House dust mite sensitization and exposure affects bronchial epithelial anti-microbial response to viral stimuli in patients with asthma

Introduction Allergen exposure worsens viral-triggered asthma exacerbations and could predispose the host to secondary bacterial infections. We have previously demonstrated that exposure to house dust mite (HDM) reduced TLR-3-induced IFN-beta in human bronchial epithelial cells (HBECs) from healthy donors. We hypothesize that HDM sensitization in different ways may be involved in both viral and bacterial resistance of HBECs in asthma. In this study, the role of HDM sensitization and effects of HDM exposure on viral stimulus-challenged HBECs from asthmatic donors have been explored with regard to expression and release of molecules involved in anti-viral and anti-bacterial responses, respectively. Methods HBECs from HDM-sensitized (HDM+) and unsensitized (HDM-) patients with asthma were used. HBECs were exposed to HDM or heat inactivated (hi)-HDM (20 mu g/ml) for 24 h prior to stimulation with the viral infection mimic, Poly(I:C), for 3 or 24 h. Samples were analyzed with ELISA and RT-qPCR for beta-defensin-2, IFN-beta, TSLP, and neutrophil-recruiting mediators: IL-8 and TNF-alpha NF kappa B signaling proteins p105, p65, and I kappa B-alpha were analyzed by Western blot. Results Poly(I:C)-induced IFN-beta expression was reduced in HBECs from HDM + compared to HDM- patients (p = 0.05). In vitro exposure of HBECs to HDM furthermore reduced anti-microbial responses to Poly(I:C) including beta-defensin-2, IL-8, and TNF-alpha along with reduced NF kappa B activity. This was observed in HBECs from asthma patients sensitized to HDM, as well as in non-sensitized patients. By contrast, Poly (I:C)-induced release of TSLP, a driver of T2 inflammation, was not reduced with exposure to HDM. Conclusion Using HBECs challenged with viral infection mimic, Poly(I:C), we demonstrated that allergic sensitization to HDM was associated with impaired anti-viral immunity and that HDM exposure reduced anti-viral and anti-bacterial defense molecules, but not TSLP, across non-allergic as well as allergic asthma. These data suggest a role of HDM in the pathogenesis of asthma exacerbations evoked by viral infections including sequential viral-bacterial and viral-viral infections.

Automated summary

This study found that exposure to house dust mite (HDM) affected the anti-viral and anti-bacterial responses in airway epithelial cells of allergic asthma patients, potentially leading to asthma exacerbations. However, HDM exposure did not affect the release of TSLP, a driver of T2 inflammation.