Treatment of lymphocyte-variant hypereosinophilic syndrome (L-HES): what to consider after confirming the elusive diagnosis.

Lymphocyte-variant hypereosinophilic syndrome (L-HES) is a rare disease driven by immunophenotypically aberrant T cells producing eosinophilopoetic cytokines such as interleukin-5 (IL-5). Treatment is challenging because L-HES is relatively steroid resistant and not amenable to tyrosine kinase inhibitors. We searched the literature for clinical trials and observational studies, including case reports, of patients treated for L-HES. In all, 25 studies were selected; two were randomised controlled trials of IL-5 blockade, which included some patients with L-HES, and the rest were observational studies. Corticosteroids are often used as first-line therapy, but patients with L-HES have lower response rates than other types of HES. Treatments that reduce symptoms and steroid dependence in some patients include interferon-alpha (IFN-α), anti-IL-5 monoclonal antibodies, cyclosporine and mycophenolate. These drugs target T-cell activation and proliferation, or IL-5 directly. Although effective, IFN-α and cyclosporine were commonly reported to cause side-effects resulting in discontinuation. Alemtuzumab can induce remissions, but these are generally short lived. The anti-IL-5 monoclonal antibodies mepolizumab and benralizumab are effective and well tolerated, but with a high rate of relapse once withdrawn. Hydroxyurea, methotrexate, imatinib were unsuccessful in most patients studied. More prospective clinical trials are needed for patients with L-HES.

The Cellular Functions of Eosinophils: Collegium Internationale Allergologicum (CIA) Update 2020.

Eosinophils and their secretory mediators play an important role in the pathogenesis of infectious and inflammatory disorders. Although eosinophils are largely evolutionally conserved, their physiologic functions are not well understood. Given the availability of new eosinophil-targeted depletion therapies, there has been a renewed interest in understanding eosinophil biology as these strategies may result in secondary disorders when applied over long periods of time. Recent data suggest that eosinophils are not only involved in immunological effector functions but also carry out tissue protective and immunoregulatory functions that actively contribute to the maintenance of homeostasis. Prolonged eosinophil depletion may therefore result in the development of secondary disorders. Here, we review recent literature pointing to important roles for eosinophils in promoting immune defense, antibody production, activation of adipose tissue, and tissue remodeling and fibrosis. We also reflect on patient data from clinical trials that feature anti-eosinophil therapeutics.

Characterization of a mouse model of hypereosinophilia-associated heart disease.

Hypereosinophilic syndrome is characterized by sustained and marked eosinophilia leading to tissue damage and organ dysfunction. Morbidity and mortality occur primarily due to cardiac and thromboembolic complications. Understanding the cause and mechanism of disease would aid in the development of targeted therapies with greater efficacy and fewer side effects. We discovered a spontaneous mouse mutant in our colony with a hypereosinophilic phenotype. Mice develop peripheral blood eosinophilia; infiltration of lungs, spleen, and heart by eosinophils; and extensive myocardial damage and remodeling. This ultimately leads to heart failure and premature death. Histopathological assessment of the hearts revealed a robust inflammatory infiltrate composed primarily of eosinophils and B-lymphocytes, associated with myocardial damage and replacement fibrosis, consistent with eosinophilic myocarditis. In many cases, hearts showed dilatation and thinning of the right ventricular wall, suggestive of an inflammatory dilated cardiomyopathy. Most mice showed atrial thrombi, which often filled the chamber. Protein expression analysis revealed overexpression of chemokines and cytokines involved in innate and adaptive immunity including IL-4, eotaxin, and RANTES. Disease could be transferred to wild-type mice by adoptive transfer of splenocytes from affected mice, suggesting a role for the immune system. In summary, the pathologies observed in the mutant lines are reminiscent of those seen in patients with hypereosinophilia, where cardiac-related morbidities, like congestive heart failure and thrombi, are the most common causes of death. As such, our model provides an opportunity to test mechanistic hypotheses and develop targeted therapies.NEW & NOTEWORTHY This article describes a new model of heart disease in hypereosinophilia. The model developed as a spontaneous mouse mutant in the colony and is characterized by peripheral blood eosinophilia and infiltration of lungs, spleen, and heart by eosinophils. In the heart, there is extensive myocardial damage, remodeling, fibrosis, and thrombosis, leading to heart failure and death. The immune microenvironment is one of increased innate and adaptive immunity, including Th1 and Th2 cytokines/chemokines. Finally, adoptive transfer of splenocytes transfers disease to recipient mice. In summary, this model provides an opportunity to test mechanistic hypotheses and develop targeted therapies for this rare but devastating disease.

Mechanisms of glucocorticoid resistance in hypereosinophilic syndromes.

BACKGROUND: Glucocorticoids (GC) are considered first-line therapy for most patients with hypereosinophilic syndrome (HES). Although response rates are generally high, many patients require moderate to high doses for control of eosinophilia and symptoms, and up to 15% of patients do not respond at all. Despite this, little is known about the mechanisms of GC resistance in patients with HES. OBJECTIVE: To explore the aetiology of GC resistance in HES. METHODS: Clinical data and samples from 26 patients with HES enrolled on a prospective study of GC responsiveness and 23 patients with HES enrolled on a natural history study of eosinophilia for whom response to GC was known were analysed retrospectively. Expression of GC receptor isoforms was assessed by quantitative RT-PCR in purified eosinophils. Serum cytokine levels were quantified by suspension array assay in multiplex. RESULTS: Despite an impaired eosinophil response to GC after 7 days of treatment, the expected rise in absolute neutrophil count was seen in 7/7 GC-resistant patients, suggesting that GC resistance in HES is not a global phenomenon. Eosinophil mRNA expression of glucocorticoid receptor (GR) isoforms (α, ß, and P) was similar between GC-sensitive (n = 20) and GC-resistant (n = 9) patients with HES. Whereas geometric mean serum levels were also comparable between GC-r (n = 11) and GC-s (n = 19) for all cytokines tested, serum IL-5 levels were >100 pg/mL only in GC-r patients. CONCLUSIONS AND CLINICAL RELEVANCE: These data suggest that the mechanism of GC resistance in HES is not due to a global phenomenon affecting all lineages, but may be due, at least in some patients, to impairment of eosinophil apoptosis by increased levels of IL-5.

Progressive multifocal leukoencephalopathy in a patient with lymphoma and presumptive hyper IgE syndrome.

We, herein, report a 23-year-old male with a rare inherited immunodeficiency disease, hyperimmunoglobulin IgE syndrome (HIES), who developed progressive multifocal leukoencephalopathy (PML) and lymphoma simultaneously. Primary immunodeficiency of the patient has remained undiagnosed until adulthood. PML is a severe demyelinating disease of the central nervous system caused by John Cunningham virus. HIES is a rare, inherited immunodeficiency characterized by high serum levels of IgE, recurrent staphylococcal infection, eczema, and hypereosinophilia. PML may accompany primary immunodeficiency syndromes, but the association with HIES is exceedingly rare. We discuss the imaging findings, medical management, and a review of related literature on primary immunodeficiency cases complicating with PML.

[The Lymphoid Variant of HES (L-HES) as Differential Diagnose of Severe Asthma in Childhood]. / Ein T-Zell assoziiertes Hypereosinophilie-Syndrom (L-HES) als Differenzialdiagnose eines Asthma bronchiale.

Based on a case report an overview on the differential diagnostic considerations with respect to blood hypereosinophilia (HE) and hypereosinophilic syndromes (HES) in childhood is given. A 13-year-old boy was admitted for the clarification of an asthma. In the blood count an increased HE with 3 500/µl (30%) was found along with elevated total serum IgE and IL-5 level (2 000 IU/ml and 17 pg/ml). Lung function showed an obstruction (FEV1 38%). Radiologically the picture of bronchiectasis and mucus pluggine appeared. In the BAL a HE (76%) with raised IL-5 level was apparent. Histologically asthma was diagnosed with mucostasis, hypertrophy of the bronchial wall musculature and a lung HE. Differential-diagnostically an ABPA, a Churg-Strauss-Syndrome, a parasitosis, drug associated HE, allergies and malignant disease could be excluded. An aberrant T-cell clone in peripheral blood was detected by flow cytometry and T-cell receptor clonal rearrangements by PCR, leading to the diagnosis of a lymphoid variant of HES (L-HES). Failure to detect the FIP1L1-PDGFRA gene fusion and a normal bone marrow examination could exclude a neoplastic HES (HESN). After steroid initiation, prompt decrease of blood eosinophilia with resolution of symptoms was observed. Steroid discontinuation led to eosinophilia recurrence associated with disease symptoms. As steroid-sparing agent the immunosuppressive azathioprine was additionally given; steroid doses could be decreased and stopped in the course. This case demonstrated the range of HE evaluation in infancy. With asthma one should also consider the possibility of a L-HES.

CD30+ clonal T-cell lymphoid proliferation of the skin in a patient with hypereosinophilic syndrome.

We report a hitherto undescribed unusual CD30+ clonal T-cell proliferation in a 46-year-old man with the lymphocytic variant of hypereosinophilic syndrome with a 17-year history of pruritus, generalized persistent papulonodular skin lesions and peripheral blood hypereosinophilia. A skin biopsy showed an eosinophil-rich infiltrate with small to medium-sized CD30+ lymphocytes and Churg-Strauss granulomas. Peripheral blood flow cytometry revealed an aberrant T-cell clone which, molecular genetically, was identical to the T-cell clone detected in the skin. No genetic aberrations of platelet-derived growth factor receptor alpha (PDGFRA), FIP1L1-PDGFRA, PDGFRB or FGFR1 were found. The skin lesions showed transient response to systemic and topical corticosteroids. The skin lesions represent cutaneous involvement by clonal T-cells in hypereosinophilic syndrome and differ from known cutaneous CD30+ lymphoproliferative disorders.

Changing roles of eosinophils in health and disease.

OBJECTIVE: To review and highlight the unappreciated roles of eosinophils suggested by recent studies. DATA SOURCES: The literature, unpublished observations, and insights by the authors. STUDY SELECTIONS: Basic studies of mouse models and patient-based clinical studies of disease. RESULTS: Eosinophils are often thought of as destructive end-stage effector cells primarily linked to parasite host defense and dysregulated immune responses associated with allergic diseases, such as asthma. However, recent studies (ie, research focused on mechanisms of action and translational studies examining disease/inflammatory pathways) are suggesting far more complex roles for eosinophils. The goal of this review is 3-fold. (1) The authors examine the dynamic history of eosinophils and how physicians over time used this information to formulate defining hypotheses. Particular emphasis is placed on recent studies challenging the parochial view of host defense in favor of roles maintaining homeostasis through immune modulation and tissue remodeling/repair. (2) They discuss diagnostic approaches to assess eosinophils in clinical settings as a means of disease identification and subsequently as a measurement of disease severity. (3) They examine how contemporary views of eosinophils and their perceived roles in diseases have led to specific therapeutic strategies. The emphasis is to review the successes and failures of these strategies as the basis of formulating future clinical studies targeting eosinophils as potential therapies of disease. CONCLUSION: Despite the complexities of eosinophil-mediated activities and the less than overwhelming success of initial attempts targeting these cells, eosinophils remain a potentially important focal target of disease diagnosis and subsequent treatment strategies.

NIK prevents the development of hypereosinophilic syndrome-like disease in mice independent of IKKα activation.

Immune cell-mediated tissue injury is a common feature of different inflammatory diseases, yet the pathogenetic mechanisms and cell types involved vary significantly. Hypereosinophilic syndrome (HES) represents a group of inflammatory diseases that is characterized by increased numbers of pathogenic eosinophilic granulocytes in the peripheral blood and diverse organs. On the basis of clinical and laboratory findings, various forms of HES have been defined, yet the molecular mechanism and potential signaling pathways that drive eosinophil expansion remain largely unknown. In this study, we show that mice deficient of the serine/threonine-specific protein kinase NF-κB-inducing kinase (NIK) develop a HES-like disease, reflected by progressive blood and tissue eosinophilia, tissue injury, and premature death at around 25-30 wk of age. Similar to the lymphocytic form of HES, CD4(+) T cells from NIK-deficient mice express increased levels of Th2-associated cytokines, and eosinophilia and survival of NIK-deficient mice could be prevented completely by genetic ablation of CD4(+) T cells. Experiments based on bone marrow chimeric mice, however, demonstrated that inflammation in NIK-deficient mice depended on radiation-resistant tissues, implicating that NIK-deficient immune cells mediate inflammation in a nonautonomous manner. Surprisingly, disease development was independent of NIK's known function as an IκB kinase α (IKKα) kinase, because mice carrying a mutation in the activation loop of IKKα, which is phosphorylated by NIK, did not develop inflammatory disease. Our data show that NIK activity in nonhematopoietic cells controls Th2 cell development and prevents eosinophil-driven inflammatory disease, most likely using a signaling pathway that operates independent of the known NIK substrate IKKα.

Long-term safety of mepolizumab for the treatment of hypereosinophilic syndromes.

BACKGROUND: Hypereosinophilic syndromes (HESs) are chronic disorders that require long-term therapy to suppress eosinophilia and clinical manifestations. Corticosteroids are usually effective, yet many patients become corticosteroid refractory or develop corticosteroid toxicity. Mepolizumab, a humanized monoclonal anti-IL-5 antibody, showed corticosteroid-sparing effects in a double-blind, placebo-controlled study of FIP1L1/PDGFRA-negative, corticosteroid-responsive subjects with HESs. OBJECTIVE: We evaluated long-term safety and efficacy of mepolizumab (750 mg) in HES. METHODS: MHE100901 is an open-label extension study. The primary end point was the frequency of adverse events (AEs). Optimal dosing frequency, corticosteroid-sparing effect of mepolizumab, and development of antimepolizumab antibodies were also explored. RESULTS: Seventy-eight subjects received 1 to 66 mepolizumab infusions each (including mepolizumab infusions received in the placebo-controlled trial). Mean exposure was 251 weeks (range, 4-302 weeks). The most common dosing interval was 9 to 12 weeks. The incidence of AEs was 932 events per 100 subject-years in the first year, declining to 461 events per 100 subject-years after 48 months. Serious AEs, including 1 death, were reported by the investigator as possibly due to mepolizumab in 3 subjects. The median daily prednisone dose decreased from 20.0 to 0 mg in the first 24 weeks. The median average daily dose for all subjects over the course of the study was 1.8 mg. Sixty-two percent of subjects were prednisone free without other HES medications for ≥ 12 consecutive weeks. No neutralizing antibodies were detected. Twenty-four subjects withdrew before study completion for death (n = 4), lack of efficacy (n = 6), or other reasons. CONCLUSION: Mepolizumab was well tolerated and effective as a long-term corticosteroid-sparing agent in PDGFRA-negative HES.

Eosinophils affect functions of in vitro-activated human CD3-CD4+ T cells.

BACKGROUND: The recent development of eosinophil-targeting agents has raised enthusiasm for management of patients with hypereosinophilic syndromes. Roughly half of anti-IL-5-treated patients with corticosteroid-responsive lymphocytic (L-HES) and idiopathic disease variants can be tapered off corticosteroids. Potential consequences of corticosteroid-withdrawal on clonal expansion of pre-malignant CD3⁻CD4⁺ T-cells associated with L-HES are a subject of concern. Indeed, corticosteroid treatment inhibits T-cell activation and may lower blood CD3⁻CD4⁺ cell counts. On the other hand, previous studies have shown that eosinophils support CD4 T-cell activation, suggesting that targeted eosinophil depletion may negatively regulate these cells. OBJECTIVES: Effects of eosinophils on CD4 T-cell activation in vitro were investigated as an indirect means of exploring whether treatment-induced eosinophil depletion may affect pathogenic T-cells driving L-HES. METHODS: Helper (CD4) T-cells and CD3⁻CD4⁺ cells from healthy controls and L-HES patients, respectively, were cultured in vitro in presence of anti-CD3/CD28 or dendritic cells. Effects of eosinophils on T-cell proliferation and cytokine production were investigated. RESULTS: Eosinophils enhanced CD3-driven proliferation of CD4 T-cells from healthy subjects in vitro, while inhibiting TCR-independent proliferation and IL-5 production by CD3⁻CD4⁺ T-cells. CONCLUSIONS: While this study confirms previous work showing that eosinophils support activation of normal helper T-cells, our in vitro findings with CD3⁻CD4⁺ T-cells suggest that eosinophil-depletion may favor activation and expansion of this pathogenic lymphocyte subset. With the ongoing development of eosinophil-targeted therapy for various eosinophilic conditions, the indirect consequences of treatment on the underlying immune mechanisms of disease should be investigated in detail in the setting of translational research programs.

Therapeutic strategies for harnessing human eosinophils in allergic inflammation, hypereosinophilic disorders, and cancer.

The eosinophil is a multifunctional granulocyte best known for providing host defense against parasites. Paradoxically, eosinophils are also implicated in the pathogenesis of allergic inflammation, asthma, and hypereosinophilic syndromes. Emerging evidence also supports the potential for harnessing the cytotoxic power of eosinophils and redirecting it to kill solid tumors. Central to eosinophil physiology is interleukin-5 (IL-5) and its receptor (IL-5R) which is composed of a ligand-specific alpha chain (IL-5Rα) and the common beta chain (ßc). Eosinophil activation can lead to their degranulation, resulting in rapid release of an arsenal of tissue-destructive proinflammatory mediators and cytotoxic proteins that can be both beneficial and detrimental to the host. This review discusses eosinophil immunobiology and therapeutic strategies for targeting of IL-5 and IL-5R, as well as the potential for harnessing eosinophil cytotoxicity as a tumoricide.

IL-32 up-regulation is associated with inflammatory cytokine production in allergic rhinitis.

IL-32 is a described pro-inflammatory cytokine produced by T lymphocytes, natural killer cells, monocytes, and epithelial cells. However, the specific mechanism of IL-32 on allergic rhinitis (AR) has not been elucidated. Here, we report a significant increase of IL-32 protein and mRNA in the nasal mucosa of AR patients. In addition, in nasal mucosa tissue from AR patients, the level of IL-32 production correlated with inflammation, IL-1ß, IL-18, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In an AR animal model, IL-32 significantly increased IgE and inflammatory cytokine levels. IL-32 expression was induced by recombinant human GM-CSF via activation of caspase-1 in eosinophils. In addition, depletion of IL-32 prevents the production of inflammatory cytokines in eosinophils. In conclusion, IL-32 is an important cytokine involved in the inflammation of AR. The regulation of IL-32 expression may form the basis of a new strategy for the treatment of AR.

Gene therapy in a murine model of chronic eosinophilic leukemia-not otherwise specified (CEL-NOS).

Chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) is a rare, aggressive, fatal disease characterized by blood eosinophilia and dysfunction of organs infiltrated with eosinophils. Clinically, the disease manifests with weight loss, cough, weakness, diarrhea, and multi-organ dysfunction that is unresponsive to therapy. We developed a one-time gene therapy for CEL-NOS using an adeno-associated virus (AAV) expressing an anti-eosinophil monoclonal antibody (AAVrh.10mAnti-Eos) to provide sustained suppression of eosinophil numbers in blood, thus reducing eosinophil tissue invasion and organ dysfunction. A novel CEL-NOS model was developed in NOD-scid IL2rγnull (NSG) mice by administration of AAV expressing the cytokine IL5 (AAVrh.10mIL5), resulting in marked peripheral and tissue eosinophilia of the heart, lung, liver, and spleen, and eventually death. Mice were administered AAVrh.10mAnti-Eos (1011 genome copies) 4 wk after administration of AAVrh.10mIL5 and evaluated for anti-eosinophil antibody expression, blood eosinophil counts, organ eosinophil invasion, and survival. AAVrh.10mAnti-Eos expressed persistent levels of the anti-eosinophil antibody for >24 wk. Strikingly, CEL-NOS treated mice had markedly lower blood eosinophil levels and reduced mortality when compared with control treated mice. These results suggest that a single treatment with AAVrh.10mAnti-Eos has the potential to provide substantial therapeutic benefit to patients with CEL-NOS, a fatal malignant disorder.