Is IgE or eosinophils the key player in allergic asthma pathogenesis? Are we asking the right question?

Effect of omalizumab on lung function and eosinophil levels in adolescents with moderate-to-severe allergic asthma

BACKGROUND

Omalizumab improves clinical outcomes in patients with asthma. Several studies have shown lung function improvements with omalizumab; however, this has not been examined exclusively in adolescents.

OBJECTIVE

To assess the effect of omalizumab on lung function and eosinophil counts in adolescents with uncontrolled moderate-to-severe allergic asthma.

METHODS

In this post hoc analysis, data from adolescents aged 12 to 17 years from 8 randomized trials of omalizumab were pooled (studies 008, 009, and 011, and SOLAR, INNOVATE, ALTO, ETOPA, and EXTRA). Changes from baseline to end of study in forced expiratory volume in 1 second (FEV₁), percent predicted FEV₁ (ppFEV₁), forced vital capacity (FVC), and blood eosinophil counts were assessed by fitting an analysis of covariance model and calculating least squares mean (LSM) difference for omalizumab vs placebo.

RESULTS

A total of 340 adolescents were identified (omalizumab, n = 203 [59.7%]; placebo, n = 137 [40.3%]). Omalizumab increased all baseline lung function variables more than placebo by end of study: LSM treatment differences (95% confidence interval) were 3.0% (0.2%-5.7%; P = .035), 120.9 mL (30.6-211.2 mL; P = .009), and 101.5 mL (8.3-194.6 mL; P = .033) for ppFEV₁, absolute FEV₁, and FVC, respectively. The LSM difference demonstrated a greater reduction in eosinophil counts for omalizumab vs placebo: -85.9 cells/μL (-137.1 to -34.6 cells/μL; P = .001).

CONCLUSION

Omalizumab was associated with lung function improvements and circulating eosinophil counts reductions in adolescents with moderate-to-severe uncontrolled asthma. Findings emphasize the effect of omalizumab in young patients and the need to optimize treatment early in the disease course. https://clinicaltrials.gov/: NCT00314574, NCT00046748, NCT00401596.

Bronchoalveolar lavage fluid cytokine, cytology and IgE allergen in horses with equine asthma

The pathophysiology of equine asthma (EA) is still not fully described, but the involvement of an allergic reaction is strongly suspected. This theory has led to the use of allergen-specific immunoglobulin (Ig)E tests to support a diagnosis of asthma. The objective of this descriptive study was to evaluate the correlation between four subgroups of EA (mastocytic mild equine asthma [MEA], neutrophilic MEA, mixed MEA, and severe equine asthma [SEA]), allergen specific IgE (measured in both serum and BALF) and mRNA expression of selected genes in bronchoalveolar lavage fluid (BALF). Serum and BALF were collected from 64 horses with a history of lower airway problems with or without poor performance. Differential cell counts from BALF were used to assign horses to one of four groups (mastocytic MEA; neutrophilic MEA, mixed MEA, and SEA). The expression of messenger RNA (mRNA) coding for IL4, IL5, IL8, IL10, TGFB, TNFA, toll-like receptor (TLR)4, IL1RA, IL1B, matrix metalloproteinase 8 (MMP8), TLR9, chemokine ligand 5 (CCL5) and cluster of differentiation (CD)14 in BALF were measured using reverse transcriptase (RT) quantitative PCR (qPCR). Allergen-specific IgE was measured in serum and BALF using an allergen-specific IgE ELISA test with the screening panel: house mites, storage mites, mould and pollen. As expected, the BALF neutrophil differential count correlated with mRNA expression of MMP-8 (r = 0.611, p < 0.001), TLR-4 (r = 0.540, p < 0.001), IL-1RA (r = 0.490, p < 0.001), IL-1β (r = 0.463, p < 0.001) and IL-8 (r = 0.302, p = 0.015). Cytokine expression of IL-1β (p = 0.014), MMP8 (p = 0.028) and IL-1RA (p = 0.037) was significantly higher in the SEA group compared to the MEA subgroups. The BALF mast cell count was correlated with allergen-specific IgE for insects (r = 0.370, p = 0.002) and pollen (r = 0.313, p = 0.011). Eosinophils in BALF were correlated with BALF mRNA expression of IL-4 (r = 0.340, p = 0.006) together with a significant correlation between BALF eosinophils and allergen-specific IgE for mites (r = 0.930, p < 0.001) and pollen in BALF (r = 0.837, p < 0.001). No correlation was found between allergen-specific IgE in serum and BALF for any of the allergen in the screening panel. Based on these results from allergen-specific IgE in horses with EA is not found in systemic circulation, and only the mastocytic and mixed subgroups of horses with EA had allergen-specific IgE in BALF. Further studies are needed to clarify the relationships identified here.

Resolution of allergic asthma

Allergic asthma is an inflammatory disease of the airways characterized by recurrent episodes of wheezing and bronchoconstriction. Chronic inflammation may finally lead to structural damage followed by airway remodeling. Various studies in recent years contributed to unravel important aspects of the immunopathogenesis of asthma and adapted new pharmaceutical developments. Here, I consider some novel insights into the immunopathogenesis of asthma and the protective and pathogenic roles of some innate and adaptive immune cells as well as the function of soluble mediators such as cytokines. Particular attention will be given to new concepts on resolution of chronic airway inflammation for prevention of airway structural damage.

Immunologic mechanisms in asthma

Asthma is a chronic airway disease, which affects more than 300 million people. The pathogenesis of asthma exhibits marked heterogeneity with many phenotypes defining visible characteristics and endotypes defining molecular mechanisms. With the evolution of novel biological therapies, patients, who do not-respond to conventional asthma therapy require novel biologic medications, such as anti-IgE, anti-IL-5 and anti-IL4/IL13 to control asthma symptoms. It is increasingly important for physicians to understand immunopathology of asthma and to characterize asthma phenotypes. Asthma is associated with immune system activation, airway hyperresponsiveness (AHR), epithelial cell activation, mucus overproduction and airway remodeling. Both innate and adaptive immunity play roles in immunologic mechanisms of asthma. Type 2 asthma with eosinophilia is a common phenotype in asthma. It occurs with and without visible allergy. The type 2 endotype comprises; T helper type 2 (Th2) cells, type 2 innate lymphoid cells (ILC2), IgE-secreting B cells and eosinophils. Eosinophilic nonallergic asthma is ILC2 predominated, which produces IL-5 to recruit eosinophil into the mucosal airway. The second major subgroup of asthma is non-type 2 asthma, which contains heterogeneous group of endoypes and phenotypes, such as exercise-induced asthma, obesity induced asthma, etc. Neutrophilic asthma is not induced by allergens but can be induced by infections, cigarette smoke and pollution. IL-17 which is produced by Th17 cells and type 3 ILCs, can stimulate neutrophilic airway inflammation. Macrophages, dendritic cells and NKT cells are all capable of producing cytokines that are known to contribute in allergic and nonallergic asthma. Bronchial epithelial cell activation and release of cytokines, such as IL-33, IL-25 and TSLP play a major role in asthma. Especially, allergens or environmental exposure to toxic agents, such as pollutants, diesel exhaust, detergents may affect the epithelial barrier leading to asthma development. In this review, we focus on the immunologic mechanism of heterogenous asthma phenotypes.

Ang-(1-7)/ MAS1 receptor axis inhibits allergic airway inflammation via blockade of Src-mediated EGFR transactivation in a murine model of asthma

The angiotensin-(1–7) [Ang-(1–7)]/MAS1 receptor signaling axis is a key endogenous anti-inflammatory signaling pathway. However, the mechanisms by which its mediates the anti-inflammatory effects are not completely understood. Using an allergic murine model of asthma, we investigated whether Ang-1(1–7)/MAS1 receptor axis a): inhibits allergic inflammation via modulation of Src-dependent transactivation of the epidermal growth factor receptor (EGFR) and downstream signaling effectors such as ERK1/2, and b): directly inhibits neutrophil and/or eosinophil chemotaxis ex vivo. Ovalbumin (OVA)-induced allergic inflammation resulted in increased phosphorylation of Src kinase, EGFR, and ERK1/2. In addition, OVA challenge increased airway cellular influx, perivascular and peribronchial inflammation, fibrosis, goblet cell hyper/metaplasia and airway hyperresponsiveness (AHR). Treatment with Ang-(1–7) inhibited phosphorylation of Src kinase, EGFR, ERK1/2, the cellular and histopathological changes and AHR. Ang-(1–7) treatment also inhibited neutrophil and eosinophil chemotaxis ex vivo. These changes were reversed following pre-treatment with A779. These data show that the anti-inflammatory actions of Ang-(1–7)/ MAS1 receptor axis are mediated, at least in part, via inhibition of Src-dependent transactivation of EGFR and downstream signaling molecules such as ERK1/2. This study therefore shows that inhibition of the Src/EGRF/ERK1/2 dependent signaling pathway is one of the mechanisms by which the Ang-(1–7)/ MAS1 receptor axis mediates it anti-inflammatory effects in diseases such as asthma.

What have recent advances in therapy taught us about severe asthma disease mechanisms?

Introduction: Severe asthma still represents a worldwide challenge. The need for further treatment options has stimulated basic and pharmacological research to focus on the immune and inflammatory background of asthma. The new biologic drugs express the considerable advances in the field and besides providing a revolutionary treatment option for severe asthma, contribute themselves to better understand the pathophysiologic mechanisms they address, paving the way to new potential targets.Areas covered: A selective search on PubMed and Medline was performed, including the evidence on immunology of severe asthma published up to May 2019 by focusing on the immunological effects of biologic drugs underlying their clinical outcomes.Expert opinion: The recent pharmacological research in the field of biologics has represented an exceptional opportunity for exploring severe asthma mechanisms. However, some points deserve to be addressed by further investigation. Although in the absence of safety warnings so far, interfering with the immune system may raise some safety concerns, especially in the long-term use. Particularly when interacting with epithelial and innate immunity the selection of candidates probably deserves special caution. Also, whether biologics exert a true disease-modifying effect is not completely clear. As a direct practical implication, the optimal treatment duration is still controversial.

Safety, pharmacokinetics and pharmacodynamics of a novel anti-asthmatic drug, XC8, in healthy probands

INTRODUCTION

XC8 (histamine glutarimide) is a novel agent which targets eosinophilic migration and mast cell degranulation and has shown anti-asthmatic effects in animal studies.

OBJECTIVE

The objective of this placebo-controlled phase 1 study was to assess the safety of oral XC8 and to evaluate its pharmacokinetic and pharmacodynamic properties.

METHODS

32 healthy volunteers in three dose-escalation treatment groups (10 mg [n = 8], 50 mg [n = 8] and 200 mg [n = 16]) were randomized in a 3:1 ratio to XC8 or placebo respectively. The subjects received a single dose of the drug at Day 1 and then once-daily for 14 days (Days 8-21).

RESULTS

No severe adverse events occurred. The number of adverse events was similar in the treatment arms compared to placebo and all subjects completed the study as planned. No clinically significant changes occurred in hematologic and biochemical blood tests in subjects receiving XC8. The pharmacokinetic data showed similar dose and time dependent mean plasma XC8 concentrations after single (Day 1) and multiple (Day 21) dosing. The mean maximum concentrations were 114-1993 ng/mL after single and 115-2089 ng/mL after multiple dosing. The mean times to maximum concentration were 0.68-1.01 and 0.67-0.98 h, respectively. There was no evidence for accumulation of XC8 after multiple dosing.

CONCLUSION

XC8 was safe and well tolerated. A phase 2 study is being performed to further evaluate the potential role of XC8 in asthma treatment.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02882217.

Refractory asthma phenotyping based on immunoglobulin E levels and eosinophilic counts: A real life study

BACKGROUND

Asthma is an inflammatory heterogeneous disease with variable severity. The serum IgE level and Eosinophilic count have been used as biomarkers to define treatment strategies with biological agents in severe refractory asthma.

OBJECTIVE

The aim of this study is to determine the concurrence of high eosinophil count and elevated serum IgE levels in patients with severe refractory asthma.

METHODS

A retrospective cross-sectional real-life study was conducted on patients attending adult refractory asthma outpatient clinic between 2015 and 2018. Serum total IgE level and blood EOS count on matched dates with spirometry and Asthma Control Test (ACT) scores were collected. All data were obtained while patients were not on biological agents.

RESULTS

A total of 142 patients with severe refractory asthma were included. The mean age was 43 years, mean eosinophilic count 564 cells/μL and mean serum IgE levels of 520 IU/ml. There was a significant correlation between serum IgE level and eosinophilic count. Serum IgE and eosinophilic count were concurrently elevated in 110 patients (78%). The patients were further categorized into four subgroups. Group A: IgE 30-100 IU/mL and EOS 150-300 cells/μL (7.3%), Group B: IgE >100 IU/mL and EOS 150-300 cells/μL (19.1%), Group C: IgE 30-100 IU/mL and EOS >300 cells/μL (14.5%) and Group D: IgE >100 IU/mL, EOS >300 cells/μL (59.1%).

CONCLUSION

The majority of severe refractory asthma patients exhibits both elevated serum IgE level and eosinophilic counts.

Update in Pediatric Asthma: Selected Issues

Asthma is a complex condition that affects 14% of the world's children and the approach to management includes both pharmacologic as well as non-pharmacologic strategies including attention to complex socioeconomic status phenomena. After an historical consideration of asthma, allergic and immunologic aspects of asthma in children and adolescents are presented. Concepts of socioeconomic aspects of asthma are considered along with environmental features and complications of asthma disparities. Also reviewed are links of asthma with mental health disorders, sleep disturbances and other comorbidities. A stepwise approach to asthma management is discussed that includes pharmacologic and non-pharmacologic strategies in the pediatric population. The role of immunotherapy and use of various immunomodulators are considered as well.

Serum IL-1β can be a biomarker in children with severe persistent allergic rhinitis

Background

Allergic rhinitis (AR) is one of the most common diseases globally and usually persists throughout life. In the present study, we aimed to determine whether the expression of inflammatory biomarkers has a relationship with the severity of allergic rhinitis and with comorbid asthma or other allergic diseases in children.

Methods

For diagnosis of AR, the skin prick test was performed to measure the responses to 18 allergens. Blood levels of eosinophils and immunoglobulin E (IgE) were examined. We classified the patients into 2 groups based on the severity of the condition as Group 1 [intermittent AR (IAR) or mild persistent AR (PAR)] and Group 2 (moderate to severe PAR). To determine the expression of inflammatory biomarkers, in serum and several biomarkers (caspase-1, IL-1β, CCL-11, CCL-24 and IL-33) were measured in the serum using enzyme-linked immunosorbent assay (ELISA). Additionally, we analyzed the correlation between clinical variables and the expression of biomarkers (eosinophils count, IL-1β and CCL-24) and the severity of AR.

Results

We found that eosinophils count, IL-1β, a marker of activation of inflammasomes, and CCL-24 were significantly increased in the moderate to severe PAR group (p = 0.008, p = 0.003, p = 0.039). Additionally, the expressions of eosinophil count, IL-1β and CCL-24 were significantly higher in patients with active asthmatic symptoms than in those without these conditions. On univariate analysis, allergic rhinitis in sibling, paternal allergic rhinitis, high expression of eosinophils count, IL-1β and CCL-24, history of active asthma and atopy correlated with severity of AR. Multivariate analysis showed only paternal allergic rhinitis and high expression of IL-1β as significant risk factors of moderate to severe PAR with 6.4 fold and 4.7 fold-increase in risk, respectively (p = 0.011 and p = 0.030).

Conclusion

In conclusion, this study provides the first evidence that an excessive release of biologically active IL-1β may promote inflammation in severe PAR. It demonstrates that IL-1β can be a biomarker for active allergic diseases such as AR, asthma, and atopy. Moreover, this finding suggests that IL-1B should be investigated as a therapeutic target in severe PAR and other allergic diseases.

Multi-Faceted Notch in Allergic Airway Inflammation

Notch is an evolutionarily conserved signaling family which iteratively exerts pleiotropic functions in cell fate decisions and various physiological processes, not only during embryonic development but also throughout adult life. In the context of the respiratory system, Notch has been shown to regulate ciliated versus secretory lineage differentiation of epithelial progenitor cells and coordinate morphogenesis of the developing lung. Reminiscent of its role in development, the Notch signaling pathway also plays a role in repair of lung injuries by regulation of stem cell activity, cell differentiation, cell proliferation and apoptosis. In addition to functions in embryonic development, cell and tissue renewal and various physiological processes, including glucose and lipid metabolism, Notch signaling has been demonstrated to regulate differentiation of literally almost all T-cell subsets, and impact on elicitation of inflammatory response and its outcome. We have investigated the role of Notch in allergic airway inflammation in both acute and chronic settings. In this mini-review, we will summarize our own work and recent advances on the role of Notch signaling in allergic airway inflammation, and discuss potential applications of the Notch signaling family in therapy for allergic airway diseases.

A high blood eosinophil count may be a risk factor for incident asthma in population at risk

BACKGROUND

Eosinophilia is considered to be associated with allergic disease and may predict asthma exacerbation. Eosinophils contribute to the pathophysiology and pathogenesis of asthma. However, studies on high blood eosinophil counts (BECs) and incident asthma remain scarce.

OBJECTIVE

To examine whether high BECs are positively associated with incident asthma in adults.

METHODS

Our study included 57975 participants aged from 20 to 79 years from the Shandong multi-center health check-up longitudinal study for Health Management. All patients with determined baseline BECs were ≥20 years old and free from asthma. We defined incident asthma as self-reported new-onset asthma occurring during the 10-year follow-up period. Multivariate modeling employed Poisson regression and Cox proportional hazards models to verify the association between BEC and incident asthma by adjusting demographics and some relevant comorbidities (rhinitis, nasal polyps, pneumonia, bronchitis, and chronic obstructive pulmonary disease).

RESULTS

A BEC ≥110 cells/μL was a risk factor for incident asthma (adjusted IRR = 1.62, 95% CI: 1.05-2.50, P = .028) in the Poisson regression. In the Cox proportional hazards model, the BEC cutoff point for incident asthma was also determined to be 110 cells/μL (HR = 1.59, 95% CI: 1.01-2.51, P = .045).

CONCLUSION

A high BEC is a risk factor for incident asthma, especially when the BEC exceeds 110 cells/μL. This suggests that adults with high BECs are more likely to develop asthma.

Membrane-bound IgE on B cells is increased during Clonorchis sinensis infection

A high level of serum IgE is a hallmark of helminthic disease. Secretory IgE can bind FcεRI or FcεRII/CD23. The combination of IgE and FcεRI, a high-affinity interaction, has long received attention and is believed to facilitate helminth control, while the properties of CD23-bound IgE have long been unexplored. Here, we established a Clonorchis sinensis (C. sinensis) infection model with different mouse strains and investigated membrane-bound IgE on B cells during infection. We show that after infection, the increase in CD23 expression on B cells was obvious, even in relatively resistant C57BL/6 mice, as well as in susceptible BALB/c and FVB mice. Although the serum IgE amount was lower in C57BL/6 mice than in BALB/c and FVB mice, the level of IgE binding to peripheral B cells was also elevated. Additionally, the IgE on B cells was soon undetectable in vitro due to dissociable binding. The results of the present study demonstrate the dramatic increase in CD23-bound IgE on B cells after C. sinensis infection. The significance of CD23-bound IgE in Ag transport and presentation has gained consideration in allergy development for its potential ability to promote the Th2 response. Therefore, even though the association of IgE and CD23 is not as substantial as that of IgE and FcεRI, membrane-bound IgE on B cells may be worth further study regarding clonorchiasis and other parasitic infections.

Integration of Metabolomics and Transcriptomics Reveals the Therapeutic Mechanism Underlying Paeoniflorin for the Treatment of Allergic Asthma

Objectives: Asthma is a chronic airway inflammatory disease, which is characterized by airway remodeling, hyperreactivity and shortness of breath. Paeoniflorin is one of the major active ingredients in Chinese peony, which exerts anti-inflammatory and immune-regulatory effects in multiple diseases. However, it remains unclear whether paeoniflorin treatment can suppress allergic asthma.

Methods: In this study, we evaluated the effect of paeoniflorin on lung function and airway inflammation in asthmatic mice. These asthmatic Balb/c mice were first sensitized and constructed through ovalbumin (OVA) motivation. Subsequently, we determined the mechanism of action of paeoniflorin in treating allergic asthma through integrated transcriptomic and metabolomic data sets.

Results: Our results demonstrated that many genes and metabolites were regulated in the paeoniflorin-treated mice. Moreover, the potential target proteins of paeoniflorin played important roles in fatty acid metabolism, inflammatory response, oxidative stress and local adhesion.

Conclusion: Paeoniflorin has a beneficial effect on asthma, which may be achieved through regulating fatty acid metabolism, inflammatory response and the adhesion pathway at system level.

Synthesis and biological evaluation of Ginsenoside Compound K analogues as a novel class of anti-asthmatic agents

Ginsenoside Compound K (CK) showed potent activity against IgE for the treatment of asthma. A series of CK analogues were then synthesized by straightforward procedures. The in vivo anti-IgE activity evaluations using the OVA-induced asthmatic mouse model revealed preliminary SARs of the CK analogues, which showed that the sugar type, modifications on A-ring and the C20 side chain of CK all affected much on the activities. Primary SARs optimization led to the discovery of compounds T1, T2, T3, T8 and T12, which displayed superior or comparable anti-asthmatic effects (IgE value = 1237.11 ± 106.28, 975.82 ± 160.32, 1136.96 ± 121.85, 1191.08 ± 107.59 and 1258.27 ± 148.70 ng/mL, respectively) in comparison with CK (1501.85 ± 184.66 ng/mL). These potent compounds could serve as leads for further development.