Chronic eosinophilic pneumonia: clinical perspectives

The long-term outcomes of mepolizumab treatment at 100 mg dose on idiopathic chronic eosinophilic pneumonia: A real-life experience

Background: The standard therapeutic regimen for idiopathic chronic eosinophilic pneumonia (ICEP) involves the administration of oral corticosteroids (OCS). However, a notable proportion of individuals experience recurrent episodes after the tapering or cessation of OCS during the course of ICEP. There has been a growing interest in exploring alternative treatment modalities for patients with ICEP at heightened risk of relapse. Objective: The aim of this study was to assess the efficacy of mepolizumab at a dose of 100 mg administered every 4 weeks in preventing relapses of ICEP and its impact on the clinical outcomes. Methods: This retrospective clinical observational study used real-world data to assess the impact of mepolizumab on patients diagnosed with ICEP accompanied by severe asthma. Demographic information and clinical characteristics were extracted from medical records. The study examined the effect of mepolizumab on the annual relapse rate, OCS dose, eosinophil count, and respiratory function parameters. Results: All patients included in the study, with a median (range) follow-up period of 19 months (4-40 months), the annual relapse rate decreased from 0.33 to 0 after the initiation mepolizumab. In addition, the maintenance OCS dose, expressed in methylprednisolone equivalents, declined from 4 mg/day to 0 mg/day. A reduction in the blood eosinophil count was observed, alongside a partial improvement in respiratory function test results among the patients. Conclusıon: A dose regimen of 100 mg of mepolizumab administered every 4 weeks emerges as a promising and well-tolerated therapeutic approach for averting relapses of ICEP.

The role of radiological imaging in the management of severe and difficult-to-treat asthma

Radiological imaging has proven to be a useful tool in the assessment of asthma, its comorbidities and potential complications. Characteristic chest radiograph and computed tomography scan findings can be seen in asthma and in other conditions that can coexist with or be misdiagnosed as asthma, including chronic rhinosinusitis, inducible laryngeal obstruction, excessive dynamic airway collapse, tracheobronchomalacia, concomitant COPD, bronchiectasis, allergic bronchopulmonary aspergillosis, eosinophilic granulomatosis with polyangiitis, and eosinophilic pneumonia. The identification of the characteristic radiological findings of these conditions is often essential in making the correct diagnosis and provision of appropriate management and treatment. Furthermore, radiological imaging modalities can be used to monitor response to therapy.

Monoclonal antibodies in idiopathic chronic eosinophilic pneumonia: a scoping review

BACKGROUND

Idiopathic chronic eosinophilic pneumonia (ICEP) is a rare disease characterized by pulmonary radiological alterations, peripheral eosinophilia, and demonstrated pulmonary eosinophilia. Oral steroids (OSs) are the standard management, but relapses occur in up to 50% of patients during the decrease or suspension of steroids, usually requiring reinitiation of treatment, exposing patients to secondary events derived from the management. Management with monoclonal antibodies has been proposed in these cases to control the disease and limit the secondary effects. The objective is to describe the extent and type of evidence regarding the use of monoclonal antibodies for ICEP.

METHODS

A panoramic review of the literature was performed. Observational and experimental studies of pediatric and adult populations that managed recurrent ICEP with monoclonal antibodies were included. Data search, selection, and extraction were performed by two independent reviewers.

RESULTS

937 studies were found. After applying the inclusion and exclusion criteria, 37 titles remained for the final analysis: a retrospective, observational, real-life study, two case series publications, and 34 case reports published in academic poster sessions and letters to the editor. In general, the use of monoclonal antibodies approved for severe asthma could be useful for the control of ICEP, since most of the results show a good response for clinical and radiological outcomes. Biological drugs seem to be a safer option for controlling relapses in ICEP, allowing lowering/suspension of OSs, and sometimes replacing them in patients intolerant to them, patients with significant comorbidities, and patients who have already developed adverse events.

CONCLUSION

The extent of the evidence supporting management of ICEP with monoclonal antibodies against IL-5 and IgE (omalizumab) is limited, but it could be promising in patients who present frequent relapses, in cortico-dependent individuals, or in patients in whom the use of steroids is contraindicated. The extent of the evidence for management with dupilumab is more limited. Studies with better design and structure are needed to evaluate quality of life and outcomes during a clear follow-up period. To our knowledge, this is the first scoping review of the literature showing the extent of the evidence for the management of ICEP with monoclonal antibodies.

A case of recurrent chronic eosinophilic pneumonia after switching from benralizumab to dupilumab

Dupilumab inhibits interleukin-4Rα and suppresses type 2 inflammation. Careful administration of dupilumab is required because it increases the blood eosinophil count secondary to a decrease in local eosinophil counts, sometimes resulting in eosinophilic complications. We herein report a case of recurrent chronic eosinophilic pneumonia after switching from benralizumab to dupilumab. A 54-year-old man with a history of eosinophilic pneumonia presented to our hospital with symptoms of cough, fever, and phlegm production six months after beginning dupilumab administration for recurrent chronic rhinosinusitis. When using dupilumab, it is essential to carefully monitor patients' eosinophil trends and pulmonary symptoms.

Methylphenidate causes chronic eosinophilic pneumonia

A man who is 38 years old and diagnosed with attention-deficit hyperactivity disorder was prescribed methylphenidate. Three weeks later, he began experiencing progressive shortness of breath and coughing. Imaging of his chest showed patchy bilateral ground-glass opacities, and bronchoscopy revealed a 15% eosinophil count in his bronchoalveolar lavage. A transbronchial biopsy confirmed a diagnosis of eosinophilic pneumonia. The patient's condition improved when he was given steroids and stopped taking methylphenidate. However, he developed the same symptoms again a few days after restarting the medication, along with a skin rash. This strongly suggests that methylphenidate was the cause of his eosinophilic pneumonia.

Diagnostic journey of chronic eosinophilic pneumonia masked as lung cancer: a rare case report

Introduction and Importance

Chronic eosinophilic pneumonia (CEP) is an idiopathic condition characterized by unusually high eosinophil infiltration in the lungs' interstitium and alveolar spaces. It is extremely rare, accounting for fewer than 3% of all interstitial lung diseases. CEP is frequently misdiagnosed as lung cancer, which can have catastrophic consequences for sufferers. When assessing patients with lung disease, doctors should be aware of CEP's symptoms and take its prognosis into account because it is a curable disorder.

Case Presentation

A 40-year-old female presented in the outpatient department of gynecology with a history of abnormal vaginal bleeding for 3 months and mild shortness of breath without any other significant medical history or being under any medications. Physical examination findings were not significant.

Clinical Discussion

Ultrasound revealed adenomyosis and a hysterectomy was planned. Chest radiograph revealed lung mass and computed tomography scan showed a well-defined mass with a pleural-based nodule. Histopathology revealed interstitial fibrosis and eosinophilic microabscesses. CEP was diagnosed and oral prednisolone was started with a 0.5 mg/kg/day dose. Chest radiographic abnormalities resolved after one month of treatment. Currently, she is asymptomatic.

Conclusion

Early recognition and diagnosis of lung masses are essential for prompt treatment with corticosteroids. CEP can mimic lung malignancy and should be considered in patients with related symptoms.

Acute Versus Chronic Eosinophilic Pneumonia: A Case Report

Eosinophilic pneumonia is a very rare form of interstitial lung disease. It is subdivided into acute and chronic types. Both types share some characteristics differences and similarities. We report two unique cases of acute eosinophilic pneumonia (AEP) and chronic eosinophilic pneumonia seen in 37- and 30-year-old males, respectively. Both cases occurred in the summer of the same year. There was no known association between the two patients except that they were both young males. We were able to compare the unique features of AEP and chronic eosinophilic pneumonia (CEP) and how these relate to the cases presented.

Eosinophilic granulomatosis with polyangiitis - Advances in pathogenesis, diagnosis, and treatment

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare disease characterized by eosinophil-rich granulomatous inflammation and necrotizing vasculitis, pre-dominantly affecting small-to-medium-sized vessels. It is categorized as a primary antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) but also shares features of hypereosinophilic syndrome (HES); therefore, both vessel inflammation and eosinophilic infiltration are suggested to cause organ damage. This dual nature of the disease causes variable clinical presentation. As a result, careful differentiation from mimicking conditions is needed, especially from HES, given the overlapping clinical, radiologic, and histologic features, and biomarker profile. EGPA also remains a diagnostic challenge, in part because of asthma, which may pre-dominate for years, and often requires chronic corticosteroids (CS), which can mask other disease features. The pathogenesis is still not fully understood, however, the interaction between eosinophils and lymphocytes B and T seems to play an important role. Furthermore, the role of ANCA is not clear, and only up to 40% of patients are ANCA-positive. Moreover, two ANCA-dependent clinically and genetically distinct subgroups have been identified. However, a gold standard test for establishing a diagnosis is not available. In practice, the disease is mainly diagnosed based on the clinical symptoms and results of non-invasive tests. The unmet needs include uniform diagnostic criteria and biomarkers to help distinguish EGPA from HESs. Despite its rarity, notable progress has been made in understanding the disease and in its management. A better understanding of the pathophysiology has provided new insights into the pathogenesis and therapeutic targets, which are reflected in novel biological agents. However, there remains an ongoing reliance on corticosteroid therapy. Therefore, there is a significant need for more effective and better-tolerated steroid-sparing treatment schemes.

Pneumothorax with Eosinophilia is an Important Diagnostic Clue for Distinguishing Paragonimiasis from Chronic Eosinophilic Pneumonia: A Case Report

The Paragonimus westermani infection is a parasitic foodborne infection that induces systemic symptoms with eosinophilia in humans. Here, we described pneumothorax in addition to pulmonary opacities with eosinophilia in a man with a positive P. westermani serology. He was misdiagnosed with chronic eosinophilic pneumonia (CEP) during the initial phase. Paragonimiasis can share similar clinical findings with CEP in cases where the worm is confined to the lungs. The findings of the current study suggest that paragonimiasis and CEP can be distinguished from each other by the presence of various symptoms. Notably, eosinophilia with pneumothorax should be an important diagnostic factor for paragonimiasis.

Benralizumab in the management of rare primary eosinophilic lung diseases

Background: Eosinophils have a double-edged role in the human body, being essential in important physiologic functions but whose presence is conspicuous in a variety of diseases characterized by a T2 inflammation phenotype. Eosinophils are exquisitely sensitive to corticosteroids, and the latter have, until recently, represented the cornerstone of treatment of eosinophilic diseases. However, most patients remain dependent on oral corticosteroids, with a notable adverse effect burden and experience a chronic relapsing disease that leads to high morbidity and mortality. Treatment prospects have changed with the advent of biologic drugs that target the eosinotropic cytokine interleukin (IL) 5 or its receptor. The success of the latter drugs in severe eosinophilic asthma has paved the way for their use in other, rarer, eosinophilic lung diseases. Recently, mepolizumab, a humanized monoclonal antibody that works against IL-5, was approved for the add-on treatment of relapsing-remitting or refractory eosinophilic granulomatosis with polyangiitis (EGPA) in patients ages ≥ 6 years. Benralizumab, a humanized antibody that binds to the α portion of the IL-5 receptor, is also being tested for its efficacy in EGPA in two clinical trials, after a growing number of case reports and case series supported its use as a steroid-sparing agent in the treatment of EGPA. Methods: In this review, we summarized the scientific literature evaluating the efficacy of benralizumab treatment in patients afflicted with rare primary eosinophilic lung diseases. Results: The literature we found, largely case reports, reported that the use of benralizumab in EGPA, chronic eosinophilic pneumonia (CEP) and allergic bronchopulmonary aspergillosis (ABPA) often led to a depletion of eosinophils, less exacerbations and a decreased systemic corticosteroid burden. No adverse effects were reported. Conclusion: Benralizumab has a prospective role in the treatment of rare eosinophilic lung diseases, which needs to be further elucidated in randomized controlled trials.

Predictive factors for relapse in corticosteroid-treated patients with chronic eosinophilic pneumonia

BACKGROUND

Chronic eosinophilic pneumonia (CEP) is an idiopathic disorder characterised by an abnormal and marked accumulation of eosinophils in the interstitium and alveolar spaces of the lungs. Systemic corticosteroid (CS) therapy leads to marked improvement. However, relapse is common in the clinical course, and the predictive factors for relapse of CEP are not well known. This study aimed to investigate predictive factors for relapse in CS-treated cases of CEP.

METHODS

We identified consecutive patients with CEP at our institution between 1999 and 2019. We retrospectively reviewed 36 CS-treated patients with CEP who underwent bronchoalveolar lavage (BAL) and high-resolution computed tomography (CT) at diagnosis. We examined relapse at least 1 year after the initiation of CS treatment. Statistical analysis included univariate and multivariate Cox proportional hazard regression analyses; P<0.05 was considered statistically significant.

RESULTS

The median (interquartile range) age at diagnosis was 59.5 years (47.8-70.0 years). This study included 13 men and 23 women. Twenty-five patients (69.4%) were never smokers and 15 (41.7%) had asthma. The peripheral blood eosinophil percentage was 35.0% (15.6-55.8%), and the BAL eosinophil percentage was 40.8% (10.7-68.5%). The median serum surfactant protein-D (SP-D) level was 135 ng/mL (82.2-176.7 ng/mL). High-resolution CT revealed centrilobular opacities in 23 patients (63.9%). Relapse of CEP was observed in 20 patients (55.6%). Higher serum SP-D levels and the presence of centrilobular opacities on high-resolution CT were significant predictors of relapse in multivariate Cox proportional hazard regression analysis (P=0.017 and P=0.028, respectively). Additionally, we devised a relapse prediction model for CS-treated CEP using two categorical parameters: the presence of centrilobular opacities and serum levels of SP-D (>135/≤135 ng/mL). Based on these parameters, cases were scored 2, 1, or 0. Patients with a score of 2 experienced relapses earlier than those with scores of 1 and 0 (log-rank test; P=0.006, P=0.003, respectively).

CONCLUSIONS

Centrilobular opacities on high-resolution CT and higher serum SP-D levels at diagnosis may be predictive factors for relapse in CS-treated patients with CEP.

Eosinophilic airway diseases: basic science, clinical manifestations and future challenges

Eosinophils have a broad range of functions, both homeostatic and pathological, mediated through an array of cell surface receptors and specific secretory granules that promote interactions with their microenvironment. Eosinophil development, differentiation, activation, survival and recruitment are closely regulated by a number of type 2 cytokines, including interleukin (IL)-5, the key driver of eosinophilopoiesis. Evidence shows that type 2 inflammation, driven mainly by interleukin (IL)-4, IL-5 and IL-13, plays an important role in the pathophysiology of eosinophilic airway diseases, including asthma, chronic rhinosinusitis with nasal polyps, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome. Several biologic therapies have been developed to suppress type 2 inflammation, namely mepolizumab, reslizumab, benralizumab, dupilumab, omalizumab and tezepelumab. While these therapies have been associated with clinical benefits in a range of eosinophilic diseases, their development has highlighted several challenges and directions for future research. These include the need for further information on disease progression and identification of treatable traits, including clinical characteristics or biomarkers that will improve the prediction of treatment response. The Nordic countries have a long tradition of collaboration using patient registries and Nordic asthma registries provide unique opportunities to address these research questions. One example of such a registry is the NORdic Dataset for aSThmA Research (NORDSTAR), a longitudinal population-based dataset containing all 3.3 million individuals with asthma from four Nordic countries (Denmark, Finland, Norway and Sweden). Large-scale, real-world registry data such as those from Nordic countries may provide important information regarding the progression of eosinophilic asthma, in addition to clinical characteristics or biomarkers that could allow targeted treatment and ensure optimal patient outcomes.

Evaluating the relationship between high-resolution computed tomography findings and their extent in eosinophilic lung diseases with peripheral blood eosinophil level

Purpose

Eosinophilic lung diseases are a group of pulmonary disorders associated with peripheral or tissue eosinophilia. They can be classified into primary (idiopathic) and secondary groups based on their aetiology. On the other hand, blood eosinophilia is a common clinical problem with various causes. In many cases the lung infiltrations in patients with peripheral eosinophilia are non-eosinophilic. Herein, we aim to assess the relationship between blood eosinophilia and abnormal high-resolution computed tomography (HRCT) features and their extent in idiopathic chronic eosinophilic pneumonia (ICEP) (the most common form of idiopathic eosinophilic lung disease). This can help in differentiating eosinophilic from non-eosinophilic lung infiltrations in patients with blood eosinophilia.

Material and methods

In this descriptive-correlational study, all patients with proven ICEP, who were referred to Masih Daneshvari Hospital, Tehran, Iran from 2012 to 2019, were included. The ICEP diagnosis was based on lung infiltrations on imaging, in addition to increased numbers of eosinophils in bronchoalveolar lavage fluid, blood or lung biopsy samples, and rapid response to corticosteroids. Patients with known aetiologies for eosinophilic lung diseases were excluded. The HRCT findings and their extent in each patient were compared with the blood eosinophil level.

Results

Positive correlation was found only between blood eosinophil level and frequency and extent of consolidation, and with frequency of lymphadenopathy.

Conclusions

HRCT can help to differentiate eosinophilic from non-eosinophilic lung infiltrations in patients with blood eosinophilia by comparing the extent of consolidation with the blood eosinophil level.

Mepolizumab and dupilumab as a replacement to systemic glucocorticoids for the treatment of Chronic Eosinophilic Pneumonia and Allergic Bronchopulmonary Aspergillosis - Case series, Almoosa specialist hospital

In this case series, we present four patients who had asthma and blood eosinophilia. Two patients were diagnosed with Chronic Eosinophilic Pneumonia (CEP) and the other two with Allergic Bronchopulmonary Aspergillosis (ABPA). Laboratory findings revealed profound peripheral eosinophilia with abnormal chest radiography (alveolar shadows, segmental atelectasis, and cystic changes). Initial improvement (clinical, laboratory, and radiological) occurred with traditional asthma therapy, including systemic corticosteroids. The patients did not tolerate corticosteroid therapy because of weight gain, uncontrolled diabetes, bone fractures, and psychological adverse effects. Mepolizumab (administered to two CEP cases and one ABPA case) and Dupilumab (administered to one ABPA case) were initiated as steroid-sparing agents, resulting in successful therapy without relapse or adverse effects. Mepolizumab, and Interleukin-5 (IL-5) antagonist, targets diseases mediated by eosinophil activity and proliferation. Dupilumab blocks the Interleukin-4/Interleukin-13 pathway and suppresses Type 2 inflammation, including Immunoglobulin E (IgE). Dupilumab resulted in up to 70% drop in total IgE levels from baseline and reduced eosinophil-mediated lung inflammation, despite the presence of normal or increased blood eosinophil counts.

IL13 May Play an Important Role in Developing Eosinophilic Chronic Rhinosinusitis and Eosinophilic Otitis Media with Severe Asthma

A woman in her 50s was a super responder to benralizumab administered for the treatment of severe bronchial asthma (BA) with eosinophilic chronic rhinosinusitis with nasal polyp (ECRS) and eosinophilic otitis media (EOM). She exhibited the gradual exacerbation of ECRS/EOM despite good control of BA approximately 1 year after benralizumab initiation. Therefore, the treatment was switched to dupilumab, and the condition of the paranasal sinuses and middle ear greatly improved with the best control of her asthma. The patient reported that her physical condition was the best of her life. However, she developed a pulmonary opacity on chest computed tomography after 6 months. Histological examination of the lung parenchyma and cell differentiation of the bronchoalveolar lavage fluid indicated atypical chronic eosinophilic pneumonia, and treatment was switched to mepolizumab. Similarly to the period of benralizumab treatment, exacerbation of ECRS/EOM reduced her quality of life approximately 10 months after the administration of mepolizumab. Dupilumab was again introduced as a replacement for mepolizumab. The clinical course and consideration of the interaction between inflammatory cells led us to speculate that interleukin-13 could play a key role in the development of ECRS/EOM with severe BA.

Recurrent pneumonia with persistent peripheral eosinophilia: Idiopathic chronic eosinophilic pneumonia

Although ICEP is an exceptionally rare disease, it is potentially overlooked and misdiagnosed. This case highlights the importance of peripheral eosinophilia in raising suspicion for ICEP. Without treatment, majority of patients fail to improve.

Eosinophil extracellular traps in a patient with chronic eosinophilic pneumonia

Eosinophils rapidly release extracellular filamentous chromatin fibers (extracellular traps, ETs) when they are stimulated. Reticulated ETs have been recently shown to affect secretion viscosity in eosinophilic inflammatory diseases. Here we report a 43-year-old woman with infiltrative shadows in both upper lungs that did not respond well to antibiotics. She admitted to occasional coughing and sputum, but had poor viscous regulation. Bronchoalveolar lavage fluid (BALF) collected from the upper left lobe showed many eosinophils (65%). She was diagnosed with chronic eosinophilic pneumonia, per previously reported criteria, and began treatment with prednisolone. The infiltration shadow gradually improved, and she was discharged 28 days after admission. Later, we immune-stained her BALF cell components with antibodies against major basic protein, an eosinophil granule protein, which showed a large number of agglomerating eosinophils; and antibodies against citrullinated histone H3 (CitH3-a marker for ETs), which showed CitH3-positive ETs, spread in a network. These findings confirmed that some BALF eosinophils released eosinophil ETs. This case shows the existence of ETs from BALF in patients with chronic eosinophilic pneumonia. Concentration of eosinophil ETs in eosinophilic inflammatory diseases may affect secretion viscosity in sputum, and so on.

Chronic eosinophilic pneumonitis due to the inhalation of aerosolized face lotion: A case report

RATIONALE

Inhalation of toxic agents can induce eosinophilic pneumonia. However, only a few case reports demonstrate that exposure to materials can induce chronic eosinophilic pneumonia (CEP). Here, we describe a rare case of CEP with mild alveolar hemorrhage due to the inhalation of aerosols from face lotion. This is the first report of eosinophilic pneumonia caused by face lotion exposure.

PATIENT CONCERNS

A 39-year-old woman was admitted to our hospital with cough and dyspnea for 2 months, which coincided when she started to use a new aerosolized face lotion. Laboratory findings showed high blood eosinophil levels, and chest computed tomography (CT) scans revealed bilateral peripheral consolidation and ground-glass opacity mainly in the left upper lobe. She underwent flexible bronchoscopy. Eosinophils in bronchoalveolar lavage fluid (BALF) were slightly elevated, and the gross appearance of BALF was bloody. The histological examination of the transbronchial lung biopsy showed infiltration of eosinophils and macrophages in alveolar septa with edema and without vasculitis and granuloma formation; a small number of hemosiderin-laden macrophages were also observed. An inhalation challenge test involving the face lotion was performed. Six hours after the test, the blood test showed an increased white blood cell (WBC) count, and chest radiography showed slight exacerbation. Forced vital capacity decreased the following day.

DIAGNOSIS

According to histological analysis and positive result of an inhalation challenge test, she was diagnosed with CEP with mild alveolar hemorrhage due to inhalation of aerosols from the face lotion.

INTERVENTIONS AND OUTCOMES

She gradually improved without medication after stopping the use of face lotion.

LESSONS

To the best of our knowledge, this is the first report of CEP with mild alveolar hemorrhage due to the inhalation of face lotion. Various inhaled agents, such as face lotion, can induce CEP in rare cases.

Treatment and relapse of interstitial lung disease in nivolumab-treated patients with non-small cell lung cancer

Nivolumab, a human monoclonal antibody against programmed death‐1, is approved for the treatment of non–small cell lung cancer (NSCLC). Although nivolumab is generally well tolerated, it can cause interstitial lung disease (ILD), a rare but potentially fatal immune‐related adverse event. Currently, there are limited data available on the treatment of nivolumab‐induced ILD and its outcome. This retrospective cohort study based on a post–marketing study described the treatment of nivolumab‐induced ILD and its outcome in NSCLC patients in Japan through the assessment of clinical and chest imaging findings by an expert central review committee. Treatment details for patients who experienced a relapse of ILD were also analyzed. Of the 238 patients identified as having nivolumab‐induced ILD, 37 patients died of ILD. Corticosteroids were used in 207 (87.0%) patients. Of those, 172 (83.1%) patients responded well and survived and 35 (16.9%) died (most died during corticosteroid treatment). A total of nine patients experienced a relapse; at the time of relapse, four patients were taking nivolumab. Of those who were receiving corticosteroids at the time of relapse, three of four patients were taking low doses or had nearly completed dose tapering. All patients (except one, whose treatment was unknown) received corticosteroids for the treatment of relapse, but one patient died. Patients with NSCLC who experience nivolumab‐induced ILD are treated effectively with corticosteroids, and providing extra care when ceasing or reducing the corticosteroid dose may prevent relapse of ILD.

Targeting eosinophils in respiratory diseases: Biological axis, emerging therapeutics and treatment modalities

Eosinophils are bi-lobed, multi-functional innate immune cells with diverse cell surface receptors that regulate local immune and inflammatory responses. Several inflammatory and infectious diseases are triggered with their build up in the blood and tissues. The mobilization of eosinophils into the lungs is regulated by a cascade of processes guided by Th2 cytokine generating T-cells. Recruitment of eosinophils essentially leads to a characteristic immune response followed by airway hyperresponsiveness and remodeling, which are hallmarks of chronic respiratory diseases. By analysing the dynamic interactions of eosinophils with their extracellular environment, which also involve signaling molecules and tissues, various therapies have been invented and developed to target respiratory diseases. Having entered clinical testing, several eosinophil targeting therapeutic agents have shown much promise and have further bridged the gap between theory and practice. Moreover, researchers now have a clearer understanding of the roles and mechanisms of eosinophils. These factors have successfully assisted molecular biologists to block specific pathways in the growth, migration and activation of eosinophils. The primary purpose of this review is to provide an overview of the eosinophil biology with a special emphasis on potential pharmacotherapeutic targets. The review also summarizes promising eosinophil-targeting agents, along with their mechanisms and rationale for use, including those in developmental pipeline, in clinical trials, or approved for other respiratory disorders.

Mepolizumab: an alternative therapy for idiopathic chronic eosinophilic pneumonia with glucocorticoid intolerance

A 55-year-old woman with cough-variant asthma presented for 1 month of worsening wheezing, cough, and dyspnea refractory to treatment. Initial laboratory findings revealed profound peripheral eosinophilia, and a chest computed tomography showed bi-apical consolidation. Bronchio-alveolar lavage demonstrated alveolar eosinophilia. She was diagnosed with idiopathic chronic eosinophilic pneumonia (ICEP). Her peripheral eosinophilia and respiratory symptoms improved rapidly with high-dose systemic corticosteroid therapy. However, she was intolerant to corticosteroid monotherapy due to non-compliance and psychological adverse effects. Mepolizumab was initiated as a steroid-sparing agent, resulting in successful therapy for 2 years without relapse or adverse effects. Mepolizumab is an interleukin-5 (IL-5) antagonist monoclonal antibody, which is a targeted therapy for diseases mediated by eosinophil activity and eosinophil proliferation. Mepolizumab is typically used in ICEP refractory to steroids, but this case supports its use in cases of glucocorticoid intolerance. Further study of IL-5 antagonist therapies for ICEP may identify an alternative treatment modality for patients in whom the adverse effects of corticosteroids pose a challenge.