High dose CD11c-driven IL15 is sufficient to drive NK cell maturation and anti-tumor activity in a trans-presentation independent manner

Nasal administration of recombinant Neospora caninum secreting IL-15/IL-15Rα inhibits metastatic melanoma development in lung

BACKGROUND

Metastases are the leading cause of mortality in many cancer types and lungs are one of the most common sites of metastasis alongside the liver, brain, and bones. In melanoma, 85% of late-stage patients harbor lung metastases. A local administration could enhance the targeting of metastases while limiting the systemic cytotoxicity. Therefore, intranasal administration of immunotherapeutic agents seems to be a promising approach to preferentially target lung metastases and decrease their burden on cancer mortality. From observations that certain microorganisms induce an acute infection of the tumor microenvironment leading to a local reactivating immune response, microbial-mediated immunotherapy is a next-generation field of investigation in which immunotherapies are engineered to overcome immune surveillance and escape from microenvironmental cancer defenses.

METHODS

The goal of our study is to evaluate the potential of the intranasal administration of Neospora caninum in a syngeneic C57BL6 mouse model of B16F10 melanoma lung metastases. It also compares the antitumoral properties of a wild-type N. caninum versus N. caninum secreting human interleukin (IL)-15 fused to the sushi domain of the IL-15 receptor α chain, a potent activator of cellular immune responses.

RESULTS

The treatment of murine lung metastases by intranasal administration of an N. caninum engineered to secrete human IL-15 impairs lung metastases from further progression with only 0,08% of lung surface harboring metastases versus 4,4% in wild-type N. caninum treated mice and 36% in untreated mice. The control of tumor development is associated with a strong increase in numbers, within the lung, of natural killer cells, CD8⁺ T cells and macrophages, up to twofold, fivefold and sixfold, respectively. Analysis of expression levels of CD86 and CD206 on macrophages surface revealed a polarization of these macrophages towards an antitumoral M1 phenotype.

CONCLUSION

Administration of IL-15/IL-15Rα-secreting N. caninum through intranasal administration, a non-invasive route, lend further support to N. caninum-demonstrated clear potential as an effective and safe immunotherapeutic approach for the treatment of metastatic solid cancers, whose existing therapeutic options are scarce. Combination of this armed protozoa with an intranasal route could reinforce the existing therapeutic arsenal against cancer and narrow the spectrum of incurable cancers.

The effects of B-cell-activating factor on the population size, maturation and function of murine natural killer cells

The role of B-cell-activating factor (BAFF) in B-lymphocyte biology has been comprehensively studied, but its contributions to innate immunity remain unclear. Natural killer (NK) cells form the first line of defense against viruses and tumors, and have been shown to be defective in patients with systemic lupus erythematosus (SLE). The link between BAFF and NK cells in the development and progression of SLE remains unstudied. By assessing NK cell numbers in wild-type (WT), BAFF^-/- (BAFF deficient), BAFF-R^-/- (BAFF receptor deficient), TACI^-/- (transmembrane activator and calcium modulator and cyclophilin ligand interactor deficient), BCMA^-/- (B-cell maturation antigen deficient) and BAFF transgenic (Tg) mice, we observed that BAFF signaling through BAFF-R was essential for sustaining NK cell numbers in the spleen. However, according to the cell surface expression of CD27 and CD11b on NK cells, we found that BAFF was dispensable for NK cell maturation. Ex vivo and in vivo models showed that NK cells from BAFF^-/- and BAFF Tg mice produced interferon-γ and killed tumor cells at a level similar to that in WT mice. Finally, we established that NK cells do not express receptors that interact with BAFF in the steady state or in the BAFF Tg mouse model of SLE. Our findings demonstrate that BAFF has an indirect effect on NK cell homeostasis and no effect on NK cell function.

Interleukin-15 and cancer: some solved and many unsolved questions

Soluble interleukin (IL)-15 exists under two forms: as monomer (sIL-15) or as heterodimeric complex in association with sIL-15Rα (sIL-15/IL-15Rα). Both forms have been successfully tested in experimental tumor murine models and are currently undergoing investigation in phase I/II clinical trials. Despite more than 20 years research on IL-15, some controversial issues remain to be addressed. A first point concerns the detection of the sIL-15/IL-15Rα in plasma of healthy donors or patients with cancer and its biological significance. The second and third unsolved question regards the protumorigenic role of the IL-15/IL-15Rα complex in human cancer and the detrimental immunological consequences associated to prolonged exposure of natural killer (NK) cells to both forms of soluble IL-15, respectively. Data suggest that in vivo prolonged or repeated exposure to monomeric sIL-15 or the soluble complex may lead to NK hypo-responsiveness through the expansion of the CD8⁺/CD44⁺ T cell subset that would suppress NK cell functions. In vitro experiments indicate that soluble complex and monomeric IL-15 may cause NK hyporesponsiveness through a direct effect caused by their prolonged stimulation, suggesting that this mechanism could also be effective in vivo. Therefore, a better knowledge of IL-15 and a more appropriate use of both its soluble forms, in terms of concentrations and time of exposure, are essential in order to improve their therapeutic use. In cancer, the overproduction of sIL-15/IL-15Rα could represent a novel mechanism of immune escape. The soluble complex may act as a decoy cytokine unable to efficiently foster NK cells, or could induce NK hyporesponsiveness through an excessive and prolonged stimulation depending on the type of IL-15Rα isoforms associated. All these unsolved questions are not merely limited to the knowledge of IL-15 pathophysiology, but are crucial also for the therapeutic use of this cytokine. Therefore, in this review, we will discuss key unanswered issues on the heterogeneity and biological significance of IL-15 isoforms, analyzing both their cancer-related biological functions and their therapeutic implications.

Defective expansion and function of memory like natural killer cells in HIV+ individuals with latent tuberculosis infection

PURPOSE

Tuberculosis (TB) is the leading cause of infectious disease related mortality, and only 10% of the infected individuals develop active disease. The likelihood of progression of latent tuberculosis infection (LTBI) to active TB disease is high in HIV infected individuals. Identification of HIV+ individuals at risk would allow treating targeted population, facilitating completion of therapy for LTBI and prevention of TB development. NK cells have an important role in T cell independent immunity against TB, but the exact role of NK cell subsets in LTBI and HIV is not well characterized.

METHODS

In this study, we compared the expansion and function of memory like NK cells from HIV-LTBI+ individuals and treatment naïve HIV+LTBI+ patients in response to Mtb antigens ESAT-6 and CFP-10.

RESULTS

In freshly isolated PBMCs, percentages of CD3-CD56+ NK cells were similar in HIV+LTBI+ patients and healthy HIV-LTBI+ individuals. However, percentages of CD3-CD56+CD16+ NK cells were higher in healthy HIV-LTBI+ individuals compared to HIV+LTBI+ patients. HIV infection also inhibited the expansion of memory like NK cells, production of IL-32α, IL-15 and IFN-γ in response to Mtb antigens in LTBI+ individuals.

CONCLUSION

We studied phenotypic, functional subsets and activation of memory like-NK cells during HIV infection and LTBI. We observed that HIV+LTBI+ patients demonstrated suboptimal NK cell and monocyte interactions in response to Mtb, leading to reduced IL-15, IFN-γ and granzyme B and increased CCL5 production. Our study highlights the effect of HIV and LTBI on modulation of NK cell activity to understand their role in development of interventions to prevent progression to TB in high risk individuals.

Pediatric Tumors-Mediated Inhibitory Effect on NK Cells: The Case of Neuroblastoma and Wilms' Tumors

Simple Summary

Neuroblastoma (NB) and Wilms’ tumor (WT) are the most common childhood solid extracranial tumors. The current treatments consist of a combination of surgery and chemotherapy or radiotherapy in high-risk patients. Such treatments are responsible for significant adverse events requiring long-term monitoring. Thus, a main challenge in NB and WT treatment is the development of novel therapeutic strategies to eliminate or minimize the adverse effects. The characterization of the immune environment could allow for the identification of new therapeutic targets. Herein, we described the interaction between these tumors and innate immune cells, in particular natural killer cells and monocytes. The detection of the immunosuppressive activity of specific NB and WT tumor cells on natural killer cells and on monocytes could offer novel cellular and molecular targets for an effective immunotherapy of NB and WT.

Abstract

Natural killer (NK) cells play a key role in the control of cancer development, progression and metastatic dissemination. However, tumor cells develop an array of strategies capable of impairing the activation and function of the immune system, including NK cells. In this context, a major event is represented by the establishment of an immunosuppressive tumor microenvironment (TME) composed of stromal cells, myeloid-derived suppressor cells, tumor-associated macrophages, regulatory T cells and cancer cells themselves. The different immunoregulatory cells infiltrating the TME, through the release of several immunosuppressive molecules or by cell-to-cell interactions, cause an impairment of the recruitment of NK cells and other lymphocytes with effector functions. The different mechanisms by which stromal and tumor cells impair NK cell function have been particularly explored in adult solid tumors and, in less depth, investigated and discussed in a pediatric setting. In this review, we will compare pediatric and adult solid malignancies concerning the respective mechanisms of NK cell inhibition, highlighting novel key data in neuroblastoma and Wilms’ tumor, two of the most frequent pediatric extracranial solid tumors. Indeed, both tumors are characterized by the presence of stromal cells acting through the release of immunosuppressive molecules. In addition, specific tumor cell subsets inhibit NK cell cytotoxic function by cell-to-cell contact mechanisms likely controlled by the transcriptional coactivator TAZ. These findings could lead to a more performant diagnostic approach and to the development of novel immunotherapeutic strategies targeting the identified cellular and molecular targets.

Wilms' Tumor Primary Cells Display Potent Immunoregulatory Properties on NK Cells and Macrophages

The immune response plays a crucial defensive role in cancer growth and metastasis and is a promising target in different tumors. The role of the immune system in Wilm's Tumor (WT), a common pediatric renal malignancy, is still to be explored. The characterization of the immune environment in WT could allow the identification of new therapeutic strategies for targeting possible inhibitory mechanisms and/or lowering toxicity of the current treatments. In this study, we stabilized four WT primary cultures expressing either a blastematous (CD56+/CD133-) or an epithelial (CD56-/CD133+) phenotype and investigated their interactions with innate immune cells, namely NK cells and monocytes. We show that cytokine-activated NK cells efficiently kill WT cells. However, after co-culture with WT primary cells, NK cells displayed an impaired cytotoxic activity, decreased production of IFNγ and expression of CD107a, DNAM-1 and NKp30. Analysis of the effects of the interaction between WT cells and monocytes revealed their polarization towards alternatively activated macrophages (M2) that, in turn, further impaired NK cell functions. In conclusion, we show that both WT blastematous and epithelial components may contribute directly and indirectly to a tumor immunosuppressive microenvironment that is likely to play a role in tumor progression.

The deubiquitinase Otub1 controls the activation of CD8+ T cells and NK cells by regulating IL-15-mediated priming

CD8 T cells and natural killer (NK) cells, central cellular components of immune responses against pathogens and cancer, rely on IL-15 for homeostasis. Here we show that IL-15 also mediates homeostatic priming of CD8 T cells for antigen-stimulated activation, which is controlled by a deubiquitinase, Otub1. IL-15 mediates membrane recruitment of Otub1, which inhibits ubiquitin-dependent activation of AKT, a pivotal kinase for T cell activation and metabolism. Otub1 deficiency in mice causes aberrant responses of CD8 T cells to IL-15, rendering naive CD8 T cells hyper-sensitive to antigen stimulation characterized by enhanced metabolic reprograming and effector functions. Otub1 also controls the maturation and activation of NK cells. Consistently, Otub1 deletion profoundly enhances anticancer immunity through unleashing the activity of CD8 T cells and NK cells. These findings suggest that Otub1 controls the activation of CD8 T cells and NK cells by functioning as a checkpoint of IL-15-mediated priming.

TBK-binding protein 1 regulates IL-15-induced autophagy and NKT cell survival

The cytokine IL-15 mediates development and survival of immune cells, including natural killer T (NKT) cells, but the underlying mechanism of IL-15 function is incompletely understood. Here we show that IL-15 induces autophagy in NKT cells with a mechanism that involves a crucial signaling component, TBK-binding protein 1 (Tbkbp1). Tbkbp1 facilitates activation of the autophagy-initiating kinase Ulk1 through antagonizing the inhibitory action of mTORC1. This antagonization involves the recruitment of an mTORC1-opposing phosphatase to Ulk1. Tbkbp1 deficiency attenuates IL-15-stimulated NKT cell autophagy, and is associated with mitochondrial dysfunction, aberrant ROS production, defective Bcl2 expression and reduced NKT cell survival. Consequently, Tbkbp1-deficient mice have profound deficiency in NKT cells, especially IFN-γ-producing NKT1. We further show that Tbkbp1 regulates IL-15-stimulated autophagy and survival of NK cells. These findings suggest a mechanism of autophagy induction by IL-15, and establish Tbkbp1 as a regulator of NKT cell development and survival.

IL-15 Promotes Polyfunctional NK Cell Responses to Influenza by Boosting IL-12 Production

IL-15 is a key regulator of NK cell maintenance and proliferation and synergizes with other myeloid cell–derived cytokines to enhance NK cell effector function. At low concentrations, trans-presentation of IL-15 by dendritic cells can activate NK cells, whereas at higher concentrations it can act directly on NK cells, independently of accessory cells. In this study, we investigate the potential for IL-15 to boost responses to influenza virus by promoting accessory cell function. We find that coculture of human PBMCs with inactivated whole influenza virus (A/Victoria/361/2011) in the presence of very low concentrations of IL-15 results in increased production of myeloid cell–derived cytokines, including IL-12, IFN-α2, GM-CSF, and IL-1β, and an increased frequency of polyfunctional NK cells (defined by the expression of two or more of CD107a, IFN-γ, and CD25). Neutralization experiments demonstrate that IL-15–mediated enhancement of NK cell responses is primarily dependent on IL-12 and partially dependent on IFN-αβR1 signaling. Critically, IL-15 boosted the production of IL-12 in influenza-stimulated blood myeloid dendritic cells. IL-15 costimulation also restored the ability of less-differentiated NK cells from human CMV-seropositive individuals to respond to influenza virus. These data suggest that very low concentrations of IL-15 play an important role in boosting accessory cell function to support NK cell effector functions.

Frequencies of IL-15Rα+ cells in patients with Behçet's disease and the effects of overexpressing IL-15Rα+ on disease symptoms in mice

It has been suggested higher serum levels of IL-15 and lower expression levels of IL-15 receptor alpha (IL-15Rα) are correlated with pathogenesis of Behçet's disease (BD). However, whether overexpressing IL-15Rα could be used as a therapeutic candidate for BD is currently unclear. Therefore, the purpose of this study was to determine whether overexpressing IL-15Rα could affect BD symptoms in a mouse model. IL-15/IL-15Rα complex expressing vector or protein complex of IL-15/IL-15Rα-Fc was used to treat BD mice. Frequencies of IL-15Rα+ cells in peripheral blood leukocytes (PBL) and lymph node cells were determined using a flow cytometer. BD symptoms in mice improved after treatment with IL-15/15Rα expression vector or IL-15/IL-15Rα-Fc protein complex. In addition, treatment with pIL-15/15Rα significantly (p = .016) decreased disease severity score of BD mice compared to treatment with control vector. Frequencies of IL-15Rα+ cells were also significantly (p = .01) higher in peritoneal macrophages of pIL-15/15Rα treated BD mice than those of mice treated with control vector. Frequencies of IL-15Rα+ PBL were also significantly higher in BD mice treated with IL-15/IL-15Rα-Fc protein complex than those in the control group. These results suggest up-regulating IL-15Rα+ cells could be used as novel therapeutic strategies to control BD in the future.

CD215+ Myeloid Cells Respond to Interleukin 15 Stimulation and Promote Tumor Progression

Interleukin 15 (IL-15) regulates the development, survival, and functions of multiple innate and adaptive immune cells and plays a dual role in promoting both tumor cell growth and antitumor immunity. Here, we demonstrated that the in vivo injection of recombinant human IL-15 (200 µg/kg) or murine IL-15 (3 µg/kg) to tumor-bearing NOD-SCID-IL2Rg-/- (NSI) mice resulted in increased tumor progression and CD45+ CD11b+ Gr-1+ CD215+ cell expansion in the tumors and spleen. In B16F10-bearing C57BL/6 mice model, we found that murine IL-15 has antitumoral effect since the activation and expansion of CD8+ T cells with murine IL-15 treatment. But no enhanced or reduced tumor growth was observed in mice when human IL-15 was used. However, both murine and human IL-15 promote CD45+ CD11b+ Gr-1+ CD215+ cells expansion. In xenograft tumor models, CD215+ myeloid cells, but not CD215- cells, responded to human IL-15 stimulation and promoted tumor growth. Furthermore, we found that human IL-15 mediated insulin-like growth factor-1 production in CD215+ myeloid cells and blocking IGF-1 reduced the tumor-promoting effect of IL-15. Finally, we observed that higher IGF-1 expression is an indicator of poor prognosis among lung adenocarcinoma patients. These findings provide evidence that IL-15 may promote tumor cell progression via CD215+ myeloid cells, and IGF-1 may be an important candidate that IL-15 facilitates tumor growth.

Group 1 Innate Lymphoid Cell Lineage Identity Is Determined by a cis-Regulatory Element Marked by a Long Non-coding RNA

Commitment to the innate lymphoid cell (ILC) lineage is determined by Id2, a transcriptional regulator that antagonizes T and B cell-specific gene expression programs. Yet how Id2 expression is regulated in each ILC subset remains poorly understood. We identified a cis-regulatory element demarcated by a long non-coding RNA (lncRNA) that controls the function and lineage identity of group 1 ILCs, while being dispensable for early ILC development and homeostasis of ILC2s and ILC3s. The locus encoding this lncRNA, which we termed Rroid, directly interacted with the promoter of its neighboring gene, Id2, in group 1 ILCs. Moreover, the Rroid locus, but not the lncRNA itself, controlled the identity and function of ILC1s by promoting chromatin accessibility and deposition of STAT5 at the promoter of Id2 in response to interleukin (IL)-15. Thus, non-coding elements responsive to extracellular cues unique to each ILC subset represent a key regulatory layer for controlling the identity and function of ILCs.

Control of Metastasis by NK Cells

The metastatic spread of malignant cells to distant anatomical locations is a prominent cause of cancer-related death. Metastasis is governed by cancer-cell-intrinsic mechanisms that enable neoplastic cells to invade the local microenvironment, reach the circulation, and colonize distant sites, including the so-called epithelial-to-mesenchymal transition. Moreover, metastasis is regulated by microenvironmental and systemic processes, such as immunosurveillance. Here, we outline the cancer-cell-intrinsic and -extrinsic factors that regulate metastasis, discuss the key role of natural killer (NK) cells in the control of metastatic dissemination, and present potential therapeutic approaches to prevent or target metastatic disease by harnessing NK cells.

Discovery and characterization of a novel humanized anti-IL-15 antibody and its relevance for the treatment of refractory celiac disease and eosinophilic esophagitis

Interleukin-15 (IL-15) is a critical regulator of immune responses, especially at mucosal interfaces within the gastro-intestinal tract. Here, we describe the discovery and characterization of a humanized antibody to IL-15. Data from its epitope and mode of action, cell biology and primate pharmacology, as well as translational studies in human samples and in vivo proof-of-concept experiments in mouse models demonstrate the therapeutic potential of this new antibody targeting IL-15 for refractory celiac disease and eosinophilic esophagitis.

IL-15 receptor alpha as the magic wand to boost the success of IL-15 antitumor therapies: The upswing of IL-15 transpresentation

Interleukin (IL)-15 as a stand-alone therapy can activate the antitumor functions of immune effector cells resulting in significant tumor regression. Interestingly, combining IL-15 with the α-moiety of its receptor (IL-15Rα), also called IL-15 transpresentation, increases the in vivo half-life of IL-15 and enhances binding of IL-15 with cells expressing the IL-15Rβγ, such as NK cells and CD8⁺ T cells. These features enlarge the signal transmission of IL-15, resulting in improved proliferation and antitumor activities of both NK cells and CD8⁺ T cells, eventually leading to enhanced killing of tumor cells. In this review, we discuss the antitumor strategies in which this IL-15 transpresentation mechanism is implemented, that are currently under preclinical investigation. Furthermore, we give an overview of the studies in which the IL-15/IL-15Rα complexes are combined with other antitumor therapies. The promising results in these preclinical studies have incited several clinical trials to test the safety and efficacy of IL-15 transpresentation strategies to treat both hematological and advanced solid tumors.