Air-interfaced colonization model suggests a commensal-like interaction of Neisseria meningitidis with the epithelium, which benefit from colonization by Streptococcus mitis.

Neisseria meningitidis is an inhabitant of the nasopharynx, from which it is transmitted from person to person or disseminates in the blood and becomes a harmful pathogen. In this work, we addressed the colonization of the nasopharyngeal niche by focusing on the interplay between meningococci and the mucus that lines the mucosa of the host. Using Calu-3 cells grown in air-interfaced culture, we studied the meningococcal colonization of the mucus and the host response. Our results suggested that N. meningitidis behaved like commensal bacteria in mucus, without interacting with human cells or actively transmigrating through the cell layer. As such, meningococci did not trigger a strong innate immune response from the Calu-3 cells. Finally, we have shown that this model is suitable for studying interaction of N. meningitidis with other bacteria living in the nasopharynx, and that Streptococcus mitis but not Moraxella catarrhalis can promote meningococcal growth in this model.