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Latent tuberculosis infection: myths, models, and molecular mechanisms. Microbiol Mol Biol Rev 2015; 78:343-71. [PMID: 25184558 DOI: 10.1128/mmbr.00010-14] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The aim of this review is to present the current state of knowledge on human latent tuberculosis infection (LTBI) based on clinical studies and observations, as well as experimental in vitro and animal models. Several key terms are defined, including "latency," "persistence," "dormancy," and "antibiotic tolerance." Dogmas prevalent in the field are critically examined based on available clinical and experimental data, including the long-held beliefs that infection is either latent or active, that LTBI represents a small population of nonreplicating, "dormant" bacilli, and that caseous granulomas are the haven for LTBI. The role of host factors, such as CD4(+) and CD8(+) T cells, T regulatory cells, tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ), in controlling TB infection is discussed. We also highlight microbial regulatory and metabolic pathways implicated in bacillary growth restriction and antibiotic tolerance under various physiologically relevant conditions. Finally, we pose several clinically important questions, which remain unanswered and will serve to stimulate future research on LTBI.
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Malhotra V, Agrawal R, Duncan TR, Saini DK, Clark-Curtiss JE. Mycobacterium tuberculosis response regulators, DevR and NarL, interact in vivo and co-regulate gene expression during aerobic nitrate metabolism. J Biol Chem 2015; 290:8294-309. [PMID: 25659431 DOI: 10.1074/jbc.m114.591800] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mycobacterium tuberculosis genes Rv0844c/Rv0845 encoding the NarL response regulator and NarS histidine kinase are hypothesized to constitute a two-component system involved in the regulation of nitrate metabolism. However, there is no experimental evidence to support this. In this study, we established M. tuberculosis NarL/NarS as a functional two-component system and identified His(241) and Asp(61) as conserved phosphorylation sites in NarS and NarL, respectively. Transcriptional profiling between M. tuberculosis H37Rv and a ΔnarL mutant strain during exponential growth in broth cultures with or without nitrate defined an ∼30-gene NarL regulon that exhibited significant overlap with DevR-regulated genes, thereby implicating a role for the DevR response regulator in the regulation of nitrate metabolism. Notably, expression analysis of a subset of genes common to NarL and DevR regulons in M. tuberculosis ΔdevR, ΔdevSΔdosT, and ΔnarL mutant strains revealed that in response to nitrite produced during aerobic nitrate metabolism, the DevRS/DosT regulatory system plays a primary role that is augmented by NarL. Specifically, NarL itself was unable to bind to the narK2, acg, and Rv3130c promoters in phosphorylated or unphosphorylated form; however, its interaction with DevR∼P resulted in cooperative binding, thereby enabling co-regulation of these genes. These findings support the role of physiologically derived nitrite as a metabolic signal in mycobacteria. We propose NarL-DevR binding, possibly as a heterodimer, as a novel mechanism for co-regulation of gene expression by the DevRS/DosT and NarL/NarS regulatory systems.
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Affiliation(s)
- Vandana Malhotra
- From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and
| | - Ruchi Agrawal
- the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India
| | - Tammi R Duncan
- From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and
| | - Deepak K Saini
- the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India
| | - Josephine E Clark-Curtiss
- From the Center for Infectious Diseases and Vaccinology, Biodesign Institute, and the School of Life Sciences, Arizona State University, Tempe, Arizona 85287 and
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Gold B, Warrier T, Nathan C. A multi-stress model for high throughput screening against non-replicating Mycobacterium tuberculosis. Methods Mol Biol 2015; 1285:293-315. [PMID: 25779324 DOI: 10.1007/978-1-4939-2450-9_18] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Models of non-replication help us understand the biology of persistent Mycobacterium tuberculosis. High throughput screening (HTS) against non-replicating M. tuberculosis may lead to identification of tool compounds that affect pathways on which bacterial survival depends in such states, and to development of drugs that can overcome phenotypic tolerance to conventional antimycobacterial agents, which are mostly active against replicating M. tuberculosis. We describe a multi-stress model of non-replication that mimics some of the microenvironmental conditions that M. tuberculosis faces in the host as adapted for HTS. The model includes acidic pH, mild hypoxia, a flux of nitric oxide and other reactive nitrogen intermediates arising from nitrite at low pH, and low concentrations of a fatty acid (butyrate) as a carbon source.
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Affiliation(s)
- Ben Gold
- Department of Microbiology and Immunology, Weill Cornell Medical College, Belfer 1126, 413 East 69th St., New York, NY, 10065, USA,
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54
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bis-Molybdopterin guanine dinucleotide is required for persistence of Mycobacterium tuberculosis in guinea pigs. Infect Immun 2014; 83:544-50. [PMID: 25404027 DOI: 10.1128/iai.02722-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mycobacterium tuberculosis is able to synthesize molybdopterin cofactor (MoCo), which is utilized by numerous enzymes that catalyze redox reactions in carbon, nitrogen, and sulfur metabolism. In bacteria, MoCo is further modified through the activity of a guanylyltransferase, MobA, which converts MoCo to bis-molybdopterin guanine dinucleotide (bis-MGD), a form of the cofactor that is required by the dimethylsulfoxide (DMSO) reductase family of enzymes, which includes the nitrate reductase NarGHI. In this study, the functionality of the mobA homolog in M. tuberculosis was confirmed by demonstrating the loss of assimilatory and respiratory nitrate reductase activity in a mobA deletion mutant. This mutant displayed no survival defects in human monocytes or mouse lungs but failed to persist in the lungs of guinea pigs. These results implicate one or more bis-MGD-dependent enzymes in the persistence of M. tuberculosis in guinea pig lungs and underscore the applicability of this animal model for assessing the role of molybdoenzymes in this pathogen.
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Raffetseder J, Pienaar E, Blomgran R, Eklund D, Patcha Brodin V, Andersson H, Welin A, Lerm M. Replication rates of Mycobacterium tuberculosis in human macrophages do not correlate with mycobacterial antibiotic susceptibility. PLoS One 2014; 9:e112426. [PMID: 25386849 PMCID: PMC4227709 DOI: 10.1371/journal.pone.0112426] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/15/2014] [Indexed: 11/19/2022] Open
Abstract
The standard treatment of tuberculosis (TB) takes six to nine months to complete and this lengthy therapy contributes to the emergence of drug-resistant TB. TB is caused by Mycobacterium tuberculosis (Mtb) and the ability of this bacterium to switch to a dormant phenotype has been suggested to be responsible for the slow clearance during treatment. A recent study showed that the replication rate of a non-virulent mycobacterium, Mycobacterium smegmatis, did not correlate with antibiotic susceptibility. However, the question whether this observation also holds true for Mtb remains unanswered. Here, in order to mimic physiological conditions of TB infection, we established a protocol based on long-term infection of primary human macrophages, featuring Mtb replicating at different rates inside the cells. During conditions that restricted Mtb replication, the bacterial phenotype was associated with reduced acid-fastness. However, these phenotypically altered bacteria were as sensitive to isoniazid, pyrazinamide and ethambutol as intracellularly replicating Mtb. In support of the recent findings with M. smegmatis, we conclude that replication rates of Mtb do not correlate with antibiotic tolerance.
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Affiliation(s)
- Johanna Raffetseder
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Elsje Pienaar
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Robert Blomgran
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Daniel Eklund
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Veronika Patcha Brodin
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Henrik Andersson
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Amanda Welin
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
| | - Maria Lerm
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, SE-58185, Sweden
- * E-mail:
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56
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Monin L, Khader SA. Chemokines in tuberculosis: the good, the bad and the ugly. Semin Immunol 2014; 26:552-8. [PMID: 25444549 DOI: 10.1016/j.smim.2014.09.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 09/15/2014] [Accepted: 09/21/2014] [Indexed: 10/24/2022]
Abstract
Mycobacterium tuberculosis (Mtb) infects about one-third of the world's population, with a majority of infected individuals exhibiting latent asymptomatic infection, while 5-10% of infected individuals progress to active pulmonary disease. Research in the past two decades has elucidated critical host immune mechanisms that mediate Mtb control. Among these, chemokines have been associated with numerous key processes that lead to Mtb containment, from recruitment of myeloid cells into the lung to activation of adaptive immunity, formation of protective granulomas and vaccine recall responses. However, imbalances in several key chemokine mediators can alter the delicate balance of cytokines and cellular responses that promote mycobacterial containment, instead precipitating terminal tissue destruction and spread of Mtb infection. In this review, we will describe recent insights in the involvement of chemokines in host responses to Mtb infection and Mtb containment (the good), chemokines contributing to inflammation during TB (the bad), and the role of chemokines in driving cavitation and lung pathology (the ugly).
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Affiliation(s)
- Leticia Monin
- Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA; Richard King Mellon Foundation Institute for Pediatric Research, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Shabaana A Khader
- Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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The endothelin system has a significant role in the pathogenesis and progression of Mycobacterium tuberculosis infection. Infect Immun 2014; 82:5154-65. [PMID: 25267836 DOI: 10.1128/iai.02304-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Tuberculosis (TB) remains a major global health problem, and although multiple studies have addressed the relationship between Mycobacterium tuberculosis and the host on an immunological level, few studies have addressed the impact of host physiological responses. Proteases produced by bacteria have been associated with important alterations in the host tissues, and a limited number of these enzymes have been characterized in mycobacterial species. M. tuberculosis produces a protease called Zmp1, which appears to be associated with virulence and has a putative action as an endothelin-converting enzyme. Endothelins are a family of vasoactive peptides, of which 3 distinct isoforms exist, and endothelin 1 (ET-1) is the most abundant and the best-characterized isoform. The aim of this work was to characterize the Zmp1 protease and evaluate its role in pathogenicity. Here, we have shown that M. tuberculosis produces and secretes an enzyme with ET-1 cleavage activity. These data demonstrate a possible role of Zmp1 for mycobacterium-host interactions and highlights its potential as a drug target. Moreover, the results suggest that endothelin pathways have a role in the pathogenesis of M. tuberculosis infections, and ETA or ETB receptor signaling can modulate the host response to the infection. We hypothesize that a balance between Zmp1 control of ET-1 levels and ETA/ETB signaling can allow M. tuberculosis adaptation and survival in the lung tissues.
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Abstract
Several major pathogens, including Mycobacterium tuberculosis, parasitize host cells and exploit host-derived nutrients to sustain their own metabolism. Although the carbon sources that are used by M. tuberculosis have been extensively studied, the mechanisms by which mycobacteria capture and metabolize nitrogen, which is another essential constituent of biomolecules, have only recently been revisited. In this Progress article, we discuss central nitrogen metabolism in M. tuberculosis, the mechanisms that are used by this pathogen to obtain nitrogen from its host and the potential role of nitrogen capture and metabolism in virulence.
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Jantsch J, Schödel J. Hypoxia and hypoxia-inducible factors in myeloid cell-driven host defense and tissue homeostasis. Immunobiology 2014; 220:305-14. [PMID: 25439732 DOI: 10.1016/j.imbio.2014.09.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 08/01/2014] [Accepted: 09/05/2014] [Indexed: 02/08/2023]
Abstract
The impact of tissue oxygenation and hypoxia on immune cells has been recognized as a major determinant of host defense and tissue homeostasis. In this review, we will summarize the available data on tissue oxygenation in inflamed and infected tissue and the effect of low tissue oxygenation on myeloid cell function. Furthermore, we will highlight effects of the master regulators of the cellular hypoxic response, hypoxia-inducible transcription factors (HIF), in myeloid cells in antimicrobial defense and tissue homeostasis.
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Affiliation(s)
- Jonathan Jantsch
- Institut für Klinische Mikrobiologie und Hygiene, Universitätsklinikum Regensburg, Germany; Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen und Friedrich-Alexander Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany.
| | - Johannes Schödel
- Medizinische Klinik 4, Universitätsklinikum Erlangen und Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany; Translational Research Center, Universitätsklinikum Erlangen und Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany.
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60
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Heitmann L, Abad Dar M, Schreiber T, Erdmann H, Behrends J, Mckenzie ANJ, Brombacher F, Ehlers S, Hölscher C. The IL-13/IL-4Rα axis is involved in tuberculosis-associated pathology. J Pathol 2014; 234:338-50. [PMID: 24979482 PMCID: PMC4277691 DOI: 10.1002/path.4399] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/05/2014] [Accepted: 06/22/2014] [Indexed: 01/20/2023]
Abstract
Human tuberculosis (TB) is a leading global health threat and still constitutes a major medical challenge. However, mechanisms governing tissue pathology during post-primary TB remain elusive, partly because genetically or immunologically tractable animal models are lacking. In human TB, the demonstration of a large relative increase in interleukin (IL)-4 and IL-13 expression, which correlates with lung damage, indicates that a subversive T helper (TH)2 component in the response to Mycobacterium tuberculosis (Mtb) may undermine protective immunity and contribute to reactivation and tissue pathology. Up to now, there has been no clear evidence regarding whether IL-4/IL-13-IL-4 receptor-α (Rα)-mediated mechanisms may in fact cause reactivation and pathology. Unfortunately, the virtual absence of centrally necrotizing granulomas in experimental murine TB is associated with a poor induction of a TH2 immune response. We therefore hypothesize that, in mice, an increased production of IL-13 may lead to a pathology similar to human post-primary TB. In our study, aerosol Mtb infection of IL-13-over-expressing mice in fact resulted in pulmonary centrally necrotizing granulomas with multinucleated giant cells, a hypoxic rim and a perinecrotic collagen capsule, with an adjacent zone of lipid-rich, acid-fast bacilli-containing foamy macrophages, thus strongly resembling the pathology in human post-primary TB. Granuloma necrosis (GN) in Mtb-infected IL-13-over-expressing mice was associated with the induction of arginase-1-expressing macrophages. Indirect blockade of the endogenous arginase inhibitor l-hydroxyarginine in Mtb-infected wild-type mice resulted in a strong arginase expression and precipitated a similar pathology of GN. Together, we here introduce an experimental TB model that displays many features of centrally necrotizing granulomas in human post-primary TB and demonstrate that IL-13/IL-4Rα-dependent mechanisms leading to arginase-1 expression are involved in TB-associated tissue pathology.
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Affiliation(s)
- Lisa Heitmann
- Infection Immunology, Research Centre Borstel, Germany; Priority Research Area 'Infections', Research Centre Borstel, Germany
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Mycobacterium tuberculosis Lsr2 is a global transcriptional regulator required for adaptation to changing oxygen levels and virulence. mBio 2014; 5:e01106-14. [PMID: 24895305 PMCID: PMC4049101 DOI: 10.1128/mbio.01106-14] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To survive a dynamic host environment, Mycobacterium tuberculosis must endure a series of challenges, from reactive oxygen and nitrogen stress to drastic shifts in oxygen availability. The mycobacterial Lsr2 protein has been implicated in reactive oxygen defense via direct protection of DNA. To examine the role of Lsr2 in pathogenesis and physiology of M. tuberculosis, we generated a strain deleted for lsr2. Analysis of the M. tuberculosis Δlsr2 strain demonstrated that Lsr2 is not required for DNA protection, as this strain was equally susceptible as the wild type to DNA-damaging agents. The lsr2 mutant did display severe growth defects under normoxic and hyperoxic conditions, but it was not required for growth under low-oxygen conditions. However, it was also required for adaptation to anaerobiosis. The defect in anaerobic adaptation led to a marked decrease in viability during anaerobiosis, as well as a lag in recovery from it. Gene expression profiling of the Δlsr2 mutant under aerobic and anaerobic conditions in conjunction with published DNA binding-site data indicates that Lsr2 is a global transcriptional regulator controlling adaptation to changing oxygen levels. The Δlsr2 strain was capable of establishing an early infection in the BALB/c mouse model; however, it was severely defective in persisting in the lungs and caused no discernible lung pathology. These findings demonstrate M. tuberculosis Lsr2 is a global transcriptional regulator required for control of genes involved in adaptation to extremes in oxygen availability and is required for persistent infection. M. tuberculosis causes nearly two million deaths per year and infects nearly one-third of the world population. The success of this aerobic pathogen is due in part to its ability to successfully adapt to constantly changing oxygen availability throughout the infectious cycle, from the high oxygen tension during aerosol transmission to anaerobiosis within necrotic lesions. An understanding of how M. tuberculosis copes with these changes in oxygen tension is critical for its eventual eradication. Using a mutation in lsr2, we demonstrate that the Lsr2 protein present in all mycobacteria is a global transcriptional regulator in control of genes required for adaptation to changes in oxygen levels. M. tuberculosis lacking lsr2 was unable to adapt to both high and very low levels of oxygen and was defective in long-term anaerobic survival. Lsr2 was also required for disease pathology and for chronic infection in a mouse model of TB.
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Gopinath K, Moosa A, Mizrahi V, Warner DF. Vitamin B(12) metabolism in Mycobacterium tuberculosis. Future Microbiol 2014; 8:1405-18. [PMID: 24199800 DOI: 10.2217/fmb.13.113] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Mycobacterium tuberculosis is included among a select group of bacteria possessing the capacity for de novo biosynthesis of vitamin B12, the largest and most complex natural organometallic cofactor. The bacillus is also able to scavenge B12 and related corrinoids utilizing an ATP-binding cassette-type protein that is distinct from the only known bacterial B12-specific transporter, BtuFCD. Consistent with the inferred requirement for vitamin B12 for metabolic function, the M. tuberculosis genome encodes two B12 riboswitches and three B12-dependent enzymes. Two of these enzymes have been shown to operate in methionine biosynthesis (MetH) and propionate utilization (MutAB), while the function of the putative nrdZ-encoded ribonucleotide reductase remains unknown. Taken together, these observations suggest that M. tuberculosis has the capacity to regulate core metabolic functions according to B12 availability - whether acquired via endogenous synthesis or through uptake from the host environment - and, therefore, imply that there is a role for vitamin B12 in pathogenesis, which remains poorly understood.
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Affiliation(s)
- Krishnamoorthy Gopinath
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit & DST/NRF Center of Excellence for Biomedical TB Research, Institute of Infectious Disease & Molecular Medicine & Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa
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63
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Black PA, Warren RM, Louw GE, van Helden PD, Victor TC, Kana BD. Energy metabolism and drug efflux in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2014; 58:2491-503. [PMID: 24614376 PMCID: PMC3993223 DOI: 10.1128/aac.02293-13] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The inherent drug susceptibility of microorganisms is determined by multiple factors, including growth state, the rate of drug diffusion into and out of the cell, and the intrinsic vulnerability of drug targets with regard to the corresponding antimicrobial agent. Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), remains a significant source of global morbidity and mortality, further exacerbated by its ability to readily evolve drug resistance. It is well accepted that drug resistance in M. tuberculosis is driven by the acquisition of chromosomal mutations in genes encoding drug targets/promoter regions; however, a comprehensive description of the molecular mechanisms that fuel drug resistance in the clinical setting is currently lacking. In this context, there is a growing body of evidence suggesting that active extrusion of drugs from the cell is critical for drug tolerance. M. tuberculosis encodes representatives of a diverse range of multidrug transporters, many of which are dependent on the proton motive force (PMF) or the availability of ATP. This suggests that energy metabolism and ATP production through the PMF, which is established by the electron transport chain (ETC), are critical in determining the drug susceptibility of M. tuberculosis. In this review, we detail advances in the study of the mycobacterial ETC and highlight drugs that target various components of the ETC. We provide an overview of some of the efflux pumps present in M. tuberculosis and their association, if any, with drug transport and concomitant effects on drug resistance. The implications of inhibiting drug extrusion, through the use of efflux pump inhibitors, are also discussed.
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Affiliation(s)
- Philippa A. Black
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
| | - Robin M. Warren
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
| | - Gail E. Louw
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
| | - Paul D. van Helden
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
| | - Thomas C. Victor
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa
| | - Bavesh D. Kana
- DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Howard Hughes Medical Institute, Chevy Chase, Maryland, USA
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Kuroda F, Tanabe N, Igari H, Sakurai T, Sakao S, Tada Y, Kasahara Y, Tatsumi K. Nontuberculous mycobacterium diseases and chronic thromboembolic pulmonary hypertension. Intern Med 2014; 53:2273-9. [PMID: 25318788 DOI: 10.2169/internalmedicine.53.2558] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
OBJECTIVE We aimed to investigate the incidence and clinical characteristics of nontuberculous mycobacterial (NTM) pulmonary disease as a complication of chronic thromboembolic pulmonary hypertension (CTEPH). METHODS We conducted a retrospective study of 10 cases (5.6%) complicated by NTM pulmonary disease among 180 CTEPH patients. RESULTS Isolated species of avium (n=5), kansasii (n=2), intracellulare (n=1), abscessus (n=1) and fortuitum (n=1) were detected. NTM-infected lesions were observed in 33 of 180 (18.3%) lung segments obtained from the 10 patients, and complete obstruction due to chronic pulmonary thromboembolism was detected in 65 of the 180 segmental pulmonary arteries (36.1%). The NTM-infected segments in the CTEPH patients were significantly associated with obstructed rather than unobstructed pulmonary artery segments [25 of 65 (38.5%) vs. 8 of 115 (6.9%), p<0.01]. Cavitary, nodular, ectatic and ground-glass lesions were seen in 14, 22, seven and four of the 180 segments, respectively. Thirteen of the 14 cavitary (92.9%) lesions were located in non-perfused segments. Five patients with NTM disease underwent pulmonary endarterectomy (PEA). Of the 18 assessable NTM-infected segments in six NTM-treated patients, 17 were located in non-perfused segments and one was located in a previously perfused segment. All NTM-infected segments improved among three segments reperfused with PEA. In contrast, only eight (57.1%) NTM-infected segments improved among 14 continuously non-perfused segments. A lower body mass index was found to be a significant risk factor for NTM disease in the CTEPH patients. CONCLUSION This is the first report to document NTM-disease complications in patients with CTEPH. Reperfusion in cases of NTM lesions may improve the response to NTM drug therapy.
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Affiliation(s)
- Fuminobu Kuroda
- Department of Respiratory Medicine, Chibaken Saiseikai Narashino Hospital, Japan
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65
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Cunningham-Bussel A, Zhang T, Nathan CF. Nitrite produced by Mycobacterium tuberculosis in human macrophages in physiologic oxygen impacts bacterial ATP consumption and gene expression. Proc Natl Acad Sci U S A 2013; 110:E4256-65. [PMID: 24145454 PMCID: PMC3831502 DOI: 10.1073/pnas.1316894110] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In high enough concentrations, such as produced by inducible nitric oxide synthase (iNOS), reactive nitrogen species (RNS) can kill Mycobacterium tuberculosis (Mtb). Lesional macrophages in macaques and humans with tuberculosis express iNOS, and mice need iNOS to avoid succumbing rapidly to tuberculosis. However, Mtb's own ability to produce RNS is rarely considered, perhaps because nitrate reduction to nitrite is only prominent in axenic Mtb cultures at oxygen tensions ≤1%. Here we found that cultures of Mtb-infected human macrophages cultured at physiologic oxygen tensions produced copious nitrite. Surprisingly, the nitrite arose from the Mtb, not the macrophages. Mtb responded to nitrite by ceasing growth; elevating levels of ATP through reduced consumption; and altering the expression of 120 genes associated with adaptation to acid, hypoxia, nitric oxide, oxidative stress, and iron deprivation. The transcriptomic effect of endogenous nitrite was distinct from that of nitric oxide. Thus, whether or not Mtb is hypoxic, the host expresses iNOS, or hypoxia impairs the action of iNOS, Mtb in vivo is likely to encounter RNS by producing nitrite. Endogenous nitrite may slow Mtb's growth and prepare it to resist host stresses while the pathogen waits for immunopathology to promote its transmission.
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Affiliation(s)
| | - Tuo Zhang
- Department of Microbiology and Immunology and
- Genomics Resources Core Facility, Weill Cornell Medical College, New York, NY 10065
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McGrath M, Gey van Pittius NC, van Helden PD, Warren RM, Warner DF. Mutation rate and the emergence of drug resistance in Mycobacterium tuberculosis. J Antimicrob Chemother 2013; 69:292-302. [DOI: 10.1093/jac/dkt364] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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67
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Hong Y, Zhou X, Fang H, Yu D, Li C, Sun B. Cyclic di-GMP mediates Mycobacterium tuberculosis dormancy and pathogenecity. Tuberculosis (Edinb) 2013; 93:625-34. [PMID: 24080120 DOI: 10.1016/j.tube.2013.09.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 09/04/2013] [Accepted: 09/06/2013] [Indexed: 11/27/2022]
Abstract
Dormancy of Mycobacterium tuberculosis is likely to be a major cause of extended chemotherapeutic regimens and wide prevalence of tuberculosis. The molecular mechanisms underlying M. tuberculosis dormancy are not well understood. In this study, single-copy genes responsible for synthesis (dgc) and degradation (pde) of the ubiquitous bacterial second messenger, cyclic di-GMP (c-di-GMP), were deleted in the virulent M. tuberculosis strain H37Rv to generate dgc(mut) and Δpde, respectively. Under aerobic growth conditions, the two mutants and wild-type cells showed similar phenotypes. However, dgc(mut) and Δpde exhibited increased and reduced dormancy, respectively, in both anaerobiosis-triggered and vitamin C-triggered in vitro dormancy models, as determined by survival and growth recovery from dormancy. The transcriptomes of aerobic cultures of dgc(mut) and wild-type H37Rv exhibited no difference, whereas those of anaerobic cultures showed a significant difference with 61 genes that are not a part of the dosR regulon. Furthermore, Δpde but not dgc(mut) showed decreased infectivity with human THP-1 cells. Δpde also showed attenuated pathogenicity in a C57BL/6 mouse infection model. These findings are explained by c-di-GMP-mediated signaling negatively regulating M. tuberculosis dormancy and pathogenicity.
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Affiliation(s)
- Yuzhi Hong
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, China
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68
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Adaptation of mycobacteria on solid, egg-based media to anaerobic conditions and characterization of their diagnostic phenotypes. J UOEH 2013; 35:109-17. [PMID: 23774654 DOI: 10.7888/juoeh.35.109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent evidence indicates that human pulmonary tuberculous granulomas are hypoxic, and a related dormancy model has been established for Mycobacterium tuberculosis using liquid media in tightly sealed tubes. In the present study, we examined the growth capacity of various mycobacterial species on solid, egg-based media under oxygen-limited conditions. During primary anaerobic cultivation on an Ogawa egg-based medium, all of the inoculated mycobacterial strains persisted for 10 weeks without detectable colony formation on the surface of the medium. Because these anaerobic cultures were restored and possessed the capacity to grow within 3 weeks following transfer to microaerobic conditions (5% or 10% oxygen tension), it was evident that the organisms persisted in a non-replicative dormant state as seen with anaerobic cultures in liquid media. The colonies grown under microaerobic conditions were also capable of growth under anaerobic conditions. Anaerobic growth could be observed only when the microaerobically grown colonies were subcultured under anaerobic conditions, suggesting that preliminary adaptation to the environment under reduced oxygen tensions is an essential process to enable growth under anaerobic conditions. A similar mode of anaerobic growth on slants of an egg-based medium was also observed with clinical isolates of M. tuberculosis. All of the clones that were adapted to grow in the anaerobic environments retained their species-specific colonial morphologic features, while, among the biochemical characteristics tested, heat-stable catalase activity and niacin accumulation in the medium disappeared during adaptation to anaerobic growth. Based on these results, we conclude that egg-based media actively support the anaerobiosis of mycobacteria exhibiting either a non-replicative dormant state or anaerobic growth, both of which are associated with latency and reactivation of tuberculosis. It was also evident that the use of egg-based media would be of great advantage in the diagnostic characterization of the reactivated clones of mycobacteria.
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69
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Jung JY, Madan-Lala R, Georgieva M, Rengarajan J, Sohaskey CD, Bange FC, Robinson CM. The intracellular environment of human macrophages that produce nitric oxide promotes growth of mycobacteria. Infect Immun 2013; 81:3198-209. [PMID: 23774601 PMCID: PMC3754229 DOI: 10.1128/iai.00611-13] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 06/11/2013] [Indexed: 11/20/2022] Open
Abstract
Nitric oxide (NO) is a diffusible radical gas produced from the activity of nitric oxide synthase (NOS). NOS activity in murine macrophages has a protective role against mycobacteria through generation of reactive nitrogen intermediates (RNIs). However, the production of NO by human macrophages has remained unclear due to the lack of sensitive reagents to detect NO directly. The purpose of this study was to investigate NO production and the consequence to mycobacteria in primary human macrophages. We found that Mycobacterium bovis BCG or Mycobacterium tuberculosis infection of human macrophages induced expression of NOS2 and NOS3 that resulted in detectable production of NO. Treatment with gamma interferon (IFN-γ), l-arginine, and tetrahydrobiopterin enhanced expression of NOS2 and NOS3 isoforms, as well as NO production. Both of these enzymes were shown to contribute to NO production. The maximal level of NO produced by human macrophages was not bactericidal or bacteriostatic to M. tuberculosis or BCG. The number of viable mycobacteria was increased in macrophages that produced NO, and this requires expression of nitrate reductase. An narG mutant of M. tuberculosis persisted but was unable to grow in human macrophages. Taken together, these data (i) enhance our understanding of primary human macrophage potential to produce NO, (ii) demonstrate that the level of RNIs produced in response to IFN-γ in vitro is not sufficient to limit intracellular mycobacterial growth, and (iii) suggest that mycobacteria may use RNIs to enhance their survival in human macrophages.
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Affiliation(s)
- Joo-Yong Jung
- Department of Pathology, Microbiology, and Immunology, University of South Carolina, School of Medicine, Columbia, South Carolina, USA
| | | | | | - Jyothi Rengarajan
- Emory Vaccine Center
- Division of Infectious Diseases, Emory University, Atlanta, Georgia, USA
| | - Charles D. Sohaskey
- Tuberculosis Research Laboratory, Department of Veterans Affairs Medical Center, Long Beach, California, USA
| | | | - Cory M. Robinson
- Department of Pathology, Microbiology, and Immunology, University of South Carolina, School of Medicine, Columbia, South Carolina, USA
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Sanyal S, Banerjee SK, Banerjee R, Mukhopadhyay J, Kundu M. Polyphosphate kinase 1, a central node in the stress response network of Mycobacterium tuberculosis, connects the two-component systems MprAB and SenX3-RegX3 and the extracytoplasmic function sigma factor, sigma E. MICROBIOLOGY-SGM 2013; 159:2074-2086. [PMID: 23946493 DOI: 10.1099/mic.0.068452-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Polyphosphate (poly P) metabolism regulates the stress response in mycobacteria. Here we describe the regulatory architecture of a signal transduction system involving the two-component system (TCS) SenX3-RegX3, the extracytoplasmic function sigma factor sigma E (SigE) and the poly P-synthesizing enzyme polyphosphate kinase 1 (PPK1). The ppk1 promoter of Mycobacterium tuberculosis is activated under phosphate starvation. This is attenuated upon deletion of an imperfect palindrome likely representing a binding site for the response regulator RegX3, a component of the two-component system SenX3-RegX3 that responds to phosphate starvation. Binding of phosphorylated RegX3 to this site was confirmed by electrophoretic mobility shift assay. The activity of the ppk1 promoter was abrogated upon deletion of a putative SigE binding site. Pull-down of SigE from M. tuberculosis lysates of phosphate-starved cells with a biotinylated DNA harbouring the SigE binding site confirmed the likely binding of SigE to the ppk1 promoter. In vitro transcription corroborated the involvement of SigE in ppk1 transcription. Finally, the overexpression of RseA (anti-SigE) attenuated ppk1 expression under phosphate starvation, supporting the role of SigE in ppk1 transcription. The regulatory elements identified in ppk1 transcription in this study, combined with our earlier observation that PPK1 is itself capable of regulating sigE expression via the MprAB TCS, suggest the presence of multiple positive-feedback loops in this signalling circuit. In combination with the sequestering effect of RseA, we hypothesize that this architecture could be linked to bistability in the system that, in turn, could be a key element of persistence in M. tuberculosis.
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Affiliation(s)
- Sourav Sanyal
- Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India
| | - Srijon Kaushik Banerjee
- Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India
| | - Rajdeep Banerjee
- Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India
| | - Jayanta Mukhopadhyay
- Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India
| | - Manikuntala Kundu
- Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India
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71
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DNA methylation impacts gene expression and ensures hypoxic survival of Mycobacterium tuberculosis. PLoS Pathog 2013; 9:e1003419. [PMID: 23853579 PMCID: PMC3701705 DOI: 10.1371/journal.ppat.1003419] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 04/30/2013] [Indexed: 01/07/2023] Open
Abstract
DNA methylation regulates gene expression in many organisms. In eukaryotes, DNA methylation is associated with gene repression, while it exerts both activating and repressive effects in the Proteobacteria through largely locus-specific mechanisms. Here, we identify a critical DNA methyltransferase in M. tuberculosis, which we term MamA. MamA creates N6-methyladenine in a six base pair recognition sequence present in approximately 2,000 copies on each strand of the genome. Loss of MamA reduces the expression of a number of genes. Each has a MamA site located at a conserved position relative to the sigma factor −10 binding site and transcriptional start site, suggesting that MamA modulates their expression through a shared, not locus-specific, mechanism. While strains lacking MamA grow normally in vitro, they are attenuated in hypoxic conditions, suggesting that methylation promotes survival in discrete host microenvironments. Interestingly, we demonstrate strikingly different patterns of DNA methyltransferase activity in different lineages of M. tuberculosis, which have been associated with preferences for distinct host environments and different disease courses in humans. Thus, MamA is the major functional adenine methyltransferase in M. tuberculosis strains of the Euro-American lineage while strains of the Beijing lineage harbor a point mutation that largely inactivates MamA but possess a second functional DNA methyltransferase. Our results indicate that MamA influences gene expression in M. tuberculosis and plays an important but strain-specific role in fitness during hypoxia. Tuberculosis is a disease with a devastating impact on public health, killing over 1.5 million people each year around the globe. Tuberculosis is caused by the bacterium Mycobacterium tuberculosis, which over millennia has evolved the ability to survive and persist for decades in the harsh environment inside its human host. Regulation of gene expression is critical for adaptation to stressful conditions. To successfully tackle M. tuberculosis, we therefore need to understand how it regulates its genes and responds to environmental stressors. In this work, we report the first investigation of the role of DNA methylation in gene regulation and stress response in M. tuberculosis. We have found that DNA methylation is important for survival of hypoxia, a stress condition present in human infections, and furthermore that DNA methylation affects the expression of several genes. In contrast to methylation-regulation systems reported in other bacteria, in which the effects of methylation vary from one gene to the next, M. tuberculosis appears to use a concerted mechanism to influence multiple genes. Our findings identify a novel mechanism by which M. tuberculosis modulates gene expression in response to stress.
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72
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Potent rifamycin-sparing regimen cures guinea pig tuberculosis as rapidly as the standard regimen. Antimicrob Agents Chemother 2013; 57:3910-6. [PMID: 23733473 DOI: 10.1128/aac.00761-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Strategies involving new drug combinations, as well as new uses of existing drugs, are urgently needed to reduce the time required to cure patients with drug-sensitive or multidrug-resistant (MDR) tuberculosis (TB). We compared the sterilizing activity of the standard first-line antitubercular regimen, rifampin-isoniazid-pyrazinamide (RHZ), with that of the novel regimen PA-824-moxifloxacin-pyrazinamide (PaMZ), which is currently being studied in clinical trials (NCT01498419), in the guinea pig model of chronic TB infection, in which animals develop necrotic granulomas histologically resembling their human counterparts. Guinea pigs were aerosol infected with ~2 log10 bacilli of wild-type Mycobacterium tuberculosis H37Rv, and antibiotic treatment was initiated 6 weeks after infection. Separate groups of animals received RHZ, PaMZ, or single or two-drug components of the latter regimen administered at human-equivalent doses 5 days/week for a total of 8 weeks. Relapse rates were assessed 3 months after discontinuation of treatment to determine the sterilizing activity of each combination regimen. PaMZ given at human-equivalent doses was safe and well tolerated for the entire treatment period and rendered guinea pig lungs culture negative more rapidly than RHZ did. After 1 month of treatment, 80% and 50% of animals in the RHZ and PaMZ groups, respectively, had lung culture-positive relapse. Both combination regimens prevented microbiological relapse when administered for a total of 2 months. Our data support the use of PaMZ as a novel isoniazid- and rifamycin-sparing regimen suitable for treatment of both drug-sensitive TB and MDR-TB.
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73
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Multifunctional essentiality of succinate metabolism in adaptation to hypoxia in Mycobacterium tuberculosis. Proc Natl Acad Sci U S A 2013; 110:6554-9. [PMID: 23576728 DOI: 10.1073/pnas.1219375110] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mycobacterium tuberculosis is a chronic, facultative intracellular pathogen that spends the majority of its decades-long life cycle in a non- or slowly replicating state. However, the bacterium remains poised to resume replicating so that it can transmit itself to a new host. Knowledge of the metabolic adaptations used to facilitate entry into and exit from nonreplicative states remains incomplete. Here, we apply (13)C-based metabolomic profiling to characterize the activity of M. tuberculosis tricarboxylic acid cycle during adaptation to and recovery from hypoxia, a physiologically relevant condition associated with nonreplication. We show that, as M. tuberculosis adapts to hypoxia, it slows and remodels its tricarboxylic acid cycle to increase production of succinate, which is used to flexibly sustain membrane potential, ATP synthesis, and anaplerosis, in response to varying degrees of O2 limitation and the presence or absence of the alternate electron acceptor nitrate. This remodeling is mediated by the bifunctional enzyme isocitrate lyase acting in a noncanonical role distinct from fatty acid catabolism. Isocitrate lyase-dependent production of succinate affords M. tuberculosis with a unique and bioenergetically efficient metabolic means of entry into and exit from hypoxia-induced quiescence.
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74
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Abstract
Tuberculosis (TB) develops in 5% to 10% of people infected with Mycobacterium tuberculosis (M.tb), but we do not understand how TB develops. CBA/J mice may model these events, as sick mice share features with TB patients, including weight loss, M.tb growth, extensive granulomatous infiltrates, neutrophils, necrosis, and fibrosis. Here, M.tb-infected CBA/J mice were categorized clinically: those with no signs or those with 10% weight loss to determine whether clinical state was associated with lung lesions. The type and distribution of infiltrates (granulomatous with lymphoid aggregates and scattered neutrophils) were similar in mice with weight loss and in mice with no signs. The amount of infiltration and neutrophil foci were higher in mice with weight loss than in mice with no clinical signs. Necrosis and fibrosis were only identified in mice that lost weight. Our results suggest that CBA/J mice may be useful to determine if and how neutrophils contribute to TB disease progression in mouse models.
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Affiliation(s)
- S Major
- Department of Infectious Disease and Global Health, Tufts University, 200 Westboro Rd, Bldg 20, Grafton, MA 01536, USA.
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75
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Klinkenberg LG, Karakousis PC. Rv1894c is a novel hypoxia-induced nitronate monooxygenase required for Mycobacterium tuberculosis virulence. J Infect Dis 2013; 207:1525-34. [PMID: 23408846 DOI: 10.1093/infdis/jit049] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Tuberculosis is difficult to cure, requiring a minimum of 6 months of treatment with multiple antibiotics. Small numbers of organisms are able to tolerate the antibiotics and persist in the lungs of infected humans, but they still require some metabolic activity to survive. We studied the role of the hypoxia-induced Rv1894c gene in Mycobacterium tuberculosis virulence in guinea pigs, which develop hypoxic, necrotic granulomas histologically resembling those in humans and found this gene to be necessary for full bacillary growth and survival. We characterized the function of the encoded enzyme as a nitronate monooxygenase, which is needed to prevent the buildup of toxic products during hypoxic metabolism and is negatively regulated by the transcriptional repressor KstR. Future studies will focus on developing small-molecule inhibitors that target Rv1894c and its homologs, with the goal of killing persistent bacteria, thereby shortening the time needed to treat tuberculosis.
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Affiliation(s)
- Lee G Klinkenberg
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231-0001, USA.
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76
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Phong WY, Lin W, Rao SPS, Dick T, Alonso S, Pethe K. Characterization of phosphofructokinase activity in Mycobacterium tuberculosis reveals that a functional glycolytic carbon flow is necessary to limit the accumulation of toxic metabolic intermediates under hypoxia. PLoS One 2013; 8:e56037. [PMID: 23409118 PMCID: PMC3567006 DOI: 10.1371/journal.pone.0056037] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Accepted: 01/04/2013] [Indexed: 11/18/2022] Open
Abstract
Metabolic versatility has been increasingly recognized as a major virulence mechanism that enables Mycobacterium tuberculosis to persist in many microenvironments encountered in its host. Glucose is one of the most abundant carbon sources that is exploited by many pathogenic bacteria in the human host. M. tuberculosis has an intact glycolytic pathway that is highly conserved in all clinical isolates sequenced to date suggesting that glucose may represent a non-negligible source of carbon and energy for this pathogen in vivo. Fructose-6-phosphate phosphorylation represents the key-committing step in glycolysis and is catalyzed by a phosphofructokinase (PFK) activity. Two genes, pfkA and pfkB have been annotated to encode putative PFK in M. tuberculosis. Here, we show that PFKA is the sole PFK enzyme in M. tuberculosis with no functional redundancy with PFKB. PFKA is required for growth on glucose as sole carbon source. In co-metabolism experiments, we report that disruption of the glycolytic pathway at the PFK step results in intracellular accumulation of sugar-phosphates that correlated with significant impairment of the cell viability. Concomitantly, we found that the presence of glucose is highly toxic for the long-term survival of hypoxic non-replicating mycobacteria, suggesting that accumulation of glucose-derived toxic metabolites does occur in the absence of sustained aerobic respiration. The culture medium traditionally used to study the physiology of hypoxic mycobacteria is supplemented with glucose. In this medium, M. tuberculosis can survive for only 7-10 days in a true non-replicating state before death is observed. By omitting glucose in the medium this period could be extended for up to at least 40 days without significant viability loss. Therefore, our study suggests that glycolysis leads to accumulation of glucose-derived toxic metabolites that limits long-term survival of hypoxic mycobacteria. Such toxic effect is exacerbated when the glycolytic pathway is disrupted at the PKF step.
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Affiliation(s)
- Wai Yee Phong
- Novartis Institute for Tropical Diseases, Singapore, Singapore
- Department of Microbiology, Immunology Programme, Yong Loo Lin School of Medicine, Life Sciences Institute, National University of Singapore, Singapore, Singapore
| | - Wenwei Lin
- Department of Microbiology, Immunology Programme, Yong Loo Lin School of Medicine, Life Sciences Institute, National University of Singapore, Singapore, Singapore
- Singapore-Massachusetts Institute of Technology Alliance for Research and Technology (SMART), CREATE NUS Campus, Singapore, Singapore
| | | | - Thomas Dick
- Novartis Institute for Tropical Diseases, Singapore, Singapore
| | - Sylvie Alonso
- Department of Microbiology, Immunology Programme, Yong Loo Lin School of Medicine, Life Sciences Institute, National University of Singapore, Singapore, Singapore
- Singapore-Massachusetts Institute of Technology Alliance for Research and Technology (SMART), CREATE NUS Campus, Singapore, Singapore
| | - Kevin Pethe
- Novartis Institute for Tropical Diseases, Singapore, Singapore
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Williams M, Mizrahi V, Kana BD. Molybdenum cofactor: a key component of Mycobacterium tuberculosis pathogenesis? Crit Rev Microbiol 2013; 40:18-29. [PMID: 23317461 DOI: 10.3109/1040841x.2012.749211] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mycobacterium tuberculosis (Mtb) and other members of the Mtb complex possess an expanded complement of genes for the biosynthesis of molybdenum cofactor (MoCo), a tricyclic pterin molecule that is covalently attached to molybdate. This cofactor allows the redox properties of molybdenum to be harnessed by enzymes in order to catalyze redox reactions in carbon, nitrogen and sulfur metabolism. In this article, we summarize recent advances in elucidating the MoCo biosynthetic pathway in Mtb and highlight the evidence implicating the biosynthesis of this cofactor, as well as the enzymes that depend upon it for activity, in Mtb pathogenesis.
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Affiliation(s)
- Monique Williams
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, Division of Medical Microbiology, Faculty of Health Sciences , University of Cape Town
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78
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The tuberculous granuloma: an unsuccessful host defence mechanism providing a safety shelter for the bacteria? Clin Dev Immunol 2012; 2012:139127. [PMID: 22811737 PMCID: PMC3395138 DOI: 10.1155/2012/139127] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 04/16/2012] [Accepted: 04/30/2012] [Indexed: 12/16/2022]
Abstract
One of the main features of the immune response to M. Tuberculosis is the formation of an organized structure called granuloma. It consists mainly in the recruitment at the infectious stage of macrophages, highly differentiated cells such as multinucleated giant cells, epithelioid cells and Foamy cells, all these cells being surrounded by a rim of lymphocytes. Although in the first instance the granuloma acts to constrain the infection, some bacilli can actually survive inside these structures for a long time in a dormant state. For some reasons, which are still unclear, the bacilli will reactivate in 10% of the latently infected individuals, escape the granuloma and spread throughout the body, thus giving rise to clinical disease, and are finally disseminated throughout the environment. In this review we examine the process leading to the formation of the granulomatous structures and the different cell types that have been shown to be part of this inflammatory reaction. We also discuss the different in vivo and in vitro models available to study this fascinating immune structure.
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79
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Rifapentine is not more active than rifampin against chronic tuberculosis in guinea pigs. Antimicrob Agents Chemother 2012; 56:3726-31. [PMID: 22547623 DOI: 10.1128/aac.00500-12] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Rifamycins are key sterilizing drugs in the current treatment of active tuberculosis (TB). Daily dosing of rifapentine (P), a potent rifamycin with high intracellular accumulation, in place of rifampin (R) in the standard antitubercular regimen significantly shortens the duration of treatment needed to prevent relapse in a murine model of active TB. We undertook the current study to compare directly the activities of human-equivalent doses of P and R in a guinea pig model of chronic TB, in which bacilli are predominantly extracellular within human-like necrotic granulomas. Hartley strain guinea pigs were aerosol infected with ~200 bacilli of Mycobacterium tuberculosis H37Rv, and treatment given 5 days/week was initiated 6 weeks later. R at 100 mg/kg of body weight and P at 100 mg/kg were given orally alone or in combination with isoniazid (H) at 60 mg/kg and pyrazinamide (Z) at 300 mg/kg. Culture-positive relapse was assessed in subgroups of guinea pigs after completion of 1 and 2 months of treatment. Human-equivalent doses of R and P showed equivalent bactericidal activity when used alone and in combination therapy. In guinea pigs treated with rifampin, isoniazid, and pyrazinamide (RHZ) or PHZ, microbiological relapse occurred in the lungs of 8/10 animals treated for 1 month and in 0/10 animals treated for 2 months. Substitution of P for R in the standard antitubercular regimen did not shorten the time to cure in this guinea pig model of chronic TB. Data from ongoing clinical trials comparing the activity of these two drugs are awaited to determine the relevance of the guinea pig TB model in preclinical drug screening.
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80
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Evaluation of a mouse model of necrotic granuloma formation using C3HeB/FeJ mice for testing of drugs against Mycobacterium tuberculosis. Antimicrob Agents Chemother 2012; 56:3181-95. [PMID: 22470120 DOI: 10.1128/aac.00217-12] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Persistence of Mycobacterium tuberculosis remains a significant challenge for the effective treatment of tuberculosis in humans. In animals that develop necrotic lung lesions following infection with M. tuberculosis, drug-tolerant bacilli are present and persist in an extracellular microenvironment within the necrotic cores. In this study, we examined the efficacy of drug treatment in C3HeB/FeJ (Kramnik) mice that develop lesions with liquefactive necrosis, in comparison to BALB/c mice that develop nonnecrotic lesions following aerosol challenge. To accomplish this, Kramnik and BALB/c mice were infected by aerosol with M. tuberculosis and treated for 7 to 8 weeks with monotherapy using drugs with different modes of action. The efficacy of drug therapy was quantified by enumeration of bacterial load. The progression of disease and location and distribution of bacilli within lesions were visualized using various staining techniques. In the late stages of infection, Kramnik mice developed fibrous encapsulated lung lesions with central liquefactive necrosis containing abundant extracellular bacilli, whereas BALB/c mice formed nonnecrotic lesions with primarily intracellular bacilli. Necrotic lesions in Kramnik mice showed evidence of hypoxia by pimonidazole staining. Kramnik mice were significantly more refractory to drug therapy, especially for pyrazinamide. Metronidazole showed no bactericidal activity in either model. There were significantly higher numbers of drug-resistant colonies isolated from the Kramnik mice compared to BALB/c mice. These results suggest that the Kramnik mouse model will be a valuable model to test antituberculosis drugs, especially against bacilli that persist within necrotic lesions.
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81
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Nickel D, Busch M, Mayer D, Hagemann B, Knoll V, Stenger S. Hypoxia Triggers the Expression of Human β Defensin 2 and Antimicrobial Activity againstMycobacterium tuberculosisin Human Macrophages. THE JOURNAL OF IMMUNOLOGY 2012; 188:4001-7. [DOI: 10.4049/jimmunol.1100976] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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82
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Chuquimia OD, Petursdottir DH, Rahman MJ, Hartl K, Singh M, Fernández C. The role of alveolar epithelial cells in initiating and shaping pulmonary immune responses: communication between innate and adaptive immune systems. PLoS One 2012; 7:e32125. [PMID: 22393384 PMCID: PMC3290547 DOI: 10.1371/journal.pone.0032125] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 01/19/2012] [Indexed: 11/19/2022] Open
Abstract
Macrophages and dendritic cells have been recognized as key players in the defense against mycobacterial infection. However, more recently, other cells in the lungs such as alveolar epithelial cells (AEC) have been found to play important roles in the defense and pathogenesis of infection. In the present study we first compared AEC with pulmonary macrophages (PuM) isolated from mice in their ability to internalize and control Bacillus Calmette-Guérin (BCG) growth and their capacity as APCs. AEC were able to internalize and control bacterial growth as well as present antigen to primed T cells. Secondly, we compared both cell types in their capacity to secrete cytokines and chemokines upon stimulation with various molecules including mycobacterial products. Activated PuM and AEC displayed different patterns of secretion. Finally, we analyzed the profile of response of AEC to diverse stimuli. AEC responded to both microbial and internal stimuli exemplified by TLR ligands and IFNs, respectively. The response included synthesis by AEC of several factors, known to have various effects in other cells. Interestingly, TNF could stimulate the production of CCL2/MCP-1. Since MCP-1 plays a role in the recruitment of monocytes and macrophages to sites of infection and macrophages are the main producers of TNF, we speculate that both cell types can stimulate each other. Also, another cell-cell interaction was suggested when IFNs (produced mainly by lymphocytes) were able to induce expression of chemokines (IP-10 and RANTES) by AEC involved in the recruitment of circulating lymphocytes to areas of injury, inflammation, or viral infection. In the current paper we confirm previous data on the capacity of AEC regarding internalization of mycobacteria and their role as APC, and extend the knowledge of AEC as a multifunctional cell type by assessing the secretion of a broad array of factors in response to several different types of stimuli.
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Affiliation(s)
- Olga D Chuquimia
- Department of Immunology, Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
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83
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Harper J, Skerry C, Davis SL, Tasneen R, Weir M, Kramnik I, Bishai WR, Pomper MG, Nuermberger EL, Jain SK. Mouse model of necrotic tuberculosis granulomas develops hypoxic lesions. J Infect Dis 2012; 205:595-602. [PMID: 22198962 PMCID: PMC3266133 DOI: 10.1093/infdis/jir786] [Citation(s) in RCA: 178] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 09/23/2011] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Preclinical evaluation of tuberculosis drugs is generally limited to mice. However, necrosis and hypoxia, key features of human tuberculosis lesions, are lacking in conventional mouse strains. METHODS We used C3HeB/FeJ mice, which develop necrotic lesions in response to Mycobacterium tuberculosis infection. Positron emission tomography in live infected animals, postmortem pimonidazole immunohistochemistry, and bacterial gene expression analyses were used to assess whether tuberculosis lesions in C3HeB/FeJ are hypoxic. Efficacy of combination drug treatment, including PA-824, active against M. tuberculosis under hypoxic conditions, was also evaluated. RESULTS Tuberculosis lesions in C3HeB/FeJ (but not BALB/c) were found to be hypoxic and associated with up-regulation of known hypoxia-associated bacterial genes (P < .001). Contrary to sustained activity reported elsewhere in BALB/c mice, moxifloxacin and pyrazinamide (MZ) combination was not bactericidal beyond 3 weeks in C3HeB/FeJ. Although PA-824 added significant activity, the novel combination of PA-824 and MZ was less effective than the standard first-line regimen in C3HeB/FeJ. CONCLUSIONS We demonstrate that tuberculosis lesions in C3HeB/FeJ are hypoxic. Activities of some key tuberculosis drug regimens in development are represented differently in C3HeB/FeJ versus BALB/c mice. Because C3HeB/FeJ display key features of human tuberculosis, this strain warrants evaluation as a more pathologically relevant model for preclinical studies.
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Affiliation(s)
- Jamie Harper
- Department of Medicine, Center for Infection and Inflammation Imaging Research
- Department of Medicine, Center for Tuberculosis Research
- Department of Pediatrics
| | - Ciaran Skerry
- Department of Medicine, Center for Tuberculosis Research
- Department of Pediatrics
| | - Stephanie L. Davis
- Department of Medicine, Center for Infection and Inflammation Imaging Research
- Department of Medicine, Center for Tuberculosis Research
- Department of Pediatrics
| | - Rokeya Tasneen
- Department of Medicine, Center for Tuberculosis Research
| | - Mariah Weir
- Department of Medicine, Center for Infection and Inflammation Imaging Research
- Department of Medicine, Center for Tuberculosis Research
- Department of Pediatrics
| | - Igor Kramnik
- National Emerging Infectious Diseases Laboratories, Boston University School of Medicine, Massachusetts
| | | | - Martin G. Pomper
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | | | - Sanjay K. Jain
- Department of Medicine, Center for Infection and Inflammation Imaging Research
- Department of Medicine, Center for Tuberculosis Research
- Department of Pediatrics
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84
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Abstract
Mycobacterium tuberculosis is an old enemy of the human race, with evidence of infection observed as early as 5000 years ago. Although more host-restricted than Mycobacterium bovis, which can infect all warm-blooded vertebrates, M. tuberculosis can infect, and cause morbidity and mortality in, several veterinary species as well. As M. tuberculosis is one of the earliest described bacterial pathogens, the literature describing this organism is vast and overwhelming. This review strives to distill what is currently known about this bacterium and the disease it causes for the veterinary pathologist.
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Affiliation(s)
- K Sakamoto
- Department of Pathology, College of Veterinary Medicine, University of Georgia, 501 D. W. Brooks Dr, Athens, GA 30602-7388, USA.
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85
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Ehrt S, Rhee K. Mycobacterium tuberculosis metabolism and host interaction: mysteries and paradoxes. Curr Top Microbiol Immunol 2012; 374:163-88. [PMID: 23242856 DOI: 10.1007/82_2012_299] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Metabolism is a widely recognized facet of all host-pathogen interactions. Knowledge of its roles in pathogenesis, however, remains comparatively incomplete. Existing studies have emphasized metabolism as a cell autonomous property of pathogens used to fuel replication in a quantitative, rather than qualitatively specific, manner. For Mycobacterium tuberculosis, however, matters could not be more different. M. tuberculosis is a chronic facultative intracellular pathogen that resides in humans as its only known host. Within humans, M. tuberculosis resides chiefly within the macrophage phagosome, the cell type, and compartment most committed to its eradication. M. tuberculosis has thus evolved its metabolic network to both maintain and propagate its survival as a species within a single host. The specific ways in which its metabolic network serves these distinct, through interdependent, functions, however, remain incompletely defined. Here, we review existing knowledge of the M. tuberculosis-host interaction, highlighting the distinct phases of its natural life cycle and the diverse microenvironments encountered therein.
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Affiliation(s)
- Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, USA,
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86
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Abstract
Mycobacterium tuberculosis (Mtb) is a metabolically flexible pathogen
that has the extraordinary ability to sense and adapt to the continuously changing host
environment experienced during decades of persistent infection. Mtb is
continually exposed to endogenous reactive oxygen species (ROS) as part of normal aerobic
respiration, as well as exogenous ROS and reactive nitrogen species (RNS) generated by the
host immune system in response to infection. The magnitude of tuberculosis (TB) disease is
further amplified by exposure to xenobiotics from the environment such as cigarette smoke
and air pollution, causing disruption of the intracellular
prooxidant–antioxidant balance. Both oxidative and reductive stresses induce
redox cascades that alter Mtb signal transduction, DNA and RNA synthesis,
protein synthesis and antimycobacterial drug resistance. As reviewed in this article,
Mtb has evolved specific mechanisms to protect itself against
endogenously produced oxidants, as well as defend against host and environmental oxidants
and reductants found specifically within the microenvironments of the lung. Maintaining an
appropriate redox balance is critical to the clinical outcome because several
antimycobacterial prodrugs are only effective upon bioreductive activation. Proper
homeostasis of oxido-reductive systems is essential for Mtb survival,
persistence and subsequent reactivation. The progress and remaining deficiencies in
understanding Mtb redox homeostasis are also discussed.
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87
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Khan A, Sarkar D. Nitrate reduction pathways in mycobacteria and their implications during latency. MICROBIOLOGY-SGM 2011; 158:301-307. [PMID: 22174380 DOI: 10.1099/mic.0.054759-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Mycobacterial persistence has gained a lot of attention with respect to developing novel antitubercular drugs, which could drastically reduce the duration of tuberculosis (TB) therapy. A better understanding of the physiology of Mycobacterium tuberculosis, and of the metabolic state of the bacillus during the latent period, is a primary need in finding drug targets against persistent TB. Recent biochemical and genetic studies of nitrate reduction in mycobacteria have revealed the roles of distinct proteins and enzymes involved in the pathway. The differential degree of nitrate reduction among pathogenic and non-pathogenic mycobacterial species, and its regulation during oxygen and nutrient limitation, suggest a link between nitrate reduction pathways and latency. The respiratory and assimilatory reduction of nitrate in mycobacteria may be interconnected to facilitate rapid adaptation to changing oxygen and/or nitrogen conditions, increasing metabolic flexibility for survival in the hostile host environment. This review summarizes the nitrate metabolic pathways operative in mycobacteria to provide an insight into the mechanisms that M. tuberculosis has evolved to adapt successfully to the host environment.
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Affiliation(s)
- Arshad Khan
- Department of Pathology and Laboratory Medicine, University of Texas, Health Science Center at Houston, Medical School, Houston, TX 77030, USA
| | - Dhiman Sarkar
- Combi Chem-Bio Resource Center, National Chemical Laboratory, Dr Homi Bhabha Road, Pune, Maharashtra 411008, India
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88
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Nandi B, Behar SM. Regulation of neutrophils by interferon-γ limits lung inflammation during tuberculosis infection. ACTA ACUST UNITED AC 2011; 208:2251-62. [PMID: 21967766 PMCID: PMC3201199 DOI: 10.1084/jem.20110919] [Citation(s) in RCA: 261] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
IFN-γ functions to suppress neutrophil accumulation in the lungs of mice infected with M. tuberculosis, in part by suppressing IL-17 production from CD4+ T cells. Resistance to Mycobacterium tuberculosis requires the host to restrict bacterial replication while preventing an over-exuberant inflammatory response. Interferon (IFN) γ is crucial for activating macrophages and also regulates tissue inflammation. We dissociate these two functions and show that IFN-γ−/− memory CD4+ T cells retain their antimicrobial activity but are unable to suppress inflammation. IFN-γ inhibits CD4+ T cell production of IL-17, which regulates neutrophil recruitment. In addition, IFN-γ directly inhibits pathogenic neutrophil accumulation in the infected lung and impairs neutrophil survival. Regulation of neutrophils is important because their accumulation is detrimental to the host. We suggest that neutrophilia during tuberculosis indicates failed Th1 immunity or loss of IFN-γ responsiveness. These results establish an important antiinflammatory role for IFN-γ in host protection against tuberculosis.
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Affiliation(s)
- Bisweswar Nandi
- Division of Rheumatology, Immunology, and Allergy, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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89
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Abstract
The mechanisms of latency and the causes of reactivation of Mycobacterium tuberculosis remain poorly understood; an important reason for this gap in knowledge is the absence of a standardized animal model of latent tuberculosis infection (LTBI). A complete LTBI model should incorporate 2 aspects of LTBI: a persistent infection model with a low bacterial load and a latent infection model that is modified from the Cornell model. Many parameters must be carefully considered to establish an LTBI model, including the inoculating dose, the route of infection, the time interval between infection and the initiation of antibiotic therapy, and the genetic background of the host animal. The responsiveness of this mouse model of LTBI can be assessed through the integrated use of indices, including Karnofsky performance status, bacterial load in spleen and lungs, induced levels of interferon-gamma and tumour necrosis factor-alpha, expression of interleukin (IL)-10 and IL-4 in tissues, specific antigen load in organs, time required for hormone-induced TB relapse, expression level of dormancy genes, and CD4 T-cell count.
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Affiliation(s)
- Changhong Shi
- Division of Infection and Immunology, Research Center of Laboratory Animals, Fourth Military Medical University, 17 Changle West Road, Xi'an 710032, Shaanxi Province, China.
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90
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Mukherjee T, Boshoff H. Nitroimidazoles for the treatment of TB: past, present and future. Future Med Chem 2011; 3:1427-54. [PMID: 21879846 PMCID: PMC3225966 DOI: 10.4155/fmc.11.90] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Tuberculosis remains a leading cause of death resulting from an infectious agent, and the spread of multi- and extensively drug-resistant strains of Mycobacterium tuberculosis poses a threat to management of global health. New drugs that effectively shorten the duration of treatment and are active against drug-resistant strains of this pathogen are urgently required to develop effective chemotherapies to combat this disease. Two nitroimidazoles, PA-824 and OPC-67683, are currently in Phase II clinical trials for the treatment of TB and the outcome of these may determine the future directions of drug development for anti-tubercular nitroimidazoles. In this review we summarize the development of these nitroimidazoles and alternative analogs in these series that may offer attractive alternatives to PA-824 and OPC-67683 for further development in the drug-discovery pipeline. Lastly, the potential pitfalls in the development of nitroimidazoles as drugs for TB are discussed.
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Affiliation(s)
- Tathagata Mukherjee
- Tuberculosis Research Section, LCID, NIAID, NIH, Room 2W20G, Building 33, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Helena Boshoff
- Tuberculosis Research Section, LCID, NIAID, NIH, Room 2W20G, Building 33, 9000 Rockville Pike, Bethesda, MD 20892, USA
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91
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Somashekar BS, Amin AG, Rithner CD, Troudt J, Basaraba R, Izzo A, Crick DC, Chatterjee D. Metabolic Profiling of Lung Granuloma in Mycobacterium tuberculosis Infected Guinea Pigs: Ex vivo 1H Magic Angle Spinning NMR Studies. J Proteome Res 2011; 10:4186-95. [DOI: 10.1021/pr2003352] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- B. S. Somashekar
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Anita G. Amin
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Christopher D. Rithner
- Central Instrument Facility, Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - JoLynn Troudt
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Randall Basaraba
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Angelo Izzo
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Dean C. Crick
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
| | - Delphi Chatterjee
- Department of Microbiology, Immunology and Pathology, Colorado State University, Campus Delivery 1682, Fort Collins, Colorado 80523-1682, United States
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92
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Dorhoi A, Reece ST, Kaufmann SHE. For better or for worse: the immune response against Mycobacterium tuberculosis balances pathology and protection. Immunol Rev 2011; 240:235-51. [PMID: 21349097 DOI: 10.1111/j.1600-065x.2010.00994.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tuberculosis (TB) is a complex disease, and the success of the bacterium as an intracellular pathogen is the outcome of its close and longstanding coevolution with the mammalian host. The dialogue between Mycobacterium tuberculosis and the host is becoming understandable at the molecular, cellular, and tissue level. This has led to the elucidation of the (i) interaction between pattern recognition receptors and pathogen-associated molecular patterns, (ii) cross-talk between immune cells, and (iii) mechanisms underlying granuloma development. Disease as an eventual but not a necessary consequence of infection results from a sensitive balance between protective immunity and destructive pathology. Early events, governed largely by conserved mechanisms of host recognition, impact not only on type and course of adaptive immunity but also on lung parenchymal function. New interpretations of how these responses shape the lung environment and direct granuloma development emphasize that the disease results from pathologic consequences of non-resolving inflammation. We review recent advances in TB research within the context of this ambitious view of TB.
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Affiliation(s)
- Anca Dorhoi
- Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany
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93
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Ahmad Z, Fraig MM, Pinn ML, Tyagi S, Nuermberger EL, Grosset JH, Karakousis PC. Effectiveness of tuberculosis chemotherapy correlates with resistance to Mycobacterium tuberculosis infection in animal models. J Antimicrob Chemother 2011; 66:1560-6. [PMID: 21602551 DOI: 10.1093/jac/dkr188] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
OBJECTIVES It is widely believed that persistent Mycobacterium tuberculosis inhabits necrotic lung granulomas in humans and that the microenvironmental conditions encountered therein render the bacilli phenotypically tolerant to antibiotics, accounting for the long duration required for successful treatment of tuberculosis (TB). To validate this belief, we directly compared the activity of rifampicin/isoniazid/pyrazinamide (RHZ) against chronic TB infection in guinea pigs, which exhibit caseous granulomas histologically resembling human caseous foci, and in mice, which lack necrotic granulomas. METHODS Guinea pigs and mice were aerosol-infected with M. tuberculosis CDC1551 and twice weekly treatment with RHZ was started 4 weeks later. Culture-positive relapse was assessed in subgroups of guinea pigs after 3 months and 4 months of treatment. RESULTS All guinea pig lungs exhibited histological evidence of granulomas with central caseation, while mouse lungs exhibited cellular lesions at the initiation of antibiotic treatment. Guinea pig lungs became culture-negative after 2 months of RHZ given twice weekly at human-equivalent doses. Relapse rates in guinea pigs were 0% (0/10) both after 3 months and 4 months of treatment. In contrast, all mouse lungs remained culture-positive after 4 months of equivalent RHZ exposures. CONCLUSIONS Caseous necrosis does not reduce the sterilizing activity of the standard antituberculosis regimen of RHZ. Our findings have important implications for the use of alternative animal models in testing novel TB drug regimens and for modelling M. tuberculosis persistence.
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Affiliation(s)
- Zahoor Ahmad
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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94
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Hoff DR, Ryan GJ, Driver ER, Ssemakulu CC, De Groote MA, Basaraba RJ, Lenaerts AJ. Location of intra- and extracellular M. tuberculosis populations in lungs of mice and guinea pigs during disease progression and after drug treatment. PLoS One 2011; 6:e17550. [PMID: 21445321 PMCID: PMC3061964 DOI: 10.1371/journal.pone.0017550] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 02/08/2011] [Indexed: 11/18/2022] Open
Abstract
The lengthy treatment regimen for tuberculosis is necessary to eradicate a small sub-population of M. tuberculosis that persists in certain host locations under drug pressure. Limited information is available on persisting bacilli and their location within the lung during disease progression and after drug treatment. Here we provide a comprehensive histopathological and microscopic evaluation to elucidate the location of bacterial populations in animal models for TB drug development.To detect bacilli in tissues, a new combination staining method was optimized using auramine O and rhodamine B for staining acid-fast bacilli, hematoxylin QS for staining tissue and DAPI for staining nuclei. Bacillary location was studied in three animal models used in-house for TB drug evaluations: C57BL/6 mice, immunocompromised GKO mice and guinea pigs. In both mouse models, the bacilli were found primarily intracellularly in inflammatory lesions at most stages of disease, except for late stage GKO mice, which showed significant necrosis and extracellular bacilli after 25 days of infection. This is also the time when hypoxia was initially visualized in GKO mice by 2-piminidazole. In guinea pigs, the majority of bacteria in lungs are extracellular organisms in necrotic lesions and only few, if any, were ever visualized in inflammatory lesions. Following drug treatment in mice a homogenous bacillary reduction across lung granulomas was observed, whereas in guinea pigs the remaining extracellular bacilli persisted in lesions with residual necrosis. In summary, differences in pathogenesis between animal models infected with M. tuberculosis result in various granulomatous lesion types, which affect the location, environment and state of bacilli. The majority of M. tuberculosis bacilli in an advanced disease state were found to be extracellular in necrotic lesions with an acellular rim of residual necrosis. Drug development should be designed to target this bacillary population and should evaluate drug regimens in the appropriate animal models.
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Affiliation(s)
- Donald R. Hoff
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Gavin J. Ryan
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Emily R. Driver
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Cornelius C. Ssemakulu
- Council for Scientific and Industrial Research (CSIR), CSIR Biosciences,
Pretoria, South Africa
| | - Mary A. De Groote
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Randall J. Basaraba
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
| | - Anne J. Lenaerts
- Department of Microbiology, Immunology, and Pathology, Colorado State
University, Fort Collins, Colorado, United States of America
- * E-mail:
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95
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Farhana A, Guidry L, Srivastava A, Singh A, Hondalus MK, Steyn AJC. Reductive stress in microbes: implications for understanding Mycobacterium tuberculosis disease and persistence. Adv Microb Physiol 2011; 57:43-117. [PMID: 21078441 DOI: 10.1016/b978-0-12-381045-8.00002-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mycobacterium tuberculosis (Mtb) is a remarkably successful pathogen that is capable of persisting in host tissues for decades without causing disease. Years after initial infection, the bacilli may resume growth, the outcome of which is active tuberculosis (TB). In order to establish infection, resist host defences and re-emerge, Mtb must coordinate its metabolism with the in vivo environmental conditions and nutrient availability within the primary site of infection, the lung. Maintaining metabolic homeostasis for an intracellular pathogen such as Mtb requires a carefully orchestrated series of oxidation-reduction reactions, which, if unbalanced, generate oxidative or reductive stress. The importance of oxidative stress in microbial pathogenesis has been appreciated and well studied over the past several decades. However, the role of its counterpart, reductive stress, has been largely ignored. Reductive stress is defined as an aberrant increase in reducing equivalents, the magnitude and identity of which is determined by host carbon source utilisation and influenced by the presence of host-generated gases (e.g. NO, CO, O(2) and CO(2)). This increased reductive power must be dissipated for bacterial survival. To recycle reducing equivalents, microbes have evolved unique electron 'sinks' that are distinct for their particular environmental niche. In this review, we describe the specific mechanisms that some microbes have evolved to dispel reductive stress. The intention of this review is to introduce the concept of reductive stress, in tuberculosis research in particular, in the hope of stimulating new avenues of investigation.
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Affiliation(s)
- Aisha Farhana
- Department of Microbiology, University of Alabama at Birmingham, AL, USA
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96
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Fang X, Wallqvist A, Reifman J. Development and analysis of an in vivo-compatible metabolic network of Mycobacterium tuberculosis. BMC SYSTEMS BIOLOGY 2010; 4:160. [PMID: 21092312 PMCID: PMC3225870 DOI: 10.1186/1752-0509-4-160] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 11/23/2010] [Indexed: 11/16/2022]
Abstract
Background During infection, Mycobacterium tuberculosis confronts a generally hostile and nutrient-poor in vivo host environment. Existing models and analyses of M. tuberculosis metabolic networks are able to reproduce experimentally measured cellular growth rates and identify genes required for growth in a range of different in vitro media. However, these models, under in vitro conditions, do not provide an adequate description of the metabolic processes required by the pathogen to infect and persist in a host. Results To better account for the metabolic activity of M. tuberculosis in the host environment, we developed a set of procedures to systematically modify an existing in vitro metabolic network by enhancing the agreement between calculated and in vivo-measured gene essentiality data. After our modifications, the new in vivo network contained 663 genes, 838 metabolites, and 1,049 reactions and had a significantly increased sensitivity (0.81) in predicted gene essentiality than the in vitro network (0.31). We verified the modifications generated from the purely computational analysis through a review of the literature and found, for example, that, as the analysis suggested, lipids are used as the main source for carbon metabolism and oxygen must be available for the pathogen under in vivo conditions. Moreover, we used the developed in vivo network to predict the effects of double-gene deletions on M. tuberculosis growth in the host environment, explore metabolic adaptations to life in an acidic environment, highlight the importance of different enzymes in the tricarboxylic acid-cycle under different limiting nutrient conditions, investigate the effects of inhibiting multiple reactions, and look at the importance of both aerobic and anaerobic cellular respiration during infection. Conclusions The network modifications we implemented suggest a distinctive set of metabolic conditions and requirements faced by M. tuberculosis during host infection compared with in vitro growth. Likewise, the double-gene deletion calculations highlight the importance of specific metabolic pathways used by the pathogen in the host environment. The newly constructed network provides a quantitative model to study the metabolism and associated drug targets of M. tuberculosis under in vivo conditions.
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Affiliation(s)
- Xin Fang
- Biotechnology HPC Software Applications Institute, Telemedicine and Advanced Technology Research Center, US Army Medical Research and Materiel Command, Ft, Detrick, MD 21702, USA
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97
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Nitrate respiration protects hypoxic Mycobacterium tuberculosis against acid- and reactive nitrogen species stresses. PLoS One 2010; 5:e13356. [PMID: 21048946 PMCID: PMC2965054 DOI: 10.1371/journal.pone.0013356] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 09/10/2010] [Indexed: 12/24/2022] Open
Abstract
There are strong evidences that Mycobacterium tuberculosis survives in a non-replicating state in the absence of oxygen in closed lesions and granuloma in vivo. In addition, M. tuberculosis is acid-resistant, allowing mycobacteria to survive in acidic, inflamed lesions. The ability of M. tuberculosis to resist to acid was recently shown to contribute to the bacillus virulence although the mechanisms involved have yet to be deciphered. In this study, we report that M. tuberculosis resistance to acid is oxygen-dependent; whereas aerobic mycobacteria were resistant to a mild acid challenge (pH 5.5) as previously reported, we found microaerophilic and hypoxic mycobacteria to be more sensitive to acid. In hypoxic conditions, mild-acidity promoted the dissipation of the protonmotive force, rapid ATP depletion and cell death. Exogenous nitrate, the most effective alternate terminal electron acceptor after molecular oxygen, protected hypoxic mycobacteria from acid stress. Nitrate-mediated resistance to acidity was not observed for a respiratory nitrate reductase NarGH knock-out mutant strain. Furthermore, we found that nitrate respiration was equally important in protecting hypoxic non-replicating mycobacteria from radical nitrogen species toxicity. Overall, these data shed light on a new role for nitrate respiration in protecting M. tuberculosis from acidity and reactive nitrogen species, two environmental stresses likely encountered by the pathogen during the course of infection.
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98
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Functional analysis of molybdopterin biosynthesis in mycobacteria identifies a fused molybdopterin synthase in Mycobacterium tuberculosis. J Bacteriol 2010; 193:98-106. [PMID: 20971904 DOI: 10.1128/jb.00774-10] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Most mycobacterial species possess a full complement of genes for the biosynthesis of molybdenum cofactor (MoCo). However, a distinguishing feature of members of the Mycobacterium tuberculosis complex is their possession of multiple homologs associated with the first two steps of the MoCo biosynthetic pathway. A mutant of M. tuberculosis lacking the moaA1-moaD1 gene cluster and a derivative in which moaD2 was also deleted were significantly impaired for growth in media containing nitrate as a sole nitrogen source, indicating a reduced availability of MoCo to support the assimilatory function of the MoCo-dependent nitrate reductase, NarGHI. However, the double mutant displayed residual respiratory nitrate reductase activity, suggesting that it retains the capacity to produce MoCo. The M. tuberculosis moaD and moaE homologs were further analyzed by expressing these genes in mutant strains of M. smegmatis that lacked one or both of the sole molybdopterin (MPT) synthase-encoding genes, moaD2 and moaE2, and were unable to grow on nitrate, presumably as a result of the loss of MoCo-dependent nitrate assimilatory activity. Expression of M. tuberculosis moaD2 in the M. smegmatis moaD2 mutant and of M. tuberculosis moaE1 or moaE2 in the M. smegmatis moaE2 mutant restored nitrate assimilation, confirming the functionality of these genes in MPT synthesis. Expression of M. tuberculosis moaX also restored MoCo biosynthesis in M. smegmatis mutants lacking moaD2, moaE2, or both, thus identifying MoaX as a fused MPT synthase. By implicating multiple synthase-encoding homologs in MoCo biosynthesis, these results suggest that important cellular functions may be served by their expansion in M. tuberculosis.
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Klinkenberg LG, Lee JH, Bishai WR, Karakousis PC. The stringent response is required for full virulence of Mycobacterium tuberculosis in guinea pigs. J Infect Dis 2010; 202:1397-404. [PMID: 20863231 DOI: 10.1086/656524] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
During human latent tuberculosis infection, Mycobacterium tuberculosis likely resides within the nutrient‐starved environment of caseous lung granulomas. The stringent response alarmone (p)ppGpp is synthesized by Rel in response to nutrient starvation, thus enabling tubercle bacilli to restrict growth and shut down metabolism in a coordinated fashion. In this study, we investigated the virulence of a rel‐deficient M. tuberculosis mutant in the guinea pig model. Quantitative reverse‐transcription polymerase chain reaction was used to study the effect of (p)ppGpp deficiency on expression of key cytokine and chemokine genes in guinea pig lungs. The rel‐deficient mutant showed impaired initial growth and survival relative to the wild‐type strain. Loss of Rel was associated with the striking absence of tubercle lesions grossly and of caseous granulomas histologically. The attenuated phenotype of the rel‐deficient mutant was not associated with increased expression of genes encoding the proinflammatory cytokines interferon‐γ and tumor necrosis factor α in the lungs 28 days after infection.
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Affiliation(s)
- Lee G Klinkenberg
- Department of Medicine, Johns Hopkins University School of Medicine, Center for Tuberculosis Research, Baltimore, Maryland, USA
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Seimon TA, Kim MJ, Blumenthal A, Koo J, Ehrt S, Wainwright H, Bekker LG, Kaplan G, Nathan C, Tabas I, Russell DG. Induction of ER stress in macrophages of tuberculosis granulomas. PLoS One 2010; 5:e12772. [PMID: 20856677 PMCID: PMC2939897 DOI: 10.1371/journal.pone.0012772] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 08/26/2010] [Indexed: 12/15/2022] Open
Abstract
Background The endoplasmic reticulum (ER) stress pathway known as the Unfolded Protein Response (UPR) is an adaptive survival pathway that protects cells from the buildup of misfolded proteins, but under certain circumstances it can lead to apoptosis. ER stress has been causally associated with macrophage apoptosis in advanced atherosclerosis of mice and humans. Because atherosclerosis shares certain features with tuberculosis (TB) with regard to lesional macrophage accumulation, foam cell formation, and apoptosis, we investigated if the ER stress pathway is activated during TB infection. Principal Findings Here we show that ER stress markers such as C/EBP homologous protein (CHOP; also known as GADD153), phosphorylated inositol-requiring enzyme 1 alpha (Ire1α) and eukaryotic initiation factor 2 alpha (eIF2α), and activating transcription factor 3 (ATF3) are expressed in macrophage-rich areas of granulomas in lungs of mice infected with virulent Mycobacterium tuberculosis (Mtb). These areas were also positive for numerous apoptotic cells as assayed by TUNEL. Microarray analysis of human caseous TB granulomas isolated by laser capture microdissection reveal that 73% of genes involved in the UPR are upregulated at the mRNA transcript level. The expression of two ER stress markers, ATF3 and CHOP, were also increased in macrophages of human TB granulomas when assayed by immunohistochemistry. CHOP has been causally associated with ER stress-induced macrophage apoptosis. We found that apoptosis was more abundant in granulomas as compared to non-granulomatous tissue isolated from patients with pulmonary TB, and apoptosis correlated with CHOP expression in areas surrounding the centralized areas of caseation. Conclusions In summary, ER stress is induced in macrophages of TB granulomas in areas where apoptotic cells accumulate in mice and humans. Although macrophage apoptosis is generally thought to be beneficial in initially protecting the host from Mtb infection, death of infected macrophages in advanced granulomas might favor dissemination of the bacteria. Therefore future work is needed to determine if ER-stress is causative for apoptosis and plays a role in the host response to infection.
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Affiliation(s)
- Tracie A Seimon
- Division of Molecular Medicine, Department of Medicine, Columbia University, New York, New York, United States of America.
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