Cell Reports
Volume 18, Issue 11, 14 March 2017, Pages 2752-2765
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Article
Recombinant BCG Expressing ESX-1 of Mycobacterium marinum Combines Low Virulence with Cytosolic Immune Signaling and Improved TB Protection

https://doi.org/10.1016/j.celrep.2017.02.057Get rights and content
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Highlights

  • BCG expressing the ESX-1 T7 secretion system of M. marinum induces phagosomal rupture

  • Rupture-induced innate immune signaling leads to IFN-β and enhanced IL-1β release

  • ESX-1 signaling induces CD8+ and Ag-specific CD4+ T cell responses and high protection

  • Recombinant BCG-expressing ESX-1 of BSL2 organism M. marinum shows low virulence

Summary

Recent insights into the mechanisms by which Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, is recognized by cytosolic nucleotide sensors have opened new avenues for rational vaccine design. The only licensed anti-tuberculosis vaccine, Mycobacterium bovis BCG, provides limited protection. A feature of BCG is the partial deletion of the ESX-1 type VII secretion system, which governs phagosomal rupture and cytosolic pattern recognition, key intracellular phenotypes linked to increased immune signaling. Here, by heterologously expressing the esx-1 region of Mycobacterium marinum in BCG, we engineered a low-virulence, ESX-1-proficient, recombinant BCG (BCG::ESX-1Mmar) that induces the cGas/STING/TBK1/IRF-3/type I interferon axis and enhances AIM2 and NLRP3 inflammasome activity, resulting in both higher proportions of CD8+ T cell effectors against mycobacterial antigens shared with BCG and polyfunctional CD4+ Th1 cells specific to ESX-1 antigens. Importantly, independent mouse vaccination models show that BCG::ESX-1Mmar confers superior protection relative to parental BCG against challenges with highly virulent M. tuberculosis.

Keywords

tuberculosis
Mycobacterium tuberculosis
recombinant BCG
ESX/type VII secretion
vaccination
Mycobacterium marinum
cytosolic pattern recognition
innate immune signaling

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