Background: Azithromycin (AZM) is effective in reducing asthma exacerbations and augments in vitro epithelial anti-viral immunity. However, the clinical data in eosinophilic (eos) and non-eosinophilic (non-eos) asthma phenotypes are conflicting.

Objectives: To compare the effect of in vitro AZM treatment on IFN? response in rhinovirus (RV1B) infected bronchial epithelial cells (BECs) of eos and non-eos asthma patients.

Methods: Twenty asthma patients, 10 eos (5 atopic) and 10 non-eos (5 atopic), underwent bronchoscopy to harvest BECs. BECs were pre-treated in vitro with and without AZM 24h before infection with RV1B. Gene expression levels of IFN? was measured 24h after infection by real-time PCR and compared across asthma phenotypes using Mann-Whitney and Wilcoxon tests.

Results: AZM increased RV1B-induced IFN? expression in non-eos asthma (p=0.002, fig. 1a) and there was a trend in eos asthma (p=0.06). This response was similar in eos and non-eos groups (p=0.15). Interestingly, within eos asthma patients, non-atopic asthmatics had a better response to AZM induced IFN? augmentation compared to atopic asthmatics (p=0.03). Whereas in non-eos asthma patients, no significant difference was found between atopic and non-atopic patients (p=0.88).

Conclusions: In vitro AZM treatment augments BEC antiviral response to RV1B in both eosinophilic and non-eosinophilic asthma phenotypes.