Effects of allergic rhinitis on the progression and recovery of acute otitis media in a mouse model

Objectives: The objective of this study was to evaluate the effects of allergic rhinitis (AR) on the development, progression, and recovery of acute otitis media (OM) in an animal model and investigate the secondary effects of bacterial infection. Methods: BALB/c mice were divided into four groups: AR + OM, AR, OM, and control groups. AR + OM and AR groups were sensitized with ovalbumin (OVA) and alum and then challenged intranasally with OVA. Phosphate-buffered saline (PBS) was administered to the OM and control groups the same number of times. After AR induction, OM was induced by surgical inoculation of non-typeable Haemophilus influenza (NTHi) into the middle ear (ME) cavity of the mice in the AR + OM and OM groups. PBS was injected into the bulla in the AR and control groups. Each group was subdivided into sets of six mice, one for each of the four time points (0, 2, 7, and 10 days post-bacterial inoculation), at which point the mice were euthanized and ME and nasal cavity mucosa were obtained and evaluated. The occurrence of OM and the ME mucosa thickness were evaluated and compared among the four groups. Tissue expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) in infected ME mucosa was assessed by immunohistochemical staining. We also investigated IgE, IL-4, and IL-5 in the nasal mucosa. Results: Most of the ears showed OM on post-inoculation day 2 in both AR + OM and OM groups. In the AR + OM group, 58.3% of ears still had OM on post-inoculation day 10, while only 16.7% of the OM group had OM. The ME mucosa of all groups increased, and the AR + OM group exhibited the thickest mucosa. The OM group showed peak thickness on post-inoculation day 2 and then decreased, whereas the ME mucosa thickness of the AR + OM group continued to increase to day 7. In the OM group, the expression of IL-1β, IL-6, and TNF-α in the ME also increased significantly, peaking on post-inoculation day 2, and then gradually decreased. In the AR + OM group, the expression of these proteins increased until day 7 and then decreased. The IgE and Th2 response (IL-4 and IL-5) cytokines were expressed at higher levels in the AR + OM and AR groups than in the OM and control groups. Conclusion: The inflammatory reaction to NTHi was more intense and lasted longer in the allergic group, which indicates that AR affects the progression and subsequent recovery of acute bacterial OM.