells: From development to effector functions.

NK cells are the major lymphocyte subset of the innate immune system that mediates antiviral and anti-tumor responses. It is well established that they develop mechanisms to distinguish self from non-self during the process of NK cell education. Unlike T and B cells, natural killer cells lack clonotypic receptors and are activated after recognizing their target via germline-encoded receptors through natural cytotoxicity, cytokine stimulation, and Ab-dependent cellular cytotoxicity. Subsequently, they utilize cytotoxic granules, death receptor ligands, and cytokines to perform their effector functions. In this review, we provide a general overview of human NK cells, as opposed to murine NK cells, discussing their ontogeny, maturation, receptor diversity, types of responses, and effector functions. Furthermore, we also describe recent advances in human NK cell biology, including tissue-resident NK cell populations, NK cell memory, and novel approaches used to target NK cells in cancer immunotherapy.

Virus-specific NK cell memory.

NK cells express a limited number of germline-encoded receptors that identify infected or transformed cells, eliciting cytotoxicity, effector cytokine production, and in some circumstances clonal proliferation and memory. To maximize the functional diversity of NK cells, the array and expression level of surface receptors vary between individual NK cell "clones" in mice and humans. Cytomegalovirus infection in both species can expand a population of NK cells expressing receptors critical to the clearance of infected cells and generate a long-lived memory pool capable of targeting future infection with greater efficacy. Here, we discuss the pathways and factors that regulate the generation and maintenance of effector and memory NK cells and propose how this understanding may be harnessed therapeutically.

Divergent Role for STAT5 in the Adaptive Responses of Natural Killer Cells

SUMMARYNatural killer (NK) cells are innate lymphocytes with the capacity to elicit adaptive features, including clonal expansion and immunological memory. Because signal transducer and activator of transcription 5 (STAT5) is essential for NK cell development, the roles of this transcription factor and its upstream cytokines interleukin-2 (IL-2) and IL-15 during infection have not been carefully investigated. In this study, we investigate how STAT5 regulates transcription during viral infection. We demonstrate that STAT5 is induced in NK cells by IL-12 and STAT4 early after infection and that partial STAT5 deficiency results in a defective capacity of NK cells to generate long-lived memory cells. Furthermore, we find a functional dichotomy of IL-2 and IL-15 signaling outputs during viral infection, whereby both cytokines drive clonal expansion, but only IL-15 is required for memory NK cell survival. We thus highlight a role for STAT5 signaling in promoting an optimal anti-viral NK cell response.

Hepatitis C Virus (HCV) Eradication With Interferon-Free Direct-Acting Antiviral-Based Therapy Results in KLRG1+ HCV-Specific Memory Natural Killer Cells.

Direct acting antiviral therapies rapidly clear chronic hepatitis C virus (HCV) infection and restore natural killer (NK) cell function. We investigated NK-cell memory formation following HCV clearance by examining NK-cell phenotype and responses from control and chronic HCV patients before and after therapy following sustained virologic response at 12 weeks post therapy (SVR12). NK-cell phenotype at SVR12 differed significantly from paired pretreatment samples, with an increase in maturation markers CD16, CD57, and KLRG1. HCV patients possessed stronger cytotoxic responses against HCV-infected cells as compared to healthy controls; a response that further increased following SVR12. The antigen-specific response was mediated by KLRG1+ NK cells, as demonstrated by increased degranulation and proliferation in response to HCV antigen only. Our data suggest that KLRG1+ HCV-specific memory NK cells develop following viral infection, providing insight into their role in HCV clearance and relevance with regard to vaccine design.

A Central Role for Ly49 Receptors in NK Cell Memory.

In the past decade, the study of NK cells was transformed by the discovery of three ways these "innate" immune cells display adaptive immune behavior, including the ability to form long-lasting, Ag-specific memories of a wide variety of immunogens. In this review, we examine these types of NK cell memory, highlighting their unique features and underlying similarities. We explore those similarities in depth, focusing on the role that Ly49 receptors play in various types of NK cell memory. From this Ly49 dependency, we will build a model by which we understand the three types of NK cell memory as aspects of what is ultimately the same adaptive immune process, rather than separate facets of NK cell biology. We hope that a defined model for NK cell memory will empower collaboration between researchers of these three fields to further our understanding of this surprising and clinically promising immune response.

The IRE1 endoplasmic reticulum stress sensor activates natural killer cell immunity and promotes natural killer cell memory by regulating c-Myc and mitochondrial respiration

Abstract Natural killer (NK) cells are critical mediators of host immunity to pathogens. Though historically being considered as a part of the innate immune system, NK cells exhibit adaptive features and can ‘remember’ stimuli like inflammation or viral infection and hence are capable of responding more robustly upon re-encountering the stimulation. Successful design of an NK cell-based therapy would ideally rely on harnessing NK cell memory, the key drivers and regulators of which remain poorly understood. Here, we demonstrate that the endoplasmic reticulum stress sensor IRE1α and its substrate transcription factor XBP1 drive NK cell responses against viral infection and tumors in vivo. IRE1α-XBP1 were essential for expansion of activated mouse and human NK cells and are situated downstream of the mTOR pathway. Transcriptome and chromatin immunoprecipitation analysis revealed c-Myc as a new and direct downstream target of XBP1 for regulation of NK cell proliferation. NK cells with c-Myc haploinsufficency phenocopied IRE1α deficiency, while c-Myc overexpression largely rescued the proliferation defect in IRE1α−/− NK cells. Like c-Myc, IRE1α also promotes oxidative phosphorylation in NK cells. Combined, our study identifies an IRE1α-XBP1-cMyc axis in NK cell immunity; and based on this work, we are currently investigating the role of IRE1 in NK cell memory using novel transgenic mouse models and small molecule drug treatment in primary human cells. We are also evaluating the therapeutic benefit of manipulating IRE1 function in CAR-NK cells to treat cancer. Our ongoing study should advance the current knowledge of NK cell memory and also open new opportunities in cancer therapy for patients with otherwise extremely poor prognoses.

β-1,3-glucan induces natural killer cell memory-like immunity

Abstract Natural killer (NK) cells are considered innate lymphocytes that are able to kill pathogenic microorganisms, including bacteria, parasites and fungi as well as virus-infected cells and tumor cells without prior stimulation. Recent studies suggest that they possess a memory-like property to previously encountered pathogens (e.g., cytomegalovirus). We showed that NK cells directly kill Cryptococcus and Candida, which are fatal opportunistic fungi often infecting immunocompromised individuals. We determined that NKp30 is the activating pattern recognition receptor that mediates NK cell killing of these fungi, and that β-1,3-glucan is the ligand for NKp30. Interestingly, we found that soluble β-1,3-glucan enhanced NK cell killing of C. neoformans and C. albicans. Since humans and animals are exposed to β-1,3-glucan through inhalation of components of the cell wall of microbes or consumption of dietary grains, we asked whether isolated β-1,3-glucan plays a role in shaping NK cell immunity. To determine whether β-1,3-glucan induces a training or memory effect, YT cells, an NK cell line, were treated for 24 hours with laminarin or Saccharomyces β-1,3-glucan and cultured for various times. After an initial period of enhanced C. neoformans killing, killing was reduced to the untreated level on the second week after the initial treatment. However, when cryptococcal killing was assessed on the fourth week, a much greater killing was observed compared to the enhanced killing. This suggests that a recall immune response was induced. We conclude that β-1,3-glucan may induce NK cell memory- like immunity.

Memory and Memory-Like NK Cell Responses to Microbial Pathogens.

NK cells are cytotoxic lymphocytes that provide systemic defense against pathogens and malignancy. Although historically considered cells of the innate immune system, NK cells are now known to be capable of memory or memory-like immune responses in certain settings. Memory NK responses were initially reported over a decade ago in studies involving mouse models of cytomegalovirus infection and delayed-type hypersensitivity reactions to chemical haptens and viral antigens. Since then, a growing body of literature suggests that memory or memory-like NK cell responses may occur in a broader range of immunological settings, including in response to various viral and bacterial infections, and some immunization protocols. Memory-like NK cell responses have also now been reported in humans and non-human primates. Here, we summarize recent studies demonstrating memory or memory-like responses by NK cells in settings of infection and immunization against infectious agents.

What Defines NK Cell Functional Fate: Phenotype or Metabolism?

NK cells are capable of an array of functions that range widely from their classic anti-tumor and anti-viral cytotoxic effector functions, to their critical regulatory roles in controlling inflammatory immune responses and promoting tissue growth. However, the mechanisms that polarize NK cells to these distinct and opposing functions are incompletely understood. NK cell functional subsets are primarily identified and studied based on phenotype, which has served as an accessible means for profiling NK cells and does offer information on NK cell activation state. However, inconsistencies have emerged in using classic phenotypes to inform function, which raise the questions: Can phenotype in fact define NK cell functional fate? What factors do profile and drive NK cell fate? In other immune cells, cell metabolism has been shown to critically determine subset polarization. There is a growing body of evidence that cell metabolism is integral to NK cell effector functions. Glucose-driven glycolysis and oxidative metabolism have been shown to drive classic NK cell anti-tumor and anti-viral effector functions. Recent studies have uncovered a critical role for metabolism in NK cell development, education, and memory generation. In this review, we will draw on the evidence to date to investigate the relationship between NK cell phenotype, metabolism, and functional fate. We explore a paradigm in which the differential activity of metabolic pathways within NK cells produce distinct metabolic fingerprints that comprehensively distinguish and drive the range of NK cell functional abilities. We will discuss future areas of study that are needed to develop and test this paradigm and suggest strategies to efficiently profile NK cells based on metabolism. Given the emerging role of metabolism in driving NK cell fates, profiling and modulating NK cell metabolism holds profound therapeutic potential to tune inflammatory and regulatory NK cell responses to treat disease.

Tissue driven influences on human NK cell development, function and residence

Abstract Natural killer (NK) cells are innate immune cells with the inherent ability to kill tumor and virus infected cells without any prior priming. Recent studies have demonstrated the ability of NK cells to develop adaptive memory and tissue residence. However, our understanding of human NK cells in tissues and their site-specific properties is limited. Here we use our unique tissue resource established in collaboration with LiveOnNY to elucidate the diversity of human NK cell phenotypic subsets, functional profile and transcriptional signatures in non-mucosal and mucosal tissue sites. We identified tissue-specific patterns of NK cell maturation and show that NK cell subset (immature and mature) and memory NK cell distribution is a function of tissue site which is not affected by age. Our results also show that while NK cells from different tissue sites express similar levels of granzyme B, NK cell antibody-dependent cellular cytotoxicity response and cytokine driven activation may be influenced by tissue site. Whole transcriptome profiling of NK cell subsets revealed that mature NK cells from all the sites (blood, bone marrow, spleen, lung and LN) have very similar transcriptional profiles. Interestingly, immature NK cells from all tissue sites have very different transcriptional profiles compared to their blood counterpart and are enriched for tissue resident memory T cell transcriptional signature. Furthermore, we show that immature NK cells show site-specific expression patterns of tissue residence surface markers. Overall, our data demonstrates the effects of tissue microenvironment on the developmental and function potential of tissue NK cells and provides insight into the development of future NK cell mediated immunotherapies.

Adaptive NK cell responses in HIV/SIV infections: A roadmap to cell-based therapeutics?

NK cells play a critical role in antiviral and antitumor responses. Although current NK cell immune therapies have focused primarily on cancer biology, many of these advances can be readily applied to target HIV/simian immunodeficiency virus (SIV)-infected cells. Promising developments include recent reports that CAR NK cells are capable of targeted responses while producing less off-target and toxic side effects than are associated with CAR T cell therapies. Further, CAR NK cells derived from inducible pluripotent stem cells or cell lines may allow for more rapid "off-the-shelf" access. Other work investigating the IL-15 superagonist ALT-803 (now N803) may also provide a recourse for enhancing NK cell responses in the context of the immunosuppressive and inflammatory environment of chronic HIV/SIV infections, leading to enhanced control of viremia. With a broader acceptance of research supporting adaptive functions in NK cells it is likely that novel immunotherapeutics and vaccine modalities will aim to generate virus-specific memory NK cells. In doing so, better targeted NK cell responses against virus-infected cells may usher in a new era of NK cell-tuned immune therapy.