Preventive effects of oral tolerance on allergic inflammation and airway remodeling in a murine model

Background: Oral tolerance (OT) is considered as a preventive and therapeutic strategy for treating asthma and allergic rhinitis (AR). We investigated the preventive effects of OT on allergic inflammation and remodeling in the upper and lower airways in a mouse model of allergy. Methods: BALB/c mice were divided into four groups: control, allergy, low-dose OT, and high-dose OT. To induce OT, mice were fed ovalbumin (OVA) before sensitization with OVA/Al(OH)3 at a dose of 1 mg for 6 days in low-dose OT group and a single dose of 25 mg in high-dose OT group. After sensitization followed by OVA challenge, nasal symptoms, interleukin (IL)-13, interferon (IFN)-gamma, IL-10, and transforming growth factor (TGF) beta-1 levels in nasal lavage (NAL) and bronchoalveolar lavage (BAL) fluids were measured, and OVA-specific IgE, IgG1, and IgG2a levels were measured in the serum. The airway hyperresponsiveness (AHR) was measured by enhanced pause. The goblet cell hyperplasia and the thickness of lamina propria were observed in the upper and lower airways. Results: In the allergy group, the allergic behavior scores, AHR, and OVA-specific IgE, IgG1, and IgG2a levels; inflammatory cells; IFN-gamma levels; and IL-13 levels in NAL/BAL fluids were elevated compared with the control group, low-dose OT group, and high-dose OT group. The allergy group had higher levels of IL-10 and TGF-beta-1 in BAL fluids when compared with the other groups. The goblet cell hyperplasia and the thickness of the lamina propria were attenuated in both OT groups compared with the allergy group. Conclusion: OT may effectively prevent AHR, allergic inflammation, and airway remodeling in the upper and lower airways.