Astrocytic TIMP-1 regulates production of Anastellin, an inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. Astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout (Timp1KO) mice do not efficiently remyelinate following a demyelinating injury. Here, we performed an unbiased proteomic analysis and identified a fibronectin-derived peptide called Anastellin (Ana) that was unique to the Timp1KO astrocyte secretome. Ana was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Ana is known to act upon the sphingosine-1-phosphate receptor 1, and we determined that Ana also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro. Administration of FTY720 to wild-type C57BL/6 mice during MOG35-55-experimental autoimmune encephalomyelitis ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 (Timp1KO) had no effect. Analysis of Timp1 and fibronectin (FN1) transcripts from primary human astrocytes from healthy and multiple sclerosis (MS) donors revealed lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Last, analyses of proteomic databases of MS samples identified Ana peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high disease activity. A role for Ana in MS as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and innate remyelination potential in the MS brain.

Astrocytic TIMP-1 regulates production of Anastellin, a novel inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. We have previously demonstrated that murine astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout ( Timp1 KO ) mice do not efficiently remyelinate following a demyelinating injury. To better understand the basis of this, we performed unbiased proteomic analyses and identified a fibronectin-derived peptide called anastellin that is unique to the murine Timp1 KO astrocyte secretome. Anastellin was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Anastellin is known to act upon the sphingosine-1-phosphate receptor 1 (S1PR1), and we determined that anastellin also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro . Further, administration of FTY720 to wild-type C57BL/6 mice during MOG 35-55 -EAE ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 in astrocytes ( Timp1 cKO ) had no effect. Analysis of human TIMP1 and fibronectin ( FN1 ) transcripts from healthy and multiple sclerosis (MS) patient brain samples revealed an inverse relationship where lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Lastly, we analyzed proteomic databases of MS samples and identified anastellin peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high versus low disease activity. The prospective role for anastellin generation in association with myelin lesions as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and the innate remyelination potential of the the MS brain.

Significance Statement

Astrocytic production of TIMP-1 prevents the protein catabolism of fibronectin. In the absence of TIMP-1, fibronectin is further digested leading to a higher abundance of anastellin peptides that can bind to sphingosine-1-phosphate receptor 1. The binding of anastellin with the sphingosine-1-phosphate receptor 1 impairs the differentiation of oligodendrocytes progenitor cells into myelinating oligodendrocytes in vitro , and negates the astrocyte-mediated therapeutic effects of FTY720 in the EAE model of chronic CNS inflammation. These data indicate that TIMP-1 production by astrocytes is important in coordinating astrocytic functions during inflammation. In the absence of astrocyte produced TIMP-1, elevated expression of anastellin may represent a prospective biomarker for FTY720 therapeutic responsiveness.

Abstract 516: Splice Factor Polypyrimidine Tract-binding Protein 1 (PTBP1) Primes Endothelial Inflammation In Atherogenic Disturbed Flow Conditions

NFκB mediated endothelial activation drives leukocyte recruitment and atherosclerosis, in part through upregulation of adhesion molecules Icam1 and Vcam. The endothelium is primed for cytokine activation of NFκB by exposure to low and disturbed blood flow (LDF). While priming leads to an exaggerated expression of Icam1 and Vcam following cytokine stimulation, the molecular underpinnings are not understood. In a model of LDF, platelets were required for the increased expression of several RNA-binding splice factors, including Polypyrimidine tract binding protein (Ptbp1). This was coordinated with changes in RNA splicing in the NFκB pathway in primed cells, leading us to examine splice factors as mediators of priming. Using Icam1 and Vcam induction by TNFα stimulation as a readout, we performed a CRISPR-Cas9 screen of these factors and identified a requirement for Ptbp1 in priming. Deletion of Ptbp1 had no obvious effect on cell proliferation or viability, but reversed LDF splicing patterns and inhibited NFκB nuclear translocation and transcriptional activation of nearly all downstream targets, including Icam1 and Vcam. In human coronary arteries, elevated PTBP1 correlates with expression of TNF pathway genes and plaque. In vivo , endothelial specific deletion of Ptbp1 reduced Icam1 expression and myeloid cell infiltration at regions of LDF in atherosclerotic mice and limited atherosclerosis. Together, our data show that Ptbp1, which is induced in a subset of the endothelium by innate immune cell recruitment at regions of LDF, is required for priming of the endothelium for subsequent NFκB activation, myeloid cell recruitment and atherosclerosis.

Optimal CD8+ T cell effector function requires costimulation-induced RNA-binding proteins that reprogram the transcript isoform landscape

Boosting T cell activation through costimulation directs defense against cancer and viral infections. Despite many studies targeting costimulation in clinical trials, the increased potency and reprogramming of T cells endowed by costimulation is poorly understood. Canonical dogma states that transcription mediates T cell activation. Here, we show that the spliceosome, controlling post-transcriptional alternative splicing and alternative polyadenylation, is the most significantly enriched pathway in T cells after CD134/CD137 costimulation. Costimulation of CD8+ T cells significantly increased expression of 29 RNA-binding proteins (RBPs) while RNA-seq uncovered over 1000 differential alternative splicing and polyadenylation events. Using in vivo mouse and in vitro human CRISPR models, we demonstrate that RBP Tardbp, among multiple other RBPs, is required for effector cytokine production, CD8+ T cell clonal expansion, and isoform regulation after costimulation. The prospect of immune response optimization through reprogramming of mRNA isoform production offered herein opens new avenues for experimentally and therapeutically tuning the activities of T cells.

Supported by NIH grants AI136955 and R21AI139891.

A high OXPHOS CD8 T cell subset is predictive of immunotherapy resistance in melanoma patients

Immune checkpoint inhibitor (ICI) therapy continues to revolutionize melanoma treatment, but only a subset of patients respond. Major efforts are underway to develop minimally invasive predictive assays of ICI response. Using single-cell transcriptomics, we discovered a unique CD8 T cell blood/tumor-shared subpopulation in melanoma patients with high levels of oxidative phosphorylation (OXPHOS), the ectonucleotidases CD38 and CD39, and both exhaustion and cytotoxicity markers. We called this population with high levels of OXPHOS “CD8⁺ T_OXPHOS cells.” We validated that higher levels of OXPHOS in tumor- and peripheral blood–derived CD8⁺ T_OXPHOS cells correlated with ICI resistance in melanoma patients. We then developed an ICI therapy response predictive model using a transcriptomic profile of CD8⁺ T_OXPHOS cells. This model is capable of discerning responders from nonresponders using either tumor or peripheral blood CD8 T cells with high accuracy in multiple validation cohorts. In sum, CD8⁺ T_OXPHOS cells represent a critical immune population to assess ICI response with the potential to be a new target to improve outcomes in melanoma patients.

Intracellular immune sensing promotes inflammation via gasdermin D-driven release of a lectin alarmin

Inflammatory caspase sensing of cytosolic lipopolysaccharide (LPS) triggers pyroptosis and the concurrent release of damage-associated molecular patterns (DAMPs). Collectively, DAMPs are key determinants that shape the aftermath of inflammatory cell death. However, the identity and function of the individual DAMPs released are poorly defined. Our proteomics study revealed that cytosolic LPS sensing triggered the release of galectin-1, a β-galactoside-binding lectin. Galectin-1 release is a common feature of inflammatory cell death, including necroptosis. In vivo studies using galectin-1-deficient mice, recombinant galectin-1 and galectin-1-neutralizing antibody showed that galectin-1 promotes inflammation and plays a detrimental role in LPS-induced lethality. Mechanistically, galectin-1 inhibition of CD45 (Ptprc) underlies its unfavorable role in endotoxin shock. Finally, we found increased galectin-1 in sera from human patients with sepsis. Overall, we uncovered galectin-1 as a bona fide DAMP released as a consequence of cytosolic LPS sensing, identifying a new outcome of inflammatory cell death.

Costimulation Induces CD4 T Cell Antitumor Immunity via an Innate-like Mechanism

Chronic exposure to tumor-associated antigens inactivates cognate T cells, restricting the repertoire of tumor-specific effector T cells. This problem was studied here by transferring TCR transgenic CD4 T cells into recipient mice that constitutively express a cognate self-antigen linked to MHC II on CD11c-bearing cells. Immunotherapeutic agonists to CD134 plus CD137, "dual costimulation," induces specific CD4 T cell expansion and expression of the receptor for the Th2-associated IL-1 family cytokine IL-33. Rather than producing IL-4, however, they express the tumoricidal Th1 cytokine IFNγ when stimulated with IL-33 or IL-36 (a related IL-1 family member) plus IL-12 or IL-2. IL-36, which is induced within B16-F10 melanomas by dual costimulation, reduces tumor growth when injected intratumorally as a monotherapy and boosts the efficacy of tumor-nonspecific dual costimulated CD4 T cells. Dual costimulation thus enables chronic antigen-exposed CD4 T cells, regardless of tumor specificity, to elaborate tumoricidal function in response to tumor-associated cytokines.

Cytosolic LPS sensing triggers the release of a lectin DAMP that promotes inflammation

Activation of inflammatory caspases, such as caspase-11 and caspase-4, by lipopolysaccharide (LPS) from Gram-negative bacteria, is a key mechanism of innate immune defense against infections. This cytosolic LPS sensing pathway results in activation of a pore-forming protein, gasdermin D, which mediates an inflammatory form of cell death called pyroptosis. In addition, caspase-11-mediated cytosolic LPS sensing leads to the activation of caspase-1 and the maturation of IL-1b and IL-18. Importantly, cytosolic LPS-induced pyroptosis is associated with the release of intracellular proteins that act as alarmins or damage-associated molecular patterns (DAMPs) to modulate the inflammatory response and play an important role during infectious diseases and sepsis. However, the identity and function of DAMPs released downstream of caspase-11 activation are poorly characterized. Using a proteomic approach involving ProteomeLab’s PF2D fractionation system followed by mass spectrometry, we have discovered that galectin-1, a b-galactoside-binding lectin, is released as a consequence of cytosolic LPS sensing. By utilizing various mutant cell lines and primary cells we show that galectin-1 secretion is dependent on caspase-11 and gasdermin D, but not NLRP3 or caspase-1. Importantly, in vivo studies using galectin-1-deficient mice showed that galectin-1 acts as a DAMP to promote systemic inflammation and plays a detrimental role during septic shock. Additionally, human septic patients were found to have increased levels of galectin-1 in their serum. Taken together, we have characterized the secretion and function of a novel lectin DAMP released upon lytic cell death and provide new insights into outcomes of inflammasome activation.

Alarmin(g) outcomes of intracellular LPS sensing

Intracellular sensing of LPS by inflammatory caspases such as caspase-11 has emerged as a key mechanism of innate immune activation during Gram-negative bacterial infections. Cytosolic recognition of LPS by caspase-11 leads to inflammatory cell death or pyroptosis and maturation of IL-1 cytokines. Remarkably, the activation of inflammatory caspases also results in the extracellular release of alarmins and damage associated molecular patterns (DAMPs). These alarmins and DAMPs lack leader signals for classical secretion and are therefore released via a caspase-11 mediated unconventional secretory mechanism. Alarmins and DAMPs—structurally diverse molecules participating in various cellular processes under steady state conditions—are released rapidly upon infections and tissue damage. In the extracellular milieu, these proteins elicit inflammatory reactions by regulating pattern recognition receptor signaling and recruiting innate cells. Despite their potential roles in sepsis, the identity of alarmins and DAMPs released as a result of cytosolic LPS sensing and their contribution to sepsis are poorly understood. Addressing this knowledge gap, we employed an unbiased proteomic approach involving two-dimensional liquid phase fractionation system and mass spectrometry and identified alarmins released in response to caspase-11 activation by cytosolic LPS. In this presentation, the molecular basis of secretion of a candidate alarmin in vitro and in vivo as well as its function in murine models of host defense will be discussed.

Noncanonical Inflammasome-Induced release of Alarmins during Sepsis

Sepsis is a life-threatening disease caused by the immune system’s response to infection that results in excessive inflammation, organ damage and often death. In fact, sepsis is the leading cause of death in intensive care units and is responsible for more than 250,000 deaths every year in the USA. Activation of inflammatory caspases, such as caspase-11 by lipopolysaccharide (LPS) from Gram-negative bacteria, is a key mechanism of innate immune defense against infection. Intracellular sensing of LPS by caspase-11 results in pyroptosis, maturation of caspase-1, IL-1β and IL-18 and unconventional secretion of intracellular proteins that lack a leader sequence for conventional secretion via endoplasmic reticulum-Golgi route. These proteins can act as alarmins or damage associated molecular patterns (DAMPs) to regulate the inflammatory response and therefore play an important role during infectious diseases. However, caspase-11-dependent release of alarmins and DAMPs following noncanonical inflammasome activation is poorly characterized. Using a proteomics approach involving ProteomeLab’s PF2D fractionation system followed by mass spectrometry, we have profiled several new alarmins released in a caspase-11 dependent manner following Gram-negative bacterial infection. By employing various mutant mice and cells, we have defined the molecular and cellular mechanisms underlying the release of a candidate alarmin as a consequence of noncanonical inflammasome activation in vitro and in vivo. Importantly, our in vivo studies demonstrate a critical role for this alarmin in LPS shock. Overall, these findings provide new insights into potential biomarkers and therapeutic targets for blocking the lethal inflammation in sepsis.

Single cell transcriptomics based-MacSpectrum reveals novel macrophage activation signatures in diseases

Adipose tissue macrophages (ATM) are crucial for maintaining adipose tissue homeostasis and mediating obesity-induced metabolic abnormalities, including prediabetic conditions and type 2 diabetes mellitus. Despite their key functions in regulating adipose tissue metabolic and immunologic homeostasis under normal and obese conditions, a high-resolution transcriptome annotation system that can capture ATM multifaceted activation profiles has not yet been developed. This is primarily attributed to the complexity of their differentiation/activation process in adipose tissue and their diverse activation profiles in response to microenvironmental cues. Although the concept of multifaceted macrophage action is well-accepted, no current model precisely depicts their dynamically regulated in vivo features. To address this knowledge gap, we generated single-cell transcriptome data from primary bone marrow-derived macrophages under polarizing and non-polarizing conditions to develop new high-resolution algorithms. The outcome was creation of a two-index platform, MacSpectrum (https://macspectrum.uconn.edu), that enables comprehensive high-resolution mapping of macrophage activation states from diverse mixed cell populations. MacSpectrum captured dynamic transitions of macrophage subpopulations under both in vitro and in vivo conditions. Importantly, MacSpectrum revealed unique "signature" gene sets in ATMs and circulating monocytes that displayed significant correlation with BMI and homeostasis model assessment of insulin resistance (HOMA-IR) in obese human patients. Thus, MacSpectrum provides unprecedented resolution to decode macrophage heterogeneity and will open new areas of clinical translation.

Gasdermin D Restrains Type I Interferon Response to Cytosolic DNA by Disrupting Ionic Homeostasis

Inflammasome-activated caspase-1 cleaves gasdermin D to unmask its pore-forming activity, the predominant consequence of which is pyroptosis. Here, we report an additional biological role for gasdermin D in limiting cytosolic DNA surveillance. Cytosolic DNA is sensed by Aim2 and cyclic GMP-AMP synthase (cGAS) leading to inflammasome and type I interferon responses, respectively. We found that gasdermin D activated by the Aim2 inflammasome suppressed cGAS-driven type I interferon response to cytosolic DNA and Francisella novicida in macrophages. Similarly, interferon-β (IFN-β) response to F. novicida infection was elevated in gasdermin D-deficient mice. Gasdermin D-mediated negative regulation of IFN-β occurred in a pyroptosis-, interleukin-1 (IL-1)-, and IL-18-independent manner. Mechanistically, gasdermin D depleted intracellular potassium (K⁺) via membrane pores, and this K⁺ efflux was necessary and sufficient to inhibit cGAS-dependent IFN-β response. Thus, our findings have uncovered an additional interferon regulatory module involving gasdermin D and K⁺ efflux.

SMAD4-deficient Dendritic Cells in the Murine Lung shows an Activated Phenotype

SMAD4 is a signaling intermediate that acts downstream of the TGFb receptor. This signaling pathway is known to regulate expression of the Itgae gene (CD103) in activated CD8 T cells. Whether SMAD4 plays a role in induction or maintenance of CD103+ dendritic cells (DCs) has not been investigated. To address this question, we crossed SMAD4 floxed mice with Cre under the control of the CD11c promoter. DCs in the lung, spleen and bone marrow of naïve CD11c-SMAD4 mice were analyzed by multi-parameter flow cytometry. The lungs of Smad4-deficient mice contained smaller numbers of CD11c+ cells than control animals, and the remaining cells expressed costimulatory molecules and CD11b at high levels. Lung suspensions were metal barcoded for time of flight cytometry (cyTOF) and viSNE maps were contracted using 25 parameters. Under these homeostatic conditions, Smad4-abalation caused a dramatic decrease in CD11c+ DCs with activation of pSTAT5, when compared to DCs from littermate controls. Activation of pSTAT5 in KO was specific to CD11c+ DCs as no difference was seen in other cell types including T cells. Our data indicate that the lungs of SMAD4-CD11c KO mice were depleted of migratory DCs, which migrated to the draining lymph nodes after spontaneous maturation. We currently are exploring whether DC-depletion undermines cell mediated immunity to respiratory virus infection.

T Cell-Directed IL-17 production by Lung Granular γδ T cells is Coordinated by a Novel IL-2 and IL-1β Circuit

Immune-mediated lung injury is considered the result of an exacerbated innate immune response, although a role for adaptive lymphocytes is emerging. αβ T cells specific for S. aureus enterotoxin A orchestrates a typical innate-like Tγδ17 response during lung injury. However, the mechanism by which a specific T cell response drives an innate immune response in the lung is unclear. Here, we show a role for IL-2 triggering IL-17 production by lung granular γδ T cells as IL-17 synthesis was reduced by IL-2 blocking mAbs in vitro and in vivo. Granular γδ T cells in the lung constitute a rare population, hence Mass Cytometry (CyTOF) was utilized to characterize this population. CyTOF analysis revealed that lung γδ T cells responded directly to IL-2 as evident from STAT5 phosphorylation and RoRγt expression. IL-2 receptor blocking mAbs and JAK inhibition impaired STAT5 phosphorylation and IL-17 release. Moreover, inhalation of S. aureus enterotoxin A induced IL-2 secretion and caspase-1-dependent IL-1β activation to drive IL-17 production. This T cell-mediated inflammasome dependent IL-17 response is maximum when lung Tγδ17 cells were sequentially stimulated first with IL-2 then IL-1β. Further investigation is still needed to identify the cellular source of IL-1β. Interestingly, when IL-2 is given therapeutically to cancer patients it carries a known risk of lung injury that is largely indistinguishable from that seen in sepsis. Hence, this novel mechanism reveals therapeutic targets treating both acute lung injury and high dose IL-2 toxicity in cancer.

Altered flow triggers activated T cell accumulation and inflammation in early atherosclerosis

Atherosclerosis is linked to systemic inflammation. Yet, the inflamed plaques predicating cardiovascular morbidity and mortality preferentially develop in areas of low and disturbed flow (LDF). Partial carotid artery ligation (PCAL) of the left carotid exposes vascular endothelium to LDF without disturbing flow contralaterally and when combined with high fat diet, LDF regions develop plaques within 2 wks. We show that just 48 hr after PCAL, LDF triggers significant upregulation of IL-36, a new member of the proinflammatory IL-1 family, and Cathepsin S, its enzymatic activator. The IL-1 family and IFNγ are intimately tied to atherogenesis and our past work establishes IL-36 as a robust stimulator of IFNγ from effector T cells. Thus, we hypothesize that LDF triggers an IL-36-IFNγ loop, promoting early disease independent of plaque-specific antigen. To test this, we assessed the homing of adoptively transferred CD8 TCR transgenic T cells that were antigen-primed and CD137-costimulated within recipient mice. Comparison of physiologic LDF regions (aortic arch) with experimentally induced LDF (PCAL) reveals that effector CD8 T cells substantially and preferentially accumulate within LDF areas, even without TCR-specific stimuli in the vessel wall. Notably, cells isolated from these regions produce IFNγ in response to IL-36. Mass cytometry (CYTOF) and single cell RNA-seq analyses are underway to build mechanistic understandings of how LDF triggers immune cell recruitment and signaling cascades. Overall, our studies propose a novel role for IL-36 within the vascular system and provide insight into the early pathogenesis of atherosclerosis, especially in the context of autoimmunity and antigen-independent T cell activation.

A novel, dual-specific antibody conjugate targeting CD134 and CD137 costimulates T cells and elicits antitumor immunity

Checkpoint inhibiting antibodies targeting CTLA-4 and PD-1, along with costimulatory agonists, exhibit impressive anticancer efficacy and evidence of durable tumor regression in patients. Despite this success however, many patients fail to respond, likely due to multiple immunosuppressive tactics employed by cancer cells. Combination therapies designed to counteract these immunosuppressive features show promise, but strategies relying on multiple agents suffer from logistical and regulatory challenges, as well as increased risks of adverse events. We developed a novel immunotherapeutic agent by fusing two TNFR family costimulatory agonists (anti-CD134/CD137) into a single biologic encompassing the therapeutic benefits of both agents while avoiding many of the drawbacks associated with traditional combination therapies. Our preliminary data show that this dual-specific, tetravalent antibody conjugate induces potent and differential in vitro potentiation of cytokine secretion from CD3-stimulated splenocytes, compared to that observed with single agonists alone or in combination. We hypothesize that this a consequence of unique signaling and hybrid costimulatory events. Secondly, this conjugate, referred to as OrthomAb, potently delayed tumor growth and reduced tumor burden in the aggressive B16 melanoma model. In vivo antitumor efficacy exceeded that of either individual unconjugated agonist. Importantly, this work establishes a framework for fusion of immunomodulatory biologics into a single drug with the benefit of combination immunotherapy to treat cancer.

Costimulation Endows Immunotherapeutic CD8 T Cells with IL-36 Responsiveness during Aerobic Glycolysis

CD134- and CD137-primed CD8 T cells mount powerful effector responses upon recall, but even without recall these dual-costimulated T cells respond to signal 3 cytokines such as IL-12. We searched for alternative signal 3 receptor pathways and found the IL-1 family member IL-36R. Although IL-36 alone did not stimulate effector CD8 T cells, in combination with IL-12, or more surprisingly IL-2, it induced striking and rapid TCR-independent IFN-γ synthesis. To understand how signal 3 responses functioned in dual-costimulated T cells we showed that IL-2 induced IL-36R gene expression in a JAK/STAT-dependent manner. These data help delineate a sequential stimulation process where IL-2 conditioning must precede IL-36 for IFN-γ synthesis. Importantly, this responsive state was transient and functioned only in effector T cells capable of aerobic glycolysis. Specifically, as the effector T cells metabolized glucose and consumed O2, they also retained potential to respond through IL-36R. This suggests that T cells use innate receptor pathways such as the IL-36R/axis when programmed for aerobic glycolysis. To explore a function for IL-36R in vivo, we showed that dual costimulation therapy reduced B16 melanoma tumor growth while increasing IL-36R gene expression. In summary, cytokine therapy to eliminate tumors may target effector T cells, even outside of TCR specificity, as long as the effectors are in the correct metabolic state.

Responses to LPS boost effector CD8 T-cell accumulation outside of signals 1 and 2

Immunization with adjuvant plus antigen induces durable T-cell immunity and is a mainstay of vaccines. Here, the consequence of separating antigen stimulation of T cells from the adjuvant response was studied in a re-transfer model. Effector CD8 T cells in recipient mice were exposed to lipopolysaccharide (LPS), the Toll-like receptor 4 (TLR4) ligand, which significantly increased persistence. While accumulation in lymphoid and non-lymphoid organs was evident, this result depended upon the timing of LPS administration and the presence of the TLR4 adaptor TRIF in the recipient mice. Interestingly, there was very little impact of the LPS response on subset differentiation, which rather appeared to be programmed by antigen and costimulation. To discern factors that limit accumulation, interleukin 10 (IL-10) was targeted since it is a product of TLR4 triggering and mitigates inflammation. Blockade of IL-10 increased accumulation even though the effector CD8 T cells were well past the priming phase, but upon recall interferon-γ secretion was not affected as would be expected when IL-10 is present during priming. Thus, the adjuvant-altered microenvironment is effective not only in the presence of antigen but also during a window of effector CD8 T-cell stasis, suggesting that pathogen-associated molecular pattern molecules released during co-infection, or by vaccines, could alter the survival fate of specific effector T cells.Cellular & Molecular Immunology advance online publication, 20 July 2015; doi:10.1038/cmi.2015.69.

Trace levels of staphylococcal enterotoxin bioactivity are concealed in a mucosal niche during pulmonary inflammation (MUC1P.917)

Pathogen and cellular by-products released during infection or trauma are critical for initiating mucosal inflammation. This was studied in mice undergoing pulmonary inflammation after Staphylococcal enterotoxin A (SEA) inhalation. A potent pro-inflammatory factor was detected using a sensitive bioassay suggesting the presence of an alarmin, a danger-associated molecular pattern (DAMP), and/or a cytokine. Highly purified bronchoalveolar lavage fluid (BALF) fractions obtained by sequential chromatography were screened for bioactivity and subjected to mass spectrometry. SEA was the only identified protein with known inflammatory potential, and unexpectedly, it co-purified with immunosuppressive proteins. Among them was lactoferrin, which inhibited SEA and anti-CD3/-CD28 stimulation by promoting T cell death and reducing TNF synthesis. Higher doses of lactoferrin were required to inhibit effector compared to resting T cells. This inhibition relied on the continual presence of lactoferrin rather than a programming event. The data show that bioactive SEA is constituted in a mucosal niche within BALF even after the initiation of inflammation. These results may have clinical value in human diagnostic settings since traces levels of SEA can be detected using a sensitive bioassay, and may help pinpoint potential mediators of lung inflammation when molecular approaches fail. Submitted to American Journal of Respiratory Cell and Molecular Biology.

Elucidating a role for a hematopoietic-tropic microRNA in T cell (IRM12P.650)

To gain new insight into how miRNA impact T cell responses, mice were immunized with costimulation and adjuvant to generate potent T effector responses. We generated a cDNA library from lymphoid tissue. Using sequencing of size-fractionated cDNA we cloned 6 potential new miRNAs with characteristic stem loop folding. One of these candidates, termed miR-R89 but not yet registered in miRBase, was unique since its expression was hematopoietic specific and regulated during immune activation. The targets and function of miR-R89 are currently unknown, but our preliminary data show it is expressed in a T cell clone known to cause experimental autoimmune encephalitis. Transfection with a locked nucleic acid (LNA) mimic of miR-R89 in EL4 thymoma cells increased IL-2 secretion after PMA-ionomycin (PI) stimulation compared to transfection with control LNA. RNAseq analysis of the transfected cells revealed that mRNA expression of two transcription factors involved in metabolism, Tfe3 and Tef, was reduced by miR-R89 mimic. Interestingly, 3’UTR mRNA of Tfe3 and Tef have several theoretical binding sites for miR-R89. Treatment of PI-stimulated EL4 cells with UK5099, an inhibitor of mitochondrial pyruvate transport and metabolism, mediated a similar increase of IL-2 secretion than observed after transfection with miR-R89. These data suggest the putative miRNA miR-R89 could target Tfe3 and Tef mRNA and function as a metabolic regulator of T cell activation.

Mechanisms underlying T cell guided innate immunity after inhalation of Staphylococcus enterotoxin A (SEA) (173.1)

Inhalation of Staphylococcus aureus enterotoxin A (SEA) in mice induces strong pulmonary inflammation marked by vascular permeability and alveolitis, thereby modeling aspects of lung injury in humans. After SEA inhalation CD8+Vβ3+ T cells robustly expand but the early events of this response in the lung are unclear. Our new data show that Vβ3+ T cells are activated quickly after SEA inhalation since CD69 and the high affinity IL-2 receptor α-chain (CD25) were upregulated by 3 hours. This coincided with several changes in the innate immune system including recruitment of neutrophils, monocytes and NK cells into the lung, and imprinting an activation phenotype on macrophages. Importantly, in the absence of T cells all of these effects were abrogated. As a way to understand how T cells condition innate immunity, we analyzed cytokine production and found an unexpected role for TCRαβ T cells promoting IL-17 secretion by TCRγδ T cells. We demonstrated that TCRγδ cells did not produce IL-17 when tested in TCRβ-/- mice. Currently, we are defining how TCRγδ cells are induced to synthesize IL-17 by the TCRαβ cells. In sum, TCRαβ T cells mediate pro-inflammatory responses, not only as a direct source of cytokines, but also by guiding the recruitment and activation of innate cells. Thus, our data show role reversal between the adaptive immune and innate immune system.

Selective PGE(2) suppression inhibits colon carcinogenesis and modifies local mucosal immunity

Prostaglandin E(2) (PGE(2)) is a bioactive lipid that mediates a wide range of physiologic effects and plays a central role in inflammation and cancer. PGE(2) is generated from arachidonic acid by the sequential actions of the COX and terminal synthases (PGES). Increased levels of COX-2, with a concomitant elevation of PGE(2), are often found in colorectal cancers (CRC), providing the rationale for the use of COX-2 inhibitors for chemoprevention. Despite their proven efficacy in cancer prevention, however, COX-2 inhibitors exhibit dose-dependent toxicities that are mediated in part by their nonspecific reduction of essential prostanoids, thus limiting their chemopreventive benefit. To achieve enhanced specificity, recent efforts have been directed toward targeting the inducible terminal synthase in the production of PGE(2), microsomal PGES (mPGES-1). In the present study, we show that genetic deletion of mPGES-1 affords significant protection against carcinogen-induced colon cancer. mPGES-1 gene deletion results in an about 80% decrease in tumor multiplicity and up to a 90% reduction in tumor load in the distal colon of azoxymethane (AOM)-treated mice. Associated with the striking cancer suppression, we have identified a critical role for PGE(2) in the control of immunoregulatory cell expansion (FoxP3-positive regulatory T cells) within the colon-draining mesenteric lymph nodes, providing a potential mechanism by which suppression of PGE(2) may protect against CRC. These results provide new insights into how PGE(2) controls antitumor immunity.

Abstract A32: Proteomic signatures of deoxycholic acid and ursodeoxycholic acid treated human colon cancer cells

A32

Dietary factors play an important role in the pathogenesis of colorectal cancer (CRC), due in part to the influence of the bile acids. While the secondary bile acid, deoxycholic acid (DCA), has been associated with tumor promotion, one tertiary bile acid in particular, ursodeoxycholic acid (UDCA), has been demonstrated to exert chemopreventive properties in the colon. Although its efficacy against high-grade adenomas has already been demonstrated in phase III clinical trials, mechanisms by which UDCA suppresses colon tumorigenesis remain unclear. In order to gain further insight into the tumor modifying properties of the bile acids, we compared the effects of DCA and UDCA on human colon tumor cells (CaCo-2) using proteomic analyses. In the following study, CaCo-2 cells grown at 70% confluence were treated with either 10 µM deoxycholic acid (DCA) or 1 mM ursodeoxycholic acid (UDCA) for 72 hours. For the proteomic analysis, protein was first fractionated by PF2D isochromatofocusing on a Beckman Coulter ProteomeLab PF2D platform. Fractions corresponding to a linear gradient between pH 8.0 and 4.0 were collected and processed through an automated autoloader for further separation by HPRP-PF2D reverse phase chromatography. Two dimensional protein expression maps displaying isoelectric point (pI) versus hydrophobicity were generated by the ProteoView/DeltaVue software package. Pairwise analysis of these complex protein chromatograms demonstrated common peak profiles (signatures) as well as unique peaks (fingerprints) characteristic of UDCA or DCA treatment. One of these protein peaks that exhibited a differential expression pattern between the two drug treatments was identified by MALDI and tandem mass spectrometry sequencing as heat-shock protein 60 (Hsp60). Furthermore, this protein was found to be less oxidized upon treatment with UDCA, suggesting the attenuation of oxidative stress present in cancer cells. Further analyses on the role of Hsp60 as well as resultant diminished oxidative stress will enable the discovery of potential mechanisms by which DCA and UDCA control cellular pathways.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):A32.

Roles of heat-shock proteins in antigen presentation and cross-presentation

Heat-shock proteins chaperone antigenic peptides that are generated within cells. Such chaperoning is a part of the endogenous pathway of antigen presentation by MHC class I molecules. In addition, peptides that are chaperoned by heat-shock proteins, or are released by cell stress or death, are taken up by antigen-presenting cells and re-presented by their MHC molecules.

Differential adhesion of rat colon carcinoma cells to fibronectin in relation to their tumorigenicity

We examined the fibronectin-adhesive properties of clones from a rat colonic cell line exhibiting distinct tumorigenicity in a syngeneic host. These cells were originally selected on the basis of differential adhesion to plastic surfaces. The TR cell line, when injected subcutaneously, forms a tumour which grows progressively and gives off metastases, whereas the TS cell line forms a small tumour which regresses within a few weeks. The regression is largely mediated by immunological factors and involves a fibroblastic reaction. REGb, a clone from the TS subline, adhered better to fibronectin or RGDS tetrapeptide than did PROb, a clone from the TR subline. However, there was little binding to the RGD tripeptide with either clone. The degree of adhesion was dependent on time and substrate concentration. After 6 h of incubation, 38% and 55% respectively of PROb and REGb cells bound to plates coated with 10 micrograms/ml fibronectin. Adhesion of both clones to fibronectin was inhibited to various degrees when cells were preincubated with RGDS, GRGDS or GRADSPK peptides, whereas other synthetic peptides such as RGD, GRGD or GRGFSPK were ineffective. Binding experiments using 125I-labelled fibronectin showed 39,000 fibronectin receptor sites on REGb cells but only 17,000 on PROb cells. Flow cytometry analysis using both anti-alpha 5 and anti-beta 1 integrins showed more fibronectin receptor sites on REGb than on PROb cells. Both approaches were in accordance with the higher adhesiveness of the REGb clone to fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and characterization of a rat protein (p 105) auto-antigenic in rats bearing a progressive syngeneic colon carcinoma

Sera from BDIX rats inoculated with 2 tumor clones derived from a single syngeneic colon carcinoma were assayed by Western blotting for the presence of antibodies against the grafted tumor. The PROb clone is progressive and produces metastases. We observed that rats bearing this tumor developed antibodies against an unglycosylated water-soluble protein of 105 kDa. The magnitude of this humoral response, as assessed by the intensity of the signal on immunoblots, was inversely correlated with survival of the rats. Furthermore, rats inoculated with the REGb clone, which is immunologically rejected, never developed detectable antibodies against the tumor. Antisera from rats injected with PROb tumor detected p105 antigen in cellular extracts from the REGb clone and from a series of rat and human cell lines. This protein was also detected in variable amounts in some normal adult and fetal tissues. Treatment of PROb or REGb cells by either interferon-gamma or heat shock did not significantly alter the expression of the p105 auto-antigen.