CRISPR screen in regulatory T cells reveals modulators of Foxp3.

Regulatory T (Treg) cells are required to control immune responses and maintain homeostasis, but are a significant barrier to antitumour immunity1. Conversely, Treg instability, characterized by loss of the master transcription factor Foxp3 and acquisition of proinflammatory properties2, can promote autoimmunity and/or facilitate more effective tumour immunity3,4. A comprehensive understanding of the pathways that regulate Foxp3 could lead to more effective Treg therapies for autoimmune disease and cancer. The availability of new functional genetic tools has enabled the possibility of systematic dissection of the gene regulatory programs that modulate Foxp3 expression. Here we developed a CRISPR-based pooled screening platform for phenotypes in primary mouse Treg cells and applied this technology to perform a targeted loss-of-function screen of around 500 nuclear factors to identify gene regulatory programs that promote or disrupt Foxp3 expression. We identified several modulators of Foxp3 expression, including ubiquitin-specific peptidase 22 (Usp22) and ring finger protein 20 (Rnf20). Usp22, a member of the deubiquitination module of the SAGA chromatin-modifying complex, was revealed to be a positive regulator that stabilized Foxp3 expression; whereas the screen suggested that Rnf20, an E3 ubiquitin ligase, can serve as a negative regulator of Foxp3. Treg-specific ablation of Usp22 in mice reduced Foxp3 protein levels and caused defects in their suppressive function that led to spontaneous autoimmunity but protected against tumour growth in multiple cancer models. Foxp3 destabilization in Usp22-deficient Treg cells could be rescued by ablation of Rnf20, revealing a reciprocal ubiquitin switch in Treg cells. These results reveal previously unknown modulators of Foxp3 and demonstrate a screening method that can be broadly applied to discover new targets for Treg immunotherapies for cancer and autoimmune disease.

Intravenous Immunomodulatory Nanoparticle Treatment for Traumatic Brain Injury.

OBJECTIVE: There are currently no definitive disease-modifying therapies for traumatic brain injury (TBI). In this study, we present a strong therapeutic candidate for TBI, immunomodulatory nanoparticles (IMPs), which ablate a specific subset of hematogenous monocytes (hMos). We hypothesized that prevention of infiltration of these cells into brain acutely after TBI would attenuate secondary damage and preserve anatomic and neurologic function. METHODS: IMPs, composed of US Food and Drug Administration-approved 500nm carboxylated-poly(lactic-co-glycolic) acid, were infused intravenously into wild-type C57BL/6 mice following 2 different models of experimental TBI, controlled cortical impact (CCI), and closed head injury (CHI). RESULTS: IMP administration resulted in remarkable preservation of both tissue and neurological function in both CCI and CHI TBI models in mice. After acute treatment, there was a reduction in the number of immune cells infiltrating into the brain, mitigation of the inflammatory status of the infiltrating cells, improved electrophysiologic visual function, improved long-term motor behavior, reduced edema formation as assessed by magnetic resonance imaging, and reduced lesion volumes on anatomic examination. INTERPRETATION: Our findings suggest that IMPs are a clinically translatable acute intervention for TBI with a well-defined mechanism of action and beneficial anatomic and physiologic preservation and recovery. Ann Neurol 2020;87:442-455.

Monocytes prime autoreactive T cells after myocardial infarction.

In humans, loss of central tolerance for the cardiac self-antigen α-myosin heavy chain (α-MHC) leads to circulation of cardiac autoreactive T cells and renders the heart susceptible to autoimmune attack after acute myocardial infarction (MI). MI triggers profound tissue damage, releasing danger signals and self-antigen by necrotic cardiomyocytes, which lead to recruitment of inflammatory monocytes. We hypothesized that excessive inflammation by monocytes contributes to the initiation of adaptive immune responses to cardiac self-antigen. Using an experimental model of MI in α-MHC-mCherry reporter mice, which specifically express mCherry in cardiomyocytes, we detected α-MHC antigen in myeloid cells in the heart-draining mediastinal lymph node (MLN) 7 days after MI. To test whether monocytes were required for cardiac self-antigen trafficking to the MLN, we blocked monocyte recruitment with a C-C motif chemokine receptor type 2 (CCR2) antagonist or immune modifying nanoparticles (IMP). Blockade of monocyte recruitment reduced α-MHC antigen detection in the MLN after MI. Intramyocardial injection of the model antigen ovalbumin into OT-II transgenic mice demonstrated the requirement for monocytes in antigen trafficking and T-cell activation in the MLN. Finally, in nonobese diabetic mice, which are prone to postinfarction autoimmunity, blockade of monocyte recruitment reduced α-MHC-specific responses leading to improved tissue repair and ventricular function 28 days after MI. Taken together, these data support a role for monocytes in the onset of pathological cardiac autoimmunity following MI and suggest that therapeutic targeting of monocytes may mitigate postinfarction autoimmunity in humans.NEW & NOTEWORTHY Our study newly identifies a role for inflammatory monocytes in priming an autoimmune T-cell response after myocardial infarction. Select inhibition of monocyte recruitment to the infarct prevents trafficking of cardiac self-antigen and activation of cardiac myosin reactive T cells in the heart-draining lymph node. Therapeutic targeting of inflammatory monocytes may limit autoimmune responses to improve cardiac remodeling and preserve left ventricular function after myocardial infarction.

Activated leukocyte cell adhesion molecule promotes leukocyte trafficking into the central nervous system.

Adhesion molecules of the immunoglobulin superfamily are crucial effectors of leukocyte trafficking into the central nervous system. Using a lipid raft-based proteomic approach, we identified ALCAM as an adhesion molecule involved in leukocyte migration across the blood-brain barrier (BBB). ALCAM expressed on BBB endothelium localized together with CD6 on leukocytes and with BBB endothelium transmigratory cups. ALCAM expression on BBB cells was upregulated in active multiple sclerosis and experimental autoimmune encephalomyelitis lesions. Moreover, ALCAM blockade restricted the transmigration of CD4+ lymphocytes and monocytes across BBB endothelium in vitro and in vivo and reduced the severity and delayed the time of onset of experimental autoimmune encephalomyelitis. Our findings indicate an important function for ALCAM in the recruitment of leukocytes into the brain and identify ALCAM as a potential target for the therapeutic dampening of neuroinflammation.

B7-H4 Modulates Regulatory CD4+ T Cell Induction and Function via Ligation of a Semaphorin 3a/Plexin A4/Neuropilin-1 Complex.

The potent immune regulatory function of an agonistic B7-H4-Ig fusion protein (B7-H4Ig) has been demonstrated in multiple experimental autoimmune models; however, the identity of a functional B7-H4 receptor remained unknown. The biological activity of B7-H4 is associated with decreased inflammatory CD4+ T cell responses as supported by a correlation between B7-H4-expressing tumor-associated macrophages and Foxp3+ T cells within the tumor microenvironment. Recent data indicate that members of the semaphorin (Sema)/plexin/neuropilin (Nrp) family of proteins both positively and negatively modulate immune cell function. In this study, we show that B7-H4 binds the soluble Sema family member Sema3a. Additionally, B7-H4Ig-induced inhibition of inflammatory CD4+ T cell responses is lost in both Sema3a functional mutant mice and mice lacking Nrp-1 expression in Foxp3+ T cells. These findings indicate that B7-H4Ig binds to Sema3a, which acts as a functional bridge to stimulate an Nrp-1/Plexin A4 heterodimer to form a functional immunoregulatory receptor complex resulting in increased levels of phosphorylated PTEN and enhanced regulatory CD4+ T cell number and function.

Biodegradable antigen-associated PLG nanoparticles tolerize Th2-mediated allergic airway inflammation pre- and postsensitization.

Specific immunotherapy (SIT) is the most widely used treatment for allergic diseases that directly targets the T helper 2 (Th2) bias underlying allergy. However, the most widespread clinical applications of SIT require a long period of dose escalation with soluble antigen (Ag) and carry a significant risk of adverse reactions, particularly in highly sensitized patients who stand to benefit most from a curative treatment. Thus, the development of safer, more efficient methods to induce Ag-specific immune tolerance is critical to advancing allergy treatment. We hypothesized that antigen-associated nanoparticles (Ag-NPs), which we have used to prevent and treat Th1/Th17-mediated autoimmune disease, would also be effective for the induction of tolerance in a murine model of Th2-mediated ovalbumin/alum-induced allergic airway inflammation. We demonstrate here that antigen-conjugated polystyrene (Ag-PS) NPs, although effective for the prophylactic induction of tolerance, induce anaphylaxis in presensitized mice. Antigen-conjugated NPs made of biodegradable poly(lactide-co-glycolide) (Ag-PLG) are similarly effective prophylactically, are well tolerated by sensitized animals, but only partially inhibit Th2 responses when administered therapeutically. PLG NPs containing encapsulated antigen [PLG(Ag)], however, were well tolerated and effectively inhibited Th2 responses and airway inflammation both prophylactically and therapeutically. Thus, we illustrate progression toward PLG(Ag) as a biodegradable Ag carrier platform for the safe and effective inhibition of allergic airway inflammation without the need for nonspecific immunosuppression in animals with established Th2 sensitization.

Cutting Edge: MicroRNA-223 Regulates Myeloid Dendritic Cell-Driven Th17 Responses in Experimental Autoimmune Encephalomyelitis.

Myeloid cells play a crucial role in the induction and sustained inflammation in neuroinflammatory disorders, such as multiple sclerosis. miR-223, a myeloid cell-specific microRNA, is one of the most upregulated microRNAs in multiple sclerosis patients. We demonstrate that miR-223-knockout mice display significantly reduced active and adoptive-transfer experimental autoimmune encephalomyelitis that is characterized by reduced numbers of myeloid dendritic cells (mDCs) and Th17 cells in the CNS. Knockout mDCs have increased PD-L1 and decreased IL-1ß, IL-6, and IL-23 expression, as well as a reduced capacity to drive Th17, but not Th1, cell differentiation. Thus, miR-223 controls mDC-induced activation of pathologic Th17 responses during autoimmune inflammation.

Intravenous immune-modifying nanoparticles as a therapy for spinal cord injury in mice.

Intravenously infused synthetic 500nm nanoparticles composed of poly(lactide-co-glycolide) are taken up by blood-borne inflammatory monocytes via a macrophage scavenger receptor (macrophage receptor with collagenous structure), and the monocytes no longer traffic to sites of inflammation. Intravenous administration of the nanoparticles after experimental spinal cord injury in mice safely and selectively limited infiltration of hematogenous monocytes into the injury site. The nanoparticles did not bind to resident microglia, and did not change the number of microglia in the injured spinal cord. Nanoparticle administration reduced M1 macrophage polarization and microglia activation, reduced levels of inflammatory cytokines, and markedly reduced fibrotic scar formation without altering glial scarring. These findings thus implicate early-infiltrating hematogenous monocytes as highly selective contributors to fibrosis that do not play an indispensable role in gliosis after SCI. Further, the nanoparticle treatment reduced accumulation of chondroitin sulfate proteoglycans, increased axon density inside and caudal to the lesion site, and significantly improved functional recovery after both moderate and severe injuries to the spinal cord. These data provide further evidence that hematogenous monocytes contribute to inflammatory damage and fibrotic scar formation after spinal cord injury in mice. Further, since the nanoparticles are simple to administer intravenously, immunologically inert, stable at room temperature, composed of an FDA-approved material, and have no known toxicity, these findings suggest that the nanoparticles potentially offer a practical treatment for human spinal cord injury.

Targeting the GM-CSF receptor for the treatment of CNS autoimmunity.

In multiple sclerosis (MS), there is a growing interest in inhibiting the pro-inflammatory effects of granulocyte-macrophage colony-stimulating factor (GM-CSF). We sought to evaluate the therapeutic potential and underlying mechanisms of GM-CSF receptor alpha (Rα) blockade in animal models of MS. We show that GM-CSF signaling inhibition at peak of chronic experimental autoimmune encephalomyelitis (EAE) results in amelioration of disease progression. Similarly, GM-CSF Rα blockade in relapsing-remitting (RR)-EAE model prevented disease relapses and inhibited T cell responses specific for both the inducing and spread myelin peptides, while reducing activation of mDCs and inflammatory monocytes. In situ immunostaining of lesions from human secondary progressive MS (SPMS), but not primary progressive MS patients shows extensive recruitment of GM-CSF Rα+ myeloid cells. Collectively, this study reveals a pivotal role of GM-CSF in disease relapses and the benefit of GM-CSF Rα blockade as a potential novel therapeutic approach for treatment of RRMS and SPMS.

Human TH17 lymphocytes promote blood-brain barrier disruption and central nervous system inflammation.

T(H)17 lymphocytes appear to be essential in the pathogenesis of numerous inflammatory diseases. We demonstrate here the expression of IL-17 and IL-22 receptors on blood-brain barrier endothelial cells (BBB-ECs) in multiple sclerosis lesions, and show that IL-17 and IL-22 disrupt BBB tight junctions in vitro and in vivo. Furthermore, T(H)17 lymphocytes transmigrate efficiently across BBB-ECs, highly express granzyme B, kill human neurons and promote central nervous system inflammation through CD4+ lymphocyte recruitment.

Adult microglial TGFß1 is required for microglia homeostasis via an autocrine mechanism to maintain cognitive function in mice.

While TGF-ß signaling is essential for microglial function, the cellular source of TGF-ß1 ligand and its spatial regulation remains unclear in the adult CNS. Our data supports that microglia but not astrocytes or neurons are the primary producers of TGF-ß1 ligands needed for microglial homeostasis. Microglia-Tgfb1 KO leads to the activation of microglia featuring a dyshomeostatic transcriptome that resembles disease-associated, injury-associated, and aged microglia, suggesting microglial self-produced TGF-ß1 ligands are important in the adult CNS. Astrocytes in MG-Tgfb1 inducible (i)KO mice show a transcriptome profile that is closely aligned with an LPS-associated astrocyte profile. Additionally, using sparse mosaic single-cell microglia KO of TGF-ß1 ligand we established an autocrine mechanism for signaling. Here we show that MG-Tgfb1 iKO mice present cognitive deficits, supporting that precise spatial regulation of TGF-ß1 ligand derived from microglia is required for the maintenance of brain homeostasis and normal cognitive function in the adult brain.

B cell-derived IL-15 enhances CD8 T cell cytotoxicity and is increased in multiple sclerosis patients.

Multiple lines of evidence suggest that CD8 T cells contribute to the pathogenesis of multiple sclerosis (MS). However, the sources and involvement of cytokines such as IL-15 in activating these cells is still unresolved. To investigate the role of IL-15 in enhancing the activation of CD8 T cells in the context of MS, we determined cell types expressing the bioactive surface IL-15 in the peripheral blood of patients and evaluated the impact of this cytokine on CD8 T cell cytotoxicity and migration. Flow cytometric analysis showed a significantly greater proportion of B cells and monocytes from MS patients expressing IL-15 relative to controls. We established that CD40L activation of B cells from healthy donors increased their IL-15 levels, reaching those of MS patients. We also demonstrated an enhanced cytotoxic profile in CD8 T cells from MS patients upon stimulation with IL-15. Furthermore, we showed that IL-15 expressed by B cells and monocytes is sufficient and functional, enhancing granzyme B production by CD8 T cells upon coculture. Exposure of CD8 T cells to this cytokine enhanced their ability to kill glial cells as well as to migrate across an in vitro inflamed human blood-brain barrier. The elevated levels of IL-15 in patients relative to controls, the greater susceptibility of CD8 T cells from patients to IL-15, in addition to the enhanced cytotoxic responses by IL-15-exposed CD8 T cells, stresses the potential of therapeutic strategies to reduce peripheral sources of IL-15 in MS.

Melanoma cell adhesion molecule identifies encephalitogenic T lymphocytes and promotes their recruitment to the central nervous system.

In multiple sclerosis, encephalitogenic CD4(+) lymphocytes require adhesion molecules to accumulate into central nervous system inflammatory lesions. Using proteomic techniques, we identified expression of melanoma cell adhesion molecule (MCAM) on a subset of human effector memory CD4(+) lymphocytes and on human blood-brain barrier endothelium. Herein, we demonstrate that MCAM is a stable surface marker that refines the identification of interleukin 17(+), interleukin 22(+), RAR-related orphan receptor γ and interleukin 23 receptor(+) cells within the CD161(+)CCR6(+) subset of memory CD4(+) lymphocytes. We also show that MCAM(+) lymphocytes express significantly more granulocyte/macrophage colony stimulating factor and granzyme B than MCAM(-) lymphocytes. Furthermore, the proportion of MCAM(+) CD4(+) lymphocytes is significantly increased in the blood and in the central nervous system of patients with multiple sclerosis and experimental autoimmune encephalomyelitis animals compared with healthy controls or other neurological diseases, and MCAM expression is upregulated at the blood-brain barrier within inflammatory lesions. Moreover, blockade of MCAM or depletion of MCAM(+) CD4(+) T lymphocytes both restrict the migration of T(H)17 lymphocytes across blood-brain barrier endothelial cells and decrease the severity of experimental autoimmune encephalomyelitis. Our findings indicate that MCAM could serve as a potential biomarker for multiple sclerosis and represents a valuable target for the treatment of neuroinflammatory conditions.

Microglia-derived TGF-ß1 ligand maintains microglia homeostasis via autocrine mechanism and is critical for normal cognitive function in adult mouse brain.

While TGF-ß signaling is essential for microglial function, the cellular source of TGF-ß ligand and its spatial regulation remains unclear in the adult CNS. Our data support that microglia, not astrocytes or neurons, are the primary producers of TGF-ß1 ligands needed for microglial homeostasis. Microglia (MG)-Tgfb1 inducible knockout (iKO) leads to the activation of microglia featuring a dyshomeostatic transcriptomic profile that resembles disease-associated microglia (DAMs), injury-associated microglia, and aged microglia, suggesting that microglial self-produced TGF-ß1 ligands are important in the adult CNS. Interestingly, astrocytes in MG-Tgfb1 iKO mice show a transcriptome profile that closely aligns with A1-like astrocytes. Additionally, using sparse mosaic single-cell microglia iKO of TGF-ß1 ligand, we established an autocrine mechanism for TGF-ß signaling. Importantly MG-Tgfb1 iKO mice show cognitive deficits, supporting that precise spatial regulation of TGF-ß1 ligand derived from microglia is critical for the maintenance of brain homeostasis and normal cognitive function in the adult brain.

Role of Ninjurin-1 in the migration of myeloid cells to central nervous system inflammatory lesions.

OBJECTIVE: Blood-derived myeloid antigen-presenting cells (APCs) account for a significant proportion of the leukocytes found within lesions of multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). These APCs along with activated microglia are thought to be pivotal in the initiation of the central nervous system (CNS)-targeted immune response in MS and EAE. However, the exact molecules that direct the migration of myeloid cells from the periphery across the blood-brain barrier (BBB) remain largely unknown. METHODS: We identified Ninjurin-1 in a proteomic screen of human BBB endothelial cells (ECs). We assessed the expression of Ninjurin-1 by BBB-ECs and immune cells, and we determined the role of Ninjurin-1 in immune cell migration to the CNS in vivo in EAE mice. RESULTS: Ninjurin-1 was found to be weakly expressed in the healthy human and mouse CNS but upregulated on BBB-ECs and on infiltrating APCs during the course of EAE and in active MS lesions. In human peripheral blood, Ninjurin-1 was predominantly expressed by monocytes, whereas it was barely detectable on T and B lymphocytes. Moreover, Ninjurin-1 neutralization specifically abrogated the adhesion and migration of human monocytes across BBB-ECs, without affecting lymphocyte recruitment. Finally, Ninjurin-1 blockade reduced clinical disease activity and histopathological indices of EAE and decreased infiltration of macrophages, dendritic cells, and APCs into the CNS. INTERPRETATION: Our study uncovers an important cell-specific role for Ninjurin-1 in the transmigration of inflammatory APCs across the BBB and further emphasizes the importance of myeloid cell recruitment during the development of neuroinflammatory lesions.

Central nervous system recruitment of effector memory CD8+ T lymphocytes during neuroinflammation is dependent on α4 integrin.

Clonally expanded CD8(+) T lymphocytes are present in multiple sclerosis lesions, as well as in the cerebrospinal fluid of patients with multiple sclerosis. In experimental autoimmune encephalomyelitis, CD8(+) T lymphocytes are found in spinal cord and brainstem lesions. However, the exact phenotype of central nervous system-infiltrating CD8(+) T lymphocytes and the mechanism by which these cells cross the blood-brain barrier remain largely unknown. Using cerebrospinal fluid from patients with multiple sclerosis, spinal cord from experimental autoimmune encephalomyelitis and coronavirus-induced encephalitis, we demonstrate that central nervous system-infiltrating CD8(+) T lymphocytes are mostly of the effector memory phenotype (CD62L(-) CCR7(-) granzymeB(hi)). We further show that purified human effector memory CD8(+) T lymphocytes transmigrate more readily across blood-brain barrier-endothelial cells than non-effector memory CD8(+) T lymphocytes, and that blood-brain barrier endothelium promotes the selective recruitment of effector memory CD8(+) T lymphocytes. Furthermore, we provide evidence for the recruitment of interferon-γ- and interleukin-17-secreting CD8(+) T lymphocytes by human and mouse blood-brain barrier endothelium. Finally, we show that in vitro migration of CD8(+) T lymphocytes across blood-brain barrier-endothelial cells is dependent on α4 integrin, but independent of intercellular adhesion molecule-1/leucocyte function-associated antigen-1, activated leucocyte cell adhesion molecule/CD6 and the chemokine monocyte chemotactic protein-1/CCL2. We also demonstrate that in vivo neutralization of very late antigen-4 restricts central nervous system infiltration of CD8(+) T lymphocytes in active immunization and adoptive transfer experimental autoimmune encephalomyelitis, and in coronavirus-induced encephalitis. Our study thus demonstrates an active role of the blood-brain barrier in the recruitment of effector memory CD8(+) T lymphocytes to the CNS compartment and defines α4 integrin as a major contributor of CD8(+) T lymphocyte entry into the brain.

PLG nanoparticles target fibroblasts and MARCO+ monocytes to reverse multiorgan fibrosis.

Systemic sclerosis (SSc) is a chronic, multisystem orphan disease with a highly variable clinical course, high mortality rate, and a poorly understood complex pathogenesis. We have identified an important role for a subpopulation of monocytes and macrophages characterized by surface expression of the scavenger receptor macrophage receptor with collagenous structure (MARCO) in chronic inflammation and fibrosis in SSc and in preclinical disease models. We show that MARCO+ monocytes and macrophages accumulate in lesional skin and lung in topographic proximity to activated myofibroblasts in patients with SSc and in the bleomycin-induced mouse model of SSc. Short-term treatment of mice with a potentially novel nanoparticle, poly(lactic-co-glycolic) acid (PLG), which is composed of a carboxylated, FDA-approved, biodegradable polymer and modulates activation and trafficking of MARCO+ inflammatory monocytes, markedly attenuated bleomycin-induced skin and lung inflammation and fibrosis. Mechanistically, in isolated cells in culture, PLG nanoparticles inhibited TGF-dependent fibrotic responses in vitro. Thus, MARCO+ monocytes are potent effector cells of skin and lung fibrosis and can be therapeutically targeted in SSc using PLG nanoparticles.

Biodegradable nanoparticles induce cGAS/STING-dependent reprogramming of myeloid cells to promote tumor immunotherapy.

Cancer treatment utilizing infusion therapies to enhance the patient's own immune response against the tumor have shown significant functionality in a small subpopulation of patients. Additionally, advances have been made in the utilization of nanotechnology for the treatment of disease. We have previously reported the potent effects of 3-4 daily intravenous infusions of immune modifying poly(lactic-co-glycolic acid) (PLGA) nanoparticles (IMPs; named ONP-302) for the amelioration of acute inflammatory diseases by targeting myeloid cells. The present studies describe a novel use for ONP-302, employing an altered dosing scheme to reprogram myeloid cells resulting in significant enhancement of tumor immunity. ONP-302 infusion decreased tumor growth via the activation of the cGAS/STING pathway within myeloid cells, and subsequently increased NK cell activation via an IL-15-dependent mechanism. Additionally, ONP-302 treatment increased PD-1/PD-L1 expression in the tumor microenvironment, thereby allowing for functionality of anti-PD-1 for treatment in the B16.F10 melanoma tumor model which is normally unresponsive to monotherapy with anti-PD-1. These findings indicate that ONP-302 allows for tumor control via reprogramming myeloid cells via activation of the STING/IL-15/NK cell mechanism, as well as increasing anti-PD-1 response rates.

Tolerance Induced by Antigen-Loaded PLG Nanoparticles Affects the Phenotype and Trafficking of Transgenic CD4+ and CD8+ T Cells.

We have shown that PLG nanoparticles loaded with peptide antigen can reduce disease in animal models of autoimmunity and in a phase 1/2a clinical trial in celiac patients. Clarifying the mechanisms by which antigen-loaded nanoparticles establish tolerance is key to further adapting them to clinical use. The mechanisms underlying tolerance induction include the expansion of antigen-specific CD4+ regulatory T cells and sequestration of autoreactive cells in the spleen. In this study, we employed nanoparticles loaded with two model peptides, GP33-41 (a CD8 T cell epitope derived from lymphocytic choriomeningitis virus) and OVA323-339 (a CD4 T cell epitope derived from ovalbumin), to modulate the CD8+ and CD4+ T cells from two transgenic mouse strains, P14 and DO11.10, respectively. Firstly, it was found that the injection of P14 mice with particles bearing the MHC I-restricted GP33-41 peptide resulted in the expansion of CD8+ T cells with a regulatory cell phenotype. This correlated with reduced CD4+ T cell viability in ex vivo co-cultures. Secondly, both nanoparticle types were able to sequester transgenic T cells in secondary lymphoid tissue. Flow cytometric analyses showed a reduction in the surface expression of chemokine receptors. Such an effect was more prominently observed in the CD4+ cells rather than the CD8+ cells.

ZEB1 promotes pathogenic Th1 and Th17 cell differentiation in multiple sclerosis.

Inappropriate CD4+ T helper (Th) differentiation can compromise host immunity or promote autoimmune disease. To identify disease-relevant regulators of T cell fate, we examined mutations that modify risk for multiple sclerosis (MS), a canonical organ-specific autoimmune disease. This analysis identified a role for Zinc finger E-box-binding homeobox (ZEB1). Deletion of ZEB1 protects against experimental autoimmune encephalitis (EAE), a mouse model of multiple sclerosis (MS). Mechanistically, ZEB1 in CD4+ T cells is required for pathogenic Th1 and Th17 differentiation. Genomic analyses of paired human and mouse expression data elucidated an unexpected role for ZEB1 in JAK-STAT signaling. ZEB1 inhibits miR-101-3p that represses JAK2 expression, STAT3/STAT4 phosphorylation, and subsequent expression of interleukin-17 (IL-17) and interferon gamma (IFN-γ). Underscoring its clinical relevance, ZEB1 and JAK2 downregulation decreases pathogenic cytokines expression in T cells from MS patients. Moreover, a Food and Drug Administration (FDA)-approved JAK2 inhibitor is effective in EAE. Collectively, these findings identify a conserved, potentially targetable mechanism regulating disease-relevant inflammation.