Eosinophil Subtypes in Adults with Asthma and Adults with Chronic Obstructive Pulmonary Disease

Type 2 inflammation, a common denominator in chronic airway disease?

PURPOSE OF REVIEW

This review addresses the growing understanding that a specific subset of patients with a respiratory disease, including asthma, chronic obstructive pulmonary disease (COPD), or bronchiectasis may have one thing in common: type 2 inflammation. In the era of personalized medicine, we need to refine clinical markers combined with molecular and cellular endotyping to improve patient outcomes.

RECENT FINDINGS

Recent literature reveals that type 2 markers such as blood eosinophils, fractional exhaled nitric oxide (FeNO), and immunglobulin E (IgE), can provide valuable insights into disease progression, exacerbation risk, and treatment response, but their stability remains to be investigated. Treating asthma and COPD patients with biologics to target IL-4/IL-13, IL-5, and alarmins have shown potential, although efficacy varied. In bronchiectasis, a subset of patients with type 2 inflammation may benefit from corticosteroid therapy, despite broader concerns regarding its use.

SUMMARY

This underscores the importance of improved disease endotyping to better characterize patients who may benefit from targeted therapies. In clinical practice, personalized treatment based on inflammatory profiles has been shown to improve outcomes in heterogeneous lung diseases. Future research needs to focus on validating reliable biomarkers and optimizing clinical trial designs to advance therapeutic strategies in respiratory diseases.

The Emerging Role of Alarmin-Targeting Biologics in the Treatment of Patients With COPD

TOPIC IMPORTANCE

COPD is a complex, heterogeneous lung disease characterized by persistent airflow limitation secondary to airways and parenchymal abnormalities, and respiratory symptoms, including dyspnea, fatigue, chronic cough, and sputum production. Cigarette smoke exposure is a major contributor to COPD; however, inhalation of toxic particles and other environmental and host factors can contribute to its genesis. Over time, the clinical course is frequently punctuated by exacerbations that further accelerate lung function decline and increase exacerbation risk. Despite current optimal therapy, many patients remain symptomatic, have exacerbations, and have increased morbidity, mortality, and health care costs. This review focuses on current knowledge of COPD pathophysiology, the role of inflammatory mechanisms, and the potential use of biologics to modulate these mechanisms.

REVIEW FINDINGS

The inflammatory response in COPD includes both type 1 and type 2 immune cells. Type 2 inflammation is suggested by eosinophilia in a significant proportion of patients with COPD. Studies targeting IL-5 in patients with COPD have failed to demonstrate significant reductions in exacerbations, suggesting that eosinophil modulation alone may be insufficient to treat COPD. Based on a better understanding of the disease and role of alarmins, with a broader role in the inflammatory cascade, it is likely that some biologics may benefit certain COPD endotypes. Ongoing trials will provide information about which groups can benefit from the blocking of specific pathways (eg, IL-5, IL-4/IL-13, IL-33, thymic stromal lymphopoietin).

SUMMARY

Biologics targeting inflammatory pathways may be effective treatments for specific patients with COPD.

Novel biomarkers in asthma

PURPOSE OF REVIEW

Asthma is a common global respiratory disease characterized by airway inflammation. It is a heterogenous group of disorders with overlapping biological mechanisms. This review will discuss the current state of the use of biomarkers in asthma with an eye to the future. The identification of biomarkers has advanced our understanding of inflammatory pathways in asthma and aided in development of targeted therapies. However, even with similar inflammatory biomarkers, not all patients respond uniformly. Thus, further research into novel biomarkers in asthma is needed.

RECENT FINDINGS

Recent literature highlights several key themes in biomarker research for asthma. Biomarkers can be derived from various sources, including sputum, blood, urine, and exhaled breath. Historically, studies have focused on eosinophilic inflammation, yet total blood eosinophil counts do not capture asthma pathology and treatment responses. Recent investigations explore eosinophil activity as well as eosinophil subpopulations based on surface protein expressions. Mast cell involvement, their mediators, and club cell secretory protein are further being examined across different asthma molecular phenotypes.

SUMMARY

The complexity of inflammatory pathways in asthma, influenced by various factors, underscores the inadequacy of relying on a single biomarker at one time point. Continued research is essential to identify appropriate biomarkers.

Inflammatory and homeostatic roles of eosinophil subpopulations in chronic rhinosinusitis with nasal polyp pathogenesis

Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) mainly expresses type-2 endotype, featuring eosinophils as a main player in the inflammatory process. Prolonged eosinophilia in the tissues of asthma and CRSwNP patients has been associated with structural changes, leading to fixed airflow obstruction in asthma and nasal polyposis in CRSwNP. This suggests that eosinophils may belong to different subgroups playing distinct roles in pathogenesis. Recent studies highlight the roles of inflammatory eosinophils (iEOS) in driving inflammation and tissue damage, whereas tissue-resident eosinophils (rEOS) maintain homeostasis and tissue repair in the airway. Therefore, understanding both roles of eosinophil subpopulations is crucial for better CRSwNP management, including enhancing the diagnosis accuracy, predicting recurrence, and optimizing treatment strategies.

Nasal production of IL-26 involving T cells in smokers with and without chronic obstructive pulmonary disease

BACKGROUND

Novel specific therapy in chronic obstructive pulmonary disease (COPD) will require accessible targets for endotyping to identify responsive patients. It is therefore of interest that IL-26 in the bronchoalveolar space is enhanced and associates with bronchoalveolar pathology among long-term smokers (LTS) with and without COPD.

OBJECTIVE

We determined whether IL-26 in the nasal cavity can be produced by T cells and associates with bronchoalveolar pathology and clinical symptoms in LTS with and without COPD.

METHODS

We characterized LTS with and without COPD plus healthy nonsmokers by radiology, spirometry, modified Medical Research Council scale, and St George Respiratory Questionnaire. We determined extracellular IL-26 concentrations (via ELISA) in nasal (NAL) and bronchoalveolar lavage (BAL) samples, BAL neutrophil counts, and NAL IL-26+ T-cell expression (via flow cytometry).

RESULTS

The NAL IL-26 concentrations were higher in LTS with COPD than in healthy nonsmokers. These enhanced IL-26 concentrations displayed a positive correlation with forced expiratory volume in 1 second/forced vital capacity ratio. The IL-26 protein was expressed in CD4+ and CD8+ T cells, but only a small portion of these cells coexpressed IL-15, IL-17A, or IL-22 in LTS with COPD. In this group, IL-26+ CD3+ T cells displayed a negative correlation with forced expiratory volume in 1 second, as did with extracellular NAL IL-26 concentrations. The relative mean fluorescence intensity for CD8+ T cells displayed a negative correlation with modified Medical Research Council and St George Respiratory Questionnaire score.

CONCLUSION

In the nasal cavity, IL-26 can be produced by local T cells. This IL-26 reflects bronchoalveolar pathology and clinical symptoms, thereby constituting an accessible target with potential for clinically relevant endotyping in COPD.

Progress in research on induced sputum in asthma: a narrative review

OBJECTIVE

To explore the clinical significance of induced sputum in asthma through a retrospective analysis of induced sputum in patients with asthma.

DATA SOURCES

The data and references cited in this article were obtained from PubMed, Sci-Hub, and Web of Science.

STUDY SELECTION

Observational studies with reliable data were selected.

CONCLUSIONS

The cytological count, -omics, and pathogen detection of induced sputum are helpful for the clinical diagnosis of asthma and in guiding medication choices.

Analysis of the effects of group progressive resistance training on inflammatory markers, cardiovascular fitness parameters, and respiratory function in elderly patients with chronic obstructive pulmonary disease

Background

To investigate the effects of implementing group progressive resistance training on Maximal Oxygen consumption (VO2max), Maximum Ventilation per minute (VEmax), Maximal Oxygen pulse (O2pulsemax), Maximum Heart Rate (HRmax), and Modified Medical Research Council dyspnea scale (mMRC) in elderly patients with chronic obstructive pulmonary disease.

Methods

A total number of 114 elderly patients with chronic obstructive pulmonary disease treated in the hospital from May 2022 to May 2024 were collected and divided into two groups based on different training methods. The conventional group (n=57) received routine rehabilitation training, while the organization group (n=57) received group progressive resistance training. Cardio - pulmonary Exercise Testing (CPET) parameters, serum inflammatory factors, lung function indicators, and mMRC score were compared between two groups before training, 2 weeks of training, and 4 weeks of training.

Results

Before training, there was no significant difference between the two groups regarding training compliance, CPET parameters, inflammatory factors, and mMRC score. After 2-4 weeks of training, both groups showed improvements in training frequency, intensity, autonomous training, and increases in VO2MAX, VEmax, O2pulsemax, and HRmax. However, the organization group had higher scores in these areas and lower levels of inflammatory factors (IL-8, IL-18, IL-6, IL-12) and mMRC scores compared to the conventional group, with statistically significant differences (P<0.05).

Conclusions

Group progressive resistance training can help improve the compliance of elderly patients with chronic obstructive pulmonary disease with training, reduce the body's inflammatory response, improve VO2MAX, VEmax, O2pulsemax, and HRmax levels, and alleviate breathing difficulties.

Eosinophils: old cells, new directions

Eosinophils are polymorphonuclear cells that have progressively gained attention due to their involvement in multiple diseases and, more recently, in various homeostatic processes. Their well-known roles range from asthma and parasitic infections to less prevalent diseases such as eosinophilic granulomatosis with polyangiitis, eosinophilic esophagitis, and hypereosinophilic syndrome. In recent years, various biological therapies targeting these cells have been developed, altering the course of eosinophilic pathologies. Recent research has demonstrated differences in eosinophil subtypes and their functions. The presence of distinct classes of eosinophils has led to the theory of resident eosinophils (rEos) and inflammatory eosinophils (iEos). Subtype differences are determined by the pattern of protein expression on the cell membrane and the localization of eosinophils. Most of this research has been conducted in murine models, but several studies confirm these findings in peripheral blood and tissue. The objective of this review is to provide a comprehensive analysis of eosinophils, by recent findings that divide this cell line into two distinct populations with different functions and purposes.

Eosinophils in chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous lung condition characterised by chronic respiratory symptoms, fixed airway obstruction and persistent inflammation that leads to a progressive airflow limitation. Although COPD has traditionally been linked to neutrophilic inflammation, recent studies have identified a subset of patients - approximately 20%-40% - with elevated eosinophil levels in blood and sputum. Emerging evidence suggests that eosinophilic inflammation has a pivotal role in a subset of COPD patients and may influence disease progression, exacerbation frequency and therapeutic responses. This narrative review provides a comprehensive analysis of the role of eosinophils in COPD with particular attention to their role as biomarkers in blood and sputum. We evaluate the prevalence of eosinophilic inflammation in COPD exanimating different thresholds used in blood and in sputum to define it. In addition, we focus on eosinophilic COPD phenotype as a treatable trait, emphasising recent evidence that supports the effectiveness of biological target therapy.

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.

Mepolizumab depletes inflammatory but preserves homeostatic eosinophils in severe asthma

BACKGROUND

Eosinophils are key therapeutic targets in severe asthma that are suppressed by IL5 (mepolizumab) and IL5 receptor (benralizumab) blockade. The effect of IL5 pathway biologics on recently described homeostatic (hEOs) and inflammatory (iEOs) eosinophil subsets is unknown. We aimed to determine the relative impact of mepolizumab and benralizumab treatment on eosinophil subset and phenotype, and explore clinical associations of eosinophil subsets with severe asthma characteristics and treatment response.

METHODS

We performed a cross-sectional observational study of severe asthma (eosinophilic n = 32, non-eosinophilic n = 23, mepolizumab-treated n = 25), with longitudinal follow-up of 30 eosinophilic participants at two timepoints (4-24 weeks, >24 weeks) post-commencement of mepolizumab (n = 20) or benralizumab (n = 10). Blood hEOs and iEOs were measured by flow cytometry assessment of surface CD62L protein.

RESULTS

iEO proportion was significantly lower in mepolizumab-treated participants in both the cross-sectional and longitudinal study. Mepolizumab and benralizumab depleted iEOs to a similar extent, however a significantly greater number of hEOs remained in mepolizumab participants at follow-up. Greater iEO proportion correlated with poorer asthma control in eosinophilic but not non-eosinophilic asthma. Higher residual iEO proportion correlated with poorer asthma control in mepolizumab-treated individuals. Reduced blood eosinophil viability was observed in around half of mepolizumab-treated participants, which was associated with significantly better asthma control and spirometry.

CONCLUSIONS

Mepolizumab depletes iEOs and reduces circulating eosinophil viability in severe asthma but preserves a residual population of circulatory hEOs. In contrast benralizumab depleted both iEOs and hEOs. Higher iEO abundance and eosinophil viability are associated with poorer clinical outcomes following mepolizumab-treatment. Monitoring circulating eosinophil phenotype and viability may be useful to predict biologic treatment response in severe asthma.

Does Eosinophil Heterogeneity Translate into Functional Diversity? A Review of the Evolving Paradigm of Eosinophil Heterogeneity in Asthma

This review provides an overview of evidence supporting the existence of distinct homeostatic and inflammatory eosinophil subpopulations in health and disease. Particular emphasis is placed on describing the phenotypic and functional roles of these eosinophil subtypes in asthma, as well as the phenotypic changes induced by clinical therapy with the anti-IL-5 biologic agent, mepolizumab. Improved understanding of distinct eosinophil phenotypes may enable targeting of select subpopulations in the treatment of patients with type 2 inflammatory diseases such as asthma.

The Current Molecular and Cellular Landscape of Chronic Obstructive Pulmonary Disease (COPD): A Review of Therapies and Efforts towards Personalized Treatment

Chronic obstructive pulmonary disease (COPD) ranks as the third leading cause of global illness and mortality. It is commonly triggered by exposure to respiratory irritants like cigarette smoke or biofuel pollutants. This multifaceted condition manifests through an array of symptoms and lung irregularities, characterized by chronic inflammation and reduced lung function. Present therapies primarily rely on maintenance medications to alleviate symptoms, but fall short in impeding disease advancement. COPD's diverse nature, influenced by various phenotypes, complicates diagnosis, necessitating precise molecular characterization. Omics-driven methodologies, including biomarker identification and therapeutic target exploration, offer a promising avenue for addressing COPD's complexity. This analysis underscores the critical necessity of improving molecular profiling to deepen our comprehension of COPD and identify potential therapeutic targets. Moreover, it advocates for tailoring treatment strategies to individual phenotypes. Through comprehensive exploration-based molecular characterization and the adoption of personalized methodologies, innovative treatments may emerge that are capable of altering the trajectory of COPD, instilling optimism for efficacious disease-modifying interventions.

Eosinophils and Cognitive Impairment in Schizophrenia: A New Perspective

Schizophrenia is a complex psychiatric disorder characterized by a wide array of cognitive impairments. While research has predominantly focused on the neurological aspects of schizophrenia, emerging evidence suggests that the immune system, specifically eosinophils, may play a significant role in the cognitive deficits associated with the disorder. This review presents a novel perspective on the interplay between eosinophils and cognitive impairment in schizophrenia. Eosinophils, traditionally associated with allergic responses and inflammation, have garnered limited attention within the realm of neuropsychiatry. Recent studies have hinted at a potential link between eosinophil activation and the pathogenesis of schizophrenia. In this comprehensive review, we delve into the world of eosinophils, elucidating their nature, functions, and interactions with the immune system. We examine the cognitive deficits observed in individuals with schizophrenia and discuss existing theories on the etiology of these impairments, focusing on immune system involvement. The paper also highlights the evolving body of research that supports the idea of eosinophilic influence on schizophrenia-related cognitive deficits. Furthermore, we explore potential mechanisms through which eosinophils may exert their effects on cognitive function in schizophrenia, including interactions with other immune cells and inflammatory pathways. By discussing the clinical implications and potential therapeutic avenues stemming from this newfound perspective, we underscore the practical significance of this emerging field of research. While this paper acknowledges the limitations and challenges inherent in studying eosinophils within the context of schizophrenia, it serves as a posit for novel thought in this vexing disease space as well as a call to action for future research endeavors. By providing a comprehensive survey of the existing literature and posing unanswered questions, we aim to inspire a reimagining of the relationship between eosinophils and cognitive impairment in schizophrenia, ultimately advancing our understanding and treatment of this debilitating disorder.

Exploring novel perspectives on eosinophilic inflammation in severe asthma

Two recent articles by the same research group documented that patients with severe eosinophilic asthma exhibit an increased proportion of a subtype of eosinophils, namely CD62Llow inflammatory eosinophils (iEos) and identified an intriguing correlation between such iEos and asthma control scores. Moreover, CD62Llow iEos were reduced after treatment with the anti-IL-5 monoclonal antibody mepolizumab. In the future, we believe that eosinophil subtypes could represent a useful biomarker in severe eosinophilic asthma, helping clinicians characterize patient endotypes and monitoring the response to biological drugs.

Comprehensive Nomograms Using Routine Biomarkers Beyond Eosinophil Levels: Enhancing Predictability of Corticosteroid Treatment Outcomes in AECOPD

Purpose

Patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) exhibit heterogeneous responses to corticosteroid treatment. We aimed to determine whether combining eosinophil levels with other routine clinical indicators can enhance the predictability of corticosteroid treatment outcomes and to come up with a scoring system.

Patients and Methods

Consecutive patients admitted with AECOPD receiving corticosteroid treatment between July 2013 and March 2022 at Beijing Chao-Yang Hospital were retrospectively analyzed. Data on patients' demographics, smoking status, hospitalization for AECOPD in the previous year, comorbidities, blood laboratory tests, in-hospital treatment and clinical outcomes were collected. Least absolute shrinkage and selection operator (LASSO) regression and backward logistic regression were used for predictor selection, and predictive nomograms were developed. The discrimination and calibration of the nomograms were assessed using the area under the receiver operating curve (AUC) and calibration plots. Internal validation was performed using the 500-bootstrap method, and clinical utility was evaluated using decision curve analysis (DCA).

Results

Among the 3254 patients included, 804 (24.7%) had treatment failure. A nomogram of eosinophils, platelets, C-reactive protein (CRP), low density lipoprotein cholesterol, prognostic nutritional index (PNI), hospitalization for AECOPD in the previous year, ischemic heart diseases and chronic hepatic disease was developed to predict treatment failure for patients with a smoking history. For patients without a smoking history, a nomogram of CRP, PNI, ischemic heart diseases and chronic hepatic disease was developed. Although the AUCs of these two nomograms were only 0.644 and 0.647 respectively, they were significantly superior to predictions based solely on blood eosinophil levels.

Conclusion

We developed easy-to-use comprehensive nomograms utilizing readily available clinical biomarkers related to inflammation, nutrition and immunity, offering modestly enhanced predictive value for treatment outcomes in corticosteroid-treated patients with AECOPD. Further investigations into novel biomarkers and additional patient data are imperative to optimize the predictive performance.

Does Chronic Obstructive Pulmonary Disease Originate from Different Cell Types?

The onset of chronic obstructive pulmonary disease (COPD) is heterogeneous, and current approaches to define distinct disease phenotypes are lacking. In addition to clinical methodologies, subtyping COPD has also been challenged by the reliance on human lung samples from late-stage diseases. Different COPD phenotypes may be initiated from the susceptibility of different cell types to cigarette smoke, environmental pollution, and infections at early stages that ultimately converge at later stages in airway remodeling and destruction of the alveoli when the disease is diagnosed. This perspective provides discussion points on how studies to date define different cell types of the lung that can initiate COPD pathogenesis, focusing on the susceptibility of macrophages, T and B cells, mast cells, dendritic cells, endothelial cells, and airway epithelial cells. Additional cell types, including fibroblasts, smooth muscle cells, neuronal cells, and other rare cell types not covered here, may also play a role in orchestrating COPD. Here, we discuss current knowledge gaps, such as which cell types drive distinct disease phenotypes and/or stages of the disease and which cells are primarily affected by the genetic variants identified by whole genome-wide association studies. Applying new technologies that interrogate the functional role of a specific cell type or a combination of cell types as well as single-cell transcriptomics and proteomic approaches are creating new opportunities to understand and clarify the pathophysiology and thereby the clinical heterogeneity of COPD.

Immune cell ratio and coagulation markers in assessing prognosis of asthma: a cross-sectional study from Saudi Arabia

Asthma affects a significant number of individuals in Saudi Arabia, with increasing prevalence worldwide, leading to a considerable impact on their quality of life and frequent hospitalizations. In this study, we aimed to explore the relationship between the immune cell ratio and coagulation markers, specifically to identify the occurrence of coagulation abnormalities associated with asthma. To achieve this, we assessed asthma history and severity using a questionnaire while analyzing coagulation biomarkers through venous blood samples. The biomarkers examined included d-dimer, prothrombin time (PT), partial thromboplastin time (PTT), and the international normalized ratio (INR). In addition, we evaluated various hematological parameters such as blood cell counts and hemoglobin (HGB) levels. Our findings revealed compelling evidence, showing significantly elevated levels of d-dimer and the eosinophil-to-neutrophil (ENR) ratio in asthma cases compared to the controls. Moreover, we observed a positive correlation between d-dimer levels and the ENR, with each unit increase in d-dimer associated with a 0.0006 increase in the ENR among asthma cases. These results highlight the potential of assessing ENR and d-dimer levels as predictive indicators for disease prognosis and the development of coagulation abnormalities in individuals with asthma. By shedding light on the relationship between immune cell ratios and coagulation markers in the context of asthma, our study contributes to a better understanding of disease progression and the associated complications. These insights can potentially lead to improved management strategies and better outcomes for asthma patients.

Eosinophils as potential biomarkers in respiratory viral infections

Eosinophils are bone marrow-derived granulocytes that, under homeostatic conditions, account for as much as 1-3% of peripheral blood leukocytes. During inflammation, eosinophils can rapidly expand and infiltrate inflamed tissues, guided by cytokines and alarmins (such as IL-33), adhesion molecules and chemokines. Eosinophils play a prominent role in allergic asthma and parasitic infections. Nonetheless, they participate in the immune response against respiratory viruses such as respiratory syncytial virus and influenza. Notably, respiratory viruses are associated with asthma exacerbation. Eosinophils release several molecules endowed with antiviral activity, including cationic proteins, RNases and reactive oxygen and nitrogen species. On the other hand, eosinophils release several cytokines involved in homeostasis maintenance and Th2-related inflammation. In the context of SARS-CoV-2 infection, emerging evidence indicates that eosinophils can represent possible blood-based biomarkers for diagnosis, prognosis, and severity prediction of disease. In particular, eosinopenia seems to be an indicator of severity among patients with COVID-19, whereas an increased eosinophil count is associated with a better prognosis, including a lower incidence of complications and mortality. In the present review, we provide an overview of the role and plasticity of eosinophils focusing on various respiratory viral infections and in the context of viral and allergic disease comorbidities. We will discuss the potential utility of eosinophils as prognostic/predictive immune biomarkers in emerging respiratory viral diseases, particularly COVID-19. Finally, we will revisit some of the relevant methods and tools that have contributed to the advances in the dissection of various eosinophil subsets in different pathological settings for future biomarker definition.