Basophil counts in PBMC populations during childhood acute wheeze/asthma are associated with future exacerbations

Basophil differentiation, heterogeneity, and functional implications

Basophils, rare granulocytes, have long been acknowledged for their roles in type 2 immune responses. However, the mechanisms by which basophils adapt their functions to diverse mammalian microenvironments remain unclear. Recent advancements in specific research tools and single-cell-based technologies have greatly enhanced our understanding of basophils. Several studies have shown that basophils play a role in maintaining homeostasis but can also contribute to pathology in various tissues and organs, including skin, lung, and others. Here, we provide an overview of recent basophil research, including cell development, characteristics, and functions. Based on an increasing understanding of basophil biology, we suggest that the precise targeting of basophil features might be beneficial in alleviating certain pathologies such as asthma, atopic dermatitis (AD), and others.

Impaired interferon response in plasmacytoid dendritic cells from children with persistent wheeze

BACKGROUND

Impaired interferon response and allergic sensitization may contribute to virus-induced wheeze and asthma development in young children. Plasmacytoid dendritic cells (pDCs) play a key role in antiviral immunity as critical producers of type I interferons. pDCs also express the high-affinity IgE receptor through which type I interferon production may be negatively regulated. Whether antiviral function of pDCs is associated with recurrent episodes of wheeze in young children is not well understood.

OBJECTIVE

We sought to evaluate the phenotype and function of circulating pDCs in children with a longitudinally defined wheezing phenotype.

METHODS

We performed multiparameter flow cytometry on PBMCs from 38 children presenting to the emergency department with an acute episode of respiratory wheeze and 19 controls. RNA sequencing on isolated pDCs from the same individuals was also performed. For each subject, their longitudinal exacerbation phenotype was determined using the Western Australia public hospital database.

RESULTS

We observed a significant depletion of circulating pDCs in young children with a persistent phenotype of wheeze. The same individuals also displayed upregulation of the FcεRI on their pDCs. Based on transcriptomic analysis, pDCs from these individuals did not mount a robust systemic antiviral response as observed in children who displayed a nonrecurrent wheezing phenotype.

CONCLUSIONS

Our data suggest that circulating pDC phenotype and function are altered in young children with a persistent longitudinal exacerbation phenotype. Expression of high-affinity IgE receptor is increased and their function as major interferon producers is impaired during acute exacerbations of wheeze.

LPS binding protein and activation signatures are upregulated during asthma exacerbations in children

Asthma exacerbations in children are associated with respiratory viral infection and atopy, resulting in systemic immune activation and infiltration of immune cells into the airways. The gene networks driving the immune activation and subsequent migration of immune cells into the airways remains incompletely understood. Cellular and molecular profiling of PBMC was employed on paired samples obtained from atopic asthmatic children (n = 19) during acute virus-associated exacerbations and later during convalescence. Systems level analyses were employed to identify coexpression networks and infer the drivers of these networks, and validation was subsequently obtained via independent samples from asthmatic children. During exacerbations, PBMC exhibited significant changes in immune cell abundance and upregulation of complex interlinked networks of coexpressed genes. These were associated with priming of innate immunity, inflammatory and remodelling functions. We identified activation signatures downstream of bacterial LPS, glucocorticoids and TGFB1. We also confirmed that LPS binding protein was upregulated at the protein-level in plasma. Multiple gene networks known to be involved positively or negatively in asthma pathogenesis, are upregulated in circulating PBMC during acute exacerbations, supporting the hypothesis that systemic pre-programming of potentially pathogenic as well as protective functions of circulating immune cells preceeds migration into the airways. Enhanced sensitivity to LPS is likely to modulate the severity of acute asthma exacerbations through exposure to environmental LPS.

Integrated Proteomics and Single-Cell Mass Cytometry Analysis Dissects the Immune Landscape of Ankylosing Spondylitis

Mass cytometry is a powerful single-cell technology widely adopted to depict immune cell heterogeneity in different contexts. However, this method is only capable of examining several dozens of proteins simultaneously and requires a prior knowledge of the markers to be analyzed. Here we propose that the integration of mass cytometry with shot-gun proteomics may serve as a valuable tool to achieve an in-depth understanding of the immune system. By implementing such a strategy, we investigated the immune landscape of ankylosing spondylitis (AS), a chronic inflammatory arthritis with unclear etiology. The proteome alteration in peripheral blood mononuclear cells (PBMCs) was investigated by quantitative proteomics, and then mass cytometry analysis was conducted to decipher the immunome by considering the signaling molecules identified with differential expression by proteomics. As a result, we identified a wide spectrum of proteins dysregulated in AS, e.g., upregulation of glycolytic enzymes, downregulation of lipid transporters, and dysregulation of chemokine signaling molecules involved in proinflammatory cytokine production and leucocyte migration. Moreover, the single-cell analysis showed the upregulation of chemokine signaling regulators in subclusters of both innate and adaptive immune cells in AS. In addition, correlation analysis unveiled the interplay among Phenograph-identified subclusters of monocytes, CD4+ T cells, and CD8+ T cells. Taken together, our findings demonstrated that the integration of mass spectrometry-based proteomics and single-cell mass cytometry may serve as a useful tool to reveal clinically relevant information regarding useful targets and cellular phenotypes that could be further exploited to develop novel therapeutic strategies.

Basophils from allergy to cancer

Human basophils, first identified over 140 years ago, account for just 0.5-1% of circulating leukocytes. While this scarcity long hampered basophil studies, innovations during the past 30 years, beginning with their isolation and more recently in the development of mouse models, have markedly advanced our understanding of these cells. Although dissimilarities between human and mouse basophils persist, the overall findings highlight the growing importance of these cells in health and disease. Indeed, studies continue to support basophils as key participants in IgE-mediated reactions, where they infiltrate inflammatory lesions, release pro-inflammatory mediators (histamine, leukotriene C₄: LTC₄) and regulatory cytokines (IL-4, IL-13) central to the pathogenesis of allergic diseases. Studies now report basophils infiltrating various human cancers where they play diverse roles, either promoting or hampering tumorigenesis. Likewise, this activity bears remarkable similarity to the mounting evidence that basophils facilitate wound healing. In fact, both activities appear linked to the capacity of basophils to secrete IL-4/IL-13, with these cytokines polarizing macrophages toward the M2 phenotype. Basophils also secrete several angiogenic factors (vascular endothelial growth factor: VEGF-A, amphiregulin) consistent with these activities. In this review, we feature these newfound properties with the goal of unraveling the increasing importance of basophils in these diverse pathobiological processes.

miR-3934 regulates the apoptosis and secretion of inflammatory cytokines of basophils via targeting RAGE in asthma

Background

Several miRNAs are now known to have clear connections to the pathogenesis of asthma. The present study focused on the potential role of miR-3934 during asthma development.

Methods

miR-3934 was detected as a down-regulated miRNA in basophils by sequencing analysis. Next, the expression levels of miR-3934 in peripheral blood mononuclear cells of 50 asthma patients and 50 healthy volunteers were examined by RT-qPCR methods. The basophils were then treated with AGEs and transfected with miR-3934 mimics. The apoptosis levels were examined by flow cytometry assay; and the expression levels of cytokines were detected using the ELISA kits. Finally, the Western blot was performed to examined the expression of key molecules in the TGF-β/Smad signaling pathway.

Results

miR-3934 was down-regulated in the basophils of asthmatic patients. The expression of the pro-inflammatory cytokines IL-6, IL-8 and IL-33 was enhanced in basophils from asthmatic patients, and this effect was partially reversed by transfection of miR-3934 mimics. Furthermore, receiver operating characteristics analysis showed that miR-3934 levels can be used to distinguish asthma patients from healthy individuals. miR-3934 partially inhibited advanced glycation end products-induced increases in basophil apoptosis by suppressing expression of RAGE.

Conclusion

Our results indicate that miR-3934 acts to mitigate the pathogenesis of asthma by targeting RAGE and suppressing TGF-β/Smad signaling.

Viral Induced Effects on a Vulnerable Epithelium; Lessons Learned From Paediatric Asthma and Eosinophilic Oesophagitis

The epithelium is integral to the protection of many different biological systems and for the maintenance of biochemical homeostasis. Emerging evidence suggests that particular children have epithelial vulnerabilities leading to dysregulated barrier function and integrity, that resultantly contributes to disease pathogenesis. These epithelial vulnerabilities likely develop in utero or in early life due to various genetic, epigenetic and environmental factors. Although various epithelia are uniquely structured with specific function, prevalent allergic-type epithelial diseases in children potentially have common or parallel disease processes. These include inflammation and immune response dysregulation stemming from atypical epithelial barrier function and integrity. Two diseases where aetiology and pathogenesis are potentially linked to epithelial vulnerabilities include Paediatric Asthma and Eosinophilic Oesophagitis (EoE). For example, rhinovirus C (RV-C) is a known risk factor for paediatric asthma development and is known to disrupt respiratory epithelial barrier function causing acute inflammation. In addition, EoE, a prevalent atopic condition of the oesophageal epithelium, is characterised by similar innate immune and epithelial responses to viral injury. This review examines the current literature and identifies the gaps in the field defining viral-induced effects on a vulnerable respiratory epithelium and resulting chronic inflammation, drawing from knowledge generated in acute wheezing illness, paediatric asthma and EoE. Besides highlighting the importance of epithelial structure and barrier function in allergic disease pathogenesis regardless of specific epithelial sub-types, this review focuses on the importance of examining other parallel allergic-type disease processes that may uncover commonalities driving disease pathogenesis. This in turn may be beneficial in the development of common therapeutics for current clinical management and disease prevention in the future.

Risk Factors Predicting Severe Asthma Exacerbations in Adult Asthmatics: A Real-World Clinical Evidence

PURPOSE

Minimizing the future risk of asthma exacerbation (AE) is one of the main goals of asthma management. We investigated prognostic factors for risk of severe AE (SAE) in a real-world clinical setting.

METHODS

This is an observational study evaluating subjects who were diagnosed with asthma and treated with anti-asthmatic medications from January 1995 to June 2018. Risk factors for SAE were analyzed in 2 treatment periods (during the initial 2 years and the following 3-10 years of treatment) using the big data of electronic medical records.

RESULTS

In this study, 5,058 adult asthmatics were enrolled; 1,335 (28.64%) experienced ≥ 1 SAE during the initial 2 years of treatment. Female sex, higher peripheral eosinophil/basophil counts, and lower levels of forced expiratory volume in 1 second (FEV1; %) were factors predicting the risk of SAEs (P < 0.001 for all). Higher serum total immunoglobulin E levels increased the risk of SAEs among the patients having ≤ 2 SAEs (P = 0.025). Patients with more frequent SAEs during the initial 2 years of treatment had significantly higher risks of SAEs during the following years of treatment (P < 0.001, for all) (patients with ≥ 4 SAEs, odds ratio [OR], 29.147; those with 3 SAEs, OR, 14.819; those with 2 SAEs, OR, 9.867; those with 1 SAE, OR, 5.116), had higher maintenance doses of systemic steroids, and showed more gradual decline in FEV1 (%) and FEV1/forced vital capacity levels maintained during the following years of treatment (P < 0.001 for all).

CONCLUSIONS

Asthmatics having risk factors for SAEs (female sex, higher peripheral eosinophil/basophil counts, and lower FEV1) should be strictly monitored to prevent future risk and improve clinical outcomes.

In infants with sufficient vitamin D status at birth, vitamin D supplementation does not impact immune development

BACKGROUND

Low vitamin D levels have been associated with allergic diseases. Vitamin D has potent immunomodulatory properties, but the mechanisms remain unclear. We have investigated the effect of oral vitamin D supplementation on circulating immune cell phenotypes in infants.

METHOD

A double-blinded randomised controlled trial was conducted to investigate the effect of oral vitamin D supplementation (400 IU/d) on eczema and immune development. A subset of 78 infants was included in this analysis. Phenotypic analysis of immune cell subsets was performed using flow cytometry.

RESULTS

Vitamin D supplementation resulted in median 25(OH)D levels of 80.5 vs 59.5 nmol/L in the placebo group at 3 months of age (P = .002) and 87.5 vs 77 nmol/L at 6 months of age (P = .08). We observed significant changes in immune cell composition from birth (cord blood) to 6 months of age. Vitamin D supplementation did not impact these changes, nor did immune cell composition correlate with plasma 25(OH)D levels. Through exploratory analysis, we identified possible associations with eczema development and increased abundance of naïve CD4^- T cells at birth, as well as associations with basophils, iNKT and central memory CD4⁺ T cells, and altered expression patterns of IgE receptor (FcεR1) on monocytes and dendritic cells with eczema at 6 months.

CONCLUSIONS

Vitamin D supplementation in infants who were vitamin D sufficient at birth did not affect developmental changes in immune cells during the first 6 months of life. However, immune cell profiles at birth and at 6 months of age were associated with early life eczema.

New Insights into the Implication of Mitochondrial Dysfunction in Tissue, Peripheral Blood Mononuclear Cells, and Platelets during Lung Diseases

Lung diseases such as chronic obstructive pulmonary disease, asthma, pulmonary arterial hypertension, or idiopathic pulmonary fibrosis are major causes of morbidity and mortality. Complex, their physiopathology is multifactorial and includes lung mitochondrial dysfunction and enhanced reactive oxygen species (ROS) release, which deserves increased attention. Further, and importantly, circulating blood cells (peripheral blood mononuclear cells-(PBMCs) and platelets) likely participate in these systemic diseases. This review presents the data published so far and shows that circulating blood cells mitochondrial oxidative capacity are likely to be reduced in chronic obstructive pulmonary disease (COPD), but enhanced in asthma and pulmonary arterial hypertension in a context of increased oxidative stress. Besides such PBMCs or platelets bioenergetics modifications, mitochondrial DNA (mtDNA) changes have also been observed in patients. These new insights open exciting challenges to determine their role as biomarkers or potential guide to a new therapeutic approach in lung diseases.

Precision medicine in childhood asthma

PURPOSE OF REVIEW

Childhood asthma is a heterogeneous disease and many children have uncontrolled disease. Therefore an individualized approach is needed to improve asthma outcomes in children. Precision medicine using clinical characteristics, biomarkers, and the rapidly involving field of genomics and pharmacogenomics aims to achieve asthma control and reduce future risks with less side-effects in individual children with asthma.

RECENT FINDINGS

It is not yet possible to select treatment options on clinical characteristics. Novel monoclonal antibodies are efficacious in patients with severe, eosinophilic asthma. Reduced lung function growth and early decline is a prevalent finding in children with persistent asthma. Pharmacogenetic studies have identified children at risk for cortisol suppression when using inhaled corticosteroids.

SUMMARY

Clinical characteristics and simple biomarkers like eosinophils, IgE, and the fraction of exhaled nitric oxide may be used in clinical practice for a basic precision medicine approach, deciding which children will have the best chance to respond to inhaled corticosteroids and to the biologicals omalizumab and mepolizumab.Further application of pharmacogenomics and breathomics needs additional studies before they can be applied as tools for precision medicine in individual children with asthma.

Mitochondrial Function in Peripheral Blood Mononuclear Cells (PBMC) Is Enhanced, Together with Increased Reactive Oxygen Species, in Severe Asthmatic Patients in Exacerbation

Asthma is a chronic inflammatory lung syndrome with an increasing prevalence and a rare but significant risk of death. Its pathophysiology is complex, and therefore we investigated at the systemic level a potential implication of oxidative stress and of peripheral blood mononuclear cells’ (PBMC) mitochondrial function. Twenty severe asthmatic patients with severe exacerbation (GINA 4–5) and 20 healthy volunteers participated at the study. Mitochondrial respiratory chain complexes activities using different substrates and reactive oxygen species (ROS) production were determined in both groups by high-resolution respirometry and electronic paramagnetic resonance, respectively. Healthy PBMC were also incubated with a pool of plasma of severe asthmatics or healthy controls. Mitochondrial respiratory chain complexes activity (+52.45%, p = 0.015 for V_ADP) and ROS production (+34.3%, p = 0.02) were increased in asthmatic patients. Increased ROS did not originate mainly from mitochondria. Plasma of severe asthmatics significantly increased healthy PBMC mitochondrial dioxygen consumption (+56.8%, p = 0.031). In conclusion, such asthma endotype, characterized by increased PMBCs mitochondrial oxidative capacity and ROS production likely related to a plasma constituent, may reflect activation of the immune system. Further studies are needed to determine whether increased PBMC mitochondrial respiration might have protective effects, opening thus new therapeutic approaches.

Progressive increase of FcεRI expression across several PBMC subsets is associated with atopy and atopic asthma within school-aged children

BACKGROUND

Antigen-specific IgE binds the Fcε receptor I (FcεRI) expressed on several types of immune cells, including dendritic cells (DCs). Activation of FcεRI on DCs in atopics has been shown to modulate immune responses that potentially contribute to asthma development. However, the extent to which DC subsets differ in FcεRI expression between atopic children with or without asthma is currently not clear. This study aimed to analyse the expression of FcεRI on peripheral blood mononuclear cells (PBMCs) from atopic children with and without asthma, and non-atopic/non-asthmatic age-matched healthy controls.

METHODS

We performed multiparameter flow cytometry on PBMC from 391 children across three community cohorts and one clinical cohort based in Western Australia.

RESULTS

We confirmed expression of FcεRI on basophils, monocytes, plasmacytoid and conventional DCs, with higher proportions of all cell populations expressing FcεRI in atopic compared to non-atopic children. Further, we observed that levels of FcεRI expression were elevated across plasmacytoid and conventional DC as well as basophils in atopic asthmatic compared to atopic non-asthmatic children also after adjusting for serum IgE levels.

CONCLUSION

Our data suggest that the expression pattern of FcεRI on DC and basophils differentiates asthmatic from non-asthmatic atopic children. Given the significant immune modulatory effects observed as a consequence of FcεRI expression, this altered expression pattern is likely to contribute to asthma pathology in children.

Advances in asthma, asthma-COPD overlap, and related biologics in 2018

Over the past year, numerous important advances in our understanding of multiple aspects of asthma, ranging from disease pathogenesis to epidemiology to therapeutics, have been reported. This review is a compilation of highlights from articles published largely in the Journal of Allergy and Clinical Immunology and supplemented by articles published elsewhere that have substantially advanced the fields of asthma, chronic obstructive pulmonary disease (COPD), and asthma-COPD overlap and biologic therapies for these disorders. The intention of this article is not to provide a comprehensive review but rather to focus on several areas that have developed quickly and/or received extensive attention from our readers.