Tec family kinases Itk and Rlk / Txk in T lymphocytes: cross-regulation of cytokine production and T-cell fates

Identifying allergic-rhinitis-associated genes with random-walk-based method in PPI network

Allergic rhinitis is a common allergic disease with a complex pathogenesis and many unresolved issues. Studies have shown that the incidence of allergic rhinitis is closely related to genetic factors, and research on the related genes could help further understand its pathogenesis and develop new treatment methods. In this study, 446 allergic rhinitis-related genes were obtained on the basis of the DisGeNET database. The protein-protein interaction network was searched using the random-walk-with-restart algorithm with these 446 genes as seed nodes to assess the linkages between other genes and allergic rhinitis. Then, this result was further examined by three screening tests, including permutation, interaction, and enrichment tests, which aimed to pick up genes that have strong and special associations with allergic rhinitis. 52 novel genes were finally obtained. The functional enrichment test confirmed their relationships to the biological processes and pathways related to allergic rhinitis. Furthermore, some genes were extensively analyzed to uncover their special or latent associations to allergic rhinitis, including IRAK2 and MAPK, which are involved in the pathogenesis of allergic rhinitis and the inhibition of allergic inflammation via the p38-MAPK pathway, respectively. The new found genes may help the following investigations for understanding the underlying molecular mechanisms of allergic rhinitis and developing effective treatments.

Unrestrained cleavage of Roquin-1 by MALT1 induces spontaneous T cell activation and the development of autoimmunity

Constitutive activation of the MALT1 paracaspase in conventional T cells of Malt1TBM/TBM (TRAF6 Binding Mutant = TBM) mice causes fatal inflammation and autoimmunity, but the involved targets and underlying molecular mechanisms are unknown. We genetically rendered a single MALT1 substrate, the RNA-binding protein (RBP) Roquin-1, insensitive to MALT1 cleavage. These Rc3h1Mins/Mins mice showed normal immune homeostasis. Combining Rc3h1Mins/Mins alleles with those encoding for constitutively active MALT1 (TBM) prevented spontaneous T cell activation and restored viability of Malt1TBM/TBM mice. Mechanistically, we show how antigen/MHC recognition is translated by MALT1 into Roquin cleavage and derepression of Roquin targets. Increasing T cell receptor (TCR) signals inactivated Roquin more effectively, and only high TCR strength enabled derepression of high-affinity targets to promote Th17 differentiation. Induction of experimental autoimmune encephalomyelitis (EAE) revealed increased cleavage of Roquin-1 in disease-associated Th17 compared to Th1 cells in the CNS. T cells from Rc3h1Mins/Mins mice did not efficiently induce the high-affinity Roquin-1 target IκBNS in response to TCR stimulation, showed reduced Th17 differentiation, and Rc3h1Mins/Mins mice were protected from EAE. These data demonstrate how TCR signaling and MALT1 activation utilize graded cleavage of Roquin to differentially regulate target mRNAs that control T cell activation and differentiation as well as the development of autoimmunity.

Low RNA stability signifies increased post-transcriptional regulation of cell identity genes

Cell identity genes are distinct from other genes with respect to the epigenetic mechanisms to activate their transcription, e.g. by super-enhancers and broad H3K4me3 domains. However, it remains unclear whether their post-transcriptional regulation is also unique. We performed a systematic analysis of transcriptome-wide RNA stability in nine cell types and found that unstable transcripts were enriched in cell identity-related pathways while stable transcripts were enriched in housekeeping pathways. Joint analyses of RNA stability and chromatin state revealed significant enrichment of super-enhancers and broad H3K4me3 domains at the gene loci of unstable transcripts. Intriguingly, the RNA m6A methyltransferase, METTL3, preferentially binds to chromatin at super-enhancers, broad H3K4me3 domains and their associated genes. METTL3 binding intensity is positively correlated with RNA m6A methylation and negatively correlated with RNA stability of cell identity genes, probably due to co-transcriptional m6A modifications promoting RNA decay. Nanopore direct RNA-sequencing showed that METTL3 knockdown has a stronger effect on RNA m6A and mRNA stability for cell identity genes. Our data suggest a run-and-brake model, where cell identity genes undergo both frequent transcription and fast RNA decay to achieve precise regulation of RNA expression.

Inhibition of ITK Signaling Causes Amelioration in Sepsis-Associated Neuroinflammation and Depression-like State in Mice

Sepsis affects millions of people worldwide and is associated with multiorgan dysfunction that is a major cause of increased morbidity and mortality. Sepsis is associated with several morbidities, such as lung, liver, and central nervous system (CNS) dysfunction. Sepsis-associated CNS dysfunction usually leads to several mental problems including depression. IL-17A is one of the crucial cytokines that is expressed and secreted by Th17 cells. Th17 cells are reported to be involved in the pathogenesis of depression and anxiety in humans and animals. One of the protein tyrosine kinases that plays a key role in controlling the development/differentiation of Th17 cells is ITK. However, the role of ITK in sepsis-associated neuroinflammation and depression-like symptoms in mice has not been investigated earlier. Therefore, this study investigated the efficacy of the ITK inhibitor, BMS 509744, in sepsis-linked neuroinflammation (ITK, IL-17A, NFkB, iNOS, MPO, lipid peroxides, IL-6, MCP-1, IL-17A) and a battery of depression-like behavioral tests, such as sucrose preference, tail suspension, and the marble burying test. Further, the effect of the ITK inhibitor on anti-inflammatory signaling (Foxp3, IL-10, Nrf2, HO-1, SOD-2) was assessed in the CNS. Our data show that sepsis causes increased ITK protein expression, IL-17A signaling, and neuroinflammatory mediators in the CNS that are associated with a depression-like state in mice. ITK inhibitor-treated mice with sepsis show attenuated IL-17A signaling, which is associated with the upregulation of IL-10/Nrf2 signaling and the amelioration of depression-like symptoms in mice. Our data show, for the first time, that the ITK inhibition strategy may counteract sepsis-mediated depression through a reduction in IL-17A signaling in the CNS.

Analyses of lncRNAs, circRNAs, and the Interactions between ncRNAs and mRNAs in Goat Submandibular Glands Reveal Their Potential Function in Immune Regulation

As part of one of the main ruminants, goat salivary glands hardly secrete digestive enzymes, but play an important role in immunity. The immune function of goat salivary glands significantly changes with age, while the expression profile and specific function of non-coding RNA during this process are unknown. In this study, transcriptome sequencing was performed on submandibular gland (SMG) tissues of 1-month-old, 12-month-old, and 24-month-old goats, revealing the expression patterns of lncRNA and circRNA at different ages. A total of 369 lncRNAs and 1699 circRNAs were found to be differentially expressed. Functional enrichment analyses showed that the lncRNA regulated target mRNAs and circRNA host genes were significantly enriched in immune-related GO terms and pathways. CeRNA network analysis showed that the key differentially expressed circRNAs and lncRNAs mainly regulate the key immune-related genes ITGB2, LCP2, PTPRC, SYK, and ZAP70 through competitive binding with miR-141-x, miR-29-y, and chi-miR-29b-3p, thereby affecting the natural killer cell-mediated cytotoxicity pathway, the T cell receptor signaling pathway, and other immune-related pathways. It should be noted that the expression of key circRNAs, lncRNAs, and key immune-related genes in goat SMGs decreased significantly with the growth of the goat. This is the first reporting of lncRNAs, circRNAs, and ceRNA network regulation in goat SMGs. Our study contributes to the knowledge of changes in the expression of non-coding RNAs during SMG development in goats and provides new insights into the relationship between non-coding RNAs and salivary gland immune function in goats.

Targeting Ibrutinib to Tumor-Infiltrating T Cells with a Sialic Acid Conjugate-Modified Phospholipid Complex for Improved Tumor Immunotherapy

Immune checkpoint blockade (ICB) treatment for the clinical therapy of numerous malignancies has attracted widespread attention in recent years. Despite being a promising treatment option, developing complementary strategies to enhance the proportion of patients benefiting from ICB therapy remains a formidable challenge because of the complexity of the tumor microenvironment. Ibrutinib (IBR), a covalent inhibitor of Bruton's tyrosine kinase (BTK), has been approved as a clinical therapy for numerous B-cell malignancies. IBR also irreversibly inhibits interleukin-2 inducible T cell kinase (ITK), an essential enzyme in Th2-polarized T cells that participates in tumor immunosuppression. Ablation of ITK by IBR can elicit Th1-dominant antitumor immune responses and potentially enhance the efficacy of ICB therapy in solid tumors. However, its poor solubility and rapid clearance in vivo restrict T cell targetability and tumor accumulation by IBR. A sialic acid derivative-modified nanocomplex (SA-GA-OCT@PC) has been reported to improve the efficacy of IBR-mediated combination immunotherapy in solid tumors. In vitro and in vivo experiments showed that SA-GA-OCT@PC effectively accumulated in tumor-infiltrating T cells mediated by Siglec-E and induced Th1-dominant antitumor immune responses. SA-GA-OCT@PC-mediated combination therapy with PD-L1 blockade agents dramatically suppressed tumor growth and inhibited tumor relapse in B16F10 melanoma mouse models. Overall, the combination of the SA-modified nanocomplex platform and PD-L1 blockade offers a treatment opportunity for IBR in solid tumors, providing novel insights for tumor immunotherapy.

Co-Stimulatory Receptor Signaling in CAR-T Cells

T cell engineering strategies have emerged as successful immunotherapeutic approaches for the treatment of human cancer. Chimeric Antigen Receptor T (CAR-T) cell therapy represents a prominent synthetic biology approach to re-direct the specificity of a patient's autologous T cells toward a desired tumor antigen. CAR-T therapy is currently FDA approved for the treatment of hematological malignancies, including subsets of B cell lymphoma, acute lymphoblastic leukemia (ALL) and multiple myeloma. Mechanistically, CAR-mediated recognition of a tumor antigen results in propagation of T cell activation signals, including a co-stimulatory signal, resulting in CAR-T cell activation, proliferation, evasion of apoptosis, and acquisition of effector functions. The importance of including a co-stimulatory domain in CARs was recognized following limited success of early iteration CAR-T cell designs lacking co-stimulation. Today, all CAR-T cells in clinical use contain either a CD28 or 4-1BB co-stimulatory domain. Preclinical investigations are exploring utility of including additional co-stimulatory molecules such as ICOS, OX40 and CD27 or various combinations of multiple co-stimulatory domains. Clinical and preclinical evidence implicates the co-stimulatory signal in several aspects of CAR-T cell therapy including response kinetics, persistence and durability, and toxicity profiles each of which impact the safety and anti-tumor efficacy of this immunotherapy. Herein we provide an overview of CAR-T cell co-stimulation by the prototypical receptors and discuss current and emerging strategies to modulate co-stimulatory signals to enhance CAR-T cell function.

Interleukin-2 inducible T cell kinase (ITK) may participate in the anti-bacterial immune response of Nile tilapia via regulating T-cell activation

Interleukin-2 inducible T cell kinase (ITK) plays a predominant role in the T-cell receptor (TCR) signaling cascade to ensure valid T-cell activation and function. Nevertheless, whether it regulates T-cell response of early vertebrates remains unknown. Herein, we investigated the involvement of ITK in the lymphocyte-mediated adaptive immune response, and its regulation to T-cell activation in the Nile tilapia Oreochromis niloticus. Both sequence and structure of O. niloticus ITK (OnITK) were remarkably conserved with its homologues from other vertebrates, implying its potential conserved function. OnITK mRNA was extensively expressed in lymphoid-related tissues, and with the relative highest level in peripheral blood. Once Nile tilapia was infected by Edwardsiella piscicida, OnITK in splenic lymphocytes was significantly up-regulated on 7-day post infection at both transcription and translation levels, suggesting that OnITK might involve in the primary adaptive immune response of teleost. Furthermore, upon splenic lymphocytes were stimulated by T-cell specific mitogen PHA, OnITK mRNA and protein levels were dramatically elevated. More importantly, treatment of splenic lymphocytes with specific inhibitor significantly crippled OnITK expression, which in turn impaired the inducible expression of T-cell activation markers IFN-γ, IL-2 and CD122, indicating the critical roles of ITK in regulating T-cell activation of Nile tilapia. Taken together, our results suggest that ITK takes part in the lymphocyte-mediated adaptive immunity of tilapia, and is indispensable for T-cell activation of teleost. Our findings thus provide novel evidences for understanding the mechanism regulating T-cell immunity of early vertebrates, as well as the evolution of adaptive immune system.

Identification of Immune-Related Key Genes as Potential Diagnostic Biomarkers of Sepsis in Children

Objective

The pathogenesis of sepsis is still unclear due to its complexity, especially in children. This study aimed to analyse the immune microenvironment and regulatory networks related to sepsis in children at the molecular level and to identify key immune-related genes to provide a new basis for the early diagnosis of sepsis.

Methods

The GSE145227 and GSE26440 datasets were downloaded from the Gene Expression Omnibus. The analyses included differentially expressed genes (DEGs), functional enrichment, immune cell infiltration, the competing endogenous RNA (ceRNA) interaction network, weighted gene coexpression network analysis (WGCNA), protein–protein interaction (PPI) network, key gene screening, correlation of sepsis molecular subtypes/immune infiltration with key gene expression, the diagnostic capabilities of key genes, and networks describing the interaction of key genes with transcription factors and small-molecule compounds. Finally, real-time quantitative PCR (RT–qPCR) was performed to verify the expression of key genes.

Results

A total of 236 immune-related DEGs, most of which were enriched in immune-related biological functions, were found. Further analysis of immune cell infiltration showed that M0 macrophages and neutrophils infiltrated more in the sepsis group, while fewer activated memory CD4⁺ T cells, resting memory CD4⁺ T cells, and CD8⁺ T cells did. The interaction network of ceRNA was successfully constructed. Six key genes (FYN, FBL, ATM, WDR75, FOXO1 and ITK) were identified by WGCNA and PPI analysis. We found strong associations between key genes and constructed septic molecular subtypes or immune cell infiltration. Receiver operating characteristic analysis showed that the area under the curve values of the key genes for diagnosis were all greater than 0.84. Subsequently, we successfully constructed an interaction network of key genes and transcription factors/small-molecule compounds. Finally, the key genes in the samples were verified by RT–qPCR.

Conclusion

Our results offer new insights into the pathogenesis of sepsis in children and provide new potential diagnostic biomarkers for the disease.

Three US Food and Drug Administration-approved therapies for chronic GVHD

Chronic graft-versus-host disease (cGVHD) is a major immunologic complication of allogeneic hematopoietic cell transplantation. cGVHD involves multiple organs, reduces quality of life, and often requires prolonged therapy with glucocorticoids, causing severe side effects. After 4 decades of testing multiple therapeutic approaches, ibrutinib, belumosudil, and ruxolitinib were US Food and Drug Administration approved for cGVHD in the last 4 years. Here we put a spotlight on their mechanisms of action, studies that led to approval, and their future role in cGVHD.

Kinase Inhibition as Treatment for Acute and Chronic Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative therapy for patients suffering from hematological malignancies via the donor immune system driven graft-versus-leukemia effect. However, the therapy is mainly limited by severe acute and chronic graft-versus-host disease (GvHD), both being life-threatening complications after allo-HCT. GvHD develops when donor T cells do not only recognize remaining tumor cells as foreign, but also the recipient’s tissue, leading to a severe inflammatory disease. Typical GvHD target organs include the skin, liver and intestinal tract. Currently all approved strategies for GvHD treatment are immunosuppressive therapies, with the first-line therapy being glucocorticoids. However, therapeutic options for glucocorticoid-refractory patients are still limited. Novel therapeutic approaches, which reduce GvHD severity while preserving GvL activity, are urgently needed. Targeting kinase activity with small molecule inhibitors has shown promising results in preclinical animal models and clinical trials. Well-studied kinase targets in GvHD include Rho-associated coiled-coil-containing kinase 2 (ROCK2), spleen tyrosine kinase (SYK), Bruton’s tyrosine kinase (BTK) and interleukin-2-inducible T-cell kinase (ITK) to control B- and T-cell activation in acute and chronic GvHD. Janus Kinase 1 (JAK1) and 2 (JAK2) are among the most intensively studied kinases in GvHD due to their importance in cytokine production and inflammatory cell activation and migration. Here, we discuss the role of kinase inhibition as novel treatment strategies for acute and chronic GvHD after allo-HCT.

Role of ITK signaling in acute kidney injury in mice: Amelioration of acute kidney injury associated clinical parameters and attenuation of inflammatory transcription factor signaling in CD4+ T cells by ITK inhibition

Acute kidney injury (AKI) is a world-wide health problem and linked with increased risk of morbidity/mortality in hospitalized patients and its incidence has been on the rise in the last few decades. AKI is characterized by renal tubular injury which results from interactions between bacterial products and host immune responses which manifests as a rapid deterioration in renal function. Immune system dysfunction induced by sepsis plays a crucial role in AKI through activation of multiple immune cells of both innate and adaptive origin. These cells release pro-inflammatory cytokines such as IL-6, IL-17A, IFN-γ, and reactive oxygen metabolites. Adaptive immune cells, especially T cells also participate in the amplification of renal inflammation through release of pro-inflammatory cytokines such as IL-17A, IFN-γ, TNF-α, and IL-10. Non-receptor protein tyrosine kinases such as ITK play crucial role in T cell through modulation of key downstream molecules such as PLCγ, STAT3, NFkB, NFATc1, and p-38MAPK. However, it has not been explored in CD4+ T cells during AKI. Therefore, this study investigated the effect of ITK inhibitor on AKI linked clinical parameters (serum BUN, creatinine and renal histopathology), downstream signaling molecules in CD4+ T cells (PLCγ, STAT3, NFkB, and NFATc1), Th1/Th2/Treg cell markers (IL-17A, TNF-α, and IL-10), and neutrophil-mediated oxidative inflammation (MPO/carbonyl/nitrotyrosine formation) in mice. Our data exhibit elevated p-ITK levels in CD4+ T cells which is associated with renal dysfunction and elevated Th1/Th17/neutrophilic responses. Blockade of ITK signaling resulted in ameliorated of AKI associated biochemical; parameters through downregulation in transcription signaling in CD4+ T cells and Th1/Th17 immune responses. Therefore, this report suggests that ITK inhibition could be an effective strategy to halt renal dysfunction associated with AKI.

Novel mouse model resistant to irreversible BTK inhibitors: a tool identifying new therapeutic targets and side effects

Pharmacological inhibitors of Bruton tyrosine kinase (BTK) have revolutionized treatment of B-lymphocyte malignancies and show great promise for dampening autoimmunity. The predominant BTK inhibitors tether irreversibly by covalently binding to cysteine 481 in the BTK catalytic domain. Substitution of cysteine 481 for serine (C481S) is the most common mechanism for acquired drug resistance. We generated a novel C481S knock-in mouse model and, using a battery of tests, no overt B-lymphocyte phenotype was found. B lymphocytes from C481S animals were resistant to irreversible, but sensitive to reversible, BTK inhibitors. In contrast, irreversible inhibitors equally impaired T-lymphocyte activation in mice, mimicking the effect of treatment in patients. This demonstrates that T-lymphocyte blockage is independent of BTK. We suggest that the C481S knock-in mouse can serve as a useful tool for the study of BTK-independent effects of irreversible inhibitors, allowing for the identification of novel therapeutic targets and pinpointing potential side effects.

TH2/TH1 Shift Under Ibrutinib Treatment in Chronic Lymphocytic Leukemia

Ibrutinib may revert the T-helper (Th)2 polarization observed in chronic lymphocytic leukemia (CLL) by targeting the IL-2-inducible kinase, that shows a significant homology with the Bruton tyrosine kinase. In the front-line GIMEMA LLC1114 trial (ibrutinib+rituximab for 6 months, followed by ibrutinib maintenance), we investigated the modulation of T-cell cytokine production in 208 peripheral blood paired samples from 71 CLL patients: 71 samples prior to treatment (Day 0, D0) and at day +14 (D14; n=50), at month +8 (M8; 30), +12 (M12; 25), +18 (M18; 22) and +24 (M24; 10) of treatment. We documented a progressive decrease of CD3+CD4+IL-4+ T cells (Th2), that was significant at M8 and at M12 (p=0.019, p=0.002), a relative increase in the CD3+CD4+IFNγ+ T cells (Th1) and a decrease of CD3+CD4+IL-17+ (Th17) cells that was maintained up to M18 (M8 vs D0 p=0.003, M12 vs D0 p=0.003, M18 vs D0 p=0.004) of ibrutinib treatment. The Th2/Th1 ratio significantly decreased already after 14 days of treatment and was maintained thereafter (D14 vs D0 p=0.037, M8 vs D0 p=0.001, M12 vs D0 p=0.005, M18 vs D0 p=0.002). The Th2/Th1 modulation over time was significant only among patients with unmutated IGHV. The Th2/Th1 ratio below a cut-off of 0.088 at M8 was associated with the achievement of a complete response (CR) (p=0.016). Ibrutinib may shape the CLL T-cell profile, limiting Th2 activation and inducing a shift in the Th2/Th1 ratio. The association between the Th2/Th1 ratio decrease and the CR achievement suggests the in vivo generation of a potential host anti-tumor immune activation induced by ibrutinib.

The DEL-1/β3 integrin axis promotes regulatory T cell responses during inflammation resolution

FOXP3+CD4+ regulatory T cells (Tregs) are critical for immune homeostasis and respond to local tissue cues, which control their stability and function. We explored here whether developmental endothelial locus-1 (DEL-1), which, like Tregs, increases during resolution of inflammation, promotes Treg responses. DEL-1 enhanced Treg numbers and function at barrier sites (oral and lung mucosa). The underlying mechanism was dissected using mice lacking DEL-1 or expressing a point mutant thereof, or mice with T cell-specific deletion of the transcription factor RUNX1, identified by RNA sequencing analysis of the DEL-1-induced Treg transcriptome. Specifically, through interaction with αvβ3 integrin, DEL-1 promoted induction of RUNX1-dependent FOXP3 expression and conferred stability of FOXP3 expression upon Treg restimulation in the absence of exogenous TGF-β1. Consistently, DEL-1 enhanced the demethylation of the Treg-specific demethylated region (TSDR) in the mouse Foxp3 gene and the suppressive function of sorted induced Tregs. Similarly, DEL-1 increased RUNX1 and FOXP3 expression in human conventional T cells, promoting their conversion into induced Tregs with increased TSDR demethylation, enhanced stability, and suppressive activity. We thus uncovered a DEL-1/αvβ3/RUNX1 axis that promotes Treg responses at barrier sites and offers therapeutic options for modulating inflammatory/autoimmune disorders.

CD28 Costimulatory Domain-Targeted Mutations Enhance Chimeric Antigen Receptor T-cell Function

An obstacle to the development of chimeric antigen receptor (CAR) T cells is the limited understanding of CAR T-cell biology and the mechanisms behind their antitumor activity. We and others have shown that CARs with a CD28 costimulatory domain drive high T-cell activation, which leads to exhaustion and shortened persistence. This work led us to hypothesize that by incorporating null mutations of CD28 subdomains (YMNM, PRRP, or PYAP), we could optimize CAR T-cell costimulation and enhance function. In vivo, we found that mice given CAR T cells with only a PYAP CD28 endodomain had a significant survival advantage, with 100% of mice alive after 62 days compared with 50% for mice with an unmutated endodomain. We observed that mutant CAR T cells remained more sensitive to antigen after ex vivo antigen and PD-L1 stimulation, as demonstrated by increased cytokine production. The mutant CAR T cells also had a reduction of exhaustion-related transcription factors and genes such as Nfatc1, Nr42a, and Pdcd1 Our results demonstrated that CAR T cells with a mutant CD28 endodomain have better survival and function. This work allows for the development of enhanced CAR T-cell therapies by optimizing CAR T-cell costimulation.

New Approaches for the Treatment of Chronic Graft-Versus-Host Disease: Current Status and Future Directions

Chronic graft-versus-host disease (cGvHD) is a severe complication of allogeneic hematopoietic stem cell transplantation that affects various organs leading to a reduced quality of life. The condition often requires enduring immunosuppressive therapy, which can also lead to the development of severe side effects. Several approaches including small molecule inhibitors, antibodies, cytokines, and cellular therapies are now being developed for the treatment of cGvHD, and some of these therapies have been or are currently tested in clinical trials. In this review, we discuss these emerging therapies with particular emphasis on tyrosine kinase inhibitors (TKIs). TKIs are a class of compounds that inhibits tyrosine kinases, thereby preventing the dissemination of growth signals and activation of key cellular proteins that are involved in cell growth and division. Because they have been shown to inhibit key kinases in both B cells and T cells that are involved in the pathophysiology of cGvHD, TKIs present new promising therapeutic approaches. Ibrutinib, a Bruton tyrosine kinase (Btk) inhibitor, has recently been approved by the Food and Drug Administration (FDA) in the United States for the treatment of adult patients with cGvHD after failure of first-line of systemic therapy. Also, Janus Associated Kinases (JAK1 and JAK2) inhibitors, such as itacitinib (JAK1) and ruxolitinib (JAK1 and 2), are promising in the treatment of cGvHD. Herein, we present the current status and future directions of the use of these new drugs with particular spotlight on their targeting of specific intracellular signal transduction cascades important for cGvHD, in order to shed some light on their possible mode of actions.

Identification of Potential Biomarkers and Immune Features of Sepsis Using Bioinformatics Analysis

Sepsis remains a major global concern and is associated with high mortality and morbidity despite improvements in its management. Markers currently in use have shortcomings such as a lack of specificity and failures in the early detection of sepsis. In this study, we aimed to identify key genes involved in the molecular mechanisms of sepsis and search for potential new biomarkers and treatment targets for sepsis using bioinformatics analyses. Three datasets (GSE95233, GSE57065, and GSE28750) associated with sepsis were downloaded from the public functional genomics data repository Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified using R packages (Affy and limma). Functional enrichment of the DEGs was analyzed with the DAVID database. Protein-protein interaction networks were derived using the STRING database and visualized using Cytoscape software. Potential biomarker genes were analyzed using receiver operating characteristic (ROC) curves in the R package (pROC). The three datasets included 156 whole blood RNA samples from 89 sepsis patients and 67 healthy controls. Between the two groups, 568 DEGs were identified, among which 315 were upregulated and 253 were downregulated in the septic group. These genes were enriched for pathways mainly involved in the innate immune response, T-cell biology, antigen presentation, and natural killer cell function. ROC analyses identified nine genes—LRG1, ELANE, TP53, LCK, TBX21, ZAP70, CD247, ITK, and FYN—as potential new biomarkers for sepsis. Real-time PCR confirmed that the expression of seven of these genes was in accordance with the microarray results. This study revealed imbalanced immune responses at the transcriptomic level during early sepsis and identified nine genes as potential biomarkers for sepsis.

Inhibition of interleukin-2-inducible T-cell kinase causes reduction in imiquimod-induced psoriasiform inflammation through reduction of Th17 cells and enhancement of Treg cells in mice

Psoriasis is a debilitating chronic skin disease with a worldwide prevalence. Its main features include well-marked silvery scales on the skin of hands and feet and back which arise due to hyperproliferation of keratinocytes and infiltration of immune cells in the skin. Multiple interactions exist between adaptive immune cells such as T cells and innate immune cells such as neutrophils and macrophages which are key players in the pathogenesis of psoriasis. Interleukin-2-inducible T-cell kinase (ITK) plays a key role in Th17 cell development through control of several transcription factors. ITK has been shown to control NFATc1, NFkB and STAT3 in CD4⁺ T cells. Effect of ITK inhibitor in imiquimod (IMQ)-induced psoriasiform inflammation remains to be explored. In the current examination, role of ITK signaling and its inhibition blockade were evaluated on NFATc1, NFkB and STAT3, IL-17A, TNF-α, IFN-γ, Foxp3, IL-10 in CD4⁺ T cells in IMQ model. Our data display that ITK signaling is involved in IMQ-induced psoriatic inflammation as paralleled by enhancement of p-ITK, NFATc1, p-NFkB and p-STAT3 in CD4⁺ T cells. It was associated with enhancement of Th17/Th1 cells and neutrophilic inflammation in the skin. Preventive treatment with ITK inhibitor led to a reduction in Th17/Th1 cells and enhancement of Treg cells. Overall, this study suggests that ITK signaling is an important modulator of transcription factor signaling in CD4⁺ T cells which is associated with Th17/Th1 cells and psoriasiform inflammation in mice. ITK signaling blockade could be a therapeutic target for the treatment of psoriatic inflammation.

Ibrutinib for chronic lymphocytic leukemia in the setting of respiratory failure from severe COVID-19 infection: Case report and literature review

Ibrutinib, a known Burton's tyrosine kinase (BTK) and interleukin‐2 inducible T‐cell kinase (ITK) inhibitor, is used for the treatment of B‐cell disorders (chronic lymphocytic leukemia [CLL] and various other lymphomas) and chronic graft versus host disease following allogeneic hematopoietic cell transplantation. Because it is considered an immunosuppressant, continuation of ibrutinib is often debated when patients have an active infection, and this becomes an especially difficult decision in the setting of coronavirus disease 2019 (COVID‐19). Here, we describe a patient with CLL who was on ibrutinib then developed severe COVID‐19 infection requiring mechanical ventilation. We elected to continue ibrutinib the same day he was intubated, reasoning that BTK inhibition in myeloid immune cells has been shown to reduce or even reverse influenza‐mediated acute lung injury and that ITK inhibition in T cells has correlated with reduction in viral replication, and therefore may have an advantage in this setting. Ibrutinib also has been shown to block Src family kinases, which potentially could result in reduction of viral entry and the inflammatory cytokine response in the lungs. The patient was extubated after 9 days with a complex hospital course and eventually discharged on room air. The only way to rationally inform these decisions and explore similar potentially promising leads in this pandemic is to conduct carefully done clinical trials.

Role of the IL-2 inducible tyrosine kinase ITK and its inhibitors in disease pathogenesis

ITK (IL-2-inducible tyrosine kinase) belongs to the Tec family kinases and is mainly expressed in T cells. It is involved in TCR signalling events driving processes like T cell development as well as Th2, Th9 and Th17 responses thereby controlling the expression of pro-inflammatory cytokines. Studies have shown that ITK is involved in the pathogenesis of autoimmune diseases as well as in carcinogenesis. The loss of ITK or its activity either by mutation or by the use of inhibitors led to a beneficial outcome in experimental models of asthma, inflammatory bowel disease and multiple sclerosis among others. In humans, biallelic mutations in the ITK gene locus result in a monogenetic disorder leading to T cell dysfunction; in consequence, mainly EBV infections can lead to severe immune dysregulation evident by lymphoproliferation, lymphoma and hemophagocytic lymphohistiocytosis. Furthermore, patients who suffer from angioimmunoblastic T cell lymphoma have been found to express significantly more ITK. These findings put ITK in the strong focus as a target for drug development.

Blockade of interleukin-2-inducible T-cell kinase signaling attenuates acute lung injury in mice through adjustment of pulmonary Th17/Treg immune responses and reduction of oxidative stress

Acute lung injury (ALI) is linked with considerable morbidity and mortality. ALI can be caused by various agents, one of them being sepsis. ALI is characterized by injury to vascular endothelium and alveolar epithelium that results in edema, pulmonary immune cells infiltration and hypoxemia. Neutrophils and T cells particularly play a huge role in amplification of pulmonary inflammation through release of multiple inflammatory mediators. Recent reports suggest a strong involvement of Th17 cells and oxidative stress in initiation/amplification of pulmonary inflammation during ALI. Interleukin-2-inducible T-cell kinase (ITK) plays a key role in Th17 cell development through control of several transcription factors. Therefore, our study explored the role of ITK on airway inflammation (total/neutrophilic cell counts, myeloperoxidase activity, E-cadherin expression, histopathological analyses) and effect of its inhibition on various inflammatory/anti-inflammatory pathways during ALI [phosphorylated-ITK (p-ITK), NFATc1, IL-17A, STAT3, Foxp3, IL-10, iNOS, nitrotyrosine, lipid peroxides). ALI was associated with increased total/neutrophilic cell counts and myeloperoxidase activity, and decreased E-cadherin expression in airway epithelial cells (AECs) which was concurrent with upregulation of p-ITK, NFATc1, IL-17A, STAT3 in CD4+ T cells and iNOS/nitrotyrosine in AECs. Treatment with ITK inhibitor reversed ALI-induced changes in airway inflammation and Th17 cells/oxidative stress. Treatment with ITK inhibitor further expanded Treg cells in mice with ALI. In short, our study proposes that ITK signaling plays a significant role in sepsis-induced ALI through upregulation of Th17 cells and oxidative stress. Further, findings provide evidence that ITK blockade could be a potential treatment strategy to attenuate airway inflammation associated with ALI.

High expression level of peptidylprolyl isomerase A is correlated with poor prognosis of liver hepatocellular carcinoma

Peptidylprolyl isomerase A (PPIA) has been reported to be correlated with cancer. The present study investigated the prognostic values of PPIA expression levels in cancer by comparing different types of cancer using databases. High expression levels of PPIA were observed in 17 out of 17 cancer types compared with normal adjacent tissues. High expression levels of PPIA were associated with decreased overall survival in low grade glioma, acute myeloid leukemia, lung adenocarcinoma, skin cutaneous melanoma and liver hepatocellular carcinoma (LIHC). The prognostic effect of PPIA expression in LIHC was independent of tumor grade. High expression levels of PPIA were of particular prognostic value in stage 3, American Joint Committee on Cancer Tumor 3, hepatitis B virus negative and sorafenib-administered subgroups in LIHC. The expression level of PPIA was significantly associated with levels of basigin and signal transducer and activator of transcription 3, which may be major effectors of PPIA in the progression of the cancer.

Invasive fungal infections in the immunocompromised host: Mechanistic insights in an era of changing immunotherapeutics

The use of cytotoxic chemotherapy in the treatment of malignant and inflammatory disorders is beset by considerable adverse effects related to nonspecific cytotoxicity. Accordingly, a mechanistic approach to therapeutics has evolved in recent times with small molecular inhibitors of intracellular signaling pathways involved in disease pathogenesis being developed for clinical use, some with unparalleled efficacy and tolerability. Nevertheless, there are emerging concerns regarding an association with certain small molecular inhibitors and opportunistic infections, including invasive fungal diseases. This is perhaps unsurprising, given that the molecular targets of such agents play fundamental and multifaceted roles in orchestrating innate and adaptive immune responses. Nevertheless, some small molecular inhibitors appear to possess intrinsic antifungal activity and may therefore represent novel therapeutic options in future. This is particularly important given that antifungal resistance is a significant, emerging concern. This paper is a comprehensive review of the state-of-the-art in the molecular immunology to fungal pathogens as applied to existing and emerging small molecular inhibitors.

Identification of a New Inhibitor That Stabilizes Interleukin-2-Inducible T-Cell Kinase in Its Inactive Conformation

Interleukin-2-inducible T-cell kinase (ITK) plays an important role in T-cell signaling and is considered a promising drug target. As the ATP binding sites of protein kinases are highly conserved, the design of selective kinase inhibitors remains a challenge. Targeting inactive kinase conformations can address the issue of kinase inhibitor selectivity. It is important for selectivity considerations to identify compounds that stabilize inactive conformations from the primary screen hits. Here we screened a library of 390,000 compounds with an ADP-Glo assay using dephosphorylated ITK. After a surface plasmon resonance (SPR) assay was used to filter out promiscuous inhibitors, 105 hits were confirmed. Next, we used a fluorescent biosensor to enable the detection of conformational changes to identify inactive conformation inhibitors. A single-cysteine-substituted ITK mutant was labeled with acrylodan, and fluorescence emission was monitored. Using a fluorescent biosensor assay, we identified 34 inactive conformation inhibitors from SPR hits. Among them, one compound was bound to a site other than the ATP pocket and exhibited excellent selectivity against a kinase panel. Overall, (1) biochemical screening using dephosphorylated kinase, (2) hit confirmation by SPR assay, and (3) fluorescent biosensor assay that can distinguish inactive compounds provide a useful platform and offer opportunities to identify selective kinase inhibitors.

How ibrutinib, a B-cell malignancy drug, became an FDA-approved second-line therapy for steroid-resistant chronic GVHD

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is potentially curative for a number of hematologic conditions, both malignant and nonmalignant. However, its success can be limited by the development of acute and chronic graft-versus-host disease (GVHD). Chronic GVHD (cGVHD) is the most common long-term complication following allo-SCT, and patients who develop this condition have significantly higher morbidity and mortality and significantly lower quality of life than patients who do not. Until recently, there were no US Food and Drug Administration (FDA)-approved therapies for cGVHD treatment. In this review article, we describe how ibrutinib was identified as potential cGVHD therapy based on preclinical cGVHD models and clinical studies in B-cell malignancies and elucidation of its mechanisms of action in cGVHD. Results from a phase 2 clinical trial that was designed based on National Institutes of Health Criteria for the grading and staging of cGVHD culminated in the FDA-approval of ibrutinib as second line therapy of steroid-refractory or steroid-resistant cGVHD. Results of ibrutinib studies in phase 3 randomized studies, for cGVHD prophylaxis and as first -line testing along with steroids will be especially important in selecting the preferred indications for ibrutinib in patients at risk for or who have developed cGVHD.

Proteomic Profiling of Mouse Helper T Cell Differentiation

Helper T cell differentiation is a key process in the regulation of adaptive immune responses. Here, mouse Th1 and Th2 cells are profiled using high-throughput proteomics to increase the understanding of the molecular biology of Th differentiation to support the design of prophylactic and therapeutic intervention strategies for (infectious) diseases. Protein profiling of Th1/Th2 differentiated cells results in the quantification of almost 6000 proteins of which 41 are differentially expressed at FDR < 0.1, and 19 at the FDR < 0.05 level, respectively. Differential protein expression analysis identifies a number of the expected canonical Th differentiation markers, and gene set analysis using the REACTOME database and a hypergeometric test (FDR < 0.05) confirms that helper T cell pathways are the top sets that are differentially expressed. Additionally, by network analysis, many differentially expressed proteins are associated with the Th1 and Th2 pathways. Data are available via PRIDE database with identifier PXD004532.

ITK inhibition induced in vitro and in vivo anti-tumor activity through downregulating TCR signaling pathway in malignant T cell lymphoma

Background

Angioimmunoblastic T cell lymphoma (AITL) is a distinct subtype of peripheral T cell lymphoma and associated with poor outcomes. The activation status of T cell receptor (TCR) signaling has recently become a focus of attention in terms of the therapeutic targets. However, the molecular pathogenesis mechanisms and novel therapeutic targets are largely unknown.

Methods

Antibodies specific to phosphorylated ZAP70, ITK and PLCγ1 were used to identify the activation status of intracellular proteins involved in TCR signaling in AITL patients. Malignant T cell lymphoma cells were transduced with a lentiviral construct containing ITK shRNA for cellular and functional assays. The antitumor effects of the selective ITK inhibitor BMS-509744 were determined in vitro and in vivo.

Results

Immunohistochemistry staining showed that more than half of the AITL patients (n = 38) exhibited continuously activated intracellular TCR signaling pathway. Patients positive for phosphorylated ITK showed a lower rate of complete response (20% vs. 75%, P = 0.004) and a shorter progression-free survival (5.17 months vs. 25.1 months, P = 0.022) than patients negative for phosphorylated ITK. Genetic and pharmacological cellular ITK inhibition significantly compromised the proliferation, invasion and migration of malignant T cells. The selective ITK inhibitor BMS-509744 also induced the pro-apoptotic effects and G2/M phase cell cycle arrest in vitro and in vivo. Finally, inhibition of ITK synergistically enhanced the antitumor effect of vincristine and doxorubicin on malignant T cell lymphoma cell lines.

Conclusions

Our findings suggest that ITK may be a novel candidate therapeutic target for the treatment of patients with ITK-expressing malignant T-cell lymphomas.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0754-9) contains supplementary material, which is available to authorized users.

What can primary immunodeficiencies teach us about Th9 cell differentiation and function?

Interleukin-9 (IL-9) producing CD4⁺ Th9 cells are a unique subset of effector cells involved in both health and disease. Th9 cells have been associated with protective immunity during parasitic infections with helminths, protozoans and extracellular pathogens, but implicated in disease states such as allergic asthma, atopic dermatitis, food allergy and autoimmune conditions including multiple sclerosis and ulcerative colitis. Here, we review the cytokine signaling pathways and downstream transcription factors required for IL-9 expression and how human primary immunodeficiencies caused by monogenic mutations can help elucidate the complex requirements for human Th9 cell differentiation. Primary immunodeficiencies are a platform for investigating IL-9 expression in primary human lymphocytes and by inference whether Th9 cells are implicated in the clinical phenotype characteristic of these patients.

Acalabrutinib (ACP-196): A Covalent Bruton Tyrosine Kinase Inhibitor with a Differentiated Selectivity and In Vivo Potency Profile

Several small-molecule Bruton tyrosine kinase (BTK) inhibitors are in development for B cell malignancies and autoimmune disorders, each characterized by distinct potency and selectivity patterns. Herein we describe the pharmacologic characterization of BTK inhibitor acalabrutinib [compound 1, ACP-196 (4-[8-amino-3-[(2S)-1-but-2-ynoylpyrrolidin-2-yl]imidazo[1,5-a]pyrazin-1-yl]-N-(2-pyridyl)benzamide)]. Acalabrutinib possesses a reactive butynamide group that binds covalently to Cys481 in BTK. Relative to the other BTK inhibitors described here, the reduced intrinsic reactivity of acalabrutinib helps to limit inhibition of off-target kinases having cysteine-mediated covalent binding potential. Acalabrutinib demonstrated higher biochemical and cellular selectivity than ibrutinib and spebrutinib (compounds 2 and 3, respectively). Importantly, off-target kinases, such as epidermal growth factor receptor (EGFR) and interleukin 2-inducible T cell kinase (ITK), were not inhibited. Determination of the inhibitory potential of anti-immunoglobulin M-induced CD69 expression in human peripheral blood mononuclear cells and whole blood demonstrated that acalabrutinib is a potent functional BTK inhibitor. In vivo evaluation in mice revealed that acalabrutinib is more potent than ibrutinib and spebrutinib. Preclinical and clinical studies showed that the level and duration of BTK occupancy correlates with in vivo efficacy. Evaluation of the pharmacokinetic properties of acalabrutinib in healthy adult volunteers demonstrated rapid absorption and fast elimination. In these healthy individuals, a single oral dose of 100 mg showed approximately 99% median target coverage at 3 and 12 hours and around 90% at 24 hours in peripheral B cells. In conclusion, acalabrutinib is a BTK inhibitor with key pharmacologic differentiators versus ibrutinib and spebrutinib and is currently being evaluated in clinical trials.

T-Bet independent development of IFNγ secreting natural T helper 1 cell population in the absence of Itk

Th1, Th2, Th9 and Th17 cells are conventional CD4⁺ effector T cells identified as secretors of prototypical cytokines IFNγ, IL4, IL9, and IL-17A respectively. Recently, populations of natural Th17 and Th1 cells (nTh17 and nTh1) with innate-like phenotype have been identified in the thymus that are distinct from conventional Th17 and Th1 cells. The absence of the Tec family kinase Interleukin-2 inducible T cell kinase (Itk) results in T cell immunodeficiency in mice and humans. Here we show that Itk negatively regulates the development of nTh1 cells that express IFNγ in a Tbet independent manner, and whose expansion can be enhanced by IL4. Furthermore, we show that robust induction of IL4 responses during Trichinella spiralis infection enhance the presence of nTh1 cells. We conclude T cell receptor signaling via Itk controls the development of natural Th1 cells, which are expanded by the presence of IL4.

Determining Cysteines Available for Covalent Inhibition Across the Human Kinome

Covalently bound protein kinase inhibitors have been frequently designed to target noncatalytic cysteines at the ATP binding site. Thus, it is important to know if a given cysteine can form a covalent bond. Here we combine a function-site interaction fingerprint method and DFT calculations to determine the potential of cysteines to form a covalent interaction with an inhibitor. By harnessing the human structural kinome, a comprehensive structure-based binding site cysteine data set was assembled. The orientation of the cysteine thiol group indicates which cysteines can potentially form covalent bonds. These covalent inhibitor easy-available cysteines are located within five regions: P-loop, roof of pocket, front pocket, catalytic-2 of the catalytic loop, and DFG-3 close to the DFG peptide. In an independent test set these cysteines covered 95% of covalent kinase inhibitors. This study provides new insights into cysteine reactivity and preference which is important for the prospective development of covalent kinase inhibitors.

IL2 Inducible T-cell Kinase, a Novel Therapeutic Target in Melanoma

PURPOSE

IL2 inducible T-cell kinase (ITK) promoter CpG sites are hypomethylated in melanomas compared with nevi. The expression of ITK in melanomas, however, has not been established and requires elucidation.

EXPERIMENTAL DESIGN

An ITK-specific monoclonal antibody was used to probe sections from deidentified, formalin-fixed paraffin-embedded tumor blocks or cell line arrays and ITK was visualized by IHC. Levels of ITK protein differed among melanoma cell lines and representative lines were transduced with four different lentiviral constructs that each contained an shRNA designed to knockdown ITK mRNA levels. The effects of the selective ITK inhibitor BI 10N on cell lines and mouse models were also determined.

RESULTS

ITK protein expression increased with nevus to metastatic melanoma progression. In melanoma cell lines, genetic or pharmacologic inhibition of ITK decreased proliferation and migration and increased the percentage of cells in the G0-G1 phase. Treatment of melanoma-bearing mice with BI 10N reduced growth of ITK-expressing xenografts or established autochthonous (Tyr-Cre/Pten(null)/Braf(V600E)) melanomas.

CONCLUSIONS

We conclude that ITK, formerly considered an immune cell-specific protein, is aberrantly expressed in melanoma and promotes tumor development and progression. Our finding that ITK is aberrantly expressed in most metastatic melanomas suggests that inhibitors of ITK may be efficacious for melanoma treatment. The efficacy of a small-molecule ITK inhibitor in the Tyr-Cre/Pten(null)/Braf(V600E) mouse melanoma model supports this possibility.

Itk is required for Th9 differentiation via TCR-mediated induction of IL-2 and IRF4

Th9 cells produce interleukin (IL)-9, a cytokine implicated in allergic asthma and autoimmunity. Here we show that Itk, a mediator of T cell receptor signalling required for Th2 immune responses and the development of asthma, is a positive regulator of Th9 differentiation. In a model of allergic lung disease, Itk-deficient mice show reduced pulmonary inflammation and IL-9 production by T cells and innate lymphoid type 2 cells (ILC2), despite normal early induction of ILC2s. In vitro, Itk(-/-) CD4(+) T cells do not produce IL-9 and have reduced levels of IRF4 (Interferon Regulator Factor 4), a critical transcription factor for effector T cell function. Both IL-9 and IRF4 expression are rescued by either IL-2 or constitutively active STAT5, but not NFATc1. STAT5 binds the Irf4 promoter, demonstrating one mechanism by which IL-2 rescues weakly activated T cells. Itk inhibition also reduces IL-9 expression by human T cells, implicating ITK as a key regulator of Th9 induction.

Inhibition of the kinase ITK in a mouse model of asthma reduces cell death and fails to inhibit the inflammatory response

Interleukin-2 (IL-2)-inducible T cell kinase (ITK) mediates T cell receptor (TCR) signaling primarily to stimulate the production of cytokines, such as IL-4, IL-5, and IL-13, from T helper 2 (TH2) cells. Compared to wild-type mice, ITK knockout mice are resistant to asthma and exhibit reduced lung inflammation and decreased amounts of TH2-type cytokines in the bronchoalveolar lavage fluid. We found that a small-molecule selective inhibitor of ITK blocked TCR-mediated signaling in cultured TH2 cells, including the tyrosine phosphorylation of phospholipase C-γ1 (PLC-γ1) and the secretion of IL-2 and TH2-type cytokines. Unexpectedly, inhibition of the kinase activity of ITK during or after antigen rechallenge in an ovalbumin-induced mouse model of asthma failed to reduce airway hyperresponsiveness and inflammation. Rather, in mice, pharmacological inhibition of ITK resulted in T cell hyperplasia and the increased production of TH2-type cytokines. Thus, our studies predict that inhibition of the kinase activity of ITK may not be therapeutic in patients with asthma.

Targets for Ibrutinib Beyond B Cell Malignancies

Ibrutinib (Imbruvica^™) is an irreversible, potent inhibitor of Bruton's tyrosine kinase (BTK). Over the last few years, ibrutinib has developed from a promising drug candidate to being approved by FDA for the treatment of three B cell malignancies, a truly remarkable feat. Few, if any medicines are monospecific and ibrutinib is no exception; already during ibrutinib's initial characterization, it was found that it could bind also to other kinases. In this review, we discuss the implications of such interactions, which go beyond the selective effect on BTK in B cell malignancies. In certain cases, the outcome of ibrutinib treatment likely results from the combined inhibition of BTK and other kinases, causing additive or synergistic, effects. Conversely, there are also examples when the clinical outcome seems unrelated to inhibition of BTK. Thus, more specifically, adverse effects such as enhanced bleeding or arrhythmias could potentially be explained by different interactions. We also predict that during long‐term treatment bone homoeostasis might be affected due to the inhibition of osteoclasts. Moreover, the binding of ibrutinib to molecular targets other than BTK or effects on cells other than B cell‐derived malignancies could be beneficial and result in new indications for clinical applications.

Allele-sensitive mutant, Itkas, reveals that Itk kinase activity is required for Th1, Th2, Th17, and iNKT-cell cytokine production

Itk(-/-) mice exhibit defects in the activation, development, and function of CD4(+) and CD8(+) T cells and iNKT cells. These and other defects in these mice make it difficult to uncouple the developmental versus functional requirement of Itk signaling. Here, we report an allele-sensitive mutant of Itk (Itkas) whose catalytic activity can be selectively inhibited by analogs of the PP1 kinase inhibitor. We show that Itkas behaves like WT Itk in the absence of the inhibitor and can rescue the development of Itk(-/-) T cells in mice. Using mice carrying Itkas, we show using its inhibitor that Itk activity is required not only for Th2, Th17, and iNKT-cell cytokine production, but also surprisingly, for Th1 cytokine production. This work has important implications for understanding the role of Itk signaling in the development versus function of iNKT cells, Th1, Th2, and Th17 cells.

Genome-wide association study of susceptibility to infection by Mycobacterium avium subspecies paratuberculosis in Holstein cattle

Paratuberculosis, or Johne's disease, is a chronic, granulomatous, gastrointestinal tract disease of cattle and other ruminants caused by the bacterium Mycobacterium avium, subspecies paratuberculosis (MAP). Control of Johne's disease is based on programs of testing and culling animals positive for infection with MAP while concurrently modifying management to reduce the likelihood of infection. The current study is motivated by the hypothesis that genetic variation in host susceptibility to MAP infection can be dissected and quantifiable associations with genetic markers identified. For this purpose, a case-control, genome-wide association study was conducted using US Holstein cattle phenotyped for MAP infection using a serum ELISA and/or fecal culture test. Cases included cows positive for either serum ELISA, fecal culture or both. Controls consisted of animals negative for the serum ELISA test or both serum ELISA and fecal culture when both were available. Controls were matched by herd and proximal birth date with cases. A total of 856 cows (451 cases and 405 controls) were used in initial discovery analyses, and an additional 263 cows (159 cases and 104 controls) from the same herds were used as a validation data set. Data were analyzed in a single marker analysis controlling for relatedness of individuals (GRAMMAR-GC) and also in a Bayesian analysis in which multiple marker effects were estimated simultaneously (GenSel). For the latter, effects of non-overlapping 1 Mb marker windows across the genome were estimated. Results from the two discovery analyses were generally concordant; however, discovery results were generally not well supported in analysis of the validation data set. A combined analysis of discovery and validation data sets provided strongest support for SNPs and 1 Mb windows on chromosomes 1, 2, 6, 7, 17 and 29.

Ibrutinib treatment ameliorates murine chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a life-threatening impediment to allogeneic hematopoietic stem cell transplantation, and current therapies do not completely prevent and/or treat cGVHD. CD4+ T cells and B cells mediate cGVHD; therefore, targeting these populations may inhibit cGVHD pathogenesis. Ibrutinib is an FDA-approved irreversible inhibitor of Bruton's tyrosine kinase (BTK) and IL-2 inducible T cell kinase (ITK) that targets Th2 cells and B cells and produces durable remissions in B cell malignancies with minimal toxicity. Here, we evaluated whether ibrutinib could reverse established cGVHD in 2 complementary murine models, a model interrogating T cell-driven sclerodermatous cGVHD and an alloantibody-driven multiorgan system cGVHD model that induces bronchiolar obliterans (BO). In the T cell-mediated sclerodermatous cGVHD model, ibrutinib treatment delayed progression, improved survival, and ameliorated clinical and pathological manifestations. In the alloantibody-driven cGVHD model, ibrutinib treatment restored pulmonary function and reduced germinal center reactions and tissue immunoglobulin deposition. Animals lacking BTK and ITK did not develop cGVHD, indicating that these molecules are critical to cGVHD development. Furthermore, ibrutinib treatment reduced activation of T and B cells from patients with active cGVHD. Our data demonstrate that B cells and T cells drive cGVHD and suggest that ibrutinib has potential as a therapeutic agent, warranting consideration for cGVHD clinical trials.

Transcriptional regulation of kinases downstream of the T cell receptor: another immunomodulatory mechanism of glucocorticoids

BACKGROUND

Glucocorticoids affect peripheral immune responses, including modulation of T-cell activation, differentiation, and apoptosis. The quantity and quality of T-cell receptor (TCR)-triggered intracellular signals modulate T-cell function. Thus, glucocorticoids may affect T cells by interfering with the TCR signaling cascade. The purpose of the study was to search for glucocorticoid-modulated kinases downstream of the TCR.

METHODS

Gene modulation in lymphoid cells either treated with glucocorticoids or from glucocorticoid-treated mice was studied using a RNase protection assay, real-time PCR, and western blotting. The sensitivity of genetically modified thymocytes to glucocorticoid-induced apoptosis was studied by performing hypotonic propidium iodide staining and flow cytometry. The Student's t-test was employed for statistical evaluation.

RESULTS

We found that transcription of Itk, a non-receptor tyrosine kinase of the Tec family, was up-regulated in a mouse T-cell hybridoma by the synthetic glucocorticoid dexamethasone. In contrast, dexamethasone down-regulated the expression of Txk, a Tec kinase that functions redundantly with Itk, and Lck, the Src kinase immediately downstream of the TCR. We investigated the expression of Itk, Txk, and Lck in thymocytes and mature lymphocytes following in vitro and in vivo dexamethasone treatment at different time points and doses. Kinase expression was differentially modulated and followed distinct kinetics. Itk was up-regulated in all cell types and conditions tested. Txk was strongly up-regulated in mature lymphocytes but only weakly up-regulated or non-modulated in thymocytes in vitro or in vivo, respectively. Conversely, Lck was down-regulated in thymocytes, but not modulated or up-regulated in mature lymphocytes in the different experimental conditions. This complex behaviour correlates with the presence of both positive and negative glucocorticoid responsive elements (GRE and nGRE, respectively) in the Itk, Txk and Lck genes. To investigate the function associated with Itk up-regulation, dexamethasone-induced apoptosis of thymocytes from Itk-deficient mice was evaluated. Our results demonstrated that Itk deficiency causes increased sensitivity to dexamethasone but not to other pro-apoptotic stimuli.

CONCLUSIONS

Modulation of Itk, Txk, and Lck in thymocytes and mature lymphocytes is another mechanism by which glucocorticoids modulate T-cell activation and differentiation. Itk up-regulation plays a protective role in dexamethasone-treated thymocytes.

Inducible tyrosine kinase inhibitors: a review of the patent literature (2010 - 2013)

INTRODUCTION

The non-receptor tyrosine kinase, inducible tyrosine kinase (Itk), plays an important role in thymus(T)-cell signalling and the production of pro-inflammatory cytokines. Itk, and the other Tec family members, Rlk and Tec, are viewed as attractive drug targets for new agents for the treatment of autoimmune and inflammatory diseases. Interest in Itk inhibitors is still modest compared to other kinases such as the Janus kinase (JAK) family or Syk.

AREAS COVERED

This article reviews the patent filings published from January 2010 to April 2014 that claim Itk inhibitors. It first considers those applications that claim selective, or apparently selective, Itk inhibitors. It then considers those applications that claim less-selective Itk inhibitors. The recent interest in irreversible Itk inhibitors is also discussed.

EXPERT OPINION

There is a difference of opinion as to the preferred utility for Itk inhibitors. Progress has been made in designing selective Itk inhibitors but little clinical progress. Until clinical data are available, it remains difficult to assess how well Itk inhibitors compare with JAK inhibitors as potential treatments for rheumatoid arthritis. However, animal data suggest that irreversible Itk inhibitors could be useful in treating asthma, whereas dual Itk inhibitors may have more utility in treating rheumatoid arthritis.

Itk-mediated integration of T cell receptor and cytokine signaling regulates the balance between Th17 and regulatory T cells

Loss of the Tec family kinase Itk results in a bias to FoxP3⁺ T_reg cell differentiation and reduced TCR-induced phosphorylation of mTOR targets.

A proper balance between Th17 and T regulatory cells (T_reg cells) is critical for generating protective immune responses while minimizing autoimmunity. We show that the Tec family kinase Itk (IL2-inducible T cell kinase), a component of T cell receptor (TCR) signaling pathways, influences this balance by regulating cross talk between TCR and cytokine signaling. Under both Th17 and T_reg cell differentiation conditions, Itk^−/− CD4⁺ T cells develop higher percentages of functional FoxP3⁺ cells, associated with increased sensitivity to IL-2. Itk^−/− CD4⁺ T cells also preferentially develop into T_reg cells in vivo. We find that Itk-deficient T cells exhibit reduced TCR-induced phosphorylation of mammalian target of rapamycin (mTOR) targets, accompanied by downstream metabolic alterations. Surprisingly, Itk^−/− cells also exhibit reduced IL-2–induced mTOR activation, despite increased STAT5 phosphorylation. We demonstrate that in wild-type CD4⁺ T cells, TCR stimulation leads to a dose-dependent repression of Pten. However, at low TCR stimulation or in the absence of Itk, Pten is not effectively repressed, thereby uncoupling STAT5 phosphorylation and phosphoinositide-3-kinase (PI3K) pathways. Moreover, Itk-deficient CD4⁺ T cells show impaired TCR-mediated induction of Myc and miR-19b, known repressors of Pten. Our results demonstrate that Itk helps orchestrate positive feedback loops integrating multiple T cell signaling pathways, suggesting Itk as a potential target for altering the balance between Th17 and T_reg cells.

Regulation of ras exchange factors and cellular localization of ras activation by lipid messengers in T cells

The Ras-MAPK signaling pathway is highly conserved throughout evolution and is activated downstream of a wide range of receptor stimuli. Ras guanine nucleotide exchange factors (RasGEFs) catalyze GTP loading of Ras and play a pivotal role in regulating receptor-ligand induced Ras activity. In T cells, three families of functionally important RasGEFs are expressed: RasGRF, RasGRP, and Son of Sevenless (SOS)-family GEFs. Early on it was recognized that Ras activation is critical for T cell development and that the RasGEFs play an important role herein. More recent work has revealed that nuances in Ras activation appear to significantly impact T cell development and selection. These nuances include distinct biochemical patterns of analog versus digital Ras activation, differences in cellular localization of Ras activation, and intricate interplays between the RasGEFs during distinct T cell developmental stages as revealed by various new mouse models. In many instances, the exact nature of these nuances in Ras activation or how these may result from fine-tuning of the RasGEFs is not understood. One large group of biomolecules critically involved in the control of RasGEFs functions are lipid second messengers. Multiple, yet distinct lipid products are generated following T cell receptor (TCR) stimulation and bind to different domains in the RasGRP and SOS RasGEFs to facilitate the activation of the membrane-anchored Ras GTPases. In this review we highlight how different lipid-based elements are generated by various enzymes downstream of the TCR and other receptors and how these dynamic and interrelated lipid products may fine-tune Ras activation by RasGEFs in developing T cells.

Ibrutinib is an irreversible molecular inhibitor of ITK driving a Th1-selective pressure in T lymphocytes

Given its critical role in T-cell signaling, interleukin-2-inducible kinase (ITK) is an appealing therapeutic target that can contribute to the pathogenesis of certain infectious, autoimmune, and neoplastic diseases. Ablation of ITK subverts Th2 immunity, thereby potentiating Th1-based immune responses. While small-molecule ITK inhibitors have been identified, none have demonstrated clinical utility. Ibrutinib is a confirmed irreversible inhibitor of Bruton tyrosine kinase (BTK) with outstanding clinical activity and tolerability in B-cell malignancies. Significant homology between BTK and ITK alongside in silico docking studies support ibrutinib as an immunomodulatory inhibitor of both ITK and BTK. Our comprehensive molecular and phenotypic analysis confirms ITK as an irreversible T-cell target of ibrutinib. Using ibrutinib clinical trial samples along with well-characterized neoplastic (chronic lymphocytic leukemia), parasitic infection (Leishmania major), and infectious disease (Listeria monocytogenes) models, we establish ibrutinib as a clinically relevant and physiologically potent ITK inhibitor with broad therapeutic utility. This trial was registered at www.clinicaltrials.gov as #NCT01105247 and #NCT01217749.

Back to the future: oral targeted therapy for RA and other autoimmune diseases

The molecular biology revolution coupled with the development of monoclonal antibody technology enabled remarkable progress in rheumatology therapy, comprising an array of highly effective biologic agents. With advances in understanding of the molecular nature of immune cell receptors came elucidation of intracellular signalling pathways downstream of these receptors. These discoveries raise the question of whether selective targeting of key intracellular factors with small molecules would add to the rheumatologic armamentarium. In this Review, we discuss several examples of this therapeutic strategy that seem to be successful, and consider their implications for the future of immune-targeted treatments. We focus on kinase inhibitors, primarily those targeting Janus kinase family members and spleen tyrosine kinase, given their advanced status in clinical development and application. We also summarize other targets involved in signalling pathways that might offer promise for therapeutic intervention in the future.

TEC and MAPK Kinase Signalling Pathways in T helper (TH) cell Development, TH2 Differentiation and Allergic Asthma

Significant advances in our understanding of the signalling events during T cell development and differentiation have been made in the past few decades. It is clear that ligation of the T cell receptor (TCR) triggers a series of proximal signalling cascades regulated by an array of protein kinases. These orchestrated and highly regulated series of events, with differential requirements of particular kinases, highlight the disparities between αβ+CD4+ T cells. Throughout this review we summarise both new and old studies, highlighting the role of Tec and MAPK in T cell development and differentiation with particular focus on T helper 2 (TH2) cells. Finally, as the allergy epidemic continues, we feature the role played by TH2 cells in the development of allergy and provide a brief update on promising kinase inhibitors that have been tested in vitro, in pre-clinical disease models in vivo and into clinical studies.

TEC family kinases in health and disease--loss-of-function of BTK and ITK and the gain-of-function fusions ITK-SYK and BTK-SYK

The TEC family is ancient and constitutes the second largest family of cytoplasmic tyrosine kinases. In 1993, loss-of-function mutations in the BTK gene were reported as the cause of X-linked agammaglobulinemia. Of all the existing 90 tyrosine kinases in humans, Bruton's tyrosine kinase (BTK) is the kinase for which most mutations have been identified. These experiments of nature collectively provide a form of mutation scanning with direct implications for the several hundred endogenous signaling proteins carrying domains also found in BTK. In 2009, an inactivating mutation in the ITK gene was shown to cause susceptibility to lethal Epstein-Barr virus infection. Both kinases represent interesting targets for inhibition: in the case of BTK, as an immunosuppressant, whereas there is evidence that the inhibition of inducible T-cell kinase (ITK) could influence the infectivity of HIV and also have anti-inflammatory activity. Since 2006, several patients carrying a fusion protein, originating from a translocation joining genes encoding the kinases ITK and spleen tyrosine kinase (SYK), have been shown to develop T-cell lymphoma. We review these disease processes and also describe the role of the N-terminal pleckstrin homology-Tec homology (PH-TH) domain doublet of BTK and ITK in the downstream intracellular signaling of such fusion proteins.