A novel synthetic mycolic acid inhibits bronchial hyperresponsiveness and allergic inflammation in a mouse model of asthma

Purpose: Recognition of microbes is important to trigger the innate immune system. Mycolic acid (MA) is a component of the cell walls of mycobacteria such as Mycobacterium bovis Bacillus Calmette-Guerin. MA has immunogenic properties, which may modulate the innate and adaptive immune response. This study aimed to investigate whether a novel synthetic MA (sMA) inhibits allergic inflammatory responses in a mouse model of asthma. Methods: BALB/c mice were injected intraperitoneally with sMA followed by sensitization and challenge with ovalbumin (OVA). Mice were examined for bronchial hyperresponsiveness (BHR), the influx of inflammatory cells into the lung tissues, histopathological changes in the lungs and CD4⁺CD25⁺Foxp3⁺ T cells in the spleen, and examined the response after the depleting regulatory T cells (Tregs) with an anti-CD25mAb. Results: Treatment of mice with sMA suppressed the asthmatic response, including BHR, bronchoalveolar inflammation, and pulmonary eosinophilic inflammation. Anti-CD25mAb treatment abrogated the suppressive effects of sMA in this mouse model of asthma and totally depleted CD4⁺CD25⁺ Foxp3⁺ T cells in the spleen. Conclusions: sMA attenuated allergic inflammation in a mouse model of asthma, which might be related with CD4⁺ CD25⁺Foxp3⁺T cell.