Induced sputum cell count and cytokine profile in atopic and non-atopic children with asthma

Revisiting differences between atopic and non-atopic asthmatics: When age is shaping airway inflammatory profile

Background

Atopic asthma is one of the most common asthma phenotypes and is generally opposed to the non-atopic counterpart. There have been very few large-scale studies comparing atopic and non-atopic asthmatics in terms of systemic and airway inflammation across the age spectrum.

Methods

Here, we have undertaken a retrospective study investigating 1626 patients (924 atopic and 702 non-atopic asthmatics) recruited from our university asthma clinic who underwent extensive clinical investigations including induced sputum. Atopy was defined by any positive specific IgE to common aeroallergens (>0,35 kU/L). We performed direct comparisons between the groups and sought to appreciate the influence of age on the airway and systemic inflammatory components. The study was approved by the ethics committee of the University Hospital of Liege (Ref. 2016/276). Informed consents were obtained from healthy subjects.

Results

Atopic asthmatics were younger (P < .001), had a higher male/female ratio (P < .001), an earlier disease onset (P < .001) and a greater proportion of treated rhinitis (P < .001) while non-atopic asthmatics had greater smoke exposure (P < .001), lower FEV₁/FVC ratio (P = .01) and diffusing capacity (P < .001). There was no difference between the 2 groups regarding FEV₁ (% predicted), asthma control, asthma quality of life and exacerbations in the previous 12 months. Regarding inflammation, atopic patients had higher FeNO levels (median = 28 ppb, P < .001), were more eosinophilic both in blood (median = 2.8%, P < .001) and in sputum (median = 2.2%, P < .001) while non-atopic patients displayed greater blood (median = 57%, P = .01) and sputum (median = 58.8%, P = .01) neutrophilic inflammation. However, stratifying patients by age showed that non-atopic asthmatics above 50 years old became equally eosinophilic in the sputum (P = .07), but not in the blood, as compared to atopic patients. Likewise, FeNO rose in non-atopic patients after 50 years old but remained, however, lower than in atopic patients.

Conclusions

We conclude that, while sharing many features, atopic group still differentiates from non-atopic asthmatics by demographics, functional and inflammatory profiles. When atopic asthmatics showed a constant eosinophilic pattern across the age spectrum, non-atopic asthmatics were found to be neutrophilic before the age of 50 but eosinophilic above 50 years old.

Bronchodilator response to albuterol nebulized with hypertonic saline in asthmatic children

INTRODUCTION

Asthma is distinguished by bronchial obstruction reversible by bronchodilators. The first-line treatment for asthmatic exacerbations is the use of inhaled beta-agonists, by pressurized metered-dose inhalers or nebulized with normal saline solution (NSS). There are no reports of nebulized beta agonists' efficacy in asthmatic children when administered with hypertonic saline solution (HSS).

OBJECTIVE

To evaluate bronchodilator responses (BDR) to albuterol nebulized with 3%-HSS in asthmatic children, compared to albuterol nebulized with NSS.

POPULATION AND METHODS

In a prospective, experimental, double-blind, randomized clinical study, children with a confirmed diagnosis of asthma with mild or moderate bronchial obstruction (FEV₁ 40%-79% of predicted) were randomized to receive a nebulization with 2.5 mg of albuterol diluted in 3 cc of 3%-HSS or NSS (0.9%), by means of a jet nebulizer. After 30 min, the BDR was assessed.

RESULTS

Fifty patients (mean age 12.0 ± 3 years, 29 males) were enrolled; 25 were randomized to the 3%-HSS group (FEV₁ 65.2% ± 10) and 25 to the NSS group (FEV₁ 69.1% ± 7.1). The BDR of FEV₁ was 41.2% (SD: ±20.1; 95% confidence interval [CI]: 35.1-50.4) and 17.3% (SD: ±19.4; 95% CI: 9.7-24.9) (p < .0001) and of maximum mid-expiratory flow was 130% (SD: ±90.8; 95% CI: 94.6-166) and 69.8% (SD: ±72.5; 95% CI: 41.4-98.2) (p < .01), for the 3%-HSS and NSS groups, respectively.

CONCLUSION

Albuterol produces a greater BDR when nebulized with 3%-HSS compared to NSS in asthmatic children with mild or moderate bronchial obstruction.

Allergic Endotypes and Phenotypes of Asthma

Allergic asthma is defined as asthma associated with sensitization to aeroallergens, which leads to asthma symptoms and airway inflammation. Allergic asthma is the most common asthma phenotype. The onset of allergic asthma is most often in childhood and is usually accompanied by other comorbidities including atopic dermatitis and allergic rhinitis. It is often persistent although there is a wide variation in disease severity. It is a T_H2-driven process. Biomarkers have been identified to distinguish patients with allergic asthma, particularly serum IgE levels, tests to indicate sensitization to aeroallergens such as specific IgE or skin prick test positivity, blood and sputum eosinophil levels, fraction of exhaled nitric oxide, and periostin. Treatments for allergic asthma include environmental control measures, allergen immunotherapy, and glucocorticoids. Biologics, targeting the T_H2 pathway, have been shown to be effective in the treatment of allergic asthma.

Childhood asthma: Novel endotyping by cytokines, validated through sensitization profiles and clinical characteristics

BACKGROUND

Specific allergy sensitization pattern, using "component-resolved diagnosis" (CRD), is a central component of allergy and asthma in childhood. Besides this, allergic asthma has been characterized by a Th2-shifted endotype with elevation of classical Th2 cytokines. Recently, other endotypes with distinct mechanisms focusing on cytokine regulation evolved, yet those pathways are still not well understood.

OBJECTIVE

(a) To define reproducible immunological endotypes using cytokine expression in an asthma cohort and (b) to characterize their sensitization profile and clinical phenotype.

METHODS

Supernatants from PBMCs of 234 children (median age 10 years) of an asthma cohort were analysed for cytokine expressions. The children were split into a training (n = 49) and validation (n = 185) group. The training group was used to identify immunological endotypes by clustering cytokine expressions, which were then assessed regarding clinical characteristics and specific IgE of recombinant allergen components. Next, our findings were validated in the validation group.

RESULTS

We identified novel endotypes based on primarily unstimulated cytokine expression. One endotype showed an IFN-γ/Interleukin (IL)-17/IL-5 predominance, a different sensitization pattern (high in birch/apple; p < .01), and inferior lung function (p < .01). A second endotype grouped young children with food allergy and reduced lung function. Our findings were reproducible in the validation group.

CONCLUSION AND CLINICAL RELEVANCE

We identified two novel clinical asthma endotypes via cytokine expression pattern with distinct sensitization patterns. These novel findings are critical for clinical guidance and open avenues for identifying underlying mechanisms and more patient-specific therapies.

Nasal interferon responses to community rhinovirus infections are similar in controls and children with asthma

BACKGROUND

Rhinovirus (RV) is the main cause of asthma exacerbations in children. Some studies reported that persons with asthma have attenuated interferon (IFN) responses to experimental RV infection compared with healthy individuals. However, responses to community-acquired RV infections in controls and children with asthma have not been compared.

OBJECTIVE

To evaluate nasal cytokine responses after natural RV infections in people with asthma and healthy children.

METHODS

We compared nasal cytokine expression among controls and children with asthma during healthy, virus-negative surveillance weeks and self-reported RV-positive sick weeks. A total of 14 controls and 21 patients with asthma were studied. Asthma disease severity was based on symptoms and medication use. Viral genome was detected by multiplex polymerase chain reaction. Nasal cytokine protein levels were determined by multiplex assays.

RESULTS

Two out of 47 surveillance weeks tested positive for RV, illustrating an asymptomatic infection rate of 5%. A total of 38 of 47 sick weeks (81%) tested positive for the respiratory virus. Of these, 33 (87%) were positive for RV. During well weeks, nasal interleukin 8 (IL-8), IL-12, and IL-1β levels were higher in children with asthma than controls. Compared with healthy virus-negative surveillance weeks, IL-8, IL-13, and interferon beta increased during colds only in patients with asthma. In both controls and children with asthma, the nasal levels of interferon gamma, interferon lambda-1, IL-1β, IL-8, and IL-10 increased during RV-positive sick weeks. During RV infection, IL-8, IL-1β, and tumor necrosis factor-α levels were strongly correlated.

CONCLUSION

In both controls and patients with asthma, natural RV infection results in robust type II and III IFN responses.

Differences between patients who achieved asthma control and those who remain uncontrolled after standardized severe asthma care strategy

OBJECTIVE

To assess clinical, functional, and inflammatory patterns of children and adolescents with severe uncontrolled asthma, and investigate the differences between patients who achieved asthma control and those who remain uncontrolled after standardized asthma care strategy.

METHODS

Screening all children and adolescents with asthma from the Pediatric Pulmonology Outpatient Clinic of Unicamp, Brazil, and included those with severe uncontrolled asthma according to GINA guidelines criteria. Patients were assessed at baseline and after by demographic and medication data, questionnaires (Asthma Control Test and Pediatric Asthma Quality of Life Questionnaire), Six-Minute Walk Test, skin prick test, spirometry, induced sputum, and blood collection (total immunoglobulin E and eosinophil count). Cytokine dosage was analyzed in sputum supernatant and serum by Cytometric Bead Array.

RESULTS

Thirty-three patients with severe uncontrolled asthma were included (median age 10.9 [7.00-17.60] years). All patients presented satisfactory adherence to treatment and 50% of them achieved good asthma control after six-month follow-up (p < 0.001). Patients who achieved asthma control reported higher intervals since their last exacerbation episode (p = 0.008) and higher quality of life scores (p < 0.001) as compared to patients who remained uncontrolled. We found no changes in lung function markers, inflammatory biomarkers, or cytokine levels between patients with uncontrolled and controlled asthma.

CONCLUSION

Participation of six months in a structured outpatient clinic for children with severe asthma had a notable improvement in control and quality of life of patients. This demonstrates the importance of a global assessment, focused on peculiarities presented by patients with severe uncontrolled asthma.

Inhalations with Brine Solution from the 'Wieliczka' Salt Mine Diminish Airway Hyperreactivity and Inflammation in a Murine Model of Non-Atopic Asthma

Inhalations with brine solutions are old but underestimated add-ons to pharmacological treatments of inflammatory lung diseases. Although widely used, not all features underlying their action on the respiratory system have been explored. The aim of the present study was to elucidate the mechanism of the beneficial action of inhalations of brine solution from the 'Wieliczka' Salt Mine, a Polish health resort, in a murine model of non-atopic asthma. Asthma was induced in BALB/c mice by skin sensitization with dinitrofluorobenzene followed by an intratracheal challenge of cognate hapten. All animals underwent 12 inhalation sessions with brine solution, pure water or physiological saline. Control mice were not inhaled. We found that brine inhalations reduced, as compared to non-inhaled mice, the typical asthma-related symptoms, like airway hyperreactivity (AHR), the infiltration of pro-inflammatory cells into the bronchial tree, and the inflammation of the airways at the level of pro-inflammatory cytokines IL-1α, IL-1β and IL-6. The level of the anti-inflammatory IL-10 was elevated in brine-inhaled mice. Inhalations with pure water increased AHR, whereas saline had no influence, either on AHR or cytokine concentrations. These observations indicate that inhalations with a brine solution from the 'Wieliczka' Salt Mine diminish the asthma-related symptoms, mostly by reducing the inflammatory status and by decreasing AHR.

Asthma: A Loss of Post-natal Homeostatic Control of Airways Smooth Muscle With Regression Toward a Pre-natal State

The defining feature of asthma is loss of normal post-natal homeostatic control of airways smooth muscle (ASM). This is the key feature that distinguishes asthma from all other forms of respiratory disease. Failure to focus on impaired ASM homeostasis largely explains our failure to find a cure and contributes to the widespread excessive morbidity associated with the condition despite the presence of effective therapies. The mechanisms responsible for destabilizing the normal tight control of ASM and hence airways caliber in post-natal life are unknown but it is clear that atopic inflammation is neither necessary nor sufficient. Loss of homeostasis results in excessive ASM contraction which, in those with poor control, is manifest by variations in airflow resistance over short periods of time. During viral exacerbations, the ability to respond to bronchodilators is partially or almost completely lost, resulting in ASM being "locked down" in a contracted state. Corticosteroids appear to restore normal or near normal homeostasis in those with poor control and restore bronchodilator responsiveness during exacerbations. The mechanism of action of corticosteroids is unknown and the assumption that their action is solely due to "anti-inflammatory" effects needs to be challenged. ASM, in evolutionary terms, dates to the earliest land dwelling creatures that required muscle to empty primitive lungs. ASM appears very early in embryonic development and active peristalsis is essential for the formation of the lungs. However, in post-natal life its only role appears to be to maintain airways in a configuration that minimizes resistance to airflow and dead space. In health, significant constriction is actively prevented, presumably through classic negative feedback loops. Disruption of this robust homeostatic control can develop at any age and results in asthma. In order to develop a cure, we need to move from our current focus on immunology and inflammatory pathways to work that will lead to an understanding of the mechanisms that contribute to ASM stability in health and how this is disrupted to cause asthma. This requires a radical change in the focus of most of "asthma research."

Smoke Exposure, Cytokine Levels, and Asthma Visits in Children Hospitalized for Bronchiolitis

BACKGROUND AND OBJECTIVE

To determine if cigarette smoke exposure, marijuana smoke exposure, or cytokine levels at admission to the hospital for bronchiolitis are associated with follow-up visits for asthma.

METHODS

We enrolled a cohort of children aged 31 days to 2 years who were hospitalized with bronchiolitis from January 2013 to April 2014. Data included the results of a baseline survey about children's health and demographics, nasal wash samples, the results of a 6-month postdischarge follow-up survey, and a chart review. Nasal wash samples were tested for interleukin (IL)-6, IL-13, and tumor necrosis factor α (TNF-α); values were categorized for analysis. χ2, Fisher's exact, and Wilcoxon rank tests were done to test bivariable differences; all analyses were done using SAS.

RESULTS

We approached 180 families for enrollment; 99 consented to participate, and 74% of these completed follow-up surveys. Half of those with high levels of IL-13 had follow-up visits for asthma, whereas only 4.2% of those with low levels had follow-up visits for asthma (P = .02). Marijuana exposure was reported for 12.5% (n = 7) of study participants. There was a significant association between marijuana exposure and TNF-α levels (P = .03).

CONCLUSIONS

Our study revealed an association between IL-13 and follow-up visits for asthma in children who were hospitalized with bronchiolitis. We found an association between family-reported marijuana smoke exposure and detectable but lower levels of TNF-α. Further research is needed to study these relationships.

Inflammation and asthma control in children with comorbid obstructive sleep apnea

OBJECTIVES

A bi-directional relationship exists between asthma and obstructive sleep apnea (OSA) in which presence of one is associated with increased prevalence and severity of the other. Our objective was to determine whether OSA accounted for differences in airway and systemic inflammation in asthmatic children and whether inflammation was associated with asthma control. We hypothesized that greater severity of SDB would correlate with increased upper airway and systemic inflammation and result in reduced asthma control.

METHODS

Non-obese children aged 4-12 years with persistent asthma, with or without OSA were recruited. Asthma control was measured with the Childhood Asthma Control Test. Children underwent polysomnography and blood sampling, and children with OSA underwent clinically indicated adenotonsillectomy. Tonsils and sera were analyzed for 11 cytokines.

RESULTS

Twenty-seven children (20 with OSA, seven without OSA) participated, mean age 7.9 years, 55.6% female, 92.6% African American. Levels did not differ for any cytokine between children with and without OSA. Lower nadir oxygen saturation was associated with higher levels of tonsil TNF-α (P < 0.001) and IL-10 (P < 0.05). Higher REM-related apnea-hypopnea index was associated with higher levels of tonsil TNF-α (P < 0.05). Children with uncontrolled asthma had significantly higher levels of serum IL-10, IL-13, and TNF-α, and tonsil TNF-α (all P < 0.05) than well-controlled asthmatic children. There was no association between OSA, or any polysomnography variable, and asthma control.

CONCLUSIONS

Despite the presence of OSA-associated airway inflammation, and asthma control-associated airway and systemic inflammation, OSA was not related to level of asthma control in this non-obese, largely minority, low income sample.

Asthma Endotyping and Biomarkers in Childhood Asthma

Childhood asthma represents a heterogeneous challenging disease, in particular in its severe forms. The identification of different asthma phenotypes has stimulated research in underlying molecular mechanisms, such as the endotypes, and paved the way to the search for related specific biomarkers, which may guide diagnosis, management, and predict response to treatment. A limited number of biomarkers are currently available in clinical practice in the pediatric population, mostly reflecting type 2-high airway inflammation. The identification of biomarkers of childhood asthma is an active area of research that holds a potential great clinical utility and may represent a step forward toward tailored management and therapy: the so-called Precision Medicine. The aim of the present review is to provide an updated overview of asthma endotyping, mostly focusing on novel noninvasive biomarkers in childhood asthma.

Biomarkers for the Phenotyping and Monitoring of Asthma in Children

An important issue in relation to the utility and reliability of biomarkers for asthma monitoring is how asthma is defined and characterized. What kind of asthma, or at what stage of the disease is a particular biomarker supposed to add information? Often, the purpose, or usefulness of a biomarker is not made clear. Diagnosis, severity evaluation, and monitoring are all different clinical uses for a biomarker, and confusion may arise when a biomarker is suitable for one of these but not another. When the utility of available biomarkers are discussed, these different roles need to be clarified. Our opinion is that there are four aspects of relevance to asthma, for which biomarkers are required: to diagnose allergies, to evaluate inflammation in the airways, to evaluate hyper-responsiveness, and for certain measures of lung function, such as lung clearance index. These types of biomarkers are needed for the phenotyping and monitoring of asthma. Another important role for biomarkers is, as mentioned above, to monitor asthma in order to follow treatment effects on inflammation and hyper-responsiveness as objective adjuncts to the patients' own symptom reports and lung function. This review will mainly focus on biomarkers that reflect airway inflammation. In spite of the numerous studies that have been conducted, we still have to remember that the value of biomarkers available for routine use, such as eosinophil counts in blood and sputum and exhaled nitric oxide, have to be interpreted in relation to reported symptoms and lung function. Measures of bronchial hyper-responsiveness, performed either by direct (methacholine challenge) or indirect (exercise or mannitol challenge) methods, could be considered biomarkers but will not be included in this review. On the other hand, diagnosing allergy is not usually useful for monitoring asthma although it is of fundamental importance for the interpretation of most biomarkers that are suitable for monitoring. We have therefore included the different approaches for diagnosing and evaluating allergic sensitization in this review.

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

IL-5, IL-8 and MMP -9 levels in exhaled breath condensate of atopic and nonatopic asthmatic children

RATIONALE

Asthma is a heterogeneous disease, and a great majority of pediatric patients with asthma demonstrate atopic characteristics and develop a Th2 type cytokine response. Nonatopic asthma, on the other hand, is seen more rarely.

METHODS

In this study, levels of IL-5, IL-8 and MMP-9 were measured in exhaled breath condensate (EBC) of the subjects to demonstrate the extent of tissue damage as well as eosinophilic and neutrophilic inflammation in children with atopic and nonatopic asthma. A total of 37 children with atopic asthma and 37 children with nonatopic asthma were enrolled in the study. Patients who exhibited protease positive aeroallergen (House dust mite, mould mix, olea, grass mix) sensitivity in allergen skin prick test were included in the atopic asthma group. To evaluate the EBC, the fluid content of the breath was collected by having the patients exhale into an EBC device, after which the IL-5, IL-8 and MMP-9 levels were assayed using the ELISA method.

RESULTS

The atopic asthmatics exhibited significantly higher IL-5 levels in their EBC samples than the nonatopic asthmatics (0.271 [0.198-0.489] pg/ml and 0.198 [0.125-0.344] pg/ml, respectively, p = 0.04), while no significant differences were observed in the levels of IL-8 and MMP-9 in the EBC samples of the atopic and nonatopic asthmatics.

CONCLUSIONS

IL-5 levels, as a marker of eosinophilic inflammation, were demonstrated to be higher in the children with atopic asthma when compared to those with nonatopic asthma in EBC. The fact that no significant difference was apparent in the IL-8 levels between the groups suggests that it is the severity of the disease rather than the atopic state that plays an important role in IL-8 levels. Since no difference was recorded between the groups in terms of MMP-9 levels, lung damage in asthma sufferers seems to develop independent of atopia.

[Determining asthma treatment in children by monitoring fractional exhaled nitric oxide, sputum eosinophils and leukotriene B₄]

Sputum eosinophils and exhaled fractional nitric oxide (FENO) are markers of airway inflammation in asthma. Cytokines, cysteinyl-leukotrienes and leukotriene B4 (LTB4) are responsible for this inflammation. The aim of this study is to determine the usefulness of these markers in monitoring asthma treatment in children. FENO, sputum eosinophils, and LTB4 in induced sputum were performed in 10 children (9-15 years old). These determinations were repeated four months later, after the beginning or an increase in the treatment. FENO values tended to decrease (P=.15), pulmonary function tended to improve (P=.10), and sputum eosinophils decreased (P=.003) compared to the first determination. There were no differences in LTB4 concentrations (P=.88). Sputum eosinophils seem to be more precise than FENO in the monitoring of inflammation in asthmatic children.