Comparative characterization of bronchial and nasal mucus reveals key determinants of influenza A virus inhibition

Differentiated primary human respiratory epithelial cells grown at air-liquid interface have become a widely used cell culture model of the human conducting airways. These cultures contain secretory cells such as goblet and club cells, which produce and secrete mucus. Here, we characterize the composition of mucus harvested from airway cultures of nasal and bronchial origin. We find that despite inter-donor variability, the salt, sugar, lipid, and protein content and composition are very similar between nasal and bronchial mucus. However, subtle differences in the abundance of individual components in nasal versus bronchial mucus can influence its antimicrobial properties. The ability of mucus to neutralize influenza A virus varies with the anatomical origin of the airway cultures and correlates with the abundance of triglycerides and specific sialylated glycoproteins and glycolipids.IMPORTANCERespiratory mucus plays an important role during the transmission and infection process of microbes in the human respiratory tract. In the case of influenza A virus, the mucus stabilizes the virions in infectious respiratory particles and droplets but hampers virus particles before they reach the respiratory epithelium through its physicochemical properties and the presence of sialylated decoy receptors. However, it is thus far not well understood which components of mucus mediate protection and inhibition. Our study now provides a comprehensive analysis of bronchial and nasal mucus from primary human airway cultures that can be used as a resource for future experimental designs and interpretations.