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Project description:Tuberculosis (TB) remains the world’s top infectious killer. Understanding how immune mediators determine the outcome of Mycobacterium tuberculosis infection could facilitate the design of better therapies against this devastating disease. GM-CSF mediates protective immunity against TB but the underlying mechanisms remain elusive. To determine the molecular mechanisms underlying the protective role of GM-CSF during M. tuberculosis infection we performed RNA-sequencing analyses of whole blood and lung samples obtained from C57Bl/6 mice infected with HN878 and treated with anti-GM-CSF monoclonal antibody or isotype control. Uninfected mice were also treated and used as uninfected controls. Three weeks post-infection, whole blood and lungs were harvested from each individual mouse and processed for RNA-sequencing. Transcriptomic analyses revealed that during M. tuberculosis infection GM-CSF regulates the expression of genes associated with neutrophil recruitment and activation and type I IFN-inducible genes, which have been previously associated with TB pathogenesis. Further mechanistical studies showed that disease exacerbation driven by GM-CSF blockade during M. tuberculosis infection was type I IFN and neutrophil-dependent and that over-activation of neutrophils by type I IFN induced NET formation at the site of infection. NETs were also found in necrotic lung lesions from patients with pulmonary TB and type I IFN-driven NET formation correlated with increased disease susceptibility in different mouse models of TB. Our findings reveal an important immune network that may play a central role in determining TB outcome.
2020-09-07 | GSE141205 | GEO
Project description:Tuberculosis (TB) remains the world’s top infectious killer. Understanding how immune mediators determine the outcome of Mycobacterium tuberculosis infection could facilitate the design of better therapies against this devastating disease. GM-CSF mediates protective immunity against TB but the underlying mechanisms remain elusive. To determine the molecular mechanisms underlying the protective role of GM-CSF during M. tuberculosis infection we performed RNA-sequencing analyses of whole blood and lung samples obtained from C57Bl/6 mice infected with HN878 and treated with anti-GM-CSF monoclonal antibody or isotype control. Uninfected mice were also treated and used as uninfected controls. Three weeks post-infection, whole blood and lungs were harvested from each individual mouse and processed for RNA-sequencing. Transcriptomic analyses revealed that during M. tuberculosis infection GM-CSF regulates the expression of genes associated with neutrophil recruitment and activation and type I IFN-inducible genes, which have been previously associated with TB pathogenesis. Further mechanistical studies showed that disease exacerbation driven by GM-CSF blockade during M. tuberculosis infection was type I IFN and neutrophil-dependent and that over-activation of neutrophils by type I IFN induced NET formation at the site of infection. NETs were also found in necrotic lung lesions from patients with pulmonary TB and type I IFN-driven NET formation correlated with increased disease susceptibility in different mouse models of TB. Our findings reveal an important immune network that may play a central role in determining TB outcome.
2020-09-07 | GSE141192 | GEO
Project description:GM-CSF controls Mycobacterium tuberculosis infection by limiting type I IFN-driven neutrophil extracellular trap formation
| PRJNA592569 | ENA
Project description:GM-CSF controls Mycobacterium tuberculosis infection by limiting type I IFN-driven neutrophil extracellular trap formation [Blood]
| PRJNA592556 | ENA
Project description:GM-CSF controls Mycobacterium tuberculosis infection by limiting type I IFN-driven neutrophil extracellular trap formation [Lung]
| PRJNA592572 | ENA
Project description:Invariant natural killer T (iNKT) cells are activated during infection, but how they limit microbial growth is unknown in most cases. We investigated how iNKT cells suppress intracellular Mycobacterium tuberculosis (Mtb) replication. When co-cultured with infected macrophages, iNKT cell activation, as measured by CD25 upregulation and IFNγ production, was primarily driven by IL-12 and IL-18. In contrast, iNKT cell control of Mtb growth was CD1d-dependent, and did not require IL-12, IL-18, or IFNγ. This demonstrated that conventional activation markers did not correlate with iNKT cell effector function during Mtb infection. iNKT cell control of Mtb replication was also independent of TNF and cell-mediated cytotoxicity. By dissociating cytokine-driven activation and CD1d-restricted effector function, we uncovered a novel mediator of iNKT cell antimicrobial activity: GM-CSF. iNKT cells produced GM-CSF in vitro and in vivo in a CD1d-dependent manner during Mtb infection, and GM-CSF was both necessary and sufficient to control Mtb growth. Here, we have identified GM-CSF production as a novel iNKT cell antimicrobial effector function and uncovered a potential role for GM-CSF in T cell immunity against Mtb.
| S-EPMC3879349 | biostudies-literature
Project description:Mycobacterium tuberculosis infection generates pulmonary granulomas that consist of a caseous, necrotic core surrounded by an ordered arrangement of macrophages, neutrophils and T cells. This inflammatory pathology is essential for disease transmission and M. tuberculosis has evolved to stimulate inflammatory granuloma development while simultaneously avoiding destruction by the attracted phagocytes. The most abundant phagocyte in active necrotic granulomas is the neutrophil. Here we show that the ESAT-6 protein secreted by the ESX-1 type VII secretion system causes necrosis of the neutrophils. ESAT-6 induced an intracellular Ca(2+) overload followed by necrosis of phosphatidylserine externalised neutrophils. This necrosis was dependent upon the Ca(2+) activated protease calpain, as pharmacologic inhibition prevented this secondary necrosis. We also observed that the ESAT-6 induced increase in intracellular Ca(2+), stimulated the production of neutrophil extracellular traps characterised by extruded DNA and myeloperoxidase. Thus we conclude that ESAT-6 has a leukocidin function, which may facilitate bacterial avoidance of the antimicrobial action of the neutrophil while contributing to the maintenance of inflammation and necrotic pathology necessary for granuloma formation and TB transmission.
| S-EPMC4237235 | biostudies-literature
Project description:Although classically associated with myelopoiesis, granulocyte-macrophage colony-stimulating factor (GM-CSF) is being increasingly recognized for its potential role in innate resistance against tuberculosis (TB). While the GM-CSF is produced by a variety of host cells, including conventional and non-conventional T cells, macrophages, alveolar epithelial cells, the cell population that promotes GM-CSF mediated innate protection against Mycobacterium tuberculosis infection remains unclear. This is because studies related to the role of GM-CSF so far have been carried out in murine models of experimental TB, which is inherently susceptible to TB as compared to humans, who exhibit a resolution of infection in majority of cases. We found a significantly higher amount of GM-CSF production by human macrophages, compared to mouse macrophages, after infection with M. tuberculosis in vitro. The higher levels of GM-CSF produced by human macrophages were also directly correlated with their increased life span and ability to control M. tuberculosis infection. Other evidence from recent studies also support that M. tuberculosis infected human macrophages display heterogeneity in their antibacterial capacity, and cells with increased expression of genes involved in GM-CSF signaling pathway can control intracellular M. tuberculosis growth more efficiently. Collectively, these emerging evidence indicate that GM-CSF produced by lung resident macrophages could be vital for the host resistance against M. tuberculosis infection in humans. Identification of GM-CSF dependent key cellular pathways/processes that mediate intracellular host defense can lay the groundwork for the development of novel host directed therapies against TB as well as other intracellular infections.
| S-EPMC7390890 | biostudies-literature
Project description:Variability in bacterial sterilization is a key feature of Mycobacterium tuberculosis (Mtb) disease. In a population of human macrophages, there are macrophages that restrict Mtb growth and those that do not. However, the sources of heterogeneity in macrophage state during Mtb infection are poorly understood. Here, we perform RNAseq on restrictive and permissive macrophages and reveal that the expression of genes involved in GM-CSF signaling discriminates between the two subpopulations. We demonstrate that blocking GM-CSF makes macrophages more permissive of Mtb growth while addition of GM-CSF increases bacterial control. In parallel, we find that the loss of bacterial control that occurs in HIV-Mtb coinfected macrophages correlates with reduced GM-CSF secretion. Treatment of coinfected cells with GM-CSF restores bacterial control. Thus, we leverage the natural variation in macrophage control of Mtb to identify a critical cytokine response for regulating Mtb survival and identify components of the antimicrobial response induced by GM-CSF.
| S-EPMC6536549 | biostudies-other
Project description:Several in vitro cellular models have been developed with the aim to reproduce and dissect human granulomatous responses, the hallmark of tuberculosis (TB) immunopathogenesis. In that context, we compared two- (2D) versus three-dimensional (3D) granuloma models resulting from infection of human peripheral blood mononuclear cells with M. tuberculosis (Mtb) in the absence or presence of a collagen-based extracellular matrix (ECM). Granuloma formation was found to be significantly enhanced in the 2D model. This feature was associated with an earlier chemokine production and lymphocyte activation, but also a significantly increased bacterial burden. Remarkably, the reduction in Mtb burden in the 3D model correlated with an increase in GM-CSF production. GM-CSF, which is known to promote macrophage survival, was found to be inherently induced by the ECM. We observed that only 3D in vitro granulomas led to the accumulation of lipid inclusions within Mtb. Our data suggest that a hypoxic environment within the ECM could be responsible for this dormant-like Mtb phenotype. Furthermore, exposure to a TNF-α antagonist reverted Mtb dormancy, thereby mimicking the reactivation of TB observed in rheumatic patients receiving this therapy. To conclude, we showed that only in vitro granulomas generated in the presence of an ECM could recapitulate some clinically relevant features of granulomatous responses in TB. As such, this model constitutes a highly valuable tool to study the interplay between immunity and Mtb stress responses as well as to evaluate novel treatment strategies.
| S-EPMC8486295 | biostudies-literature