Lysyl Oxidase Regulates Epithelial Differentiation and Barrier Integrity in Eosinophilic Esophagitis.

BACKGROUND & AIMS: Epithelial disruption in eosinophilic esophagitis (EoE) encompasses both impaired differentiation and diminished barrier integrity. We have shown that lysyl oxidase (LOX), a collagen cross-linking enzyme, is up-regulated in the esophageal epithelium in EoE. However, the functional roles of LOX in the esophageal epithelium remains unknown. METHODS: We investigated roles for LOX in the human esophageal epithelium using 3-dimensional organoid and air-liquid interface cultures stimulated with interleukin (IL)13 to recapitulate the EoE inflammatory milieu, followed by single-cell RNA sequencing, quantitative reverse-transcription polymerase chain reaction, Western blot, histology, and functional analyses of barrier integrity. RESULTS: Single-cell RNA sequencing analysis on patient-derived organoids revealed that LOX was induced by IL13 in differentiated cells. LOX-overexpressing organoids showed suppressed basal and up-regulated differentiation markers. In addition, LOX overexpression enhanced junctional protein genes and transepithelial electrical resistance. LOX overexpression restored the impaired differentiation and barrier function, including in the setting of IL13 stimulation. Transcriptome analyses on LOX-overexpressing organoids identified an enriched bone morphogenetic protein (BMP) signaling pathway compared with wild-type organoids. In particular, LOX overexpression increased BMP2 and decreased the BMP antagonist follistatin. Finally, we found that BMP2 treatment restored the balance of basal and differentiated cells. CONCLUSIONS: Our data support a model whereby LOX exhibits noncanonical roles as a signaling molecule important for epithelial homeostasis in the setting of inflammation via activation of the BMP pathway in the esophagus. The LOX/BMP axis may be integral in esophageal epithelial differentiation and a promising target for future therapies.

Persistent esophageal changes after histologic remission in eosinophilic esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is characterized by persistent or relapsing allergic inflammation, and both clinical and histologic features of esophageal inflammation persist over time in most individuals. Mechanisms contributing to EoE relapse are not understood, and chronic EoE-directed therapy is therefore required to prevent long-term sequelae. OBJECTIVE: We investigated whether EoE patients in histologic remission have persistent dysregulation of esophageal gene expression. METHODS: Esophageal biopsy samples from 51 pediatric and 52 adult subjects with EoE in histopathologic remission (<15 eosinophils per high-power field [eos/hpf]) and control (48 pediatric and 167 adult) subjects from multiple institutions were subjected to molecular profiling by the EoE diagnostic panel, which comprises a set of 94 esophageal transcripts differentially expressed in active EoE. RESULTS: Defining remission as <15 eos/hpf, we identified 51 and 32 differentially expressed genes in pediatric and adult EoE patients compared to control individuals, respectively (false discovery rate < 0.05). Using the stringent definition of remission (0 eos/hpf), the adult and pediatric cohorts continued to have 18 and 25 differentially expressed genes (false discovery rate < 0.05). Among 6 shared genes between adults and children, CDH26 was upregulated in both children and adults; immunohistochemistry demonstrated increased cadherin 26 staining in the epithelium of EoE patients in remission compared to non-EoE controls. In the adult cohort, POSTN expression correlated with the endoscopic reference system score (Spearman r = 0.35, P = .011), specifically correlating with the rings' endoscopic reference system subscore (r = 0.53, P = .004). CONCLUSION: We have identified persistent EoE-associated esophageal gene expression in patients with disease in deep remission. These data suggest potential inflammation-induced epigenetic mechanisms may influence gene expression during remission in EoE and provide insight into possible mechanisms that underlie relapse in EoE.

Eosinophilic gastrointestinal disorders in patients with inborn errors of immunity: Data from the USIDNET registry.

Rationale: Eosinophilic gastrointestinal disorders (EGID), including eosinophilic esophagitis (EoE), are inflammatory disorders of the gastrointestinal mucosa mediated by complex immune mechanisms. Although there have been initial reports of EGID in patients with inborn errors of immunity (IEI), little is known about the presentation of EGID in immunodeficient individuals. Methods: We queried the U.S. Immunodeficiency Network (USIDNET) for patient records including the terms eosinophilic esophagitis, gastritis, enteritis, or colitis. We analyzed 74 patient records from the database, including diagnoses, demographics, infectious history, laboratory findings, genetic studies, therapeutic interventions, and clinical outcomes. Results: We examined 74 patient records. A total of 61 patients had isolated EoE, and 13 had distal gastrointestinal involvement consistent with EGID. The most common IEI were common variable immunodeficiency (43.2%), some form of combined immunodeficiency (21.6%), chronic granulomatous disease (8.1%), hyper-IgE syndrome (6.8%), and autoimmune lymphoproliferative syndrome (6.8%). The median age at presentation with IEI was 0.5 years (IQR 1.725, max 39 years) and 56.76% were male. Approximately 20% of the patients in the cohort received a hematopoietic stem cell transplantation for treatment of IEI, but the timing of the HSCT in relationship to the EGID diagnosis was unknown. Conclusions: Here, we report EGID in a diverse cohort of IEI patients, suggesting that both non-EoE EGID and EoE can be seen as comorbid conditions with a variety of IEI. Our data suggests that EGID may be more common in patients with IEI than would be expected based on estimates of EGID in the general population.

Posttreatment Gene Scores Support Histologic and Endoscopic Response Thresholds in Eosinophilic Esophagitis.

INTRODUCTION: The correlation between clinical and molecular treatment response thresholds in eosinophilic esophagitis (EoE) is not well understood. METHODS: We evaluated posttreatment EoE diagnostic panel gene expression profiles across histologic and endoscopic thresholds (EREFS) in a prospective adult EoE cohort. RESULTS: We observed a strong inverse correlation between posttreatment gene score and eosinophil count (R = -0.66; P < 0.001); biopsies with <15 eos/hpf had higher gene scores (≥425) vs those with ≥15 eos/hpf. Findings for EREFS were similar; EREFS ≤2 was associated with EoE diagnostic panel scores ≥395. DISCUSSION: Molecular signatures support the use of posttreatment response thresholds <15 eos/hpf and EREFS ≤2 in clinical practice and trials.

CD73+ Epithelial Progenitor Cells That Contribute to Homeostasis and Renewal Are Depleted in Eosinophilic Esophagitis.

BACKGROUND & AIMS: Although basal cell hyperplasia is a histologic hallmark of eosinophilic esophagitis (EoE), little is known about the capabilities of epithelial renewal and differentiation in the EoE inflammatory milieu. In murine esophageal epithelium, there are self-renewing and slowly proliferating basal stem-like cells characterized by concurrent expression of CD73 (5'-nucleotidase ecto) and CD104 (integrin ß4). Here, we investigated CD73+CD104+ cells within the basal population of human esophageal epithelium and clarified the biological significance of these cells in the EoE epithelium. METHODS: We performed flow cytometry on esophageal biopsy samples from EoE and non-EoE patients to determine the quantity of CD73+CD104+ cells in the epithelium. Simulating the EoE milieu we stimulated primary patient-derived and immortalized cell line-derived esophageal organoids with interleukin (IL)4 and IL13 and analyzed by flow cytometry, immunohistochemistry, and quantitative reverse-transcription polymerase chain reaction. We performed single-cell RNA sequencing on primary organoids in the setting of IL13 stimulation and evaluated the CD73+CD104+ population. We performed fluorescent-activated cell sorting to purify CD73+CD104+ and CD73- CD104+ populations and seeded these groups in organoid culture to evaluate the organoid formation rate and organoid size. We used RNA interference to knock down CD73 in esophageal organoids to evaluate organoid formation rates and size. We evaluated the effects of signal transducer and activator of transcription 6 (STAT6) signaling inhibition by RNA interference, a STAT6 inhibitor, AS1517499, as well as the proton pump inhibitor omeprazole. RESULTS: EoE patients showed decreased epithelial CD73+CD104+ cell content. IL4 and IL13 stimulation depleted this population in 3-dimensional organoids with a recapitulation of basal cell hyperplasia as corroborated by single-cell RNA sequencing of the organoids, which suggests depletion of CD73+CD104+ cells. The CD73+CD104+ population had enhanced organoid formation compared with the CD73-CD104+ population. Similarly, knock-down of CD73 resulted in decreased organoid formation rate. Genetic and pharmacologic inhibition of STAT6 prevented T helper 2 cytokine-induced depletion of CD73+CD104+ cells. Lastly, omeprazole treatment prevented the effects of IL4 and IL13 on the CD73+CD104+ population. CONCLUSIONS: This study addressed the role of CD73+CD104+ cells in epithelial renewal and homeostasis in the context of EoE. The depletion of the CD73+CD104+ self-renewal population by helper T cell 2 cytokines in EoE milieu may be perpetuating epithelial injury. Future therapies targeting epithelial restitution in EoE could decrease the need for immune modulation and steroid therapy.

Improvement in eosinophilic esophagitis when using dupilumab for other indications or compassionate use.

BACKGROUND: Dupilumab has been approved to treat atopic dermatitis, asthma, and nasal polyps and is in active clinical trials for the treatment of eosinophilic esophagitis (EoE). Given its shared immunopathology, we hypothesized that EoE symptoms and inflammation would improve when dupilumab therapy was used for other allergic indications. OBJECTIVE: To measure the clinical and histologic response in EoE to dupilumab when treating other atopic diseases. METHODS: We completed a retrospective chart review of all patients at Children's Hospital of Philadelphia and Rady Children Hospital who were prescribed dupilumab for atopic dermatitis, asthma, or nasal polyps and had a concomitant clinical diagnosis of EoE. Demographic information along with histology, symptom scores, medications, and diet information were collected. Response to dupilumab was evaluated. RESULTS: A total of 45 patients were identified. Of which, 11 patients were prescribed dupilumab for asthma, 27 for atopic dermatitis, 3 for nasal polyps, and 4 for compassionate use for EoE. There was no follow-up data for 8 patients. Follow-up histology was available for 26 patients: 22 of 26 had less than 6 eosinophils per high power field after the initiation of dupilumab with significant improvement (pre: 52.9 + 35.1 to post: 4.5 + 10.9 eosinophils/high power field, P < .005). A total of 28 patients had improvement of symptoms, with 24 patients reporting complete resolution of symptoms after dupilumab initiation. Reductions in EoE treatment medications (swallowed steroids, proton pump inhibitors) or expansion of diet occurred in 29 patients treated with dupilumab. CONCLUSION: Dupilumab therapy initiated for atopic disease effectively induces symptomatic and histologic remission of esophageal disease and reduces the need for EoE-directed therapy in patients with concomitant EoE.

Medical Management of Eosinophilic Esophagitis in Pediatric Patients.

Eosinophilic esophagitis is an immune-mediated allergic disease of the esophagus that affects pediatric patients of all ages. The diagnosis is made by esophagogastroduodenoscopy demonstrating eosinophilic infiltrate of the esophagus. Approaches to treatment involve proton pump inhibitors (PPIs), swallowed topical steroid preparations, as well as dietary elimination. In this review we discuss the evidence and efficacy of each of these approaches.

RNA sequencing identifies global transcriptional changes in peripheral CD4+ cells during active oesophagitis and following epicutaneous immunotherapy in eosinophilic oesophagitis.

OBJECTIVE: There are no disease-modifying therapies for the treatment of eosinophilic oesophagitis (EoE), which is driven by non-IgE-mediated allergic inflammation. A recent clinical trial of milk epicutaneous immunotherapy (EPIT) has shown initial promise, with 47% of treated EoE patients tolerating milk without recurrence of disease. Mechanisms of EPIT in EoE have not been studied in humans. Here, we identify transcriptional changes in the peripheral CD4+ T-cell compartment during active EoE and following EPIT. METHODS: RNA isolation, sequencing and integrative data analysis were performed on peripheral CD4+ T cells isolated from 15 of 20 patients enrolled in a clinical trial of EPIT for EoE. Gene expression changes in peripheral CD4+ T cells were examined during diet therapy and following trial of milk antigen EPIT. RESULTS: We identify 244 differentially expressed genes in peripheral blood CD4+ cells of EoE patients consuming versus those eliminating milk, and 129 DEGs in CD4+ cells were isolated after EPIT versus after placebo (FDR ≤ 0.05). Gene set enrichment analysis identifies enrichment of hallmark interferon-α and interferon-γ response pathways in peripheral CD4+ T cells from EoE patients during active disease on a milk-containing diet. We demonstrate overlap of this gene signature with the altered gene expression signature seen in EoE patient biopsy tissue. EPIT therapy response is associated with significant enrichment in pathways related to T-cell receptor signalling (P = 1.16 × 10-14), antigen presentation and costimulation, and cytokine signalling (P = 1.11 × 10-16), as well as upregulation of genes associated with regulatory T-cell function. CONCLUSIONS: EoE is associated with distinct global transcriptional changes in CD4+ T cells, one feature of which is an IFN response signature. Clinically favorable response to EPIT is likely multifactorial but is associated with a distinct transcriptional profile in peripheral CD4+ cells supporting the hypothesis that EPIT alters peripheral CD4+ responses in EoE patients.

Conserved IFN Signature between Adult and Pediatric Eosinophilic Esophagitis.

Eosinophilic esophagitis (EoE) is an allergic inflammatory disease of the esophagus that occurs in both children and adults. Previous studies of affected tissue from pediatric cohorts have identified prominent signatures of eosinophilia and type 2 inflammation. However, the details of the immune response in adults with EoE are still being elucidated. To determine whether EoE in adults shares inflammatory profiles with those observed in children, we performed RNA sequencing of paired human esophageal biopsies and blood samples from adults with EoE or gastroesophageal reflux disease. Unbiased analysis of differentially expressed genes in tissue revealed a strong IFN signature that was significantly enriched in EoE patients as compared with patients with gastroesophageal reflux disease. Both type I and type II IFN-responsive genes were upregulated in adult biopsies, but not in blood. A similar increase in expression of IFN gene sets was observed in pediatric EoE biopsies as compared with non-EoE samples, and in public pediatric and adult RNA-sequencing data. Finally, we found that human peripheral CD4+ T cells from children with EoE produce IFN-γ upon activation with EoE-causal allergens. Together, this work identifies a conserved IFN signature in pediatric and adult EoE, highlighting a role for non-type 2 inflammatory networks in the disease process in humans.

Toll-like receptor 2 stimulation augments esophageal barrier integrity.

BACKGROUND: Germline-encoded innate immune pattern recognition receptors (PRR) are expressed at epithelial surfaces and modulate epithelial defenses. Evidence suggests that stimulation of the Toll-like receptor (TLR) family of PRR may regulate epithelial barrier integrity by upregulating tight junction (TJ) complex protein expression, but it is not known whether this mechanism is utilized in esophageal epithelial cells. TJ complex proteins maintain intact barrier function and are dysregulated in atopic disorders including eosinophilic esophagitis. METHODS: Pattern recognition receptors expression was assessed in EoE and control primary esophageal epithelial cells, demonstrating robust expression of TLR2 and TLR3. The three-dimensional air-liquid interface culture (ALI) model was used to test whether TLR2 or TLR3 stimulation alters epithelial barrier function using an in vitro model of human epithelium. Transepithelial electrical resistance (TEER) and FITC-Dextran permeability were evaluated to assess membrane permeability. ALI cultures were evaluated by histology, immunohistochemistry, Western blotting, and chromatin immunoprecipitation (ChIP). RESULTS: TLR3 stimulation did not change TEER in the ALI model. TLR2 stimulation increased TEER (1.28- to 1.31-fold) and decreased paracellular permeability to FITC-Dextran, and this effect was abolished by treatment with anti-TLR2 blocking antibody. TJ complex proteins claudin-1 and zonula occludens-1 were upregulated following TLR2 stimulation, and ChIP assay demonstrated altered histone 4 acetyl binding at the TJP1 enhancer and CLDN1 enhancer and promoter following zymosan treatment, implying the occurrence of durable chromatin changes. CONCLUSIONS: Our findings implicate the TLR2 pathway as a potential regulator of esophageal epithelial barrier function and suggest that downstream chromatin modifications are associated with this effect.

Pediatric eosinophilic esophagitis: updates for the primary care setting.

PURPOSE OF REVIEW: Eosinophilic esophagitis (EoE) is a multifactorial, non-IgE-mediated inflammatory disorder of the esophagus and is the most common cause of food impaction in the pediatric population. The purpose of this review is to describe the current recommendations for diagnosis and management of EoE. RECENT FINDINGS: New data has associated EoE with other allergic disorders of the atopic march as well as several risk factors, which predispose to allergic conditions. A subset of patients with esophageal eosinophilia respond to proton pump inhibitor (PPI) therapy with a partial or complete resolution of esophageal eosinophilia. Therefore, some patients can be treated with PPI alone. If this is unsuccessful, dietary elimination and swallowed steroid therapy are recommended for long-term management. There is a growing appreciation that untreated esophageal inflammation can lead to complications of fibrosis and stricture formation. SUMMARY: The current review will focus on the diagnosis and management of EoE in the pediatric population. Identification and diagnosis of pediatric patients with EoE is critical to prevent long-term esophageal complications.

Complications Associated with Underweight Primary Immunodeficiency Patients: Prevalence and Associations Within the USIDNET Registry.

PURPOSE: The point prevalence of underweight status and obesity in primary immunodeficiency disease (PID) is unknown, despite the described associations between PID and weight loss and failure to thrive. The goal of this study is to estimate the prevalence of underweight status and obesity in PID patients and to investigate the associations between abnormal body weight and complications of PID. METHODS: Using the US Immunodeficiency Network (USIDNET), we performed a retrospective analysis of 653 pediatric (age 2 to 20 years) and 514 adult (age > 20) patient records with information on patient body mass index (BMI). Prevalence of underweight and obese status in PID patients was compared to data from the National Health and Nutrition Examination Survey (NHANES). RESULTS: After separating BMI data by year of entry to the database, we demonstrated that both adult and pediatric patients with PID had significantly higher prevalence of underweight patients in multiple years of analysis. Further examination of underweight patients by PID diagnosis revealed that underweight status in adults with CVID was associated with granulomatous disease as well as earlier age of CVID diagnosis. In the pediatric CVID cohort, underweight status was significantly associated with lymphopenia. Examination of obesity in pediatric and adult PID patients compared to NHANES database revealed only a single year when obesity in PID patients was significantly less prevalent. In other 2-year time intervals from 2005 to 2014, the prevalence of obesity was unchanged in children and adults. CONCLUSIONS: These results quantify the prevalence of underweight status in PID in a North American population and demonstrate that whether as a result of weight loss or poor weight gain, underweight status is more prevalent in the PID population than in the general US population. The prevalence of obesity in PID patients was similar to that seen in the general population. This highlights the need for continued education on the association of low weight and PID. CLINICAL TRIAL REGISTRATION: NCT01953016.

Elevated expression of activated TH2 cells and milk-specific TH2 cells in milk-induced eosinophilic esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is an allergic inflammatory disease that is triggered by food allergens and characterized by progressive esophageal dysfunction. Esophageal biopsy specimens are characterized by eosinophilia and expression of TH2 cytokines. OBJECTIVE: To ascertain whether TH2 cells can exist in the peripheral blood in patients with milk-induced EoE. METHODS: Peripheral blood mononuclear cells from 20 children with milk-induced EoE were collected during active EoE (EoE-A) while consuming milk and inactive EoE (EoE-I) while not consuming milk, and 8 healthy patients without EoE were used as controls. The samples were analyzed for T-cell phenotype, including intracellular cytokines before and after incubation with milk antigens and assessed by flow cytometry. RESULTS: We found a significant increase in CD4+ TH2 cells in the peripheral blood of patients with EoE-A compared with the controls. Furthermore, we observed a significant mean (SD) increase in the activation marker of CD154+ T cells (0.17% [0.047%]) in patients with EoE-A compared with control patients (0.034% [0.007%]) and EoE-I (0.025% [0.008]). These CD4+ T cells expressed significantly increase levels of TH2 cytokines (interleukins 4, 5, and 13) compared with the EoE-I and control groups. CD3+CD4+CD154+IL-5+ cells were significantly increased by milk antigens in both milk-induced EoE-A (0.050% [0.008%] to 0.079% [0.017%]) and EoE-I (0.0045% [0.002%] to 0.014% [0.008%]) compared with the controls (0.008% [0.003%] to 0.003% [0.001%]). CONCLUSION: Our findings indicate that in EoE peripheral T cells have specific activation to milk allergens.

Recurrent and Sustained Viral Infections in Primary Immunodeficiencies.

Viral infections are commonplace and often innocuous. Nevertheless, within the population of patients with primary immunodeficiencies (PIDDs), viral infections can be the feature that drives a diagnostic evaluation or can be the most significant morbidity for the patient. This review is focused on the viral complications of PIDDs. It will focus on respiratory viruses, the most common type of viral infection in the general population. Children and adults with an increased frequency or severity of respiratory viral infections are often referred for an immunologic evaluation. The classic teaching is to investigate humoral function in people with recurrent sinopulmonary infections, but this is often interpreted to mean recurrent bacterial infections. Recurrent or very severe viral infections may also be a harbinger of a primary immunodeficiency as well. This review will also cover persistent cutaneous viral infections, systemic infections, central nervous system infections, and gastrointestinal infections. In each case, the specific viral infections may drive a diagnostic evaluation that is specific for that type of virus. This review also discusses the management of these infections, which can become problematic in patients with PIDDs.

Plasma-derived MHC class II+ exosomes from tumor-bearing mice suppress tumor antigen-specific immune responses.

Tumor-specific immunosuppression is frequently observed in tumor-bearing hosts. Exosomes are nano-sized, endosomal-derived membrane vesicles secreted by most tumor and hematopoietic cells and have been shown to actively participate in immune regulation. We previously demonstrated that antigen-specific immunosuppressive exosomes could be isolated from the blood plasma of antigen-immunized mice. Here, we demonstrate that plasma-derived exosomes isolated from mice bearing OVA-expressing tumors were able to suppress OVA-specific immune responses in a mouse delayed-type hypersensitivity model. Enrichment of tumor-derived exosomes in the plasma of mice bearing subcutaneous melanoma was not detected using an exosome-tagging approach. Instead, depletion of MHC class II(+) vesicles from plasma-derived exosomes or using plasma-derived exosomes isolated from MHC class II-deficient mice resulted in significant abrogation of the suppressive effect. These results demonstrate that circulating host-derived, MHC class II(+) exosomes in tumor-bearing hosts are able to suppress the immune response specific to tumor antigens.

Dendritic cells transduced to express interleukin 4 reduce diabetes onset in both normoglycemic and prediabetic nonobese diabetic mice.

BACKGROUND: We and others have previously demonstrated that treatment with bone marrow derived DC genetically modified to express IL-4 reduce disease pathology in mouse models of collagen-induced arthritis and delayed-type hypersensitivity. Moreover, treatment of normoglycemic NOD mice with bone marrow derived DC, genetically modified to express interleukin 4 (IL-4), reduces the onset of hyperglycemia in a significant number of animals. However, the mechanism(s) through which DC expressing IL-4 function to prevent autoimmune diabetes and whether this treatment can reverse disease in pre-diabetic NOD mice are unknown. METHODOLOGY/PRINCIPAL FINDINGS: DC were generated from the bone marrow of NOD mice and transduced with adenoviral vectors encoding soluble murine IL-4 (DC/sIL-4), a membrane-bound IL-4 construct, or empty vector control. Female NOD mice were segregated into normoglycemic (<150 mg/dL) and prediabetic groups (between 150 and 250 mg/dL) on the basis of blood glucose measurements, and randomized for adoptive transfer of 10(6) DC via a single i.v. injection. A single injection of DC/sIL-4, when administered to normoglycemic 12-week old NOD mice, significantly reduced the number of mice that developed diabetes. Furthermore, DC/sIL-4, but not control DC, decreased the number of mice progressing to diabetes when given to prediabetic NOD mice 12-16 weeks of age. DC/sIL-4 treatment also significantly reduced islet mononuclear infiltration and increased the expression of FoxP3 in the pancreatic lymph nodes of a subset of treated animals. Furthermore, DC/sIL-4 treatment altered the antigen-specific Th2:Th1 cytokine profiles as determined by ELISPOT of splenocytes in treated animals. CONCLUSIONS: Adoptive transfer of DC transduced to express IL-4 into both normoglycemic and prediabetic NOD mice is an effective treatment for T1D.

B7-1/2, but not PD-L1/2 molecules, are required on IL-10-treated tolerogenic DC and DC-derived exosomes for in vivo function.

Costimulatory molecules, such as B7-1/2 and PD-L1/2 play an important role in the function of APC. The regulation of the surface levels of costimulatory molecules is one mechanism by which APC maintain the balance between tolerance and immunity. We examined the contributions of B7-1/2 and PD-L1/2 to the function of IL-10-treated, immunosuppressive DC as well as therapeutic exosomes derived from these DC. IL-10 treatment of DC significantly downregulated surface expression of MHC II, B7-1, B7-2, and decreased levels of MHC I and PD-L2. IL-10 treatment of DC resulted in a modified costimulatory profile of DC-secreted exosomes with a reduction in B7-1, PD-L1 and PD-L2. We further demonstrate that absence of B7-1 or B7-2 on donor DC results in a loss of ability of IL-10-treated DC and their exosomes to suppress the delayed-type hypersensitivity response, whereas IL-10-treated DC deficient in PD-L1/2 as well as their secreted exosomes retained the ability to suppress delayed-type hypersensitivity responses. We conclude that B7-1 and B7-2, but not PD-L1 and PD-L2, on IL-10-treated DC and DC-derived exosomes play a critical role in immunosuppressive functions of both DC and exosomes.

Therapeutic effect of exosomes from indoleamine 2,3-dioxygenase-positive dendritic cells in collagen-induced arthritis and delayed-type hypersensitivity disease models.

OBJECTIVE: We have demonstrated previously that dendritic cells (DCs) modified with immunosuppressive cytokines, and exosomes derived from DCs can suppress the onset of murine collagen-induced arthritis (CIA) and reduce the severity of established arthritis. Indoleamine 2,3-dioxygenase (IDO) is a tryptophan-degrading enzyme that is important for immune regulation and tolerance maintenance. DCs expressing functional IDO can inhibit T cells by depleting them of essential tryptophan and/or by producing toxic metabolites, as well as by generating Treg cells. This study was undertaken to examine the immunosuppressive effects of bone marrow (BM)-derived DCs genetically modified to express IDO, and of exosomes derived from IDO-positive DCs. METHODS: BM-derived DCs were adenovirally transduced with IDO or CTLA-4Ig (an inducer of IDO), and the resulting DCs and exosomes were tested for their immunosuppressive ability in the CIA and delayed-type hypersensitivity (DTH) murine models. RESULTS: Both DCs and exosomes derived from DCs overexpressing IDO had an antiinflammatory effect in CIA and DTH murine models. The suppressive effects were partially dependent on B7 costimulatory molecules. In addition, gene transfer of CTLA-4Ig to DCs resulted in induction of IDO in the DCs and in exosomes able to reduce inflammation in an IDO-dependent manner. CONCLUSION: These results demonstrate that both IDO-expressing DCs and DC-derived exosomes are immunosuppressive and antiinflammatory, and are able to reverse established arthritis. Therefore, exosomes from IDO-positive DCs may represent a novel therapy for rheumatoid arthritis.