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Background: Viral infection is a common trigger of severe respiratory illnesses in early life and a risk factor for later asthma development. The mechanism leading to asthma could involve an aberrant airway immune response to viral infections, but this has rarely been studied in a human setting. Objectives: To investigate in situ virus‐specific differences in upper airway immune mediator levels during viral episodes of respiratory illnesses and the association with later asthma. Methods: We included 493 episodes of acute respiratory illnesses in 277 children aged 0–3 years from the COPSAC2010 mother–child cohort. Levels of 18 different immune mediators were assessed in nasal epithelial lining fluid using high‐sensitivity MesoScale Discovery kits and compared between children with and without viral PCR‐identification in nasopharyngeal samples. Finally, we investigated whether the virus‐specific immune response was associated with asthma by age 6 years. Results: Viral detection were associated with upregulation of several Type 1 and regulatory immune mediators, including IFN‐ɣ, TNF‐α, CCL4, CXCL10 and IL‐10 and downregulation of Type 2 and Type 17 immune mediators, including CCL13, and CXCL8 (FDR <0.05). Children developing asthma had decreased levels of IL‐10 (FDR <0.05) during viral episodes compared to children not developing asthma. Conclusion: We described the airway immune mediator profile during viral respiratory illnesses in early life and showed that children developing asthma by age 6 years have a reduced regulatory (IL‐10) immune mediator level. This provides insight into the interplay between early‐life viral infections, airway immunity and asthma development. [ABSTRACT FROM AUTHOR]

Background: High body mass index (BMI) is an established risk factor for asthma, but the underlying mechanisms remain unclear., Objective: To increase understanding of the BMI-asthma relationship by studying the association between genetic predisposition to higher BMI and asthma, infections and other asthma traits during childhood., Methods: Data were obtained from the two ongoing Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts. Polygenic risk scores for adult BMI were calculated for each child. Replication was done in the large-scale register-based Integrative Psychiatric Research (iPSYCH) cohort using data on hospitalisation for asthma and infections., Results: In the COPSAC cohorts (n=974), the adult BMI polygenic risk score was significantly associated with lower respiratory tract infections (incidence rate ratio (IRR) 1.20, 95% CI 1.08-1.33, false discovery rate p-value (pFDR)=0.005) at age 0-3 years and episodes of severe wheeze (IRR 1.30, 95% CI 1.06-1.60, pFDR=0.04) at age 0-6 years. Lower respiratory tract infections partly mediated the association between the adult BMI polygenic risk score and severe wheeze (proportion mediated: 0.59, 95% CI 0.28-2.24, p-value associated with the average causal mediation effect (pACME)=2e -16 ). In contrast, these associations were not mediated through the child's current BMI and the polygenic risk score was not associated with an asthma diagnosis or reduced lung function up to age 18 years. The associations were replicated in iPSYCH (n=114 283), where the adult BMI polygenic risk score significantly increased the risk of hospitalisations for lower respiratory tract infections and wheeze or asthma throughout childhood to age 18 years., Conclusion: Children with genetic predisposition to higher BMI had increased risk of lower respiratory tract infections and severe wheeze, independent of the child's current BMI. These results shed further light on the complex relationship between body mass BMI and asthma., Competing Interests: Conflict of interest: The authors have no potential conflicts of interest to disclose., (Copyright ©The authors 2024. For reproduction rights and permissions contact permissions@ersnet.org.)