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Systematic, multiparametric analysis of Mycobacterium tuberculosis intracellular infection offers insight into coordinated virulence.

ABSTRACT: A key to the pathogenic success of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is the capacity to survive within host macrophages. Although several factors required for this survival have been identified, a comprehensive knowledge of such factors and how they work together to manipulate the host environment to benefit bacterial survival are not well understood. To systematically identify Mtb factors required for intracellular growth, we screened an arrayed, non-redundant Mtb transposon mutant library by high-content imaging to characterize the mutant-macrophage interaction. Based on a combination of imaging features, we identified mutants impaired for intracellular survival. We then characterized the phenotype of infection with each mutant by profiling the induced macrophage cytokine response. Taking a systems-level approach to understanding the biology of identified mutants, we performed a multiparametric analysis combining pathogen and host phenotypes to predict functional relationships between mutants based on clustering. Strikingly, mutants defective in two well-known virulence factors, the ESX-1 protein secretion system and the virulence lipid phthiocerol dimycocerosate (PDIM), clustered together. Building upon the shared phenotype of loss of the macrophage type I interferon (IFN) response to infection, we found that PDIM production and export are required for coordinated secretion of ESX-1-substrates, for phagosomal permeabilization, and for downstream induction of the type I IFN response. Multiparametric clustering also identified two novel genes that are required for PDIM production and induction of the type I IFN response. Thus, multiparametric analysis combining host and pathogen infection phenotypes can be used to identify novel functional relationships between genes that play a role in infection.

SUBMITTER: Barczak AK

PROVIDER: S-EPMC5444860 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Systematic, multiparametric analysis of Mycobacterium tuberculosis intracellular infection offers insight into coordinated virulence.

Barczak Amy K AK Avraham Roi R Singh Shantanu S Luo Samantha S SS Zhang Wei Ran WR Bray Mark-Anthony MA Hinman Amelia E AE Thompson Matthew M Nietupski Raymond M RM Golas Aaron A Montgomery Paul P Fitzgerald Michael M Smith Roger S RS White Dylan W DW Tischler Anna D AD Carpenter Anne E AE Hung Deborah T DT

PLoS pathogens 20170515 5

A key to the pathogenic success of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is the capacity to survive within host macrophages. Although several factors required for this survival have been identified, a comprehensive knowledge of such factors and how they work together to manipulate the host environment to benefit bacterial survival are not well understood. To systematically identify Mtb factors required for intracellular growth, we screened an arrayed, non-redunda ...[more]

PMID: 28505176

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Project description:A better understanding of the kinetics of accumulated immune cells that are involved in pathophysiology during Mycobacterium tuberculosis (Mtb) infection may help to facilitate the development of vaccines and immunological interventions. However, the kinetics of innate and adaptive cells that are associated with pathogenesis during Mtb infection and their relationship to Mtb virulence are not clearly understood. In this study, we used a mouse model to compare the bacterial burden, inflammation and kinetics of immune cells during aerogenic infection in the lung between laboratory-adapted strains (Mtb H37Rv and H37Ra) and Mtb K strain, a hyper-virulent W-Beijing lineage strain. The Mtb K strain multiplied more than 10- and 3.54-fold more rapidly than H37Ra and H37Rv, respectively, during the early stage of infection (at 28 days post-infection) and resulted in exacerbated lung pathology at 56 to 112 days post-infection. Similar numbers of innate immune cells had infiltrated, regardless of the strain, by 14 days post-infection. High, time-dependent frequencies of F4/80-CD11c+CD11b-Siglec-H+PDCA-1+ plasmacytoid DCs and CD11c-CD11b+Gr-1int cells were observed in the lungs of mice that were infected with the Mtb K strain. Regarding adaptive immunity, Th1 and Th17 T cells that express T-bet and RORγt, respectively, significantly increased in the lungs that were infected with the laboratory-adapted strains, and the population of CD4+CD25+Foxp3+ regulatory T cells was remarkably increased at 112 days post-infection in the lungs of mice that were infected with the K strain. Collectively, our findings indicate that the highly virulent Mtb K strain may trigger the accumulation of pDCs and Gr1intCD11b+ cells with the concomitant down-regulation of the Th1 response and the maintenance of an up-regulated Th2 response without inducing a Th17 response during chronic infection. These results will help to determine which immune system components must be considered for the development of tuberculosis (TB) vaccines and immunological interventions.

Project description:Virulence effectors secreted by Mycobacterium tuberculosis (Mtb) help subvert host immune mechanisms and, therefore, are critical for establishing infection and pathogenesis. However, knowledge in terms of signaling mechanisms that modulate the secretion of virulence factors is sparse. We performed high-throughput secretome, phosphoproteome, and phospho-secretome analysis of Mtb. We combined the analysis with empirical validations to show regulation of mycobacterial secretion through protein phosphorylation. System level protein-protein interaction network analysis superimposed with the secretome, phosphoproteome, and phospho-secretome profile revealed an intricate relationship between phosphorylation and secretion. At the core of the network was a key virulence factor CFP10. We identified PknA to be the kinase responsible for phosphorylating CFP10. Using genetic tools, we show that phosphomimetic mutation of CFP10 negatively regulates the secretion of virulence mediator ESAT6. Significantly, the dynamics of CFP10 phosphorylation strongly influenced bacterial virulence and survival within macrophages and mice. Together, the results show that the dynamic phosphorylation status of the secretory protein CFP10 regulates the secretion of virulence factors and impacts virulence. IMPORTANCE Secreted virulence factors play a critical role in bacterial pathogenesis. Virulence effectors not only help bacteria to overcome the host immune system but also aid in establishing infection. Mtb, which causes tuberculosis in humans, encodes various virulence effectors. Triggers that modulate the secretion of virulence effectors in Mtb are yet to be fully understood. To gain mechanistic insight into the secretion of virulence effectors, we performed high-throughput proteomic studies. With the help of system-level protein-protein interaction network analysis and empirical validations, we unravelled a link between phosphorylation and secretion. Taking the example of the well-known virulence factor of CFP10, we show that the dynamics of CFP10 phosphorylation strongly influenced bacterial virulence and survival ex vivo and in vivo. This study presents the role of phosphorylation in modulating the secretion of virulence factors.

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Systematic, multiparametric analysis of Mycobacterium tuberculosis intracellular infection offers insight into coordinated virulence.

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Systematic, multiparametric analysis of Mycobacterium tuberculosis intracellular infection offers insight into coordinated virulence.

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