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Clinical and Vaccine Immunology, November 2008, p. 1730-1736, Vol. 15, No. 11
1071-412X/08/$08.00+0 doi:10.1128/CVI.00286-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Experimental Pathology Section, Department of Pathology, National Institute of Medical Sciences and Nutrition "Salvador Zubiràn," Mexico City, Mexico,1 Stanford Rook, Ltd., Centre Point, 103 New Oxford Street, London WC1A 1DD, United Kingdom,2 UCL Centre for Infectious Diseases and International Health, University College London Medical School, London W1T 4JF, United Kingdom3
Received 24 July 2008/ Returned for modification 2 September 2008/ Accepted 19 September 2008
The environmental saprophyte Mycobacterium vaccae induces a Th1 response and cytotoxic T cells that recognize M. tuberculosis, and by subcutaneous injection, it is therapeutic for pulmonary tuberculosis (TB) induced by high-dose challenge in BALB/c mice. However, M. vaccae also drives regulatory T cells that inhibit Th2 responses, and this is seen in allergy models, not only following subcutaneous injection but also after oral administration. An oral immunotherapeutic for TB would be clinically useful, so we investigated M. vaccae given orally by gavage at 28-day intervals in the TB model. We used two different protocols: starting the oral M. vaccae either 1 day before or 32 days after infection with M. tuberculosis. Throughout the infection (until 120 days), we monitored outcome (CFU), molecules involved in the development of immunoregulation (Foxp3, hemoxygenase 1, idoleamine 2,3-dioxygenase, and transforming growth factor β [TGF-β]), and indicators of cytokine balance (tumor necrosis factor, inducible nitric oxide synthase, interleukin-4 [IL-4], and IL-4
2; an inhibitory splice variant of IL-4 associated with improved outcome in human TB). Oral M. vaccae had a significant effect on CFU and led to increased expression of Th1 markers and of IL-4
2, while suppressing IL-4, Foxp3, and TGF-β. When administered 1 day before infection, oral M. vaccae induced a striking peak of expression of hemoxygenase 1. In conclusion, we show novel information about the expression in TB of murine IL-4
2 and molecules involved in immunoregulation and show that these can be modulated by oral administration of a saprophytic mycobacterium. A clinical trial of oral M. vaccae in extensively drug-resistant TB might be justified.
Published ahead of print on 30 September 2008.
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