The Polyphosphate Kinase Gene ppk2 Is Required for Mycobacterium tuberculosis Inorganic Polyphosphate Regulation and Virulence

ABSTRACT The Mycobacterium tuberculosis gene Rv3232c/MT3329 (ppk2) encodes a class II polyphosphate kinase, which hydrolyzes inorganic polyphosphate (poly P) to synthesize GTP. We assessed the role of ppk2 in M. tuberculosis poly P regulation, antibiotic tolerance, and virulence. A ppk2-deficient mutant (ppk2::Tn) and its isogenic wild-type (WT) and complemented (Comp) strains were studied. For each strain, the intrabacillary poly P content, MIC of isoniazid, and growth kinetics during infection of J774 macrophages were determined. Multiplex immunobead assays were used to evaluate cytokines elaborated during macrophage infection. The requirement of ppk2 for M. tuberculosis virulence was assessed in the murine model. The ppk2::Tn mutant was found to have significantly increased poly P content and a 4-fold increase in the MIC of isoniazid relative to the WT and Comp strains. The ppk2::Tn mutant showed reduced survival at day 7 in activated and naive J774 macrophages relative to the WT. Naive ppk2::Tn mutant-infected macrophages showed increased expression of interleukin 2 (IL-2), IL-9, IL-10, IL-12p70, and gamma interferon (IFN-γ) relative to WT-infected macrophages. The ppk2::Tn mutant exhibited significantly lower lung CFU during acute murine infection compared to the control groups. ppk2 is required for control of intrabacillary poly P levels and optimal M. tuberculosis growth and survival in macrophages and mouse lungs. IMPORTANCE Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a highly successful human pathogen because it has developed mechanisms to multiply and survive in the lungs by circumventing the immune system. Identification of virulence factors responsible for M. tuberculosis growth and persistence in host tissues may assist in the development of novel strategies to treat TB. In this study, we found that the mycobacterial enzyme polyphosphate kinase 2 (PPK2) is required for controlling intracellular levels of important regulatory molecules and for maintaining susceptibility to the first-line anti-TB drug isoniazid. In addition, PPK2 was found to be required for M. tuberculosis growth in the lungs of mice, at least in part by suppressing the expression of certain key cytokines and chemokines by inactivated lung macrophages.

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Protective Vaccine Efficacy of the Complete Form of PPE39 Protein from Mycobacterium tuberculosis Beijing/K Strain in Mice

Clinical and Vaccine Immunology ◽

10.1128/cvi.00219-17 ◽

2017 ◽

Vol 24 (11) ◽

Cited By ~ 4

Author(s):

Ahreum Kim ◽

Yun-Gyoung Hur ◽

Sunwha Gu ◽

Sang-Nae Cho

Keyword(s):

T Cells ◽

Mycobacterium Tuberculosis ◽

T Cell ◽

Vaccine Development ◽

Protective Efficacy ◽

Interleukin 2 ◽

T Cell Epitopes ◽

Content Type ◽

Complete Form ◽

Ifn Γ

ABSTRACT The aim of this study was to evaluate the protective efficacy of MTBK_24820, a complete form of PPE39 protein derived from a predominant Beijing/K strain of Mycobacterium tuberculosis in South Korea. Mice were immunized with MTKB_24820, M. bovis Bacilli Calmette-Guérin (BCG), or adjuvant prior to a high-dosed Beijing/K strain aerosol infection. After 4 and 9 weeks, bacterial loads were determined and histopathologic and immunologic features in the lungs and spleens of the M. tuberculosis-infected mice were analyzed. Putative immunogenic T-cell epitopes were examined using synthetic overlapping peptides. Successful immunization of MTBK_24820 in mice was confirmed by increased IgG responses (P < 0.05) and recalled gamma interferon (IFN-γ), interleukin-2 (IL-2), IL-6, and IL-17 responses (P < 0.05 or P < 0.01) to MTBK_24820. After challenge with the Beijing/K strain, an approximately 0.5 to 1.0 log10 reduction in CFU in lungs and fewer lung inflammation lesions were observed in MTBK_24820-immunized mice compared to those for control mice. Moreover, MTBK_24820 immunization elicited significantly higher numbers of CD4+ T cells producing protective cytokines, such as IFN-γ and IL-17, in lungs and spleens (P < 0.01) and CD4+ multifunctional T cells producing IFN-γ, tumor necrosis factor alpha (TNF-α), and/or IL-17 (P < 0.01) than in control mice, suggesting protection comparable to that of BCG against the hypervirulent Beijing/K strain. The dominant immunogenic T-cell epitopes that induced IFN-γ production were at the N terminus (amino acids 85 to 102 and 217 to 234). Its vaccine potential, along with protective immune responses in vivo, may be informative for vaccine development, particularly in regions where the M. tuberculosis Beijing/K-strain is frequently isolated from TB patients.

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Transcriptional Profiling of Mycobacterium tuberculosis Exposed toIn VitroLysosomal Stress

Infection and Immunity ◽

10.1128/iai.00072-16 ◽

2016 ◽

Vol 84 (9) ◽

pp. 2505-2523 ◽

Cited By ~ 22

Author(s):

Wenwei Lin ◽

Paola Florez de Sessions ◽

Garrett Hor Keong Teoh ◽

Ahmad Naim Nazri Mohamed ◽

Yuan O. Zhu ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Efflux Pump ◽

Metabolic Reprogramming ◽

Human Macrophage ◽

Host Immune System ◽

Activated Macrophages ◽

Intrinsic Resistance ◽

Macrophage Infection ◽

Content Type

Increasing experimental evidence supports the idea thatMycobacterium tuberculosishas evolved strategies to survive within lysosomes of activated macrophages. To further our knowledge ofM. tuberculosisresponse to the hostile lysosomal environment, we profiled the global transcriptional activity ofM. tuberculosiswhen exposed to the lysosomal soluble fraction (SF) prepared from activated macrophages. Transcriptome sequencing (RNA-seq) analysis was performed using various incubation conditions, ranging from noninhibitory to cidal based on the mycobacterial replication or killing profile. Under inhibitory conditions that led to the absence of apparent mycobacterial replication,M. tuberculosisexpressed a unique transcriptome with modulation of genes involved in general stress response, metabolic reprogramming, respiration, oxidative stress, dormancy response, and virulence. The transcription pattern also indicates characteristic cell wall remodeling with the possible outcomes of increased infectivity, intrinsic resistance to antibiotics, and subversion of the host immune system. Among the lysosome-specific responses, we identified theglgE-mediated 1,4 α-glucan synthesis pathway and a defined group of VapBC toxin/anti-toxin systems, both of which represent toxicity mechanisms that potentially can be exploited for killing intracellular mycobacteria. A meta-analysis including previously reported transcriptomic studies in macrophage infection andin vitrostress models was conducted to identify overlapping and nonoverlapping pathways. Finally, the Tap efflux pump-encoding geneRv1258cwas selected for validation. AnM. tuberculosis ΔRv1258cmutant was constructed and displayed increased susceptibility to killing by lysosomal SF and the antimicrobial peptide LL-37, as well as attenuated survival in primary murine macrophages and human macrophage cell line THP-1.

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Listeria-Vectored Vaccine Expressing the Mycobacterium tuberculosis 30-Kilodalton Major Secretory Protein via the Constitutively Active prfA* Regulon Boosts Mycobacterium bovis BCG Efficacy against Tuberculosis

Infection and Immunity ◽

10.1128/iai.00245-17 ◽

2017 ◽

Vol 85 (9) ◽

Cited By ~ 7

Author(s):

Qingmei Jia ◽

Barbara Jane Dillon ◽

Saša Masleša-Galić ◽

Marcus A. Horwitz

Keyword(s):

T Cells ◽

Mycobacterium Tuberculosis ◽

Mycobacterium Bovis ◽

Interleukin 2 ◽

Secretory Protein ◽

Broth Culture ◽

Listeriolysin O ◽

Content Type ◽

Ifn Γ ◽

Constitutively Active

ABSTRACT A potent vaccine against tuberculosis, one of the world's deadliest diseases, is needed to enhance the immunity of people worldwide, most of whom have been vaccinated with the partially effective Mycobacterium bovis BCG vaccine. Here we investigate novel live attenuated recombinant Listeria monocytogenes (rLm) vaccines expressing the Mycobacterium tuberculosis 30-kDa major secretory protein (r30/antigen 85B [Ag85B]) (rLm30) as heterologous booster vaccines in animals primed with BCG. Using three attenuated L. monocytogenes vectors, L. monocytogenes ΔactA (LmI), L. monocytogenes ΔactA ΔinlB (LmII), and L. monocytogenes ΔactA ΔinlB prfA* (LmIII), we constructed five rLm30 vaccine candidates expressing r30 linked in frame to the L. monocytogenes listeriolysin O signal sequence and driven by the hly promoter (h30) or linked in frame to the ActA N-terminal 100 amino acids and driven by the actA promoter (a30). All five rLm30 vaccines secreted r30 in broth and macrophages; while rLm30 expressing r30 via a constitutively active prfA* regulon (rLmIII/a30) expressed the largest amount of r30 in broth culture, all five rLm30 vaccines expressed equivalent amounts of r30 in infected macrophages. In comparative studies, boosting of BCG-immunized mice with rLmIII/a30 induced the strongest antigen-specific T-cell responses, including splenic and lung polyfunctional CD4+ T cells expressing the three cytokines interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin-2 (IL-2) (P < 0.001) and splenic and lung CD8+ T cells expressing IFN-γ (P < 0.0001). In mice and guinea pigs, the rLmIII/a30 and rLmI/h30 vaccines were generally more potent booster vaccines than r30 with an adjuvant and a recombinant adenovirus vaccine expressing r30. In a setting in which BCG alone was highly immunoprotective, boosting of mice with rLmIII/a30, the most potent of the vaccines, significantly enhanced protection against aerosolized M. tuberculosis (P < 0.01).

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Biphasic Dynamics of Macrophage Immunometabolism during Mycobacterium tuberculosis Infection

mBio ◽

10.1128/mbio.02550-18 ◽

2019 ◽

Vol 10 (2) ◽

Cited By ~ 27

Author(s):

Lanbo Shi ◽

Qingkui Jiang ◽

Yuri Bushkin ◽

Selvakumar Subbian ◽

Sanjay Tyagi

Keyword(s):

Mycobacterium Tuberculosis ◽

Immune Cells ◽

Aerobic Glycolysis ◽

Defense Responses ◽

Bioactive Lipids ◽

Macrophage Infection ◽

Mycobacterium Tuberculosis Infection ◽

Metabolic Switch ◽

Content Type ◽

M1 Polarization

ABSTRACT Macrophages are the primary targets of Mycobacterium tuberculosis infection; the early events of macrophage interaction with M. tuberculosis define subsequent progression and outcome of infection. M. tuberculosis can alter the innate immunity of macrophages, resulting in suboptimal Th1 immunity, which contributes to the survival, persistence, and eventual dissemination of the pathogen. Recent advances in immunometabolism illuminate the intimate link between the metabolic states of immune cells and their specific functions. In this review, we describe the little-studied biphasic metabolic dynamics of the macrophage response during progression of infection by M. tuberculosis and discuss their relevance to macrophage immunity and M. tuberculosis pathogenicity. The early phase of macrophage infection, which is marked by M1 polarization, is accompanied by a metabolic switch from mitochondrial oxidative phosphorylation to hypoxia-inducible factor 1 alpha (HIF-1α)-mediated aerobic glycolysis (also known as the Warburg effect in cancer cells), as well as by an upregulation of pathways involving oxidative and antioxidative defense responses, arginine metabolism, and synthesis of bioactive lipids. These early metabolic changes are followed by a late adaptation/resolution phase in which macrophages transition from glycolysis to mitochondrial oxidative metabolism, with a consequent dampening of macrophage proinflammatory and antimicrobial responses. Importantly, the identification of upregulated metabolic pathways and/or metabolic regulatory mechanisms with immunomodulatory functions during M1 polarization has revealed novel mechanisms of M. tuberculosis pathogenicity. These advances can lead to the development of novel host-directed therapies to facilitate bacterial clearance in tuberculosis by targeting the metabolic state of immune cells.

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Cryptococcal Phospholipase B1 Is Required for Intracellular Proliferation and Control of Titan Cell Morphology during Macrophage Infection

Infection and Immunity ◽

10.1128/iai.03104-14 ◽

2015 ◽

Vol 83 (4) ◽

pp. 1296-1304 ◽

Cited By ~ 32

Author(s):

Robert J. Evans ◽

Zhongming Li ◽

William S. Hughes ◽

Julianne T. Djordjevic ◽

Kirsten Nielsen ◽

...

Keyword(s):

Cryptococcus Neoformans ◽

Virulence Factors ◽

Fold Increase ◽

Macrophage Infection ◽

Content Type ◽

The Central Nervous System ◽

Opportunistic Fungal Pathogen ◽

And Control

Cryptococcus neoformansis an opportunistic fungal pathogen and a leading cause of fungal-infection-related fatalities, especially in immunocompromised hosts. Several virulence factors are known to play a major role in the pathogenesis of cryptococcal infections, including the enzyme phospholipase B1 (Plb1). Compared to other well-studiedCryptococcus neoformansvirulence factors such as the polysaccharide capsule and melanin production, very little is known about the contribution of Plb1 to cryptococcal virulence. Phospholipase B1 is a phospholipid-modifying enzyme that has been implicated in multiple stages of cryptococcal pathogenesis, including initiation and persistence of pulmonary infection and dissemination to the central nervous system, but the underlying reason for these phenotypes remains unknown. Here we demonstrate that a Δplb1knockout strain ofC. neoformanshas a profound defect in intracellular growth within host macrophages. This defect is due to a combination of a 50% decrease in proliferation and a 2-fold increase in cryptococcal killing within the phagosome. In addition, we show for the first time that the Δplb1strain undergoes a morphological change duringin vitroandin vivointracellular infection, resulting in a subpopulation of very large titan cells, which may arise as a result of the attenuated mutant's inability to cope within the macrophage.

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Stringent Response Factors PPX1 and PPK2 Play an Important Role in Mycobacterium tuberculosis Metabolism, Biofilm Formation, and Sensitivity to IsoniazidIn Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01139-16 ◽

2016 ◽

Vol 60 (11) ◽

pp. 6460-6470 ◽

Cited By ~ 19

Author(s):

Yu-Min Chuang ◽

Noton K. Dutta ◽

Chien-Fu Hung ◽

T.-C. Wu ◽

Harvey Rubin ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Biofilm Formation ◽

Tricarboxylic Acid Cycle ◽

Antibiotic Sensitivity ◽

Stringent Response ◽

Antibiotic Tolerance ◽

Inorganic Polyphosphate ◽

Response Factors ◽

Content Type

ABSTRACTMycobacterium tuberculosisremains a global health threat largely due to the lengthy duration of curative antibiotic treatment, contributing to medical nonadherence and the emergence of drug resistance. This prolonged therapy is likely due to the presence ofM. tuberculosispersisters, which exhibit antibiotic tolerance. Inorganic polyphosphate [poly(P)] is a key regulatory molecule in theM. tuberculosisstringent response mediating antibiotic tolerance. The polyphosphate kinase PPK1 is responsible for poly(P) synthesis inM. tuberculosis, while the exopolyphosphatases PPX1 and PPX2 and the GTP synthase PPK2 are responsible for poly(P) hydrolysis. In the present study, we show by liquid chromatography-tandem mass spectrometry that poly(P)-accumulatingM. tuberculosismutant strains deficient inppx1orppk2had significantly lower intracellular levels of glycerol-3-phosphate (G3P) and 1-deoxy-xylulose-5-phosphate. Real-time PCR revealed decreased expression of genes in the G3P synthesis pathway in each mutant. Theppx1-deficient mutant also showed a significant accumulation of metabolites in the tricarboxylic acid cycle, as well as altered arginine and NADH metabolism. Each poly(P)-accumulating strain showed defective biofilm formation, while deficiency ofppk2was associated with increased sensitivity to plumbagin and meropenem and deficiency ofppx1led to enhanced susceptibility to clofazimine. A DNA vaccine expressingppx1andppk2, together with two other members of theM. tuberculosisstringent response,M. tuberculosisrelandsigE, did not show protective activity against aerosol challenge withM. tuberculosis, but vaccine-induced immunity enhanced the killing activity of isoniazid in a murine model of chronic tuberculosis. In summary, poly(P)-regulating factors of theM. tuberculosisstringent response play an important role inM. tuberculosismetabolism, biofilm formation, and antibiotic sensitivityin vivo.

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Hydrolysis of Clavulanate by Mycobacterium tuberculosis β-Lactamase BlaC Harboring a Canonical SDN Motif

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00598-15 ◽

2015 ◽

Vol 59 (9) ◽

pp. 5714-5720 ◽

Cited By ~ 12

Author(s):

Daria Soroka ◽

Inès Li de la Sierra-Gallay ◽

Vincent Dubée ◽

Sébastien Triboulet ◽

Herman van Tilbeurgh ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Fold Increase ◽

Mycobacterium Abscessus ◽

Site Directed Mutagenesis ◽

Directed Mutagenesis ◽

Content Type ◽

Emergence Of Resistance ◽

Hydrolysis Of ◽

Sequential Formation

ABSTRACTCombinations of β-lactams with clavulanate are currently being investigated for tuberculosis treatment. SinceMycobacterium tuberculosisproduces a broad spectrum β-lactamase, BlaC, the success of this approach could be compromised by the emergence of clavulanate-resistant variants, as observed for inhibitor-resistant TEM variants in enterobacteria. Previous analyses based on site-directed mutagenesis of BlaC have led to the conclusion that this risk was limited. Here, we used a different approach based on determination of the crystal structure of β-lactamase BlaMAbofMycobacterium abscessus, which efficiently hydrolyzes clavulanate. Comparison of BlaMAband BlaC allowed for structure-assisted site-directed mutagenesis of BlaC and identification of the G132N substitution that was sufficient to switch the interaction of BlaC with clavulanate from irreversible inactivation to efficient hydrolysis. The substitution, which restored the canonical SDN motif (SDG→SDN), allowed for efficient hydrolysis of clavulanate, with a more than 104-fold increase inkcat(0.41 s−1), without affecting the hydrolysis of other β-lactams. Mass spectrometry revealed that acylation of BlaC and of its G132N variant by clavulanate follows similar paths, involving sequential formation of two acylenzymes. Decarboxylation of the first acylenzyme results in a stable secondary acylenzyme in BlaC, whereas hydrolysis occurs in the G132N variant. The SDN/SDG polymorphism defines two mycobacterial lineages comprising rapidly and slowly growing species, respectively. Together, these results suggest that the efficacy of β-lactam–clavulanate combinations may be limited by the emergence of resistance. β-Lactams active without clavulanate, such as faropenem, should be prioritized for the development of new therapies.

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Mycobacterium tuberculosis Hip1 Dampens Macrophage Proinflammatory Responses by Limiting Toll-Like Receptor 2 Activation

Infection and Immunity ◽

10.1128/iai.05574-11 ◽

2011 ◽

Vol 79 (12) ◽

pp. 4828-4838 ◽

Cited By ~ 22

Author(s):

Ranjna Madan-Lala ◽

Katia Vitorello Peixoto ◽

Fabio Re ◽

Jyothi Rengarajan

Keyword(s):

Mycobacterium Tuberculosis ◽

Disease Progression ◽

Proinflammatory Cytokines ◽

Inflammatory Responses ◽

Toll Like Receptor ◽

Serine Hydrolase ◽

Content Type ◽

Cytokines And Chemokines ◽

Proinflammatory Responses ◽

Toll Like Receptor 2

ABSTRACTMycobacterium tuberculosisis a highly successful human pathogen that evades host innate immunity by interfering with macrophage functions. In addition to avoiding macrophage microbicidal activities,M. tuberculosistriggers secretion of proinflammatory cytokines and chemokines in macrophages. The levels of proinflammatory cytokines induced by clinicalM. tuberculosisisolates are thought to play an important role in determining tuberculosis disease progression and severity, but the mechanisms by whichM. tuberculosismodulates the magnitude of inflammatory responses remain unclear. Here we show thatM. tuberculosisrestricts robust macrophage activation and dampens proinflammatory responses through the cell envelope-associated serine hydrolase Hip1 (hydrolaseimportant forpathogenesis1). By transcriptionally profiling macrophages infected with either wild-type orhip1mutant bacteria, we found that thehip1mutant induced earlier and significantly higher levels of several proinflammatory cytokines and chemokines. We show that increased activation of Toll-like receptor 2 (TLR2)- and MyD88-dependent signaling pathways mediates the enhanced cytokine secretion induced by thehip1mutant. Thus, Hip1 restricts the onset and magnitude of proinflammatory cytokines by limiting TLR2-dependent activation. We also show that Hip1 dampens TLR2-independent activation of the inflammasome and limits secretion of interleukin-18 (IL-18). Dampening of TLR2 signaling does not require viableM. tuberculosisor phagocytosis but does require Hip1 catalytic activity. We propose thatM. tuberculosisrestricts proinflammatory responses by masking cell surface interactions between TLR2 agonists onM. tuberculosisand TLR2 on macrophages. This strategy may allowM. tuberculosisto evade early detection by host immunity, delay the onset of adaptive immune responses, and accelerate disease progression.

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Discrimination between Active and Latent Tuberculosis Based on Ratio of Antigen-Specific to Mitogen-Induced IP-10 Production

Journal of Clinical Microbiology ◽

10.1128/jcm.02758-14 ◽

2014 ◽

Vol 53 (2) ◽

pp. 504-510 ◽

Cited By ~ 30

Author(s):

Yun Hee Jeong ◽

Yun-Gyoung Hur ◽

Hyejon Lee ◽

Sunghyun Kim ◽

Jang-Eun Cho ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Interleukin 2 ◽

Induced Responses ◽

Necrosis Factor Alpha ◽

Content Type ◽

Monocyte Chemoattractant Protein 1 ◽

Tnf Α ◽

Release Assay ◽

Ltbi Group ◽

Ifn Γ

Mycobacterium tuberculosisis the major causative agent of tuberculosis (TB). The gamma interferon (IFN-γ) release assay (IGRA) has been widely used to diagnose TB by testing cell-mediated immune responses but has no capacity for distinguishing between active TB and latent TB infection (LTBI). This study aims to identify a parameter that will help to discriminate active TB and LTBI. Whole-blood samples from 33 active TB patients, 20 individuals with LTBI, and 26 non-TB controls were applied to the commercial IFN-γ release assay, QuantiFERON-TB Gold In-Tube, and plasma samples were analyzed for interleukin-2 (IL-2), IL-6, IL-8, IL-10, IL-13, tumor necrosis factor-alpha (TNF-α), IFN-γ, monokine induced by IFN-γ (MIG), interferon gamma inducible protein 10 (IP-10), interferon-inducible T cell alpha chemoattractant (I-TAC), and monocyte chemoattractant protein 1 (MCP-1) by using a commercial cytometric bead array. TheMycobacterium tuberculosisantigen-specific production of most of the assayed cytokines and chemokines was higher in the active TB than in the LTBI group. The mitogen-induced responses were lower in the active TB than in the LTBI group. When the ratio of TB-specific to mitogen-induced responses was calculated, IL-2, IL-6, IL-10, IL-13, TNF-α, IFN-γ, MIG, and IP-10 were more useful in discriminating active TB from LTBI. In particular, most patients showed higher IP-10 production toMycobacterium tuberculosisantigens than to mitogen at the individual level, and the ratio for IP-10 was the strongest indicator of active infection versus LTBI with 93.9% sensitivity and 90% specificity. In conclusion, the ratio of the TB-specific to the mitogen-induced IP-10 responses showed the most promising accuracy for discriminating active TB versus LTBI and should be further studied to determine whether it can serve as a biomarker that might help clinicians administer appropriate treatments.

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Differentiation of Antigen-Specific T Cells with Limited Functional Capacity during Mycobacterium tuberculosis Infection

Infection and Immunity ◽

10.1128/iai.00480-13 ◽

2013 ◽

Vol 82 (1) ◽

pp. 132-139 ◽

Cited By ~ 16

Author(s):

Yun Hee Jeong ◽

Bo-Young Jeon ◽

Sun-Hwa Gu ◽

Sang-Nae Cho ◽

Sung Jae Shin ◽

...

Keyword(s):

T Cells ◽

Mycobacterium Tuberculosis ◽

T Cell ◽

Memory T Cells ◽

Interleukin 2 ◽

Effector Memory ◽

Memory Cells ◽

Content Type ◽

Tnf Α ◽

Ifn Γ

ABSTRACTDespite the generation ofMycobacterium tuberculosis-specific T cell immune responses during the course of infection, only 5 to 10% of exposed individuals develop active disease, while others develop a latent infection. This phenomenon suggests defectiveM. tuberculosis-specific immunity, which necessitates more careful characterization ofM. tuberculosis-specific T cell responses. Here, we longitudinally analyzed the phenotypes and functions ofM. tuberculosis-specific T cells. In contrast to the functional exhaustion of T cells observed after chronic infection,M. tuberculosis-specific CD8+T cells differentiated into either effector (CD127loCD62Llo) or effector memory (CD127hiCD62Llo) cells, but not central memory cells (CD127hiCD62Lhi), with low programmed death 1 (PD-1) expression, even in the presence of high levels of bacteria. Additionally,M. tuberculosis-specific CD8+and CD4+T cells produced substantial levels of tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ), but not interleukin 2 (IL-2), uponin vitrorestimulation. AmongM. tuberculosis-specific CD8+T cells, CD127hieffector memory cells displayed slower ongoing turnover but greater survival potential. In addition, these cells produced more IFN-γ and TNF-α and displayed lytic activity upon antigen stimulation. However, the effector function ofM. tuberculosis-specific CD8+CD127hieffector memory T cells was inferior to that of canonical CD8+CD127himemory T cells generated after acute lymphocytic choriomeningitis virus infection. Collectively, our data demonstrate thatM. tuberculosis-specific T cells can differentiate into memory T cells during the course ofM. tuberculosisinfection independent of the bacterial burden but with limited functionality. These results provide a framework for further understanding the mechanisms ofM. tuberculosisinfection that can be used to develop more effective vaccines.

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