Recombinant BCG Expressing ESX-1 of Mycobacterium marinum Combines Low Virulence with Cytosolic Immune Signaling and Improved TB Protection

Publication date: 14 March 2017
Source:Cell Reports, Volume 18, Issue 11
Author(s): Matthias I. Gröschel, Fadel Sayes, Sung Jae Shin, Wafa Frigui, Alexandre Pawlik, Mickael Orgeur, Robin Canetti, Nadine Honoré, Roxane Simeone, Tjip S. van der Werf, Wilbert Bitter, Sang-Nae Cho, Laleh Majlessi, Roland Brosch
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-1^Mmar) 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-1^Mmar confers superior protection relative to parental BCG against challenges with highly virulent M. tuberculosis.

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Teaser

Gröschel et al. describe the virulence-neutral expression of the ESX-1 type VII secretion system of Mycobacterium marinum in the attenuated BCG vaccine. ESX-1-marinum enables recombinant BCG to rupture the phagosome and to induce cytosolic pattern recognition and dedicated innate immune signaling in mice, resulting in increased protection against tuberculosis.


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