MicroRNA-155 is a critical regulator of regulatory T cells in OM-85 Broncho-Vaxom treated experimental models of allergic rhinitis

Background: Bacterial lysates could alleviate the clinical symptoms of allergic rhinitis (AR) and decrease the recurrent rate of AR through regulation of regulatory T cell (Treg) cells. However, the molecular regulatory mechanisms of bacterial lysates to Treg are still unclear. Objective: We aimed to investigate the importance of microRNA-155 (miR-155) to Treg cells function in OM-85 Broncho-Vaxom (OM-85 BV) treated experimental mouse models of AR. Methods: AR mouse models were established and treated by intranasal administration of OM-85 BV to investigate the role of bacteria lysate for Treg cell function. The proliferation of Treg cells in peripheral blood was examined. The mRNA levels of IL-10, transforming growth factor-beta (TGF-beta) were examined by real-time PCR. miR-155 mimics and inhibitor were used to verify the role of miR-155 for Treg cells function. Results: OM-85 BV, miR-155 mimics or their combination reduced total cells, lymphocytes, neutrophils and eosinophils in nasal lavage fluid of AR mouse models and improved allergic symptoms. OM-85 BV promoted the proliferation of Treg and the expression of Foxp3, IL-10 and TGF-beta both in vivo and in vitro. The miR-155 enhanced the proliferation and treated experimental models of AR and alleviate the upper airway allergic inflammation in AR mice.