Etiology of asthma exacerbations

Asthma exacerbations and airway redox imbalance under type 2 inflammatory conditions

Asthma is a chronic inflammatory airway disease characterized by bronchial hyperresponsiveness and reversibility. Despite considerable advances in asthma treatment based on our understanding of its pathophysiology, asthma exacerbations remain challenging. To reduce asthma exacerbations, it is essential to identify triggers, patients' risk factors, and underlying mechanisms. While exposure to viruses and environmental stimuli are known common triggers for asthma exacerbations, the key factors involved in asthma exacerbations have been identified as type 2 inflammation. Type 2 inflammatory biomarkers have been demonstrated to be useful in predicting individuals at risk of exacerbations. Furthermore, recent clinical trials of targeted biological therapy, which blocks the type 2 pathway, have supported the critical role of type 2 inflammation in asthma exacerbations. Although the specific mechanisms linking type 2 inflammation to asthma exacerbations have not yet been fully elucidated, increasing evidence shows that reduction/oxidation (redox) imbalance likely plays an important role in this association. Under type 2 inflammatory conditions, human airway epithelial cells activate 15-lipoxygenase-1 in complex with phosphatidylethanolamine binding protein-1, leading to the generation of electrophilic hydroperoxyl-phospholipids. When the accumulation of reactive lipid peroxidation surpasses a specific glutathione-dependent activity, these electrophilic compounds are not neutralized, leading to programmed cell death, ferroptosis. Reduced glutathione levels, caused by type 2 inflammation, may impair its ability to neutralize reactive lipid peroxidation. The accumulation of lipid peroxidation with intracellular redox imbalance may contribute to asthma exacerbations in individuals with type 2 inflammation. Inhibiting the ferroptotic pathway holds promise as a therapeutic strategy to alleviate asthma exacerbations.

Natural killer cells in the lung: potential role in asthma and virus-induced exacerbation?

Asthma is a chronic inflammatory airway disorder whose pathophysiological and immunological mechanisms are not completely understood. Asthma exacerbations are mostly driven by respiratory viral infections and characterised by worsening of symptoms. Despite current therapies, asthma exacerbations can still be life-threatening. Natural killer (NK) cells are innate lymphoid cells well known for their antiviral activity and are present in the lung as circulating and resident cells. However, their functions in asthma and its exacerbations are still unclear. In this review, we will address NK cell activation and functions, which are particularly relevant for asthma and virus-induced asthma exacerbations. Then, the role of NK cells in the lungs at homeostasis in healthy individuals will be described, as well as their functions during pulmonary viral infections, with an emphasis on those associated with asthma exacerbations. Finally, we will discuss the involvement of NK cells in asthma and virus-induced exacerbations and examine the effect of asthma treatments on NK cells.

Innate Immunity, Epithelial Plasticity, and Remodeling in Asthma

Innate immune responses (IIR) of the epithelium play a critical role in the initiation and progression of asthma. The core of the IIR is an intracellular signaling pathway activated by pattern recognition receptors (PRRs) to limit the spread of infectious organisms. This chapter will focus on the epithelium as the major innate sentinel cell and its role in acute exacerbations (AEs). Although the pathways of how the IIR activates the NFκB transcription factor, triggering cytokine secretion, dendritic cell activation, and Th2 polarization are well-described, recent exciting work has developed mechanistic insights into how chronic activation of the IIR is linked to mucosal adaptive responses. These adaptations include changes in cell state, now called epithelial-mesenchymal plasticity (EMP). EMP is a coordinated, genomic response to airway injury disrupting epithelial barrier function, expanding the basal lamina, and producing airway remodeling. EMP is driven by activation of the unfolded protein response (UPR), a transcriptional response producing metabolic shunting of glucose through the hexosamine biosynthetic pathway (HBP) to protein N-glycosylation. NFκB signaling and UPR activation pathways potentiate each other in remodeling the basement membrane. Understanding of injury-repair process of epithelium provides new therapeutic targets for precision approaches to the treatment of asthma exacerbations and their sequelae.

Effects of carbon black nanoparticles and high humidity on the lung metabolome in Balb/c mice with established allergic asthma

In respiratory diseases, the induction of allergic asthma has gradually aroused public concerns. Co-exposures of environmental risk factors such as nanoparticles and high humidity could play important roles in the development of allergic asthma. However, the relevant researches are still lacking and the involved mechanisms, especially metabolic changes, remain unclear. We took the lead in studying the combined induction effect and underlying mechanisms of carbon black nanoparticles (CB NPs) and high humidity on allergic asthma. In this work, murine models of allergic asthma were established with ovalbumin under the single and combined exposures of 15 μg/kg CB NPs and 90% relative humidity. The two risk factors, particularly their co-exposure, exhibited adjuvant effect on airway hyperresponsiveness, remodeling, and inflammation in Balb/c mice. Untargeted metabolomics identified the potential biomarkers in lung for asthma occurrence and for asthma exacerbation caused by CB NPs and high humidity. The significantly dysregulated metabolic pathways in asthmatic mice were proposed, and the disturbed metabolic pathways under the exposures of CB NPs and/or high humidity were mainly implicated in asthma symptoms. This work sheds light on the understanding for health risks of NP pollutions and high environmental humidity and contributes to useful biomarker identification and asthma control.

Safety of Live Attenuated Influenza Vaccine in Children With Asthma

BACKGROUND AND OBJECTIVES

Asthma is considered a precaution for use of quadrivalent live attenuated influenza vaccine (LAIV4) in persons aged ≥5 years because of concerns for wheezing events. We evaluated the safety of LAIV4 in children with asthma, comparing the proportion of children with asthma exacerbations after LAIV4 or quadrivalent inactivated influenza vaccine (IIV4).

METHODS

We enrolled 151 children with asthma, aged 5 to 17 years, during 2 influenza seasons. Participants were randomly assigned 1:1 to receive IIV4 or LAIV4 and monitored for asthma symptoms, exacerbations, changes in peak expiratory flow rate (PEFR), and changes in the asthma control test for 42 days after vaccination.

RESULTS

We included 142 participants in the per-protocol analysis. Within 42 days postvaccination, 18 of 142 (13%) experienced an asthma exacerbation: 8 of 74 (11%) in the LAIV4 group versus 10 of 68 (15%) in the IIV4 group (LAIV4-IIV4 = -0.0390 [90% confidence interval -0.1453 to 0.0674]), meeting the bounds for noninferiority. When adjusted for asthma severity, LAIV4 remained noninferior to IIV4. There were no significant differences in the frequency of asthma symptoms, change in PEFR, or childhood asthma control test/asthma control test scores in the 14 days postvaccination between LAIV4 and IIV4 recipients. Vaccine reactogenicity was similar between groups, although sore throat (P = .051) and myalgia (P <.001) were more common in the IIV4 group.

CONCLUSIONS

LAIV4 was not associated with increased frequency of asthma exacerbations, an increase in asthma-related symptoms, or a decrease in PEFR compared with IIV4 among children aged 5 to 17 years with asthma.

Human Rhinovirus Infection of the Respiratory Tract Affects Sphingolipid Synthesis

The 17q21 asthma susceptibility locus includes asthma risk alleles associated with decreased sphingolipid synthesis, likely resulting from increased expression of ORMDL3. ORMDL3 inhibits serine-palmitoyl transferase (SPT), the rate limiting enzyme of de novo sphingolipid synthesis. There is evidence that decreased sphingolipid synthesis is critical to asthma pathogenesis. Children with asthma and 17q21 asthma risk alleles display decreased sphingolipid synthesis in blood cells. Reduced SPT activity results in airway hyperreactivity, a hallmark feature of asthma. 17q21 asthma risk alleles are also linked to childhood infections with human rhinovirus (RV). This study evaluates the interaction of RV with the de novo sphingolipid synthesis pathway, and the alterative effects of concurrent SPT inhibition in SPT-deficient mice and human airway epithelial cells. In mice, RV infection shifted lung sphingolipid synthesis gene expression to a pattern that resembles genetic SPT deficiency, including decreased expression of Sptssa, a small SPT subunit. This pattern was pronounced in lung EpCAM+ epithelial cells and reproduced in human bronchial epithelial cells. RV did not affect Sptssa expression in lung CD45+ immune cells. RV increased sphingolipids unique to the de novo synthesis pathway in mouse lung and human airway epithelial cells. Interestingly, these de novo sphingolipid species were reduced in the blood of RV infected, wild-type mice. RV exacerbated SPT-deficiency-associated airway hyperreactivity. Airway inflammation was similar in RV-infected wild-type and SPT deficient mice. This study reveals the effects of RV infection on the de novo sphingolipid synthesis pathway, elucidating a potential mechanistic link between 17q21 asthma risk alleles and rhinoviral infection.

TLR7 Agonist Suppresses ILC2-mediated Inflammation via IL-27-producing Interstitial Macrophages

Group 2 innate lymphoid cells (ILC2s) play an important role in the pathophysiology of asthma via the robust production of type 2 cytokines. Recent studies have demonstrated that Toll-like receptor 7 (TLR7) signaling skews toward a type 1 inflammatory response in asthma, which may lead to the development of novel treatment strategies. However, the effect of TLR7 signaling on ILC2-dependent non-allergic eosinophilic inflammation remains unclear. In this study, we investigated the effects of R848, a TLR7 agonist, in a mouse model of IL-33-induced eosinophilic airway inflammation. Intranasal administration of R848 decreased infiltration of airway eosinophils and ILC2s, mucus production in epithelial cells, and type 2 cytokine production. Flow cytometric analysis identified an increased number of interstitial macrophages (IMs) expressing a high level of TLR7 in the lung upon IL-33 stimulation. IL-33-induced IMs also expressed high levels of M2-type genes and chemokines (CCL17 and CCL24). However, R848 stimulation modified these gene expressions and elicited the production of interleukin 27 (IL-27). Co-culture experiments revealed that IL-33-induced IMs directly suppressed ILC2 activation in response to R848. In addition, the inhibitory effects of R848 on ILC2-induced type 2 inflammation were defective in WSX-1-deficient mice lacking the IL-27 receptor. Taken together, these findings indicate that R848 stimulates IL-33-induced IMs to suppress ILC2-mediated type 2 airway inflammation via IL-27. These findings highlight the therapeutic potential of TLR7 agonists and/or IL-27 cascades in non-allergic asthma.

Can eosinophilia and neutrophil-lymphocyte ratio predict hospitalization in asthma exacerbation?

OBJECTIVE

Asthma is one of the most common diseases amongst children. Blood eosinophil count and neutrophil-lymphocyte ratio (NLR) are known as markers for phenotyping asthma. This study was performed to investigate blood eosinophil count and NLR as predictors of hospitalization in pediatric asthma exacerbations.

DATA SOURCES AND STUDY SELECTIONS

In this cross-sectional study, children admitted to hospital ward for more severe asthma exacerbation were compared with non-hospitalized children with moderate to severe asthma exacerbation whose asthma exacerbation was managed in emergency department or outpatient clinic. We investigated patients' characteristic and factors associated with hospitalization.

RESULTS

A total of 211 children with moderate to severe asthma exacerbation (mean age [Formula: see text] years old) were enrolled in the study including 91 hospitalized patients and 120 non-hospitalized patients. For the prediction of hospitalization, an ROC Curve analysis was performed and revealed a cut-off of 298 cells/µL and 2.52 of blood eosinophil count and NLR, respectively. In multivariate analysis, not using an asthma action plan (OR 2.22, 95% CI 1.09-4.49; P = 0.027), a blood eosinophil count [Formula: see text] 298 (OR 8.79, 95% CI 4.44-17.4; P < 0.001) and an NLR [Formula: see text] 2.52 (OR 2.13, 95% CI 1.09-4.14; P = 0.027) were associated with hospitalization.

CONCLUSION

Blood eosinophil count and NLR were found to be higher in hospitalized children with more severe asthma exacerbation compared to non-hospitalized patients. These markers can be indicators for asthma exacerbation severity.

Single-cell transcriptomic analysis of allergen-specific T cells in allergy and asthma

CD4⁺ T helper (T_H) cells and regulatory T (T_reg) cells that respond to common allergens play an important role in driving and dampening airway inflammation in patients with asthma. Until recently, direct, unbiased molecular analysis of allergen-reactive T_H and T_reg cells has not been possible. To better understand the diversity of these T cell subsets in allergy and asthma, we analyzed the single-cell transcriptome of ~50,000 house dust mite (HDM) allergen-reactive T_H cells and T_reg cells from asthmatics with HDM allergy and from three control groups: asthmatics without HDM allergy and nonasthmatics with and without HDM allergy. Our analyses show that HDM allergen-reactive T_H and T_reg cells are highly heterogeneous and certain subsets are quantitatively and qualitatively different in individuals with HDM-reactive asthma. The number of interleukin-9 (IL-9)-expressing HDM-reactive T_H cells is greater in asthmatics with HDM allergy compared with nonasthmatics with HDM allergy, and this IL-9-expressing T_H subset displays enhanced pathogenic properties. More HDM-reactive T_H and T_reg cells expressing the interferon response signature (T_HIFNR and T_regIFNR) are present in asthmatics without HDM allergy compared with those with HDM allergy. In cells from these subsets (T_HIFNR and T_regIFNR), expression of TNFSF10 was enriched; its product, tumor necrosis factor-related apoptosis-inducing ligand, dampens activation of T_H cells. These findings suggest that the T_HIFNR and T_regIFNR subsets may dampen allergic responses, which may help explain why only some people develop T_H2 responses to nearly ubiquitous allergens.

Bronchoconstriction: a potential missing link in airway remodelling

In asthma, progressive structural changes of the airway wall are collectively termed airway remodelling. Despite its deleterious effect on lung function, airway remodelling is incompletely understood. As one of the important causes leading to airway remodelling, here we discuss the significance of mechanical forces that are produced in the narrowed airway during asthma exacerbation, as a driving force of airway remodelling. We cover in vitro, ex vivo and in vivo work in this field, and discuss up-to-date literature supporting the idea that bronchoconstriction may be the missing link in a comprehensive understanding of airway remodelling in asthma.

Interleukin 4 gene polymorphism (-589C/T) and the risk of asthma: a meta-analysis and met-regression based on 55 studies

BACKGROUND

Numerous investigations have previously evaluated the association of interleukin (IL) 4 gene polymorphisms and the risk of asthma, conferring inconsistent results. To resolve the incongruent outcomes yielded from different single studies, we conducted the most up-to-date meta-analysis of IL4 gene -589C/T (rs2243250) polymorphism and susceptibility to asthma.

METHODS

A systematic literature search was performed in ISI web of science, Scopus, Medline/PubMed databases prior to September 2020, and the pooled odds ratio (OR) and their corresponding 95% CI were calculated to determine the association strength.

RESULTS

Literature search led to retrieving of 49 publications (55 case-control studies) containing 9572 cases and 9881 controls. It was revealed that IL4 gene -589C/T polymorphism increased the risk of asthma across all genetic models, including dominant model (OR = 1.22), recessive model (OR = 1.17), allelic model (OR = 1.21), and TT vs. CC model (OR = 1.34), but not the CT vs. TT model. The subgroup analysis by age indicated that IL4 gene -589C/T polymorphism was significantly associated with asthma risk in both pediatrics and adults. Additionally, the subgroup analysis by ethnicity revealed significant association in Asian, American, and Europeans. Finally, subgroup analysis by East Asian and non-East Asian populations indicated significant associations.

CONCLUSIONS

The current meta-analysis revealed that IL4 gene -589C/T polymorphism was a susceptibility risk in both pediatrics and adults in the whole and different ethnic groups.

SiO2 prompts host defense against Acinetobacter baumannii infection by mTORC1 activation

Host-pathogen interactions in the setting of chronic pulmonary inflammation remain unclear, and the occurrence of pneumonia is increased in patients with chronic obstructive pulmonary disease who use immunosuppressive drugs. We performed Acinetobacter baumannii infection in mice with chronic pulmonary inflammation after intranasal administration of SiO₂ and found SiO₂ treatment increased host defense against A. baumannii infection. Innate immune responses initiated by NF-κB, type 1 interferon, NLRP3 and AIM2 inflammasomes were dispensable for SiO₂-mediated host defense. SiO₂ treatment activated the mTORC1 signaling, and mTORC1 was crucial for host defense against A. baumannii infection. Our study highlights the protective role of mTORC1 signaling in host defense against bacterial infection, offers novel insights into understanding the mechanisms of immunosuppressive drug-related pneumonia, and provides potential host-directed therapeutics to treat bacterial infections.

CEACAM3 decreases asthma exacerbations and modulates respiratory syncytial virus latent infection in children

BACKGROUND

Respiratory syncytial virus (RSV) is associated with childhood asthma. Nevertheless, not all children exposed to RSV develop asthma symptoms, possibly because genes modulate the effects of RSV on asthma exacerbations.

OBJECTIVE

The purpose of this study was to identify genes that modulate the effect of RSV latent infection on asthma exacerbations.

METHODS

We performed a meta-analysis to investigate differentially expressed genes (DEGs) of RSV infection from Gene Expression Omnibus datasets. Expression quantitative trait loci (eQTL) methods were applied to select single nucleotide polymorphisms (SNPs) that were associated with DEGs. Gene-based analysis was used to identify SNPs that were significantly associated with asthma exacerbations in the Taiwanese Consortium of Childhood Asthma Study (TCCAS), and validation was attempted in an independent cohort, the Childhood Asthma Management Program (CAMP). Gene-RSV interaction analyses were performed to investigate the association between the interaction of SNPs and RSV latent infection on asthma exacerbations.

RESULTS

A total of 352 significant DEGs were found by meta-analysis of RSV-related genes. We used 38 123 SNPs related to DEGs to investigate the genetic main effects on asthma exacerbations. We found that eight RSV-related genes (GADD45A, GYPB, MS4A3, NFE2, RNASE3, EPB41L3, CEACAM6 and CEACAM3) were significantly associated with asthma exacerbations in TCCAS and also validated in CAMP. In TCCAS, rs7251960 (CEACAM3) significantly modulated the effect of RSV latent infection on asthma exacerbations (false-discovery rate <0.05). The rs7251960 variant was associated with CEACAM3 mRNA expression in lung tissue (p for trend=1.2×10^-7). CEACAM3 mRNA was reduced in nasal mucosa from subjects with asthma exacerbations in two independent datasets.

CONCLUSIONS

rs7251960 is an eQTL for CEACAM3, and CEACAM3 mRNA expression is reduced in subjects experiencing asthma exacerbations. CEACAM3 may be a modulator of RSV latent infection on asthma exacerbations.

Aberrant anti-viral response of natural killer cells in severe asthma

Rhinovirus infections are the main cause of asthma exacerbations. As natural killer (NK) cells are important actors of the antiviral innate response, we aimed at evaluating the functions of NK cells from severe asthma patients in response to rhinovirus-like molecules or rhinoviruses.Peripheral blood mononuclear cells from patients with severe asthma and healthy donors were stimulated with pathogen-like molecules or with the rhinoviruses (RV)-A9 and RV-2. NK cell activation, degranulation and interferon (IFN)-γ expression were analysed.NK cells from severe asthma patients were less cytotoxic than those from healthy donors in response to toll-like receptor (TLR)3, TLR7/8 or RV-A9 but not in response to RV-2 stimulation. Furthermore, when cultured with interleukin (IL)-12+IL-15, cytokines which are produced during viral infections, NK cells from patients with severe asthma were less cytotoxic and expressed less IFN-γ than NK cells from healthy donors. NK cells from severe asthmatics exhibited an exhausted phenotype, with an increased expression of the checkpoint molecule Tim-3.Together, our findings indicate that the activation of NK cells from patients with severe asthma may be insufficient during some but not all respiratory infections. The exhausted phenotype may participate in NK cell impairment and aggravation of viral-induced asthma exacerbation in these patients.

Lung-on-a-chip: the future of respiratory disease models and pharmacological studies

Recently, organ-on-a-chip models, which are microfluidic devices that mimic the cellular architecture and physiological environment of an organ, have been developed and extensively investigated. The chips can be tailored to accommodate the disease conditions pertaining to many organs; and in the case of this review, the lung. Lung-on-a-chip models result in a more accurate reflection compared to conventional in vitro models. Pharmaceutical drug testing methods traditionally use animal models in order to evaluate pharmacological and toxicological responses to a new agent. However, these responses do not directly reflect human physiological responses. In this review, current and future applications of the lung-on-a-chip in the respiratory system will be discussed. Furthermore, the limitations of current conventional in vitro models used for respiratory disease modeling and drug development will be addressed. Highlights of additional translational aspects of the lung-on-a-chip will be discussed in order to demonstrate the importance of this subject for medical research.

Respiratory Health Effects of Exposure to Ambient Particulate Matter and Bioaerosols

Researchers have been studying the respiratory health effects of ambient air pollution for more than 70 years. While air pollution as a whole can include gaseous, solid, and liquid constituents, this article focuses only on the solid and liquid fractions, termed particulate matter (PM). Although PM may contain anthropogenic, geogenic, and/or biogenic fractions, in this article, particles that originate from microbial, fungal, animal, or plant sources are distinguished from PM as bioaerosols. Many advances have been made toward understanding which particle and exposure characteristics most influence deposition and clearance processes in the respiratory tract. These characteristics include particle size, shape, charge, and composition as well as the exposure concentration and dose rate. Exposure to particles has been directly associated with the exacerbation and, under certain circumstances, onset of respiratory disease. The circumstances of exposure leading to disease are dependent on stressors such as human activity level and changing particle composition in the environment. Historically, researchers assumed that bioaerosols were too large to be inhaled into the deep lung, and thus, not applicable for study in conjunction with PM2.5 (the 2.5-μm and below size fraction that can reach the deep lung); however, this concept is beginning to be challenged. While there is extensive research on the health effects of PM and bioaerosols independent of each other, only limited work has been performed on their coexposure. Studying these two particle types as dual stressors to the respiratory system may aid in more thoroughly understanding the etiology of respiratory injury and disease. © 2020 American Physiological Society. Compr Physiol 10:1-20, 2020.

Procalcitonin Levels in Critically Ill Children With Status Asthmaticus

BACKGROUND

Children with status asthmaticus (SA) often present with fever and are evaluated with chest radiographs (CXRs). In the absence of a confirmatory test for bacterial infection, antibiotics are started whenever there are radiological infiltrates or if there is a suspicion of pneumonia. We undertook this study to determine if serum procalcitonin (PCT) levels at admission are altered in critically ill children with SA. We also sought to determine if serum PCT levels are elevated in children with radiological infiltrates or in children who were treated with antibiotics.

METHODS

This is a prospective single-center observational study evaluating serum PCT levels in critically ill children with SA. Study subjects included children 1 to 21 years old, admitted to a pediatric intensive care unit (PICU) with SA between March 2012 and April 2013. For the purposes of this study, patients whose CXRs were read by the radiologist as probable bacterial pneumonia was defined as having "radiological bacterial pneumonia," whereas patients who received antibiotics by the treating physician were defined as having "clinician-diagnosed pneumonia."

RESULTS

Sixty-one patients with a median age of 7.3 years (interquartile range, 4-10 years) were included in the study. Fifty-one percent were male. Average Pediatric Risk of Mortality III score was 2.7 (SD, 2.9). Three patients (5%) were determined to have radiological bacterial pneumonia, whereas 52 (85%) did not. Six patients (10%) were indeterminate. The mean PCT level for all patients was 0.65 (SD, 1.54) ng/mL, whereas the median PCT level was 0.3 ng/mL. There was no significant difference in the mean PCT levels between the patients with and without clinician-diagnosed pneumonia (0.33 [SD, 0.36] vs 0.69 [SD, 1.67], P = 0.44). Using a PCT cutoff level of 0.5 ng/mL, a significant association was found with the presence of fever (P = 0.004), but no significant association was found with the presence of CXR infiltrates, radiological bacterial pneumonia, hospital length of stay, PICU length of stay, Pediatric Risk of Mortality III scores, or receipt of antibiotics.

CONCLUSIONS

Serum PCT level was not elevated to greater than 0.5 ng/mL in 75% of this cohort of critically ill children with SA admitted to PICU. Presence of CXR infiltrates was not associated with higher PCT levels. Large clinical trials are needed to study the diagnostic and predictive role of PCT in this patient population.

Eosinophils and Respiratory Viruses

Eosinophils have been mainly associated with parasitic infection and pathologies such as asthma. Some patients with asthma present a high number of eosinophils in their airways. Since respiratory viruses are associated with asthma exacerbations, several studies have evaluated the role of eosinophils against respiratory viruses. Eosinophils contain and produce molecules with antiviral activity, including RNases and reactive nitrogen species. They can also participate in adaptive immunity, serving as antigen-presenting cells. Eosinophil antiviral response has been demonstrated against some respiratory viruses in vitro and in vivo, including respiratory syncytial virus and influenza. Given the implication of respiratory viruses in asthma, the eosinophil antiviral role might be an important factor to consider in this pathology.

Asthma: An Undermined State of Immunodeficiency

Asthma is a heterogeneous chronic respiratory disease characterized by an increased burden of infections. Respiratory tract infections associated with an increased risk for asthma especially when occurring in the first months of life, also represent the most common cause of asthma exacerbations. The association between asthma and the increased frequency of infections and microbiota dysbiosis might be explained by a common mechanism, such as an underlying immune system defect. Apart from the well-established association between primary immunodeficiencies and asthma, several alterations in the immune response following infection have also been observed in asthmatic patients. An impairment in lung epithelial barrier integrity exists and is associated with both an increased susceptibility to infections and the development of asthma. Asthmatic patients are also found to have a deficient interferon (IFN) response upon infection. Additionally, defects in Toll-like receptor (TLR) signaling are observed in asthma and are correlated with both recurrent infections and asthma development. In this review, we summarize the common pathophysiological background of asthma and infections, highlighting the importance of an underlying immune system defect that predispose individuals to recurrent infections and asthma.

The TH2-polarizing function of atopic interleukin 17 receptor B-positive dendritic cells up-regulated by lipopolysaccharide

BACKGROUND

Recent studies suggest that epithelial cell (EC)-derived cytokines contribute to allergic airway disease exacerbation.

OBJECTIVE

To confirm our hypothesis that atopic dendritic cells (DCs) are activated to up-regulate the receptors of cytokines that mainly derived from ECs and enhance T_H2 responses.

METHODS

The expressions of interleukin 17 receptor B (IL-17RB) (IL-25 receptor), membrane-bound ST2 (IL-33 receptor), thymic stromal lymphopoietin receptor (TSLPR), granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR), and several functional markers on CD1c⁺ monocyte-derived DCs (mo-DCs) were detected by flow cytometry. Lipopolysaccharide (LPS)-activated mo-DCs were cocultured with autologous CD4⁺ T cells, and cytokine production by these T cells was determined by intracellular flow cytometry.

RESULTS

LPS activated both nonatopic and atopic mo-DCs to express a higher level of GM-CSFR but only activated atopic mo-DCs to express increased IL-17RB, which was subsequently activated by IL-25 involved with signal transducer and activator of transcription 5 phosphorylation. In addition, LPS increased the expression of the OX40 ligand (OX40L) but decreased inducible costimulator ligand on atopic CD86⁺ mo-DCs. More importantly, IL-25 further up-regulated OX40L on atopic CD86⁺ mo-DCs. After coculturing with LPS-activated mo-DCs from atopic individuals, CD4⁺ T cells had enhanced inflammatory responses by increased production of IL-4, IL-5, IL-13, and interferon γ (IFN-γ). In contrast, further addition of IL-25 led CD4⁺ T cells to produce higher level of IL-4 but lower level of IFN-γ.

CONCLUSION

Atopic IL-17RB⁺ DCs can be up-regulated by LPS and promote a T_H2-type response, implying that the IL-25/IL-17RB pathway may represent a potential molecular mechanism underlying the regulation of ECs on DCs in allergic airway disease.

Leveraging gene-environment interactions and endotypes for asthma gene discovery

Asthma is a heterogeneous clinical syndrome that includes subtypes of disease with different underlying causes and disease mechanisms. Asthma is caused by a complex interaction between genes and environmental exposures; early-life exposures in particular play an important role. Asthma is also heritable, and a number of susceptibility variants have been discovered in genome-wide association studies, although the known risk alleles explain only a small proportion of the heritability. In this review, we present evidence supporting the hypothesis that focusing on more specific asthma phenotypes, such as childhood asthma with severe exacerbations, and on relevant exposures that are involved in gene-environment interactions (GEIs), such as rhinovirus infections, will improve detection of asthma genes and our understanding of the underlying mechanisms. We will discuss the challenges of considering GEIs and the advantages of studying responses to asthma-associated exposures in clinical birth cohorts, as well as in cell models of GEIs, to dissect the context-specific nature of genotypic risks, to prioritize variants in genome-wide association studies, and to identify pathways involved in pathogenesis in subgroups of patients. We propose that such approaches, in spite of their many challenges, present great opportunities for better understanding of asthma pathogenesis and heterogeneity and, ultimately, for improving prevention and treatment of disease.

Inhaled lead affects lung pathology and inflammation in sensitized and control guinea pigs

The association between lead exposure and respiratory diseases including asthma is controversial. Some studies indicate that exposure to environmental lead pollution may cause asthma; however, there is not sufficient data in this regard. The effect of lead on lung pathological findings and serum inflammatory mediators in sensitized and non-sensitized guinea pigs exposed to inhaled lead was examined. Eleven animal groups including control, sensitized, three groups of non sensitized animals, three groups during sensitization, and three groups after sensitization exposed to aerosol of three lead concentrations (n = 6 for each group) were studied. Serum inflammatory mediators levels and lung pathological changes were evaluated. All pathological changes and serum ET-1, EPO, NO levels were significantly higher in the sensitized and non sensitized animals exposed to lead than control group (p < 0.05 to p < 0.001). There was no significant difference between non sensitized groups exposed to high lead concentration and sensitized group. Serum inflammatory mediators levels and pathological findings in sensitized groups exposed to lead both during and after sensitization were significantly higher than sensitized non exposed group (p < 0.05 to p < 0.001). The data of exposed animals to high lead concentration were significantly higher than those of medium and low concentrations; those of medium concentration were also higher than low concentration (p < 0.05 to p < 0.001). In summary, the present study indicates that exposure to inhaled lead is able to induce respiratory changes similar to asthma. In addition, the results indicated that exposure to environmental lead is able to aggravate asthma severity both during development of asthma or after its manifestation.

Differential TLR-induced cytokine production by human mast cells is amplified by FcɛRI triggering

BACKGROUND

Mast cells are mainly present in strategic locations, where they may have a role in defence against parasites and bacteria. These pathogens can be recognized by mast cells via Toll-like receptors (TLR). Allergic symptoms are often increased in the presence of pathogens at the site of allergen exposure, but it is unknown which cytokines can mediate such an effect.

OBJECTIVE

To study whether an interaction between IgE- and TLR-mediated activation of human mast cells can contribute to exacerbated inflammatory responses.

METHODS

Peripheral blood-derived mast cells were stimulated with TLR ligands, in the presence or absence of anti-IgE triggering, after which degranulation was measured using flow cytometry and cytokine production was evaluated by multiplex assays, and ELISA. For evaluation of allergen-specific responses, mast cells were sensitized with serum of allergic individuals or controls, after which they were stimulated using allergens in combination with TLR ligands.

RESULTS

Simultaneous triggering of mast cells via IgE and TLR ligands greatly enhanced cytokine production but not IgE-induced degranulation. Different TLR ligands specifically enhanced the differential production of cytokines in conjunction with FcεRI triggering. Importantly, only TLR-4 and TLR-6 were able to induce robust production of IL-13, an important molecule in allergic reactions.

CONCLUSIONS & CLINICAL RELEVANCE

These results indicate that the simultaneous presence of pathogen- or danger-associated signals and FcεRI triggering via specific IgE can significantly modify mast cell-mediated allergic reactions via synergistic production of cytokines and inflammatory mediators and provide an explanation of augmented allergic symptoms during infection.

Pooled Sequencing of Candidate Genes Implicates Rare Variants in the Development of Asthma Following Severe RSV Bronchiolitis in Infancy

Severe infection with respiratory syncytial virus (RSV) during infancy is strongly associated with the development of asthma. To identify genetic variation that contributes to asthma following severe RSV bronchiolitis during infancy, we sequenced the coding exons of 131 asthma candidate genes in 182 European and African American children with severe RSV bronchiolitis in infancy using anonymous pools for variant discovery, and then directly genotyped a set of 190 nonsynonymous variants. Association testing was performed for physician-diagnosed asthma before the 7^th birthday (asthma) using genotypes from 6,500 individuals from the Exome Sequencing Project (ESP) as controls to gain statistical power. In addition, among patients with severe RSV bronchiolitis during infancy, we examined genetic associations with asthma, active asthma, persistent wheeze, and bronchial hyperreactivity (methacholine PC₂₀) at age 6 years. We identified four rare nonsynonymous variants that were significantly associated with asthma following severe RSV bronchiolitis, including single variants in ADRB2, FLG and NCAM1 in European Americans (p = 4.6x10^-4, 1.9x10^-13 and 5.0x10^-5, respectively), and NOS1 in African Americans (p = 2.3x10^-11). One of the variants was a highly functional nonsynonymous variant in ADRB2 (rs1800888), which was also nominally associated with asthma (p = 0.027) and active asthma (p = 0.013) among European Americans with severe RSV bronchiolitis without including the ESP. Our results suggest that rare nonsynonymous variants contribute to the development of asthma following severe RSV bronchiolitis in infancy, notably in ADRB2. Additional studies are required to explore the role of rare variants in the etiology of asthma and asthma-related traits following severe RSV bronchiolitis.

Healthcare Resource Utilization in Patients Receiving Omalizumab for Allergic Asthma in a Real-World Setting

Introduction

Inadequately controlled asthma is associated with increased healthcare resource utilization. The eXpeRience registry was initiated to evaluate real-world outcomes in patients receiving omalizumab for uncontrolled persistent allergic asthma. The current analysis of data from the eXpeRience registry focuses on healthcare resource utilization and on absences from work or school.

Methods

The eXpeRience was a 2-year, multinational, non-interventional, observational registry conducted to investigate real-world outcomes among patients receiving omalizumab in accordance with country-specific prescribing criteria for the treatment of uncontrolled persistent allergic asthma. Asthma-related healthcare resource utilization (hospitalizations, emergency room visits or unscheduled-asthma-related doctor visits or interventions) and absences from work or school were assessed pre-treatment (12-month data were collected retrospectively at baseline) and at months 12 and 24 after the initiation of omalizumab treatment. Serious adverse event (SAE) data were also assessed.

Results

A total of 943 patients (mean age 45 years; female 65%) were enrolled in the registry. Overall, the mean (standard deviation [SD]) number of asthma-related medical healthcare uses per patient decreased from 6.2 (6.97) during the pre-treatment period to 1.0 (1.96) and 0.5 (1.28) at months 12 and 24, respectively. The mean (SD) number of work or school days missed due to asthma was also lower at months 12 (3.5 [17.28] and 1.6 [4.28], respectively) and 24 (1.0 [4.66] and 1.9 [5.46], respectively) compared with the pre-treatment period (26.4 [49.61] and 20.7 [27.49], respectively). The nature and frequency of SAEs in the eXpeRience registry were comparable to that seen in interventional clinical trials with omalizumab.

Conclusion

The results of the eXpeRience registry indicate that omalizumab is associated with reductions in healthcare utilization, and in the number of days of absence from work or school, in patients with uncontrolled persistent allergic asthma in the real-world setting.

Funding

Novartis Pharma AG, Basel, Switzerland.

Electronic supplementary material

The online version of this article (doi:10.1007/s13554-014-0019-z) contains supplementary material, which is available to authorized users.

Asthma exacerbation in children: relationship among pollens, weather, and air pollution

BACKGROUND

Asthma exacerbation is an episode of (sub)acute worsening of asthmatic symptoms. Exacerbation may depend on environmental factors.

OBJECTIVE

The present study investigated emergency calls for asthma exacerbation in children, analysing: i) their trend over the course of time; and ii) their possible relationship with environmental factors, including pollen count, meteorological parameters, and air pollution.

METHODS

Emergency calls for exacerbation were recorded for 10 years (from 2002 to 2011) in Genoa (Italy). Betulaceae, Urticaceae, Gramineae, and Oleaceae pollen counts were measured. Meteorological parameters and air pollutants were also measured in the same area and for the same period.

RESULTS

The number of emergency calls did not significantly modify during the time studied. Two main peaks were detected: during the autumn and the spring. Wind speed significantly diminished as did most air pollutants. There were significant and relevant relationships between emergency calls and: pollens during the spring (r = 0.498), rainfall (r = 0.818), wind speed (r = 0.727), and air pollutants (r = 0.622 for SO2; r = 0.699 for NO; r = 0.58 for NO2).

CONCLUSIONS

This 10-year survey demonstrates that: (i) asthma exacerbations did not diminish over the time; (ii) there were seasonal peaks (autumn and spring); (iii) pollens (mainly Parietaria), wind speed and rainfall, SO2, NO, O3 and NO2 were strongly associated with asthma exacerbations in children in this area. Therefore, asthma exacerbations may significantly depend on environmental variations.

Comparison of vilanterol, a novel long-acting beta2 agonist, with placebo and a salmeterol reference arm in asthma uncontrolled by inhaled corticosteroids

Background

Current maintenance therapies for asthma require twice-daily dosing. Vilanterol (VI) is a novel long-acting beta₂ agonist, under development in combination with fluticasone furoate, a new inhaled corticosteroid (ICS). Findings from a previous 4-week study suggested that VI has inherent 24-hour activity and is therefore suitable for once-daily dosing. The study described here was a double-blind, double-dummy, randomised, placebo-controlled trial, the aim of which was to assess the efficacy of once-daily VI compared with placebo in patients with persistent asthma. The primary endpoint was change from baseline in 24-hour weighted mean forced expiratory volume in 1 second after 12 weeks of treatment vs. placebo. An active control arm received salmeterol (SAL) twice daily. All patients were maintained on a stable background dose of ICS.

Results

Patients (n = 347) received VI, placebo or SAL (1:1:1). For the primary endpoint, substantial improvements in lung function were seen with VI (359 ml), SAL (283 ml) and placebo (289 ml). There were no statistically significant treatment differences between either the VI (70 ml, P = 0.244) or SAL (-6 ml, P = 0.926) groups and placebo. Both active treatments were well tolerated, with similarly low rates of treatment-related adverse events compared with placebo. No treatment-related serious adverse events occurred.

Conclusions

This study failed to show a treatment difference between VI and placebo for the primary endpoint, in the presence of a placebo response of unforeseen magnitude. Because the placebo response was so large, it is not possible to draw meaningful conclusions from the data. The reason for this magnitude of effect is unclear but it may reflect increased compliance with the anti-inflammatory therapy regimen during the treatment period.

Trial registration

NCT01181895 at ClinicalTrials.gov.

Inhaled environmental allergens and toxicants as determinants of the asthma phenotype

The driving environmental factors behind the development of the asthma phenotype remain incompletely studied and understood. Here, we present an overview of inhaled allergic/atopic and mainly nonallergic/nonatopic or toxicant shapers of the asthma phenotype, which are present in both the indoor and outdoor environment around us. The inhaled allergic/atopic factors include fungus, mold, animal dander, cockroach, dust mites, and pollen; these allergic triggers and shapers of the asthma phenotype are considered in the context of their ability to drive the immunologic IgE response and potentially induce interactions between the innate and adaptive immune responses, with special emphasis on the NADPH-dependent reactive oxygen-species-associated mechanism of pollen-associated allergy induction. The inhaled nonallergic/nonatopic, toxicant factors include gaseous and volatile agents, such as sulfur dioxide, ozone, acrolein, and butadiene, as well as particulate agents, such as rubber tire breakdown particles, and diesel exhaust particles. These toxicants are reviewed in terms of their relevant chemical characteristics and hazard potential, ability to induce airway dysfunction, and potential for driving the asthma phenotype. Special emphasis is placed on their interactive nature with other triggers and drivers, with regard to driving the asthma phenotype. Overall, both allergic and nonallergic environmental factors can interact to acutely exacerbate the asthma phenotype; some may also promote its development over prolonged periods of untreated exposure, or possibly indirectly through effects on the genome. Further therapeutic considerations should be given to these environmental factors when determining the best course of personalized medicine for individuals with asthma.

Evaluation of coagulation activation after rhinovirus infection in patients with asthma and healthy control subjects: an observational study

Background

Asthma exacerbations are frequently triggered by rhinovirus infections. Both asthma and respiratory tract infection can activate haemostasis. Therefore we hypothesized that experimental rhinovirus-16 infection and asthmatic airway inflammation act in synergy on the haemostatic balance.

Methods

28 patients (14 patients with mild allergic asthma and 14 healthy non-allergic controls) were infected with low-dose rhinovirus type 16. Venous plasma and bronchoalveolar lavage fluid (BAL fluid) were obtained before and 6 days after infection to evaluate markers of coagulation activation, thrombin-antithrombin complexes, von Willebrand factor, plasmin-antiplasmin complexes, plasminogen activator inhibitor type-1, endogenous thrombin potential and tissue factor-exposing microparticles by fibrin generation test, in plasma and/or BAL fluid. Data were analysed by nonparametric tests (Wilcoxon, Mann Whitney and Spearman correlation).

Results

13 patients with mild asthma (6 females, 19-29 y) and 11 healthy controls (10 females, 19-31 y) had a documented Rhinovirus-16 infection. Rhinovirus-16 challenge resulted in a shortening of the fibrin generation test in BAL fluid of asthma patients (t = -1: 706 s vs. t = 6: 498 s; p = 0.02), but not of controls (t = -1: 693 s vs. t = 6: 636 s; p = 0.65). The fold change in tissue factor-exposing microparticles in BAL fluid inversely correlated with the fold changes in eosinophil cationic protein and myeloperoxidase in BAL fluid after virus infection (r = -0.517 and -0.528 resp., both p = 0.01).

Rhinovirus-16 challenge led to increased plasminogen activator inhibitor type-1 levels in plasma in patients with asthma (26.0 ng/mL vs. 11.5 ng/mL in healthy controls, p = 0.04). Rhinovirus-16 load in BAL showed a linear correlation with the fold change in endogenous thrombin potential, plasmin-antiplasmin complexes and plasminogen activator inhibitor type-1.

Conclusions

Experimental rhinovirus infection induces procoagulant changes in the airways of patients with asthma through increased activity of tissue factor-exposing microparticles. These microparticle-associated procoagulant changes are associated with both neutrophilic and eosinophilic inflammation. Systemic activation of haemostasis increases with Rhinoviral load.

Trial registration

This trial was registered at the Dutch trial registry (http://www.trialregister.nl): NTR1677.

Natural killer cell NKG2D and granzyme B are critical for allergic pulmonary inflammation

BACKGROUND

The diverse roles of innate immune cells in the pathogenesis of asthma remain to be fully defined. Natural killer (NK) cells are innate lymphocytes that can regulate adaptive immune responses. NK cells are activated in asthma; however, their role in allergic airway inflammation is not fully understood.

OBJECTIVE

We investigated the importance of NK cells in house dust mite (HDM)-triggered allergic pulmonary inflammation. Specifically, we aimed to determine the role of the major NK-cell activating receptor NKG2D and NK-cell effector functions mediated by granzyme B.

METHODS

Allergic airway inflammation was induced in the airways of mice by repeated intranasal HDM extract administration and responses in wild-type and NKG2D-deficient mice were compared. Adoptive transfer studies were used to identify the cells and mechanisms involved.

RESULTS

Mice that lacked NKG2D were resistant to the induction of allergic inflammation and showed little pulmonary eosinophilia, few airway TH2 cells, and no rise in serum IgE after multiple HDM-allergen exposures. However, NKG2D was not required for pulmonary inflammation after a single inoculation of allergen. NKG2D-deficient mice showed no alteration in responses to respiratory virus infection. Transfer of wild-type NK cells (but not CD3(+) cells) into NKG2D-deficient mice restored allergic inflammatory responses only if the NK cells expressed granzyme B.

CONCLUSIONS

These studies established a pivotal role for NK-cell NKG2D and granzyme B in the pathogenesis of HDM-induced allergic lung disease, and identified novel therapeutic targets for the prevention and treatment of asthma.

Activation of human basophils by combined toll-like receptor- and FcεRI-triggering can promote Th2 skewing of naive T helper cells

Basophils are mostly known for their involvement in allergic reactions. Recent studies in mice indicate a role for basophils in the induction of adaptive immunity, especially T helper 2 (Th2) responses. Therefore, it would be highly important to understand how basophils respond to pathogen-associated molecules, such as ligands for toll-like receptors (TLRs), and if the basophils could promote Th2 responses via these stimuli. To this end, the activation of basophils via TLRs in combination with activation via IgE was studied, as well as its effect on T helper cell skewing. Using quantitative PCR, we demonstrated the presence of mRNA for TLRs 1-8 in human basophils. Basophils responded to TLR triggering with differential cytokine production, but not with degranulation. Simultaneous triggering of TLRs and IgE led to synergy in production of IL-4, IL-8, IL-13, and RANTES. Furthermore, the synergistic effects on basophils mediated by IgE and TLR-4 triggering allowed robust Th2 skewing upon activation of naïve human CD4⁺ T cells. Our data show that human basophils respond to TLR ligands in synergy with IgE-mediated activation and that the cytokines produced can promote Th2 differentiation. These results indicate a role for basophils in the regulation of T-cell responses in humans.

Differences in respiratory syncytial virus and influenza infection in a house-dust-mite-induced asthma mouse model: consequences for steroid sensitivity

A significant number of clinical asthma exacerbations are triggered by viral infection. We aimed to characterize the effect of virus infection in an HDM (house dust mite) mouse model of asthma and assess the effect of oral corticosteroids. HDM alone significantly increased eosinophils, lymphocytes, neutrophils, macrophages and a number of cytokines in BAL (bronchoalveolar lavage), all of which were sensitive to treatment with prednisolone (with the exception of neutrophils). Virus infection also induced cell infiltration and cytokines. RSV (respiratory syncytial virus) infection in HDM-treated animals further increased all cell types in BAL (except eosinophils, which declined), but induced no further increase in HDM-elicited cytokines. However, while HDM-elicited TNF-α (tumour necrosis factor-α), IFN-γ (interferon-γ), IL (interleukin)-2, IL-5 and IL-10 were sensitive to prednisolone treatment, concomitant infection with RSV blocked the sensitivity towards steroid. In contrast, influenza infection in HDM- challenged animals resulted in increased BAL lymphocytes, neutrophils, IFN-γ, IL-1β, IL-4, IL-5, IL-10 and IL-12, but all were attenuated by prednisolone treatment. HDM also increased eNO (exhaled NO), which was further increased by concomitant virus infection. This increase was only partially attenuated by prednisolone. RSV infection alone increased BAL mucin. However, BAL mucin was increased in HDM animals with virus infection. Chronic HDM challenge in mice elicits a broad inflammatory response that shares many characteristics with clinical asthma. Concomitant influenza or RSV infection elicits differing inflammatory profiles that differ in their sensitivity towards steroids. This model may be suitable for the assessment of novel pharmacological interventions for asthmatic exacerbation.

Smoking in asthma is associated with elevated levels of corticosteroid resistant sputum cytokines-an exploratory study

Background

Current cigarette smoking is associated with reduced acute responses to corticosteroids and worse clinical outcomes in stable chronic asthma. The mechanism by which current smoking promotes this altered behavior is currently unclear. Whilst cytokines can induce corticosteroid insensitivity in-vitro, how current and former smoking affects airway cytokine concentrations and their responses to oral corticosteroids in stable chronic asthma is unclear.

Objectives

To examine blood and sputum cytokine concentrations in never, ex and current smokers with asthma before and after oral corticosteroids.

Methods

Exploratory study utilizing two weeks of oral dexamethasone (equivalent to 40 mg/day prednisolone) in 22 current, 21 never and 10 ex-smokers with asthma. Induced sputum supernatant and plasma was obtained before and after oral dexamethasone. 25 cytokines were measured by multiplex microbead system (Invitrogen, UK) on a Luminex platform.

Results

Smokers with asthma had elevated sputum cytokine interleukin (IL) -6, -7, and -12 concentrations compared to never smokers with asthma. Few sputum cytokine concentrations changed in response to dexamethasone IL-17 and IFNα increased in smokers, CCL4 increased in never smokers and CCL5 and CXCL10 reduced in ex-smokers with asthma. Ex-smokers with asthma appeared to have evidence of an ongoing corticosteroid resistant elevation of cytokines despite smoking cessation. Several plasma cytokines were lower in smokers with asthma compared to never smokers with asthma.

Conclusion

Cigarette smoking in asthma is associated with a corticosteroid insensitive increase in multiple airway cytokines. Distinct airway cytokine profiles are present in current smokers and never smokers with asthma and could provide an explanatory mechanism for the altered clinical behavior observed in smokers with asthma.

Rhinovirus wheezing illness and genetic risk of childhood-onset asthma

BACKGROUND

Both genetic variation at the 17q21 locus and virus-induced respiratory wheezing illnesses are associated with the development of asthma. Our aim was to determine the effects of these two factors on the risk of asthma in the Childhood Origins of Asthma (COAST) and the Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohorts.

METHODS

We tested genotypes at the 17q21 locus for associations with asthma and with human rhinovirus (HRV) and respiratory syncytial virus (RSV) wheezing illnesses and tested for interactions between 17q21 genotypes and HRV and RSV wheezing illnesses with respect to the risk of asthma. Finally, we examined genotype-specific expression of 17q21 genes in unstimulated and HRV-stimulated peripheral-blood mononuclear cells (PBMCs).

RESULTS

The 17q21 variants were associated with HRV wheezing illnesses in early life, but not with RSV wheezing illnesses. The associations of 17q21 variants with asthma were restricted to children who had had HRV wheezing illnesses, resulting in a significant interaction effect with respect to the risk of asthma. Moreover, the expression levels of ORMDL3 and of GSDMB were significantly increased in HRV-stimulated PBMCs, as compared with unstimulated PBMCs. The expression of these genes was associated with 17q21 variants in both conditions, although the increase with exposure to HRV was not genotype-specific.

CONCLUSIONS

Variants at the 17q21 locus were associated with asthma in children who had had HRV wheezing illnesses and with expression of two genes at this locus. The expression levels of both genes increased in response to HRV stimulation, although the relative increase was not associated with the 17q21 genotypes. (Funded by the National Institutes of Health.).

Triggers of asthma and COPD: are they different?

BACKGROUND

Asthma symptoms can be triggered by a variety of factors commonly referred to as "triggers". Some of these factors can also induce severe asthma exacerbations. Thus, it can be assumed that actions taken against such triggers may prevent the progression of the disease. However, limited data exist on the clinical importance of these triggers in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To compare the effect of triggers on symptoms and actions taken against certain modifiable triggers in patients with asthma and COPD.

METHODS

The study was conducted in a university hospital between June 2009 and June 2010. Patients with asthma and COPD were asked to complete a questionnaire in which both the factors triggering symptoms and the actions taken against several triggers were assessed.

RESULTS

Three hundred consecutive adult patients (150 asthma, 150 COPD) were enrolled to the study. The frequency of triggering factors was similar in both groups. Vaccination rates for influenza and pneumococcus were significantly higher in patients with COPD. However, such anti-allergic approaches as the use of strategies to decrease dust exposure, the use of anti-mite bed sheets, and the removal of pets from the home were more commonly employed by asthmatic patients.

CONCLUSION

This study revealed that certain triggers affected COPD and asthma patients to the same degree. Therefore, triggers and strategies for controlling modifiable triggers should be more concentrated on during education in both groups. However, the preventive effect of these strategies on disease progression, particularly in patients with COPD, needs clarification.

Assistance model for patients with asthma in the primary care

To create a program structured for the control and prevention towards asthma worsening, it is necessary to settle down actions of regionalization, planning and management. Currently, the Ministerial orders allow each municipality district to cope their needs with local initiatives, based on the search of the health indicators with University partnerships. Taking into account this context, it is feasible the implantation of an effective model through organized demand of attendance flow and physical structure, besides the withdrawal of medications and professional training. To describe the modus operandi situation currently in the Primary Health Care Units regarding these patients' reception, diagnosis, and follow-up, as well as the current situation according to the professional profile and sector. To introduce an assistance model for reception, of these patients in these primary care units. This is a bibliographical review based on the specialized literature such as scientific papers selected through the search on the SciELO and Bireme databases, from Medline and Lilacs data sources. A Committee was set up by members from the Health and Service , the Medical School, and scientific societies for discussion and planning.

[Respiratory allergens and asthma exacerbation]

INTRODUCTION

Asthma exacerbations are characterized by a progressive aggravation of respiratory symptoms such as dyspnea, cough, wheezing or chest tightness.

BACKGROUND

The relationship between allergy and asthma exacerbations has been evaluated by epidemiological studies based on various criteria such as oral corticosteroid requirement, emergency room visits and hospital admission for asthma. Many studies have observed that deteriorating asthma can be related to increased exposure to allergens, particularly allergens from house dust mite, cockroach, cat, rodent, mold or pollen. Several studies have demonstrated that sensitization to respiratory allergens and allergen exposure increases the risk of exacerbation of asthma. When asthma exacerbations are work-related, occupational allergens may be implicated.

CONCLUSIONS AND PERSPECTIVES

Most studies provide evidence that allergen exposure contributes to the risk of asthma exacerbations, but other precipitating factors, such as viruses, can interact and increase the risk.

Intranasal administration of poly(I:C) and LPS in BALB/c mice induces airway hyperresponsiveness and inflammation via different pathways

Background

Bacterial and viral infections are known to promote airway hyperresponsiveness (AHR) in asthmatic patients. The mechanism behind this reaction is poorly understood, but pattern recognizing Toll-like receptors (TLRs) have recently been suggested to play a role.

Materials and Methods

To explore the relation between infection-induced airway inflammation and the development of AHR, poly(I:C) activating TLR3 and LPS triggering TLR4, were chosen to represent viral and bacterial induced interactions, respectively. Female BALB/c or MyD88-deficient C57BL/6 mice were treated intranasally with either poly(I:C), LPS or PBS (vehicle for the control group), once a day, during 4 consecutive days.

Results

When methacholine challenge was performed on day 5, BALB/c mice responded with an increase in airway resistance. The maximal resistance was higher in the poly(I:C) and LPS treated groups than among the controls, indicating development of AHR in response to repeated TLR activation. The proportion of lymphocytes in broncheoalveolar lavage fluid (BALF) increased after poly(I:C) treatment whereas LPS enhanced the amount of neutrophils. A similar cellular pattern was seen in lung tissue. Analysis of 21 inflammatory mediators in BALF revealed that the TLR response was receptor-specific. MyD88-deficient C57BL/6 mice responded to poly (I:C) with an influx of lymphocytes, whereas LPS caused no inflammation.

Conclusion

In vivo activation of TLR3 and TLR4 in BALB/c mice both caused AHR in conjunction with a local inflammatory reaction. The AHR appeared to be identical regardless of which TLR that was activated, whereas the inflammation exhibited a receptor specific profile in terms of both recruited cells and inflammatory mediators. The inflammatory response caused by LPS appeared to be dependent on MyD88 pathway. Altogether the presented data indicate that the development of AHR and the induction of local inflammation might be the result of two parallel events, rather than one leading to another.

Daily exhaled nitric oxide measurements and asthma exacerbations in children

BACKGROUND

Fractional exhaled Nitric Oxide (FeNO) is a biomarker for eosinophilic airway inflammation and can be measured at home on a daily basis. A short-term increase in FeNO may indicate a higher risk of future asthma exacerbations.

OBJECTIVE

To assess changes in FeNO before and after asthma exacerbations compared to a stable control period.

METHODS

A post hoc analysis was performed on daily FeNO measurements over 30 weeks in children with asthma (n = 77). Moderate exacerbations were defined by an increase in symptom scores and severe exacerbations by prescription of prednisone. Individual mean and maximum FeNO, the variability of FeNO assessed by the coefficient of variation (CV), and slopes of FeNO in time were all quantified in 3-week blocks. Cross-correlation of FeNO with symptoms and autocorrelation of FeNO were assessed in relation to exacerbations and examined as predictors for exacerbations compared to reference periods using logistic regression.

RESULTS

Fractional exhaled nitric oxide could be assessed in relation to 25 moderate and 12 severe exacerbations. The CV, slope, cross-correlation, and autocorrelation of daily FeNO increased before moderate exacerbations. Increases in slope were also randomly seen in 19% of 2-week blocks of children without exacerbations. At least 3-5 FeNO measurements in the 3 weeks before an exacerbation were needed to calculate a slope that could predict moderate exacerbations. No specific pattern of FeNO was seen before severe exacerbations.

CONCLUSION

Fractional exhaled nitric oxide monitoring revealed changes in FeNO prior to moderate exacerbations. Whether this can be used to prevent loss of asthma control should be further explored.

Diminished levels of nasal S100A7 (psoriasin) in seasonal allergic rhinitis: an effect mediated by Th2 cytokines

BACKGROUND

S100A7 is an antimicrobial peptide involved in several inflammatory diseases. The aim of the present study was to explore the expression and regulation of S100A7 in seasonal allergic rhinitis (SAR).

METHODS

Nasal lavage (NAL) fluid was obtained from healthy controls before and after lipopolysaccharide (LPS) provocation, from SAR patients before and after allergen challenge, and from SAR patients having completed allergen-specific immunotherapy (ASIT). Nasal biopsies, nasal epithelial cells and blood were acquired from healthy donors. The airway epithelial cell line FaDu was used for in vitro experiments. Real-time RT-PCR and immunohistochemistry were used to determine S100A7 expression in nasal tissue and cells. Release of S100A7 in NAL and culture supernatants was measured by ELISA. The function of recombinant S100A7 was explored in epithelial cells, neutrophils and peripheral blood mononuclear cells (PBMC).

RESULTS

Nasal administration of LPS induced S100A7 release in healthy non-allergic subjects. The level of S100A7 was lower in NAL from SAR patients than from healthy controls, and it was further reduced in the SAR group 6 h post allergen provocation. In contrast, ASIT patients displayed higher levels after completed treatment. S100A7 was expressed in the nasal epithelium and in glands, and it was secreted by cultured epithelial cells. Stimulation with IL-4 and histamine repressed the epithelial S100A7 release. Further, recombinant S100A7 induced activation of neutrophils and PBMC.

CONCLUSIONS

The present study shows an epithelial expression and excretion of S100A7 in the nose after microbial stimulation. The levels are diminished in rhinitis patients and in the presence of an allergic cytokine milieu, suggesting that the antimicrobial defense is compromised in patients with SAR.

NOD-like receptors and RIG-I-like receptors in human eosinophils: activation by NOD1 and NOD2 agonists

NOD-like receptors (NLRs) and RIG-I-like receptors (RLRs) are newly discovered pattern-recognition receptors. They detect substructures of bacterial peptidoglycan and viral RNA, respectively, thereby initiating an immune response. However, their role in eosinophil activation remains to be explored. The aim of this study was to characterize the expression of a range of NLRs and RLRs in purified human eosinophils and assess their functional importance. Expression of NOD1, NOD2, NLRP3, RIG-I and MDA-5 was investigated using real-time reverse transcription PCR, flow cytometry and immunohistochemistry. The effects of the corresponding agonists iE-DAP (NOD1), MDP (NOD2), alum (NLRP3) and poly(I:C)/LyoVec (RIG-I/MDA-5) were studied in terms of cytokine secretion, degranulation, survival, expression of adhesion molecules and activation markers, and chemotactic migration. Eosinophils expressed NOD1 and NOD2 mRNA and protein. Low levels of RIG-I and MDA-5 were found, whereas expression of NLRP3 was completely absent. In accordance, stimulation with iE-DAP and MDP was found to induce secretion of interleukin-8, up-regulate expression of CD11b, conversely down-regulate CD62 ligand, increase expression of CD69 and induce migration. The MDP also promoted release of eosinophil-derived neurotoxin, whereas iE-DAP failed to do so. No effects were seen upon stimulation with alum or poly(I:C)/LyoVec. Moreover, the NOD1-induced and NOD2-induced activation was mediated via the nuclear factor-κB signalling pathway and augmented by interleukin-5 and granulocyte-macrophage colony-stimulating factor, but not interferon-γ. Taken together, the NLR system represents a novel pathway for eosinophil activation. The responses are enhanced in the presence of cytokines that regulate T helper type 2 immunity, suggesting that the NLRs constitute a link between respiratory infections and exacerbations of allergic disease.

Monoclonal antibodies for the treatment of asthma

Asthma is a chronic inflammatory disease of the airways which can have a detrimental effect on quality of life and in extreme cases cause death. Although the majority of patients can control their asthma symptoms with a combination of steroids and beta agonists there is still a group of patients whose asthma remains symptomatic despite the best available treatment. These severe asthmatic patients represent the unmet medical need in asthma and are the focus of those developing novel monoclonal antibody based drugs. The complex networks of cytokines and cells involved in the pathology of asthma provide plenty of scope for intervention with monoclonal antibody based drugs which are able to block cytokine or chemokine receptor interactions, deplete cells expressing a specific receptor or block cell/cell interactions. At present anti-IgE (Xolair©) is the only monoclonal antibody based drug approved for the treatment of asthma. However, a number of other antibody based drugs have been clinically tested in asthma including anti-IL-5, anti-IL-4, anti-IL-13, anti-TNFα, anti-CCR3, anti-CCR4 and anti-OX40L. This review will examine the development of these monoclonal antibody based therapies. Since many of these therapies have targeted key pathways in asthma pathology these studies provide information on patient stratification and asthma pathology.

Pathways activated during human asthma exacerbation as revealed by gene expression patterns in blood

BACKGROUND

Asthma exacerbations remain a major unmet clinical need. The difficulty in obtaining airway tissue and bronchoalveolar lavage samples during exacerbations has greatly hampered study of naturally occurring exacerbations. This study was conducted to determine if mRNA profiling of peripheral blood mononuclear cells (PBMCs) could provide information on the systemic molecular pathways involved during asthma exacerbations.

METHODOLOGY/PRINCIPAL FINDINGS

Over the course of one year, gene expression levels during stable asthma, exacerbation, and two weeks after an exacerbation were compared using oligonucleotide arrays. For each of 118 subjects who experienced at least one asthma exacerbation, the gene expression patterns in a sample of peripheral blood mononuclear cells collected during an exacerbation episode were compared to patterns observed in multiple samples from the same subject collected during quiescent asthma. Analysis of covariance identified genes whose levels of expression changed during exacerbations and returned to quiescent levels by two weeks. Heterogeneity among visits in expression profiles was examined using K-means clustering. Three distinct exacerbation-associated gene expression signatures were identified. One signature indicated that, even among patients without symptoms of respiratory infection, genes of innate immunity were activated. Antigen-independent T cell activation mediated by IL15 was also indicated by this signature. A second signature revealed strong evidence of lymphocyte activation through antigen receptors and subsequent downstream events of adaptive immunity. The number of genes identified in the third signature was too few to draw conclusions on the mechanisms driving those exacerbations.

CONCLUSIONS/SIGNIFICANCE

This study has shown that analysis of PBMCs reveals systemic changes accompanying asthma exacerbation and has laid the foundation for future comparative studies using PBMCs.

Procalcitonin and C-reactive protein in hospitalized adult patients with community-acquired pneumonia or exacerbation of asthma or COPD

BACKGROUND

Antibiotic overuse in respiratory illness is common and is associated with drug resistance and hospital-acquired infection. Biomarkers that can identify bacterial infections may reduce antibiotic prescription. We aimed to compare the usefulness of the biomarkers procalcitonin and C-reactive protein (CRP) in patients with pneumonia or exacerbations of asthma or COPD.

METHODS

Patients with a diagnosis of community-acquired pneumonia or exacerbation of asthma or COPD were recruited during the winter months of 2006 to 2008. Demographics, clinical data, and blood samples were collected. Procalcitonin and CRP concentrations were measured from available sera.

RESULTS

Sixty-two patients with pneumonia, 96 with asthma, and 161 with COPD were studied. Serum procalcitonin and CRP concentrations were strongly correlated (Spearman rank correlation coefficient [rs] = 0.56, P < .001). Patients with pneumonia had increased procalcitonin and CRP levels (median [interquartile range] 1.27 ng/mL [2.36], 191 mg/L [159]) compared with those with asthma (0.03 ng/mL [0.04], 9 mg/L [21]) and COPD (0.05 ng/mL [0.06], 16 mg/L [34]). The area under the receiver operating characteristic curve (95% CI) for distinguishing between patients with pneumonia (antibiotics required) and exacerbations of asthma (antibiotics not required), for procalcitonin and CRP was 0.93 (0.88-0.98) and 0.96 (0.93-1.00). A CRP value > 48 mg/L had a sensitivity of 91% (95% CI, 80%-97%) and specificity of 93% (95% CI, 86%-98%) for identifying patients with pneumonia.

CONCLUSIONS

Procalcitonin and CRP levels can both independently distinguish pneumonia from exacerbations of asthma. CRP levels could be used to guide antibiotic therapy and reduce antibiotic overuse in hospitalized patients with acute respiratory illness.

IL-28A (IFN-λ2) modulates lung DC function to promote Th1 immune skewing and suppress allergic airway disease

IL-28 (IFN-λ) cytokines exhibit potent antiviral and antitumor function but their full spectrum of activities remains largely unknown. Recently, IL-28 cytokine family members were found to be profoundly down-regulated in allergic asthma. We now reveal a novel role of IL-28 cytokines in inducing type 1 immunity and protection from allergic airway disease. Treatment of wild-type mice with recombinant or adenovirally expressed IL-28A ameliorated allergic airway disease, suppressed Th2 and Th17 responses and induced IFN-γ. Moreover, abrogation of endogenous IL-28 cytokine function in IL-28Rα^−/− mice exacerbated allergic airway inflammation by augmenting Th2 and Th17 responses, and IgE levels. Central to IL-28A immunoregulatory activity was its capacity to modulate lung CD11c⁺ dendritic cell (DC) function to down-regulate OX40L, up-regulate IL-12p70 and promote Th1 differentiation. Consistently, IL-28A-mediated protection was absent in IFN-γ^−/− mice or after IL-12 neutralization and could be adoptively transferred by IL-28A-treated CD11c⁺ cells. These data demonstrate a critical role of IL-28 cytokines in controlling T cell responses in vivo through the modulation of lung CD11c⁺ DC function in experimental allergic asthma.