Otitis media with effusion in an allergic animal model: A functional and morphological study

Allergy is considered as one of important etiologic factor of otitis media with effusion (OME). In present study, we evaluated the causal effect of allergy on OME in an animal model, and investigated the secondary effect of bacterial infection.

Allergy and control animals were subdivided into groups with and without intratympanic injection of lipopolysaccharide (IT-LPS). Allergic otitis media was induced via intraperitoneal ovo-albumin injection with intranasal challenge. We assessed the occurrence of OME in allergic animals and the effect of IT-LPS on allergic otitis media. We also investigated the Th1 and Th2 responses in the middle-ear mucosa. Hearing of the animals was measured by ABR and DPOAE.

OME was observed in 75% of the allergic animals. After IT-LPS, 100% of the control and allergy groups showed otitis media. Light microscopy revealed that the middle-ear mucosa of animals of both groups also was significantly increased after IT-LPS, and the Th1 response (IL-2 and IFN-γ) and Th2 response (IL-5 and IL-13) cytokines were expressed at higher levels in the allergy group with IT-LPS than in control group with IT-LPS. Hearing tests between the allergy and control group with IT-LPS did not reveal any differences.

Our findings may be direct evidence of an allergic causal effect on OME. Th2 response cytokines were strongly expressed in allergic OME, and the inflammatory reaction to LPS was more intense in the allergic group, which indicates that otitis media related to allergy can be severely aggravated by an inflammatory reaction to bacterial infection.