GLS/IL-12-modified Mycobacterium smegmatis as a novel anti-tuberculosis immunotherapeutic vaccine.

OBJECTIVE

To study the effects and mechanisms of recombinant Mycobacterium smegmatis (rMS) carrying pZM03 (a co-expression plasmid encoding human granulysin [GLS] and murine interleukin 12 [IL-12]) on murine M. tuberculosis infection.

DESIGN

BALB/c mice infected with M. tuberculosis were treated with normal saline, M. smegmatis, pZM03 or rMS. The number of viable bacteria in the lungs and spleens were counted to observe the therapeutic effects. The levels of IL-12 and interferon-gamma (IFN-gamma) in serum, and IFN-gamma and tumour necrosis factor-alpha (TNF-alpha) released from spleen lymphocytes were detected to observe the T-helper 1 (Th1) response. Secretory IgA (SIgA) in bronchoalveolar lavage fluid was measured to observe the mucosal immunity. The lungs and spleens were prepared for pathological analysis.

RESULTS

The rMS group showed a significantly reduced number of colony-forming units compared to the other groups. The expression of GLS in the tissue, and increased levels of IL-12, IFN-gamma, TNF-alpha and SIgA, were found in the rMS group. The pathological changes in the lungs of the rMS group were localised, while those in the control group were extensive.

CONCLUSION

rMS had immunotherapeutic effects associated with a switch to the Th1 response and the antibacterial activity of GLS.