Asthma development is associated with low mucosal IL‐10 during viral infections in early life.

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]