PTEN loss in glioma cell lines leads to increased extracellular vesicles biogenesis and PD-L1 cargo in a PI3K-dependent manner

Phosphatase and Tensin Homologue (PTEN) is one of the most frequently lost tumor suppressors in cancer and the predominant negative regulator of the PI3K/AKT signaling axis. A growing body of evidence has highlighted the loss of PTEN with immuno-modulatory functions including the upregulation of the programmed death ligand-1 (PD-L1), an altered tumor derived secretome that drives an immunosuppressive tumor immune microenvironment (TIME), and resistance to certain immunotherapies. Given their roles in immunosuppression and tumor growth, we examined whether the loss of PTEN would impact the biogenesis, cargo, and function of extracellular vesicles (EVs) in the context of the anti-tumor associated cytokine interferon-γ (IFN-γ). Through genetic and pharmacological approaches, we show that PD-L1 expression is regulated by JAK/STAT signaling, not PI3K signaling. Instead, we observe that PTEN loss positively upregulates cell surface levels of PD-L1 and enhances the biogenesis of EVs enriched with PD-L1 in a PI3K-dependent manner. We demonstrate that because of these changes, EVs derived from glioma cells lacking PTEN have a greater ability to suppress T cell receptor (TCR) signaling. Taken together, these findings provide important new insights into how the loss of PTEN can contribute to an immunosuppressive TIME, facilitate immune evasion, and highlight a novel role for PI3K signaling in the regulation of EV biogenesis and the cargo they contain.

Adaptive immune cells are necessary for SARS-CoV-2-induced pathology

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the ongoing global pandemic associated with morbidity and mortality in humans. Although disease severity correlates with immune dysregulation, the cellular mechanisms of inflammation and pathogenesis of COVID-19 remain relatively poorly understood. Here, we used mouse-adapted SARS-CoV-2 strain MA10 to investigate the role of adaptive immune cells in disease. We found that while infected wild-type mice lost ~10% weight by 3 to 4 days postinfection, rag-/- mice lacking B and T lymphocytes did not lose weight. Infected lungs at peak weight loss revealed lower pathology scores, fewer neutrophils, and lower interleukin-6 and tumor necrosis factor-α in rag-/- mice. Mice lacking αβ T cells also had less severe weight loss, but adoptive transfer of T and B cells into rag-/- mice did not significantly change the response. Collectively, these findings suggest that while adaptive immune cells are important for clearing SARS-CoV-2 infection, this comes at the expense of increased inflammation and pathology.

Th2 and Th17-associated immunopathology following SARS-CoV-2 breakthrough infection in Spike-vaccinated ACE2-humanized mice

Vaccines have demonstrated remarkable effectiveness in protecting against COVID-19; however, concerns regarding vaccine-associated enhanced respiratory diseases (VAERD) following breakthrough infections have emerged. Spike protein subunit vaccines for SARS-CoV-2 induce VAERD in hamsters, where aluminum adjuvants promote a Th2-biased immune response, leading to increased type 2 pulmonary inflammation in animals with breakthrough infections. To gain a deeper understanding of the potential risks and the underlying mechanisms of VAERD, we immunized ACE2-humanized mice with SARS-CoV-2 Spike protein adjuvanted with aluminum and CpG-ODN. Subsequently, we exposed them to increasing doses of SARS-CoV-2 to establish a breakthrough infection. The vaccine elicited robust neutralizing antibody responses, reduced viral titers, and enhanced host survival. However, following a breakthrough infection, vaccinated animals exhibited severe pulmonary immunopathology, characterized by a significant perivascular infiltration of eosinophils and CD4+ T cells, along with increased expression of Th2/Th17 cytokines. Intracellular flow cytometric analysis revealed a systemic Th17 inflammatory response, particularly pronounced in the lungs. Our data demonstrate that aluminum/CpG adjuvants induce strong antibody and Th1-associated immunity against COVID-19 but also prime a robust Th2/Th17 inflammatory response, which may contribute to the rapid onset of T cell-mediated pulmonary immunopathology following a breakthrough infection. These findings underscore the necessity for further research to unravel the complexities of VAERD in COVID-19 and to enhance vaccine formulations for broad protection and maximum safety.

Targeting kinase ITK treats autoimmune arthritis via orchestrating T cell differentiation and function

IL-2 inducible T cell kinase (ITK) is critical in T helper subset differentiation and its inhibition has been suggested for the treatment of T cell-mediated inflammatory diseases. T follicular helper (Tfh), Th17 and regulatory T cells (Treg) also play important roles in the development of rheumatoid arthritis (RA), while the role of ITK in the development of RA and the intricate balance between effector T and regulatory T cells remains unclear. Here, we found that CD4+ T cells from RA patients presented with an elevated ITK activation. ITK inhibitor alleviated existing collagen-induced arthritis (CIA) and reduced antigen specific antibody production. Blocking ITK kinase activity interferes Tfh cell generation. Moreover, ITK inhibitor effectively rebalances Th17 and Treg cells by regulating Foxo1 translocation. Furthermore, we identified dihydroartemisinin (DHA) as a potential ITK inhibitor, which could inhibit PLC-γ1 phosphorylation and the progression of CIA by rebalancing Th17 and Treg cells. Out data imply that ITK activation is upregulated in RA patients, and therefore blocking ITK signal may provide an effective strategy to treat RA patients and highlight the role of ITK on the Tfh induction and RA progression.

Th2 and Th17-Associated Immunopathology Following SARS-CoV-2 Breakthrough Infection in Spike-Vaccinated ACE2-humanized Mice

Vaccines have demonstrated remarkable effectiveness in protecting against COVID-19; however, concerns regarding vaccine-associated enhanced respiratory diseases (VAERD) following breakthrough infections have emerged. Spike protein subunit vaccines for SARS-CoV-2 induce VAERD in hamsters, where aluminum adjuvants promote a Th2-biased immune response, leading to increased type 2 pulmonary inflammation in animals with breakthrough infections. To gain a deeper understanding of the potential risks and the underlying mechanisms of VAERD, we immunized ACE2-humanized mice with SARS-CoV-2 Spike protein adjuvanted with aluminum and CpG-ODN. Subsequently, we exposed them to increasing doses of SARS-CoV-2 to establish a breakthrough infection. The vaccine elicited robust neutralizing antibody responses, reduced viral titers, and enhanced host survival. However, following a breakthrough infection, vaccinated animals exhibited severe pulmonary immunopathology, characterized by a significant perivascular infiltration of eosinophils and CD4+ T cells, along with increased expression of Th2/Th17 cytokines. Intracellular flow cytometric analysis revealed a systemic Th17 inflammatory response, particularly pronounced in the lungs. Our data demonstrate that aluminum/CpG adjuvants induce strong antibody and Th1-associated immunity against COVID-19 but also prime a robust Th2/Th17 inflammatory response, which may contribute to the rapid onset of T cell-mediated pulmonary immunopathology following a breakthrough infection. These findings underscore the necessity for further research to unravel the complexities of VAERD in COVID-19 and to enhance vaccine formulations for broad protection and maximum safety.

Endothelial SARS-CoV-2 infection is not the underlying cause of COVID-19-associated vascular pathology in mice

Endothelial damage and vascular pathology have been recognized as major features of COVID-19 since the beginning of the pandemic. Two main theories regarding how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) damages endothelial cells and causes vascular pathology have been proposed: direct viral infection of endothelial cells or indirect damage mediated by circulating inflammatory molecules and immune mechanisms. However, these proposed mechanisms remain largely untested in vivo. In the present study, we utilized a set of new mouse genetic tools developed in our lab to test both the necessity and sufficiency of endothelial human angiotensin-converting enzyme 2 (hACE2) in COVID-19 pathogenesis. Our results demonstrate that endothelial ACE2 and direct infection of vascular endothelial cells do not contribute significantly to the diverse vascular pathology associated with COVID-19.

Age-dependent acquisition of pathogenicity by SARS-CoV-2 Omicron BA.5

Pathology studies of SARS-CoV-2 Omicron variants of concern (VOC) are challenged by the lack of pathogenic animal models. While Omicron BA.1 and BA.2 replicate in K18-hACE2 transgenic mice, they cause minimal to negligible morbidity and mortality, and less is known about more recent Omicron VOC. Here, we show that in contrast to Omicron BA.1, BA.5-infected mice exhibited high levels of morbidity and mortality, correlating with higher early viral loads. Neither Omicron BA.1 nor BA.5 replicated in brains, unlike most prior VOC. Only Omicron BA.5-infected mice exhibited substantial weight loss, high pathology scores in lungs, and high levels of inflammatory cells and cytokines in bronchoalveolar lavage fluid, and 5- to 8-month-old mice exhibited 100% fatality. These results identify a rodent model for pathogenesis or antiviral countermeasure studies for circulating SARS-CoV-2 Omicron BA.5. Further, differences in morbidity and mortality between Omicron BA.1 and BA.5 provide a model for understanding viral determinants of pathogenicity.

Monoclonal antibodies binding to different epitopes of CD20 differentially sensitize DLBCL to different classes of chemotherapy

Introduction

Rituximab (R), an anti-CD20 monoclonal antibody (mAb) and the world's first approved antibody for oncology patients, was combined with the CHOP chemotherapy regimen and markedly improved the prognosis of all B- cell-derived lymphomas, the most common hematological malignancy worldwide. However, there is a 35% disease recurrence with no advancement in the first-line treatment since R was combined with the archetypal CHOP chemotherapy regimen nearly 30 years ago. There is evidence that R synergizes with chemotherapy, but the pharmacological interactions between R and CHOP or between newer anti-CD20 mAbs and CHOP remain largely unexplored.

Methods

We used in vitro models to score pharmacological interactions between R and CHOP across various lymphoma cell lines. We compared these pharmacological interactions to ofatumumab, a second-generation anti-CD20 mAb, and CHOP. Lastly, we used RNA-sequencing to characterize the transcriptional profiles induced by these two antibodies and potential molecular pathways that mediate their different effects.

Results

We discovered vast heterogeneity in the pharmacological interactions between R and CHOP in a way not predicted by the current clinical classification. We then discovered that R and ofatumumab differentially synergize with the cytotoxic and cytostatic capabilities of CHOP in separate distinct subsets of B-cell lymphoma cell lines, thereby expanding favorable immunochemotherapy interactions across a greater range of cell lines beyond those induced by R-CHOP. Lastly, we discovered these two mAbs differentially modulate genes enriched in the JNK and p38 MAPK family, which regulates apoptosis and proliferation.

Discussion

Our findings were completely unexpected because these mAbs were long considered to be biological and clinical equivalents but, in practice, may perform better than the other in a patient-specific manner. This finding may have immediate clinical significance because both immunochemotherapy combinations are already FDA-approved with no difference in toxicity across phase I, II, and III clinical trials. Therefore, this finding could inform a new precision medicine strategy to provide additional therapeutic benefit to patients with B-cell lymphoma using immunochemotherapy combinations that already meet the clinical standard of care.

Endothelial SARS-CoV-2 infection is not the underlying cause of COVID19-associated vascular pathology in mice

Endothelial damage and vascular pathology have been recognized as major features of COVID-19 since the beginning of the pandemic. Two main theories regarding how Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) damages endothelial cells and causes vascular pathology have been proposed: direct viral infection of endothelial cells or indirect damage mediated by circulating inflammatory molecules and immune mechanisms. However, these proposed mechanisms remain largely untested in vivo. Here, we utilized a set of new mouse genetic tools 1 developed in our lab to test both the necessity and sufficiency of endothelial human angiotensin-converting enzyme 2 (hACE2) in COVID19 pathogenesis. Our results demonstrate that endothelial ACE2 and direct infection of vascular endothelial cells does not contribute significantly to the diverse vascular pathology associated with COVID-19.

Juneteenth in STEMM and the barriers to equitable science

We are 52 Black scientists. Here, we establish the context of Juneteenth in STEMM and discuss the barriers Black scientists face, the struggles they endure, and the lack of recognition they receive. We review racism's history in science and provide institutional-level solutions to reduce the burdens on Black scientists.

Degrading the signal amplifier: ITK as a target for targeted protein degradation

In this issue of Cell Chemical Biology, Jiang and colleagues show for the first time that the Tec kinase ITK can be targeted using PROTAC approaches. This new modality has implications for the treatment of T cell lymphomas, but also potentially for the treatment of T cell-mediated inflammatory diseases, that depend on ITK signaling.

ITK signaling regulates a switch between T helper 17 and T regulatory cell lineages via a calcium-mediated pathway

The balance of pro-inflammatory T helper type 17 (Th17) and anti-inflammatory T regulatory (Treg) cells is crucial in maintaining immune homeostasis in health and disease conditions. Differentiation of naïve CD4+ T cells into Th17/Treg cells is dependent upon T cell receptor (TCR) activation and cytokine signaling, which includes the kinase ITK. Signals from ITK can regulate the differentiation of Th17 and Treg cell fate choice, however, the mechanism remains to be fully understood. We report here that in the absence of ITK activity, instead of developing into Th17 cells under Th17 conditions, naïve CD4+ T cells switch to cells expressing the Treg marker Foxp3 (Forkhead box P3). These switched Foxp3+ Treg like cells retain suppressive function and resemble differentiated induced Tregs in their transcriptomic profile, although their chromatin accessibility profiles are intermediate between Th17 and induced Tregs cells. Generation of the switched Foxp3+ Treg like cells was associated with reduced expression of molecules involved in mitochondrial oxidative phosphorylation and glycolysis, with reduced activation of the mTOR signaling pathway, and reduced expression of BATF. This ITK dependent switch between Th17 and Treg cells was reversed by increasing intracellular calcium. These findings suggest potential strategies for fine tune the TCR signal strength via ITK to regulate the balance of Th17/Treg cells.

Cell-autonomous requirement for ACE2 across organs in lethal mouse SARS-CoV-2 infection

Angiotensin-converting enzyme 2 (ACE2) is the cell-surface receptor for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). While its central role in Coronavirus Disease 2019 (COVID-19) pathogenesis is indisputable, there remains significant debate regarding the role of this transmembrane carboxypeptidase in the disease course. These include the role of soluble versus membrane-bound ACE2, as well as ACE2-independent mechanisms that may contribute to viral spread. Testing these roles requires in vivo models. Here, we report humanized ACE2-floxed mice in which hACE2 is expressed from the mouse Ace2 locus in a manner that confers lethal disease and permits cell-specific, Cre-mediated loss of function, and LSL-hACE2 mice in which hACE2 is expressed from the Rosa26 locus enabling cell-specific, Cre-mediated gain of function. Following exposure to SARS-CoV-2, hACE2-floxed mice experienced lethal cachexia, pulmonary infiltrates, intravascular thrombosis and hypoxemia-hallmarks of severe COVID-19. Cre-mediated loss and gain of hACE2 demonstrate that neuronal infection confers lethal cachexia, hypoxemia, and respiratory failure in the absence of lung epithelial infection. In this series of genetic experiments, we demonstrate that ACE2 is absolutely and cell-autonomously required for SARS-CoV-2 infection in the olfactory epithelium, brain, and lung across diverse cell types. Therapies inhibiting or blocking ACE2 at these different sites are likely to be an effective strategy towards preventing severe COVID-19.

Effective differentiation of double negative thymocytes requires high fidelity replication of mitochondrial DNA in an age dependent manner

One of the most proliferative periods for T cells occurs during their development in the thymus. Increased DNA replication can result in increased DNA mutations in the nuclear genome, but also in mitochondrial genomes. A high frequency of mitochondrial DNA mutations can lead to abnormal mitochondrial function and have negative implications on human health. Furthermore, aging is accompanied by an increase in such mutations through oxidative damage and replication errors. Increased mitochondrial DNA mutations cause loss of mitochondrial protein function, and decrease energy production, substrates, and metabolites. Here we have evaluated the effect of increased mitochondrial DNA mutations on T cell development in the thymus. Using mice carrying a mutant mitochondrial DNA polymerase γ (PolG) that causes increased mitochondrial DNA mutations, we show that high fidelity replication of mitochondrial DNA is pivotal for proper T cell development. Reducing the fidelity of mitochondrial DNA replication results in a premature age-dependent reduction in the total number of CD4/CD8 double negative and double positive thymocytes. Analysis of mitochondrial density in thymocyte subpopulations suggests that this may be due to reduced proliferation in specific double negative stages. Taken together, this work suggests that T cell development is regulated by the ability of mitochondria to faithfully replicate their DNA.

Multivalent viral particles elicit safe and efficient immunoprotection against Nipah Hendra and Ebola viruses

Experimental vaccines for the deadly zoonotic Nipah (NiV), Hendra (HeV), and Ebola (EBOV) viruses have focused on targeting individual viruses, although their geographical and bat reservoir host overlaps warrant creation of multivalent vaccines. Here we explored whether replication-incompetent pseudotyped vesicular stomatitis virus (VSV) virions or NiV-based virus-like particles (VLPs) were suitable multivalent vaccine platforms by co-incorporating multiple surface glycoproteins from NiV, HeV, and EBOV onto these virions. We then enhanced the vaccines' thermotolerance using carbohydrates to enhance applicability in global regions that lack cold-chain infrastructure. Excitingly, in a Syrian hamster model of disease, the VSV multivalent vaccine elicited safe, strong, and protective neutralizing antibody responses against challenge with NiV, HeV, or EBOV. Our study provides proof-of-principle evidence that replication-incompetent multivalent viral particle vaccines are sufficient to provide protection against multiple zoonotic deadly viruses with high pandemic potential.

High-Efficiency Retroviral Transduction for Type 1 Regulatory T Cell Differentiation

Type 1 regulatory T (Tr1) cells are an immunoregulatory CD4 ⁺ Foxp3- IL-10 ^high T cell subset with therapeutic potential for various inflammatory diseases. Retroviral (RV) transduction has been a valuable tool in defining the signaling pathways and transcription factors that regulate Tr1 differentiation and suppressive function. This protocol describes a method for RV transduction of naïve CD4 ⁺ T cells differentiating under Tr1 conditions, without the use of reagents such as polybrene or RetroNectin. A major advantage of this protocol over others is that it allows for the role of genes of interest on both differentiation and function of Tr1 cells to be interrogated. This is due to the high efficiency of RV transduction combined with the use of an IL10 ^GFP /Foxp3 ^RFP dual reporter mouse model, which enables successfully transduced Tr1 cells to be identified and sorted for functional assays. In addition, this protocol may be utilized for dual/multiple transduction approaches and transduction of other lymphocyte populations, such as CD8 ⁺ T cells.

Neuropilin-1 Identifies a New Subpopulation of TGF-β-Induced Foxp3+ Regulatory T Cells With Potent Suppressive Function and Enhanced Stability During Inflammation

CD4⁺Foxp3⁺ regulatory T cells (Tregs) play a crucial role in preventing autoimmunity and inflammation. There are naturally-derived in the thymus (tTreg), generated extrathymically in the periphery (pTreg), and induced in vitro culture (iTreg) with different characteristics of suppressiveness, stability, and plasticity. There is an abundance of published data on neuropilin-1 (Nrp-1) as a tTreg marker, but little data exist on iTreg. The fidelity of Nrp-1 as a tTreg marker and its role in iTreg remains to be explored. This study found that Nrp-1 was expressed by a subset of Foxp3⁺CD4⁺T cells in the central and peripheral lymphoid organs in intact mice, as well as in iTreg. Nrp-1⁺iTreg and Nrp-1^-iTreg were adoptively transferred into a T cell-mediated colitis model to determine their ability to suppress inflammation. Differences in gene expression between Nrp-1⁺ and Nrp-1^-iTreg were analyzed by RNA sequencing. We demonstrated that the Nrp-1⁺ subset of the iTreg exhibited enhanced suppressive function and stability compared to the Nrp-1^- counterpart both in vivo and in vitro, partly depending on IL-10. We found that Nrp-1 is not an exclusive marker of tTreg, however, it is a biomarker identifying a new subset of iTreg with enhanced suppressive function, implicating a potential for Nrp-1⁺iTreg cell therapy for autoimmune and inflammatory diseases.

A TMPRSS2 inhibitor acts as a pan-SARS-CoV-2 prophylactic and therapeutic

The COVID-19 pandemic caused by the SARS-CoV-2 virus remains a global public health crisis. Although widespread vaccination campaigns are underway, their efficacy is reduced owing to emerging variants of concern1,2. Development of host-directed therapeutics and prophylactics could limit such resistance and offer urgently needed protection against variants of concern3,4. Attractive pharmacological targets to impede viral entry include type-II transmembrane serine proteases (TTSPs) such as TMPRSS2; these proteases cleave the viral spike protein to expose the fusion peptide for cell entry, and thus have an essential role in the virus lifecycle5,6. Here we identify and characterize a small-molecule compound, N-0385, which exhibits low nanomolar potency and a selectivity index of higher than 106 in inhibiting SARS-CoV-2 infection in human lung cells and in donor-derived colonoids7. In Calu-3 cells it inhibits the entry of the SARS-CoV-2 variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta). Notably, in the K18-human ACE2 transgenic mouse model of severe COVID-19, we found that N-0385 affords a high level of prophylactic and therapeutic benefit after multiple administrations or even after a single administration. Together, our findings show that TTSP-mediated proteolytic maturation of the spike protein is critical for SARS-CoV-2 infection in vivo, and suggest that N-0385 provides an effective early treatment option against COVID-19 and emerging SARS-CoV-2 variants of concern.

ITK signaling regulates IL-10 production by CD8+ T cells and lung immunopathology during influenza infection

Influenza (flu) infections cause 250,000 deaths and 3–5 million cases of severe illness during the average flu season. Severe influenza infections are associated with a combination of strong pro-inflammatory and weak anti-inflammatory immune responses. Production of the immunomodulatory cytokine IL-10 by T cells restricts immunopathology during flu infections, however knowledge of the signaling pathways regulating IL-10 induction during flu is limited. Using IL-10GFP reporter mouse models, we found Interleukin-2 inducible T cell kinase (ITK), a critical component in T cell receptor (TCR) signaling, regulates the development of IL-10-producing CD8+ T cells during influenza A infection. Compared to wild type (WT) mice, Itk−/− mice displayed increased morbidity and mortality after influenza infection, accompanied by a significant reduction of IL-10-producing CD8+ T cells in the airways. The absence of ITK and chemical inhibition of the PI3K/AKT/mTOR signaling pathway impaired both BLIMP1 expression and IL-10 production in CD8+ T cells in vitro. Introduction of Blimp-1 or a constitutively active AKT mutant via retroviral transduction rescued IL-10 production and Blimp-1 expression in Itk−/− CD8+ T cells. Utilizing a transgenic allele sensitive Itk (ITKas) mouse model to specifically inhibit ITK kinase activity in coculture, we found ITK kinase activity is not required for the suppressive function of IL-10 producing CD8+ T cells. Together, our data suggests that ITK is a critical regulator of the development and suppressive function of IL-10 producing CD8+ T cells and flu-induced pulmonary immunopathology. Modulating ITK signaling may be a strategy for regulating immunopathology due to respiratory viral infections.

This work was supported in part by grants from the National Institutes of Health (R01 AI151139, R56 AI146226 and P20 GM130555). W. Huang also received research support from MegaRobo Technologies Corporation.

ITK tunes the Th17/Treg switch response by controlling calcium dependent signaling

Naïve CD4+ T cells can differentiate into pro inflammatory T helper type 17 (Th17) and anti inflammatory T regulatory (Treg) lineages following T cell receptor (TCR) activation. The strength of the TCR signal is tuned by Interleukin-2 inducible T cell Kinase (ITK) and ITK can tune the development of Th17 and Treg cells. ITK signals can also tune a Th17/Treg switch under Th17 conditions. How ITK mediated tuning of TCR signal control naïve CD4+ T cell commitment into Th17/Treg lineages is unclear. Here we used ITK inhibitors, conventional ITK and allele specific ITK (ITKas) IL17 GFP/Foxp3 RFP reporter mice, to track naïve CD4+ T cell commitment into Th17/Treg lineages. Under Th17 conditions, reduced TCR signal strength in absence of ITK activity/expression, tuned naïve CD4+ T cell fate by reducing Th17 differentiation and inducing switch to cells resembling Tregs expressing Foxp3. The ITKas model showed this switch is due to specific ITK inhibition. The switched Treg like cells resemble Tregs by expression of Treg markers (CD25, CTLA4, PD1) and suppression of effector T cell proliferation. Transcriptomic analysis of switched Treg like cells by RNA Seq indicate they resemble Tregs, with reduced Th17 (Rorc, Il17) and increased Treg (Foxp3, Nrp1, Ikzf2) gene expression. Analysis of chromatin accessibility by ATAC Seq indicated closed loci for Th17 (Rorc, Il17) genes. Activating intracellular calcium dependent pathways led to a loss of the Th17/Treg switch response in naïve CD4+ T cell commitment, effectively bypassing ITK mediated tuning of the TCR signal critical for the switch response. In conclusion, we show here ITK tunes a Th17/Treg switch response in naïve CD4+ T cell commitment under Th17 conditions by controlling calcium dependent signaling.

Supported by grants from NIH (NIH AI129422).

SARS-CoV-2 infection of olfactory epithelial cells and neurons drives acute lung injury and lethal COVID-19 in mice

Lethal COVID-19 is associated with respiratory failure that is thought to be caused by acute respiratory distress syndrome (ARDS) secondary to pulmonary infection. To date, the cellular pathogenesis has been inferred from studies describing the expression of ACE2, a transmembrane protein required for SARS-CoV-2 infection, and detection of viral RNA or protein in infected humans, model animals, and cultured cells. To functionally test the cellular mechanisms of COVID-19, we generated hACE2 ^fl animals in which human ACE2 (hACE2) is expressed from the mouse Ace2 locus in a manner that permits cell-specific, Cre-mediated loss of function. hACE2 ^fl animals developed lethal weight loss and hypoxemia within 7 days of exposure to SARS-CoV-2 that was associated with pulmonary infiltrates, intravascular thrombosis and patchy viral infection of lung epithelial cells. Deletion of hACE2 in lung epithelial cells prevented viral infection of the lung, but not weight loss, hypoxemia or death. Inhalation of SARS-CoV-2 by hACE2 ^fl animals resulted in early infection of sustentacular cells with subsequent infection of neurons in the neighboring olfactory bulb and cerebral cortexâ€" events that did not require lung epithelial cell infection. Pharmacologic ablation of the olfactory epithelium or Foxg1 ^Cre mediated deletion of hACE2 in olfactory epithelial cells and neurons prevented lethality and neuronal infection following SARS-CoV-2 infection. Conversely, transgenic expression of hACE2 specifically in olfactory epithelial cells and neurons in Foxg1 ^Cre ; LSL- hACE2 mice was sufficient to confer neuronal infection associated with respiratory failure and death. These studies establish mouse loss and gain of function genetic models with which to genetically dissect viral-host interactions and demonstrate that lethal disease due to respiratory failure may arise from extrapulmonary infection of the olfactory epithelium and brain. Future therapeutic efforts focused on preventing olfactory epithelial infection may be an effective means of protecting against severe COVID-19.

Interleukin-2-inducible T-cell kinase (Itk) signaling regulates potent noncanonical regulatory T cells

Regulatory T cells (Tregs) play an important role in controlling autoimmunity and limiting tissue damage and inflammation. IL2-inducible T cell kinase (Itk) is part of the Tec family of tyrosine kinases and is a critical component of T cell receptor mediated signaling. Here, we showed that either genetic ablation of Itk signaling or inhibition of Itk signaling pathways resulted in increased frequency of "noncanonical" CD4+ CD25- FOXP3+ Tregs (ncTregs), as well as of "canonical" CD4+ CD25+ FOXP3+ Tregs (canTregs). Using in vivo models, we showed that ncTregs can avert the formation of acute graft-versus-host disease (GVHD), in part by reducing conventional T cell proliferation, proinflammatory cytokine production, and tissue damage. This reduction in GVHD occurred without disruption of graft-versus-leukaemia (GVL) effects. RNA sequencing revealed that a number of effector, cell adhesion, and migration molecules were upregulated in Itk-/- ncTregs. Furthermore, disrupting the SLP76: ITK interaction using a specific peptide inhibitor led to enhanced Treg development in both mouse and primary human cells. This peptide inhibitor also significantly reduced inflammatory cytokine production in primary GVHD patient samples and mouse T cells without causing cell death or apoptosis. We provide evidence that specifically targeting Itk signaling could be a therapeutic strategy to treat autoimmune disorders.

Targeting of the Tec Kinase ITK Drives Resolution of T Cell-Mediated Colitis and Emerges as Potential Therapeutic Option in Ulcerative Colitis

BACKGROUND & AIMS

The molecular checkpoints driving T cell activation and cytokine responses in ulcerative colitis (UC) are incompletely understood. Here, we studied the Tec kinase ITK in UC.

METHODS

We analyzed patients with inflammatory bowel disease (n = 223) and evaluated ITK activity as well as the functional effects of cyclosporine-A (CsA). In addition, 3 independent murine colitis models were used to investigate the functional role of ITK. Finally, the activity of ITK was blocked via pharmacological inhibitors and genetically engineered mice. Readout parameters were mini-endoscopy, histopathology, mucosal T cell apoptosis, and cytokine production.

RESULTS

We found an expansion of pITK-expressing mucosal CD4+ T cells in UC rather than Crohn's disease that correlated with disease severity. CsA suppressed activation of ITK in cultured CD4+ T cells and calcineurin-containing microclusters adjacent to the T cell receptor signaling complex. Functionally, the capacity of CsA to suppress activity of experimental colitis was critically dependent on ITK. Genetic inactivation of Itk via gene targeting or induction of allele-sensitive Itk mutants prevented experimental colitis in 3 colitis models, and treatment with pharmacological ITK blockers suppressed established colitis. In addition, ITK controlled apoptosis and activation of mucosal Th2 and Th17 lymphocytes via NFATc2 signaling pathways.

CONCLUSIONS

ITK activation was detected in UC and could be down-regulated in cultured T cells by CsA administration. Selective targeting of ITK emerges as an attractive approach for treatment of chronic intestinal inflammation and potentially UC by driving resolution of mucosal inflammation.

Eosinophils are dispensable for development of MOG35-55-induced experimental autoimmune encephalomyelitis in mice

Experimental autoimmune encephalomyelitis (EAE) represents the mouse model of multiple sclerosis, a devastating neurological disorder. EAE development and progression involves the infiltration of different immune cells into the brain and spinal cord. However, less is known about a potential role of eosinophil granulocytes for EAE disease pathogenesis. In the present study, we found enhanced eosinophil abundance accompanied by increased concentration of the eosinophil chemoattractant eotaxin-1 in the spinal cord in the course of EAE induced in C57BL/6 mice by immunization with MOG_35-55 peptide. However, the absence of eosinophils did not affect neuroinflammation, demyelination and clinical development or severity of EAE, as assessed in ∆dblGATA1 eosinophil-deficient mice. Taken together, despite their enhanced abundance in the inflamed spinal cord during disease progression, eosinophils were dispensable for EAE development.

Konjac Glucomannan Oligosaccharides Prevent Intestinal Inflammation Through SIGNR1-Mediated Regulation of Alternatively Activated Macrophages

SCOPE

Konjac glucomannan oligosaccharides (KMOS) are prebiotics and may improve intestinal immunity through modulation of macrophage function. However, the underlying molecular mechanisms were unclear.

METHODS AND RESULTS

Using a mouse model of dextran sulfated sodium (DSS)-induced acute colitis, the study demonstrates here that KMOS (400 mg^-1 kg^-1 d^-1 ) can ameliorate intestinal inflammation in a macrophage dependent manner. Oral exposure to KMOS prevents DSS-induced intestinal pathology, improves epithelial integrity, and decreases accumulation of colonic inflammatory leukocytes and cytokines. The therapeutic effects of KMOS are dependent on the function of macrophages, as depletion of macrophages abolished the effects. In colonic lamina propria of DSS-treated mice, as well as in vitro culture of bone marrow derived macrophages (BMDMs), KMOS skews reprogramming of classically activated macrophages (CAM/M1) into alternatively activated macrophages (AAM/M2). The study further determines that the activation of SIGNR1/phospho-c-Raf (S338)/phospho-p65 (S276)/acetyl-p65 (K310) pathway is responsible for KMOS-induced AAM/M2 polarization. Blockage of SIGNR1 abolishes KMOS-induced AAM/M2 polarization of activated macrophages, expression of phospho-p65 (S276) in colonic macrophages, and alleviation of DSS-induced colitis in mice, suggesting that SIGNR1 is critical for macrophage responses to KMOS.

CONCLUSIONS

This study reveals a SIGNR1-mediated macrophage-dependent pathway that supports regulatory function of KMOS in host immunity and intestinal homeostasis.

Human Wnt/β-Catenin Regulates Alloimmune Signaling during Allogeneic Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is one of the most widely applied forms of adoptive immunotherapy for the treatment of hematological malignancies. Detrimental graft-versus-host disease (GVHD), but also beneficial graft-versus-leukemia (GVL) effects occurring after allo-HSCT are largely mediated by alloantigen-reactive donor T cells in the graft. Separating GVHD from GVL effects is a formidable challenge, and a greater understanding of donor T cell biology is required to accomplish the uncoupling of GVHD from GVL. Here, we evaluated the role of β-catenin in this process. Using a unique mouse model of transgenic overexpression of human β-catenin (Cat-Tg) in an allo-HSCT model, we show here that T cells from Cat-Tg mice did not cause GVHD, and surprisingly, Cat-Tg T cells maintained the GVL effect. Donor T cells from Cat-Tg mice exhibited significantly lower inflammatory cytokine production and reduced donor T cell proliferation, while upregulating cytotoxic mediators that resulted in enhanced cytotoxicity. RNA sequencing revealed changes in the expression of 1169 genes for CD4, and 1006 genes for CD8⁺ T cells involved in essential aspects of immune response and GVHD pathophysiology. Altogether, our data suggest that β-catenin is a druggable target for developing therapeutic strategies to reduce GVHD while preserving the beneficial GVL effects following allo-HSCT treatment.

A novel highly potent inhibitor of TMPRSS2-like proteases blocks SARS-CoV-2 variants of concern and is broadly protective against infection and mortality in mice

The COVID-19 pandemic caused by the SARS-CoV-2 virus remains a global public health crisis. Although widespread vaccination campaigns are underway, their efficacy is reduced against emerging variants of concern (VOCs) ^1,2 . Development of host-directed therapeutics and prophylactics could limit such resistance and offer urgently needed protection against VOCs ^3,4 . Attractive pharmacological targets to impede viral entry include type-II transmembrane serine proteases (TTSPs), such as TMPRSS2, whose essential role in the virus lifecycle is responsible for the cleavage and priming of the viral spike protein ^5-7 . Here, we identify and characterize a small-molecule compound, N-0385, as the most potent inhibitor of TMPRSS2 reported to date. N-0385 exhibited low nanomolar potency and a selectivity index of >10 ⁶ at inhibiting SARS-CoV-2 infection in human lung cells and in donor-derived colonoids ⁸ . Importantly, N-0385 acted as a broad-spectrum coronavirus inhibitor of two SARS-CoV-2 VOCs, B.1.1.7 and B.1.351. Strikingly, single daily intranasal administration of N-0385 early in infection significantly improved weight loss and clinical outcomes, and yielded 100% survival in the severe K18-human ACE2 transgenic mouse model of SARS-CoV-2 disease. This demonstrates that TTSP-mediated proteolytic maturation of spike is critical for SARS-CoV-2 infection in vivo and suggests that N-0385 provides a novel effective early treatment option against COVID-19 and emerging SARS-CoV-2 VOCs.

ITK regulates IL-10 production by CD8+ T cells and lung immunopathology during influenza infection

Respiratory viral infections are a major cause of human morbidity and mortality. Influenza (flu) infections cause 250,000 deaths and 3–5 million cases of severe illness during the average flu season. Severe flu infections are associated with a combination of strong pro-inflammatory and weak anti-inflammatory immune responses. Production of the immunomodulatory cytokine IL-10 by T cells restricts immunopathology during flu infections, however our knowledge of the signaling pathways regulating IL-10 induction during flu is limited. Using IL-10GFP reporter mouse models, we found that Interleukin-2 inducible T cell kinase (ITK), a critical component in T cell receptor (TCR) signaling, regulates immunopathology and the development of IL-10-producing CD8+ T cells in the airways during influenza A infection. Utilizing alternative coculture, the model antigen ovalbumin (OVA), and transgenic TCR specific for OVA in CD8+ T cells (OTI) adoptive transfer, we determined that ITK regulates flu antigen-specific IL-10+CD8+ T cell differentiation in a CD8+ T cell intrinsic and extrinsic manner. Exogenous IL-2 rescued IL-10 production by Itk−/− CD8+ T cells, in vitro and in vivo, suggesting that ITK may play a role in IL-2-producing T helper cells that promote IL-10 production in CD8+ T cells. The absence of ITK impaired the expression of transcription factors (TFs) IRF4 and Blimp-1, and retroviral transduction enabling the reintroduction of these TFs could partially rescue IL-10 production in Itk−/− CD8+ T cells. Our data suggests that ITK is a critical regulator of IL-10 production by CD8+ T cells and flu-induced pulmonary immunopathology. Modulating ITK signaling may be a strategy for regulating immunopathology due to viral infections.

Interleukin-2 inducible T cell kinase functions as a molecular switch to fine tune differentiation of naive T helper cells in pro/anti-inflammatory effector T cell lineages

Naïve CD4+ T helper cells differentiate into effector CD4+ T cells with pro/anti-inflammatory functions upon receipt of signals from the T cell receptor (TCR) in presence of cytokines in the environment. Interleukin-2 inducible T cell kinase (ITK) has been shown to control the strength of signals downstream of the TCR. Here we have investigated the potential of ITK to act as a molecular switch in controlling T cell differentiation fate. Our results demonstrate in the absence of ITK expression/activity, naïve CD4+ T cells activated under conditions that promote differentiation into pro-inflammatory T helper type-17 (Th17) cells fail to differentiate into Th17 cells and instead switch into T cells expressing the T regulatory (Treg) lineage specific transcription factor Forkhead Box P3 (FoxP3). Similarly, we found that naïve CD4+ T cells activated to differentiate into anti-inflammatory Type 1 regulatory (Tr1) cells in the absence of ITK expression/activity fail to differentiate into Tr1 cells and instead switch into expressing the T helper type-1 (Th1) lineage specific T-box transcription factor (T-Bet). The switched FoxP3 expressing T cells resemble Tregs by their expression of Treg specific markers and have anti-inflammatory properties in suppressing effector T cell proliferation. In addition the switched T-Bet expressing T cells resemble Th1 cells by their expression of Th1 specific markers and the Th1 effector cytokine Interferon γ (IFNγ). This work suggest that signals regulated by ITK may function as a molecular switch to control Th17/Treg and Tr1/Th1 axes, highlighting the potential of manipulating ITK to control the balance of pro/anti-inflammatory T cells in immune disorders.

Targeting SLP76:ITK interaction separates GVHD from GVL in allo-HSCT

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative therapy for relapsed hematological malignancies due to graft-versus-leukemia (GVL) activity mediated by alloreactive donor T cells. However, graft-versus-host disease (GVHD) is also primarily mediated by the same donor T cells. Here we assessed the effect of attenuating TCR-mediated SLP76:ITK interaction in T cell-mediated GVL vs. GVHD effects after allo-HSCT. Neither CD8+ T cells nor CD4+ donor T cells from mice expressing a tyrosine to phenylalanine mutation at position 145 (Y145F) of the adapter protein SLP-76 caused GVHD, T cells cells preserved GVL effects after allogeneic transplantation. SLP76Y145FKI CD8+ and CD4+ donor T cells also produce less inflammatory cytokines and show decreased migration to GVHD target organs such as the liver and small intestine, while maintaining GVL efficacy against primary B-cell acute lymphoblastic leukemia (B-ALL). We also report the development of a novel peptide that can specifically inhibit SLP76 and ITK interactions, which results in decreased phosphorylation of PLCγ1 and ERK, and decreased cytokine production in human T cells. This peptide inhibited donor T cell-mediated GVHD while maintaining GVL effects. Altogether, our data suggest that inhibiting SLP76:ITK interaction could be a therapeutic strategy to reduce GVHD while retaining the beneficial GVL effects after allo-HSCT treatment.

Targeting SLP76:ITK interaction separates GVHD from GVL in allo-HSCT

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for hematological malignancies, due to graft-versus-leukemia (GVL) activity mediated by alloreactive donor T cells. However, graft-versus-host disease (GVHD) is also mediated by these cells. Here, we assessed the effect of attenuating TCR-mediated SLP76:ITK interaction in GVL vs. GVHD effects after allo-HSCT. CD8+ and CD4+ donor T cells from mice expressing a Y145F mutation in SLP-76 did not cause GVHD but preserved GVL effects against B-ALL cells. SLP76Y145FKI CD8+ and CD4+ donor T cells also showed less inflammatory cytokine production and migration to GVHD target organs. We developed a novel peptide to specifically inhibit SLP76:ITK interactions, resulting in decreased phosphorylation of PLCγ1 and ERK, decreased cytokine production in human T cells, and separation of GVHD from GVL effects. Altogether, our data suggest that inhibiting SLP76:ITK interaction could be a therapeutic strategy to separate GVHD from GVL effects after allo-HSCT treatment.

Effect of Perfluorooctanesulfonic acid (PFOS) on immune cell development and function in mice

Perfluoroctanesulfonate (PFOS) belongs to a larger family of compounds known as Per- and polyfluoroalkyl substances (PFAS). The strength of the carbon-fluorine bond makes PFOS extremely resistant to environmental degradation. Due to its persistent nature, research has been directed to elucidating possible health effects of PFOS on humans and laboratory animals. Here we have explored the effects of PFOS exposure on immune development and function in mice. We exposed adult mice to 3 and 1.5 μg/kg/day of PFOS for 2 and 4 weeks, respectively, and examined the effects of PFOS exposure on populations of T cells, B cells, and granulocytes. These doses of PFOS resulted in serum levels of approximately 100 ng/mL with no weight loss during exposure. We find that PFOS does not affect T-cell development during this time. However, while PFOS exposure reduced immune cell populations in some organs, it also led to an increase in the numbers of cells in others, suggesting possible relocalization of cells. We also examined the effect of PFOS on the response to influenza virus infection. We find that exposure to PFOS at 1.5 μg/kg/day of PFOS for 4 weeks does not affect weight loss or survival, nor is viral clearance affected. Analysis of antibody and T cell specific antiviral responses indicate that at this concentration, PFOS does not suppress the immune cell development or antigen specific immune response.

TCR/ITK Signaling in Type 1 Regulatory T cells

Type 1 regulatory T (Tr1) cells can modulate inflammation through multiple direct and indirect molecular and cellular mechanisms and have demonstrated potential for anti-inflammatory therapies. Tr1 cells do not express the master transcription factor of conventional regulatory T cells, Foxp3, but express high levels of the immunomodulatory cytokine, IL-10. IL-2-inducible T-cell kinase (ITK) is conserved between mouse and human and is highly expressed in T cells. ITK signaling downstream of the T-cell receptor (TCR) is critical for T-cell subset differentiation and function. Upon activation by TCR, ITK is critical for Ras activation, leading to downstream activation of MAPKs and upregulation of IRF4, which further enable Tr1 cell differentiation and suppressive function. We summarize here the structure, signaling pathway, and function of ITK in T-cell lineage designation, with an emphasis on Tr1 cell development and function.

Targeting Interleukin-2-Inducible T-Cell Kinase (ITK) Differentiates GVL and GVHD in Allo-HSCT

Allogeneic hematopoietic stem cell transplantation is a potentially curative procedure for many malignant diseases. Donor T cells prevent disease recurrence via graft-versus-leukemia (GVL) effect. Donor T cells also contribute to graft-versus-host disease (GVHD), a debilitating and potentially fatal complication. Novel treatment strategies are needed which allow preservation of GVL effects without causing GVHD. Using murine models, we show that targeting IL-2-inducible T cell kinase (ITK) in donor T cells reduces GVHD while preserving GVL effects. Both CD8⁺ and CD4⁺ donor T cells from Itk^-/- mice produce less inflammatory cytokines and show decrease migration to GVHD target organs such as the liver and small intestine, while maintaining GVL efficacy against primary B-cell acute lymphoblastic leukemia (B-ALL). Itk^-/- T cells exhibit reduced expression of IRF4 and decreased JAK/STAT signaling activity but upregulating expression of Eomesodermin (Eomes) and preserve cytotoxicity, necessary for GVL effect. Transcriptome analysis indicates that ITK signaling controls chemokine receptor expression during alloactivation, which in turn affects the ability of donor T cells to migrate to GVHD target organs. Our data suggest that inhibiting ITK could be a therapeutic strategy to reduce GVHD while preserving the beneficial GVL effects following allo-HSCT treatment.

TCR Signal Strength and Antigen Affinity Regulate CD8+ Memory T Cells

CD8⁺ T cells play a critical role in adaptive immunity, differentiating into CD8⁺ memory T cells that form the basis of protective cellular immunity. Vaccine efficacy is attributed to long-term protective immunity, and understanding the parameters that regulate development of CD8⁺ T cells is critical to the design of T cell-mediated vaccines. We show in this study using mouse models that two distinct parameters, TCR signal strength (regulated by the tyrosine kinase ITK) and Ag affinity, play important but separate roles in modulating the development of memory CD8⁺ T cells. Unexpectedly, our data reveal that reducing TCR signal strength along with reducing Ag affinity for the TCR leads to enhanced and accelerated development of CD8⁺ memory T cells. Additionally, TCR signal strength is able to regulate CD8⁺ T cell effector cytokine R production independent of TCR Ag affinity. Analysis of RNA-sequencing data reveals that genes for inflammatory cytokines/cytokine receptors are significantly altered upon changes in Ag affinity and TCR signal strength. Furthermore, our findings show that the inflammatory milieu is critical in regulating this TCR signal strength-mediated increase in memory development, as both CpG oligonucleotide treatment or cotransfer of wild-type and Itk^-/- T cells eliminates the observed increase in memory cell formation. These findings suggest that TCR signal strength and Ag affinity independently contribute to CD8⁺ memory T cell development, which is modulated by inflammation, and suggest that manipulating TCR signal strength along with Ag affinity, may be used to tune the development of CD8⁺ memory T cells during vaccine development.

BTK/ITK dual inhibitors: Modulating immunopathology and lymphopenia for COVID-19 therapy

Bruton's tyrosine kinase (BTK) signaling is involved in innate immune responses and regulates the production of proinflammatory cytokines that can contribute to COVID‐19 immunopathology. Clinical trials with BTK inhibitors in COVID‐19 treatment have been proposed, and previous studies have attempted to investigate the therapeutic effects of ibrutinib and underlying mechanisms in treating viral pneumonia. These attempts, however, did not consider potential off target effect of BTK inhibitors on T cell differentiation, function, and survival, which may be beneficial in treatment for COVID‐19. Here, we summarize the current knowledge of BTK/IL‐2‐inducible T‐cell kinase (ITK) signaling in immunopathology and lymphopenia and discuss the potential of BTK/ITK dual inhibitors such as ibrutinib in modulating immunopathology and lymphopenia, for COVID‐19 therapy.

The Lifebox Surgical Headlight Project: engineering, testing, and field assessment in a resource-constrained setting

BACKGROUND

Poor surgical lighting represents a major patient safety issue in low-income countries. This study evaluated device performance and undertook field assessment of high-quality headlights in Ethiopia to identify critical attributes that might improve safety and encourage local use.

METHODS

Following an open call for submissions (December 2018 to January 2019), medical and technical (non-medical) headlights were identified for controlled specification testing on 14 prespecified parameters related to light quality/intensity, mounting and battery performance, including standardized illuminance measurements over time. The five highest-performing devices (differential illumination, colour rendering, spot size, mounting and battery duration) were distributed to eight Ethiopian surgeons working in resource-constrained facilities. Surgeons evaluated the devices in operating rooms, and in a comparative session rated each headlight in terms of performance and willingness to purchase.

RESULTS

Of 25 submissions, eight headlights (6 surgical and 2 technical) met the criteria for full specification testing. Scores ranged from 8 to 12 (of 14), with differential performance in lighting, mounting and battery domains. Only two headlights met the illuminance parameters of more than 35 000 lux during initial testing, and no headlight satisfied all minimum specifications. Of the five headlights evaluated in Ethiopia, daily operation logbooks noted variability in surgeons' opinions of lighting quality (6-92 per cent) and spot size (0-92 per cent). Qualitative interviews also yielded important feedback, including preference for easy transport. Surgeons sought high quality with price sensitivity (using out-of-pocket funds) and identified the least expensive but high-functioning device as their first choice.

CONCLUSION

No device satisfied all the predetermined specifications, and large price discrepancies were critical factors leading surgeons' choices. The favoured device is undergoing modification by the manufacturer based on design feedback so an affordable, high-quality surgical headlight crafted specifically for the needs of resource-constrained settings can be used to improve surgical safety.

The Role of Tyrosine Kinase Itk in T helper 17 and T regulatory cells in Hypersensitivity Pneumonitis

The balance of inflammatory and suppressive cytokines is critical in controlling inflammatory responses, and the pro- and anti-inflammatory cytokines IL17A and IL10 has been implicated in numerous pulmonary inflammatory diseases. The tyrosine kinase, Itk, plays a critical role in T cell activation. Itk is required for the development of Th17 cells and their production of IL17A in allergic lung inflammation. Furthermore, Type I regulatory and Foxp3+ T regulatory (Tregs) cells, producers of IL10, are positively and negatively regulated by Itk respectively. Farmer’s lung, a subset of hypersensitivity pneumonitis, develops due to repeated exposure to the bacteria Saccharopolyspora rectivirgula (SR) and is dependent on IL17A and regulated by IL10. Surprisingly, exposure to SR drives robust CD4+ T cell IL17A response even in the absence of Itk, with pulmonary inflammation. Transcriptomic analysis of sort purified WT and Itk−/− IL17A producing CD4+ T cells from SR-exposed mice revealed an enrichment of Notch signaling pathway in the absence of Itk. SR also induced the Itk independent development of a population of IL17A producing Foxp3+ Tregs cells, and a significant decrease in IL10 producing Tr1 cells. These data suggest that Itk regulates the expression of IL10, and pathogenic Th17 cells via Notch signaling. These studies suggest that TCR signaling through Itk differentially regulates the development of inflammatory Th17 cells and suppressive Tregs and Tr1 cells in response to SR exposure. Understanding how Itk modulates the development of Th17/Treg cytokine responses will allow us to better understand the precise role of Itk in the regulating the balance of pro- and anti-inflammatory cytokine production during airway inflammation.

ITK regulates IL-10 production by CD8+ T cells and lung immunopathology during influenza infection

Influenza (flu) infections cause 250,000 deaths and 3–5 million cases of severe illness during the average flu season. Severe influenza infections are associated with a combination of strong pro-inflammatory and weak anti-inflammatory immune responses. Production of the anti-inflammatory cytokine IL-10 by T cells restricts immunopathology during flu infections, however our knowledge of the signaling pathways regulating IL-10 induction is limited. Using IL-10GFP reporter mouse models, we found that Interleukin-2 inducible T cell kinase (ITK), a critical component in T cell receptor (TCR) signaling, regulates the development of IL-10-producing CD8+ T cells during influenza A infection. Compared to wild type (WT) mice, Itk−/− mice displayed increased morbidity and mortality after influenza infection, accompanied by a significant reduction of IL-10 producing CD8+ T cells in the airways. Using the model antigen ovalbumin (OVA) and transgenic TCR specific for OVA in CD8+ T cells (OTI), along with an allele sensitive mutation in the ITK kinase domain, we determine that ITK regulates IL-10 production in antigen-specific CD8+ T cells in a kinase dependent manner. RNA sequencing and multiparametric flow cytometric analyses revealed that ITK differentially regulates the expression of cell surface markers and transcription factors that are involved in regulating T cell differentiation, effector and memory phenotypes. Together, our data suggests that ITK is a critical regulator of IL-10 production by CD8+ T cells and regulate immunopathology during influenza infection. Modulating ITK signaling may be a strategy for regulating immunopathology due to viral infections.

Heterogeneity of regulatory T cells during lung inflammation

Pulmonary inflammation is the leading cause of respiratory illness worldwide. Although strong T cell responses are desired for defending the hosts against infections, the cytotoxic effector function of the innate and adaptive immune responses can lead to the development of pulmonary immunopathology, which may lead to death. While T cells produce inflammatory cytokines during infections and allergies, they can also produce the immunomodulatory cytokine IL-10, which is critical for limiting the immunopathology caused by the excessive effector immune responses. However, the composition of IL-10-producing lymphocyte population and their molecular signatures are unclear. Using mouse models that report the production of IL-10 by GFP and expression of T regulatory cell marker Foxp3 by RFP, mouse models of lung inflammation (including allergic asthma, hypersensitivity pneumonitis, and flu), transcriptomic analyses at the population and single cell levels, and transgenic mouse models that are impaired in T cell-derived IL-10 production, we found that, in the disease models used, regulatory T cells in the mouse airway are mainly comprised of CD4+ Foxp3+, CD4+ Foxp3− and CD8+ subsets, and they differ under different disease conditions. Furthermore, within each subset, IL-10-producing T cells exhibit significant molecular heterogeneity. Information gained from this dataset provides insights into the T cell subset heterogeneity and signature markers, and shed light for future strategic design for therapeutic development utilizing the immunomodulatory features of T cells for the treatment of pulmonary immunopathology.

Development of regulatory IL-10-producing ILCs during type 2 inflammation

Innate lymphoid cells (ILCs) are important for mucosal homeostasis and host defense against infectious pathogens. ILC subsets ILC1, 2, and 3, classified similar to T helper cells Th1, Th2, and Th17, are well characterized and known to promote both protective and harmful inflammatory responses. However, the immunosuppressive roles of ILCs are less understood. Regulatory ILCs that produce the immunomodulatory cytokine IL-10 have been recently defined, but the mechanisms regulating their development and function are not fully understood. Similar to other ILCs, regulatory ILCs were thought to be a pre-existing population, however unlike ILC1, 2, and 3 which all differentiate from ILC precursor cells (ILCPs), regulatory ILCs were thought to differentiate exclusively from upstream precursors, common helper-like innate lymphoid precursors (CHILPs) and common lymphoid cell precursors (CLPs). In our animal facilities, we found no evidence of pre-existing tissue resident IL-10+ ILCs in our investigations. In contrast, we find that co-stimulation of IL-33 and a γ-chain cytokine (IL-2, IL-4, or IL-7) robustly induces IL-10+ILCs that exhibit immunosuppressive functions in vitro and in vivo. Further, in addition to CLPs and CHILPs, we find that downstream ILC2Ps can develop into functionally suppressive IL-10+ ILCs following cytokine stimulation. Together, our data support an alternative pathway of IL-10-producing regulatory ILC development and regulation of inflammatory responses.

Interleukin-2-Inducible T-Cell Kinase Deficiency Impairs Early Pulmonary Protection Against Mycobacterium tuberculosis Infection

Interleukin-2 (IL-2) inducible T-cell kinase (ITK) is a non-receptor tyrosine kinase highly expressed in T-cell lineages and regulates multiple aspects of T-cell development and function, mainly through its function downstream of the T-cell receptor. Itk deficiency can lead to CD4 lymphopenia and Epstein-Bar virus (EBV)-associated lymphoproliferation and recurrent pulmonary infections in humans. However, the role of the ITK signaling pathway in pulmonary responses in active tuberculosis due to Mtb infection is not known. We show here that human lungs with active tuberculosis exhibit altered T-cell receptor/ITK signaling and that Itk deficiency impaired early protection against Mtb in mice, accompanied by defective development of IL-17A-producing γδ T cells in the lungs. These findings have important implications of human genetics associated with susceptibility to Mtb due to altered immune responses and molecular signals modulating host immunity that controls Mtb activity. Enhancing ITK signaling pathways may be an alternative strategy to target Mtb infection, especially in cases with highly virulent strains in which IL-17A plays an essential protective role.

Amino acid starvation enhances vaccine efficacy by augmenting neutralizing antibody production

Specific reduction in the intake of proteins or amino acids (AAs) offers enormous health benefits, including increased life span, protection against age-associated disorders, and improved metabolic fitness and immunity. Cells respond to conditions of AA starvation by activating the amino acid starvation response (AAR). Here, we showed that mimicking AAR with halofuginone (HF) enhanced the magnitude and affinity of neutralizing, antigen-specific antibody responses in mice immunized with dengue virus envelope domain III protein (DENVrEDIII), a potent vaccine candidate against DENV. HF enhanced the formation of germinal centers (GCs) and increased the production of the cytokine IL-10 in the secondary lymphoid organs of vaccinated mice. Furthermore, HF promoted the transcription of genes associated with memory B cell formation and maintenance and maturation of GCs in the draining lymph nodes of vaccinated mice. The increased abundance of IL-10 in HF-preconditioned mice correlated with enhanced GC responses and may promote the establishment of long-lived plasma cells that secrete antigen-specific, high-affinity antibodies. Thus, these data suggest that mimetics of AA starvation could provide an alternative strategy to augment the efficacy of vaccines against dengue and other infectious diseases.

Who regulates whom: ZNF341 is an additional player in the STAT3/TH17 song

Deficiency of ZNF341, a transcription factor featuring 12 Cys2His2 zinc fingers that regulates the expression and autoinduction of STAT3 (signal transducer and activator of transcription 3), results in hyper-immunoglobulin E syndrome and defective T helper 17 cell differentiation in humans.

Non-receptor tyrosine kinase signaling in autoimmunity and therapeutic implications

Autoimmune diseases are characterized by impaired immune tolerance towards self-antigens, leading to enhanced immunity to self by dysfunctional B cells and/or T cells. The activation of these cells is controlled by non-receptor tyrosine kinases (NRTKs), which are critical mediators of antigen receptor and cytokine receptor signaling pathways. NRTKs transduce, amplify and sustain activating signals that contribute to autoimmunity, and are counter-regulated by protein tyrosine phosphatases (PTPs). The function of and interaction between NRTKs and PTPs during the development of autoimmunity could be key points of therapeutic interference against autoimmune diseases. In this review, we summarize the current state of knowledge of the functions of NRTKs and PTPs involved in B cell receptor (BCR), T cell receptor (TCR), and cytokine receptor signaling pathways that contribute to autoimmunity, and discuss their targeting for therapeutic approaches against autoimmune diseases.

TCR signal strength and antigen affinity independently modulate CD8+ memory T cell development

CD8+ T cells play a critical role in adaptive immunity by maintaining the ability to differentiate into CD8+ memory T cells, which provide the basis of protective immunity. During an intracellular infection, CD8+ T cells pass through several characteristic phases before becoming mature memory cells. Initial antigen stimulation causes naïve CD8+ T cells to clonally expand and differentiate into short-lived effector cells (SLECs). Subsequently, SLECs undergo a contraction phase to give rise to memory precursor effector cells (MPECs); 5–10% of the MPECs survive the initial contraction phase and further develop into CD8+ memory T cells. We have shown that the non-receptor tyrosine kinase Itk, which regulates TCR signal strength, can significantly suppress CD8+ memory T cell development. We hypothesize that TCR signal strength, regulated by Itk, intersects with antigen affinity to modulate the development of SLECs and MPECs, leading to an increased proportion of memory CD8+ T cells. Utilizing Itk deficient OT-1 TCR transgenic mice, which carry CD8+ T cells specific for the Ovalbumin protein, an adoptive transfer model was established to exam the influence of TCR signal strength and antigen affinity in the development of CD8+ memory T cells. Our findings suggest that TCR signal strength and affinity independently contribute to CD8+ memory T cell development. Our data reveals that reducing both antigen affinity and TCR signal strength leads to enhanced and accelerated antigen-mediated proliferation and development of memory cells, and enhanced secondary expansion of these memory cells. In sum, our data suggests that TCR signal strength and antigen affinity are independent parameters that may be used to tune vaccine development.

ITK signaling differentiates GVT and GVHD after allogeneic bone marrow transplantation by regulating IRF-4, JAK/STAT and Eomesodermin expression

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective therapy for patients with hematologic malignancies. Donor T cells contained within the graft prevent tumor recurrence by exhibiting graft-versus-tumor (GVT) effects but also cause graft-versus-host disease (GVHD); therefore, novel treatment strategies are needed to maintain GVT while suppressing GVHD. We investigated the role of TCR-mediated ITK activation in mediating GVT vs. GVHD effects after allo-HSCT. We discovered that T cells from ITK−/−mice display a CD62Lhi CD122+ CD44hi Innate Lymphoid Cell-Like (ILCL) functional phenotype, and higher Eomes but not T bet expression compared to WT. We showed that T cells from ITK−/−mice reduced IRF-4, JAK1 and JAK2 and STAT3. T cells from ITK−/− mice displayed reduced cytokine production but showed preserved cytotoxicity after allo-HSCT. These cells also showed defective upregulation of the chemokine receptors CX3CR3, CXCR1, and CXCR6, which correlated with their reduced migration into GVHD target organs. The defective migration of ITK deficient T cells into GVHD target organs contributed to separation of GVHD and GVT effects, since ITK deficeint T cells cleared intravenously injected but not subcutaneously injected tumor cells in allo-HSCT mice. Moreover, pharmacological ITK inhibition attenuated GVHD and preserved GVT function by wild type CD8+ T cells. Together, our data suggest that ITK inhibition could be used as therapy after allo-HSCT to reduce GVHD while preserving the beneficial GVT effects by donor T cells