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Selective delipidation of Mycobacterium bovis BCG enables direct pulmonary vaccination and enhances protection against Mycobacterium tuberculosis.

ABSTRACT: Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis (TB), is the leading killer due to an infectious organism. Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the only vaccine approved against TB, however, its efficacy against pulmonary TB is poor. While BCG is currently inoculated intradermally, the natural route of M.tb infection is through the lung. Excessive lung pathology caused by pulmonary inoculation of BCG has prevented the use of this immunization route. Here, we show that selective chemical treatment of BCG with petroleum ether removes inflammatory lipids from the bacterial surface while keeping BCG viable. Pulmonary vaccination using this modified BCG attenuated inflammatory responses, prevented immunopathology of the lung, and significantly increased protection against M.tb infection in mice. We further directly linked IL-17A as the responsible contributor of improved immunity against M.tb infection. These results provide evidence that selective removal of cytotoxic lipids from the BCG surface attenuates inflammation and offers a safer and superior vaccine against TB causing less damage post-infectious challenge with M.tb.

SUBMITTER: Moliva JI

PROVIDER: S-EPMC6462255 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Selective delipidation of Mycobacterium bovis BCG enables direct pulmonary vaccination and enhances protection against Mycobacterium tuberculosis.

Moliva Juan I JI Hossfeld Austin P AP Sidiki Sabeen S Canan Cynthia H CH Dwivedi Varun V Beamer Gillian G Turner Joanne J Torrelles Jordi B JB

Mucosal immunology 20190218 3

Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis (TB), is the leading killer due to an infectious organism. Mycobacterium bovis bacillus Calmette-Guérin (BCG) is the only vaccine approved against TB, however, its efficacy against pulmonary TB is poor. While BCG is currently inoculated intradermally, the natural route of M.tb infection is through the lung. Excessive lung pathology caused by pulmonary inoculation of BCG has prevented the use of this immunization route. Here, ...[more]

PMID: 30778118

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Project description:A new vaccination strategy is urgently needed for improved control of the global tuberculosis (TB) epidemic. Using a mouse aerosol Mycobacterium tuberculosis challenge model, we investigated the protective efficacy of a mmaA4 gene deletion mutant of Mycobacterium bovis BCG (?mmaA4BCG) formulated in dimethyl dioctadecyl ammonium bromide (DDA) - D(+) trehalose 6,6 dibenenate (TDB) (DDA/TDB) adjuvant. In previous studies, deletion of the mmaA4 gene was shown to reduce the suppression of IL-12 production often seen after mycobacterial infections. While the non-adjuvanted ?mmaA4BCG strain did not protect mice substantially better than conventional BCG against a tuberculous challenge in four protection experiments, the protective responses induced by the ?mmaA4BCG vaccine formulated in DDA/TDB adjuvant was consistently increased relative to nonadjuvanted BCG controls. Furthermore, the ?mmaA4BCG-DDA/TDB vaccine induced significantly higher frequencies of multifunctional (MFT) CD4 T cells expressing both IFN? and TNF? (double positive) or IFN?, TNF? and IL-2 (triple positive) than CD4 T cells derived from mice vaccinated with BCG. These MFT cells were characterized by having higher IFN? and TNF? median fluorescence intensity (MFI) values than monofunctional CD4 T cells. Interestingly, both BCG/adjuvant and ?mmaA4BCG/adjuvant formulations induced significantly higher frequencies of CD4 T cells expressing TNF? and IL-2 than nonadjuvanted BCG or ?mmaA4BCG vaccines indicating that BCG/adjuvant mixtures may be more effective at inducing central memory T cells. Importantly, when either conventional BCG or the mutant were formulated in adjuvant and administered to SCID mice or immunocompromised mice depleted of IFN?, significantly lower vaccine-derived mycobacterial CFU were detected relative to immunodeficient mice injected with non-adjuvanted BCG. Overall, these data suggest that immunization with the ?mmaA4BCG/adjuvant formulation may be an effective, safe, and relatively inexpensive alternative to vaccination with conventional BCG.

Project description:UnlabelledThe current tuberculosis (TB) vaccine, Mycobacterium bovis Bacillus Calmette-Guérin (BCG), provides insufficient protection against pulmonary TB. Previously, we generated a listeriolysin-expressing recombinant BCG strain, which to date has successfully completed phase I and phase IIa clinical trials. In an attempt to further improve efficacy, we deleted the antiapoptotic virulence gene nuoG, encoding NADH dehydrogenase 1 subunit G, from BCG ΔureC::hly In vitro, deletion of nuoG unexpectedly led to strongly increased recruitment of the autophagosome marker LC3 to the engulfed vaccine, suggesting that nuoG also affects xenophagic pathways. In mice, BCG ΔureC::hly ΔnuoG vaccination was safer than BCG and improved protection over that of parental BCG ΔureC::hly, significantly reducing TB load in murine lungs, ameliorating pulmonary pathology, and enhancing immune responses. Transcriptome analysis of draining lymph nodes after vaccination with either BCG ΔureC::hly or BCG ΔureC::hly ΔnuoG demonstrated earlier and stronger induction of immune responses than that with BCG SSI and suggested upregulation of inflammasome activation and interferon-induced GTPases. In summary, BCG ΔureC::hly ΔnuoG is a promising next-generation TB vaccine candidate with excellent efficacy and safety.ImportanceAutophagy and apoptosis are fundamental processes allowing cells to degrade their components or kill themselves, respectively. The immune system has adopted these mechanisms to eliminate intracellular pathogens. Residing in host cells, the causative agent of tuberculosis, Mycobacterium tuberculosis, has evolved strategies to set cellular programs of autophagy and apoptosis "on hold." The mycobacterial gene nuoG was found to prevent host cell apoptosis. We have deleted nuoG in the live vaccine candidate BCG ΔureC::hly, which is in phase II clinical development, to leave cellular apoptosis "on go" upon immunization. In preclinical models, this strategy boosted immunity and improved protection from M. tuberculosis infection. Unexpectedly, we obtained compelling evidence that mycobacterial nuoG facilitates inhibition of autophagic pathways, suggesting a new role for this gene in the host-pathogen interplay in tuberculosis.

Dataset Information

Selective delipidation of Mycobacterium bovis BCG enables direct pulmonary vaccination and enhances protection against Mycobacterium tuberculosis.

Publications

Selective delipidation of Mycobacterium bovis BCG enables direct pulmonary vaccination and enhances protection against Mycobacterium tuberculosis.

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