Background. Influenza virus triggers severe exacerbations of asthma for which no adequate treatment is available. It is known that IL-33 levels correlate with exacerbation severity, but its role in the immune-pathogenesis of exacerbations has remained elusive. Objective. We hypothesized that IL-33 is necessary to drive asthma exacerbations. We intervened with the IL-33 cascade and sought to dissect its role, also in synergy with TSLP, in airway inflammation, anti-viral activity and lung function. We aimed to unveil the major source of IL-33 in the airways and IL-33-dependent mechanisms that underlie severe asthma exacerbation. Methods: Mild asthmatic patients were experimentally infected with rhinovirus. Mice were chronically exposed to house dust mite (HDM) extract and then infected with influenza to resemble key features of exacerbations in humans. Interventions included anti-IL-33-receptor ST2 and/or anti-TSLP. Results. We identified bronchial ciliated cells and Type-II alveolar cells as a major local source of IL-33 during virus-driven exacerbation in humans and mice, respectively. By blocking ST2 we demonstrated that IL-33 and not TSLP was necessary to drive exacerbations. IL-33 enhanced AHR and airway inflammation by suppressing innate and adaptive anti-viral responses and by instructing epithelial cells and dendritic cells (DCs) of HDM-sensitized mice to dampen IFN-β expression and prevent the Th1-promoting DCs phenotype. IL-33 also boosted luminal NETosis and halted cytolytic anti-viral activities, but did not affect the Th2-response. Conclusion: Interventions targeting the IL-33/ST2 axis could prove an effective acute, shortterm therapy for virus-induced asthma exacerbation.

Background The temporal in vivo response of epithelial cells to a viral challenge and its association with viral clearance and clinical outcomes has been largely unexplored in asthma. Objective To determine gene expression profiles over time in nasal epithelial cells (NECs) challenged in vivo with rhinovirus‐16 (RV16) and compare to nasal symptoms and viral clearance. Methods Patients with stable mild to moderate asthma (n = 20) were challenged intranasally with RV16. Nasal brush samples for RNA sequencing were taken 7 days prior to infection and 3, 6 and 14 days post‐infection, and blood samples 4 days prior to infection and day 6 post‐infection. Viral load was measured in nasal lavage fluid at day 3, 6 and 14. Results Top differentially (>2.5‐fold increase) expressed gene sets in NECs post‐RV16 at days 3 and 6, compared with baseline, were interferon alpha and gamma response genes. Patients clearing the virus within 6 days (early resolvers) had a significantly increased interferon response at day 6, whereas those having cleared the virus by day 14 (late resolvers) had significantly increased responses at day 3, 6 and 14. Interestingly, patients not having cleared the virus by day 14 (non‐resolvers) had no enhanced interferon responses at any of these days. The daily Cold Symptom Scores (CSS) peaked at days 3 to 5 and correlated positively with interferon response genes at day 3 (R = 0.48), but not at other time‐points. Interferon response genes were also enhanced in blood at day 6 after RV16 challenge. Conclusion and Clinical Relevance This study shows that viral load and clearance varies markedly over time in mild to moderate asthma patients exposed to a fixed RV16 dose. The host's nasal interferon response to RV16 at day 3 is associated with upper respiratory tract symptoms. The temporal interferon response in nasal epithelium associates with viral clearance in the nasal compartment.

Neutrophilic inflammation in asthma is associated with interleukin (IL)-17A, corticosteroid-insensitivity and bronchodilator-induced forced expiratory volume in 1 s (FEV1) reversibility. IL-17A synergises with tumour necrosis factor (TNF)-α in the production of the neutrophil chemokine CXCL-8 by primary bronchial epithelial cells (PBECs).We hypothesised that local neutrophilic inflammation in asthma correlates with IL-17A and TNF-α-induced CXCL-8 production by PBECs from asthma patients.PBECs from most asthma patients displayed an exaggerated CXCL-8 production in response to TNF-α and IL-17A, but not to TNF-α alone, and which was also insensitive to corticosteroids. This hyperresponsiveness of PBECs strongly correlated with CXCL-8 levels and neutrophil numbers in bronchoalveolar lavage from the corresponding patients, but not with that of eosinophils. In addition, this hyperresponsiveness also correlated with bronchodilator-induced FEV1 % reversibility. At the molecular level, epithelial hyperresponsiveness was associated with failure of the translational repressor T-cell internal antigen-1 related protein (TiAR) to translocate to the cytoplasm to halt CXCL-8 production, as confirmed by TiAR knockdown. This is in line with the finding that hyperresponsive PBECs also produced enhanced levels of other inflammatory mediators.Hyperresponsive PBECs in asthma patients may underlie neutrophilic and corticosteroid-insensitive inflammation and a reduced FEV1, irrespective of eosinophilic inflammation. Normalising cytoplasmic translocation of TiAR is a potential therapeutic target in neutrophilic, corticosteroid-insensitive asthma.