Niche- and gender-dependent immune reactions in relation to the microbiota profile in pediatric patients with otitis media with effusion

Abstract

Otitis media with effusion (OME) is a common inflammatory disease, primarily affecting children. OME is defined as a chronic low-grade inflammation of the middle ear (ME), without any signs of infection and with effusion persisting in the ME for more than three months. The precise pathogenesis is, however, not fully understood. Here, we comprehensively characterized and compared the host immune responses (inflammatory cells and mediators) and the overall microbial community composition (microbiota) present in matched middle ear effusion samples (MEE), external ear canal lavages, and nasopharynx (NPH) samples from children with OME. Female patients had significantly increased percentages of T lymphocytes and higher levels of a wide array of inflammatory mediators in their MEEs compared to male patients, which was unrelated to microbiota composition. The relative abundances of identified microorganisms were strongly associated with their niche of origin. Furthermore, specific inflammatory mediators were highly correlated with certain bacterial species. Interestingly, some organisms displayed a niche-driven inflammation pattern, where presence of Haemophilus spp and Corynebacterium propinquum in MEEs was accompanied by pro-inflammatory mediators, whereas their presence in NPH was accompanied by anti-inflammatory mediators. For Turicella and Alloiococcus we found exactly the opposite results, i.e., an anti-inflammatory profile when present in MEEs, whereas their presence in the NPH was accompanied by a pro-inflammatory profile. Altogether, our results indicate that immune responses in children with OME are highly niche- and microbiota-driven, but gender-based differences were also observed, providing novel insight into potential pathogenic mechanisms behind OME