Differential antitumor immunity mediated by NKT cell subsets in vivo

Effective suppression of tumor growth and hepatic metastasis of neuroblastoma by NKT-stimulatory phenyl glycolipid

Invariant natural killer T cell (iNKT) cells produce large amounts of cytokines in response to α-Galactosylceramide (α-GalCer) stimulation. An analog containing two phenyl rings on the acyl chain, C34, was previously found to be more Th1-biased than α-GalCer and triggered greater anticancer activities against breast cancer, melanoma and lung cancer in mice. Since liver is enriched in iNKT cells, we investigated anticancer efficacy of C34 on neuroblastoma with hepatic metastasis. C34 induced Th1-biased cytokine secretions in the liver, significantly suppressed neuroblastoma growth/metastasis and prolonged mouse survival. The anti-tumor efficacy might be attributed to greater expansions of hepatic NKT, NK, CD4+ T, and CD8+ T cells as well as reduction of the number of SSCloGr1intCD11b+ subset of myeloid-derived suppressor cells (MDSCs) in the liver of tumor-bearing mice, as compared to DMSO control group. C34 also upregulated expression of CD1d and CD11c, especially in the SSCloGr1intCD11b+ subset of MDSCs, which might be killed by C34-activated NKT cells, attributing to their reduced number. In addition, C34 also induced expansion of CD4+ T, CD8+ T, and NK cells, which might eliminate neuroblastoma cells. These immune-modulating effects of C34 might act in concert in the local milieu of liver to suppress the tumor growth. Further analysis of database of neuroblastoma revealed that patients with high CD11c expression in the monocytic MDSCs in the tumor had longer survival, suggesting the potential clinical application of C34 for treatment of neuroblastoma.

Intratumoral NKT cell accumulation promotes antitumor immunity in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is a potentially lethal disease lacking effective treatments. Its immunosuppressive tumor microenvironment (TME) allows it to evade host immunosurveillance and limits response to immunotherapy. Here, using the mouse KRT19-deficient (sgKRT19-edited) PDA model, we find that intratumoral accumulation of natural killer T (NKT) cells is required to establish an immunologically active TME. Mechanistically, intratumoral NKT cells facilitate type I interferon (IFN) production to initiate an antitumor adaptive immune response, and orchestrate the intratumoral infiltration of T cells, dendritic cells, natural killer cells, and myeloid-derived suppressor cells. At the molecular level, NKT cells promote the production of type I IFN through the interaction of their CD40L with CD40 on myeloid cells. To evaluate the therapeutic potential of these observations, we find that administration of folinic acid to mice bearing PDA increases NKT cells in the TME and improves their response to anti-PD-1 antibody treatment. In conclusion, NKT cells have an essential role in the immune response to mouse PDA and are potential targets for immunotherapy.

A Humanized Mouse Model Coupled with Computational Analysis Identifies Potent Glycolipid Agonist of Invariant NKT Cells

Invariant natural killer T (iNKT) cells play an important role in many innate and adaptive immune responses, with potential applications in cancer immunotherapy. The glycolipid KRN7000, an α-galactosylceramide, potently activates iNKT cells but has shown limited anticancer effects in human clinical trials conducted so far. In spite of almost three decades of structure-activity relationship studies, no alternative glycolipid has yet emerged as a superior clinical candidate. One reason for the slow progress in this area is that standard mouse models do not accurately reflect the specific ligand recognition by human iNKT cells and their requirements for activation. Here we evaluated a series of KRN7000 analogues using a recently developed humanized mouse model that expresses a human αTCR chain sequence and human CD1d. In this process, a more stimulatory, previously reported but largely overlooked glycolipid was identified, and its activity was probed and rationalized via molecular simulations.

Invariant natural killer T cells in autoimmune cholangiopathies: Mechanistic insights and therapeutic implications

Invariant natural killer T cells (iNKT cells) constitute a specialized subset of lymphocytes that bridges innate and adaptive immunity through a combination of traits characteristic of both conventional T cells and innate immune cells. iNKT cells are characterized by their invariant T cell receptors and discerning recognition of lipid antigens, which are presented by the non-classical MHC molecule, CD1d. Within the hepatic milieu, iNKT cells hold heightened prominence, contributing significantly to the orchestration of organ homeostasis. Their unique positioning to interact with diverse cellular entities, ranging from epithelial constituents like hepatocytes and cholangiocytes to immunocytes including Kupffer cells, B cells, T cells, and dendritic cells, imparts them with potent immunoregulatory abilities. Emergering knowledge of liver iNKT cells subsets enable to explore their therapeutic potential in autoimmne liver diseases. This comprehensive review navigates the landscape of iNKT cell investigations in immune-mediated cholangiopathies, with a particular focus on primary biliary cholangitis and primary sclerosing cholangitis, across murine models and human subjects to unravel the intricate involvements of iNKT cells in liver autoimmunity. Additionally, we also highlight the prospectives of iNKT cells as therapeutic targets in cholangiopathies. Modulation of the equilibrium between regulatory and proinflammatory iNKT subsets can be defining determinant in the dynamics of hepatic autoimmunity. This discernment not only enriches our foundational comprehension but also lays the groundwork for pioneering strategies to navigate the multifaceted landscape of liver autoimmunity.

IL-21-armored B7H3 CAR-iNKT cells exert potent antitumor effects

CD1d-restricted invariant NKT (iNKT) cells play a critical role in tumor immunity. However, the scarcity and limited persistence restricts their development and clinical application. Here, we demonstrated that iNKT cells could be efficiently expanded using modified cytokines combination from peripheral blood mononuclear cells. Introduction of IL-21 significantly increased the frequency of CD62L-positive memory-like iNKT cells. iNKT cells armoring with B7H3-targeting second generation CAR and IL-21 showed potent tumor cell killing activity. Moreover, co-expression of IL-21 promoted the activation of Stat3 signaling and reduced the expression of exhaustion markers in CAR-iNKT cells in vitro. Most importantly, IL-21-arming significantly prolonged B7H3 CAR-iNKT cell proliferation and survival in vivo, thus improving their therapeutic efficacy in mouse renal cancer xerograph models without observed cytokine-related adverse events. In summary, these results suggest that B7H3 CAR-iNKT armored with IL-21 is a promising therapeutic strategy for cancer treatment.

Targeting adrenergic receptors to mitigate invariant natural killer T cells-induced acute liver injury

Invariant Natural Killer T (iNKT) cell activation by α-galactosylceramide (αGC) potentiates cytotoxic immune responses against tumors. However, αGC-induced liver injury is a limiting factor for iNKT-based immunotherapy. Although adrenergic receptor stimulation is an important immunosuppressive signal that curbs tissue damage induced by inflammation, its effect on the antitumor activity of invariant Natural Killer T (iNKT) cells remains unclear. We use mouse models and pharmacological tools to show that the stimulation of the sympathetic nervous system (SNS) inhibits αGC-induced liver injury without impairing iNKT cells' antitumoral functions. Mechanistically, SNS stimulation prevents the collateral effect of TNF-α production by iNKT cells and neutrophil accumulation in hepatic parenchyma. Our results suggest that the modulation of the adrenergic signaling can be a complementary approach to αGC-based immunotherapy to mitigate iNKT-induced liver injury without compromising its antitumoral activity.

Immune landscape and immunotherapy of hepatocellular carcinoma: focus on innate and adaptive immune cells

Hepatocellular carcinoma (HCC) is responsible for roughly 90% of all cases of primary liver cancer, and the cases are on the rise. The treatment of advanced HCC is a serious challenge. Immune checkpoint inhibitor (ICI) therapy has marked a watershed moment in the history of HCC systemic treatment. Atezolizumab in combination with bevacizumab has been approved as a first-line treatment for advanced HCC since 2020; however, the combination therapy is only effective in a limited percentage of patients. Considering that the tumor immune microenvironment (TIME) has a great impact on immunotherapies for HCC, an in-depth understanding of the immune landscape in tumors and the current immunotherapeutic approaches is extremely necessary. We elaborate on the features, functions, and cross talk of the innate and adaptive immune cells in HCC and highlight the benefits and drawbacks of various immunotherapies for advanced HCC, as well as future projections. HCC consists of a heterogeneous group of cancers with distinct etiologies and immune microenvironments. Almost all the components of innate and adaptive immune cells in HCC have altered, showing a decreasing trend in the number of tumor suppressor cells and an increasing trend in the pro-cancer cells, and there is also cross talk between various cell types. Various immunotherapies for HCC have also shown promising efficacy and application prospect. There are multilayered interwoven webs among various immune cell types in HCC, and emerging evidence demonstrates the promising prospect of immunotherapeutic approaches for HCC.

Aging unconventionally: γδ T cells, iNKT cells, and MAIT cells in aging

Unconventional T cells include γδ T cells, invariant Natural Killer T cells (iNKT) cells and Mucosal Associated Invariant T (MAIT) cells, which are distinguished from conventional T cells by their recognition of non-peptide ligands presented by non-polymorphic antigen presenting molecules and rapid effector functions that are pre-programmed during their development. Here we review current knowledge of the effect of age on unconventional T cells, from early life to old age, in both mice and humans. We then discuss the role of unconventional T cells in age-associated diseases and infections, highlighting the similarities between members of the unconventional T cell family in the context of aging.

Classic costimulatory interactions in MAIT cell responses: from gene expression to immune regulation

Mucosa-associated invariant T (MAIT) cells are evolutionarily conserved, innate-like T lymphocytes with enormous immunomodulatory potentials. Due to their strategic localization, their invariant T cell receptor (iTCR) specificity for major histocompatibility complex-related protein 1 (MR1) ligands of commensal and pathogenic bacterial origin, and their sensitivity to infection-elicited cytokines, MAIT cells are best known for their antimicrobial characteristics. However, they are thought to also play important parts in the contexts of cancer, autoimmunity, vaccine-induced immunity, and tissue repair. While cognate MR1 ligands and cytokine cues govern MAIT cell maturation, polarization, and peripheral activation, other signal transduction pathways, including those mediated by costimulatory interactions, regulate MAIT cell responses. Activated MAIT cells exhibit cytolytic activities and secrete potent inflammatory cytokines of their own, thus transregulating the biological behaviors of several other cell types, including dendritic cells, macrophages, natural killer cells, conventional T cells, and B cells, with significant implications in health and disease. Therefore, an in-depth understanding of how costimulatory pathways control MAIT cell responses may introduce new targets for optimized MR1/MAIT cell-based interventions. Herein, we compare and contrast MAIT cells and mainstream T cells for their expression of classic costimulatory molecules belonging to the immunoglobulin superfamily and the tumor necrosis factor (TNF)/TNF receptor superfamily, based not only on the available literature but also on our transcriptomic analyses. We discuss how these molecules participate in MAIT cells' development and activities. Finally, we introduce several pressing questions vis-à-vis MAIT cell costimulation and offer new directions for future research in this area.

Mettl3-m6A-Creb1 forms an intrinsic regulatory axis in maintaining iNKT cell pool and functional differentiation

N6-methyladenosine (m6A) methyltransferase Mettl3 is involved in conventional T cell immunity; however, its role in innate immune cells remains largely unknown. Here, we show that Mettl3 intrinsically regulates invariant natural killer T (iNKT) cell development and function in an m6A-dependent manner. Conditional ablation of Mettl3 in CD4+CD8+ double-positive (DP) thymocytes impairs iNKT cell proliferation, differentiation, and cytokine secretion, which synergistically causes defects in B16F10 melanoma resistance. Transcriptomic and epi-transcriptomic analyses reveal that Mettl3 deficiency disturbs the expression of iNKT cell-related genes with altered m6A modification. Strikingly, Mettl3 modulates the stability of the Creb1 transcript, which in turn controls the protein and phosphorylation levels of Creb1. Furthermore, conditional targeting of Creb1 in DP thymocytes results in similar phenotypes of iNKT cells lacking Mettl3. Importantly, ectopic expression of Creb1 largely rectifies such developmental defects in Mettl3-deficient iNKT cells. These findings reveal that the Mettl3-m6A-Creb1 axis plays critical roles in regulating iNKT cells at the post-transcriptional layer.

Markers and makers of NKT17 cells

Invariant natural killer T (iNKT) cells are thymus-generated innate-like αβ T cells that undergo terminal differentiation in the thymus. Such a developmental pathway differs from that of conventional αβ T cells, which are generated in the thymus but complete their functional maturation in peripheral tissues. Multiple subsets of iNKT cells have been described, among which IL-17-producing iNKT cells are commonly referred to as NKT17 cells. IL-17 is considered a proinflammatory cytokine that can play both protective and pathogenic roles and has been implicated as a key regulatory factor in many disease settings. Akin to other iNKT subsets, NKT17 cells acquire their effector function during thymic development. However, the cellular mechanisms that drive NKT17 subset specification, and how iNKT cells in general acquire their effector function prior to antigen encounter, remain largely unknown. Considering that all iNKT cells express the canonical Vα14-Jα18 TCRα chain and all iNKT subsets display the same ligand specificity, i.e., glycolipid antigens in the context of the nonclassical MHC-I molecule CD1d, the conundrum is explaining how thymic NKT17 cell specification is determined. Mapping of the molecular circuitry of NKT17 cell differentiation, combined with the discovery of markers that identify NKT17 cells, has provided new insights into the developmental pathway of NKT17 cells. The current review aims to highlight recent advances in our understanding of thymic NKT17 cell development and to place these findings in the larger context of iNKT subset specification and differentiation.

Pathogenic NKT cells attenuate urogenital chlamydial clearance and enhance infertility

Urogenital chlamydial infections continue to increase with over 127 million people affected annually, causing significant economic and public health pressures. While the role of traditional MHCI and II peptide presentation is well defined in chlamydial infections, the role of lipid antigens in immunity remains unclear. Natural killer (NK) T cells are important effector cells that recognize and respond to lipid antigens during infections. Chlamydial infection of antigen-presenting cells facilitates presentation of lipid on the MHCI-like protein, CD1d, which stimulates NKT cells to respond. During urogenital chlamydial infection, wild-type (WT) female mice had significantly greater chlamydial burden than CD1d-/- (NKT-deficient) mice, and had significantly greater incidence and severity of immunopathology in both primary and secondary infections. WT mice had similar vaginal lymphocytic infiltrate, but 59% more oviduct occlusion compared to CD1d-/- mice. Transcriptional array analysis of oviducts day 6 post-infection revealed WT mice had elevated levels of Ifnγ (6-fold), Tnfα (38-fold), Il6 (2.5-fold), Il1β (3-fold) and Il17a (6-fold) mRNA compared to CD1d-/- mice. In infected females, oviduct tissues had an elevated infiltration of CD4+ -invariant NKT (iNKT) cells, however, iNKT-deficient Jα18-/- mice had no significant differences in hydrosalpinx severity or incidence compared to WT controls. Lipid mass spectrometry of surface-cleaved CD1d in infected macrophages revealed an enhancement of presented lipids and cellular sequestration of sphingomyelin. Taken together, these data suggest an immunopathogenic role for non-invariant NKT cells in urogenital chlamydial infections, facilitated by lipid presentation via CD1d via infected antigen-presenting cells.

Towards a better understanding of human iNKT cell subpopulations for improved clinical outcomes

Invariant natural killer T (iNKT) cells are a unique T lymphocyte population expressing semi-invariant T cell receptors (TCRs) that recognise lipid antigens presented by CD1d. iNKT cells exhibit potent anti-tumour activity through direct killing mechanisms and indirectly through triggering the activation of other anti-tumour immune cells. Because of their ability to induce potent anti-tumour responses, particularly when activated by the strong iNKT agonist αGalCer, they have been the subject of intense research to harness iNKT cell-targeted immunotherapies for cancer treatment. However, despite potent anti-tumour efficacy in pre-clinical models, the translation of iNKT cell immunotherapy into human cancer patients has been less successful. This review provides an overview of iNKT cell biology and why they are of interest within the context of cancer immunology. We focus on the iNKT anti-tumour response, the seminal studies that first reported iNKT cytotoxicity, their anti-tumour mechanisms, and the various described subsets within the iNKT cell repertoire. Finally, we discuss several barriers to the successful utilisation of iNKT cells in human cancer immunotherapy, what is required for a better understanding of human iNKT cells, and the future perspectives facilitating their exploitation for improved clinical outcomes.

A circulating subset of iNKT cells mediates antitumor and antiviral immunity

Invariant natural killer T (iNKT) cells are a group of innate-like T lymphocytes that recognize lipid antigens. They are supposed to be tissue resident and important for systemic and local immune regulation. To investigate the heterogeneity of iNKT cells, we recharacterized iNKT cells in the thymus and peripheral tissues. iNKT cells in the thymus were divided into three subpopulations by the expression of the natural killer cell receptor CD244 and the chemokine receptor CXCR6 and designated as C0 (CD244 − CXCR6 − ), C1 (CD244 − CXCR6 + ), or C2 (CD244 + CXCR6 + ) iNKT cells. The development and maturation of C2 iNKT cells from C0 iNKT cells strictly depended on IL-15 produced by thymic epithelial cells. C2 iNKT cells expressed high levels of IFN-γ and granzymes and exhibited more NK cell–like features, whereas C1 iNKT cells showed more T cell–like characteristics. C2 iNKT cells were influenced by the microbiome and aging and suppressed the expression of the autoimmune regulator AIRE in the thymus. In peripheral tissues, C2 iNKT cells were circulating that were distinct from conventional tissue-resident C1 iNKT cells. Functionally, C2 iNKT cells protected mice from the tumor metastasis of melanoma cells by enhancing antitumor immunity and promoted antiviral immune responses against influenza virus infection. Furthermore, we identified human CD244 + CXCR6 + iNKT cells with high cytotoxic properties as a counterpart of mouse C2 iNKT cells. Thus, this study reveals a circulating subset of iNKT cells with NK cell–like properties distinct from conventional tissue-resident iNKT cells.

A humanized mouse model for in vivo evaluation of invariant Natural Killer T cell responses

Invariant natural killer T (iNKT) cells mediate immune responses when stimulated by glycolipid agonists presented by CD1d. In extensive studies of synthetic analogues of α-galactosyl ceramides, we identified numerous examples of significant differences in the recognition of specific glycolipids in wild type mice versus human iNKT cell clones or PBMC samples. To predict human iNKT cell responses more accurately in a mouse model, we derived a mouse line in which compound genetic modifications were used to express a human-like iNKT cell TCR along with human CD1d in place of the endogenous mouse proteins. Detailed transcriptional and phenotypic profiling demonstrated that these partially humanized mice developed an expanded population of T cells recognizing CD1d-presented glycolipid antigens, among which a subset characterized by expression of chemokine receptor CXCR6 had features characteristic of authentic iNKT cells. Responses to iNKT cell activating glycolipids in these mice generated cytokine production in vitro and in vivo that showed a pattern of fine specificity that closely resembled that of cultured human iNKT cell clones. Anti-tumor responses to variants of α-galactosyl ceramide in VαKI mice also correlated with their potency for stimulating human iNKT cells. This genetically modified mouse line provides a practical model for human presentation and recognition of iNKT cell activators in the context of a normally functioning immune system, and may furnish valuable opportunities for preclinical evaluation of iNKT cell-based therapies.

TCR-engineered iNKT cells induce robust antitumor response by dual targeting cancer and suppressive myeloid cells

Adoptive immunotherapy with T cells engineered with tumor-specific T cell receptors (TCRs) holds promise for cancer treatment. However, suppressive cues generated in the tumor microenvironment (TME) can hinder the efficacy of these therapies, prompting the search for strategies to overcome these detrimental conditions and improve cellular therapeutic approaches. CD1d-restricted invariant natural killer T (iNKT) cells actively participate in tumor immunosurveillance by restricting suppressive myeloid populations in the TME. Here, we showed that harnessing iNKT cells with a second TCR specific for a tumor-associated peptide generated bispecific effectors for CD1d- and major histocompatibility complex (MHC)-restricted antigens in vitro. Upon in vivo transfer, TCR-engineered iNKT (TCR-iNKT) cells showed the highest efficacy in restraining the progression of multiple tumors that expressed the cognate antigen compared with nontransduced iNKT cells or CD8+ T cells engineered with the same TCR. TCR-iNKT cells achieved robust cancer control by simultaneously modulating intratumoral suppressive myeloid populations and killing malignant cells. This dual antitumor function was further enhanced when the iNKT cell agonist α-galactosyl ceramide (α-GalCer) was administered as a therapeutic booster through a platform that ensured controlled delivery at the tumor site, named multistage vector (MSV). These preclinical results support the combination of tumor-redirected TCR-iNKT cells and local α-GalCer boosting as a potential therapy for patients with cancer.

Single-cell analysis reveals differences among iNKT cells colonizing peripheral organs and identifies Klf2 as a key gene for iNKT emigration

Invariant natural killer T cell (iNKT) subsets are differentially distributed in various immune organs. However, it remains unclear whether iNKT cells exhibit phenotypical and functional differences in different peripheral organs and how thymic iNKT cells emigrate to peripheral organs. Here, we used single-cell RNA-seq to map iNKT cells from peripheral organs. iNKT1 cells from liver, spleen, and lymph node appear to have distinct phenotypic profiles and functional capabilities. However, iNKT17 transcriptomes were comparable across peripheral organs. In addition, by integrating data with a thymic iNKT cell study, we uncovered a transient population of recent thymic emigrants, a cluster of peripheral iNKT cells with high expression of transcription factor Kruppel-like factor 2 (Klf2). Deletion of Klf2 led to a severe impairment of iNKT differentiation and migration. Our study revealed that iNKT subsets are uniquely distributed in peripheral organs with some inter-local tissue variation, especially for iNKT1 cell, and identified Klf2 as a rheostat for iNKT cell migration and differentiation.

Adoptive Immunotherapy With Engineered iNKT Cells to Target Cancer Cells and the Suppressive Microenvironment

Invariant Natural Killer T (iNKT) cells are T lymphocytes expressing a conserved semi-invariant TCR specific for lipid antigens (Ags) restricted for the monomorphic MHC class I-related molecule CD1d. iNKT cells infiltrate mouse and human tumors and play an important role in the immune surveillance against solid and hematological malignancies. Because of unique functional features, they are attractive platforms for adoptive cells immunotherapy of cancer compared to conventional T cells. iNKT cells can directly kill CD1d-expressing cancer cells, but also restrict immunosuppressive myelomonocytic populations in the tumor microenvironment (TME) via CD1d-cognate recognition, promoting anti-tumor responses irrespective of the CD1d expression by cancer cells. Moreover, iNKT cells can be adoptively transferred across MHC barriers without risk of alloreaction because CD1d molecules are identical in all individuals, in addition to their ability to suppress graft vs. host disease (GvHD) without impairing the anti-tumor responses. Within this functional framework, iNKT cells are successfully engineered to acquire a second antigen-specificity by expressing recombinant TCRs or Chimeric Antigen Receptor (CAR) specific for tumor-associated antigens, enabling the direct targeting of antigen-expressing cancer cells, while maintaining their CD1d-dependent functions. These new evidences support the exploitation of iNKT cells for donor unrestricted, and possibly off the shelf, adoptive cell therapies enabling the concurrent targeting of cancer cells and suppressive microenvironment.

Cross Talk Between Natural Killer T and Dendritic Cells and Its Impact on T Cell Responses in Infections

Both innate and adaptive immunity is vital for host defense against infections. Dendritic cells (DCs) are critical for initiating and modulating adaptive immunity, especially for T-cell responses. Natural killer T (NKT) cells are a small population of innate-like T cells distributed in multiple organs. Many studies have suggested that the cross-talk between these two immune cells is critical for immunobiology and host defense mechanisms. Not only can DCs influence the activation/function of NKT cells, but NKT cells can feedback on DCs also, thus modulating the phenotype and function of DCs and DC subsets. This functional feedback of NKT cells on DCs, especially the preferential promoting effect on CD8α+ and CD103+ DC subsets in lymphoid and non-lymphoid tissues, significantly impacts the systemic and local adaptive CD4 and CD8 T cell responses in infections. This review focuses on the two-way interaction between NKT cells and DCs, emphasizing the importance of NKT cell feedback on DCs in bridging innate and adaptive immune responses for host defense purposes.

iNKT: A new avenue for CAR-based cancer immunotherapy

Chimeric antigen receptor (CAR) T cell is a T lymphocyte-based immunotherapy, which achieves great successes in treating blood malignancies and provides new hope to cue advanced cancer patients. Invariant natural killer T (iNKT) cells are a kind of special T lymphocytes characterized by expressing invariant TCR of Vα24Vβ11 to recognize CD1d-presented glycolipid antigens, which bridge innate and adaptive immune responses. iNKT cells themselves show strong anti-tumor effect in tumor models via CD1d-mediated killing of CD1d-positive tumor cells and immunosuppressive TAMs and MDSCs, and are closely related to the prognosis of cancer patients. iNKT cells are not restricted to polymorphic human leukocyte antigen (HLA) and can prevent Graft versus Host Disease (GvHD), which makes it to be an ideal CAR vector for allogeneic therapy. Although CAR-iNKT was developed and verified by several different teams and attracts more and more attentions, many obstacles are still needed to be resolved before obtaining CAR-iNKT therapeutics. In this review, we summarized the current status of clinical application of iNKT cells and the latest achievements of CAR-iNKT cells, which provides new insight in CAR-iNKT development and usages.

SLAMF6/Ly108 promotes the development of hepatocellular carcinoma via facilitating macrophage M2 polarization

Tumor-associated macrophages (TAMs) are capable of worsening hepatocellular carcinoma (HCC) prognosis by accelerating tumor growth and progression. Signaling lymphocyte activation molecule family member 6 (SLAMF6; Ly108 in mice) is an immune regulator that is involved in numerous diseases. However, whether SLAMF6 might affect macrophage function in HCC has not yet been reported. Therefore, the present study aimed to determine the relationship between SLAMF6 expression on macrophages and HCC progression. In the present study, the expression of SLAMF6 in human blood samples and mice was analyzed by flow cytometry. Furthermore, macrophage-related polarization markers were detected via reverse transcription quantitative PCR. Clonogenic formation and Transwell assay were performed to determine the proliferation, migration and invasion of HCC cells. In addition, a murine HCC model was established to detect the function of SLAMF6 in vivo. The results demonstrated that SLAMF6 expression was increased in CD14⁺ cells obtained from patients with HCC. It was also determined that this increase was associated with a positive hepatitis B virus DNA status and high levels of α-fetoprotein. Polarized TAMs from THP-1 cells, murine peritoneal macrophages and murine bone marrow-derived macrophages all exhibited higher levels of SLAMF6 compared with M1 cells. Furthermore, an increased expression of Ly108 was detected in macrophages obtained from mice tumor tissues, indicating that the tumor microenvironment may promote Ly108 expression and macrophage M2 polarization. Ly108 small interfering RNA was applied to macrophages, which resulted in the suppression of M2 polarization. Ly108-silenced macrophages attenuated HCC cell migration and invasion and prevented tumor growth by inhibiting the nuclear factor-κB pathway. Altogether, the results from the present study suggested that SLAMF6/Ly108 was upregulated in TAMs, which may in turn accelerate the development of HCC.

The role of NK and NKT cells in the pathogenesis and improvement of multiple sclerosis following disease-modifying therapies

BACKGROUND

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS) that T cells become autoreactive by recognizing CNS antigens. Both innate and adaptive immune systems are involved in the pathogenesis of MS. In recent years, the impact of innate immune cells on MS pathogenesis has received more attention. CD56bright NK cells, as an immunoregulatory subset of NK cells, can increase the production of cytokines that modulate adaptive immune responses, whereas CD56dim NK cells are more active in cytolysis functions. These two main subsets of NK cells may have different effects on the onset or progression of MS. Invariant NKT (iNKT) cells are other immune cells involved in the control of autoimmune diseases; however, variant NKT (vNKT) cells, despite limited information, could play a role in MS remission via an immunoregulatory pathway.

AIM

We aimed to evaluate the influence of MS therapeutic agents on NK and NKT cells and NK cell subtypes.

MATERIALS AND METHODS

The possible mechanism of each MS therapeutic agent has been presented here, focusing on the effects of different disease-modifying therapies on the number of NK and NKT subtypes.

RESULTS

Expansion of CD56bright NK cells, reduction in the CD56dim cells, and enhancement in NKT cells are the more important innate immune cells alterations following the disease-modifying therapies.

CONCLUSION

Expansion of CD56bright NK cells or reduction in the CD56dim cells has been associated with a successful response to different treatments in MS. iNKT and vNKT cells could have beneficial effects on MS improving. It seems that they are enhanced due to some of MS drugs, leading to disease improvement. However, a reduction in the number of NKT cells could be due to the adverse effects of some of MS drugs on the bone marrow.

Liver X receptors regulate natural killer T cell population and antitumor activity in the liver of mice

The nuclear receptors liver X receptor α (LXRα) and LXRβ are lipid sensors that regulate lipid metabolism and immunity. Natural killer T (NKT) cells, a T cell subset expressing surface markers of both natural killer cells and T lymphocytes and involved in antitumor immunity, are another abundant immune cell type in the liver. The potential function of the metabolic regulators LXRα/β in hepatic NKT cells remains unknown. In this study, we examined the role of LXRα and LXRβ in NKT cells using mice deficient for LXRα and/or LXRβ, and found that hepatic invariant NKT (iNKT) cells are drastically decreased in LXRα/β-KO mice. Cytokine production stimulated by the iNKT cell activator α-galactosylceramide was impaired in LXRα/β-KO hepatic mononuclear cells and in LXRα/β-KO mice. iNKT cell-mediated antitumor effect was also disturbed in LXRα/β-KO mice. LXRα/β-KO mice transplanted with wild-type bone marrow showed decreased iNKT cells in the liver and spleen. The thymus of LXRα/β-KO mice showed a decreased population of iNKT cells. In conclusion, LXRα and LXRβ are essential for NKT cell-mediated immunity, such as cytokine production and hepatic antitumor activity, and are involved in NKT cell development in immune tissues, such as the thymus.

The immunological and metabolic landscape in primary and metastatic liver cancer

The liver is the sixth most common site of primary cancer in humans, and generally arises in a background of cirrhosis and inflammation. Moreover, the liver is frequently colonized by metastases from cancers of other organs (particularly the colon) because of its anatomical location and organization, as well as its unique metabolic and immunosuppressive environment. In this Review, we discuss how the hepatic microenvironment adapts to pathologies characterized by chronic inflammation and metabolic alterations. We illustrate how these immunological or metabolic changes alter immunosurveillance and thus hinder or promote the development of primary liver cancer. In addition, we describe how inflammatory and metabolic niches affect the spreading of cancer metastases into or within the liver. Finally, we review the current therapeutic options in this context and the resulting challenges that must be surmounted.

The Role of NKT Cells in Glioblastoma

Glioblastoma is an aggressive and deadly cancer, but to date, immunotherapies have failed to make significant strides in improving prognoses for glioblastoma patients. One of the current challenges to developing immunological interventions for glioblastoma is our incomplete understanding of the numerous immunoregulatory mechanisms at play in the glioblastoma tumor microenvironment. We propose that Natural Killer T (NKT) cells, which are unconventional T lymphocytes that recognize lipid antigens presented by CD1d molecules, may play a key immunoregulatory role in glioblastoma. For example, evidence suggests that the activation of type I NKT cells can facilitate anti-glioblastoma immune responses. On the other hand, type II NKT cells are known to play an immunosuppressive role in other cancers, as well as to cross-regulate type I NKT cell activity, although their specific role in glioblastoma remains largely unclear. This review provides a summary of our current understanding of NKT cells in the immunoregulation of glioblastoma as well as highlights the involvement of NKT cells in other cancers and central nervous system diseases.

NK1.1- natural killer T cells upregulate interleukin-17 expression in experimental lupus nephritis

Interleukin (IL)-17-secreting invariant natural killer T (NKT) cells are involved in several inflammatory diseases. However, their role in lupus nephritis (LN) has not been fully characterized. Samples from patients with LN or glomerulonephritis and healthy controls were obtained, and elevated IL-17+ NKT cell numbers and IL-17 expression were observed in blood cells and kidneys, respectively, in patients with LN. Comparison of a mouse model of experimental autoimmune LN with the parental strain (NKT-deficient B6.CD1d-/- mice) revealed improved proteinuria, disease severity, and histopathology and decreased levels of chemokine (C-X-C motif) ligand 16 and T cell receptor-α variable 14 expression. Spleens and kidneys of B6.CD1d-/- mice also showed downregulation of inflammatory markers and IL-17. In coculture with renal mesangial and NKT cells, inflammatory markers and IL-17 were upregulated following α-galactosylceramide treatment and downregulated after treatment with IL-17-blocking antibodies. This was most prominent with killer cell lectin-like receptor subfamily B member 1 C (NK1.1)- NKT cells. Thus, IL-17 is upregulated in LN. Activation of NKT cells regulates IL-17-related immune responses systemically and in the kidneys, primarily via NK1.1- NKT cells. IL-17-secreting NK1.1- NKT cells could serve as diagnostic and therapeutic targets for LN.NEW & NOTEWORTHY This study makes a significant contribution to the literature because our results indicate that IL-17 is upregulated in lupus nephritis and that natural killer T (NKT) cells are involved in its pathogenesis. Activation of NKT cells regulates IL-17-related immune responses, both systemically and in the kidney, and this mainly involves NK1.1- NKT cells. Furthermore, IL-17-secreting NK1.1- NKT cells could serve as a diagnostic and therapeutic target for lupus nephritis.

The split nature of tumor-infiltrating leukocytes: Implications for cancer surveillance and immunotherapy

An important development in tumor immunology was the identification of highly diverse tumor-infiltrating leukocyte subsets that can play strikingly antagonistic functions. Namely, “anti-tumor” vs. “pro-tumor” roles have been suggested for Th1 and Th17 subsets of CD4⁺ T cells, Type I or Type II NKT cells, M1 and M2 macrophages, or N1 and N2 neutrophils, respectively. While these findings are being validated in cancer patients, it is also clear that the balance between infiltrating CD8⁺ cytotoxic and Foxp3⁺ regulatory T cells has prognostic value. Here we review the pre-clinical and clinical data that have shaped our current understanding of tumor-infiltrating leukocytes.

The Adjuvant of α-Galactosylceramide Presented by Gold Nanoparticles Enhances Antitumor Immune Responses of MUC1 Antigen-Based Tumor Vaccines

BACKGROUND

Therapeutic tumor vaccines are one of the most promising strategies and have attracted great attention in cancer treatment. However, most of them have shown unsatisfactory immunogenicity, there are still few available vaccines for clinical use. Therefore, there is an urgent demand to develop novel strategies to improve the immune efficacy of antitumor vaccines.

PURPOSE

This study aimed to develop novel adjuvants and carriers to enhance the immune effect of MUC1 glycopeptide antigen-based antitumor vaccines.

METHODS

An antitumor vaccine was developed, in which MUC1 glycopeptide was used as tumor-associated antigen, α-GalCer served as an immune adjuvant and AuNPs was a multivalent carrier.

RESULTS

Immunological evaluation results indicated that the constructed vaccines enabled a significant antibody response. FACS analysis and immunofluorescence assay showed that the induced antisera exhibited a specific binding with MUC1 positive MCF-7 cells. Moreover, the induced antibody can mediate CDC to kill MCF-7 cells. Besides stimulating B cells to produce MUC1-specific antibodies, the prepared vaccines also induced MUC1-specific CTLs in vitro. Furthermore, the vaccines significantly delayed tumor development in tumor-bearing mice model.

CONCLUSION

These results showed that the construction of vaccines by presenting α-GalCer adjuvant and an antigen on gold nanoparticles offers a potential strategy to improve the antitumor response in cancer immunotherapy.

Natural Killer T Lymphocytes Integrate Innate Sensory Information and Relay Context to Effector Immune Responses

It is now appreciated that a group of lymphoid lineage cells, collectively called innate-like effector lymphocytes, have evolved to integrate information relayed by the innate sensory immune system about the state of the local tissue environment and to pass on this context to downstream effector innate and adaptive immune responses. Thereby, innate functions engrained into such innate-like lymphoid lineage cells during development can control the quality and magnitude of an immune response to a tissue-altering pathogen and facilitate the formation of memory engrams within the immune system. These goals are accomplished by the innate lymphoid cells that lack antigen-specific receptors, γδ T cell receptor (TCR)-expressing T cells, and several αβ TCR-expressing T cell subsets-such as natural killer T cells, mucosal-associated invariant T cells, et cetera. Whilst we briefly consider the commonalities in the origins and functions of these diverse lymphoid subsets to provide context, the primary topic of this review is to discuss how the semi-invariant natural killer T cells got this way in evolution through lineage commitment and onward ontogeny. What emerges from this discourse is the question: Has a "limbic immune system" emerged (screaming quietly in plain sight!) out of what has been dubbed "in-betweeners"?

iNKT Cel Transfer: The Use of Cell Sorting Combined with Flow Cytometry Validation Approach

Natural killer T (NKT) cells are an innate-like T cell subset that recognize lipid antigens presented by CD1d-expressing antigen presenting cells (APCs), such as dendritic cells, macrophages, and B cells. They can be subdivided into two different subsets according to the variation in αβ TCR chains: type I and type II NKT cells. Type I, also called invariant NKT cells (iNKT), express restricted TCRs with an invariant α-chain (Vα24-Jα18 in humans and Vα14-Jα18 in mice) and limited β-chains. Here we have established a protocol in which iNKT cells are isolated from a donor wild-type mouse and transferred into iNKT KO (Jα18^-/-) mouse. Below we will explore the methods for cell sorting of splenic iNKTs, iNKT cells transfer, and detection of transferred cells into the liver using flow cytometry technique.

IL-7 During Antigenic Stimulation Using Allogeneic Dendritic Cells Promotes Expansion of CD45RA-CD62L+CD4+ Invariant NKT Cells With Th-2 Biased Cytokine Production Profile

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes cells that recognize glycolipid antigens associated with CD1d, non-classical antigen presenting proteins. They can drive either pro-inflammatory (Th-1) or anti-inflammatory (Th-2) immune microenvironment through the production of both Th-1 and Th-2 type cytokines upon activation, thus play a vital role in cancer, infection, and autoimmune diseases. Adoptive cell therapy using ex vivo expanded iNKT cells is a promising approach to enhance anti-tumor immunity or immunosuppression. However, overcoming phenotypic and functional heterogeneity and promoting in vivo persistency of iNKT cells remains to be a challenge. Here, we compared various methods for ex vivo expansion of human iNKT cells and assessed the quality of expansion, phenotype, and cytokine production profile of expanded iNKT cells. While a direct stimulation of iNKT cells in peripheral blood mononuclear cells with agonist glycolipid led to the expansion of iNKT cells in varying degrees, stimulation of enriched iNKT cells by irradiated autologous peripheral blood mononuclear cells or allogeneic dendritic cells resulted in consistent expansion of highly pure iNKT cells. Interestingly, the mode of antigenic stimulation influenced the dominant subtype of expanded iNKT cells. Further, we evaluated whether additional IL-7 or IL-15 during antigenic stimulation with allogeneic dendritic cells can improve the phenotypic heterogeneity and modify cytokine production profile of iNKT cells expanded from 18 consecutive donors. The presence of IL-7 or IL-15 during antigenic stimulation did not affect the fold of expansion or purity of expanded iNKT cells. However, IL-7, but not IL-15, led to a better expansion of CD4⁺ iNKT cells, enhanced Th-2 type cytokine production of CD4⁺ iNKT cells, and maintained the expansion of central memory (CD45RA^-CD62L⁺) CD4⁺ iNKT cells. Our results suggest the addition of IL-7 during antigenic stimulation with allogeneic dendritic cells can promote the expansion of CD62L⁺Th-2⁺CD4⁺ human iNKT cells that can be used as novel immunotherapeutic to control excessive inflammation to treat various autoimmune diseases.

Immune cell composition in the endometrium of patients with a complete molar pregnancy: Effects on outcome

OBJECTIVE

In 15% of patients with complete hydatidiform mole (CHM), disease progresses to post-molar gestational trophoblastic neoplasia (GTN) after curettage. Tumor infiltrating lymphocytes (TILs) are essential in overcoming disease in many tumors. Infiltrating lymphocyte composition and density may influence trophoblast regression and development of post-molar GTN. We analyzed immune cell composition and density in curettaged endometrium of patients with CHM which spontaneously regressed, and of patients with CHM which progressed to post-molar GTN.

METHODS

Sixteen patients with CHM and spontaneous regression, and 16 patients with CHM which progressed to post-molar GTN were selected. Immune cell composition and density of natural killer (NK) cells, natural killer T (NKT)-like cells, Cytotoxic T cells, T-Regulatory and T-Helper cells, were determined by multiplex immunohistochemistry (mIHC).

RESULTS

Curettaged endometrium of patients with CHM and spontaneous regression contained a slightly higher number of immune cells compared to patients with CHM which progressed to post-molar GTN. NKT-like cell density was significantly higher in patients with spontaneous regression compared to patients with CHM which progressed to post-molar GTN (483 ± 296 vs.295 ± 143 (mean ± SD), p = 0.03) respectively. NKT-like cell density in the spontaneous regression group was split in 'high' and 'low' (i.e. above and below the median number of NKT-like cells). In patients with high NKT-like cell density, hCG normalized earlier than in patients with low NKT-like cell density (9.5 weeks, (range 3.7-14) vs. 12.9 weeks, (range 8.6-17.9), p = 0.05).

CONCLUSION

A high number of NKT-like cells in the endometrium of CHMs may contribute to spontaneous regression of molar trophoblast cells.

Innate Lymphocyte Mechanisms in Skin Diseases

Innate lymphocyte populations are emerging as key effectors in tissue homeostasis, microbial defense, and inflammatory skin disease. The cells are evolutionarily ancient and carry conserved principles of function, which can be achieved through shared or unique specific mechanisms. Recent technological and treatment advances have provided insight into heterogeneity within and between individuals and species. Similar pathways can extend through to adaptive lymphocytes, which softens the margins with innate lymphocyte populations and allows investigation of nonredundant pathways of immunity and inflammation that might be amenable to therapeutic intervention. Here, we review advances in understanding of innate lymphocyte biology with a focus on skin disease and the roles of commensal and pathogen responses and tissue homeostasis.

Nanovaccine administration route is critical to obtain pertinent iNKt cell help for robust anti-tumor T and B cell responses

Nanovaccines, co-delivering antigen and invariant natural killer T (iNKT) cell agonists, proved to be very effective in inducing anti-tumor T cell responses due to their exceptional helper function. However, it is known that iNKT cells are not equally present in all lymphoid organs and nanoparticles do not get evenly distributed to all immune compartments. In this study, we evaluated the effect of the vaccination route on iNKT cell help to T and B cell responses for the first time in an antigen and agonist co-delivery setting. Intravenous administration of PLGA nanoparticles was mainly targeting liver and spleen where iNKT1 cells are abundant and induced the highest serum IFN-y levels, T cell cytotoxicity, and Th-1 type antibody responses. In comparison, after subcutaneous or intranodal injections, nanoparticles mostly drained or remained in regional lymph nodes where iNKT17 cells were abundant. After subcutaneous and intranodal injections, antigen-specific IgG2 c production was hampered and IFN-y production, as well as cytotoxic T cell responses, depended on sporadic systemic drainage. Therapeutic anti-tumor experiments also demonstrated a clear advantage of intravenous injection over intranodal or subcutaneous vaccinations. Moreover, tumor control could be further improved by PD-1 immune checkpoint blockade after intravenous vaccination, but not by intranodal vaccination. Anti PD-1 antibody combination mainly exerts its effect by prolonging the cytotoxicity of T cells. Nanovaccines also demonstrated synergism with anti-4-1BB agonistic antibody treatment in controlling tumor growth. We conclude that nanovaccines containing iNKT cell agonists shall be preferentially administered intravenously, to optimally reach cellular partners for inducing effective anti-tumor immune responses.

Recent advances in iNKT cell development

Recent studies suggest that murine invariant natural killer T (iNKT) cell development culminates in three terminally differentiated iNKT cell subsets denoted as NKT1, 2, and 17 cells. Although these studies corroborate the significance of the subset division model, less is known about the factors driving subset commitment in iNKT cell progenitors. In this review, we discuss the latest findings in iNKT cell development, focusing in particular on how T-cell receptor signal strength steers iNKT cell progenitors toward specific subsets and how early progenitor cells can be identified. In addition, we will discuss the essential factors for their sustenance and functionality. A picture is emerging wherein the majority of thymic iNKT cells are mature effector cells retained in the organ rather than developing precursors.

Selective effects of radiotherapy on viability and function of invariant natural killer T cells in vitro

BACKGROUND AND PURPOSE

Immunotherapies involving the adoptive transfer of ex vivo expanded autologous invariant natural killer (iNKT) cells are a potential option for cancer patients and are under investigation in clinical trials. Most cancer patients receive radiotherapy at some point during their treatment. We investigated the effects of therapeutic doses of radiation on the viability and function of human primary cultures of iNKT cells in vitro.

MATERIALS AND METHODS

iNKT cell lines generated from 6 healthy donors were subjected to therapeutically-relevant doses of radiation. Cell cycle arrest and cell death were assessed by flow cytometry. Double strand DNA breaks were analysed by measuring phosphorylated histone H2AX expression by fluorescence microscopy. Cytolytic degranulation, cytokine production and cytotoxicity by antigen-stimulated iNKT cells were assessed by flow cytometry.

RESULTS

Radiation inhibited viability of iNKT cells in a dose-dependent manner. Radiation caused double strand DNA breaks, which were rapidly repaired, and affected the cell cycle at high doses. Moderate doses of radiation did not inhibit degranulation or cytotoxicity by iNKT cells, but induced perforin expression and inhibited proliferation and interferon-γ production by surviving iNKT cells.

DISCUSSION

Exposure of iNKT cell to radiation can negatively affect their viability and function.

Liver X Receptors Regulate Cholesterol Metabolism and Immunity in Hepatic Nonparenchymal Cells

Excess dietary cholesterol intake and the dysregulation of cholesterol metabolism are associated with the pathogenesis and progression of nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, and fibrosis. Hepatic accumulation of free cholesterol induces activation of nonparenchymal cells, including Kupffer cells, macrophages, and hepatic stellate cells, which leads to persistent inflammation and fibrosis. The nuclear receptors liver X receptor α (LXRα) and LXRβ act as negative regulators of cholesterol metabolism through the induction of hepatocyte cholesterol catabolism, excretion, and the reverse cholesterol transport pathway. Additionally, LXRs exert an anti-inflammatory effect in immune cell types, such as macrophages. LXR activation suppresses acute hepatic inflammation that is mediated by Kupffer cells/macrophages. Acute liver injury, diet-induced steatohepatitis, and fibrosis are exacerbated by significant hepatic cholesterol accumulation and inflammation in LXR-deficient mice. Therefore, LXRs regulate hepatic lipid metabolism and immunity and they are potential therapeutic targets in the treatment of hepatic inflammation that is associated with cholesterol accumulation.

SLAM-SAP-Fyn: Old Players with New Roles in iNKT Cell Development and Function

Invariant natural killer T (iNKT) cells are a unique T cell lineage that develop in the thymus and emerge with a memory-like phenotype. Accordingly, following antigenic stimulation, they can rapidly produce copious amounts of Th1 and Th2 cytokines and mediate activation of several immune cells. Thus, it is not surprising that iNKT cells play diverse roles in a broad range of diseases. Given their pivotal roles in host immunity, it is crucial that we understand the mechanisms that govern iNKT cell development and effector functions. Over the last two decades, several studies have contributed to the current knowledge of iNKT cell biology and activity. Collectively, these studies reveal that the thymic development of iNKT cells, their lineage expansion, and functional properties are tightly regulated by a complex network of transcription factors and signaling molecules. While prior studies have clearly established the importance of the SLAM-SAP-Fyn signaling axis in iNKT cell ontogenesis, recent studies provide exciting mechanistic insights into the role of this signaling cascade in iNKT cell development, lineage fate decisions, and functions. Here we summarize the previous literature and discuss the more recent studies that guide our understanding of iNKT cell development and functional responses.

3,4-Dideoxy-3,3,4,4-tetrafluoro- and 4-OH epimeric 3-deoxy-3,3-difluoro-α-GalCer analogues: Synthesis and biological evaluation on human iNKT cells stimulation

iNKT cells recognize CD1d/α-galactosylceramide (α-GalCer) complexes via their invariant TCR receptor and stimulate the immune response. Many α-GalCer analogues have been investigated to interrogate this interaction. Following our previous work related to the modification of the hydrogen bond network between α-GalCer and CD1d, we have now focused our attention on the synthesis of 3-deoxy-3,3-difluoro- and 3,4-dideoxy-3,3,4,4-tetrafluoro-α-GalCer analogues, and studied their ability to stimulate human iNKT cells. In each case, deoxygenation at the indicated positions was accompanied by difluoro introduction in order to evaluate the resulting electronic effect on the stability of the ternary CD1d/Galcer/TCR complex which has been rationalized by modeling study. With deoxy-difluorination at the 3-position, the two epimeric 4-OH analogues were investigated to establish their capacity to compensate for the lack of the hydrogen bond donating group at the 3-position. The 3,4-dideoxytetrafluoro analogue was of interest to highlight the amide NH-bond hydrogen bond properties.

NKT Cells Coexpressing a GD2-Specific Chimeric Antigen Receptor and IL15 Show Enhanced In Vivo Persistence and Antitumor Activity against Neuroblastoma

PURPOSE

Vα24-invariant natural killer T cells (NKT) are attractive carriers for chimeric antigen receptors (CAR) due to their inherent antitumor properties and preferential localization to tumor sites. However, limited persistence of CAR-NKTs in tumor-bearing mice is associated with tumor recurrence. Here, we evaluated whether coexpression of the NKT homeostatic cytokine IL15 with a CAR enhances the in vivo persistence and therapeutic efficacy of CAR-NKTs.

EXPERIMENTAL DESIGN

Human primary NKTs were ex vivo expanded and transduced with CAR constructs containing an optimized GD2-specific single-chain variable fragment and either the CD28 or 4-1BB costimulatory endodomain, each with or without IL15 (GD2.CAR or GD2.CAR.15). Constructs that mediated robust CAR-NKT cell expansion were selected for further functional evaluation in vitro and in xenogeneic mouse models of neuroblastoma.

RESULTS

Coexpression of IL15 with either costimulatory domain increased CAR-NKT absolute numbers. However, constructs containing 4-1BB induced excessive activation-induced cell death and reduced numeric expansion of NKTs compared with respective CD28-based constructs. Further evaluation of CD28-based GD2.CAR and GD2.CAR.15 showed that coexpression of IL15 led to reduced expression levels of exhaustion markers in NKTs and increased multiround in vitro tumor cell killing. Following transfer into mice bearing neuroblastoma xenografts, GD2.CAR.15 NKTs demonstrated enhanced in vivo persistence, increased localization to tumor sites, and improved tumor control compared with GD2.CAR NKTs. Importantly, GD2.CAR.15 NKTs did not produce significant toxicity as determined by histopathologic analysis.

CONCLUSIONS

Our results informed selection of the CD28-based GD2.CAR.15 construct for clinical testing and led to initiation of a first-in-human CAR-NKT cell clinical trial (NCT03294954).

Natural killer T cell activation increases iNOS+CD206- M1 macrophage and controls the growth of solid tumor

Background

NKT cells play an important role in anti-tumor immunity. Alpha-galactosylceramide (α-GalCer), a synthetic glycolipid is presented to natural killer T (NKT) cells by most antigen-presenting cells through CD1d molecules leading to activation of NKT cells. However, the precise mechanisms of how α-GalCer-activated NKT regulate the polarization of the macrophages and effector T cells in the solid tumor are not studied adequately.

Methods

We induced solid tumor in C57BL/6 mice by subcutaneous injection of B16F10 cell line (1 X 10⁶ cells) and monitored the tumor growth. Animals were given an intraperitoneal injection of α-GalCer (2 μg/injection) in 200 μl PBS on day + 1, + 5, + 10, + 15, and + 20 (with respect to tumor cell injection). Immune cells were characterized using flow cytometry and immunofluorescence staining. NK cells, Gr1⁺ cells, and F4/80⁺ macrophages in the mice were depleted by intravenous injection of cell-specific antibodies. Statistical analysis was performed using Student’s t-test or one-way ANOVA.

Results

Our results showed that intratumoral NKT cells have a lower frequency of CD69, CD25, CD122, and IFN-γR expression; produced less inflammatory cytokines such as IFN-γ, TNF-α, and GM-CSF; higher frequency CD62L⁺ NKT cells; and also showed reduced proliferation as compared to the splenic NKT cells. Mice treated with α-GalCer showed a significantly increased frequency of IFN-γ-producing NKT cells, CD8⁺ T cells, and effector Th1 cells. Depletion of NK cells in α-GalCer-treated mice showed a lower frequency of IFN-γ-producing CD4⁺ and CD8⁺ T cells in the tumor and prevented the α-GalCer-induced tumor growth. NKT cell activation with α-GalCer treatment significantly increased the iNOS⁺CD206⁻ M1-macrophages and reduced the iNOS⁻CD206⁺ M2-macrophages in the spleen and tumor, and depletion of F4/80⁺ macrophages prevented the α-GalCer-induced reduction in the tumor growth.

Conclusions

We showed that activation of NKT cell with α-GalCer modulates the frequency of M1-macrophages and effector Th1 cells in the secondary lymphoid tissues and tumor microenvironment and inhibit tumor growth. The finding suggests that activation of NKT cells with α-GalCer may provide an effective anti-cancer outcome.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0697-7) contains supplementary material, which is available to authorized users.

Impacts of the MHC class I-like XNC10 and innate-like T cells on tumor tolerance and rejection in the amphibian Xenopus

The conditions that lead to antitumor or protumor functions of natural killer T (NKT) cells against mammalian tumors are only partially understood. Therefore, insights into the evolutionary conservation of NKT and their analogs-innate-like T (iT) cells-may reveal factors that contribute to tumor eradication. As such, we investigated the amphibian Xenopus laevis iT cells and interacting MHC class I-like (XNC or mhc1b.L) genes against ff-2 thymic lymphoid tumors. Upon ff-2 intraperitoneal transplantation into syngeneic tadpoles, two iT cell subsets iVα6 and iVα22, characterized by an invariant T-cell receptor α chain rearrangement (Vα6-Jα1.43 and Vα22-Jα1.32 respectively), were recruited to the peritoneum, concomitant with a decreased level of these transcripts in the spleen and thymus. To address the hypothesize that different iT cell subsets have distinct, possibly opposing, roles upon ff-2 tumor challenge, we determined whether ff-2 tumor growth could be manipulated by impairing Vα6 iT cells or by deleting their restricting element, the XNC gene, XNC10 (mhc1b10.1.L), on ff-2 tumors. Accordingly, the in vivo depletion of Vα6 iT cells using XNC10-tetramers enhanced tumor growth, indicating Vα6 iT cell-mediated antitumor activities. However, XNC10-deficient transgenic tadpoles that also lack Vα6 iT cells were resistant to ff-2 tumors, uncovering a potential new function of XNC10 besides Vα6 iT cell development. Furthermore, the CRISPR/Cas9-mediated knockout of XNC10 in ff-2 tumors broke the immune tolerance. Together, our findings demonstrate the relevance of XNC10/iT cell axis in controlling Xenopus tumor tolerance or rejection.

Precision oncology: myth or reality?

Cancer incidence rates are growing at an alarming pace pressing for the development of innovative personalized approaches to treating this disease. The absence of clinical symptoms in the early stages delays the onset of adequate treatment. Traditional therapies are not always as effective as they should be and do not guarantee long-lasting relapse-free survival. Metastatic cancers pose a particular challenge to healthcare professionals. This review touches upon the immunologic mechanisms underlying the development of malignancies, talks about conventional and innovative therapeutic modalities, such as targeted, gene or specific immunotherapies, and analyzes the literature on the use of different approaches that form a basis for precision oncology.

T Cell Receptor Expression Timing and Signal Strength in the Functional Differentiation of Invariant Natural Killer T Cells

The CD1d-restricted Vα14 invariant NKT (iNKT) cell lineage in mice (Vα24 in humans) represents an evolutionary conserved innate-like immune cell type that recognizes glycolipid antigens. Because of their unique ability to promptly secrete copious amounts of both pro-inflammatory and anti-inflammatory cytokines, typically produced by different T helper cell types, iNKT cells are implicated in the regulation of various pathologic conditions such as infection, allergy, autoimmune disease, maintenance of transplantation tolerance, and cancer. This striking multifaceted role in immune regulation is correlated with the presence of multiple functionally distinct iNKT cell subsets that can be distinguished based on the expression of characteristic surface markers and transcription factors. However, to date it, remains largely unresolved how this puzzling diversity of iNKT cell functional subsets emerges and what factors dictate the type of effector cell differentiation during the thymic differentiation considering the mono-specific nature of their T cell receptor (TCR) and their selecting molecule CD1d. Here, we summarize recent findings focusing on the role of TCR-mediated signaling and discuss possible mechanisms that may influence the sub-lineage choice of iNKT cells.

Beyond CAR T Cells: Other Cell-Based Immunotherapeutic Strategies Against Cancer

Background: Chimeric antigen receptor (CAR)-modified T cells have successfully harnessed T cell immunity against malignancies, but they are by no means the only cell therapies in development for cancer.

Main Text Summary: Systemic immunity is thought to play a key role in combatting neoplastic disease; in this vein, genetic modifications meant to explore other components of T cell immunity are being evaluated. In addition, other immune cells—from both the innate and adaptive compartments—are in various stages of clinical application. In this review, we focus on these non-CAR T cell immunotherapeutic approaches for malignancy. The first section describes engineering T cells to express non-CAR constructs, and the second section describes other gene-modified cells used to target malignancy.

Conclusions: CAR T cell therapies have demonstrated the clinical benefits of harnessing our body's own defenses to combat tumor cells. Similar research is being conducted on lesser known modifications and gene-modified immune cells, which we highlight in this review.

Novel thioglycoside analogs of α-galactosylceramide stimulate cytotoxicity and preferential Th1 cytokine production by human invariant natural killer T cells

Invariant natural killer T (iNKT) cells recognize glycolipid antigens bound to CD1d molecules on antigen-presenting cells. Therapeutic activation of iNKT cells with the xenogeneic glycolipid α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in murine models, but clinical trials using α-GalCer-stimulated human iNKT cells have shown limited efficacy. We synthesized a series of thioglycoside analogs of α-GalCer with different substituents to the galactose residue and found that two of these compounds, XZ7 and XZ11, bound to CD1d-transfected HeLa cells and activated lines of expanded human iNKT cells. Both compounds stimulated cytolytic degranulation by iNKT cells and while XZ7 preferentially stimulated the production of the antitumor cytokine interferon-γ (IFN-γ), XZ11 preferentially stimulated interleukin-4 (IL-4) production. This biased T helper type 1 effector profile of XZ7 was also evident when iNKT were stimulated with dendritic cells presenting this glycolipid. Separate analysis of the responses of CD4+, CD8α+ and CD4-CD8- iNKT cells indicated that XZ7 preferentially activated CD8α+ iNKT cells, and to a lesser degree, CD4-CD8- iNKT cells. The partial agonist effect of glycolipid XZ7, inducing cytotoxicity and IFN-γ production but not IL-4 production, indicates that specific protumour activities of iNKT cells can be abolished, while preserving their antitumor activities, by introducing structural modifications to α-GalCer. Since XZ7 was much less potent than α-GalCer as an iNKT cell agonist, it is unlikely to be superior to α-GalCer as a therapeutic agent for cancer, but may serve as a parent compound for developing more potent structural analogs.

NKT cells - New players in CAR cell immunotherapy?

Low levels of peripheral blood natural killer T (NKT) cells in cancer patients and a favorable outcome associated with a high number of tumor-infiltrating NKT cells demonstrated in several studies indicated the important role of these immune cells in the antitumor response. With effective antitumor immunity via direct tumor lysis, cytokine modulation of effector cells and regulation of immunosuppressive cells, type I NKT cells display interesting features/properties for the rapidly developing chimeric antigen receptor (CAR) technology. Due to their restriction to the monomorphic HLA-like molecule CD1d, but not to the polymorphic human leukocyte antigen (HLA), NKT CAR cells show potential for enabling autologous and allogeneic/off-the-shelf cancer immunotherapy. Promising results were obtained in preclinical NKT CAR cell studies, but clinical trials have not yet been conducted. In this review, we summarize the biological features of NKT cells, their role in antitumor immunity and recent advances in the development of NKT CAR cells.

Regulation of the terminal maturation of iNKT cells by mediator complex subunit 23

Invariant natural killer T cells (iNKT cells) are a specific subset of T cells that recognize glycolipid antigens and upon activation rapidly exert effector functions. This unique function is established during iNKT cell development; the detailed mechanisms of this process, however, remain to be elucidated. Here the authors show that deletion of the mediator subunit Med23 in CD4⁺CD8⁺ double positive (DP) thymocytes completely blocks iNKT cell development at stage 2. This dysregulation is accompanied by a bias in the expression of genes related to the regulation of transcription and metabolism, and functional impairment of the cells including the loss of NK cell characteristics, reduced ability to secrete cytokines and attenuated recruitment capacity upon activation. Moreover, Med23-deficient iNKT cells exhibit impaired anti-tumor activity. Our study identifies Med23 as an essential transcriptional regulator that controls iNKT cell differentiation and terminal maturation.

Invariant Natural Killer T cells (iNKT) rapidly exert effector functions upon activation, but the mechanisms of their functional maturation remain to be determined. Here, Xu and colleagues show that the mediator subunit Med23 is a transcriptional regulator controlling iNKT cell terminal maturation.

Tissue-Specific Roles of NKT Cells in Tumor Immunity

NKT cells are an unusual population of T cells recognizing lipids presented by CD1d, a non-classical class-I-like molecule, rather than peptides presented by conventional MHC molecules. Type I NKT cells use a semi-invariant T cell receptor and almost all recognize a common prototype lipid, α-galactosylceramide (α-GalCer). Type II NKT cells are any lipid-specific CD1d-restricted T cells that use other receptors and generally don't recognize α-GalCer. They play important regulatory roles in immunity, including tumor immunity. In contrast to type I NKT cells that most have found to promote antitumor immunity, type II NKT cells suppress tumor immunity and the two subsets cross-regulate each other, forming an immunoregulatory axis. They also can promote other regulatory cells including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), and can induce MDSCs to secrete TGF-β, one of the most immunosuppressive cytokines known. In some tumors, both Tregs and type II NKT cells can suppress immunosurveillance, and the balance between these is determined by a type I NKT cell. We have also seen that regulation of tumor immunity can depend on the tissue microenvironment, so the same tumor in the same animal in different tissues may be regulated by different cells, such as type II NKT cells in the lung vs Tregs in the skin. Also, the effector T cells that protect those sites when Tregs are removed do not always act between tissues even in the same animal. Thus, metastases may require different immunotherapy from primary tumors. Newly improved sulfatide-CD1d tetramers are starting to allow better characterization of the elusive type II NKT cells to better understand their function and control it to overcome immunosuppression.