Effects of <i>Mycobacterium vaccae</i> Aerosol Inhalation on Airway Inflammation in Asthma Mouse Model

Background:Mycobacterium vaccae vaccine, a composition of Mycobacterium proteins, has been known to have bidirectional immunomodulatory functions. Recent studies have shown that M. vaccae has a therapeutic potential for treating asthma. However, little is known regarding the effect of M. vaccae aerosol inhalation during allergen sensitization or challenge on asthma. The purpose of this study was to explore the effect and the underlying mechanism of M. vaccae aerosol inhalation during allergen sensitization or challenge on airway inflammation in an asthma mouse model. Methods: Asthma mouse models were established. Mice received aerosol inhalation with M. vaccae once daily during allergen sensitization or challenge for 5 days successively. Airway responsiveness, bronchoalveolar lavage fluid (BALF) cell count, histology, and cytokine concentrations (IL-4, IFN-γ, IL-10, and IL-17) were measured. The relative mRNA expression of ASC, caspase-1, TNF-α, and IL-1β was also determined. Expression of pulmonary NLRP3 and nuclear factor kappa B (NF-κB) protein was measured using immunohistochemistry and Western blot. Results:M. vaccae aerosol inhalation suppressed airway hyperresponsiveness and inflammation, reduced levels of IL-4, upregulated expression of IFN-γ and IL-10 in BALF, inhibited mRNA expression of pulmonary ASC, caspase-1, TNF-α, and IL-1β, and also inhibited expression of pulmonary NLRP3 and NF-κB protein during allergen sensitization or challenge. Conclusion:M. vaccae aerosol inhalation can suppress airway hyperresponsiveness and inflammation during allergen sensitization or challenge, and may be a promising approach for asthma therapy.