Charcot-Leyden Crystals in Eosinophilic Inflammation: Active Cytolysis Leads to Crystal Formation

Eosinophil ETosis and Charcot-Leyden crystals in Kimura disease

Two cases of refractory Kimura disease that required treatment with biologic agents are reported. Their pathology suggests the involvement of eosinophil ETosis, which is active cell death producing Charcot-Leyden crystals.

Eosinophil cytolysis with or without ETosis in four cases of human gastric cancer: a comparative ultrastructural study

The ultrastructural morphology of eosinophil cytolysis and extracellular trap cell death (ETosis) has predominantly been examined in non-neoplastic eosinophil-associated diseases, with a limited investigation in neoplasms. This current electron microscopy study examined the ultrastructural characteristics of eosinophil cytolysis and ETosis across four distinct gastric cancer cases: three cases (cases 1-3) exhibited non-ETotic cytolysis, while one case (case 4) presented eosinophils at various stages of ETosis. In cases 1-3, eosinophil non-ETotic cytolysis was characterized by localized plasma membrane disruption, the presence of free extracellular granules (FEGs), and the maintenance of a round or oval nuclear lobe profile. In case 4, eosinophils were observed in progressive stages of ETosis, arbitrarily subdivided into early, intermediate, and advanced. Although early ETosis and non-ETotic cytolysis exhibited overlapping ultrastructural features, chromatin decondensation and nuclear envelope enlargement were more pronounced in early ETosis. Nuclear envelope disruption, loss of the round or oval nuclear lobe profile (intermediate stage), extracellular DNA trap deposition, and the appearance of Charcot-Leyden crystals (advanced stage) were all distinctive features of ETosis. The findings of this case report confirm previous observations of eosinophil cytolysis with or without ETosis in non-neoplastic diseases and extend them to advanced gastric carcinoma. Since Charcot-Leyden crystals were only seen in case 4, their correlation with ETosis was further supported. In gastric cancer, the release of FEGs during non-ETotic cytolysis and the release of both FEGs and DNA traps during ETotic cytolysis may contribute to the formation of an antitumor microenvironment.

Charcot-Leyden Crystals in Hepatic Abscess: A Diagnostic Clue Unveiling Parasitic Infection Through Fine-Needle Aspiration Cytology

Charcot-Leyden crystals (CLCs) are hexagonal, colorless, bipyramidal structures derived from the aggregation of materials formed by disintegrating eosinophils. Necrotic cell debris and CLCs serve as indirect indicators of parasitic infestation. Here, we highlight a case of a 49-year-old male patient who presented with high-grade fever and right upper quadrant abdominal pain. Radiological findings showed a hypodense liver lesion consistent with an abscess. Fine-needle aspiration cytology (FNAC) demonstrated necrotic debris and a significant presence of CLCs, with no identifiable parasites. Laboratory investigations omitted bacterial and fungal infections, while enzyme-linked immunoassay (ELISA) identified IgG antibodies for Entamoeba histolytica. A definitive diagnosis of amoebic liver abscess was rendered, and the patient was treated successfully with metronidazole and luminal amoebicides. This case report emphasizes the diagnostic importance of CLCs in hepatic aspirates, particularly when the direct demonstration of parasites is a challenge. CLCs may provide indirect evidence of parasitic liver abscesses despite negative results from stool and cytological examinations for parasites. Effective identification and evidence-based anti-amoebic treatment are essential in endemic areas to avoid superfluous examinations for neoplastic causes.

The Effect of Mepolizumab on Blood Eosinophil Subtype Distribution and Granule Protein Gene Expression in Severe Eosinophilic Asthma

Purpose

Mepolizumab, which causes a decrease in the number of blood eosinophils, is used to treat patients with severe eosinophilic asthma (SEA). However, there is a relative lack of data on dynamic changes in blood eosinophil subtype distribution and their granule protein expression following anti-interleukin (IL)-5 treatment. Our objective was to evaluate blood inflammatory-like (iEOS-like) and resident-like (rEOS-like) eosinophil subtype distribution and CLC, EDN, EPX, ECP, and MBP gene expression following up to 24 weeks of treatment with mepolizumab in SEA patients.

Patients and Methods

Ten free of oral steroids SEA patients and 9 healthy control subjects (HS) were included. Patients were treated with mepolizumab 100 mg subcutaneously/4 weeks, and investigation tests were performed at 0, 4, 12, and 24 weeks. Blood eosinophils were isolated by Ficoll centrifugation and magnetic separation, then subtyped using magnetic separation against CD62L. Gene expression investigation was done using quantitative real time-polymerase chain reaction analysis.

Results

Approximately three-quarters of isolated blood eosinophils were iEOS-like cells before mepolizumab treatment, p<0.01. Blood eosinophil granule protein gene expression was increased in SEA patients compared to the HS, p<0.05, and iEOS-like cells EPX, MBP, and CLC gene expressions were higher than rEOS-like cells, p<0.05. Following 4, 12, and 24 weeks of treatment with mepolizumab, residual blood eosinophils shifted towards rEOS-like cells, p<0.05, and CLC, EPX, ECP, and MBP gene expression of both eosinophil subtypes decreased to HS levels.

Conclusion

Treating SEA patients with mepolizumab shifts blood eosinophil subtype distribution towards rEOS-like cells and reduces granule protein gene expression levels to those of healthy individuals.

Arginine-Rich Peptides Regulate the Pathogenic Galectin-10 Crystallization and Mitigate Crystallopathy-Associated Inflammation

Protein self-assembly into a crystal in vivo triggers acute or chronic organ injury that can lead to intractable diseases lacking specific treatment options. In this study, we report the discovery of ionic arginine-rich peptides to disrupt the pathogenic galectin-10 (gal-10) crystallization, where the aberrant deposition of gal-10 crystals in airways causes the activation of IL-1β-dependent inflammation and the stimulation of epithelial cells to produce TNF-α. Gal-10 crystals show susceptibility to pH changes and charged residue substitutions at the protein packing interfaces, manifesting the role of charge-charge attractions across protein-protein interaction interfaces in governing gal-10 crystallization. To dissolve the gal-10 crystal, the ionic peptides R9 and R12Y8 were identified to eliminate the interprotein charge-charge interactions. The efficacy of R12Y8 in mitigating the gal-10 crystallopathy in vivo was assessed in a crystal-induced lung inflammation mice model. The mice intratracheally administrated by R12Y8 exhibited a downregulated release of proinflammatory cytokines and reduced infiltration of inflammatory cells in the lungs. Our study demonstrates that the pathogenic gal-10 crystallization is readily eliminated by R-rich peptides, which may display translational potentials for the treatment of gal-10 crystallopathy.

Persistent desmoglein-1 downregulation and periostin accumulation in histologic remission of eosinophilic esophagitis

BACKGROUND

Patients with eosinophilic esophagitis (EoE) require long-lasting resolution of inflammation to prevent fibrostenosis and dysphagia. However, the dissociation between symptoms and histologic improvement suggests persistent molecular drivers despite histologic remission.

OBJECTIVE

We characterized persisting molecular alterations in pediatric patients with EoE using tissue transcriptomics and proteomics.

METHODS

Esophageal biopsy samples (n = 247) collected prospectively during 189 endoscopies from pediatric patients with EoE (n = 36, up to 11 follow-up endoscopies) and pediatric controls (n = 44, single endoscopies) were subjected to bulk transcriptomics (n = 96) and proteomics (n = 151). Intercellular junctions (desmoglein-1/3, desmoplakin, E-cadherin) and epithelial-to-mesenchymal transition (vimentin:E-cadherin ratio) were assessed by immunofluorescence staining.

RESULTS

Active EoE (≥15 eosinophils per high-power field [eos/hpf]), inactive EoE (<15 eos/hpf), and deep-remission EoE (0 eos/hpf) were diagnosed in 107 of 185, 78 of 185, and 41 of 185 biopsy samples, respectively. Among the dysregulated genes (up-/downregulated 310/112) and proteins (up-/downregulated 68/16) between active EoE and controls, 17 genes, and 6 proteins remained dysregulated in inactive EoE. Using persistently upregulated genes (n = 9) and proteins (n = 3) only, such as ALOX15, CXCL1, CXCL6, CTSG, CDH26, PRRX1, CLC, EPX, and periostin (POSTN), was sufficient to separate inactive EoE and deep-remission biopsy samples from control tissue. While 32 differentially expressed genes persisted in deep-remission EoE compared to controls, the proteome normalized except for persistently upregulated POSTN. Epithelial-to-mesenchymal transition normalized in inactive EoE, whereas desmosome recovery remained impaired as a result of desmoglein-1 downregulation.

CONCLUSION

The analysis of molecular changes shows persistent EoE-associated esophageal dysregulation despite histologic remission. These data expand our understanding of inflammatory processes and possible mechanisms that underlie tissue remodeling in EoE.

The relevance of eosinophils in chronic obstructive pulmonary disease: inflammation, microbiome, and clinical outcomes

Chronic obstructive pulmonary disease is caused by the inhalation of noxious particles such as cigarette smoke. The pathophysiological features include airway inflammation, alveolar destruction, and poorly reversible airflow obstruction. A subgroup of patients with chronic obstructive pulmonary disease has higher blood eosinophil counts, associated with an increased response to inhaled corticosteroids and increased biomarkers of pulmonary type 2 inflammation. Emerging evidence shows that patients with chronic obstructive pulmonary disease with increased pulmonary eosinophil counts have an altered airway microbiome. Higher blood eosinophil counts are also associated with increased lung function decline, implicating type 2 inflammation in progressive pathophysiology in chronic obstructive pulmonary disease. We provide a narrative review of the role of eosinophils and type 2 inflammation in the pathophysiology of chronic obstructive pulmonary disease, encompassing the lung microbiome, pharmacological targeting of type 2 pathways in chronic obstructive pulmonary disease, and the clinical use of blood eosinophil count as a chronic obstructive pulmonary disease biomarker.

IL-22 and IL-23 regulate the anticryptococcal response during Cryptococcus deuterogattii infection

Cryptococcosis is a neglected fungal disease that causes many deaths annually, is primarily caused by Cryptococcus neoformans and Cryptococcus gattii species. They are environmental fungus that engages lung pneumonia and a severe systemic infection. The rising incidence of affected immunocompetent hosts, particularly by the aggressive Cryptococcus deuterogattii (R265), underscores the urgency to understand factors influencing its dissemination. The immunopathogenesis of R265 infection is incompletely understood. Therefore, we investigate the role of IL-22 and IL-23 cytokines during R265 cryptocococcosis. Our findings highlight the crucial role of IL-22 and IL-23 cytokines in lung barrier homeostasis, preventing excessive lung damage. IL-22 not only prevents neutrophil infiltration and IL-17A production but also facilitates eosinophil lung infiltration. Ultimately, this study contributes vital insights into the selective role of IL-22 and IL-23 cytokines in immune activation and tissue regulation during the aggressive R265 lung and systemic infection.

Therapeutic relevance of eosinophilic inflammation and airway viral interactions in severe asthma

The role of eosinophils in airway inflammation and asthma pathogenesis is well established, with raised eosinophil counts in blood and sputum associated with increased disease severity and risk of asthma exacerbation. Conversely, there is also preliminary evidence suggesting antiviral properties of eosinophils in the airways. These dual roles for eosinophils are particularly pertinent as respiratory virus infections contribute to asthma exacerbations. Biologic therapies targeting key molecules implicated in eosinophil-associated pathologies have been approved in patients with severe asthma and, therefore, the effects of depleting eosinophils in a clinical setting are of considerable interest. This review discusses the pathological and antiviral roles of eosinophils in asthma and exacerbations. We also highlight the significant reduction in asthma exacerbations seen with biologic therapies, even at the height of the respiratory virus season. Furthermore, we discuss the implications of these findings in relation to the role of eosinophils in inflammation and antiviral responses to respiratory virus infection in asthma.

The NLRP3 inflammasome in allergic diseases: mechanisms and therapeutic implications

In recent years, there has been a global increase in the prevalence of allergic diseases, including allergic rhinitis, chronic rhinosinusitis, allergic asthma, atopic dermatitis, allergic conjunctivitis, and food allergies. Since the pathogenic mechanisms of these allergic diseases are not yet fully understood, targeted and effective therapies are lacking. The NLRP3 inflammasome, a multiprotein complex implicated in various inflammatory diseases, can be activated by diverse stimuli. It assembles into NLRP3 inflammasome complexes through conformational changes, initiating the proteolytic cleavage of dormant procaspase-1 into active caspase-1 and promoting the maturation of inflammatory cytokines, including IL-1β and IL-18. Dysfunction of the NLRP3 inflammasome may serve as a key driver of inflammatory diseases, leading to pyroptosis and amplifying the local inflammatory response. As preliminarily demonstrated, specific NLRP3 inflammatory vesicle inhibitors play refectory roles in animal models of allergic diseases, and it is believed that specific NLRP3 inflammasome inhibitors may be potential therapeutic agents for allergic diseases. This review highlights the progress of research on the NLRP3 inflammasome in allergic diseases, explores its contribution to different types of allergic diseases, and identifies promising clinical targets for intervention.

Plastic bronchitis linked to human bocavirus 1 identified through high-throughput next-generation sequencing: A case report

BACKGROUND

Plastic bronchitis (PB) is an uncommon and severe acute respiratory ailment characterized by the formation of casts in the trachea or bronchial tree. Some instances have been linked to human bocavirus (HBoV) infections.

CASE PRESENTATION

In this report, we present a case of PB secondary to HBoV1 infection in a previously healthy pediatric patient. A 17-month-old male was admitted due to respiratory distress following 2 days of cough and fever. A preadmission chest X-ray revealed atelectasis of the left lung. Emergency electronic bronchoscopy and foreign body forceps were employed to remove casts, leading to improved breathing. High-throughput next-generation sequencing detected only HBoV1. A subsequent electronic bronchoscopy 2 days later showed no casts.

CONCLUSIONS

PB associated with HBoV1 infection should be considered in children experiencing acute respiratory distress, and a second bronchoscopy intervention may not be necessary in cases related to HBoV1.

Monoclonal immunoglobulin crystalline nephropathies

Monoclonal Ig crystalline nephropathies are rare lesions resulting from precipitation of monoclonal Igs in the kidney as crystalline inclusions. They can be categorized into lesions with predominant intracellular crystals (light chain [LC] proximal tubulopathy, LC crystal-storing histiocytosis, and LC crystalline podocytopathy) and lesions with predominant extracellular crystals (crystalglobulin-induced nephropathy and crystalline variant of LC cast nephropathy). The majority of these lesions are associated with low tumor burden lymphoproliferative disorders, with the exception of crystalline variant of LC cast nephropathy. Extrarenal involvement (e.g., skin and cornea) is frequent. Kidney biopsy is the cornerstone for diagnosis, which often requires electron microscopy and antigen retrieval. A thorough hematologic workup and evaluation of extrarenal involvement is mandatory for management. Treatment of these lesions is with clone-directed therapy, with the goal of achieving hematologic very good partial response or complete response, which preserves or improves kidney function. In vitro and in vivo studies, animal models, and novel sequencing techniques have been invaluable tools to understand the pathogenesis of LC proximal tubulopathy and can be used to increase our limited knowledge of the pathogenesis of the other monoclonal Ig crystalline nephropathies. This review provides an update on the pathology, renal and hematologic characteristics, extrarenal manifestations, prognosis, treatment, and pathogenesis of monoclonal Ig crystalline nephropathies.

Eosinophilic mucus diseases

Eosinophilic inflammation is primarily characterized by type 2 immune responses against parasitic organisms. In the contemporary human being especially in developed countries, eosinophilic inflammation is strongly associated with allergic/sterile inflammation, and constitutes an undesired immune reaction. This situation is in stark contrast to neutrophilic inflammation, which is indispensable for the host defense against bacterial infections. Among eosinophilic inflammatory disorders, massive accumulation of eosinophils within mucus is observed in certain cases, and is often linked to the distinctive clinical finding of mucus with high viscosity. Eosinophilic mucus is found in a variety of diseases, including chronic allergic keratoconjunctivitis, chronic rhinosinusitis encompassing allergic fungal sinusitis, eosinophilic otitis media, eosinophilic sialodochitis, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic plastic bronchitis, and eosinophilic asthma. In these pathological conditions, chronic inflammation and tissue remodeling coupled with irreversible organ damage due to persistent adhesion of toxic substances and luminal obstruction may impose a significant burden on the body. Eosinophils aggregate in the hyperconcentrated mucus together with cell-derived crystals, macromolecules, and polymers, thereby affecting the biophysical properties of the mucus. This review focuses on the clinically significant challenges of mucus and discusses the consequences of activated eosinophils on the mucosal surface that impact mucus and persistent inflammation.

Eosinophil-mucus interplay in severe asthma: Implications for treatment with biologicals

Airway mucus is a hydrogel with unique biophysical properties due to its primary water composition and a small proportion of large anionic glycoproteins or mucins. The predominant mucins in human mucus, MUC5AC and MUC5B, are secreted by specialized cells within the airway epithelium both in normal conditions and in response to various stimuli. Their relative proportions are correlated with specific inflammatory responses and disease mechanisms. The dysregulation of mucin expression is implicated in numerous respiratory diseases, including asthma, COPD, and cystic fibrosis, where the pathogenic role of mucus has been extensively described yet often overlooked. In airway diseases, excessive mucus production or impaired mucus clearance leads to mucus plugging, with secondary airway occlusion that contribute to airflow obstruction, asthma severity and poor control. Eosinophils and Charcot Leyden crystals in sputum contribute to the mucus burden and tenacity. Mucin may also contribute to eosinophil survival. Other mechanisms, including eosinophil-independent IL-13 release, mast-cell activation and non-type-2 (T2) cytokines, are also likely to participate in mucus pathobiology. An accurate assessment of mucus and its clinical and functional consequences require a thorough approach that includes evaluation of cellular predominance in sputum, airway cytokines and other inflammatory markers, mucus characteristics and composition and structural and functional impact measured by advanced lung imaging. This review, illustrated with clinical scenarios, provides an overview of current methods to assess mucus and its relevance to the choice of biologics to treat patients with severe asthma.

Aggregated eosinophils and neutrophils characterize the properties of mucus in chronic rhinosinusitis

BACKGROUND

Airway obstruction caused by viscous mucus is an important pathophysiologic characteristic of persistent inflammation, which can result in organ damage.

OBJECTIVE

We investigated the hypothesis that the biophysical characteristics of accumulating granulocytes affect the clinical properties of mucus.

METHODS

Surgically acquired nasal mucus samples from patients with eosinophilic chronic rhinosinusitis and neutrophil-dominant, noneosinophilic chronic rhinosinusitis were evaluated in terms of computed tomography density, viscosity, water content, wettability, and protein composition. Isolated human eosinophils and neutrophils were stimulated to induce the formation of extracellular traps, followed by the formation of aggregates. The biophysical properties of the aggregated cells were also examined.

RESULTS

Mucus from patients with eosinophilic chronic rhinosinusitis had significantly higher computed tomography density, viscosity, dry weight, and hydrophobicity compared to mucus from patients with noneosinophilic chronic rhinosinusitis. The levels of eosinophil-specific proteins in mucus correlated with its physical properties. Eosinophil and neutrophil aggregates showed physical and pathologic characteristics resembling those of mucus. Cotreatment with deoxyribonuclease and heparin, which slenderizes the structure of eosinophil extracellular traps, efficiently induced reductions in the viscosity and hydrophobicity of both eosinophil aggregates and eosinophilic mucus.

CONCLUSIONS

The present study elucidated the pathogenesis of mucus stasis in infiltrated granulocyte aggregates from a novel perspective. These findings may contribute to the development of treatment strategies for eosinophilic airway diseases.

Galectin-10 in serum extracellular vesicles reflects asthma pathophysiology

BACKGROUND

Novel biomarkers (BMs) are urgently needed for bronchial asthma (BA) with various phenotypes and endotypes.

OBJECTIVE

We sought to identify novel BMs reflecting tissue pathology from serum extracellular vesicles (EVs).

METHODS

We performed data-independent acquisition of serum EVs from 4 healthy controls, 4 noneosinophilic asthma (NEA) patients, and 4 eosinophilic asthma (EA) patients to identify novel BMs for BA. We confirmed EA-specific BMs via data-independent acquisition validation in 61 BA patients and 23 controls. To further validate these findings, we performed data-independent acquisition for 6 patients with chronic rhinosinusitis without nasal polyps and 7 patients with chronic rhinosinusitis with nasal polyps.

RESULTS

We identified 3032 proteins, 23 of which exhibited differential expression in EA. Ingenuity pathway analysis revealed that protein signatures from each phenotype reflected disease characteristics. Validation revealed 5 EA-specific BMs, including galectin-10 (Gal10), eosinophil peroxidase, major basic protein, eosinophil-derived neurotoxin, and arachidonate 15-lipoxygenase. The potential of Gal10 in EVs was superior to that of eosinophils in terms of diagnostic capability and detection of airway obstruction. In rhinosinusitis patients, 1752 and 8413 proteins were identified from EVs and tissues, respectively. Among 11 BMs identified in EVs and tissues from patients with chronic rhinosinusitis with nasal polyps, 5 (including Gal10 and eosinophil peroxidase) showed significant correlations between EVs and tissues. Gal10 release from EVs was implicated in eosinophil extracellular trapped cell death in vitro and in vivo.

CONCLUSION

Novel BMs such as Gal10 from serum EVs reflect disease pathophysiology in BA and may represent a new target for liquid biopsy approaches.

Eosinophil extracellular traps in eosinophilic chronic rhinosinusitis induce Charcot-Leyden crystal formation and eosinophil recruitment

Eosinophil extracellular traps (EETs) are implicated in various eosinophil-associated diseases; however, their role in chronic rhinosinusitis (CRS) remains unclear. In the present study, 57 CRS patients were enrolled, and immunofluorescence was used to analyze EETs in eosinophilic (eCRS) and non-eosinophilic (Non-eCRS) tissues. MSD was used to examine IL-4, IL-5, and IL-13 concentrations in tissue homogenates. Charcot-Leyden crystals (CLCs) protein expression was detected in PMA, PMA+DNase I, and blank control eosinophils using ELISA. Eotaxin-3 mRNA and protein levels were measured in human nasal epithelial cells (HNECs) cultured with EETs, EETs+DNase I, DNase I, and unstimulated eosinophils using PCR and ELISA. EETs were significantly increased in eCRS tissues compared with Non-eCRS (P<0.001), and correlated with VAS and Lund-Mackay CT scores. IL-5 expression was related to EETs formation (r = 0.738, P<0.001). PMA-stimulated eosinophils exhibited higher CLCs protein levels (P<0.01). Co-culturing HNECs with EETs significantly increased eotaxin-3 mRNA and protein levels (P<0.0001, P<0.001) compared with other groups. The study suggests EETs formation is elevated in eCRS patients and is involved in CLCs formation and chemokine secretion, promoting eosinophilic inflammation.

Mucus plugs in the airways of asthmatic subjects and smoking status

BACKGROUND

Mucus plugs have been described in the airways of asthmatic subjects, particularly those with associated with type 2 inflammation and sputum eosinophilia. In the current study we addressed the question of whether smoking, neutrophilic inflammation and airway dimensions affected the prevalence of mucus plugs.

METHODS

In a cohort of moderate to severe asthmatics (n = 50), including a group of ex-smokers and current smokers, the prevalence of mucus plugs was quantified using a semi-quantitative score based on thoracic computerized tomography. The relationships between mucus score, sputum inflammatory profile and airway architecture were tested according to patient's smoking status.

RESULTS

Among the asthmatics (37% former or active smokers), 74% had at least one mucus plug. The median score was 3 and was unrelated to smoking status. A significant but weak correlation was found between mucus score, FEV1 and FEV1/FVC. Mucus score was significantly correlated with sputum eosinophils. Among former and active smokers, mucus score was correlated with sputum neutrophils. Mucus score was positively associated with FeNO in non-smoking subjects. The lumen dimensions of the main and lobar bronchi were significantly inversely correlated with mucus score.

CONCLUSION

Airway mucus plugs could define an asthma phenotype with altered airway architecture and can occur in asthmatic subjects with either neutrophilic or eosinophilic sputum according to their smoking status.

Eosinophils-from cradle to grave: An EAACI task force paper on new molecular insights and clinical functions of eosinophils and the clinical effects of targeted eosinophil depletion

Over the past years, eosinophils have become a focus of scientific interest, especially in the context of their recently uncovered functions (e.g. antiviral, anti-inflammatory, regulatory). These versatile cells display both beneficial and detrimental activities under various physiological and pathological conditions. Eosinophils are involved in the pathogenesis of many diseases which can be classified into primary (clonal) and secondary (reactive) disorders and idiopathic (hyper)eosinophilic syndromes. Depending on the biological specimen, the eosinophil count in different body compartments may serve as a biomarker reflecting the underlying pathophysiology and/or activity of distinct diseases and as a therapy-driving (predictive) and monitoring tool. Personalized selection of an appropriate therapeutic strategy directly or indirectly targeting the increased number and/or activity of eosinophils should be based on the understanding of eosinophil homeostasis including their interactions with other immune and non-immune cells within different body compartments. Hence, restoring as well as maintaining homeostasis within an individual's eosinophil pool is a goal of both specific and non-specific eosinophil-targeting therapies. Despite the overall favourable safety profile of the currently available anti-eosinophil biologics, the effect of eosinophil depletion should be monitored from the perspective of possible unwanted consequences.

Frequency of strongyloidiasis and associated factors: Analysis of 13 years of laboratory results in a tertiary referral hospital in Honduras, 2010-2022

INTRODUCTION

The frequency of detected strongyloidiasis is affected by the selected laboratory method in the studied population. Considering that Honduras has few community-based studies, the analysis of the laboratory record data can provide information helping to understand this parasitosis.

OBJECTIVE

To estimate the frequency and to identify the factors associated with strongyloidiasis, analyzing the laboratory records of the Servicio de Parasitología at Hospital Escuela in Tegucigalpa (Honduras) between 2010 and 2022.

MATERIALS AND METHODS

We carried out a descriptive, cross-sectional, analytical study. The laboratory diagnosis consisted of stool samples' examination by direct smear and modified Baermann technique. We estimated frequencies and percentages. The statistical association was calculated with prevalence ratios and a 95% confidence interval. Software R, version 4.2.0, and epiR package, version 2.0.46, were used to perform the analysis.

RESULTS

The frequency of strongyloidiasis was 0.29% (112/38,085). It was higher with the modified Baermann technique (0.87%; 40/4,575) among male patients (0.44%; 70/15,758). Regarding the age, strongyloidiasis was higher in the 20-40 years old group (0.41%; 28/6,886) with direct smear and 41-61 years old (1.14%; 14/1,232) group with the modified Baermann technique. Among the factors associated with strongyloidiasis were age between 20 and 61 years old (PR=2.26, CI 95%=1.53-3.31), male patients (PR=2.34, CI 95%=1.60‑3.44), mucus (PR=1.86, CI 95%=1.22-2.83) and Charcot-Leyden crystals in stool (PR=8.47, CI 95%=5.14-13.96); watery stool (PR=2.39, CI 95%=1.55-3.68), and other helminthiases (PR=6.73, CI 95%=3.98-11.38). Associated factors to cases detected with the modified Baermann technique were outpatient consultation (PR=4.21, CI 95%=1.91-9.28) and formed stools (PR=3.99, CI 95%=1.94-8.19).

CONCLUSIONS

The modified Baermann technique increased the detection of strongyloidiasis almost four times. Most cases were distributed among male adults. The cases diagnosed exclusively with the modified Baermann technique have differences from those with observed larvae in the direct smear. It is necessary to develop community-based population studies.

Eosinophilic plastic bronchitis: Case series and review of the literature

Plastic bronchitis is a term used to describe group of life-threatening disorders characterized by the presence of large obstructing casts in the airways. Eosinophilic plastic bronchitis is a subtype of plastic bronchitis that occurs mainly in children and has not been well-described in the literature. Patients may have a history of asthma or atopy, but many do not. They often present with cough and wheezing, and frequently have complete collapse of one lung seen on imaging. The severity of presentation varies depending on the location of the casts, ranging from mild symptoms to severe airway obstruction and death. Bronchoscopy is often required to both diagnose and treat this condition. A variety of medical therapies have been used, although no formal studies have evaluated their efficacy. Symptoms may resolve after initial cast removal, but in some patients, cast formation recurs. Here, we report a case series of nine patients with eosinophilic plastic bronchitis and review the existing literature of this condition.

Eosinophil-derived galectin-10 upregulates matrix metalloproteinase expression in bullous pemphigoid blisters

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune bullous disease in which abundant eosinophils accumulate in the blisters. Galectin-10 abounds in the cytoplasm of eosinophils and is released as a result of eosinophil extracellular trap cell death (EETosis).

OBJECTIVE

To identify EETosis and the pathological roles of galectin-10 in BP.

METHODS

EETosis and galectin-10 in BP blisters were confirmed by immunofluorescence and transmission electron microscopy. The concentrations of galectin-10 in serum and blister fluid from BP patients were studied by ELISA. The matrix metalloproteinase (MMP) expression in BP blisters was immunohistochemically compared to that in healthy controls. As an in vitro assay, normal human epidermal keratinocytes (NHEKs) and normal human dermal fibroblasts (NHDFs) were stimulated with galectin-10, followed by MMP expression measurement by real-time PCR and ELISA. The signaling pathways activated by galectin-10 were studied using Western blotting and confirmed by inhibition assays.

RESULTS

Galectin-10-containing eosinophil infiltration and the extracellular deposition of major basic protein were observed in BP blisters. The ultrastructural characteristics of tissue eosinophils indicated piecemeal degranulation and EETosis. In the BP patients, the concentration of galectin-10 was higher in the blister fluid than in the serum. Several types of MMPs were upregulated in BP blisters. Galectin-10 upregulated the production of MMPs through the pathways of p38 MAPK, ERK and JNK in NHEKs and NHDFs.

CONCLUSION

In the BP blisters, the eosinophils underwent EETosis and released galectin-10. Galectin-10 might contribute to BP blister formation through the production of MMPs by keratinocytes and fibroblasts.

The effects of benralizumab on airway geometry and dynamics in severe eosinophilic asthma: a single-arm study design exploring a functional respiratory imaging approach

BACKGROUND

Severe eosinophilic asthma (SEA) is characterised by elevated blood/sputum eosinophil counts and airway inflammation, which can lead to mucus plug-mediated airway obstruction, increased exacerbation frequency, declines in lung function, and death. Benralizumab targets the alpha-subunit of the interleukin-5 receptor found on eosinophils, leading to rapid and near complete eosinophil depletion. This is expected to result in reduced eosinophilic inflammation, reduced mucus plugging and improved airway patency and airflow distribution.

METHODS

BURAN is an interventional, single-arm, open-label, uncontrolled, prospective, multicentre study during which participants will receive three 30 mg subcutaneous doses of benralizumab at 4-week intervals. This study will use functional respiratory imaging (FRI), a novel, quantitative method of assessing patients' lung structure and function based on detailed, three-dimensional models of the airways, with direct comparison of images taken at Weeks 0 and 13. Patients aged ≥ 18 years with established SEA who may be receiving oral corticosteroids and/or other asthma controller medications, who are inadequately controlled on inhaled corticosteroid-long-acting β2-agonist therapies and who have had ≥ 2 asthma exacerbations in the previous 12 months will be included. The objectives of BURAN are to describe changes in airway geometry and dynamics, measured by specific image-based airway volume and other FRI endpoints, following benralizumab therapy. Outcomes will be evaluated using descriptive statistics. Changes in FRI parameters, mucus plugging scores and central/peripheral ratio will be quantified as mean percent change from baseline (Week 0) to Week 13 (± 5 days) and statistical significance will be evaluated using paired t-tests. Relationships between FRI parameters/mucus plugging scores and conventional lung function measurements at baseline will be assessed with linear regression analyses for associations between outcomes, scatterplots to visualise the relationship, and correlation coefficients (Spearman's rank and Pearson's) to quantify the strength of these associations.

CONCLUSIONS

The BURAN study will represent one of the first applications of FRI-a novel, non-invasive, highly sensitive method of assessing lung structure, function and health-in the field of biologic respiratory therapies. Findings from this study will increase understanding of cellular-level eosinophil depletion mechanisms and improvements in lung function and asthma control following benralizumab treatment. Trial registration EudraCT: 2022-000152-11 and NCT05552508.

Charcot-Leyden crystals: An ancient but never so current discovery

From the first description of Charcot-Leyden crystals (CLCs) to the present, many steps have been taken to understand the mechanisms underlying their formation. In particular, to date not only eosinophils but also mast cells are known to be responsible for the production of CLCs, which represent the crystallized form of Galectin-10. Due to their characteristics, CLCs typically induce a crystallopathy and are responsible for an exacerbation of inflammation. Nasal cytology (NC) has allowed to better understand the correlation between the severity of several rhinopaties and the presence of CLCs in NC samples, which is strictly correlated with an eosinophiles and mast cells infiltration. As a matter of fact, rhinopaties with a mixed eosinophilic-mast cell inflammatory infiltrate, characterized by the presence of abundant CLCs, show a worse prognosis and a higher risk of relapse. This could have important therapeutic implications, since the treatments available today could be exploited to target both eosinophils and mast cells, to reduce the damage induced by CLCs.

Bronchiectasis in severe asthma is associated with eosinophilic airway inflammation and activation

Background

Bronchiectasis is a common comorbidity in severe asthma; causative pathogenic mechanisms are not fully understood but may differ from other causes of bronchiectasis. The role of eosinophilic airway inflammation, a classic feature of asthma predominantly driven by IL-5 and IL-13, in bronchiectasis is unclear, but association with disruption of the airway epithelium through eosinophil degranulation and increased mucus production is plausible.

Objective

We sought to describe the prevalence of bronchiectasis in an unselected population of patients with severe asthma, and the association with the airway eosinophilic inflammation and activation.

Methods

All patients with severe asthma according to European Respiratory Society/American Thoracic Society criteria (high-dose inhaled corticosteroids/oral corticosteroids), attending 4 respiratory clinics over a 1-year period, were included. All patients underwent high-resolution computed tomography and induced sputum was collected and analyzed for a cell differential count, free eosinophilic granules, and airway messenger RNA expression of T2 inflammatory pathways.

Results

Bronchiectasis was present in 31% (34 of 108) of patients with severe asthma, and half (52%) of these patients had airway eosinophilia whereas only 16% of patients without bronchiectasis had airway eosinophilia. Patients with bronchiectasis had a significantly higher sputum eosinophil count (5.3 vs 0.8; P = .001) as well as more extensive eosinophil degranulation, compared with those without bronchiectasis (13% vs 2%; P = .05), suggesting a higher degree of eosinophil activation. Pairwise analyses identified significantly higher messenger RNA expression of Charcot-Leyden crystal galectin in patients with bronchiectasis (P = .02).

Conclusions

Bronchiectasis in severe asthma was associated with eosinophilic airway inflammation and eosinophilic degranulation as well as messenger RNA expression of Charcot-Leyden crystal galectin.

Airway autoimmunity, asthma exacerbations, and response to biologics

Biologic therapies in asthma are indicated in severe disease, and they are directed against specific inflammatory modulators that contribute to pathogenesis and severity. Currently approved biologics target T2 cytokines (IgE, IL-5, IL-4/IL-13, and TLSP) and have demonstrated efficacy in clinical outcomes such as exacerbation rate and oral corticosteroid dose reductions, blood and airway eosinophil depletion, and lung function improvement. However, a proportion of these patients may show inadequate responses to biologics, with either initial lack of improvement or clinical and functional worsening after an optimal initial response. Exacerbations while on a biologic may be due to several reasons, including imprecise identification of the dominant effector pathway contributing to severity, additional inflammatory pathways that are not targeted by the biologic, inaccuracies of the biomarker used to guide therapy, inadequate dosing schedules, intercurrent airway infections, anti-drug neutralizing antibodies, and a novel phenomenon of autoimmune responses in the airways interfering with the effectiveness of the monoclonal antibodies. This review, illustrated using case scenarios, describes the underpinnings of airway autoimmune responses in driving exacerbations while patients are being treated with biologics, device a strategy to evaluate such exacerbations, an algorithm to switch between biologics, and perhaps to consider two biologics concurrently.

Predictive significance of Charcot-Leyden crystal structures for nasal polyp recurrence

BACKGROUND

Charcot-Leyden crystals (CLCs) are recognized to be classic hallmarks of eosinophilic inflammation. Both protein and mRNA levels of CLC in nasal secretions and nasal brushing samples have been associated with nasal polyp recurrence. However, whether the crystalline CLC structures in nasal tissue could serve as an effective biomarker to predict polyp recurrence remains unclear.

METHODS

A total of 110 patients with chronic rhinosinusitis with nasal polyps (CRSwNP) completing the postoperative follow-up over a period of 24 months were recruited. Hematoxylin and eosin staining was employed for CLCs identification. The predictive factors for polyp recurrence were determined by binary logistic regression analysis.

RESULTS

Thirty three (30.00%) patients developed recurrence during a 24-month postoperative follow-up, in which 84.85% (28/33) patients had crystalline CLC structures. Logistic regression analysis showed that crystalline CLC structure in nasal tissues is predictive of polyp recurrence. Youden index demonstrated crystalline CLC structure higher than 1 per high power field can predict postoperative polyp recurrence with 84.80% sensitivity and 98.70% specificity.

CONCLUSIONS

The crystalline CLC structures in nasal tissues may serve as an easy-counting and promising biomarker to predict CRSwNP recurrence.

Proposal for Structured Histopathology of Nasal Secretions for Endotyping Chronic Rhinosinusitis: An Exploratory Study

Background: The EPOS guidelines promote cellular analysis as a primary goal in endotyping chronic rhinosinusitis (CRS). Current analysis is mainly based on biopsy or operative tissue collection, whereas the use of sinonasal secretions for inflammatory endotyping is not advocated in clinical practice. Early endotyping is crucial though, especially regarding the increasing evidence of patient-tailored therapy. We aimed to investigate the diagnostic value and reproducibility of sinonasal secretions sampling. Methods: First, preoperative secretion analysis of 53 Caucasian CRS patients was compared to subsequent operative tissue analysis. Second, secretion analysis at two different time points was compared for 10 postoperative Caucasian CRS patients with type 2 (T2) inflammation and 10 control participants. Secretions were collected by both endoscopic aspiration and nasal blown secretions in all participants. Results: The sensitivity to detect T2 inflammation was higher in nasal aspiration samples (85%) compared to nasal blow secretions (32%). A specificity of 100% for both techniques was obtained. A 90% reproducibility for T2 eosinophil detection was found by sampling at different time points regardless of the technique. Of the T2 patients, 60% showed no T2 inflammatory pattern more than one year after endoscopic sinus surgery. Conclusions: Nasal secretion sampling, especially aspiration of nasal secretions, is useful in the detection of T2 inflammation in CRS pathology. We proposed a structured histopathology analysis to be useful in daily clinical practice, which includes Congo red staining sensitive for eosinophilic cells and free eosinophil granules. Analysis of nasal secretions enables endotyping in an early stage, allowing more directed therapy.

Galectin-10 as a Potential Biomarker for Eosinophilic Diseases

Galectin-10 is a member of the lectin family and one of the most abundant cytoplasmic proteins in human eosinophils. Except for some myeloid leukemia cells, basophils, and minor T cell populations, galectin-10 is exclusively present in eosinophils in the human body. Galectin-10 forms Charcot–Leyden crystals, which are observed in various eosinophilic diseases. Accumulating studies have indicated that galectin-10 acts as a new biomarker for disease activity, diagnosis, and treatment effectiveness in asthma, eosinophilic esophagitis, rhinitis, sinusitis, atopic dermatitis, and eosinophilic granulomatosis with polyangiitis. The extracellular release of galectin-10 is not mediated through conventional secretory processes (piecemeal degranulation or exocytosis), but rather by extracellular trap cell death (ETosis), which is an active cell death program. Eosinophils undergoing ETosis rapidly disintegrate their plasma membranes to release the majority of galectin-10. Therefore, elevated galectin-10 levels in serum and tissue suggest a high degree of eosinophil ETosis. To date, several studies have shown that galectin-10/Charcot–Leyden crystals are more than just markers for eosinophilic inflammation, but play functional roles in immunity. In this review, we focus on the close relationship between eosinophils and galectin-10, highlighting this protein as a potential new biomarker in eosinophilic diseases.

The regulatory role of eosinophils in viral, bacterial, and fungal infections

Eosinophils are innate immune cells typically associated with allergic and parasitic diseases. However, in recent years, eosinophils have also been ascribed a role in keeping homeostasis and in fighting several infectious diseases. Indeed, these cells circulate as mature cells in the blood and can be quickly recruited to the infected tissue. Moreover, eosinophils have all the necessary cellular equipment such as pattern recognition receptors (PRRs), pro-inflammatory cytokines, anti-bacterial proteins, and DNA traps to fight pathogens and promote an efficient immune response. This review summarizes some of the updated information on the role of eosinophils' direct and indirect mediated interactions with pathogens.

Crystalline State Determines the Potency of Galectin-10 Protein Assembly to Induce Inflammation

Protein crystallization is a prevalent phenomenon existing in the formation of intricate protein-assembled structures in living cells. Whether the crystallization of a protein would exert a specific biological function, however, remains poorly understood. Here, we reconstructed a recombinant galectin-10 (gal-10) protein and artificially engineered a gal-10 protein assembly in two distinguishable states: i.e., an insoluble crystalline state and a soluble state. The potency of the gal-10 protein in either the crystalline state or the soluble state to induce chemokine or cytokine release in the primary human nasal epithelial cells and nasal polyps derived from chronic rhinosinusitis patients with nasal polyps was investigated. The crystalline gal-10 upregulated the gene expression of chemokines or cytokines, including IL-1β, IL-6, IL-8, TNF-α, and GM-CSF, in patient-derived primary cells and nasal polyps. In contrast, soluble gal-10 displayed a diminished potency to induce inflammation. Our results demonstrate that the gal-10 protein potency of activating inflammation is correlated with its crystalline state.

A sputum 6-gene signature predicts airway inflammation endotypes and exacerbation frequency in chronic obstructive pulmonary disease

Aim: To validate a sputum 6-gene signature (6GS), comprising of CLC, CPA, DNASE1L3, IL-1B, ALPL and CXCR2, for identifying different endotypes in chronic obstructive pulmonary disease. Methodology & results: Sputum cell CLC, CPA3 and DNASE1L3 gene expression correlated with eosinophil percentage, while IL-1B, ALPL and CXCR2 correlated with neutrophil percentage. Hierarchical cluster analyses of IL-1B, ALPL and CXCR2, and CLC, CPA3 and DNASE1L3, identified patient groups that differed in their sputum neutrophil and eosinophil levels, respectively. Multiple logistic regressions demonstrated that the 6GS could distinguish between eosinophil^High and eosinophil^Low patients, as well as neutrophil^High and neutrophil^Low, and could also predict exacerbation history. Conclusion: The 6GS may have applications in clinical practice or for stratifying patients for clinical trials.

Effects of Therapeutic Antibodies on Gene and Protein Signatures in Asthma Patients: A Comparative Systematic Review

Several biologic therapies that target inflammatory modulators are now used for treating patients with uncontrolled, severe asthma. Knowledge about how this type of treatment modifies the molecular milieu is rapidly increasing. Thus, this systematic review aimed to compile the reported effects of therapeutic antibodies on the transcriptome or proteome of asthma patients. Studies of asthmatic patients under biological treatment describing transcriptomic or proteomic changes upon treatment were included. Preclinical or single gene/protein studies were not considered. PubMed and Scopus search was performed in August and September 2021. Following PRISMA guidelines and GRADE recommendations, we selected 12 studies on gene or protein expression changes in patients treated with the antibodies currently approved by EMA and the FDA. All studies were at low risk of bias as per the RoB2 tool. Different gene clusters have been identified to change upon omalizumab treatment, found a reduction in eosinophil-associated gene signatures after benralizumab treatment, and protein profiles were different in patients treated with mepolizumab and in those treated with benralizumab. The main potential biomarkers proposed by the selected studies are shown. These results may contribute to discovering biomarkers of response and selecting the best therapy for each patient.

Enhancing Human Superorganism Ecosystem Resilience by Holistically ‘Managing Our Microbes’

Microbes in the 21st century are understood as symbionts ‘completing’ the human ‘superorganism’ (Homo sapiens plus microbial partners-in-health). This paper addresses a significant paradox: despite the vast majority of our genes being microbial, the lack of routine safety testing for the microbiome has led to unintended collateral side effects from pharmaceuticals that can damage the microbiome and inhibit innate ‘colonization resistance’ against pathobionts. Examples are discussed in which a Microbiome First Medicine approach provides opportunities to ‘manage our microbes’ holistically, repair dysbiotic superorganisms, and restore health and resilience in the gut and throughout the body: namely, managing nosocomial infections for Clostridioides difficile and Staphylococcus aureus and managing the gut and neural systems (gut–brain axis) in autism spectrum disorder. We then introduce a risk analysis tool: the evidence map. This ‘mapping’ tool was recently applied by us to evaluate evidence for benefits, risks, and uncertainties pertaining to the breastmilk ecosystem. Here, we discuss the potential role of the evidence map as a risk analysis methodology to guide scientific and societal efforts to: (1) enhance ecosystem resilience, (2) ‘manage our microbes’, and (3) minimize the adverse effects of both acute and chronic diseases.

Eosinophils and Bacteria, the Beginning of a Story

Eosinophils are granulocytes primarily associated with TH2 responses to parasites or immune hyper-reactive states, such as asthma, allergies, or eosinophilic esophagitis. However, it does not make sense from an evolutionary standpoint to maintain a cell type that is only specific for parasitic infections and that otherwise is somehow harmful to the host. In recent years, there has been a shift in the perception of these cells. Eosinophils have recently been recognized as regulators of immune homeostasis and suppressors of over-reactive pro-inflammatory responses by secreting specific molecules that dampen the immune response. Their role during parasitic infections has been well investigated, and their versatility during immune responses to helminths includes antigen presentation as well as modulation of T cell responses. Although it is known that eosinophils can present antigens during viral infections, there are still many mechanistic aspects of the involvement of eosinophils during viral infections that remain to be elucidated. However, are eosinophils able to respond to bacterial infections? Recent literature indicates that Helicobacter pylori triggers TH2 responses mediated by eosinophils; this promotes anti-inflammatory responses that might be involved in the long-term persistent infection caused by this pathogen. Apparently and on the contrary, in the respiratory tract, eosinophils promote TH17 pro-inflammatory responses during Bordetella bronchiseptica infection, and they are, in fact, critical for early clearance of bacteria from the respiratory tract. However, eosinophils are also intertwined with microbiota, and up to now, it is not clear if microbiota regulates eosinophils or vice versa, or how this connection influences immune responses. In this review, we highlight the current knowledge of eosinophils as regulators of pro and anti-inflammatory responses in the context of both infection and naïve conditions. We propose questions and future directions that might open novel research avenues in the future.

Mepolizumab decreased the levels of serum galectin-10 and eosinophil cationic protein in asthma

Background

Mepolizumab, a humanized antibody targeting interleukin-5, decreases the number of blood eosinophils and the frequency of exacerbation of severe asthma. Galectin-10 is a protein within the cytoplasm of eosinophils and constitutes Charcot-Leyden crystals, which promotes key features of asthma. However, the relationship between time kinetics and clinical response of eosinophil-derived molecules such as galectin-10 or eosinophil cationic protein (ECP) has not been precisely investigated.

Objective

This study aimed to clarify the precise time course of the levels of serum galectin-10 and ECP after mepolizumab treatment and to analyze the relationship between the levels of eosinophil-derived molecules and the clinical background or response to mepolizumab treatment.

Methods

This multicenter, prospective open-label study recruited 20 patients with severe eosinophilic asthma. Mepolizumab was administered every 4 weeks for 32 weeks and the levels of various biomarkers were serially analyzed.

Results

The serum galectin-10 and ECP significantly and rapidly decreased 4 weeks after initial administration of mepolizumab. In contrast, basophil count, fractional exhaled nitric oxide, and the serum total IgE level were unchanged during treatment. Asthma Control Questionnaire-5, Asthma Health Questionnaire-33, and Lund-Mackay scores significantly improved after mepolizumab treatment. Both high ECP and eosinophil count related to better response in forced expiratory volume in 1 second (FEV₁) and measurable ECP level at 4 weeks after administration of mepolizumab related to the further improvement in FEV₁ toward week 32. No significant difference in improvement in FEV₁ was observed in galectin-10 high group. The level of ECP at baseline was significantly related to the higher prevalence of nasal polyp and Lund-Mackay score.

Conclusion

This study was the first to show that the levels of serum galectin-10 decreases after initial administration of mepolizumab. The significant relationship between serum ECP and better response in FEV₁ suggested the potential role of serum ECP as a predictive biomarker for the efficacy of mepolizumab (UMIN000030466).

Underestimation of airway luminal eosinophilia by quantitative sputum cytometry

RATIONALE

On Wright-stained sputum cytospins, eosinophil differential of ≥ 1.2% is considered abnormal, and ≥ 2.3% identifies an eosinophilic endotype. We hypothesized that failure to consider free eosinophil granules (FEG), and the re-emergence (unmasking) of eosinophilia due to various reasons underestimate the prevalence of the eosinophilic endotype.

METHODS

This is a retrospective analysis of our Institutional Review Board-approved clinical sputum database. Of the 24,176 examinations of sputa from patients with various airway diseases, 17,693 were viable cell counts from 9570 patients (6604 on a single occasion, 2967 from multiple occasions). The prevalence of intact eosinophil % at 1.2 and 2.3% thresholds was first examined. Then, additional evidence of eosinophilia was assessed by semi-quantitative enumeration of FEGs. In those patients whose sputa were examined on multiple occasions (at the time of an exacerbation or after corticosteroid dose was reduced), re-emergence (unmasking) of eosinophilia was assessed .

RESULTS

Using the threshold of eosinophilia ≥ 1.2%, 6289/17693 (35.6%) of sputa were classified as eosinophilic. This increased to 7850/17693 (44.4%) when the presence of FEGs was considered. Using the threshold of eosinophilia ≥ 2.3%, 4647/17693 (26.3%) of sputa were classified as eosinophilic. This increased to 5435/17693 (30.7%) when the presence of FEG were considered. Extrapolating from the prevalence of re-emergence observed in the 2967 patients who had sputa examined on multiple occasions to the whole sample, we estimated that eosinophilia at 1.2% threshold would be observed in at least 60% of the samples, and a clinically relevant eosinophilia at 2.3% threshold would be observed in at least 48.5% of the samples.

CONCLUSIONS

Using a large sputum cytometry clinical database (17,693 viable cell counts), we demonstrate that a single time point intact cell count underestimates the prevalence of eosinophilia in a variety of airway diseases. The prevalence of eosinophilia increases from 35.6 to 60% (40% underestimation) at the 1.2% threshold, and from 26.3 to 48.5% (45% underestimation) at the 2.3% clinically relevant threshold, when free granules and a second examination are considered. This has important implications to identify the eosinophilic and Th2 high endotype both for clinical trials of anti-eosinophil therapies, and to select patients who may respond well to glucocorticosteroids and anti-IL5 therapies.

Emerging Evidence for Pleiotropism of Eosinophils

Eosinophils are complex granulocytes with the capacity to react upon diverse stimuli due to their numerous and variable surface receptors, which allows them to respond in very different manners. Traditionally believed to be only part of parasitic and allergic/asthmatic immune responses, as scientific studies arise, the paradigm about these cells is continuously changing, adding layers of complexity to their roles in homeostasis and disease. Developing principally in the bone marrow by the action of IL-5 and granulocyte macrophage colony-stimulating factor GM-CSF, eosinophils migrate from the blood to very different organs, performing multiple functions in tissue homeostasis as in the gastrointestinal tract, thymus, uterus, mammary glands, liver, and skeletal muscle. In organs such as the lungs and gastrointestinal tract, eosinophils are able to act as immune regulatory cells and also to perform direct actions against parasites, and bacteria, where novel mechanisms of immune defense as extracellular DNA traps are key factors. Besides, eosinophils, are of importance in an effective response against viral pathogens by their nuclease enzymatic activity and have been lately described as involved in severe acute respiratory syndrome coronavirus SARS-CoV-2 immunity. The pleiotropic role of eosinophils is sustained because eosinophils can be also detrimental to human physiology, for example, in diseases like allergies, asthma, and eosinophilic esophagitis, where exosomes can be significant pathophysiologic units. These eosinophilic pathologies, require specific treatments by eosinophils control, such as new monoclonal antibodies like mepolizumab, reslizumab, and benralizumab. In this review, we describe the roles of eosinophils as effectors and regulatory cells and their involvement in pathological disorders and treatment.

Emerging role of galectin family in inflammatory autoimmune diseases

Galectin family is a group of glycan-binding proteins. Members in this family are expressed in different tissues, immune or non-immune cells. These molecules are important regulators in innate and adaptive immune response, performing significantly in a broad range of cellular and pathophysiological functions, such as cell proliferation, adhesion, migration, and invasion. Findings have shown that expression of galectins is abnormal in many inflammatory autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, sjögren's syndrome, systemic sclerosis. Galectins also function as intracellular and extracellular disease regulators mainly through the binding of their carbohydrate recognition domain to glycoconjugates. Here, we review the state-of-the-art of the role that different galectin family members play in immune cells, contributing to the complex inflammatory diseases. Hopefully collection of the information will provide a preliminary theoretical basis for the exploration of new targets for treatment of the disorders.

How to detect eosinophil ETosis (EETosis) and extracellular traps

Eosinophils are short-lived and comprise only a small population of circulating leukocytes; however, they play surprisingly multifunctional roles in homeostasis and various diseases including allergy and infection. Recent research has shed light on active cytolytic eosinophil cell death that releases eosinophil extracellular traps (EETs) and total cellular contents, namely eosinophil extracellular trap cell death (EETosis). The pathological contribution of EETosis was made more cogent by recent findings that a classical pathological finding of eosinophilic inflammation, that of Charcot-Leyden crystals, is closely associated with EETosis. Currently no gold standard methods to identify EETosis exist, but “an active eosinophil lysis that releases cell-free granules and net-like chromatin structure” appears to be a common feature of EETosis. In this review, we describe several approaches that visualize EETs/EETosis in clinical samples and in vitro studies using isolated human eosinophils. EETs/EETosis can be observed using simple chemical or fluorescence staining, immunostaining, and electron microscopy, although it is noteworthy that visualization of EETs is greatly changed by sample preparation including the extracellular space of EETotic cells and shear flow. Considering the multiple aspects of biological significance, further study into EETs/EETosis is warranted to give a detailed understanding of the roles played in homeostasis and disease pathogenesis.

A review on the effect of COVID-19 in type 2 asthma and its management

Background

COVID-19 is considered the most critical health pandemic of 21st century. Due to extremely high transmission rate, people are more susceptible to viral infection. COVID-19 patients having chronic type-2 asthma prevails a major risk as it may aggravate the disease and morbidities.

Objective

The present review mainly focuses on correlating the influence of COVID-19 in type-2 asthmatic patients. Besides, it delineates the treatment measures and drugs that can be used to manage mild, moderate, and severe symptoms of COVID-19 in asthmatic patients, thus preventing any exacerbation.

Methods

An in-depth research was carried out from different peer-reviewed articles till September 2020 from several renowned databases like PubMed, Frontier, MEDLINE, and related websites like WHO, CDC, MOHFW, and the information was analysed and written in a simplified manner.

Results

The progressive results were quite conflicting as severe cases of COVID-19 shows an increase in the level of several cytokines that can augment inflammation to the bronchial tracts, worsening the asthma attacks. Contradicting to this, certain findings reveal the decrease in the severity of COVID-19 due to the elevation of T-cells in type-2 asthmatic patients, as prominent reduction of T-cell is seen in most of the COVID-19 positive patients. This helps to counteract the balance of immune responses and hence ameliorate the disease progression.

Conclusion

Asthmatic patients must remain cautious during the COVID-19 pandemic by maintaining all the precautions to stay safe due to limited research data. Future strategies should include a better understanding of asthmatic exacerbation and its relation to COVID-19.

Galectins in allergic inflammatory diseases

Allergic inflammatory diseases are a global public health concern affecting millions of people. Although there are several potential hypotheses, details regarding their molecular mechanisms are still ambiguous. Recently, a group of β-galactoside-binding proteins, galectins, have been revealed as important factors in altering allergic chronic inflammatory diseases. In this review, we describe the molecular and cellular basis of how galectins modulate inflammatory reactions. We also provide an overview of clinical features related to galectins. Finally, we discuss the potential issues that might lead to misrepresentation of the exact biological functions of galectins.

Nonimmunoglobulin Crystal-Storing Histiocytosis (CSH): Case Report and Literature Review

Crystal-storing histiocytosis (CSH) is an uncommon condition in which histiocytes accumulate a crystalline matter within their cytoplasm. Generally, those crystals are composed of either monoclonal or polyclonal immunoglobulin chains, which have a strong association with an underlying lymphoproliferative or plasma cell disorder (LP-PCD). Rarely, CSH has been reported as local or generalized manifestation of a variety of benign disorders. These cases are associated with crystals composed of nonimmunoglobulin substances. We are reporting an exceptional case of a local colonic CSH with Charcot-Leyden crystals. This patient underwent a screening colonoscopy that detected some polyps. The biopsy reported tubular adenomas, with a markedly dense, transmural inflammatory infiltrates, which were predominantly composed of eosinophils and crystal-storing histiocytes containing Charcot-Leyden crystals. The patient had a negative workup for LP-PCD and autoimmune conditions, including a normal skeletal survey and bone marrow aspirate/biopsy. The only positive laboratory workup was an elevated absolute eosinophil count and a positive IgG anti-Strongyloides antibody. Giving those findings, this parasitic infection is the most likely etiology of the CSH in our patient. Although there was an initial negative evaluation for LP-PCD, close monitoring of patients with either immunoglobulin or nonimmunoglobulin CSH is recommended.

Predictive Significance of Charcot-Leyden Crystal Protein in Nasal Secretions in Recurrent Chronic Rhinosinusitis with Nasal Polyps

INTRODUCTION

The recurrence occurs frequently among patients with chronic rhinosinusitis with nasal polyps (CRSwNP), and predictors that could be conveniently detected during practice in outpatient service are needed.

OBJECTIVE

We aimed to illustrate that the concentration of Charcot-Leyden crystal (CLC) in nasal secretions can effectively and noninvasively predict polyp recurrence.

METHODS

108 patients with CRSwNP were divided into recurrence (n = 68) and recurrence-free (n = 40) groups. Preoperative CLC concentrations in nasal secretions were collected and detected by ELISA. Polyp tissues were harvested during biopsy or endoscopic sinus surgery and were evaluated for inflammatory cells by histopathological staining. Demographic information and the clinical characteristics of each patient were reviewed for associations with recurrence. Binary logistic regression analysis was performed to determine predictive factors for polyp recurrence. Receiver operating characteristic (ROC) curves and the Youden index were performed to determine their predictive values. Survival analysis was performed to compare recurrence risk of patients with different CLC concentrations.

RESULTS

Sixty-eight (62.96%) patients developed recurrence during a 12- to 33-month postoperative follow-up. CLC concentrations in nasal secretions were positively correlated with eosinophil percent in polyp tissue and peripheral blood and were significantly higher in patients of the recurrence group than in the patients of the recurrence-free group (p < 0.001). Binary logistic regression and ROC curve demonstrated that CLC protein in nasal secretions is predictive of polyp recurrence. According to the Youden index, a CLC concentration of 34.24 ng/mL can predict postoperative polyp recurrence with 92.6% sensitivity and 87.5% specificity. Patients with CLC concentrations higher than the cutoff value yielded a higher risk of recurrence (p < 0.001, HR = 11.31, 95% CI: 6.41-19.98).

CONCLUSIONS

CLC protein in nasal secretions may serve as a promising noninvasive biomarker to predict CRSwNP recurrence.

Hypereosinophilic syndrome with abundant Charcot-Leyden crystals in spleen and lymph nodes

Hypereosinophilic syndrome, which is characterized by eosinophilia in the peripheral blood, often causes various organ disorders. Charcot-Leyden crystals are recognized features of various diseases, such as parasite infection and asthma, and are known to be classic hallmarks of eosinophilic inflammation. Our recent study revealed the mechanism of Charcot-Leyden crystal formation (i.e., galectin-10 crystallization), namely the involvement of eosinophil extracellular trap cell death, a nonapoptotic cell death. Here we report an autopsy case of a 57-year-old man who had died of hypereosinophilic syndrome. We found numerous eosinophil extracellular trap cell death-associated Charcot-Leyden crystals in the spleen and lymph nodes. Observation of abdominal lymph nodes by electron microscopy revealed eosinophil extracellular traps and free extracellular granules, which are characteristic of typical eosinophil extracellular trap cell death. In this case, we observed various sizes of Charcot-Leyden crystals that were stained with anti-galectin-10 immunofluorescent staining. Further studies are required to understand the pathophysiological roles of Charcot-Leyden crystals and these may lead to the development of novel therapeutic modalities for severe eosinophilic inflammation.

The Charcot-Leyden crystal protein revisited-A lysopalmitoylphospholipase and more

The Charcot-Leyden crystal protein (CLC-P), a constituent of human and not mouse eosinophils, is one of the most abundant proteins within human eosinophils. It has a propensity to form crystalline structures, Charcot-Leyden crystals, which are hallmarks in their distinctive extracellular crystalline forms as markers of eosinophilic inflammation. The functions of CLC-P within eosinophils have been uncertain. Although the action of CLC-P as a lysophospholipase has been questioned, assays of chromatographically purified CLC-P and crystal-derived CLC-P as well as studies of transfected recombinant CLC-P have consistently documented that CLC-P endogenously expresses lysophospholipase activity, releasing free palmitate from substrate lysopalmitoylphosphatidylcholine. Rather than acting solely as a hydrolytic enzyme to release palmitate from a lysolipid substrate, some other lysophospholipases function more dominantly as acyl-protein thioesterases (APTs), enzymes that catalyze the removal of thioester-linked, long chain fatty acids, such as palmitate, from cysteine residues of proteins. As such APTs participate in palmitoylation, a post-translational modification that can affect membrane localization, vesicular transport, and secretion. CLC-P has attributes of an APT. Thus, whereas CLC-P expresses inherent lysophospholipase activity, like some other lysophospholipase enzymes, it likely also functions in regulating the dynamic palmitoylation cycle, including, given its dominant subplasmalemmal location, at the human eosinophil's plasma membrane.

Galectin-10, the protein that forms Charcot-Leyden crystals, is not stored in granules but resides in the peripheral cytoplasm of human eosinophils

A predominant protein of human eosinophils is galectin-10 (Gal-10), also known as Charcot-Leyden crystal protein (CLC-P) because of its remarkable ability to form Charcot-Leyden crystals (CLCs), which are frequently found in tissues from patients with eosinophilic disorders. CLC-P/Gal-10 is highly expressed in human eosinophils and considered a biomarker of eosinophil involvement in inflammation. However, the intracellular sites where large pools of CLC-P/Gal-10 constitutively reside are still unclear, and whether this protein is derived or not from eosinophil granules remains to be established. Here, we applied pre-embedding immunonanogold transmission electron microscopy combined with strategies for optimal antigen and cell preservation and quantitative imaging analysis to investigate, for the first time, the intracellular localization of CLC-P/Gal-10 at high resolution in resting and activated human eosinophils. We demonstrated that CLC-P/Gal-10 is mostly stored in the peripheral cytoplasm of human eosinophils, being accumulated within an area of ∼250 nm wide underneath the plasma membrane and not within specific (secretory) granules, a pattern also observed by immunofluorescence. High-resolution analysis of single cells revealed that CLC-P/Gal-10 interacts with the plasma membrane with immunoreactive microdomains of high CLC-P/Gal-10 density being found in ∼60% of the membrane area. Eosinophil stimulation with CCL11 or TNF-α, which are known inducers of eosinophil secretion, did not change the peripheral localization of CLC-P/Gal-10 as observed by both immunofluorescence and immuno-EM (electron microscopy). Thus, in contrast to other preformed eosinophil proteins, CLC-P/Gal-10 neither is stored within secretory granules nor exported through classical degranulation mechanisms (piecemeal degranulation and compound exocytosis).