Protein kinase G from pathogenic mycobacteria promotes survival within macrophages

EBP50 induces apoptosis in macrophages by upregulating nitric oxide production to eliminate intracellular Mycobacterium tuberculosis

Mycobacterium bovis BCG is known to have the capacity to inhibit the positioning of iNOS on BCG-containing phagosomes by interfering with EBP50, a scaffolding protein that controls the recruitment of inducible nitric oxide synthase (iNOS) at the vicinity of phagosomes in macrophages. However, knockdown of the expression of EBP50 still facilitates the intracellular survival of BCG, which suggested that EBP50 may have some other unknown antimycobacterial properties. In this study we show that overexpression of EBP50 by a recombinant lentivirus had no effect on the iNOS recruitment to M.tuberculosis-containing phagosomes, but significantly promoted the elimination of intracellular M.tuberculosis. We revealed in the present study that the enhancement of intracellular killing to M. tuberculosis upon EBP50 overexpression was due to the increased level of apoptosis in macrophages. We showed that EBP50 overexpression significantly increased the expression of iNOS and generation of nitric oxide (NO), and EBP50-induced apoptosis was NO-dependent and mediated by Bax and caspase-3. We found that M. tuberculosis decreases while Mycobacterium smegmatis increases the expression of EBP50 in RAW264.7 cells, which suggested that virulent mycobacteria are capable of modulating the antimycobacterial properties of macrophages by inhibiting the expression and interfering with the function of EBP50.

Major differential gene regulation in Coxiella burnetii between in vivo and in vitro cultivation models

Background

Coxiella burnetii is the causative agent of the zoonotic disease Q fever. As it is an intracellular pathogen, infection by C. burnetii requires adaptation to its eukaryotic host and intracellular environment. The recently developed cell-free medium also allows the bacteria to propagate without host cells, maintaining its infection potential. The adaptation to different hosts or extracellular environments has been assumed to involve genome-wide modulation of C. burnetii gene expression. However, little is currently known about these adaptation events which are critical for understanding the intracellular survival of C. burnetii.

Results

We studied C. burnetii genome–wide transcriptional patterns in vivo (mice spleen) and in cell and cell-free in vitro culture models to examine its metabolic pathways and virulence associated gene expression patterns that are required to colonize and persist in different environments. Within each model, the gene expression profiles of the Dutch C. burnetii outbreak strain (602) and NM reference strains were largely similar. In contrast, modulation of gene-expression was strongly influenced by the cultivation method, indicating adaptation of the bacterium to available components. Genome–wide expression profiles of C. burnetii from in vitro cell culture were more similar to those seen for in vivo conditions, while gene expression profiles of cell-free culture were more distant to in vivo. Under in vivo conditions, significant alterations of genes involved in metabolism and virulence were identified. We observed that C. burnetii under in vivo conditions predominantly uses glucose as a carbon source (mostly for biosynthetic processes) and fatty acids for energy generation. C. burnetii experienced nutrient limitation and anaerobiosis as major stressors, while phosphate limitation was identified as an important signal for intracellular growth inside eukaryotic host cells. Finally, the in vivo environment significantly induced expression of several virulence genes, including those implicated in LPS synthesis, colonization, host component modulation and DNA repair mechanisms.

Conclusion

Our study shows that C. burnetii, with its relative small genome, requires only a subset of core gene functions to survive under in vitro conditions, but requires the induction of full repertoire of genes for successful pathogenesis and thriving in harsh environments in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2143-7) contains supplementary material, which is available to authorized users.

Mycobacterial proteomics: analysis of expressed proteomes and post-translational modifications to identify candidate virulence factors

The Mycobacterium tuberculosis bacillus has a number of unique features that make it a particularly effective human pathogen. Although genomic analysis has added to our current understanding of the molecular basis by which M. tuberculosis damages its host, proteomics may be better suited to describe the dynamic interactions between mycobacterial and host systems that underpin this disease. The M. tuberculosis proteome has been investigated using proteomics for over a decade, with increasingly sophisticated mass spectrometry technology and sensitive methods for comparative proteomic profiling. Deeper coverage of the M. tuberculosis proteome has led to the identification of hundreds of putative virulence determinants, as well as an unsurpassed coverage of post-translational modifications. Proteomics is therefore uniquely poised to contribute to our understanding of this pathogen, which may ultimately lead to better management of the disease.

Mycobacterium tuberculosis virulence: insights and impact on vaccine development

The existing TB vaccine, the attenuated Mycobacterium bovis strain BCG, is effective in protecting infants from severe forms of the disease, while its efficacy in protecting adults from pulmonary TB is poor. In the last two decades, a renewed interest in TB resulted in the development of several candidate vaccines that are now entering clinical trials. However, most of these vaccines are based on a common rationale and aim to induce a strong T-cell response against Mycobacterium tuberculosis. Recent advancements in the understanding of M. tuberculosis virulence determinants and associated pathogenic strategies are opening a new and broader view of the complex interaction between this remarkable pathogen and the human host, providing insights at molecular level that could lead to a new rationale for the design of novel antitubercular vaccines. A vaccination strategy that simultaneously targets different steps in TB pathogenesis may result in improved protection and reduced TB transmission.

Identification of Novel Inhibitors of Mycobacterium tuberculosis PknG Using Pharmacophore Based Virtual Screening, Docking, Molecular Dynamics Simulation, and Their Biological Evaluation

PknG is a Ser/thr protein kinase that plays a crucial role in regulatory processes within the mycobacterial cell and signaling cascade of the infected host cell. The essentiality of PknG in mycobacterial virulence by blocking phagosome-lysosome fusion as well as its role in intrinsic antibiotic resistance makes it an attractive drug target. However, only very few compounds have been reported as Mycobacterium tuberculosis PknG (MtPknG) inhibitors so far. Therefore, in an effort to find potential inhibitors against MtPknG, we report here a sequential pharmacophore-based virtual screening workflow, 3-fold docking with different search algorithms, and molecular dynamic simulations for better insight into the predicted binding mode of identified hits. After detailed analysis of the results, six ligands were selected for in vitro analysis. Three of these molecules showed significant inhibitory activity against MtPknG. In addition, inhibitory studies of mycobacterial growth in infected THP-1 macrophages demonstrated considerable growth inhibition of M. bovis BCG induced through compound NRB04248 without any cytotoxic effect against host macrophages. Our results suggest that the compound NRB04248 can be explored for further design and optimization of MtPknG inhibitors.

Lipid metabolism and Type VII secretion systems dominate the genome scale virulence profile of Mycobacterium tuberculosis in human dendritic cells

Background

Mycobacterium tuberculosis continues to kill more people than any other bacterium. Although its archetypal host cell is the macrophage, it also enters, and survives within, dendritic cells (DCs). By modulating the behaviour of the DC, M. tuberculosis is able to manipulate the host’s immune response and establish an infection. To identify the M. tuberculosis genes required for survival within DCs we infected primary human DCs with an M. tuberculosis transposon library and identified mutations with a reduced ability to survive.

Results

Parallel sequencing of the transposon inserts of the surviving mutants identified a large number of genes as being required for optimal intracellular fitness in DCs. Loci whose mutation attenuated intracellular survival included those involved in synthesising cell wall lipids, not only the well-established virulence factors, pDIM and cord factor, but also sulfolipids and PGL, which have not previously been identified as having a direct virulence role in cells. Other attenuated loci included the secretion systems ESX-1, ESX-2 and ESX-4, alongside many PPE genes, implicating a role for ESX-5. In contrast the canonical ESAT-6 family of ESX substrates did not have intra-DC fitness costs suggesting an alternative ESX-1 associated virulence mechanism. With the aid of a gene-nutrient interaction model, metabolic processes such as cholesterol side chain catabolism, nitrate reductase and cysteine-methionine metabolism were also identified as important for survival in DCs.

Conclusion

We conclude that many of the virulence factors required for survival in DC are shared with macrophages, but that survival in DCs also requires several additional functions, such as cysteine-methionine metabolism, PGLs, sulfolipids, ESX systems and PPE genes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1569-2) contains supplementary material, which is available to authorized users.

A redox regulatory system critical for mycobacterial survival in macrophages and biofilm development

Survival of M. tuberculosis in host macrophages requires the eukaryotic-type protein kinase G, PknG, but the underlying mechanism has remained unknown. Here, we show that PknG is an integral component of a novel redox homeostaticsystem, RHOCS, which includes the ribosomal protein L13 and RenU, a Nudix hydrolase encoded by a gene adjacent to pknG. Studies in M. smegmatis showed that PknG expression is uniquely induced by NADH, which plays a key role in metabolism and redox homeostasis. In vitro, RenU hydrolyses FAD, ADP-ribose and NADH, but not NAD+. Absence of RHOCS activities in vivo causes NADH and FAD accumulation, and increased susceptibility to oxidative stress. We show that PknG phosphorylates L13 and promotes its cytoplasmic association with RenU, and the phosphorylated L13 accelerates the RenU-catalyzed NADH hydrolysis. Importantly, interruption of RHOCS leads to impaired mycobacterial biofilms and reduced survival of M. tuberculosis in macrophages. Thus, RHOCS represents a checkpoint in the developmental program required for mycobacterial growth in these environments.

Nearly one-third of the world’s population is infected with Mycobacterium tuberculosis (Mtb), the causative agent of TB. A key factor that contributes to the widespread infection of Mtb is its capacity to survive inside the host macrophage. Understanding how Mtb withstands the hostile intracellular environment of this phagocytic cell may reveal targets for development of therapeutics that enhance the innate anti-Mtb activities of the macrophage. We discovered a novel signaling pathway in mycobacteria which regulates cellular redox homeostasis through NADH and FAD, regulators of metabolism and redox balance. NADH induces the expression of a protein kinase, PknG, which then phosphorylates the ribosomal protein L13 and promotes its presence in the cytoplasm. L13 therein forms a complex with RenU, a Nudix (Nucleoside diphosphate linked moiety X) hydrolase that degrades NADH and FAD. Genetic disruption of this signaling cascade leads to cellular accumulation of these molecules, increased mycobacterial sensitivity to oxidative stress, impaired surface biofilm growth, and most importantly, reduced survival of Mtb in macrophages.

Biochemical analysis of the NAD+-dependent malate dehydrogenase, a substrate of several serine/threonine protein kinases of Mycobacterium tuberculosis

PknD is one of the eleven eukaryotic-like serine/threonine protein kinases (STPKs) of Mycobacterium tuberculosis (Mtb). In vitro phosphorylation assays with the active recombinant PknD showed that the intracellular protein NAD⁺-dependent malate dehydrogenase (MDH) is a substrate of this kinase. MDH, an energy-supplying enzyme, catalyzes the interconversion of malate and oxaloacetate and plays crucial roles in several metabolic pathways including the citric acid cycle. The phosphorylation site was identified on threonine residues and the phosphorylation inhibited the MDH activity. In vitro, the recombinant MDH could also be phosphorylated by at least five other STPKs, PknA, PknE, PknH, PknJ, and PknG. Immunoprecipitation analysis revealed that MDH was hyperphosphorylated in the bacteria at the beginning of the stationary and under oxygen-limited conditions by STPKs other than PknD. On the contrary, when PknD-deficient mutant mycobacteria were grown in a phosphate-depleted medium, MDH was not detectably phosphorylated. These results suggest that although the MDH is a substrate of several mycobacterial STPKs, the activity of these kinases can depend on the environment, as we identified PknD as a key element in the MDH phosphorylation assay under phosphate-poor conditions.

Expression and purification of the natively disordered and redox sensitive metal binding regions of Mycobacterium tuberculosis protein kinase G

Mycobacterium tuberculosis protein kinase G (PknG) is secreted into host macrophages to block lysosomal degradation. The catalytic domain (∼147-405) is C-terminally flanked by a tetratricopeptide repeat domain (TPRD). The preceding rubredoxin-like metal-binding motif (RD, ∼74-147) mediates PknG redox regulation. The N-terminal ∼75 residues were predicted to show no regulatory secondary structure (NORS) and harbor the only site (T63) phosphorylated in vivo. Deletions or mutations in the NORS or the redox-sensitive RD significantly decrease the survival function. Here, we show that the RD appears only to be present in the folded, metal-bound state if ZnCl2 is added upon induction of protein expression in minimal medium. Since factor Xa cleaves at the end of its recognition site (IEGR), a modified expression plasmid for PknG1-147 was obtained by mutating the N-terminal thrombin to a factor Xa recognition site. This allows preparing PknG1-147 with its native N-terminus. We further present a fast approach to generate expression plasmids for only the NORS or the RD by site-directed mutagenesis of the expression plasmid for His-tagged PknG1-147. An expression plasmid for PknG1-75 was obtained by introducing a stop codon at position 76 and one for PknG74-174 by introducing a factor Xa recognition site before position 74. SDS-PAGE analysis shows that all fragments are highly expressed in E. coli and can be purified to high purity. Thereby, the established preparation protocols pave the route for the NMR structural characterization of PknG regulation by its N-terminal regions, which is demonstrated by the recorded initial (1)H-(15)N-HSQC spectra.

Label-free Quantitative Proteomics Reveals a Role for the Mycobacterium tuberculosis SecA2 Pathway in Exporting Solute Binding Proteins and Mce Transporters to the Cell Wall

Mycobacterium tuberculosis is an example of a bacterial pathogen with a specialized SecA2-dependent protein export system that contributes to its virulence. Our understanding of the mechanistic basis of SecA2-dependent export and the role(s) of the SecA2 pathway in M. tuberculosis pathogenesis has been hindered by our limited knowledge of the proteins exported by the pathway. Here, we set out to identify M. tuberculosis proteins that use the SecA2 pathway for their export from the bacterial cytoplasm to the cell wall. Using label-free quantitative proteomics involving spectral counting, we compared the cell wall and cytoplasmic proteomes of wild type M. tuberculosis to that of a ΔsecA2 mutant. This work revealed a role for the M. tuberculosis SecA2 pathway in the cell wall localization of solute binding proteins that work with ABC transporters to import solutes. Another discovery was a profound effect of SecA2 on the cell wall localization of the Mce1 and Mce4 lipid transporters, which contribute to M. tuberculosis virulence. In addition to the effects on solute binding proteins and Mce transporter export, our label-free quantitative analysis revealed an unexpected relationship between SecA2 and the hypoxia-induced DosR regulon, which is associated with M. tuberculosis latency. Nearly half of the transcriptionally controlled DosR regulon of cytoplasmic proteins were detected at higher levels in the ΔsecA2 mutant versus wild type M. tuberculosis. By increasing the list of M. tuberculosis proteins known to be affected by the SecA2 pathway, this study expands our appreciation of the types of proteins exported by this pathway and guides our understanding of the mechanism of SecA2-dependent protein export in mycobacteria. At the same time, the newly identified SecA2-dependent proteins are helpful for understanding the significance of this pathway to M. tuberculosis virulence and physiology.

Phosphorylation of Mycobacterium tuberculosis ParB participates in regulating the ParABS chromosome segregation system

Here, we present for the first time that Mycobacterium tuberculosis ParB is phosphorylated by several mycobacterial Ser/Thr protein kinases in vitro. ParB and ParA are the key components of bacterial chromosome segregation apparatus. ParB is a cytosolic conserved protein that binds specifically to centromere-like DNA parS sequences and interacts with ParA, a weak ATPase required for its proper localization. Mass spectrometry identified the presence of ten phosphate groups, thus indicating that ParB is phosphorylated on eight threonines, Thr32, Thr41, Thr53, Thr110, Thr195, and Thr254, Thr300, Thr303 as well as on two serines, Ser5 and Ser239. The phosphorylation sites were further substituted either by alanine to prevent phosphorylation or aspartate to mimic constitutive phosphorylation. Electrophoretic mobility shift assays revealed a drastic inhibition of DNA-binding by ParB phosphomimetic mutant compared to wild type. In addition, bacterial two-hybrid experiments showed a loss of ParA-ParB interaction with the phosphomimetic mutant, indicating that phosphorylation is regulating the recruitment of the partitioning complex. Moreover, fluorescence microscopy experiments performed in the surrogate Mycobacterium smegmatis ΔparB strain revealed that in contrast to wild type Mtb ParB, which formed subpolar foci similar to M. smegmatis ParB, phoshomimetic Mtb ParB was delocalized. Thus, our findings highlight a novel regulatory role of the different isoforms of ParB representing a molecular switch in localization and functioning of partitioning protein in Mycobacterium tuberculosis.

The intracellular Scots pine shoot symbiont Methylobacterium extorquens DSM13060 aggregates around the host nucleus and encodes eukaryote-like proteins

Endophytes are microbes that inhabit plant tissues without any apparent signs of infection, often fundamentally altering plant phenotypes. While endophytes are typically studied in plant roots, where they colonize the apoplast or dead cells, Methylobacterium extorquens strain DSM13060 is a facultatively intracellular symbiont of the meristematic cells of Scots pine (Pinus sylvestris L.) shoot tips. The bacterium promotes host growth and development without the production of known plant growth-stimulating factors. Our objective was to examine intracellular colonization by M. extorquens DSM13060 of Scots pine and sequence its genome to identify novel molecular mechanisms potentially involved in intracellular colonization and plant growth promotion. Reporter construct analysis of known growth promotion genes demonstrated that these were only weakly active inside the plant or not expressed at all. We found that bacterial cells accumulate near the nucleus in intact, living pine cells, pointing to host nuclear processes as the target of the symbiont’s activity. Genome analysis identified a set of eukaryote-like functions that are common as effectors in intracellular bacterial pathogens, supporting the notion of intracellular bacterial activity. These include ankyrin repeats, transcription factors, and host-defense silencing functions and may be secreted by a recently imported type IV secretion system. Potential factors involved in host growth include three copies of phospholipase A2, an enzyme that is rare in bacteria but implicated in a range of plant cellular processes, and proteins putatively involved in gibberellin biosynthesis. Our results describe a novel endophytic niche and create a foundation for postgenomic studies of a symbiosis with potential applications in forestry and agriculture.

All multicellular eukaryotes host communities of essential microbes, but most of these interactions are still poorly understood. In plants, bacterial endophytes are found inside all tissues. M. extorquens DSM13060 occupies an unusual niche inside cells of the dividing shoot tissues of a pine and stimulates seedling growth without producing cytokinin, auxin, or other plant hormones commonly synthesized by plant-associated bacteria. Here, we tracked the bacteria using a fluorescent tag and confocal laser scanning microscopy and found that they localize near the nucleus of the plant cell. This prompted us to sequence the genome and identify proteins that may affect host growth by targeting processes in the host cytoplasm and nucleus. We found many novel genes whose products may modulate plant processes from within the plant cell. Our results open up new avenues to better understand how bacteria assist in plant growth, with broad implications for plant science, forestry, and agriculture.

Mycobacterium tuberculosis Mce3E suppresses host innate immune responses by targeting ERK1/2 signaling

Crucial to the pathogenesis of the tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis is its ability to subvert host immune defenses to promote its intracellular survival. The mammalian cell entry protein 3E (Mce3E), located in the region of difference 15 of the M. tuberculosis genome and absent in Mycobacterium bovis bacillus Calmette-Guérin, has an essential role in facilitating the internalization of mammalian cells by mycobacteria. However, relatively little is known about the role of Mce3E in modulation of host innate immune responses. In this study, we demonstrate that Mce3E inhibits the activation of the ERK1/2 signaling pathway, leading to the suppression of Tnf and Il6 expression, and the promotion of mycobacterial survival within macrophages. Mce3E interacts and colocalizes with ERK1/2 at the endoplasmic reticulum in a DEF motif (an ERK-docking motif)-dependent manner, relocates ERK1/2 from cytoplasm to the endoplasmic reticulum, and finally reduces the association of ERK1/2 with MEK1 and blocks the nuclear translocation of phospho-ERK1/2. A DEF motif mutant form of Mce3E (F294A) loses its ability to suppress Tnf and Il6 expression and to promote intracellular survival of mycobacteria. Inhibition of the ERK1/2 pathway in macrophages using U0126, a specific inhibitor of the ERK pathway, also leads to the suppressed Tnf and Il6 expression and the enhanced intracellular survival of mycobacteria. Taken together, these results suggest that M. tuberculosis Mce3E exploits the ERK1/2 signaling pathway to suppress host innate immune responses, providing a potential Mce3E-ERK1/2 interface-based drug target against M. tuberculosis.

What Role Does Mycobacterium avium subsp. paratuberculosis Play in Crohn's Disease?

Crohn's disease (CD) is a chronic, debilitating inflammatory bowel disease with no etiological agent yet identified. Studies have demonstrated that the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) is present in a high percentage of CD patients. Although MAP has been isolated from human specimens, current techniques fail to show the presence of MAP in 100 % of tissues or biopsies obtained from CD patient lesions, and thus MAP cannot meet Koch's postulate as the etiological agent of CD. In this report, the effect of genetic and immune factors as well as the presence of MAP as a potential environmental factor is analyzed.

Lead selection and characterization of antitubercular compounds using the Nested Chemical Library

Discovering new drugs to treat tuberculosis more efficiently and to overcome multidrug resistance is a world health priority. To find novel antitubercular agents several approaches have been used in various institutions worldwide, including target-based approaches against several validated mycobacterial enzymes and phenotypic screens. We screened more than 17,000 compounds from Vichem's Nested Chemical Library™ using an integrated strategy involving whole cell-based assays with Corynebacterium glutamicum and Mycobacterium tuberculosis, and target-based assays with protein kinases PknA, PknB and PknG as well as other targets such as PimA and bacterial topoisomerases simultaneously. With the help of the target-based approach we have found very potent hits inhibiting the selected target enzymes, but good minimal inhibitory concentrations (MIC) against M. tuberculosis were not achieved. Focussing on the whole cell-based approach several potent hits were found which displayed minimal inhibitory concentrations (MIC) against M. tuberculosis below 10 μM and were non-mutagenic, non-cytotoxic and the targets of some of the hits were also identified. The most active hits represented various scaffolds. Medicinal chemistry-based lead optimization was performed applying various strategies and, as a consequence, a series of novel potent compounds were synthesized. These efforts resulted in some effective potential antitubercular lead compounds which were confirmed in phenotypic assays.

ATP exhibits antimicrobial action by inhibiting bacterial utilization of ferric ions

ATP up-regulates macrophage antimycobacterial activity in a P2X7-dependent manner, but little is known about whether ATP directly exhibits antimicrobial effects against intracellular mycobacteria. In this study, we found that ATP inhibited the growth of various bacteria, including Staphylococcus, Pseudomonas, and mycobacteria, without damaging bacterial surface structures. Using gene technology, we newly established an enterobactin-deficient (entB(-)) mutant from ATP-resistant Klebsiella pneumoniae, and found the recovery of ATP susceptibility in the enterobactin-deleted mutant. Therefore, ATP's antibacterial activity is attributable to its iron-chelating ability. Since ATP distributed in the cytosol of macrophages at high concentrations, ATP appears to augment macrophage's antimicrobial activity by directly attacking intracytosolic and intra-autophagosomal pathogens. Furthermore, ATP exhibited combined effects with some antimicrobials against methicillin-resistant S. aureus (MRSA) and M. intracellulare, suggesting its usefulness as an adjunctive drug in the chemotherapy of certain intractable infections.

Expression and characterization of Streptomyces coelicolor serine/threonine protein kinase PkaE

We identified and characterized a new eukaryotic-type protein kinase (PkaE) from Streptomyces coelicolor A3 (2) M145. PkaE, consisting of 510 amino acid residues, is a cytoplasmic protein kinase and contains the catalytic domain of eukaryotic protein kinases in the N-terminal region. Recombinant PkaE was found to be autophosphorylated at threonine residues only. The disruption of chromosomal pkaE resulted in the overproduction of the actinorhodin-related blue pigment antibiotics. pkaE was expressed during the late growth phase in S. coelicolor A3 (2) M145, which corresponded to the production time of blue pigments. This result indicated that PkaE acts as a negative regulator for production of the secondary metabolites. In addition, PkaE was able to phosphorylate KbpA, a regulator involved in the AfsK-AfsR regulatory pathway.

Mycobacterium tuberculosis proteome microarray for global studies of protein function and immunogenicity

Poor understanding of the basic biology of Mycobacterium tuberculosis (MTB), the etiological agent of tuberculosis, hampers development of much-needed drugs, vaccines, and diagnostic tests. Better experimental tools are needed to expedite investigations of this pathogen at the systems level. Here, we present a functional MTB proteome microarray covering most of the proteome and an ORFome library. We demonstrate the broad applicability of the microarray by investigating global protein-protein interactions, small-molecule-protein binding, and serum biomarker discovery, identifying 59 PknG-interacting proteins, 30 bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) binding proteins, and 14 MTB proteins that together differentiate between tuberculosis (TB) patients with active disease and recovered individuals. Results suggest that the MTB rhamnose pathway is likely regulated by both the serine/threonine kinase PknG and c-di-GMP. This resource has the potential to generate a greater understanding of key biological processes in the pathogenesis of tuberculosis, possibly leading to more effective therapies for the treatment of this ancient disease.

An inducible and secreted eukaryote-like serine/threonine kinase of Salmonella enterica serovar Typhi promotes intracellular survival and pathogenesis

Eukaryote-like serine/threonine kinases (eSTKs) constitute an important family of bacterial virulence factors. Genome analysis had predicted putative eSTKs in Salmonella enterica serovar Typhi, although their functional characterization and the elucidation of their role in pathogenesis are still awaited. We show here that the primary sequence and secondary structure of the t4519 locus of Salmonella Typhi Ty2 have all the signatures of eukaryotic superfamily kinases. t4519 encodes a ∼39-kDa protein (T4519), which shows serine/threonine kinase activities in vitro. Recombinant T4519 (rT4519) is autophosphorylated and phosphorylates the universal substrate myelin basic protein. Infection of macrophages results in decreased viability of the mutant (Ty2Δt4519) strain, which is reversed by gene complementation. Moreover, reactive oxygen species produced by the macrophages signal to the bacteria to induce T4519, which is translocated to the host cell cytoplasm. That T4519 may target a host substrate(s) is further supported by the activation of host cellular signaling pathways and the induction of cytokines/chemokines. Finally, the role of T4519 in the pathogenesis of Salmonella Typhi is underscored by the significantly decreased mortality of mice infected with the Ty2Δt4519 strain and the fact that the competitive index of this strain for causing systemic infection is 0.25% that of the wild-type strain. This study characterizes the first eSTK of Salmonella Typhi and demonstrates its role in promoting phagosomal survival of the bacteria within macrophages, which is a key determinant of pathogenesis. This, to the best of our knowledge, is the first study to describe the essential role of eSTKs in the in vivo pathogenesis of Salmonella spp.

Targeting bacterial central metabolism for drug development

Current antibiotics, derived mainly from natural sources, inhibit a narrow spectrum of cellular processes, namely DNA replication, protein synthesis, and cell wall biosynthesis. With the worldwide explosion of drug resistance, there is renewed interest in the investigation of alternate essential cellular processes, including bacterial central metabolic pathways, as a drug target space for the next generation of antibiotics. However, the validation of targets in central metabolism is more complex, as essentiality of such targets can be conditional and/or contextual. Bearing in mind our enhanced understanding of prokaryotic central metabolism, a key question arises: can central metabolism be bacteria's Achilles' heel and a therapeutic target for the development of new classes of antibiotics? In this review, we draw lessons from oncology and attempt to address some of the open questions related to feasibility of targeting bacterial central metabolism as a strategy for developing new antibacterial drugs.

Striking the Right Balance Determines TB or Not TB

Mycobacterium tuberculosis continues to be one of the most successful pathogens on earth. Upon inhalation of M. tuberculosis by a healthy individual, the host immune system will attempt to eliminate these pathogens using a combination of immune defense strategies. These include the recruitment of macrophages and other phagocytes to the site of infection, production of cytokines that enhance the microbicidal capacity of the macrophages, as well as the activation of distinct subsets of leukocytes that work in concert to fight the infection. However, being as successful as it is, M. tuberculosis has evolved numerous strategies to subvert host immunity at virtual every level. As a consequence, one third of the world inhabitants carry M. tuberculosis, and tuberculosis continuous to cause disease in more than 8 million people with deadly consequences in well over 1 million patients each year. In this review, we discuss several of the strategies that M. tuberculosis employs to circumvent host immunity, as well as describe some of the mechanisms that the host uses to counter such subversive strategies. As for many other infectious diseases, the ultimate outcome is usually defined by the relative strength of the virulence strategies employed by the tubercle bacillus versus the arsenal of immune defense mechanisms of the infected host.

Crosstalk between Mycobacterium tuberculosis and the host cell

The successful establishment and maintenance of a bacterial infection depend on the pathogen's ability to subvert the host cell's defense response and successfully survive, proliferate, or persist within the infected cell. To circumvent host defense systems, bacterial pathogens produce a variety of virulence factors that potentiate bacterial adherence and invasion and usurp host cell signaling cascades that regulate intracellular microbial survival and trafficking. Mycobacterium tuberculosis, probably one of the most successful pathogens on earth, has coexisted with humanity for centuries, and this intimate and persistent connection between these two organisms suggests that the pathogen has evolved extensive mechanisms to evade the human immune system at multiple levels. While some of these mechanisms are mediated by factors released by M. tuberculosis, others rely on host components that are hijacked to prevent the generation of an effective immune response thus benefiting the survival of M. tuberculosis within the host cell. Here, we describe several of these mechanisms, with an emphasis on the cyclic nucleotide signaling and subversion of host responses that occur at the intracellular level when tubercle bacilli encounter macrophages, a cell that becomes a safe-house for M. tuberculosis although it is specialized to kill most microbes.

A rational framework for evaluating the next generation of vaccines against Mycobacterium avium subspecies paratuberculosis

Since the early 1980s, several investigations have focused on developing a vaccine against Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne's disease in cattle and sheep. These studies used whole-cell inactivated vaccines that have proven useful in limiting disease progression, but have not prevented infection. In contrast, modified live vaccines that invoke a Th1 type immune response, may improve protection against infection. Spurred by recent advances in the ability to create defined knockouts in MAP, several independent laboratories have developed modified live vaccine candidates by transpositional mutation of virulence and metabolic genes in MAP. In order to accelerate the process of identification and comparative evaluation of the most promising modified live MAP vaccine candidates, members of a multi-institutional USDA-funded research consortium, the Johne's disease integrated program (JDIP), met to establish a standardized testing platform using agreed upon protocols. A total of 22 candidates vaccine strains developed in five independent laboratories in the United States and New Zealand voluntarily entered into a double blind stage gated trial pipeline. In Phase I, the survival characteristics of each candidate were determined in bovine macrophages. Attenuated strains moved to Phase II, where tissue colonization of C57/BL6 mice were evaluated in a challenge model. In Phase III, five promising candidates from Phase I and II were evaluated for their ability to reduce fecal shedding, tissue colonization and pathology in a baby goat challenge model. Formation of a multi-institutional consortium for vaccine strain evaluation has revealed insights for the implementation of vaccine trials for Johne's disease and other animal pathogens. We conclude by suggesting the best way forward based on this 3-phase trial experience and challenge the rationale for use of a macrophage-to-mouse-to native host pipeline for MAP vaccine development.

Manipulation of the mononuclear phagocyte system by Mycobacterium tuberculosis

Over the past 20 years, there has been an emerging appreciation about the role of the mononuclear phagocyte system (MPS) to control and eradicate pathogens. Likewise, there have been significant advances in dissecting the mechanisms involved in the microbial subversion of MPS cells, mainly affecting their differentiation and effector functions. Mycobacterium tuberculosis is a chronic bacterial pathogen that represents an enigma to the field because of its remarkable ability to thrive in humans. One reason is that M. tuberculosis renders a defective MPS compartment, which is perhaps the most ingenious strategy for survival in the host given the prominence of these cells to modulate microenvironments, their function as sentinels and orchestrators of the immune response, and their pathogenic role as reservoirs for microbial persistence. In this article, the principal strategies used by M. tuberculosis to subvert the MPS compartment are presented along with emerging concepts.

Proteome and phosphoproteome analysis of the serine/threonine protein kinase E mutant of Mycobacterium tuberculosis

AIMS

Serine/threonine protein kinases (STPKs) have prominent roles in the survival mechanisms of Mycobacterium tuberculosis (M. tuberculosis). Previous studies from our laboratory underscored the role of PknE, an STPK in virulence, adaptation and the suppression of host cell apoptosis. In this study, two-dimensional gel electrophoresis was used to study the proteome and phosphoproteome profiles of wild type M. tuberculosis and its isogenic pknE deletion mutant (ΔpknE) during growth in Middlebrook 7H9 and nitric oxide stress.

MAIN METHODS

Wild-type M. tuberculosis and its isogenic pknE deletion mutant strain were grown in Middlebrook 7H9 as well as subjected to nitric oxide stress using sodium nitroprusside. Whole cell lysates were prepared and analyzed by 2D-gel electrophoresis. Phosphoproteomes were analyzed using phospho serine and phospho threonine antibodies after subjecting the 2D-gels to western blotting. Proteins of interest were identified using mass spectrometry.

KEY FINDINGS

Our analysis provides insights into the targets that impose pro-apoptotic as well as altered cellular phenotypes on ΔpknE, revealing novel substrates and functions for PknE.

SIGNIFICANCE

For the first time, our proteome and phosphoproteome data decipher the function of PknE in cell division, virulence, dormancy, suppression of sigma factor B and its regulated genes, suppression of two-component systems and in the metabolic activity of M. tuberculosis.

Homology modelling, docking, pharmacophore and site directed mutagenesis analysis to identify the critical amino acid residue of PknI from Mycobacterium tuberculosis

Tuberculosis is caused by Mycobacterium tuberculosis, an intracellular pathogen. PknI is one of the 11 functional Serine/Threonine Protein Kinases which is predicted to regulate the cell division of M. tuberculosis. In order to find newer drugs and vaccine we need to understand the pathogenesis of the disease. We have used the bioinformatics approach to identify the functionally active residues of PknI and to confirm the same with wet lab experiments. In the current study, we have created homology model for PknI and have done comparative structural analysis of PknI with other kinases. Molecular docking studies were done with a library of kinase inhibitors and T95 was found as the potent inhibitor for PknI. Based on structure based pharmacophore analysis of kinase substrate complexes, Lys 41 along with Asp90, Val92 and Asp96 were identified as functionally important residues. Further, we used site directed mutagenesis technique to mutate Lys 41 to Met resulting in defective cell division of Mycobacterium smegmatis mc(2). Overall, the proposed model together with its binding features gained from pharmacophore docking studies helped in identifying ligand inhibitor specific to PknI which was confirmed by laboratory experiments.

Deletion of relA abrogates the capacity of Mycobacterium avium paratuberculosis to establish an infection in calves

Previous comparative studies in goats revealed deletion of relA but not pknG abrogates the capacity of Mycobacterium avium subsp. paratuberculosis (Map) to establish a persistent infection. The immune response elicited by the mutant cleared infection. The objective of the present study was to extend the studies in calves and compare the proliferative response elicited by the relA deletion mutant (ΔrelA) and Map using flow cytometry and quantitative reverse transcription real-time PCR (qRT-PCR). Six 3-day-old calves were divided into two groups. Three were vaccinated with ΔrelA and 3 inoculated with wild type Map. The calves were challenged with Map 1 month later and necropsied 3 months post challenge. Three untreated calves were used as uninfected controls. Examination of tissues revealed the ΔrelA mutant was immune eliminated. Bacterial load of Map was significantly reduced in the calves vaccinated with ΔrelA and challenged with Map in comparison with calves inoculated and challenged with Map. A vigorous CD4 memory T cell response was detected at necropsy in PBMC from both infected groups. CD8 positive NK cells proliferated in the presence and absence of antigen stimulation in both treated groups but not in the uninfected group. IFN-γ, IL17, and IL22 gene expression were up-regulated with an associated increase in their transcription factors, Tbet and RORC, in both treated groups. TGF-β, IL-10, and FoxP3 were not up-regulated, indicating no activation of regulatory T cells. The findings show that the immune response to ΔrelA is clearly different than the response to Map. Understanding the immunological basis for this difference should facilitate development of a vaccine that elicits sterile immunity.

Safety and reactogenicity of BCG revaccination with isoniazid pretreatment in TST positive adults

RATIONALE

Global tuberculosis (TB) control may require mass vaccination with a new TB vaccine, such as a recombinant bacille Calmette Guerin (BCG) or attenuated Mycobacterium tuberculosis (MTB). The safety profile of live mycobacterial vaccines in latently infected adults with prior infant BCG vaccination is unknown.

OBJECTIVES

Evaluate safety and reactogenicity of BCG revaccination, with or without isoniazid (INH) pretreatment, in adults with latent MTB infection (LTBI).

METHODS

Eighty-two healthy, HIV uninfected, South African adults, with a BCG scar and tuberculin skin test (TST) diameter ≥ 15 mm, were randomized to receive 6 months of INH, starting either before, or 6 months after, intradermal revaccination with BCG Vaccine SSI (Statens Serum Institut, Copenhagen). Safety and reactogenicity data are reported through 3 months post BCG revaccination.

RESULTS

Baseline characteristics were similar between treatment arms. Mean baseline TST diameter was 20 ± 4 mm. Seventy-two subjects received BCG revaccination. Injection site erythema (68%) and induration (86%) peaked 1 week after revaccination. Ulceration (76%) peaked at 2 weeks, and resolved by 3 months in all but 3 subjects. Diameter of ulceration was >10mm in only 8%, but a residual scar was common (85%). No regional lymphadenitis or serious morbidity related to BCG was seen. Reactogenicity was not affected by INH pretreatment.

CONCLUSION

BCG revaccination of MTB infected adults is safe, well tolerated, and reactogenicity is similar to that of primary BCG vaccination. Clinical trials of live recombinant BCG or attenuated MTB vaccines may be considered in latently infected adults, with or without INH pretreatment (ClinicalTrials.gov identifier: NCT01119521).

Effect of isoniazid therapy for latent TB infection on QuantiFERON-TB gold in-tube responses in adults with positive tuberculin skin test results in a high TB incidence area: a controlled study

BACKGROUND

T-cell interferon-γ release assays (IGRAs) are used in the diagnosis of Mycobacterium tuberculosis infection and could be useful biomarkers of response to treatment of latent TB infection for clinical trials, infection control units, and TB programs.

METHODS

This investigation was a prospective, controlled substudy of IGRA responses in 82 healthy South African adults with HIV seronegative and positive tuberculin skin test results randomly assigned to treatment with 6 months of daily isoniazid preventive therapy (IPT) or observation before Bacillus Calmette-Guérin revaccination in a clinical trial. QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was used to measure interferon-γ (IFN-γ) response to mycobacterial antigens at baseline and after IPT or observation.

RESULTS

IFN-γ levels declined between baseline and the end of IPT (signed rank test P≤.0001) and between baseline and a similar period of observation without IPT (signed rank test P=.03). The rate of decrease in IFN-γ responses over time did not differ between the groups (Mann-Whitney-Wilcoxon test P=.31). QFT-GIT test results in two subjects (5%) in the IPT group and two subjects (5%) in the observation group reverted from positive to negative during follow-up. No significant difference was found between the groups with respect to baseline positivity or the proportion of patients whose tests reverted to negative.

CONCLUSIONS

IPT had no effect on changes in QFT-GIT readouts during short-term follow-up of adults with positive tuberculin skin tests in a high TB incidence setting. QFT-GIT is unlikely to be a useful biomarker of response to treatment of latent TB infection.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01119521; URL: www.clinicaltrials.gov.

Mycobacterium tuberculosis Rv3402c enhances mycobacterial survival within macrophages and modulates the host pro-inflammatory cytokines production via NF-kappa B/ERK/p38 signaling

Intracellular survival plays a central role in the pathogenesis of Mycobacterium tuberculosis, a process which depends on an array of virulence factors to colonize and replicate within the host. The M. tuberculosis iron regulated open reading frame (ORF) rv3402c, encoding a conserved hypothetical protein, was shown to be up-regulated upon infection in both human and mice macrophages. To explore the function of this ORF, we heterologously expressed the rv3402c gene in the non-pathogenic fast-growing Mycobacterium smegmatis strain, and demonstrated that Rv3402c, a cell envelope-associated protein, was able to enhance the intracellular survival of recombinant M. smegmatis. Enhanced growth was not found to be the result of an increased resistance to intracellular stresses, as growth of the Rv3402c expressing strain was unaffected by iron depletion, H₂O₂ exposure, or acidic conditions. Colonization of macrophages by M. smegmatis expressing Rv3402c was associated with substantial cell death and significantly greater amount of TNF-α and IL-1β compared with controls. Rv3402c-induced TNF-α and IL-1β production was found to be mediated by NF-κB, ERK and p38 pathway in macrophages. In summary, our study suggests that Rv3402c delivered in a live M. smegmatis vehicle can modify the cytokines profile of macrophage, promote host cell death and enhance the persistence of mycobacterium within host cells.

Protein kinase B (PknB) of Mycobacterium tuberculosis is essential for growth of the pathogen in vitro as well as for survival within the host

The Mycobacterium tuberculosis protein kinase B (PknB) comprises an intracellular kinase domain, connected through a transmembrane domain to an extracellular region that contains four PASTA domains. The present study describes the comprehensive analysis of different domains of PknB in the context of viability in avirulent and virulent mycobacteria. We find stringent regulation of PknB expression necessary for cell survival, with depletion or overexpression of PknB leading to cell death. Although PknB-mediated kinase activity is essential for cell survival, active kinase lacking the transmembrane or extracellular domain fails to complement conditional mutants not expressing PknB. By creating chimeric kinases, we find that the intracellular kinase domain has unique functions in the virulent strain, which cannot be substituted by other kinases. Interestingly, we find that although the presence of the C-terminal PASTA domain is dispensable in the avirulent M. smegmatis, all four PASTA domains are essential in M. tuberculosis. The differential behavior of PknB vis-à-vis the number of essential PASTA domains and the specificity of kinase domain functions suggest that PknB-mediated growth and signaling events differ in virulent compared with avirulent mycobacteria. Mouse infection studies performed to determine the role of PknB in mediating pathogen survival in the host demonstrate that PknB is not only critical for growth of the pathogen in vitro but is also essential for the survival of the pathogen in the host.

Surviving the macrophage: tools and tricks employed by Mycobacterium tuberculosis

Mycobacterium tuberculosis has evolved to withstand one of the most inhospitable cells within the human body, namely the macrophage, a cell that is normally geared toward the destruction of any invading microbe. How M. tuberculosis achieves this is still incompletely understood; however, a number of mechanisms are now known that provide advantages to M. tuberculosis for its survival and proliferation inside the macrophage. While some of these mechanisms are mediated by factors released by M. tuberculosis, others rely on host components that are being hijacked to benefit survival of M. tuberculosis within the macrophage as well to avoid the generation of an effective immune response. Here, we describe several of these mechanisms, also pointing out the potential usage of this knowledge toward the development of novel strategies to treat tuberculosis. Furthermore, we attempt to put the 'macrophage niche' into context with other intracellular pathogens and discuss some of the generalities as well as specializations that M. tuberculosis employs to survive.

Insights into redox sensing metalloproteins in Mycobacterium tuberculosis

Mycobacterium tuberculosis, the pathogen that causes tuberculosis, has evolved sophisticated mechanisms for evading assault by the human host. This review focuses on M. tuberculosis regulatory metalloproteins that are sensitive to exogenous stresses attributed to changes in the levels of gaseous molecules (i.e., molecular oxygen, carbon monoxide and nitric oxide) to elicit an intracellular response. In particular, we highlight recent developments on the subfamily of Whi proteins, redox sensing WhiB-like proteins that contain iron-sulfur clusters, sigma factors and their cognate anti-sigma factors of which some are zinc-regulated, and the dormancy survival regulon DosS/DosT-DosR heme sensory system. Mounting experimental evidence suggests that these systems contribute to a highly complex and interrelated regulatory network that controls M. tuberculosis biology. This review concludes with a discussion of strategies that M. tuberculosis has developed to maintain redox homeostasis, including mechanisms to regulate endogenous nitric oxide and carbon monoxide levels.

What pathogens have taught us about posttranslational modifications

Pathogens use various mechanisms to manipulate host processes to promote infection. Decades of research on pathogens have revealed not only the molecular mechanisms that these microbes use to replicate and survive within host cells, but also seminal information on how host signaling machinery regulates cellular processes. Among these discoveries are mechanisms involving posttranslational modifications that alter the activity, localization, or interactions of the modified protein. Herein, we examine how pathogens have contributed to our basic understanding of three posttranslational modifications: phosphorylation, NMPylation, and ubiquitylation. Over the years, technologies, techniques and research tools have developed side by side with the study of pathogens, facilitating the discovery of protein modifications and furthering our understanding of how they contribute to both infection and cellular functions.

Cell death paradigms in the pathogenesis of Mycobacterium tuberculosis infection

Cell death or senescence is a fundamental event that helps maintain cellular homeostasis, shapes the growth of organism, and provides protective immunity against invading pathogens. Decreased or increased cell death is detrimental both in infectious and non-infectious diseases. Cell death is executed both by regulated enzymic reactions and non-enzymic sudden collapse. In this brief review we have tried to summarize various cell death modalities and their impact on the pathogenesis of Mycobacterium tuberculosis.

Bacterial serine/threonine protein kinases in host-pathogen interactions

In bacterial pathogenesis, monitoring and adapting to the dynamically changing environment in the host and an ability to disrupt host immune responses are critical. The virulence determinants of pathogenic bacteria include the sensor/signaling proteins of the serine/threonine protein kinase (STPK) family that have a dual role of sensing the environment and subverting specific host defense processes. STPKs can sense a wide range of signals and coordinate multiple cellular processes to mount an appropriate response. Here, we review some of the well studied bacterial STPKs that are essential virulence factors and that modify global host responses during infection.

Syntheses and biological evaluation of 2-amino-3-acyl-tetrahydrobenzothiophene derivatives; antibacterial agents with antivirulence activity

Developing new compounds targeting virulence factors (e.g., inhibition of pilus assembly by pilicides) is a promising approach to combating bacterial infection. A high-throughput screening campaign of a library of 17 500 small molecules identified 2-amino-3-acyl-tetrahydrobenzothiophene derivatives (hits 2 and 3) as novel inhibitors of pili-dependent biofilm formation in a uropathogenic Escherichia coli strain UTI89. Based on compounds 2 and 3 as the starting point, we designed and synthesized a series of structurally related analogs and investigated their activity against biofilm formation of E. coli UTI89. Systematic structural modification of the initial hits provided valuable information on their SARs for further optimization. In addition, small structural changes to the parent molecules resulted in low micromolar inhibitors (20-23) of E. coli biofilm development without an effect on bacterial growth. The hit compound 3 and its analog 20 were confirmed to prevent pili formation in a hemagglutination (HA) titer assay and electron microscopy (EM) measurements. These findings suggest that 2-amino-3-acyl-tetrahydrobenzothiophenes may serve as a new class of compounds for further elaboration as antibacterial agents with antivirulence activity.

Establishment and validation of whole-cell based fluorescence assays to identify anti-mycobacterial compounds using the Acanthamoeba castellanii-Mycobacterium marinum host-pathogen system

Tuberculosis is considered to be one of the world’s deadliest disease with 2 million deaths each year. The need for new antitubercular drugs is further exacerbated by the emergence of drug-resistance strains. Despite multiple recent efforts, the majority of the hits discovered by traditional target-based screening showed low efficiency in vivo. Therefore, there is heightened demand for whole-cell based approaches directly using host-pathogen systems. The phenotypic host-pathogen assay described here is based on the monitoring of GFP-expressing Mycobacterium marinum during infection of the amoeba Acanthamoeba castellanii. The assay showed straight-forward medium-throughput scalability, robustness and ease of manipulation, demonstrating its qualities as an efficient compound screening system. Validation with a series of known antitubercular compounds highlighted the advantages of the assay in comparison to previously published macrophage-Mycobacterium tuberculosis-based screening systems. Combination with secondary growth assays based on either GFP-expressing D. discoideum or M. marinum allowed us to further fine-tune compound characterization by distinguishing and quantifying growth inhibition, cytotoxic properties and antibiotic activities of the compounds. The simple and relatively low cost system described here is most suitable to detect anti-infective compounds, whether they present antibiotic activities or not, in which case they might exert anti-virulence or host defense boosting activities, both of which are largely overlooked by classical screening approaches.

PknE, a serine/threonine protein kinase of Mycobacterium tuberculosis initiates survival crosstalk that also impacts HIV coinfection

Serine threonine protein kinases (STPK) play a major role in the pathogenesis of Mycobacterium tuberculosis. Here, we examined the role of STPK pknE, using a deletion mutant ΔpknE in the modulation of intracellular signaling events that favor M. tuberculosis survival. Phosphorylation kinetics of MAPK (p38MAPK, Erk½ and SAPK/JNK) was defective in ΔpknE compared to wild-type infected macrophages. This defective signaling dramatically delayed and reduced the phosphorylation kinetics of transcription factors ATF-2 and c-JUN in ΔpknE infected macrophages. MAPK inhibitors instead of reducing the phosphorylation in ΔpknE infected macrophages, revealed crosstalks with Erk½ signaling influenced by SAPK/JNK and p38 pathways independently. Modulations in intra cellular signaling altered the expression of coreceptors CCR5 and CXCR4 in ΔpknE infected macrophages. In conclusion, pknE plays a role in MAPK crosstalks that enables intracellular survival of M. tuberculosis. This survival strategy also impacts HIV/TB coinfection.