Effect of oral feeding with Clostridium leptum on regulatory T-cell responses and allergic airway inflammation in mice

Background: Allergic lung inflammation is mediated by allergen-specific T responses, which are negatively regulated by regulatory T cells (Tregs). Previous studies have reported that inoculation of indigenous Clostridium species in the early lives of mice can induce Tregs that colonize the colon. However, whether inoculation of C leptum alone in adult mice could induce systemic Treg responses and inhibit allergic airway inflammation remains unclear. Objective: To investigate the effect of oral administration of C leptum on systemic Treg responses and allergic airway inflammation in a mouse model of asthma. Methods: Adult BABL/c mice were injected with ovalbumin to induce asthma and treated orally with C leptum or vehicle daily for 2 weeks. The numbers of Foxp3(+)CD4(+)CD25(+) Tregs in both the spleen and mediastinal lymph nodes were examined by flow cytometry. After allergen challenge, the airway hyperresponsiveness of individual mice was measured, and the numbers of inflammatory infiltrates and the levels of cytokines in bronchoalveolar lavage fluids ere determined. Results: Oral feeding with C leptum increased the percentage and total number of Tregs in the spleens and mediastinal lymph nodes at 14 days after inoculation and attenuated allergen-induced airway hyperresponsiveness and inflammation by inhibiting inflammatory cytokine production but enhancing interleukin 10 and transforming growth factor beta 1 production in the lungs. Conclusion: Oral treatment with C leptum can attenuate induced allergic airway inflammation in adult mice. (C) 2012 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.