Fetal Eosinophils Get on the Nerves of Airways. Early Origins of Bronchoconstriction

Cord blood granulocyte levels are associated with severe bronchiolitis in the first year of life

Objectives

Bronchiolitis is a leading cause of infant hospitalisation in the first year of life, and it preferentially affects infants born to mothers with asthma. Here, we evaluate cord blood granulocytes in infants born to mothers with asthma participating in the Breathing for Life Trial (BLT), to investigate early life determinants of bronchiolitis hospitalisation within the first year of life.

Methods

Cord blood from 89 participants was collected into EDTA tubes and processed within 6 h of birth. Cells were stained in whole cord blood for eosinophils (CD45+, CD193+, CD16-), and neutrophils (CD45+, CD193-, CD16+). Medical records were reviewed for bronchiolitis hospitalisation in the first 12 months of life. Statistical analyses were conducted using Stata IC16.1.

Results

Logistic regression adjusted for caesarean section, gestational age, maternal smoking during pregnancy, foetal heart deceleration during labour, and season of birth revealed an association between cord blood eosinophil levels and bronchiolitis hospitalisation in the first 12 months of life with an Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve of 0.943 (aOR = 1.35, P = 0.011). Neutrophils were associated with the risk of bronchiolitis hospitalisation in a univariable logistic regression (OR = 0.93, P = 0.029); however, there was no statistical significance in the adjusted model.

Conclusions

Higher eosinophil numbers in cord blood were associated with bronchiolitis hospitalisation in the first 12 months in a cohort of infants born to asthmatic mothers. This suggests that susceptibility to bronchiolitis in later life is influenced by the immune cell profile prior to viral infection.

Airway Wall Remodeling in Childhood Asthma-A Personalized Perspective from Cell Type-Specific Biology

Airway wall remodeling is a pathology occurring in chronic inflammatory lung diseases including asthma, chronic obstructive pulmonary disease, and fibrosis. In 2017, the American Thoracic Society released a research statement highlighting the gaps in knowledge and understanding of airway wall remodeling. The four major challenges addressed in this statement were: (i) the lack of consensus to define “airway wall remodeling” in different diseases, (ii) methodologic limitations and inappropriate models, (iii) the lack of anti-remodeling therapies, and (iv) the difficulty to define endpoints and outcomes in relevant studies. This review focuses on the importance of cell-cell interaction, especially the bronchial epithelium, in asthma-associated airway wall remodeling. The pathology of “airway wall remodeling” summarizes all structural changes of the airway wall without differentiating between different pheno- or endo-types of asthma. Indicators of airway wall remodeling have been reported in childhood asthma in the absence of any sign of inflammation; thus, the initiation event remains unknown. Recent studies have implied that the interaction between the epithelium with immune cells and sub-epithelial mesenchymal cells is modified in asthma by a yet unknown epigenetic mechanism during early childhood.

Cord blood group 2 innate lymphoid cells are associated with lung function at 6 weeks of age

Objective

Offspring born to mothers with asthma in pregnancy are known to have lower lung function which tracks with age. Human group 2 innate lymphoid cells (ILC2) accumulate in foetal lungs, at 10‐fold higher levels compared to adult lungs. However, there are no data on foetal ILC2 numbers and the association with respiratory health outcomes such as lung function in early life. We aimed to investigate cord blood immune cell populations from babies born to mothers with asthma in pregnancy.

Methods

Cord blood from babies born to asthmatic mothers was collected, and cells were stained in whole cord blood. Analyses were done using traditional gating approaches and computational methodologies (t‐distributed stochastic neighbour embedding and PhenoGraph algorithms). At 6 weeks of age, the time to peak tidal expiratory flow as a percentage of total expiratory flow time (tPTEF/tE%) was determined as well as Lung Clearance Index (LCI), during quiet natural sleep.

Results

Of 110 eligible infants (March 2017 to November 2019), 91 were successfully immunophenotyped (82.7%). Lung function was attempted in 61 infants (67.0%), and 43 of those infants (70.5% of attempted) had technically acceptable tPTEF/tE% measurements. Thirty‐four infants (55.7% of attempted) had acceptable LCI measurements. Foetal ILC2 numbers with increased expression of chemoattractant receptor‐homologous molecule (CRTh2), characterised by two distinct analysis methodologies, were associated with poorer infant lung function at 6 weeks of age.”

Conclusion

Foetal immune responses may be a surrogate variable for or directly influence lung function outcomes in early life.

Maternal asthma is associated with reduced lung function in male infants in a combined analysis of the BLT and BILD cohorts

RATIONALE

Asthma in pregnancy is associated with respiratory diseases in the offspring.

OBJECTIVE

To investigate if maternal asthma is associated with lung function in early life.

METHODS

Data on lung function measured at 5-6 weeks of age were combined from two large birth cohorts: the Bern Infant Lung Development (BILD) and the Australian Breathing for Life Trial (BLT) birth cohorts conducted at three study sites (Bern, Switzerland; Newcastle and Sydney, Australia). The main outcome variable was time to reach peak tidal expiratory flow as a percentage of total expiratory time(tPTEF:tE%). Bayesian linear hierarchical regression analyses controlling for study site as random effect were performed to estimate the effect of maternal asthma on the main outcome, adjusting for sex, birth order, breast feeding, weight gain and gestational age. In separate adjusted Bayesian models an interaction between maternal asthma and sex was investigated by including an interaction term.

MEASUREMENTS AND MAIN RESULTS

All 406 BLT infants were born to mothers with asthma in pregnancy, while 193 of the 213 (91%) BILD infants were born to mothers without asthma. A significant interaction between maternal asthma and male sex was negatively associated with tPTEF:tE% (intercept 37.5; estimate: -3.5; 95% credible interval -6.8 to -0.1). Comparing the model posterior probabilities provided decisive evidence in favour of an interaction between maternal asthma and male sex (Bayes factor 33.5).

CONCLUSIONS

Maternal asthma is associated with lower lung function in male babies, which may have lifelong implications on their lung function trajectories and future risk of wheezing and asthma.