Expansion Of Eosinophils Research Articles

Single-cell proteomics and transcriptomics capture eosinophil development and identify the role of IL-5 in their lineage transit amplification

The activities, ontogeny, and mechanisms of lineage expansion of eosinophils are less well resolved than those of other immune cells, despite the use of biological therapies targeting the eosinophilia-promoting cytokine interleukin (IL)-5 or its receptor, IL-5Rα. We combined single-cell proteomics and transcriptomics and generated transgenic IL-5Rα reporter mice to revisit eosinophilopoiesis. We reconciled human and murine eosinophilopoiesis and provided extensive cell-surface immunophenotyping and transcriptomes at different stages along the continuum of eosinophil maturation. We used these resources to show that IL-5 promoted eosinophil-lineage expansion via transit amplification, while its deletion or neutralization did not compromise eosinophil maturation. Informed from our resources, we also showed that interferon response factor-8, considered an essential promoter of myelopoiesis, was not intrinsically required for eosinophilopoiesis. This work hence provides resources, methods, and insights for understanding eosinophil ontogeny, the effects of current precision therapeutics, and the regulation of eosinophil development and numbers in health and disease.

Expansion of distinct peripheral blood myeloid cell subpopulations in patients with rheumatoid arthritis-associated interstitial lung disease

ObjectivesInterstitial lung disease (ILD) is associated with significant mortality in rheumatoid arthritis (RA) patients with key cellular players remaining largely unknown. This study aimed to characterize inflammatory and myeloid derived suppressor cell (MDSC) subpopulations in RA-ILD as compared to RA, idiopathic pulmonary fibrosis (IPF) without autoimmunity, and controls. MethodsPeripheral blood was collected from patients with RA, RA-ILD, IPF, and controls (N = 60, 15/cohort). Myeloid cell subpopulations were identified phenotypically by flow cytometry using the following markers:CD45,CD3,CD19,CD56,CD11b,HLA-DR,CD14,CD16, CD15,CD125,CD33. Functionality of subsets were identified with intracellular arginase-1 (Arg-1) and inducible nitric oxide synthase (iNOS) expression. ResultsThere was increased intermediate (CD14++CD16+) and nonclassical (CD14+/-CD16++) and decreased classical (CD14++CD16-) monocytes in RA, RA-ILD, and IPF vs. control. Intermediate monocytes were higher and classical monocytes were lower in RA-ILD vs. RA but not IPF. Monocytic (m)MDSCs were higher in RA-ILD vs. control and RA but not IPF. Granulocytic (g)MDSCs did not significantly differ. In contrast, neutrophils were increased in IPF and RA-ILD patients with elevated expression of Arg-1 sharing similar dimensional clustering pattern. Eosinophils were increased in RA-ILD vs. controls, RA and IPF. Across cohorts, iNOS was decreased in intermediate/nonclassical monocytes but increased in mMDSCs vs. classical monocytes. In RA-ILD, iNOS positive mMDSCs were increased versus classic monocytes. ConclusionsMyeloid cell subpopulations are significantly modulated in RA-ILD patients with expansion of CD16+ monocytes, mMDSCs, and neutrophils, a phenotypic profile more aligned with IPF than other RA patients. Eosinophil expansion was unique to RA-ILD, potentially facilitating disease pathogenesis and providing a future therapeutic target.

The challenge of diagnosing and classifying eosinophilia and eosinophil disorders: A review.

Eosinophilia is a feature of multiple conditions, both hematologic and non-hematologic, and may be associated with organ damage. The pathogenesis of eosinophilia can follow two distinct pathways. Primary eosinophilia is caused by a cell-intrinsic mechanism originating from clonal expansion of eosinophils through acquisition of a somatic mutation, such as FIP1L1-PDGFRA. In recent years, great progress has been made in the field of pathogenesis and molecularly targeted therapy of neoplastic eosinophilia. The diagnostic procedure should include, among other things, morphologic analysis of blood and bone marrow samples, cytogenetics and fluorescence in situ-hybridization tests to detect evidence of an acute or chronic myeloid or lymphoid disorder. Secondary eosinophilia follows a cell-extrinsic mechanism as a response to exogenous cytokines. In most clinical cases, peripheral blood eosinophilia is reactive and typically associated with non-hematological disorders such as infections, allergic conditions, connective tissue disorders, vasculitis, malignancy, or endocrinopathies. Nonetheless, the cause of most cases of hypereosinophilic syndrome remains unknown. In this article, we present a short review focused on differential diagnosis of eosinophilia and eosinophilic disorders. The diagnosis of eosinophilia is a challenge for physicians; thus this review may be useful in clinical practice.

IL-5-producing CD4+ Tcells and eosinophils cooperate to enhance response to immune checkpoint blockade in breast cancer.

Immune checkpoint blockade (ICB) has heralded a new era in cancer therapy. Research into the mechanisms underlying response to ICB has predominantly focused on Tcells; however, effective immune responses require tightly regulated crosstalk between innate and adaptive immune cells. Here, we combine unbiased analysis of blood and tumors from metastatic breast cancer patients treated with ICB with mechanistic studies in mouse models of breast cancer. We observe an increase in systemic and intratumoral eosinophils in patients and mice responding to ICB treatment. Mechanistically, ICB increased IL-5 production by CD4+ Tcells, stimulating elevated eosinophil production from the bone marrow, leading to systemic eosinophil expansion. Additional induction of IL-33 by ICB-cisplatin combination or recombinant IL-33 promotes intratumoral eosinophil infiltration and eosinophil-dependent CD8+ Tcell activation to enhance ICB response. This work demonstrates the critical role of eosinophils in ICB response and provides proof-of-principle for eosinophil engagement to enhance ICB efficacy.

ASYMPTOMATIC EOSINOPHILIA WITH REACTIVE HYPERGAMMAGLOBULINEMIA

<h3>Introduction</h3> Eosinophilia is commonly reactive (secondary eosinophilia) involving polyclonal expansion of eosinophils due to infection, atopic disease, drug allergy, or autoimmune conditions. More rarely, primary eosinophilia occurs from clonal expansion of eosinophils from underlying hematologic malignancies or idiopathic hypereosinophilic syndrome. <h3>Case Description</h3> A 72 year old male who emigrated from Ghana 19 years prior was referred to allergy clinic for allergy testing for eosinophilia of at least 2 weeks (AEC 1900 eosinophils/μL) detected on routine blood work. He was asymptomatic. Physical exam was normal. Initial workup revealed improving eosinophilia (AEC 790), lymphocytosis, and hypergammaglobulinemia (IgG 2064 g/L, IgE 1894 g/L, IgA 461 g/L). SPEP showed polyclonal gammopathy. Immunophenotyping showed normal B/T cell populations. RAST testing, tryptase, Vitamin B12, HIV, HTLV, ANCA, MPO, Strongyloides Ab, and CRP were negative. Further history revealed a diarrheal illness in Ghana a few months prior. Stool O&P from his initial primary care appointment was positive for few <i>Blastocystis hominis</i>. Repeat testing 3 months later showed continued improvement of eosinophilia (AEC 670) and persistent though improving hypergammaglobulinemia. <h3>Discussion</h3> Eosinophilia may be detected in asymptomatic patients and requires a broad differential diagnosis for underlying cause. Careful history, physical examination, and directed workup is key. Travel history is particularly important in travelers and immigrants. While the pathogenicity of <i>Blastocystic hominis</i> is controversial, the patient's reported diarrheal illness without other symptoms and otherwise negative work up makes parasitic gastroenteritis with reactive hypergammaglobulinemia the most likely etiology of this patient's asymptomatic eosinophilia.

Massive eosinophilia despite severe aplastic anemia.

A 47-year-old nonsmoking man developed very severe aplastic anemia (AA) (hemoglobin 56 g/L, neutrophils 110/μl, eosinophils 0/μl, platelets 4000/μl) with fatty marrow (Figure 1A: hematoxylin–eosin stain, ×4 objective). He had a history of bronchial asthma for 3 years and had been treated with inhaled corticosteroid in combination with long-acting β2-agonist (budesonide/formoterol fumarate). In addition, he had developed eosinophilic pneumonia requiring systemic administration of prednisolone (<30 mg/day) twice in the last 1.5 years. His family history was not significant for any serious diseases. Treatment with antithymocyte globulin, eltrombopag olamine, and cyclosporine (CsA) (500 mg/day) eliminated the need for blood transfusions and the CsA dose was gradually reduced. While pancytopenia continued (hemoglobin <97 g/L, neutrophils <1400/μl, platelets <30,000/μl), eosinophilia (>500/μl) appeared 17 months after the start of treatment. This increased to 4550/μl in 4 months after discontinuation of CsA treatment at 33 months. In addition, he presented with a rash with purpura on the legs, for which prednisolone (<20 mg/day) was not effective. Bone marrow examination showed mild hypocellular marrow with eosinophil expansion (43.8%) (Figure 1B: hematoxylin–eosin stain, ×4 objective; Figure 1C: hematoxylin–eosin stain, ×40 objective; Figure 1D: direct Fast Scarlet stain, ×40 objective). Increased blasts and significant dysplasia were not observed. G-banding and fluorescence in situ hybridization for the FIP1L1–PDGFRA re-arrangement detected no chromosomal aberrations. Moreover, skin biopsy revealed eosinophilic vasculitis and panniculitis, compatible with eosinophilic granulomatosis with polyangiitis (Figure 1E: hematoxylin–eosin stain, ×20 objective; Figure 1F: direct Fast Scarlet stain, ×40 objective). After re-administration of CsA (150 mg/day), eosinophilia and skin lesions disappeared in 5 weeks. This case indicates that massive reactive eosinophilia can occur even in AA patients with eosinophil-associated diseases, especially during dose reduction, or after the discontinuation of CsA. None. The authors declare that there is no conflict of interest. Aya Takahashi and Tsutomu Shinohara designed the research, drafted the manuscript, and created the figure. Aya Takahashi performed the skin biopsy. Yoshihito Iwahara, Aya Takahashi, Hisanori Machida, Keishi Naruse, Eiji Takeuchi, and Tsutomu Shinohara analyzed the data. Keishi Naruse contributed to pathological assessment. All authors revised the manuscript critically and approved the final manuscript.

Beyond Il-5: Metabolic Reprogramming and Stromal Support Are Prerequisite for Generation and Survival of Long-Lived Eosinophil.

Eosinophils play surprisingly diverse roles in health and disease. Accordingly, we have now begun to appreciate the scope of the functional and phenotypic heterogeneity and plasticity of these cells. Along with tissue-recruited subsets during inflammation, there are tissue resident eosinophil phenotypes with potentially longer life spans and less dependency on IL-5 for survival. Current models to study murine eosinophils ex vivo rely on IL-5-sustained expansion of eosinophils from bone marrow hematopoietic progenitors. Although it does generate eosinophils (bmEos) in high purity, such systems are short-lived (14 days on average) and depend on IL-5. In this report, we present a novel method of differentiating large numbers of pure bone marrow-derived eosinophils with a long-lived phenotype (llEos) (40 days on average) that require IL-5 for initial differentiation, but not for subsequent survival. We identified two key factors in the development of llEos: metabolic adaptation and reprogramming induced by suppressed nutrient intake during active differentiation (from Day 7 of culture), and interaction with IL-5-primed stromal cells for the remainder of the protocol. This regimen results in a higher yield and viability of mature eosinophils. Phenotypically, llEos develop as Siglec-F(+)Ly6G(+) cells transitioning to Siglec-F(+) only, and exhibit typical eosinophil features with red eosin granular staining, as well as the ability to chemotax to eotaxin Ccl11 and process fibrinogen. This culture system requires less reagent input and allows us to study eosinophils long-term, which is a significant improvement over IL-5-driven differentiation protocols. Moreover, it provides important insights into factors governing eosinophil plasticity and the ability to assume long-lived IL-5-independent phenotypes.

In Vivo Eosinophil Expansion Using Gene Transfer by Electroporation.

Eosinophils are differentiated in the bone marrow and transit through the blood circulation to home into tissues primarily under the regulation of IL-5. Because the number of eosinophils in the peripheral blood is relatively low under normal conditions, in vivo functional studies of eosinophils remain extremely difficult. Increasing their numbers in vivo might be useful for assessing eosinophil activities during parasite infections, allergic inflammation, and so on. Here, we provide a method for eosinophil expansion using IL-5 gene transfer by electroporation in vivo.

Abstract 13911: Interleukin-5-induced Eosinophil Population Improves Cardiac Function After Myocardial Infarction

Background: Eosinophils have been commonly recognized as one of the major participants in helminth infection and allergic diseases. Recent studies suggest that these innate immune cells mediate tissue repairs after muscle, hepatic, or endometrial injuries. Yet, the precise role of eosinophils in myocardial infarction (MI) remains unclear. Interleukin (IL)-5 is the most important cytokines that are responsible for the development, activation, and survival of eosinophils. Here, we report a role of IL-5 in infarcted heart. Methods and Results: MI was induced by permanent ligation of left anterior descending coronary artery in wild-type C57BL/6 mice. Western blot show that infarcted heart IL-5 expression is increased by 2.35-fold (P&lt;0.01) higher than their expression in the heart of sham mice at day 5 after surgery. External supply of recombinant mouse IL-5 (100 μg/kg/day for 3 days) reduces the infarct size (by 13.38%, P&lt;0.01), increases ejection fraction (from 32.41% to 43.93%, P&lt;0.01), and increases angiogenesis (CD31 area from 3.35% to 4.14%, P=0.03) in the peri-infarct zone. An expansion of eosinophils is observed in both the peripheral blood and infarcted myocardium after IL-5 administration. Pharmacological depletion of eosinophils by TRFK5 pretreatment mutes the beneficial effects of IL-5 in MI mice. Mechanistic studies also demonstrate that IL-5 increases the accumulation of M2 macrophages in infarcted myocardium at day 7 post-MI. In vitro co-culture experiments reveal that eosinophils shift bone marrow-derived macrophage polarization towards the M2 phenotypes. This effect is abolished by IL-4 neutralizing antibody, but not IL-10 or IL-13 neutralization. Western blot analyses show that eosinophils promote the macrophage downstream STAT6 phosphorylation. Conclusions: We demonstrate here that IL-5 facilitates the recovery of post-MI cardiac function by promoting eosinophils accumulation and subsequent polarization of M2 macrophages via the IL-4/STAT6 axis.

Benralizumab for severe DRESS in two COVID-19 patients

Drug rash with eosinophilia and systemic symptoms (DRESS) is a rare severe hypersensitivity reaction that clinically manifests with exanthema, facial edema, enlarged lymph nodes, fever, and organ damage at variable degrees.1 Eosinophil expansion in blood is a hallmark of DRESS, and eosinophil tissue infiltration a main contributor to the observed organ damage and dysfunction.2 Although high-dose systemic glucocorticoids have not been evaluated in randomized clinical trials, they are currently the first-line therapy for DRESS with organ involvement.

Interleukin 33 Triggers Early Eosinophil-Dependent Events Leading to Metaplasia in a Chronic Model of Gastritis-Prone Mice

Interleukin (IL)33/IL1F11 is an important mediator for the development of type 2 T-helper cell (Th2)-driven inflammatory disorders and has also been implicated in the pathogenesis of gastrointestinal (GI)-related cancers, including gastric carcinoma. We therefore sought to mechanistically determine IL33's potential role as a critical factor linking chronic inflammation and gastric carcinogenesis using gastritis-prone SAMP1/YitFc (SAMP) mice. SAMP and (parental control) AKR mice were assessed for baseline gastritis and progression to metaplasia. Expression/localization of IL33 and its receptor, ST2/IL1R4, were characterized in corpus tissues, and activation and neutralization studies were both performed targeting the IL33/ST2 axis. Dissection of immune pathways leading to metaplasia was evaluated, including eosinophil depletion studies using anti-IL5/anti-CCR3 treatment. Progressive gastritis and, ultimately, intestinalized spasmolytic polypeptide-expressing metaplasia (SPEM) was detected in SAMP stomachs, which was absent in AKR but could be moderately induced with exogenous, recombinant IL33. Robust peripheral (bone marrow) expansion of eosinophils and local recruitment of both eosinophils and IL33-expressing M2 macrophages into corpus tissues were evident in SAMP. Interestingly, IL33 blockade did not affect bone marrow-derived expansion and local infiltration of eosinophils, but markedly decreased M2 macrophages and SPEM features, while eosinophil depletion caused a significant reduction in both local IL33-producing M2 macrophages and SPEM in SAMP. IL33 promotes metaplasia and the sequelae of eosinophil-dependent downstream infiltration of IL33-producing M2 macrophages leading to intestinalized SPEM in SAMP, suggesting that IL33 represents a critical link between chronic gastritis and intestinalizing metaplasia that may serve as a potential therapeutic target for preneoplastic conditions of the GI tract.

Eosinophilia Associated With CD3-CD4+ T Cells: Characterization and Outcome of a Single-Center Cohort of 26 Patients.

Background: Lymphocytic variant hypereosinophilic syndrome is characterized by marked over-production of eosinophilopoietic factor(s) by dysregulated T cells leading to eosinophil expansion. In most cases, these T cells are clonal and express a CD3−CD4+ phenotype. As this is a rare disorder, presenting manifestations, disease course, treatment responses, and outcome are not well-characterized.Materials and Methods: In this retrospective single-center observational study, we reviewed medical files of all patients with persistent hypereosinophilia seen between 1994 and 2019 in whom CD3−CD4+ T cells were detected. Data collection included clinical and biological findings at presentation, treatment responses, disease course, and serial CD3−CD4+ T cell counts.Results: Our cohort comprises 26 patients, including 2 with hypereosinophilia of undetermined significance. All 24 symptomatic patients had cutaneous lesions and/or angioedema, and fasciitis was present in several cases. The aberrant T cell subset represented 2% or less total lymphocytes in 11 subjects. TCR gene rearrangement patterns on whole blood were polyclonal in these cases, while they all had serum CCL17/TARC levels above 1,500 pg/ml. Disease manifestations were mild and did not require maintenance therapy in roughly one third of the cohort, while two thirds required long-term oral corticosteroids and/or second-line agents. Among these, interferon-alpha was the most effective treatment option with a response observed in 8/8 patients, one of whom was cured of disease. Treatment had to be interrupted in most cases however due to poor tolerance and/or development of secondary resistance. Anti-interleukin-5 antibodies reduced blood eosinophilia in 5/5 patients, but clinical responses were disappointing. A sub-group of 5 patients had severe treatment-refractory disease, and experienced significant disease- and treatment-related morbidity and mortality, including progression to T cell lymphoma in three.Conclusions: This retrospective longitudinal analysis of the largest monocentric cohort of CD3−CD4+ T cell associated lymphocytic variant hypereosinophilic syndrome published so far provides clinicians confronted with this rare disorder with relevant new data on patient presentation and outcome that should help tailor therapy and follow-up to different levels of disease severity. It highlights the need for novel therapeutic options, especially for the subset of patients with severe treatment-refractory disease. Future research efforts should be made toward understanding CD3−CD4+ T cell biology in order to develop new treatments that target primary pathogenic mechanisms.

Anti-inflammatory and immune-regulatory cytokines in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by a failure of spontaneous resolution of inflammation. Although the pro-inflammatory cytokines and mediators that trigger RA have been the focus of intense investigations, the regulatory and anti-inflammatory cytokines responsible for the suppression and resolution of disease in a context-dependent manner have been less well characterized. However, knowledge of the pathways that control the suppression and resolution of inflammation in RA is clinically relevant and conceptually important for understanding the pathophysiology of the disease and for the development of treatments that enable long-term remission. Cytokine-mediated processes such as the activation of T helper 2 cells by IL-4 and IL-13, the resolution of inflammation by IL-9, IL-5-induced eosinophil expansion, IL-33-mediated macrophage polarization, the production of IL-10 by regulatory B cells and IL-27-mediated suppression of lymphoid follicle formation are all involved in governing the regulation and resolution of inflammation in RA. By better understanding these immune-regulatory signalling pathways, new therapeutic strategies for RA can be envisioned that aim to balance and resolve, rather than suppress, inflammation.

Matrix protein Tenascin-C expands and reversibly blocks maturation of eosinophil progenitors

Abstract While eosinophil depletion is a sought after strategy in treating allergic disease, little is known about the local tissue factors regulating eosinophils. In disease, eosinophils encounter provisional extracellular matrix (ECM) glycoproteins such as Tenascin-C (TNC), which strongly correlates with eosinophil expansion in tissues. While restricted in healthy adult lungs, TNC is a hematopoietic niche component in bone marrow stroma and is expressed de novo during wound healing or in pathologic epithelial remodeling in asthma. RNA-Seq shows that exposing naïve murine eosinophils to TNC upregulates immaturity markers (CD34, CD117, and Sca-1) and suppresses IL-5Rα. Thus, we hypothesized that TNC represents a factor in the provisional allergic tissue microenvironment that could support in situ eosinophil progenitor expansion. In murine bone marrow-derived cultures, TNC: 1) 3-fold expanded the available Lin−Sca1+ early precursor pool; 2) downregulated IL-5Rα expression on Lin− CD45+ c-kit+ cells during the eosinophil lineage commitment phase; 3) served as a reversible eosinophil maturation block, as TNC withdrawal rescued maturation and increased final eosinophil yield. Moreover, TNC knockout mice lack in situ lung expansion of Lin− c-kit+ CD34+ common myeloid progenitors and Lin− Siglec-F+ Sca-1+ cells in an allergic inflammation model as well as exhibit accelerated lung eosinophil maturation ex vivo. Adding TNC to lung homogenates cultured in IL-5 ex vivo suppressed eosinophil maturation in a manner consistent with TNC block of eosinophil maturation in bone marrow-derived cultures. Together, our results stress the local tissue factor potential to promote in situ expansion and eosinophil persistence in allergic disease.

Aberrant innate immune activation facilitates EcoHIV evasion from vaccine-induced protection

Abstract Aberrant innate immune response during acute phase of infection causes persistent viral infection through suppression of T-cell function. Understanding the impact of this aberrant innate immune activation on vaccine-conferred protection is critical regarding development of effective vaccine against chronic disease. Here, using EcoHIV mice model and a novel DC-targeting DNA vaccine that elicited high frequencies of GAG-specific, broadly reactive, and polyfunctional cytotoxic CD8+ T cells, we show that aberrant innate immune activation at early stage of infection rendered EcoHIV resistant to vaccine protection by suppressing T cells proliferation and function. We found that despite high frequencies of p24-specific IFN-γ+CD8+ T cells elicited by vaccination, EcoHIV have fallen short of effective recall of antiviral T cell immunity induced by prophylactic vaccination in vivo. Provirus DNA was readily detected in PBMC and spleen in all of the infected mice without detectable resistant mutations. Compared to non-immunized mice, provirus copies in immunized mice were decreased only at 1 and 2 weeks post viral inoculation without further decrease over the following weeks. Further investigation revealed that EcoHIV infected multiple DC subsets, and CD11b+ myeloid derived cells within 7 dpi, and induced quick expansion of eosinophils and monocytic cells in spleen, which peaked at 14 dpi and remained high at 21 dpi. The expansion of monocytic cells was associated with down-regulation of CD80 and CD86, up-regulation of PD-L1/L2 on multiple dendritic cell subsets, PD-1+ and Tim+ CD8 T cells, compromised capacity of DCs in stimulating CD4 and CD8 T cells proliferation, and suppressed viral-specific CD8 T cells proliferation in vitro.

The lung hematopoietic niche supports bone marrow-independent hematopoiesis and contributes to local eosinophil expansion during allergic inflammation.

Abstract Bone marrow is classically viewed as the major source of differentiated leukocytes infiltrating tissues from circulation. Recent evidence shows that the lung can potentially function as a hematopoietic organ on its own. This is a novel concept and tissue factors driving in situ leukocyte production are not yet well understood. In naïve murine lungs, we detected a small population of Lin−CD34+c-Kit+ common myeloid progenitors (CMPs) by flow cytometry and single cell RNA-seq analysis. Males had 0.087±0.06% CMPs, while females had a larger population of 0.18±0.08%, out of CD45+ cells. In a 3 challenge in vivo ovalbumin model of allergic inflammation, we observed a six-fold expansion of CMPs in the lung tissue and the appearance of Siglec-F+CD34+IL-5Rα+ eosinophil progenitors (EoPs) (1.505±0.6% of CD45+). To illustrate the hematopoietic potential of the lung independent of bone marrow recruitment, we cultured naïve lung single cell suspensions ex vivo in presence of SCF, FLT3 and IL-5. This was sufficient to yield up to 20% mature eosinophils, which is comparable to tissue eosinophil levels in models of allergic inflammation. We further tested whether Tenascin-C (TNC), a known component of bone marrow hematopoiesis, may equally support the hematopoietic niche in the lung. TNC is a provisional matrix glycoprotein that strongly associates with epithelial remodeling and eosinophil accumulation in asthma. TNC−/− mice had a significant defect in CMP and EoP expansion in a murine model of asthma and ex vivo IL-5 lung cultures. Administration of recombinant TNC rescued normal lung eosinophilopoiesis. These results suggest the existence and significant potential of the lung hematopoietic niche to supply effector cells during inflammation.

Targeting the Interleukin-5 Pathway for Treatment of Eosinophilic Conditions Other than Asthma.

Improved understanding of the contribution of eosinophils to various chronic inflammatory conditions, most notably allergic asthma, has encouraged development of monoclonal antibodies specifically targeting mediators and surface receptors involved in eosinophil expansion and activation. The pivotal role of interleukin-5 (IL-5) in eosinophil biology, its high specificity for this leukocyte subset, and its involvement in the majority of eosinophilic conditions make it a very enticing target for treatment of eosinophil-mediated disorders. Two types of antibodies have been developed to target eosinophils: antibodies against IL-5 (mepolizumab and reslizumab), and an antibody against the IL-5-receptor-alpha-chain (IL-5Rα) (benralizumab). Both types of antibodies prevent IL-5 from engaging its receptor and in addition, anti-IL-5Rα antibodies induce target-cell lysis. They have been shown to reduce circulating eosinophil counts rapidly in humans with various disorders. Herein, a brief overview of the role of IL-5 in eosinophil biology will be presented, followed by a description of the development and characteristics of antibodies targeting IL-5 or its receptor. Results of clinical trials evaluating the efficacy and safety of these new antibodies in diseases (other than eosinophilic asthma) with prominent tissue eosinophilia are reviewed, followed by safety considerations and potential future applications.

Pharmacokinetic/pharmacodynamic profile of reslizumab in asthma

ABSTRACTIntroduction: Allergic asthma is a Th2-driven inflammatory process characterized by the infiltration of eosinophils into the airways. IL-5 is a key trigger for eosinophil expansion and release from the bone marrow and plays a crucial role in the entire life span of eosinophils from differentiation to maturation and survival. IL-5 can be considered among the most obvious targets to selectively inhibit eosinophilic airway inflammation.Areas covered: The preclinical and clinical development of reslizumab, a humanized mAb against IL-5 that has been developed to block IL-5 bioactivity and reduce biologically available IL-5, are described with a particular focus on its pharmacodynamics (PK)/pharmacokinetic (PD) profile.Expert opinion: Although pivotal trials have documented that reslizumab can be recommended as add-on therapy for the treatment of patients with severe eosinophilic asthma, there is still important information that is lacking and some PK and PD properties of reslizumab are still not fully understood.

In Vivo Expansion of Activated Foxp3+ Regulatory T Cells and Establishment of a Type 2 Immune Response upon IL-33 Treatment Protect against Experimental Arthritis.

IL-33 is strongly involved in several inflammatory and autoimmune disorders with both pro- and anti-inflammatory properties. However, its contribution to chronic autoimmune inflammation, such as rheumatoid arthritis, is ill defined and probably requires tight regulation. In this study, we aimed at deciphering the complex role of IL-33 in a model of rheumatoid arthritis, namely, collagen-induced arthritis (CIA). We report that repeated injections of IL-33 during induction (early) and during development (late) of CIA strongly suppressed clinical and histological signs of arthritis. In contrast, a late IL-33 injection had no effect. The cellular mechanism involved in protection was related to an enhanced type 2 immune response, including the expansion of eosinophils, Th2 cells, and type 2 innate lymphoid cells, associated with an increase in type 2 cytokine levels in the serum of IL-33-treated mice. Moreover, our work strongly highlights the interplay between IL-33 and regulatory T cells (Tregs), demonstrated by the dramatic in vivo increase in Treg frequencies after IL-33 treatment of CIA. More importantly, Tregs from IL-33-treated mice displayed enhanced capacities to suppress IFN-γ production by effector T cells, suggesting that IL-33 not only favors Treg proliferation but also enhances their immunosuppressive properties. In concordance with these observations, we found that IL-33 induced the emergence of a CD39(high) Treg population in a ST2L-dependent manner. Our findings reveal a powerful anti-inflammatory mechanism by which IL-33 administration inhibits arthritis development.

Helminth Products Protect against Autoimmunity via Innate Type 2 Cytokines IL-5 and IL-33, Which Promote Eosinophilia.

Epidemiologic studies in humans have demonstrated that infection with helminth parasites is associated with a reduced risk of developing autoimmune diseases. Mechanistic studies in mice have linked the protective effect of helminths on autoimmunity to the suppressive activity of helminth-induced regulatory T cells (Tregs) or Th2 cells. In this study, we demonstrate that treatment of mice with Fasciola hepatica excretory-secretory products (FHES) attenuated the clinical signs of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Protection was associated with a significant reduction in the infiltration of pathogenic Th1 and Th17 cells into the brain. Although FHES enhanced anti-inflammatory cytokine and Th2 responses, protection against EAE was independent of IL-4, IL-10, and Tregs. However, administration of FHES induced production of the type 2 cytokines IL-33 and IL-5, which promoted accumulation of eosinophils. FHES-induced expansion of eosinophils and protection against EAE was lost in IL-33(-/-) mice and upon neutralization of IL-5. Furthermore, transfer of FHES-induced or IL-33-induced eosinophils conferred protection against EAE. In addition, treatment of mice with recombinant IL-33 attenuated autoimmunity, and this was dependent on IL-5. To our knowledge, this study is the first to report a role for helminth-induced IL-5 and IL-33 in protection against autoimmunity.