Activation of limbal epithelial proliferation is partly controlled by the ACE2-LCN2 pathway.

In response to corneal injury, an activation of corneal epithelial stem cells and their direct progeny the early transit amplifying (eTA) cells to rapidly proliferate is critical for proper re-epithelialization. Thus, it is important to understand how such stem/eTA cell activation is regulated. Angiotensin-converting enzyme 2 (ACE2) is predominantly expressed in the stem/eTA-enriched limbal epithelium but its role in the limbal epithelium was unclear. Single cell RNA sequencing (scRNA-seq) suggested that Ace2 involved the proliferation of the stem/eTA cells. Ace2 was reduced following corneal injury. Such reduction enhanced limbal epithelial proliferation and downregulated LCN2, a negative regulator of proliferation in a variety of tissues, via upregulating TGFA and consequently activating epidermal growth factor receptor (EGFR). Inhibition of EGFR or overexpression of LCN2 reversed the increased proliferation in limbal epithelial cells lacking ACE2. Our findings demonstrate that after corneal injury, ACE2 is downregulated, which activates limbal epithelial cell proliferation via a TGFA/EGFR/LCN2 pathway.

Therapeutic role of interferon-γ in experimental autoimmune encephalomyelitis is mediated through a tolerogenic subset of splenic CD11b+ myeloid cells.

Cumulative evidence has established that Interferon (IFN)-γ has both pathogenic and protective roles in Multiple Sclerosis and the animal model, Experimental Autoimmune Encephalomyelitis (EAE). However, the underlying mechanisms to the beneficial effects of IFN-γ are not well understood. In this study, we found that IFN-γ exerts therapeutic effects on chronic, relapsing-remitting, and chronic progressive EAE models. The frequency of regulatory T (Treg) cells in spinal cords from chronic EAE mice treated with IFN-γ was significantly increased with no effect on Th1 and Th17 cells. Consistently, depletion of FOXP3-expressing cells blocked the protective effects of IFN-γ, indicating that the therapeutic effect of IFN-γ depends on the presence of Treg cells. However, IFN-γ did not trigger direct in vitro differentiation of Treg cells. In vivo administration of blocking antibodies against either interleukin (IL)-10, transforming growth factor (TGF)-ß or program death (PD)-1, revealed that the protective effects of IFN-γ in EAE were also dependent on TGF-ß and PD-1, but not on IL-10, suggesting that IFN-γ might have an indirect role on Treg cells acting through antigen-presenting cells. Indeed, IFN-γ treatment increased the frequency of a subset of splenic CD11b+ myeloid cells expressing TGF-ß-Latency Associated Peptide (LAP) and program death ligand 1 (PD-L1) in a signal transducer and activator of transcription (STAT)-1-dependent manner. Furthermore, splenic CD11b+ cells from EAE mice preconditioned in vitro with IFN-γ and myelin oligodendrocyte glycoprotein (MOG) peptide exhibited a tolerogenic phenotype with the capability to induce conversion of naïve CD4+ T cells mediated by secretion of TGF-ß. Remarkably, adoptive transfer of splenic CD11b+ cells from IFN-γ-treated EAE mice into untreated recipient mice ameliorated clinical symptoms of EAE and limited central nervous system infiltration of mononuclear cells and effector helper T cells. These results reveal a novel cellular and molecular mechanism whereby IFN-γ promotes beneficial effects in EAE by endowing splenic CD11b+ myeloid cells with tolerogenic and therapeutic activities.

Allergen-Encapsulating Nanoparticles Reprogram Pathogenic Allergen-Specific Th2 Cells to Suppress Food Allergy.

Food allergy is a prevalent, potentially deadly disease caused by inadvertent sensitization to benign food antigens. Pathogenic Th2 cells are a major driver for disease, and allergen-specific immunotherapies (AIT) aim to increase the allergen threshold required to elicit severe allergic symptoms. However, the majority of AIT approaches require lengthy treatments and convey transient disease suppression, likely due to insufficient targeting of pathogenic Th2 responses. Here, the ability of allergen-encapsulating nanoparticles to directly suppress pathogenic Th2 responses and reactivity is investigated in a mouse model of food allergy. NPs associate with pro-tolerogenic antigen presenting cells, provoking accumulation of antigen-specific, functionally suppressive regulatory T cells in the small intestine lamina propria. Two intravenous doses of allergen encapsulated in poly(lactide-co-glycolide) nanoparticles (NPs) significantly reduces oral food challenge (OFC)-induced anaphylaxis. Importantly, NP treatment alters the fates of pathogenic allergen-specific Th2 cells, reprogramming these cells toward CD25+FoxP3+ regulatory and CD73+FR4+ anergic phenotypes. NP-mediated reductions in the frequency of effector cells in the gut and mast cell degranulation following OFC are also demonstrated. These studies reveal mechanisms by which an allergen-encapsulating NP therapy and, more broadly, allergen-specific immunotherapies, can rapidly attenuate allergic responses by targeting pathogenic Th2 cells.

Characterization of hyperpolarization-activated cyclic nucleotide-gated channels in oligodendrocytes.

Mature oligodendrocytes (OLG) are the myelin-forming cells of the central nervous system. Recent work has shown a dynamic role for these cells in the plasticity of neural circuits, leading to a renewed interest in voltage-sensitive currents in OLG. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and their respective current (Ih) were recently identified in mature OLG and shown to play a role in regulating myelin length. Here we provide a biochemical and electrophysiological characterization of HCN channels in cells of the oligodendrocyte lineage. We observed that mice with a nonsense mutation in the Hcn2 gene (Hcn2ap/ap) have less white matter than their wild type counterparts with fewer OLG and fewer oligodendrocyte progenitor cells (OPCs). Hcn2ap/ap mice have severe motor impairments, although these deficits were not observed in mice with HCN2 conditionally eliminated only in oligodendrocytes (Cnpcre/+; Hcn2F/F). However, Cnpcre/+; Hcn2F/F mice develop motor impairments more rapidly in response to experimental autoimmune encephalomyelitis (EAE). We conclude that HCN2 channels in OLG may play a role in regulating metabolism.

Rotator Cuff Tears Are Related to the Side Sleeping Position.

Purpose: To determine whether there was a relationship between sleep position and symptomatic partial- and full-thickness rotator cuff tears. Methods: A consecutive series of patients that met the inclusion/exclusion criteria (n = 58) were in seen in clinic between July 2019 and December 2019. All of these individuals had a significant partial-thickness (> 50%) or full-thickness rotator cuff tear determined by either ultrasound, magnetic resonance imaging, or both. All patients in this series either had an insidious onset of shoulder pain or their symptoms were related to the basic wear and tear of daily activities. Traumatic rotator cuff tears (those associated with a significant traumatic event such as shoulder instability, motor vehicle accidents, sports related injuries, etc.) were excluded. Previous shoulder surgery, recurrent rotator cuff tears, and worker's compensation cases also were excluded from this series. As part of the history-taking process, the patients were asked what was their preferred sleeping position-side sleeper, back sleeper, or stomach sleeper. A χ2 test was conducted to determine the relationship between rotator cuff pathology and sleep position. Results: Of the 58 subjects, 52 of the patients were side sleepers, 4 were stomach sleepers, 1 was a back sleeper, and 1 preferred all 3 positions. Statistical analysis, using the χ2 test (P < .0001), demonstrated that rotator cuff tears were most often seen in side sleepers. Conclusions: In our study, there appeared to be a relationship between the preference of being a side sleeper and the presence of a rotator cuff tear. Level of Evidence: Level IV, prognostic case series.

The immune system and metabolic products in epilepsy and glioma-associated epilepsy: emerging therapeutic directions.

Epilepsy has a profound impact on quality of life. Despite the development of new antiseizure medications (ASMs), approximately one-third of affected patients have drug-refractory epilepsy and are nonresponsive to medical treatment. Nearly all currently approved ASMs target neuronal activity through ion channel modulation. Recent human and animal model studies have implicated new immunotherapeutic and metabolomic approaches that may benefit patients with epilepsy. In this Review, we detail the proinflammatory immune landscape of epilepsy and contrast this with the immunosuppressive microenvironment in patients with glioma-related epilepsy. In the tumor setting, excessive neuronal activity facilitates immunosuppression, thereby contributing to subsequent glioma progression. Metabolic modulation of the IDH1-mutant pathway provides a dual pathway for reversing immune suppression and dampening seizure activity. Elucidating the relationship between neurons and immunoreactivity is an area for the prioritization and development of the next era of ASMs.

Interferon-γ controls aquaporin 4-specific Th17 and B cells in neuromyelitis optica spectrum disorder.

Neuromyelitis optica spectrum disorder (NMOSD) is a CNS autoimmune inflammatory disease mediated by T helper 17 (Th17) and antibody responses to the water channel protein, aquaporin 4 (AQP4), and associated with astrocytopathy, demyelination and axonal loss. Knowledge about disease pathogenesis is limited and the search for new therapies impeded by the absence of a reliable animal model. In our work, we determined that NMOSD is characterized by decreased IFN-γ receptor signalling and that IFN-γ depletion in AQP4201-220-immunized C57BL/6 mice results in severe clinical disease resembling human NMOSD. Pathologically, the disease causes autoimmune astrocytic and CNS injury secondary to cellular and humoral inflammation. Immunologically, the absence of IFN-γ allows for increased expression of IL-6 in B cells and activation of Th17 cells, and generation of a robust autoimmune inflammatory response. Consistent with NMOSD, the experimental disease is exacerbated by administration of IFN-ß, whereas repletion of IFN-γ, as well as therapeutic targeting of IL-17A, IL-6R and B cells, ameliorates it. We also demonstrate that immune tolerization with AQP4201-220-coupled poly(lactic-co-glycolic acid) nanoparticles could both prevent and effectively treat the disease. Our findings enhance the understanding of NMOSD pathogenesis and provide a platform for the development of immune tolerance-based therapies, avoiding the limitations of the current immunosuppressive therapies.

Engineering nanoparticle therapeutics for food allergy.

Food allergy is a growing public health issue among children and adults that can lead to life-threatening anaphylaxis following allergen exposure. The criterion standard for disease management includes food avoidance and emergency epinephrine administration because current allergen-specific immunotherapy treatments are limited by adverse events and unsustained desensitization. A promising approach to remedy these shortcomings is the use of nanoparticle-based therapies that disrupt disease-driving immune mechanisms and induce more sustained tolerogenic immune pathways. The pathophysiology of food allergy includes multifaceted interactions between effector immune cells, including lymphocytes, antigen-presenting cells, mast cells, and basophils, mainly characterized by a TH2 cell response. Regulatory T cells, TH1 cell responses, and suppression of other major allergic effector cells have been found to be major drivers of beneficial outcomes in these nanoparticle therapies. Engineered nanoparticle formulations that have shown efficacy at reducing allergic responses and revealed new mechanisms of tolerance include polymeric-, lipid-, and emulsion-based nanotherapeutics. This review highlights the recent engineering design of these nanoparticles, the mechanisms induced by them, and their future potential therapeutic targets.

Topical application of synthetic melanin promotes tissue repair.

In acute skin injury, healing is impaired by the excessive release of reactive oxygen species (ROS). Melanin, an efficient scavenger of radical species in the skin, performs a key role in ROS scavenging in response to UV radiation and is upregulated in response to toxic insult. In a chemical injury model in mice, we demonstrate that the topical application of synthetic melanin particles (SMPs) significantly decreases edema, reduces eschar detachment time, and increases the rate of wound area reduction compared to vehicle controls. Furthermore, these results were replicated in a UV-injury model. Immune array analysis shows downregulated gene expression in apoptotic and inflammatory signaling pathways consistent with histological reduction in apoptosis. Mechanistically, synthetic melanin intervention increases superoxide dismutase (SOD) activity, decreases Mmp9 expression, and suppresses ERK1/2 phosphorylation. Furthermore, we observed that the application of SMPs caused increased populations of anti-inflammatory immune cells to accumulate in the skin, mirroring their decrease from splenic populations. To enhance antioxidant capacity, an engineered biomimetic High Surface Area SMP was deployed, exhibiting increased wound healing efficiency. Finally, in human skin explants, SMP intervention significantly decreased the damage caused by chemical injury. Therefore, SMPs are promising and effective candidates as topical therapies for accelerated wound healing, including via pathways validated in human skin.

Interferon-gamma ameliorates experimental autoimmune encephalomyelitis by inducing homeostatic adaptation of microglia.

Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b+ myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-γ-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen, promoted a significantly higher induction of CD4+ regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-ß secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1high MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1highPD-L1lowCD11b+Ly6G- cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1highPD-L1low MG). Amelioration of clinical symptoms and induction of CX3CR1highPD-L1low MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-γ promoted the induction of homeostatic CX3CR1highPD-L1low MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE.

Nanoparticle dose and antigen loading attenuate antigen-specific T-cell responses.

Immune-mediated hypersensitivities such as autoimmunity, allergy, and allogeneic graft rejection are treated with therapeutics that suppress the immune system, and the lack of specificity is associated with significant side effects. The delivery of disease-relevant antigens (Ags) by carrier systems such as poly(lactide-co-glycolide) nanoparticles (PLG-Ag) and carbodiimide (ECDI)-fixed splenocytes (SP-Ag) has demonstrated Ag-specific tolerance induction in model systems of these diseases. Despite therapeutic outcomes by both platforms, tolerance is conferred with different efficacy. This investigation evaluated Ag loading and total particle dose of PLG-Ag on Ag presentation in a coculture system of dendritic cells (DCs) and Ag-restricted T cells, with SP-Ag employed as a control. CD25 expression was observed in nearly all T cells even at low concentrations of PLG-Ag, indicating efficient presentation of Ag by dendritic cells. However, the secretion of IL-2, Th1, and Th2 cytokines (IFNγ and IL-4, respectively) varied depending on PLG-Ag concentration and Ag loading. Concentration escalation of soluble Ag resulted in an increase in IL-2 and IFNγ and a decrease in IL-4. Treatment with PLG-Ag followed a similar trend but with lower levels of IL-2 and IFNγ secreted. Transcriptional Activity CEll ARrays (TRACER) were employed to measure the real-time transcription factor (TF) activity in Ag-presenting DCs. The kinetics and magnitude of TF activity was dependent on the Ag delivery method, concentration, and Ag loading. Ag positively regulated IRF1 activity and, as carriers, NPs and ECDI-treated SP negatively regulated this signaling. The effect of Ag loading and dose on tolerance induction were corroborated in vivo using the delayed-type hypersensitivity (DTH) and experimental autoimmune encephalomyelitis (EAE) mouse models where a threshold of 8 µg/mg Ag loading and 0.5 mg PLG-Ag dose were required for tolerance. Together, the effect of Ag loading and dosing on in vitro and in vivo immune regulation provide useful insights for translating Ag-carrier systems for the clinical treatment of immune disorders.

Fibroblast A20 governs fibrosis susceptibility and its repression by DREAM promotes fibrosis in multiple organs.

In addition to autoimmune and inflammatory diseases, variants of the TNFAIP3 gene encoding the ubiquitin-editing enzyme A20 are also associated with fibrosis in systemic sclerosis (SSc). However, it remains unclear how genetic factors contribute to SSc pathogenesis, and which cell types drive the disease due to SSc-specific genetic alterations. We therefore characterize the expression, function, and role of A20, and its negative transcriptional regulator DREAM, in patients with SSc and disease models. Levels of A20 are significantly reduced in SSc skin and lungs, while DREAM is elevated. In isolated fibroblasts, A20 mitigates ex vivo profibrotic responses. Mice haploinsufficient for A20, or harboring fibroblasts-specific A20 deletion, recapitulate major pathological features of SSc, whereas DREAM-null mice with elevated A20 expression are protected. In DREAM-null fibroblasts, TGF-ß induces the expression of A20, compared to wild-type fibroblasts. An anti-fibrotic small molecule targeting cellular adiponectin receptors stimulates A20 expression in vitro in wild-type but not A20-deficient fibroblasts and in bleomycin-treated mice. Thus, A20 has a novel cell-intrinsic function in restraining fibroblast activation, and together with DREAM, constitutes a critical regulatory network governing the fibrotic process in SSc. A20 and DREAM represent novel druggable targets for fibrosis therapy.

Immune activation is essential for the antitumor activity of EZH2 inhibition in urothelial carcinoma.

The long-term survival of patients with advanced urothelial carcinoma (UCa) is limited because of innate resistance to treatment. We identified elevated expression of the histone methyltransferase EZH2 as a hallmark of aggressive UCa and hypothesized that EZH2 inhibition, via a small-molecule catalytic inhibitor, might have antitumor effects in UCa. Here, in a carcinogen-induced mouse bladder cancer model, a reduction in tumor progression and an increase in immune infiltration upon EZH2 inhibition were observed. Treatment of mice with EZH2i causes an increase in MHC class II expression in the urothelium and can activate infiltrating T cells. Unexpectedly, we found that the lack of an intact adaptive immune system completely abolishes the antitumor effects induced by EZH2 catalytic inhibition. These findings show that immune evasion is the only important determinant for the efficacy of EZH2 catalytic inhibition treatment in a UCa model.

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.

Repurposing the cardiac glycoside digoxin to stimulate myelin regeneration in chemically-induced and immune-mediated mouse models of multiple sclerosis.

Multiple sclerosis (MS) is a central nervous system (CNS) autoimmune disease characterized by inflammation, demyelination, and neurodegeneration. The ideal MS therapy would both specifically inhibit the underlying autoimmune response and promote repair/regeneration of myelin as well as maintenance of axonal integrity. Currently approved MS therapies consist of non-specific immunosuppressive molecules/antibodies which block activation or CNS homing of autoreactive T cells, but there are no approved therapies for stimulation of remyelination nor maintenance of axonal integrity. In an effort to repurpose an FDA-approved medication for myelin repair, we chose to examine the effectiveness of digoxin, a cardiac glycoside (Na+ /K+ ATPase inhibitor), originally identified as pro-myelinating in an in vitro screen. We found that digoxin regulated multiple genes in oligodendrocyte progenitor cells (OPCs) essential for oligodendrocyte (OL) differentiation in vitro, promoted OL differentiation both in vitro and in vivo in female naïve C57BL/6J (B6) mice, and stimulated recovery of myelinated axons in B6 mice following demyelination in the corpus callosum induced by cuprizone and spinal cord demyelination induced by lysophosphatidylcholine (LPC), respectively. More relevant to treatment of MS, we show that digoxin treatment of mice with established MOG35-55 -induced Th1/Th17-mediated chronic EAE combined with tolerance induced by the i.v. infusion of biodegradable poly(lactide-co-glycolide) nanoparticles coupled with MOG35-55 (PLG-MOG35-55 ) completely ameliorated clinical disease symptoms and stimulated recovery of OL lineage cell numbers. These findings provide critical pre-clinical evidence supporting future clinical trials of myelin-specific tolerance with myelin repair/regeneration drugs, such as digoxin, in MS patients.

Tolerogenic Immune-Modifying Nanoparticles Encapsulating Multiple Recombinant Pancreatic ß Cell Proteins Prevent Onset and Progression of Type 1 Diabetes in Nonobese Diabetic Mice.

Type 1 diabetes (T1D) is an autoimmune disease characterized by T and B cell responses to proteins expressed by insulin-producing pancreatic ß cells, inflammatory lesions within islets (insulitis), and ß cell loss. We previously showed that Ag-specific tolerance targeting single ß cell protein epitopes is effective in preventing T1D induced by transfer of monospecific diabetogenic CD4 and CD8 transgenic T cells to NOD.scid mice. However, tolerance induction to individual diabetogenic proteins, for example, GAD65 (glutamic acid decarboxylase 65) or insulin, has failed to ameliorate T1D both in wild-type NOD mice and in the clinic. Initiation and progression of T1D is likely due to activation of T cells specific for multiple diabetogenic epitopes. To test this hypothesis, recombinant insulin, GAD65, and chromogranin A proteins were encapsulated within poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles (COUR CNPs) to assess regulatory T cell induction, inhibition of Ag-specific T cell responses, and blockade of T1D induction/progression in NOD mice. Whereas treatment of NOD mice with CNPs containing a single protein inhibited the corresponding Ag-specific T cell response, inhibition of overt T1D development only occurred when all three diabetogenic proteins were included within the CNPs (CNP-T1D). Blockade of T1D following CNP-T1D tolerization was characterized by regulatory T cell induction and a significant decrease in both peri-insulitis and immune cell infiltration into pancreatic islets. As we have recently published that CNP treatment is both safe and induced Ag-specific tolerance in a phase 1/2a celiac disease clinical trial, Ag-specific tolerance induced by nanoparticles encapsulating multiple diabetogenic proteins is a promising approach to T1D treatment.

Masked Delivery of Allergen in Nanoparticles Safely Attenuates Anaphylactic Response in Murine Models of Peanut Allergy.

Food allergy is a growing health concern worldwide. Current allergen-specific immunotherapy (AIT) approaches require frequent dosing over extended periods of time and may induce anaphylaxis due to allergen-effector cell interactions. A critical need remains to develop novel approaches that refine AIT for the treatment of food allergies. Previous studies show that poly(lactide-co-glycolide) (PLG) nanoscale particles (NP) effectively suppress Th1- and Th17-driven immune pathologies. However, their ability to suppress the distinct Th2-polarized immune responses driving food allergy are unknown. Herein, we describe the safety and efficacy of NPs containing encapsulated peanut allergen in desensitizing murine models of peanut allergy. Peanut extract encapsulation allowed for the safe intravenous delivery of allergen relative to non-encapsulated approaches. Application of 2-3 doses, without the need for dose escalation, was sufficient to achieve prophylactic and therapeutic efficacy, which correlated with suppression of Th2-mediated disease and reduced mast cell degranulation. Efficacy was associated with strong reductions in a broad panel of Th1, Th2, and Th17 cytokines. These results demonstrate the ability of PLG NPs to suppress allergen-specific immune responses to induce a more tolerogenic phenotype, conferring protection from intragastric allergen challenge. These promising studies represent a step forward in the development of improved immunotherapies for food allergy.

Mechanistic contributions of Kupffer cells and liver sinusoidal endothelial cells in nanoparticle-induced antigen-specific immune tolerance.

The intravenous delivery of disease-relevant antigens (Ag) by polymeric nanoparticles (NP-Ags) has demonstrated Ag-specific immune tolerance in autoimmune and allergic disorders as well as allogeneic transplant rejection. NP-Ags are observed to distribute to the spleen, which has an established role in the induction of immune tolerance. However, studies have shown that the spleen is dispensable for NP-Ag-induced tolerance, suggesting significant contributions from other immunological sites. Here, we investigated the tolerogenic contributions of Kupffer cells (KCs) and liver sinusoidal endothelial cells (LSECs) to NP-Ag-induced tolerance in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Intravenously delivered Ag-conjugated poly(lactide-co-glycolide) NPs (PLG-Ag) distributed largely to the liver, where they associated with both KCs and LSECs. This distribution was accompanied by CD4 T cell accumulation, clonal deletion, and PD-L1 expression by KCs and LSECs. Ex vivo co-cultures of PLG-Ag-treated KCs or LSECs with Ag-specific CD4 T cells resulted in PGE2 and IL-10 or PGE2 secretion, respectively. KC depletion and adoptive transfer experiments demonstrated that KCs were sufficient, but not necessary, to mediate PLG-Ag-induced tolerance in EAE. The durability of PLG-Ag-induced tolerance in the absence of KCs may be attributed to the distribution of PLG-Ags to LSECs, which demonstrated similar levels of PD-L1, PGE2, and T cell stimulatory ability. Collectively, these studies provide mechanistic support for the role of liver KCs and LSECs in Ag-specific tolerance for a biomaterial platform that is currently being evaluated in clinical trials.

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.