Biology of the eosinophil

Eosinophil extracellular vesicles and DNA traps in allergic inflammation

Eosinophil granulocytes, a specialized subset of white blood cells, have traditionally been associated with allergic responses and parasitic infections. However, recent research has unveiled their versatile roles in immune regulation beyond these classical functions. This review highlights the emerging field of eosinophil biology, with a particular focus on their release of extracellular vesicles (EVs) and extracellular DNA traps (EETs). It further explores potential implications of eosinophil-derived EVs and EETs for immune responses during inflammatory diseases. The release of EVs/EETs from eosinophils, which also affects the eosinophils themselves, may influence both local and systemic immune reactions, affecting the pathophysiology of conditions such as airway inflammation, chronic rhinosinusitis and atopic dermatitis.

SingleNucleotide Polymorphisms as Biomarkers of Mepolizumab and Benralizumab Treatment Response in Severe Eosinophilic Asthma

The most promising treatment options for severe uncontrolled asthma (SUA) have emerged in recent years with the development of monoclonal antibodies for blocking selective targets responsible for the underlying inflammation, such as mepolizumab and benralizumab. However, there is variability in treatment response that is not fully controlled. The variability of the response to mepolizumab and benralizumab could be influenced by single-nucleotide polymorphisms (SNPs), and it would be useful to detect these and use them as predictive biomarkers of response. We conducted a retrospective observational cohort study of 72 Caucasian patients recruited from a tertiary hospital with severe uncontrolled eosinophilic asthma treated with mepolizumab and benralizumab. Polymorphisms in the IL5 (rs4143832, rs17690122), RAD50 (rs11739623, rs4705959), IL1RL1 (rs1420101, rs17026974, rs1921622), GATA2 (rs4857855), IKZF2 (rs12619285), FCGR2A (rs1801274), FCGR2B (rs3219018, rs1050501), FCGR3A (rs10127939, rs396991), FCER1A (rs2251746, rs2427837), FCER1B (rs1441586, rs573790, rs569108), and ZNF415 (rs1054485) genes were analyzed by real-time polymerase chain reaction (PCR) using Taqman probes. The response was analyzed after 12 months of treatment. In patients under mepolizumab treatment, a treatment response defined as a reduction in exacerbations was associated with ZNF415 rs1054485-T (p = 0.042; OR = 5.33; 95% CI = 1.06-30.02), treatment response defined as a reduction in oral corticosteroids use was associated with the number of exacerbations in the previous year (p = 0.029; OR = 3.89; 95% CI = 1.24-14.92), and treatment response defined as improvement in lung function was associated with the age at the beginning of biological therapy (p = 0.002; OR = 1.10; 95% CI = 1.04-1.18), FCER1B rs569108-AA (p < 0.001; OR = 171.06; 95% CI = 12.94-6264.11), and FCER1A rs2427837-A (p = 0.021; OR = 8.61; 95% CI = 1.71-76.62). On the other hand, in patients under benralizumab treatment, treatment response, defined as a reduction in exacerbations, was associated with ZNF415 rs1054485-T (p = 0.073; OR = 1.3 × 108; 95% CI = 1.8 × 10-19-NA), FCER1B rs569108-AA (p = 0.050; OR = 11.51; 95% CI = 1.19-269.78), allergies (p = 0.045; OR = 4.02; 95% CI = 1.05-16.74), and sex (p = 0.028; OR = 4.78; 95% CI = 1.22-20.63); and treatment response defined as improvement in lung function was associated with polyposis (p = 0.027; OR = 9.16; 95% CI = 1.58-91.4), IKZF2 rs12619285-AA (p = 0.019; OR = 9.1; 95% CI = 1.7-75.78), IL5 rs4143832-T (p = 0.017; OR = 11.1; 95% CI = 1.9-112.17), and FCER1B rs1441586-C (p = 0.045; OR = 7.81; 95% CI = 1.16-73.45). The results of this study show the potential influence of the studied polymorphisms on the response to mepolizumab and benralizumab and the clinical benefit that could be obtained by defining predictive biomarkers of treatment response.

Ally, adversary, or arbitrator? The context-dependent role of eosinophils in vaccination for respiratory viruses and subsequent breakthrough infections

Eosinophils are a critical type of immune cell and central players in type 2 immunity. Existing literature suggests that eosinophils also can play a role in host antiviral responses, typically type 1 immune events, against multiple respiratory viruses, both directly through release of antiviral mediators and indirectly through activation of other effector cell types. One way to prime host immune responses toward effective antiviral responses is through vaccination, where typically a type 1-skewed immunity is desirable in the context of intracellular pathogens like respiratory viruses. In the realm of breakthrough respiratory viral infection in vaccinated hosts, an event in which virus can still establish productive infection despite preexisting immunity, eosinophils are most prominently known for their link to vaccine-associated enhanced respiratory disease upon natural respiratory syncytial virus infection. This was observed in a pediatric cohort during the 1960s following vaccination with formalin-inactivated respiratory syncytial virus. More recent research has unveiled additional roles of the eosinophil in respiratory viral infection and breakthrough infection. The specific contribution of eosinophils to the quality of vaccine responses, vaccine efficacy, and antiviral responses to infection in vaccinated hosts remains largely unexplored, especially regarding their potential roles in protection. On the basis of current findings, we will speculate upon the suggested function of eosinophils and consider the many potential ways by which eosinophils may exert protective and pathological effects in breakthrough infections. We will also discuss how to balance vaccine efficacy with eosinophil-related risks, as well as the use of eosinophils and their products as potential biomarkers of vaccine efficacy or adverse events.

Eosinophilic Patterns in Patients with Seasonal Allergy Affected by Bronchial Asthma and Rhinitis/Rhinosinusitis: Efficacy of Benralizumab in Patients with the Persistent Pattern

BACKGROUND

Eosinophilia can be influenced by multiple factors. This study aims to set a protocol for monitoring blood absolute eosinophil count (AEC) in patients with seasonal allergy affected by bronchial asthma (BA), allergic rhinitis (AR), or chronic rhinosinusitis with or without nasal polyposis (CRSw/sNP).

METHODS

We planned a total of four annual blood samples to measure AEC in- and out-seasonal pollen exposure (i.e., one measurement every three months for one year).

RESULTS

We identified two distinct groups of patients (non-eosinophilic and eosinophilic). Patients in the eosinophilic group presented with four different patterns (episodic, transient, floating, and persistent). Most patients with episodic, transient, and floating patterns were affected by mild allergy and the increase in eosinophils was related to allergen exposure. In contrast, patients with the persistent pattern mostly presented with more severe allergy (i.e., severe BA and relapsing CRSwNP) and the eosinophilia was unrelated to allergen exposure. The subgroup of patients with severe BA, relapsing CRSwNP, and persistent eosinophilc pattern were treated with benralizumab, which induced a noteworthy improvement in both severe BA and CRSwNP.

CONCLUSIONS

Multiple AEC measurements in patients with seasonal allergy can better reflect patient's eosinophilic status and help define the relationship of AEC enhancement with allergen exposure.

Hypereosinophilia as a presenting sign of advanced pancreatic adenocarcinoma: a rare, severe presentation

Pancreatic adenocarcinoma (PA) is the third most lethal malignancy worldwide with only a 7.7% 5-year survival rate. Prognosis is poor with more than 50% of patients presenting with stage IV disease. Despite focused attention on early detection and treatment, pathogenesis and early symptomatology are not well described. In addition to prodromal symptoms, hypereosinophilia has been identified as a marker of malignancy in both PA and other solid tumour and haematological malignancies. Peripheral hypereosinophilia (PH) secondary to solid organ tumours, however, is rare, with only four cases of PA reported to date. We present a case of advanced PA with associated severe PH in a man in his early 50s. Time from diagnosis to death in this patient was only 6 weeks, emphasising the need to consider malignancy in the differential diagnosis for a patient that presents with a severe PH of unknown origin.

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.

Chronic Atopic Dermatitis with Eosinophilia Improved by Daesiho-Tang: A Case Report

Purpose

This study is to report a case of chronic atopic dermatitis (AD) with eosinophilia, which did not respond to conventional therapy and was improved by Daesiho-tang (DSHT).

Patients and Methods

The patient visited our clinic with symptoms of atopic dermatitis including skin lesions and pruritus. Based on her symptoms, DSHT was prescribed. At each visit, the Scoring Atopic Dermatitis (SCORAD), Dermatology Life Quality Index (DLQI), and accompanying systemic symptoms (ASS) were measured. Multiple Allergen Simultaneous Test (MAST) was initially performed for 108 allergens and analyzed by Western blotting using an Alternate Scoring Method (ASM) according to the specific IgE concentration. Also, peripheral blood laboratory (Lab) tests were performed three times during the patient's visit.

Results

After taking DSHT, the total SCORAD score improved from 62.9 to 23.5, while the patient's ASS also improved. The DLQI score improved from 19 to 5. The total number of eosinophils in the peripheral blood, which showed a mild increase, recovered from 17.2% (0.98 x103/μL) to 4.5% (0.24 x103/μL). The total IgE slightly decreased, while AST and ALT were also restored to normal ranges.

Conclusion

Based on this case, DSHT is considered a potential alternative treatment for AD.

Eosinophilic Granulomatosis with Polyangiitis: Latest Findings and Updated Treatment Recommendations

Eosinophilic granulomatosis with polyangiitis (EGPA) causes necrotizing vasculitis and eosinophil-rich granulomatous inflammation in small- to medium-sized vessels, resulting in multiple organ damage. EGPA is classified as an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, with myeloperoxidase-ANCA detected in approximately one-third of the patients. Conventional treatment of EGPA relies on systemic glucocorticoids (GCs) in combination with cyclophosphamide when poor prognostic factors are present; however, the dilemma between disease control and drug-related adverse effects has long been a challenge. Recent studies have revealed that the genetic background, pathophysiology, and clinical manifestations differ between ANCA-positive and ANCA-negative patients; however, mepolizumab, an interleukin (IL)-5 inhibitor, is effective in both groups, suggesting that the IL-5-eosinophil axis is deeply involved in the pathogenesis of both ANCA-positive and ANCA-negative EGPA. This review summarizes the latest knowledge on the pathophysiology of EGPA and focuses on the roles of eosinophils and ANCA. We then introduce the current treatment recommendations and accumulated evidence for mepolizumab on EGPA. Based on current unmet clinical needs, we discuss potential future therapeutic strategies for EGPA.

Nonatopic Eosinophilic Duodenitis in an Adult: A Case Report and Overview

Eosinophilic duodenitis is an inflammation of the duodenum, characterized by an abundance of eosinophils, typically triggered by hypersensitivity reactions. Typically, recurrent abdominal pain with eosinophilic duodenitis is rare in individuals without a history of atopic conditions like asthma. Here, we present the case of a 62-year-old man who experienced recurrent upper abdominal pain for 12 months and unintended weight loss for the past six months. The patient reported no allergies to food, drugs, or the environment, and has no history of other atopic conditions. Esophagogastroduodenoscopy (EGD) with biopsy of the duodenum and stomach revealed 32 eosinophils per high-power field (HPF), which is mild. Skin prick testing yielded negative results. Following initial treatment with H2 inhibitors, proton pump inhibitors, and budesonide for a total of 12 weeks, the patient reported an improvement in symptoms and subsequent weight gain. This report emphasizes a rare case of eosinophilic duodenitis in a nonatopic individual with a successful treatment regimen. His quality of life improved with weight gain, resolved abdominal pain, and improved appetite. Although the patient's condition lasted about 12 months, our report showcased the importance of timely clinical diagnosis and appropriate combination therapy to alleviate progressive pain associated with eosinophilic duodenitis.

Features of the response to subchronic low-dose exposure to copper oxide nanoparticles in rats

Copper is an essential trace element for human health and, at the same time, a major industrial metal widely used both in its elemental form and in compounds. We conducted a dose-dependent assessment of the response of outbred albino male rats to subchronic low-dose exposure to copper oxide nanoparticles administered intraperitoneally at cumulative doses of 18 and 36 mg/kg during 6 weeks to exposure groups 1 and 2, respectively. We observed disorders at different levels of organization of the body in the exposed animals, from molecular to organismal. The observed decrease in the activity of succinate dehydrogenase in nucleated blood cells gave evidence of impaired bioenergetics processes. In view of the results of the metabolomics analysis, we assume mitochondrial damage and contribution of apoptotic processes to the pathology induced by copper poisoning. We also assume neurodegenerative effects based on the assessed morphological parameters of the nervous system, results of behavioral tests, and a decreased level of expression of genes encoding NMDA receptor subunits in the hippocampus. The hepatotoxic effect noted by a number of metabolomics-based, biochemical, and cytological indicators was manifested by the impaired protein-synthesizing function of the liver and enhanced degenerative processes in its cells. We also observed a nephrotoxic effect of nanosized copper oxide with a predominant lesion of proximal kidney tubules. At the same time, both doses tested demonstrated such positive health effects as a statistically significant decrease in the activity of alkaline phosphatase and the nucleated blood cell DNA fragmentation factor. Judging by the changes observed, the cumulative dose of copper oxide nanoparticles of 18 mg/kg body weight administered intraperitoneally approximates the threshold one for rats. The established markers of health impairments may serve as a starting point in the development of techniques of early diagnosis of copper poisoning.

The multidisciplinary approach to eosinophilia

Eosinophilic granulocytes are normally present in low numbers in the bloodstream. Patients with an increased number of eosinophilic granulocytes in the differential count (eosinophilia) are common and can pose a clinical challenge because conditions with eosinophilia occur in all medical specialties. The diagnostic approach must be guided by a thorough medical history, supported by specific tests to guide individualized treatment. Neoplastic (primary) eosinophilia is identified by one of several unique acquired genetic causes. In contrast, reactive (secondary) eosinophilia is associated with a cytokine stimulus in a specific disease, while idiopathic eosinophilia is a diagnosis by exclusion. Rational treatment is disease-directed in secondary cases and has paved the way for targeted treatment against the driver in primary eosinophilia, whereas idiopathic cases are treated as needed by principles in eosinophilia originating from clonal drivers. The vast majority of patients are diagnosed with secondary eosinophilia and are managed by the relevant specialty-e.g., rheumatology, allergy, dermatology, gastroenterology, pulmonary medicine, hematology, or infectious disease. The overlap in symptoms and the risk of irreversible organ involvement in eosinophilia, irrespective of the cause, warrants that patients without a diagnostic clarification or who do not respond to adequate treatment should be referred to a multidisciplinary function anchored in a hematology department for evaluation. This review presents the pathophysiology, manifestations, differential diagnosis, diagnostic workup, and management of (adult) patients with eosinophilia. The purpose is to place eosinophilia in a clinical context, and therefore justify and inspire the establishment of a multidisciplinary team of experts from diagnostic and clinical specialties at the regional level to support the second opinion. The target patient population requires highly specialized laboratory analysis and therapy and occasionally has severe eosinophil-induced organ dysfunction. An added value of a centralized, clinical function is to serve as a platform for education and research to further improve the management of patients with eosinophilia. Primary and idiopathic eosinophilia are key topics in the review, which also address current research and discusses outstanding issues in the field.

Eosinophilic Lung Diseases

The eosinophilic lung diseases may manifest as chronic eosinophilic pneumonia, acute eosinophilic pneumonia, or as the Löffler syndrome (generally of parasitic etiology). The diagnosis of eosinophilic pneumonia is made when both characteristic clinical-imaging features and alveolar eosinophilia are present. Peripheral blood eosinophils are generally markedly elevated; however, eosinophilia may be absent at presentation. Lung biopsy is not indicated except in atypical cases after multidisciplinary discussion. The inquiry to possible causes (medications, toxic drugs, exposures, and infections especially parasitic) must be meticulous. Idiopathic acute eosinophilic pneumonia may be misdiagnosed as infectious pneumonia. Extrathoracic manifestations raise the suspicion of a systemic disease especially eosinophilic granulomatosis with polyangiitis. Airflow obstruction is frequent in allergic bronchopulmonary aspergillosis, idiopathic chronic eosinophilic pneumonia, eosinophilic granulomatosis with polyangiitis, and hypereosinophilic obliterative bronchiolitis. Corticosteroids are the cornerstone of therapy, but relapses are common. Therapies targeting interleukin 5/interleukin-5 are increasingly used in eosinophilic lung diseases.

Intratumor childhood vaccine-specific CD4+ T-cell recall coordinates antitumor CD8+ T cells and eosinophils

BACKGROUND

Antitumor mechanisms of CD4⁺ T cells remain crudely defined, and means to effectively harness CD4⁺ T-cell help for cancer immunotherapy are lacking. Pre-existing memory CD4⁺ T cells hold potential to be leveraged for this purpose. Moreover, the role of pre-existing immunity in virotherapy, particularly recombinant poliovirus immunotherapy where childhood polio vaccine specific immunity is ubiquitous, remains unclear. Here we tested the hypothesis that childhood vaccine-specific memory T cells mediate antitumor immunotherapy and contribute to the antitumor efficacy of polio virotherapy.

METHODS

The impact of polio immunization on polio virotherapy, and the antitumor effects of polio and tetanus recall were tested in syngeneic murine melanoma and breast cancer models. CD8⁺ T-cell and B-cell knockout, CD4⁺ T-cell depletion, CD4⁺ T-cell adoptive transfer, CD40L blockade, assessments of antitumor T-cell immunity, and eosinophil depletion defined antitumor mechanisms of recall antigens. Pan-cancer transcriptome data sets and polio virotherapy clinical trial correlates were used to assess the relevance of these findings in humans.

RESULTS

Prior vaccination against poliovirus substantially bolstered the antitumor efficacy of polio virotherapy in mice, and intratumor recall of poliovirus or tetanus immunity delayed tumor growth. Intratumor recall antigens augmented antitumor T-cell function, caused marked tumor infiltration of type 2 innate lymphoid cells and eosinophils, and decreased proportions of regulatory T cells (Tregs). Antitumor effects of recall antigens were mediated by CD4⁺ T cells, limited by B cells, independent of CD40L, and dependent on eosinophils and CD8⁺ T cells. An inverse relationship between eosinophil and Treg signatures was observed across The Cancer Genome Atlas (TCGA) cancer types, and eosinophil depletion prevented Treg reductions after polio recall. Pretreatment polio neutralizing antibody titers were higher in patients living longer, and eosinophil levels increased in the majority of patients, after polio virotherapy.

CONCLUSION

Pre-existing anti-polio immunity contributes to the antitumor efficacy of polio virotherapy. This work defines cancer immunotherapy potential of childhood vaccines, reveals their utility to engage CD4⁺ T-cell help for antitumor CD8⁺ T cells, and implicates eosinophils as antitumor effectors of CD4⁺ T cells.

Case report: Successful use of mepolizumab for immune checkpoint inhibitors-induced hypereosinophilic syndrome in two patients with solid malignancies

Hypereosinophilic syndrome (HES) represents a group of blood disorders characterized by an absolute eosinophil count (AEC) > 1.5 × 103/μl in the peripheral blood, which eventually extravasate and cause organ damage. It can be primary or secondary to infections or tumors. The infiltration of eosinophils in tissue and organs is associated with different disorders and, in some cases, with life-threatening manifestations. Albeit the pathogenesis of HES in patients with solid tumo\rs is not yet clarified; recently, HES has also been described as an immune-related adverse event in patients with solid tumors receiving immune checkpoint inhibitors. Treatment of HES is still debated, especially in patients with concomitant solid tumors, and different drugs including imatinib, hydroxyurea, interferon-ɑ, glucocorticoids, and the monoclonal antibody targeting circulating IL-5 mepolizumab have been proposed according to the underlying cause and the severity of HES. Herein, we describe, for the first time, the successful use of mepolizumab for the treatment of immune checkpoint-induced HES in two patients with metastatic solid tumor.

CCL4 Regulates Eosinophil Activation in Eosinophilic Airway Inflammation

Eosinophilic chronic rhinosinusitis (ECRS) is a refractory airway disease accompanied by eosinophilic inflammation, the mechanisms of which are unknown. We recently found that CCL4/MIP-1β-a specific ligand for CCR5 receptors-was implicated in eosinophil recruitment into the inflammatory site and was substantially released from activated eosinophils. Moreover, it was found in nasal polyps from patients with ECRS, primarily in epithelial cells. In the present study, the role of epithelial cell-derived CCL4 in eosinophil activation was investigated. First, CCL4 expression in nasal polyps from patients with ECRS as well as its role of CCL4 in eosinophilic airway inflammation were investigated in an in vivo model. Furthermore, the role of CCL4 in CD69 expression-a marker of activated eosinophils-as well as the signaling pathways involved in CCL4-mediated eosinophil activation were investigated. Notably, CCL4 expression, but not CCL5, CCL11, or CCL26, was found to be significantly increased in nasal polyps from patients with ECRS associated with eosinophil infiltration as well as in BEAS-2B cells co-incubated with eosinophils. In an OVA-induced allergic mouse model, CCL4 increased eosinophil accumulation in the nasal mucosa and the bronchoalveolar lavage (BALF). Moreover, we found that CD69 expression was upregulated in CCL4-stimulated eosinophils; similarly, phosphorylation of several kinases, including platelet-derived growth factor receptor (PDGFR)β, SRC kinase family (Lck, Src, and Yes), and extracellular signal-regulated kinase (ERK), was upregulated. Further, CCR5, PDGFRβ, and/or Src kinase inhibition partially restored CCL4-induced CD69 upregulation. Thus, CCL4, which is derived from airway epithelial cells, plays a role in the accumulation and activation of eosinophils at inflammatory sites. These findings may provide a novel therapeutic target for eosinophilic airway inflammation, such as ECRS.

Challenges in managing a multifactorial eosinophilic pneumonia: daptomycin vs strongyloidiasis case report

BACKGROUND

Eosinophilia is defined as a blood eosinophil count > 500/mcL with etiology usually an allergic reaction or parasitic infection which can lead to serious organ damage.

CASE PRESENTATION

A patient being treated for hardware infection develops eosinophilia while on daptomycin in the setting of a positive strongyloides antibody. The patient was on chronic steroids prior to admission for epitheliopathy which complicated care. The daptomycin was discontinued, ivermectin initiated to treat strongyloidiasis, and high dose steroids initiated simultaneously. Eosinophilia resolved and patient discharged home after two months in the hospital.

CONCLUSION

Multifactorial eosinophilia poses question of steroid harm in the setting of parasitic infection. Patient was treated for both strongyloides and daptomycin induced eosinophilia with improvement and discharge from the hospital.

Eosinophils in filarial infections: Inducers of protection or pathology?

Filariae are parasitic roundworms, which can cause debilitating diseases such as lymphatic filariasis and onchocerciasis. Lymphatic filariasis, also known as elephantiasis, and onchocerciasis, commonly referred to as river blindness, can lead to stigmatizing pathologies and present a socio-economic burden for affected people and their endemic countries. Filariae typically induce a type 2 immune response, which is characterized by cytokines, i.e., IL-4, IL-5 and IL-13 as well as type 2 immune cells including alternatively activated macrophages, innate lymphoid cells and Th2 cells. However, the hallmark characteristic of filarial infections is a profound eosinophilia. Eosinophils are innate immune cells and pivotal in controlling helminth infections in general and filarial infections in particular. By modulating the function of other leukocytes, eosinophils support and drive type 2 immune responses. Moreover, as primary effector cells, eosinophils can directly attack filariae through the release of granules containing toxic cationic proteins with or without extracellular DNA traps. At the same time, eosinophils can be a driving force for filarial pathology as observed during tropical pulmonary eosinophilia in lymphatic filariasis, in dermatitis in onchocerciasis patients as well as adverse events after treatment of onchocerciasis patients with diethylcarbamazine. This review summarizes the latest findings of the importance of eosinophil effector functions including the role of eosinophil-derived proteins in controlling filarial infections and their impact on filarial pathology analyzing both human and experimental animal studies.

Suppression of airway allergic eosinophilia by Hp-TGM, a helminth mimic of TGF-β

Type 2-high asthma is a chronic inflammatory disease of the airways which is increasingly prevalent in countries where helminth parasite infections are rare, and characterized by T helper 2 (Th2)-dependent accumulation of eosinophils in the lungs. Regulatory cytokines such as TGF-β can restrain inflammatory reactions, dampen allergic Th2 responses, and control eosinophil activation. The murine helminth parasite Heligmosomoides polygyrus releases a TGF-β mimic (Hp-TGM) that replicates the biological and functional properties of TGF-β despite bearing no structural similarity to the mammalian protein. Here, we investigated if Hp-TGM could alleviate allergic airway inflammation in mice exposed to Alternaria alternata allergen, house dust mite (HDM) extract or alum-adjuvanted ovalbumin protein (OVA). Intranasal administration of Hp-TGM during Alternaria exposure sharply reduced airway and lung tissue eosinophilia along with bronchoalveolar lavage fluid IL-5 and lung IL-33 cytokine levels at 24 h. The protective effect of Hp-TGM on airway eosinophilia was also obtained in the longer T-cell mediated models of HDM or OVA sensitisation with significant inhibition of eotaxin-1, IL-4 and IL-13 responses depending on the model and time-point. Hp-TGM was also protective when administered parenterally either when given at the time of allergic sensitisation or during airway allergen challenge. This project has taken the first steps in identifying the role of Hp-TGM in allergic asthma and highlighted its ability to control lung inflammation and allergic pathology. Future research will investigate the mode of action of Hp-TGM against airway allergic eosinophilia, and further explore its potential to be developed as a biotherapeutic in allergic asthma.

Chemokines and chemokine receptors in allergic rhinitis: from mediators to potential therapeutic targets

Allergic rhinitis (AR) is an immune-mediated inflammatory condition characterized by immune cell infiltration of the nasal mucosa, with symptoms of rhinorrhea, sneezing, nasal obstruction, and itchiness. Currently, common medication for AR is anti-inflammatory treatment including intranasal steroids, oral, or intranasal anti-histamines, and immunotherapy. These strategies are effective to the majority of patients with AR, but some patients under medication cannot achieve symptom relieve and suffer from bothersome side effects, indicating a demand for novel anti-inflammatory treatment as alternatives. Chemokines, a complex superfamily of small, secreted proteins, were initially recognized for their chemotactic effects on various immune cells. Chemokines constitute both physiological and inflammatory cell positioning systems and mediate cell localization to certain sites via interaction with their receptors, which are expressed on responding cells. Chemokines and their receptors participate in the sensitization, early phase response, and late phase response of AR by promoting inflammatory cell recruitment, differentiation, and allergic mediator release. In this review, we first systemically summarize chemokines and chemokine receptors that are important in AR pathophysiology and then discuss potential strategies targeting chemokines and their receptors for AR therapy.

Eosinophils in the Gastrointestinal Tract: Key Contributors to Neuro-Immune Crosstalk and Potential Implications in Disorders of Brain-Gut Interaction

Eosinophils are innate immune granulocytes actively involved in defensive responses and in local and systemic inflammatory processes. Beyond these effector roles, eosinophils are fundamental to maintaining homeostasis in the tissues they reside. Gastrointestinal eosinophils modulate barrier function and mucosal immunity and promote tissue development through their direct communication with almost every cellular component. This is possible thanks to the variety of receptors they express and the bioactive molecules they store and release, including cytotoxic proteins, cytokines, growth factors, and neuropeptides and neurotrophines. A growing body of evidence points to the eosinophil as a key neuro-immune player in the regulation of gastrointestinal function, with potential implications in pathophysiological processes. Eosinophil–neuron interactions are facilitated by chemotaxis and adhesion molecules, and the mediators released may have excitatory or inhibitory effects on each cell type, with physiological consequences dependent on the type of innervation involved. Of special interest are the disorders of the brain–gut interaction (DBGIs), mainly functional dyspepsia (FD) and irritable bowel syndrome (IBS), in which mucosal eosinophilia and eosinophil activation have been identified. In this review, we summarize the main roles of gastrointestinal eosinophils in supporting gut homeostasis and the evidence available on eosinophil–neuron interactions to bring new insights that support the fundamental role of this neuro-immune crosstalk in maintaining gut health and contributing to the pathophysiology of DBGIs.

Food Allergen Nitration Enhances Safety and Efficacy of Oral Immunotherapy in Food Allergy

(1) Background: Posttranslational protein modifications have been demonstrated to change protein allergenicity. Previously, it was reported that pretreatment with highly nitrated food proteins induced a tolerogenic immune response in an experimental mouse model and in human immune cells. Here, we investigated a possible therapeutic effect of modified proteins and evaluated the safety of oral exposure to highly nitrated proteins in an experimental food allergy model. (2) Methods: BALB/c mice were orally sensitized towards ovalbumin (OVA) under gastric acid suppression. Thereafter, treatment via intragastric gavage with maximally nitrated OVA (nOVAmax) and OVA as a control was performed six times every 2 weeks. On the last day of experiments, all the treated mice were orally challenged with OVA. Systemic anaphylactic reaction was determined by measuring the core body temperature. Moreover, antibody levels, regulatory T cell numbers, cytokine levels and histology of antrum tissues were analyzed. (3) Results: After oral immunotherapy, OVA-specific IgE titers were decreased while IgG1 titers were significantly elevated in the mice receiving OVA. After oral challenge with OVA, nOVAmax-treated allergic animals showed no drop of the core body temperature, which was observed for OVA-allergic and OVA-treated allergic animals. Significantly fewer eosinophils and mast cells were found in the gastric mucosa of the allergic mice after nOVAmax treatment. (4) Conclusions: Oral immunotherapy with nOVAmax reduced allergic reactions upon allergen exposure and the number of allergen effector cells in the gastric mucosa. Thus, maximally nitrated allergens enabled an efficient and safe treatment for food allergy in our experimental model.

From DREAM to REALITI-A and beyond: Mepolizumab for the treatment of eosinophil-driven diseases

Effective treatment of inflammatory diseases is often challenging owing to their heterogeneous pathophysiology. Understanding of the underlying disease mechanisms is improving and it is now clear that eosinophils play a complex pathophysiological role in a broad range of type 2 inflammatory diseases. Standard of care for these conditions often still includes oral corticosteroids (OCS) and/or cytotoxic immune therapies, which are associated with debilitating side effects. Selective, biological eosinophil‐reducing agents provide treatment options that improve clinical symptoms associated with eosinophilic inflammation and reduce OCS use. Mepolizumab is a humanized monoclonal antibody that binds to and neutralizes interleukin‐5, the major cytokine involved in eosinophil proliferation, activation, and survival. Mepolizumab is approved for the treatment of severe eosinophilic asthma, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome. Additionally, the efficacy of add‐on mepolizumab has been observed in patients with severe chronic rhinosinusitis with nasal polyposis and chronic obstructive pulmonary disease with an eosinophilic phenotype. Here, we review the development, approval, and real‐world effectiveness of mepolizumab for the treatment of patients with severe eosinophilic asthma, from the DREAM to REALITI‐A studies, and describe how knowledge from this journey extended to the use of mepolizumab and other biologics across a broad spectrum of eosinophilic diseases.

Eosinophils and melanoma: Implications for immunotherapy

New therapies such as immune checkpoint blockers (ICB) have offered extended survival to patients affected by advanced melanoma. However, ICBs have demonstrated debilitating side effects on the joints, liver, lungs, skin, and gut. Several biomarkers have been identified for their role in predicting which patients better tolerate ICBs. Still, these biomarkers are limited by immunologic and genetic heterogeneity and the complexity of translation into clinical practice. Recent observational studies have suggested eosinophil counts, and serum levels of eosinophil cationic protein are significantly associated with prolonged survival in advanced-stage melanoma. It is likely that eosinophils thereby modulate treatment response through mechanisms yet to be explored. Here, we review the functionality of eosinophils, their oncogenic role in melanoma and discuss how these mechanisms may influence patient response to ICBs and their implications in clinical practice.

Isolation and characterization of eosinophils in bovine blood and small intestine

An effective method to isolate functional eosinophils from blood and tissues is required to analyze the multiple roles eosinophils play in innate immunity and tissue homeostasis. Highspeed cell sorting was used to isolate bovine eosinophils from blood polymorphonuclear (PMN) cells and from small intestine intraepithelial leukocytes. Eosinophils and neutrophils were purified from bovine blood with highspeed cell sorting after gating on autofluorescence (FL1) high and low PMN subpopulations. Highspeed sorting of intestinal eosinophils was accomplished by using a combination of positive (CD45⁺, CD11c^Low, side scatter^High) and negative (CD3^-) selection parameters. Eosinophils sorted from blood PMNs were 88.6 ± 5.8 % (mean + 1 SD; n = 4) pure and yielded significantly (p < 0.05) more RNA than purified neutrophils. Analysis of Toll-like receptor (TLR) gene expression and TLR ligand-induced pro-inflammatory cytokine (IL-1, IL-6, IL-8, and TNFα) gene expression demonstrated significant (p < 0.01) functional differences between blood eosinophils and neutrophils. Eosinophils varied between 14.7 % to 29.3 % of CD45⁺ IELs and purity of sorted intestinal eosinophils was 95 + 3.5 % (mean + 1SD; n = 5). A comparison of mucosal and blood eosinophils revealed significant (p < 0.01) differences in TLR gene expression, supporting the hypothesis that functionally distinct eosinophil populations are present in blood and tissues. In conclusion, highspeed cell sorting provides an effective method to isolate viable eosinophils from blood and tissues that can then be used for transcriptome analyses and in vitro function assays.

Effective Management of Severe Asthma with Biologic Medications in Adult Patients: A Literature Review and International Expert Opinion

Severe asthma often remains uncontrolled despite effective treatments and evidence-based guidelines. A group of global experts in asthma and biologic medications from 9 countries considered the most relevant clinical variables to manage severe asthma in adult patients and guide treatment choice. The resulting recommendations address the investigation of biomarker levels (blood eosinophil count along with fractional concentration of exhaled nitric oxide [FeNO]), clinical features (oral corticosteroid [OCS] dependence, specific comorbid disease entities associated with severe type 2 asthma), and safety considerations. Current evidence suggests that biomarkers, including both blood or sputum eosinophil counts as well as FeNO, add prognostic and predictive value and should be measured in all patients with severe asthma. OCS use is an important factor in biologic selection, especially given the documented ability of some biologics to reduce OCS dependence. Comorbid diseases and relevant safety considerations to each biologic should also be considered. More data are needed to determine whether biomarker profiles identify patients suited to one biologic versus another as limited data support differential predictors of response. Further prospective head-to-head trials and post hoc analyses of clinical trial data are warranted. The authors believe that these recommendations have value as they offer expert opinion to assist health care providers in making difficult decisions regarding the quality of care in severe, type 2 asthma with biologic medications. They remain conditional and are based on limited data owing to a lack of head-to-head comparisons.

α4β1 and αMβ2 Integrin Expression and Pro-Proliferative Properties of Eosinophil Subtypes in Asthma

Eosinophilic inflammation is one of the main pathophysiological features in asthma. Two subtypes of eosinophils exist in the lung and systemic circulation: lung-resident eosinophils (rEOS) and inflammatory eosinophils (iEOS). We evaluated the expression of α₄β₁ and α_Mβ₂ integrins of eosinophil subtypes and their influence on airway smooth muscle (ASM) cell proliferation and viability in asthma. We included 16 severe non-allergic eosinophilic asthma (SNEA) patients, 13 steroid-free, non-severe allergic asthma (AA) patients, and 12 healthy control subjects (HS). For AA patients, a bronchial allergen challenge with Dermatophagoides pteronyssinus was performed. The eosinophil subtypes were distinguished using magnetic bead-labeled antibodies against surface CD62L, and individual combined cell cultures were prepared with ASM cells. The integrins gene expression was analyzed by a quantitative real-time polymerase chain reaction. Proliferation was assessed by the Alamar blue assay, and viability by annexin V and propidium iodide staining. rEOS-like cells were characterized by the relatively higher gene expression of the β₁ integrin subunit, whereas iEOS-like cells were characterized by the α_M and β₂ integrin subunits. The inclusion of either eosinophil subtypes in co-culture significantly increased the proliferation of ASM cells, and the effect of rEOS-like cells was stronger than iEOS-like cells (p < 0.05). Furthermore, rEOS-like cells had a more pronounced effect on reducing ASM cell apoptosis compared to that of iEOS-like cells (p < 0.05). Lastly, the bronchial allergen challenge significantly enhanced only the iEOS-like cells’ effect on ASM cell proliferation and viability in AA patients (p < 0.05). These findings highlight the different expression of α₄β₁ and α_Mβ₂ integrins on distinct eosinophil subtypes in asthma. Therefore, rEOS-like cells have a stronger effect in stimulating ASM cell proliferation and viability; however, contact with specific allergens mainly enhances pro-proliferative iEOS-like cell properties.

Recent trends of NFκB decoy oligodeoxynucleotide-based nanotherapeutics in lung diseases

Nuclear factor κB (NFκB) is a unique protein complex that plays a major role in lung inflammation and respiratory dysfunction. The NFκB signaling pathway, therefore becomes an avenue for the development of potential pharmacological interventions, especially in situations where chronic inflammation is often constitutively active and plays a key role in the pathogenesis and progression of the disease. NFκB decoy oligodeoxynucleotides (ODNs) are double-stranded and carry NFκB binding sequences. They prevent the formation of NFκB-mediated inflammatory cytokines and thus have been employed in the treatment of a variety of chronic inflammatory diseases. However, the systemic administration of naked decoy ODNs restricts their therapeutic effectiveness because of their poor pharmacokinetic profile, instability, degradation by cellular enzymes and their low cellular uptake. Both structural modification and nanotechnology have shown promising results in enhancing the pharmacokinetic profiles of potent therapeutic substances and have also shown great potential in the treatment of respiratory diseases such as asthma, chronic obstructive pulmonary disease and cystic fibrosis. In this review, we examine the contribution of NFκB activation in respiratory diseases and recent advancements in the therapeutic use of decoy ODNs. In addition, we also highlight the limitations and challenges in use of decoy ODNs as therapeutic molecules, cellular uptake of decoy ODNs, and the current need for novel delivery systems to provide efficient delivery of decoy ODNs. Furthermore, this review provides a common platform for discussion on the existence of decoy ODNs, as well as outlining perspectives on the latest generation of delivery systems that encapsulate decoy ODNs and target NFκB in respiratory diseases.

Essential sufficiency of zinc, ω-3 polyunsaturated fatty acids, vitamin D and magnesium for prevention and treatment of COVID-19, diabetes, cardiovascular diseases, lung diseases and cancer

Despite the development of a number of vaccines for COVID-19, there remains a need for prevention and treatment of the virus SARS-CoV-2 and the ensuing disease COVID-19. This report discusses the key elements of SARS-CoV-2 and COVID-19 that can be readily treated: viral entry, the immune system and inflammation, and the cytokine storm. It is shown that the essential nutrients zinc, ω-3 polyunsaturated fatty acids (PUFAs), vitamin D and magnesium provide the ideal combination for prevention and treatment of COVID-19: prevention of SARS-CoV-2 entry to host cells, prevention of proliferation of SARS-CoV-2, inhibition of excessive inflammation, improved control of the regulation of the immune system, inhibition of the cytokine storm, and reduction in the effects of acute respiratory distress syndrome (ARDS) and associated non-communicable diseases. It is emphasized that the non-communicable diseases associated with COVID-19 are inherently more prevalent in the elderly than the young, and that the maintenance of sufficiency of zinc, ω-3 PUFAs, vitamin D and magnesium is essential for the elderly to prevent the occurrence of non-communicable diseases such as diabetes, cardiovascular diseases, lung diseases and cancer. Annual checking of levels of these essential nutrients is recommended for those over 65 years of age, together with appropriate adjustments in their intake, with these services and supplies being at government cost. The cost:benefit ratio would be huge as the cost of the nutrients and the testing of their levels would be very small compared with the cost savings of specialists and hospitalization.

Blood eosinophil count-guided corticosteroid therapy and as a prognostic biomarker of exacerbations of chronic obstructive pulmonary disease: a systematic review and meta-analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and dyspnea, as well as an increase in the number of leukocytes in the airways, lungs, and pulmonary vessels. A 'One size fits all' approach to COPD patients with different clinical features may be considered outdated. The following are the two major objectives of this meta-analysis: the first is to determine if blood eosinophil counts (BEC) can serve as a prognostic biomarker of COPD outcomes, and the second is to determine which level of BEC is effective for inhaled corticosteroid (ICS) treatment.

METHODS

We searched articles published before 15 May 2021 in the following four electronic databases: Web of Science, Cochrane Library, EMBASE, and PubMed.

RESULTS

A total of 42 studies, comprising a sampling of 188,710 subjects, were summarized and compared in this meta-analysis. The rate ratio (RR) of exacerbations of COPD (ECOPD) between ICS and non-ICS treatment was statistically significant for the COPD patients with a baseline BEC ⩾ 2% or ⩾ 200 cells/μl, RR = 0.82 (0.73, 0.93) or 0.79 (0.70, 0.89) respectively, while the RR of ECOPD between ICS and non-ICS treatment was statistically insignificant for the COPD patients with baseline BEC < 2% or <200 cells/μl, RR = 0.97 (0.87, 1.08) or 0.97 (0.86, 1.08), suggested that ICS therapy was beneficial to the improvement of ECOPD in patients with a baseline BEC ⩾ 2% or BEC ⩾ 200 cells/μl.

CONCLUSION

Our research shows that a BEC ⩾ 200 cells/μl or ⩾2% is likely to become the cutoff value of ICS treatment for ECOPD. Moreover, we believe that the baseline BEC can be used as a biomarker for predicting ECOPD. The stability of BEC requires special attention.

Eosinopenia is a reliable marker of severe disease and unfavourable outcome in patients with COVID-19 pneumonia

BACKGROUND AND AIM

Viral pneumonia is the most relevant clinical presentation of COVID-19 which may lead to severe acute respiratory syndrome and even death. Eosinopenia was often noticed in patients with COVID-19 pneumonia, but its role is poorly investigated. The aim of the present study was to investigate the characteristics and clinical outcomes of patients with COVID-19 pneumonia and eosinopenia.

METHODS

We revised the records of consecutive patients with COVID-19 pneumonia admitted to our ER-COVID-19 area in order to compare clinical characteristics and outcomes of patients with and without eosinopenia. We considered the following clinical outcomes: 4-weeks survival; need for intensive respiratory support; and hospital discharge.

RESULTS

Out of first 107 consecutive patients with pneumonia and a positive COVID-19 nasopharyngeal swab, 75 patients showed undetectable eosinophil count (absolute eosinopenia). At 4 weeks, 38 patients (38.4%) had required intensive respiratory treatment, 25 (23.4%) deceased and 42 (39.2%) were discharged. Compared with patients without absolute eosinopenia, patients with absolute eosinopenia showed higher need of intensive respiratory treatment (49.3% vs 13.3%, P < .001), higher mortality (30.6% vs 6.2%, P .006) and lower rate of hospital discharge (28% vs 65.6%, P < .001). Binary logistic regression analyses including neutrophil, lymphocyte, eosinophil, basophil and monocyte counts showed that absolute eosinopenia was an independent factor associated with 4-weeks mortality, need for intensive respiratory support and hospital discharge.

CONCLUSIONS

Absolute eosinopenia is associated with clinical outcomes in patients with COVID-19 pneumonia and might be used as a marker to discriminate patients with unfavourable prognosis.

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

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

Eosinophils in the pathogenesis of pancreatic disorders

Eosinophils comprise approximately 1-4% of total blood leukocytes that reside in the intestine, bone marrow, mammary gland, and adipose tissues to maintain innate immunity in healthy individuals. Eosinophils have four toxic granules known as major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and eosinophil-derived neurotoxin (EDN), and upon degranulation, these granules promote pathogenesis of inflammatory diseases like allergy, asthma, dermatitis, and gastrointestinal disorders. Additionally, the role of eosinophils is underscored in exocrine disorders including pancreatitis. Chronic pancreatitis (CP) is an inflammatory disorder that occurs due to the alcohol consumption, blockage of the pancreatic duct, and trypsinogen mutation. Eosinophil levels are detected in higher numbers in both CP and pancreatic cancer patients compared with healthy individuals. The mechanistic understanding of chronic inflammation-induced pancreatic malignancy has not yet been reached and requires further exploration. This review provides a comprehensive summary of the epidemiology, pathophysiology, evaluation, and management of eosinophil-associated pancreatic disorders and further summarizes current evidence regarding risk factors, pathophysiology, clinical features, diagnostic evaluation, treatment, and prognosis of eosinophilic pancreatitis (EP) and pancreatic cancer.

5-lipoxygenase- and Glucocorticoid-dependent eosinophilia in a novel surgical model in mice

BACKGROUND

Subcutaneous implants of heat-coagulated egg white (egg white implants, EWI) induce intense local eosinophilia and prime for hyperreactivity following airway ovalbumin challenge. The roles of allergen sensitization, surgical trauma-induced glucocorticoids, and the 5-lipoxygenase (5-LO) pathway were hitherto unexplored in this model, in which quantitative recovery and large-scale purification of the eosinophils from the inflammatory site for functional and immunopharmacological studies are difficult to achieve.

METHODS

We overcame this limitation by shifting the implantation site to the peritoneal cavity (EWIp), thereby enabling quantitative leukocyte retrieval.

RESULTS

By day 7 post-surgery, eosinophil counts reached ~ 30% of all leukocytes recovered. Eosinophilia was prevented by: a) induction of allergen-specific oral tolerance to ovalbumin, the main allergen in egg white; b) inactivation of the 5-lipoxygenase pathway; c) blockade of endogenous glucocorticoid signaling by pretreatment with metirapone plus mifepristone before surgery. Highly purified eosinophils (~99% pure) could be obtained from the peritoneal exudate of EWIp-carrier mice in 2 simple, antibody-free steps. Preparative-scale yields, suitable for most biochemical, pharmacological, and molecular applications, were routinely obtained, and could be further enhanced through addition of pre-or post-surgery immunization steps (active or adoptive). The recovered eosinophils were fully functional in vivo, as demonstrated by the transfer of purified eosinophils into eosinophil-deficient Δdbl-GATA-1-KO mice, which upon subsequent challenge with eotaxin-1 present secondary accumulation of neutrophils, but not of mononuclear phagocytes.

CONCLUSION

These findings document glucocorticoid-, allergen- and 5-lipoxygenase-dependent eosinophilia, which makes EWIp carriers an abundant source of pure, nontransgenic eosinophils for immunopharmacological studies.

Initiation and Pathogenesis of Severe Asthma with Fungal Sensitization

Fungi represent one of the most diverse and abundant eukaryotes on earth, and their ubiquity and small proteolytically active products make them pervasive allergens that affect humans and other mammals. The immunologic parameters surrounding fungal allergies are still not fully elucidated despite their importance given that a large proportion of severe asthmatics are sensitized to fungal allergens. Herein, we explore fungal allergic asthma with emphasis on mouse models that recapitulate the characteristics of human disease, and the main leukocyte players in the pathogenesis of fungal allergies. The endogenous mycobiome may also contribute to fungal asthma, a phenomenon that we discuss only superficially, as much remains to be discovered.

Human RNase3 immune modulation by catalytic-dependent and independent modes in a macrophage-cell line infection model

The human RNase3 is a member of the RNaseA superfamily involved in host immunity. RNase3 is expressed by leukocytes and shows broad-spectrum antimicrobial activity. Together with a direct antimicrobial action, RNase3 exhibits immunomodulatory properties. Here, we have analysed the transcriptome of macrophages exposed to the wild-type protein and a catalytic-defective mutant (RNase3-H15A). The analysis of differently expressed genes (DEGs) in treated THP1-derived macrophages highlighted a common pro-inflammatory "core-response" independent of the protein ribonucleolytic activity. Network analysis identified the epidermal growth factor receptor (EGFR) as the main central regulatory protein. Expression of selected DEGs and MAPK phosphorylation were inhibited by an anti-EGFR antibody. Structural analysis suggested that RNase3 activates the EGFR pathway by direct interaction with the receptor. Besides, we identified a subset of DEGs related to the protein ribonucleolytic activity, characteristic of virus infection response. Transcriptome analysis revealed an early pro-inflammatory response, not associated to the protein catalytic activity, followed by a late activation in a ribonucleolytic-dependent manner. Next, we demonstrated that overexpression of macrophage endogenous RNase3 protects the cells against infection by Mycobacterium aurum and the human respiratory syncytial virus. Comparison of cell infection profiles in the presence of Erlotinib, an EGFR inhibitor, revealed that the receptor activation is required for the antibacterial but not for the antiviral protein action. Moreover, the DEGs related and unrelated to the protein catalytic activity are associated to the immune response to bacterial and viral infection, respectively. We conclude that RNase3 modulates the macrophage defence against infection in both catalytic-dependent and independent manners.

Eosinophils and childhood asthma

Eosinophils are a type of granulocyte with eosinophilic granules in the cytoplasm that play an important role in allergic and parasitic diseases. Eosinophils are important in the pathogenesis of asthma, and many studies have examined the relationship between them. In allergic eosinophilic asthma, eosinophils act not only as important effector cells but also as antigen-presenting cells in allergic inflammatory reactions. In nonallergic eosinophilic asthma, type 2 innate lymphoid cells in the airways play an important role in eosinophil activation. Direct methods, including bronchial biopsy, bronchoalveolar lavage, and the induced sputum test, are used to evaluate eosinophilic inflammatory reactions in patients with asthma, however, because of difficulty with their implementation, they are sometimes replaced by measurements of blood eosinophils, fraction of exhaled nitric oxide, and serum periostin level. However, these tests are less accurate than direct methods. For the treatment of patients with severe eosinophilic asthma, anti-interleukin-5 preparations such as mepolizumab, reslizumab, and benralizumab have recently been introduced and broadened the scope of asthma treatment. Although eosinophils are already known to play an important role in asthma, we expect that further studies will reveal more details of their action.

Hyper-eosinophilic syndrome: An uncommon cause of chronic abdominal pain in an elderly male

Hypereosinophilia is defined as an absolute eosinophil count of ≥1.5 × 10⁹/L, and its presence with involvement of at least one organ system defines the hypereosinophilic syndrome. It may occur with parasitic infestation, connective tissue disorder or rarely in clonal disorders such as eosinophilic leucaemia. Organ systems that may be involved include the cardiovascular, central nervous, respiratory and gastrointestinal systems. In the latter, a wide spectrum of clinical presentation may be seen from trivial, to debilitating or rarely fatal. We report an elderly male with a history of bronchial asthma, obstructive sleep apnoea and food allergy who presented with chronic abdominal pain and weight loss. Abdominal examination and routine evaluation were essentially normal other than a peripheral hyper-eosinophilia. We witnessed a brisk and lasting response to an elimination diet and corticosteroids.

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.

Murine Models of Eosinophil Function in Fungal and Viral Infections

Eosinophils are granulocytes that were historically considered to be terminally differentiated at the time of bone marrow egress. However, more recent evidence provides a new outlook on these cells as complex immunomodulators that are involved in host defense and homeostasis. Our work established a role for eosinophils as mediators of antiviral immune responses during influenza in hosts that were sensitized and challenged with fungal allergens. Herein, we describe methods for working with murine eosinophils in the context of influenza A virus.

The multiple functions and subpopulations of eosinophils in tissues under steady-state and pathological conditions

Eosinophils not only play a critical role in the pathogenesis of eosinophil-associated diseases, but they also have multiple important biological functions, including the maintenance of homeostasis, host defense against infections, immune regulation through canonical Th1/Th2 balance modulation, and anti-inflammatory and anti-tumorigenic activities. Recent studies have elucidated some emerging roles of eosinophils in steady-state conditions; for example, eosinophils contribute to adipose tissue metabolism and metabolic health through alternatively activated macrophages and the maintenance of plasma cells in intestinal tissue and bone marrow. Moreover, eosinophils exert tissue damage through eosinophil-derived cytotoxic mediators that are involved in eosinophilic airway inflammation, leading to diseases including asthma and chronic rhinosinusitis with nasal polyps characterized by fibrin deposition through excessive response by eosinophils-induced. Thus, eosinophils possessing these various effects reflect the heterogenous features of these cells, which suggests the existence of distinct different subpopulations of eosinophils between steady-state and pathological conditions. Indeed, a recent study demonstrated that instead of dividing eosinophils by classical morphological changes into normodense and hypodense eosinophils, murine eosinophils from lung tissue can be phenotypically divided into two distinct subtypes: resident eosinophils and inducible eosinophils gated by Siglec-F^int CD62L⁺ CD101^low and Siglec-F^high CD62L^- CD101^high, respectively. However, it is difficult to explain every function of eosinophils by rEos and iEos, and the relationship between the functions and subpopulations of eosinophils remains controversial. Here, we overview the multiple roles of eosinophils in the tissue and their biological behavior in steady-state and pathological conditions. We also discuss eosinophil subpopulations.

Mechanisms of Allergen Immunotherapy in Allergic Rhinitis

PURPOSE OF REVIEW

Allergic rhinitis (AR) is a chronic inflammatory immunoglobulin (Ig) E-mediated disease of the nasal mucosa that can be triggered by the inhalation of seasonal or perennial allergens. Typical symptoms include sneezing, rhinorrhea, nasal itching, nasal congestion and symptoms of allergic conjunctivitis. AR affects a quarter of the population in the United States of America and Europe.

RECENT FINDINGS

AR has been shown to reduce work productivity in 36-59% of the patients with 20% reporting deteriorated job attendance. Moreover, 42% of children with AR report reduced at-school productivity and lower grades. Most importantly, AR impacts the patient's quality of life, due to sleep deprivation. However, a proportion of patients fails to respond to conventional medication and opts for the allergen immunotherapy (AIT), which currently is the only disease-modifying therapeutic option. AIT can be administered by either subcutaneous (SCIT) or sublingual (SLIT) route. Both routes of administration are safe, effective, and can lead to tolerance lasting years after treatment cessation. Both innate and adaptive immune responses that contribute to allergic inflammation are suppressed by AIT. Innate responses are ameliorated by reducing local mast cell, basophil, eosinophil, and circulating group 2 innate lymphoid cell frequencies which is accompanied by decreased basophil sensitivity. Induction of allergen-specific blocking antibodies, immunosuppressive cytokines, and regulatory T and B cell phenotypes are key pro-tolerogenic adaptive immune responses.

CONCLUSION

A comprehensive understanding of these mechanisms is necessary for optimal selection of AIT-responsive patients and monitoring treatment efficacy. Moreover, it could inspire novel and more efficient AIT approaches.

"NETs and EETs, a Whole Web of Mess"

Neutrophils and eosinophils are granulocytes that have very distinct functions. Neutrophils are first responders to external threats, and they use different mechanisms to control pathogens. Phagocytosis, reactive oxygen species, and neutrophil extracellular traps (NETs) are some of the mechanisms that neutrophils utilize to fight pathogens. Although there is some controversy as to whether NETs are in fact beneficial or detrimental to the host, it mainly depends on the biological context. NETs can contribute to disease pathogenesis in certain types of diseases, while they are also undeniably critical components of the innate immune response. On the contrary, the role of eosinophils during host immune responses remains to be better elucidated. Eosinophils play an important role during helminthic infections and allergic responses. Eosinophils can function as effector cells in viral respiratory infections, gut bacterial infections, and as modulators of immune responses by driving the balance between Th1 and Th2 responses. In particular, eosinophils have biological activities that appear to be quite similar to those of neutrophils. Both possess bactericidal activity, can activate proinflammatory responses, can modulate adaptive immune responses, can form extracellular traps, and can be beneficial or detrimental to the host according to the underlying pathology. In this review we compare these two cell types with a focus on highlighting their numerous similarities related to extracellular traps.

Basophils and Eosinophils in Nematode Infections

Helminths remain one of the most prolific pathogens in the world. Following infection helminths interact with various epithelial cell surfaces, including skin, lung, and gut. Recent works have shown that epithelial cells produce a series of cytokines such as TSLP, IL-33, and IL-25 that lead to the induction of innate and acquired type 2 immune responses, which we named Type 2 epithelial cytokines. Although basophils and eosinophils are relatively rare granulocytes under normal conditions (0.5% and 5% in peripheral blood, respectively), both are found with increased frequency in type 2 immunity, including allergy and helminth infections. Recent reports showed that basophils and eosinophils not only express effector functions in type 2 immune reactions, but also manipulate the response toward helminths. Furthermore, basophils and eosinophils play non-redundant roles in distinct responses against various nematodes, providing the potential to intervene at different stages of nematode infection. These findings would be helpful to establish vaccination or therapeutic drugs against nematode infections.

Physical Exercise as a Multimodal Tool for COVID-19: Could It Be Used as a Preventive Strategy?

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or coronavirus disease 2019 (COVID-19) is a novel coronavirus not previously recognized in humans until late 2019. On 31 December 2019, a cluster of cases of pneumonia of unspecified etiology was reported to the World Health Organization in China. The availability of adequate SARS-CoV-2 drugs is also limited, and the efficacy and safety of these drugs for COVID-2019 pneumonia patients need to be assessed by further clinical trials. For these reasons, there is a need for other strategies against COVID-19 that are capable of prevention and treatment. Physical exercise has proven to be an effective therapy for most chronic diseases and microbial infections with preventive/therapeutic benefits, considering that exercise involves primary immunological mediators and/or anti-inflammatory properties. This review aimed to provide an insight into how the implementation of a physical exercise program against COVID-19 may be a useful complementary tool for prevention, which can also enhance recovery, improve quality of life, and provide immune protection against SARS-CoV-2 virus infection in the long term. In summary, physical exercise training exerts immunomodulatory effects, controls the viral gateway, modulates inflammation, stimulates nitric oxide synthesis pathways, and establishes control over oxidative stress.

Multiple Biological Aspects of Eosinophils in Host Defense, Eosinophil-Associated Diseases, Immunoregulation, and Homeostasis: Is Their Role Beneficial, Detrimental, Regulator, or Bystander?

Eosinophils are innate immune leukocytes and play important roles as terminal effector cells owing to their mediators, such as tissue-destructive cationic proteins, cytokines, chemokines, and lipid mediators. Historically, they are not only considered an important player in host defense against parasitic, viral, fungal, and bacterial infections but also implicated in the pathogenesis of eosinophil-associated diseases, such as allergic rhinitis, asthma, eosinophilic chronic rhinosinusitis, esophagitis, atopic dermatitis, myopathies, and hypereosinophilic syndrome. Moreover, recent studies have shown that eosinophils have an immune regulatory and homeostatic function. Interestingly, there is emerging evidence that eosinophils are accumulated through adoptive T-helper 2 (Th2) and innate Th2 responses, mechanisms of the classical allergen-specific immunoglobulin E (IgE)-mediated response, and group 2 innate lymphoid cell-derived interleukin-5, respectively. Furthermore, in agreement with current concepts of eosinophil subtypes, it has been shown that resident and phenotypically distinct eosinophils, i.e., resident and recruited inflammatory eosinophils, exist in inflamed sites, and each has different functions. Thus, the classical and novel studies suggest that eosinophils have multiple functions, and their roles may be altered by the environment. In this article, we review multiple biological aspects of eosinophils (novel and classical roles), including their beneficial and detrimental effects, immunoregulation, and homeostatic function.

Clinical Relevance of Plasma Concentrations of MBL in Accordance with IgE Levels in Children Diagnosed with Bronchial Asthma

Background and objectives: Bronchial asthma is a heterogeneous, multifactorial pulmonary disease characterized by variable airway obstruction caused by chronic inflammation. Our study investigates the clinical relevance of MBL plasma levels in accordance with IgE values in children who attended a pediatric consult for respiratory symptoms with bronchial asthma. Materials and Methods: The study population consists of patients <18-years-old and included 43 patients with bronchial asthma and 64 age-matched healthy subjects as a control group. We used the ELISA Human MBL Immunoassay kit and the electrochemiluminescence immunoassay (ECLIA) kit for IgE determination. Results: Our results show significantly different distributions of patients in the bronchial asthma group and control group. The measured values were within the normal range for most controls, while the bronchial asthma patients displayed higher values of plasma MBL and IgE levels. We observed a wider heterogeneity in MBL concentrations in bronchial asthma patients when compared to the healthy age-matched controls. Our results also suggest a potential clinical usefulness of plasma MBL concentrations in accordance with IgE and eosinophil cells levels in the diagnosis of bronchial asthma, and our results may suggest a prognostic role of MBL in the evolution of asthmatic disease; however, further studies are necessary to confirm these findings. Conclusions: We can say that plasma MBL concentrations present a relative diagnostic role for bronchial asthma in pediatric patients and may suggest a more severe disease progression; however, further studies are needed to elucidate the role played by MBL in the determination and evolution of this disease.