Non-typeable Haemophilus influenzae infection of ciliated epithelium from healthy and chronic obstructive pulmonary disease donors

Background: Non-typeable Haemophilus influenzae (NTHi) is strongly associated with exacerbation of Chronic Obstructive Pulmonary Disease (COPD). Little is known about initial NTHi-host interactions and how this leads to colonisation. Therefore, we investigated early NTHi interaction with respiratory epithelium in COPD. Methods: Primary airway epithelial cells (healthy and COPD) grown at air-liquid interface were studied at day 7 (prior to ciliogenesis) and day 28 (ciliated), with the proportion of ciliated cells quantified by flow cytometry. NTHi interaction with cultures was observed by high-speed video microscopy, live confocal and scanning electron microscopy for 24 hours. NTHi invasion was quantified by gentamicin killing assay and image cytometry. Results: Flow cytometry confirmed absence of cilia at day 7 and a ciliated phenotype at day 28, with more ciliated cells per well in healthy cultures (4.1±1.9x104) compared to COPD (1.5±1.5x104)(p Conclusion: NTHi rapidly binds to motile cilia, forming long bacterial chains and biofilm. Preferential invasion of non-ciliated epithelium suggests it may occur more often in COPD where, in vivo ciliation is poor.