Eosinophil activity in infants hospitalized for wheezing and risk of persistent childhood asthma

A systematic review and meta-analysis on absolute eosinophil counts and the risk of asthma in preschool children with wheezing: An EAACI Task Force Report

Preschool children with wheezing disorders pose diagnostic and therapeutic challenges and consume substantial healthcare resources. Peripheral eosinophil blood count (EBC) has been proposed as a potential indicator for future asthma development. This review by the European Academy of Allergy and Clinical Immunology (EAACI) Preschool Wheeze Task Force aimed to provide systematic evidence for the association between increased EBC and the risk of future asthma, as well as to identify potential cutoff values. In February 2023, a search of PubMed, EMBASE, and Cochrane Library databases was conducted to identify studies comparing EBCs in preschool children with wheezing who continued to wheeze later in life and those who did not. Included observational studies focused on children aged <6 years with a wheezing disorder, assessment of their EBCs, and subsequent asthma status. No language or publication date restrictions were applied. Among the initial 3394 studies screened, 10 were included in the final analysis, involving 1225 patients. The data from these studies demonstrated that high EBC in preschool children with wheezing is associated with future asthma development, with odds ratios of 1.90 (95% CI: 0.45-7.98, p = .38), 2.87 (95% CI: 1.38-5.95, p < .05), and 3.38 (95% CI: 1.72-6.64, p < .05) for cutoff values in the <300, 300-449, and ≥450 cells/μL ranges, respectively. Defining a specific cutoff point for an elevated EBC lacks consistency, but children with EBC >300 cells/μL are at increased risk of asthma. However, further research is needed due to the limitations of the included studies. Future investigations are necessary to fully elucidate the discussed association.

Limited clinical role of blood eosinophil levels in early life atopic disease: A mother-child cohort study

BACKGROUND

Blood eosinophil count is a well-established biomarker of atopic diseases in older children and adults. However, its predictive role for atopic diseases in preschool children is not well established.

OBJECTIVE

To investigate the association between blood eosinophil count in children and development of atopic diseases up to age 6 years.

METHODS

We investigated blood eosinophil count at age 18 months and 6 years in relation to recurrent wheeze/asthma, atopic dermatitis, allergic rhinitis, and allergic sensitization during the first 6 years of life in the two Copenhagen Prospective Studies on Asthma in Childhood cohorts (n = 1111). Blood eosinophil count was investigated in association with remission of existing atopic disease, current atopic disease, and later development of atopic disease.

RESULTS

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis, while blood eosinophil count at age 6 years was associated with increased occurrence of current wheezing/asthma (OR = 1.1; 1.04-1.16, p = .0005), atopic dermatitis (OR = 1.06; 1.01-1.1, p = .02), and allergic rhinitis (OR = 1.11; 1.05-1.18, p = .0002). Blood eosinophil count at 18 months did not predict persistence or development of recurrent wheeze/asthma or atopic dermatitis at age 6 years.

CONCLUSION

Blood eosinophil count at 18 months was not associated with current wheezing/asthma or atopic dermatitis and did not predict persistence or development of disease. This implies a limited clinical role of blood eosinophil levels in early-life atopic disease and questions the clinical value of blood eosinophil counts measured in toddlers as a predictive biomarker for subsequent atopic disease in early childhood.

Early Prediction of Asthma

The clinical manifestations of asthma in children are highly variable, are associated with different molecular and cellular mechanisms, and are characterized by common symptoms that may diversify in frequency and intensity throughout life. It is a disease that generally begins in the first five years of life, and it is essential to promptly identify patients at high risk of developing asthma by using different prediction models. The aim of this review regarding the early prediction of asthma is to summarize predictive factors for the course of asthma, including lung function, allergic comorbidity, and relevant data from the patient's medical history, among other factors. This review also highlights the epigenetic factors that are involved, such as DNA methylation and asthma risk, microRNA expression, and histone modification. The different tools that have been developed in recent years for use in asthma prediction, including machine learning approaches, are presented and compared. In this review, emphasis is placed on molecular mechanisms and biomarkers that can be used as predictors of asthma in children.

Increased fecal human beta-defensin-2 expression in preterm infants is associated with allergic disease development in early childhood

Background

This study aimed to investigate whether fecal human beta-defensins (HBD)-2 and eosinophil cationic protein (ECP) expression in preterm infants are associated with allergic disease development by age 2 years.

Methods

Preterm infants' stool samples were collected at the age of 6 and 12 months postnatally. Information regarding medication exposure histories (antibiotics, antipyretics, probiotics) and physician-diagnosed allergic diseases was obtained using age-specific questionnaires and medical records. We compared the 6-month and 12-month fecal HBD-2 and ECP concentrations between the medication exposure and non-exposure group, respectively, and between children who developed allergic diseases and those who did not by 2 years of age. Univariate and multivariable logistic regression analyses were performed to investigate independent variables related to physician-diagnosed allergic diseases by 2 years of age.

Results

Seventy-four preterm infants (gestational age, 31–36 weeks) were included. Fecal HBD-2 levels were significantly increased at 12 months of age among children who developed allergic diseases compared to those who did not (37.18 ± 11.80 ng/g vs. 8.56 ± 4.33 ng/g, P = 0.011). This association was more apparent among allergic children given antibiotics (50.23 ± 16.15 ng/g vs. 9.75 ± 7.16 ng/g, P = 0.008) or antipyretics (46.12 ± 14.22 ng/g vs. 10.82 ± 6.81 ng/g, P = 0.018) during the first year, whereas among allergic children who were previously not exposed to antibiotics or antipyretics, the differences were not significant. Results of the multivariable logistic regression analysis indicated that HBD-2 concentration in 12-month stools was an independent indicator associated with physician-diagnosed allergic diseases by 2 years of age (adjusted odds ratio: 1.03 [95% confidence interval: 1.00–1.05], P = 0.036). Our data revealed a lack of association between fecal ECP and allergic diseases.

Conclusions

We found that preterm infants who expressed high fecal HBD-2 at 12 months of age were associated with physician-diagnosed allergic diseases by the age of 2 years. Further studies are needed to determine the role of fecal HBD-2 in the development of allergic diseases.

Correlation of PD-1/PD-L1 Signaling Pathway with Treg/Th17 Imbalance from Asthmatic Children

BACKGROUND

The balance between T helper 17 (Th17) and regulatory T cells (Treg) is a new paradigm in asthma pathogenesis, but no therapeutic targets could modulate the Th17/Treg balance specifically for asthma. Since previous studies have shown the programmed cell death-1(PD-1)/PD-ligand 1 (PD-L1) pathway is critical to immune homeostasis in this disease, we hypothesized that the PD-1/PD-L1 pathway might be involved in the regulation of Treg/Th17 imbalance in asthmatic children.

METHODS

The percentage of Treg and Th17 cells and the expression of PD-1 and PD-L1 were detected by flow cytometry in children with asthma and healthy controls. CD4+ T cells were stimulated with Th17 and Treg differentiating factors, and treated with anti-PD-1. Then cells were harvested and measured for Th17 and Treg percentages and Foxp3 and RORγt levels using RT-PCR.

RESULTS

We observed an inverse correlation between the percentages of Treg and Th17 cells, and the expression of PD-1 and PD-L1 in the two subsets also changed in the mild persistent and moderate to severe persistent groups compared with healthy controls. In vitro, administration of anti-PD-1 could decrease Th17 percentages and RORγt mRNA, and increase Treg percentages and Foxp3 mRNA in CD4+ T cells of children with asthma in the mild persistent and moderate to persistent groups. Additionally, the role played by anti-PD-1 in regulating Treg/Th17 balance was further confirmed in an asthmatic mouse model.

CONCLUSION

Alteration of the PD-1/PD-L1 pathway can modulate Treg/Th17 balance in asthmatic children. Treatment with anti-PD-1 posed protective effects on asthma models, providing a novel theoretical target for asthma.

Current and future management of the young child with early onset wheezing

PURPOSE OF REVIEW

In this review, we discuss current thinking in relation to available guidelines for the care of preschool-aged children with recurrent wheezing, while highlighting the gaps in our knowledge and discussing changes that could occur over the next 5 years.

RECENT FINDINGS

The Asthma Predictive Index as well as allergen-specific IgE, peripheral eosinophil count and exhaled nitric oxide are perhaps underutilized sources of information that can assist in predicting progression to asthma and response to therapies. Inhaled corticosteroids and leukotriene receptor antagonists decrease impairment and exacerbation frequency in wheezing children but are not disease modifying. Macrolides may be useful during acute wheezing episodes for preventing progression to more severe symptoms. Monoclonal antibodies targeting IgE and TH2 cytokines have been successful in trials of adults and older children with asthma, but trials in younger children are needed.

SUMMARY

Establishing the phenotype and endotype of young wheezing children can be useful for prognostication of future asthma risk as well as for selection of the most appropriate treatment. Primary asthma prevention strategies are needed during the critical developmental window in early life prior to the onset of irrecoverable loss of lung function.

The heterogeneity of viral bronchiolitis: A lack of universal consensus definitions

Viral bronchiolitis is one of the most common hospital presentations in infancy and as such represents a major healthcare burden worldwide. However despite this, there are currently no effective targeted therapies nor can those infants at highest risk for developing severe disease or subsequent respiratory morbidity be predicted on initial hospital presentation. Current definitions of bronchiolitis in the published literature vary significantly in terms of the age range at presentation, specific clinical symptoms, causative virus, and the inclusion or exclusion of infants with previous presentations and/or various comorbidities. In this review, we highlight how this heterogeneity among definitions contributes to a lack of clarity on this condition and its likely multiple endotypes. We argue that without a new universal consensus definition or sets of definitions, progress into bronchiolitis will continue to be stalled.

Interleukin-33 in children with asthma: A systematic review and meta-analysis

BACKGROUND

Previous studies have shown that serum interleukin 33 serving as an "alarmin" is increased in children with asthma. The objective of this study was to assess the validity of serum IL33 test for early diagnosis of childhood asthma.

METHODS

A literature search was performed in June 2016 using PubMed, Embase, the Cochrane Library and other Chinese Medical Databases to identify studies. The search terms used were "cytokine", "interleukin-33", "asthma" and "children". The meta-analysis was performed using Review Manager 5.3 software. Random-effects model was used to estimate the standardized mean differences (SMDs) with 95% confidence intervals (CIs).

RESULTS

A total of eight studies were included into this meta-analysis, involving 330 asthmatic children and 248 healthy children. The meta-analysis results revealed that the serum IL33 level was higher in asthmatic children compared to that in healthy children (SMD=1.29, 95%CI=0.53-2.05, P=0.0009), with significant heterogeneity across studies (I²=94% and P<0.00001).

CONCLUSIONS

The meta-analysis showed that serum IL33 is a helpful biomarker for early diagnosis of childhood asthma. However, owing to lack of enough data, the increased serum concentration of IL33 cannot be an indicator for the asthma severity.

Clinical and Virus Surveillance After the First Wheezing Episode: Special Reference to Rhinovirus A and C Species

BACKGROUND

Susceptibility to rhinovirus (RV)-induced early wheezing episode has been recognized as an important risk factor for asthma, but the data on different RV species are limited. Our aim was to investigate the risk for recurrences in first-time wheezing children with special focus on RV species.

METHODS

First-time wheezing children (88 inpatients and 23 outpatients) were prospectively followed at 2-week, 2-month and 12-month time-points, and at first recurrence within 12 months. The respiratory virus etiology was analyzed using polymerase chain reaction. RV-positive samples were sequenced. The primary outcomes were time to a new physician-confirmed wheezing episode, time to a new RV-induced wheezing episode and time to the initiation of regular controller medication for asthma symptoms.

RESULTS

The median age of the children was 12 months (standard deviation, 6.0), 67% were males and 23% were sensitized. RV dominated in symptomatic and asymptomatic infections. Different RV strains were observed in 97% (67/69) of consecutive samples during follow-up. First-time wheezing children with RV-C and RV-A had an increased risk for a new physician-confirmed wheezing episode and a new RV-associated wheezing episode than non-RV group (all P < 0.05). Also, the risk for the initiation of regular controller medication was increased in RV-A and RV-C groups when compared with non-RV group (both P < 0.05).

CONCLUSIONS

RV causes reinfections with different strains in small children after the first wheezing episode. Both RV-A and RV-C affected children have an increased risk for recurrence, especially RV associated, and initiation of regular controller medication than those with other viruses.

Factors predicting persistence of early wheezing through childhood and adolescence: a systematic review of the literature

Background

For the early identification of persistent asthma symptoms among young children with recurrent wheezing, it would be helpful to identify all available studies that have identified at least one factor for predicting the persistence of early wheezing. The objective of the present study was to perform a systematic review of all studies that have identified factors that predict the persistence of symptoms among young patients with recurring wheezing.

Methods

A systematic review of relevant studies was conducted through searching in MEDLINE, EMBASE, CINHAL, and SCOPUS databases up to June 2016. Studies that identified predictors of persistence of wheezing illness among young children with recurrent wheezing were retrieved. Two independent reviewers screened the literature and extracted relevant data.

Results

The literature search returned 649 references, 619 of which were excluded due to their irrelevance. Five additional studies were identified from reference lists, and 35 studies were finally included in the review. Among all the identified predictors, the most frequently identified ones were the following: family asthma or atopy; personal history of atopic diseases; allergic sensitization early in life; and frequency, clinical pattern, or severity of wheezing/symptoms.

Conclusion

Parental asthma (especially maternal), parental allergy, eczema, allergic rhinitis, persistent wheezing, wheeze without colds, exercise-induced wheeze, severe wheezing episodes, allergic sensitization (especially polysensitization), eosinophils (blood or eosinophil cationic protein in nasal sample), and fraction of exhaled nitric oxide were risk factors predicting persistence of early wheezing through school age. All of them are included in conventional algorithms, for example, Asthma Predictive Index and its modifications, for predicting future asthma.

Faecal eosinophil cationic protein and serum immunoglobulin E in relation to infant feeding practices

Background To date, the effects of exclusive breastfeeding duration and timing of solid food introduction on allergy prevention are unclear. The aim of this study was to determine the effect of variable feeding practices on intestinal inflammation in infants using faecal eosinophil cationic protein as a surrogate marker and to assess whether faecal eosinophil cationic protein is associated with serum immunoglobulin E. Methods Subjects ( n = 206) were enrolled from the Prediction of Allergies in Taiwanese CHildren (PATCH) birth cohort study. Stool samples were collected at 6 and 12 months for determining eosinophil cationic protein, and blood was collected for determining total and allergen-specific immunoglobulin E at 12 months. We compared these biomarkers between infants with variable exclusive breastfeeding duration and infants introduced to solid foods at various periods. The association between faecal eosinophil cationic protein, total serum immunoglobulin E and specific immunoglobulin E was also analysed. Results Faecal eosinophil cationic protein was significantly higher in exclusively breastfed infants compared with formula-fed infants and infants who were not exclusively breastfed at 6 months of age ( P < 0.05). At 12 months, infants who were introduced to solid foods at 5-6 months had the lowest faecal eosinophil cationic protein compared with those who were introduced at earlier and later periods. There was no significant association between faecal eosinophil cationic protein and serum immunoglobulin E. Conclusion We found that breastfeeding exclusively for >6 months did not reduce serum immunoglobulin E, but rather increased intestinal inflammation. Faecal eosinophil cationic protein was not associated with total serum immunoglobulin E and specific immunoglobulin E and might not be a useful indictor of immunoglobulin E sensitization in infancy.

Blood eosinophils as a marker of likely corticosteroid response in children with preschool wheeze: time for an eosinophil guided clinical trial?

Childhood wheezing is common particularly in children under the age of 6 years and in this age group is generally referred to as preschool wheezing. Particular diagnostic and treatment uncertainties exist in these young children due to the difficulty in obtaining objective evidence of reversible airways narrowing and inflammation. A diagnosis of asthma depends on the presence of relevant clinical signs and symptoms and the demonstration of reversible airways narrowing on lung function testing, which is difficult to perform in young children. Few treatments are available and inhaled corticosteroids are the recommended preventer treatment in most international asthma guidelines. There is, however, considerable controversy about its effectiveness in children with preschool wheeze and a corticosteroid responder phenotype has not been established. These diagnostic and treatment uncertainties in conjunction with the knowledge of corticosteroid side effects, in particular the reduction of growth velocity, have resulted in a variable approach to inhaled corticosteroid prescribing by medical practitioners and a reluctance in carers to regularly administer the treatment. Identifying children who are likely responders to corticosteroid therapy would be a major benefit in the management of this condition. Eosinophils have emerged as a promising biomarker of corticosteroid responsive airways disease, and evaluation of this biomarker in sputum has successfully been employed to direct management in adults with asthma. Obtaining sputum from young children is time consuming and difficult, and it is hard to justify more invasive procedures such as a bronchoscopy in young children routinely. Recently, in children, interest has shifted to assessing the value of less invasive biomarkers of likely corticosteroid response and the biomarker 'blood eosinophils' has emerged as an attractive candidate. The aim of this review was to summarize the evidence for blood eosinophils as a predictive biomarker for corticosteroid responsive disease with a particular focus on the difficult area of preschool wheeze.

Biomarkers to predict asthma in wheezing preschool children

Wheezing in preschool children is a very common symptom. An adequate prediction of asthma in these children is difficult and cannot be reliably assessed with conventional clinical tools. The study of potential predictive biomarkers in various media, ranging from invasive sampling (e.g. bronchoscopy) to non-invasive sampling (lung function testing and exhaled breath analysis), was comprehensively reviewed. The evolution in biomarker discovery has resulted in an 'omics' approach, in which hundreds of biomarkers in the field of genomics, proteomics, metabolomics, and 'breath-omics' can be simultaneously studied. First, results on gene expression and exhaled breath profiles in predicting an early asthma diagnosis are promising. However, many hurdles need to be overcome before clinical implementation is possible. To reliably predict asthma in a wheezing child, probably a holistic approach is needed, combining clinical information with blood sampling, lung function tests, and potentially exhaled breath analysis. The further development of predictive, non-invasive biomarkers may eventually improve an early asthma diagnosis in wheezing preschool children and assist clinicians in early treatment decision-making.

Low eosinophils during bronchiolitis in infancy are associated with lower risk of adulthood asthma

BACKGROUND

Infant bronchiolitis may be the first manifestation of asthma.

AIM

To evaluate the association of early-childhood risk or protective factors for asthma and lung function reduction in adults 30 years after bronchiolitis in infancy.

METHODS

Forty-seven former bronchiolitis patients attended the clinical study at the median age of 29.5 years, including doctoral examination and measurement of post-bronchodilator lung function with flow-volume spirometry. Data on early-life risk factors including blood eosinophil counts on admission for bronchiolitis and on convalescence 4-6 weeks after bronchiolitis were available.

RESULTS

Low blood eosinophil count <0.25 × 10E9/l on admission for bronchiolitis was a significant protective factor and high blood eosinophil count >0.45 × 10E9/l on convalescence was a significant risk factor for asthma in adulthood independently from atopic status in infancy. Parental asthma and high blood eosinophil count >0.45 × 10E9/l during bronchiolitis were significant risk factors for irreversible airway obstruction (FEV1/FVC ratio below the 5th percentile lower limit of normality after bronchodilation).

CONCLUSION

Our adjusted analyses confirmed that eosinopenia during infant bronchiolitis predicted low asthma risk and eosinophilia outside infection predicted high asthma risk up to the age of 28-31 years. Parental asthma and eosinophilia during bronchiolitis were recognized as risk factors for irreversible airway obstruction.

Inflammatory activity at school age in very low birth weight bronchopulmonary dysplasia survivors

OBJECTIVE

Airway inflammation is involved in the pathogenesis of bronchopulmonary dysplasia (BPD). The aim of the study was to evaluate the inflammatory activity in plasma and exhaled air in very low birth weight (VLBW) BPD survivors at school age.

METHODS

Twenty-one 6-14-year-old former VLBW (birth weight ≤1,500 g) children with severe radiographic BPD (radBPD), 19 without radBPD (nonBPD group) and 19 non-asthmatic term controls underwent measurement of eosinophil cationic protein, IL-6, IL-8, adiponectin, adipsin, leptin, and resistin in plasma, leukotriene B4 and 8-isoprostane in exhaled breath condensate, and NO in exhaled breath. Background data were obtained from patient records, clinical examination and parental questionnaire. Both univariate and multivariate models were applied in the statistical analysis.

RESULTS

There were no significant differences between the groups in any of the inflammatory markers measured. Five (25%) radBPD and 2 (11%) nonBPD children reported asthma (P = 0.058). In logistic regression analysis, exposure to chorioamnionitis was associated with low IL-8 (OR 29.0, 95% CI 3.27-258) and postnatal corticosteroid therapy with high adiponectin (OR 32.0, 95% CI 1.29-793). High body mass index standard deviation score (BMI-SDS) was associated with high plasma adipsin (OR 2.47, 95% CI 1.07-5.75) and leptin (OR 5.76, 95%CI 1.83-18.2) levels.

CONCLUSIONS

The inflammatory activity seems to decrease by school age in VLBW BPD survivors. Chorioamnionitis and postnatal corticosteroid treatment may modulate the inflammatory responsiveness in VLBW subjects even up to school age. The respiratory outcome in VLBW infants might be improved by preventing excessive weight gain.

Blood eosinophil counts during bronchiolitis are related to bronchial hyper-responsiveness and lung function in early adolescence

AIM

To assess whether inflammatory markers measured in urine and blood during acute bronchiolitis in infancy were associated with asthma, lung function, bronchial hyper-responsiveness (BHR) and atopy at 11 years of age.

METHODS

We included 105 children hospitalised for bronchiolitis during their first year of life. At hospitalisation, urinary (U-) eosinophil protein X, U-leukotriene E4 , U-prostaglandin 9α, 11β-PGF2 and blood eosinophil counts were measured. Ninety-five children (90%) were available for follow-up at 11 years of age.

RESULTS

At follow-up, higher blood eosinophil counts obtained during bronchiolitis were observed in the group with asthma than in the group without asthma (median 0.27 versus 0.09 × 10(9) /L, respectively, p = 0.048). By regression analyses, blood eosinophil counts during the acute bronchiolitis were positively associated with BHR (p = 0.006) and negatively associated with forced expiratory volume in first second (p = 0.025) at 11 years of age. None of the other inflammatory markers were associated with asthma, lung function, BHR or atopy at 11 years of age.

CONCLUSION

Eosinophil inflammation during bronchiolitis may have a long-term impact on lung function and airway responsiveness. The associations could be related to virus-host interactions during bronchiolitis or to predisposed children.

Asthma: a chronic infectious disease?

There are increasing data to support the "hygiene" and "microbiota" hypotheses of a protective role of infections in modulating the risk of subsequent development of asthma. There is less evidence that respiratory infections can actually cause the development of asthma. There is some evidence that rhinovirus respiratory infections are associated with the development of asthma, particularly in childhood, whereas these infections in later life seem to have a weaker association with the development of asthma. The role of bacterial infections in chronic asthma remains unclear. This article reviews the available evidence indicating that asthma may be considered as a chronic infectious disease.