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1.
Vitamin C: A Natural Inhibitor of Cell Wall Functions and Stress Response in Mycobacteria.
Syal, K, Chatterji, D
Advances in experimental medicine and biology. 2018;:321-332
Abstract
Tuberculosis, caused by Mycobacterium tuberculosis, has re-emerged as a threat to human race. Conventional antibiotic treatments are failing due to different stress response strategies adopted by bacterial pathogens. Since time immemorial, Vitamin C is known to protect against pathogens by boosting immunity in humans. Recently, Vitamin C has been shown to directly kill M. tuberculosis including multiple drug-resistant strains by generation of oxidative radicals through Fenton's reaction. Concurrently, it inhibits (p)ppGpp-mediated stringent response thus effectively shutting down long-term survival and persistence in mycobacteria. Here, we have discussed historical perspective and recent evidences on Vitamin C-mediated inhibition of several key pathways of M. tuberculosis such as (p)ppGpp synthesis and mycobacterial cell wall function. Several cell wall components including mycolic acids are critical for mycobacterial virulence. We observed downregulation of various mycolic acids in M. smegmatis upon treatment with Vitamin C, and data have been presented here. Vitamin C has been shown to inhibit the biofilm growth as well as disrupt the formed biofilm in mycobacteria. Additionally, Vitamin C role in cell-mediated and humoral immunity has been elucidated. Vitamin C is toxic at high concentration; therefore we have proposed the idea of derivatizing Vitamin C in order to lower the minimal inhibition concentration (MIC) necessary to target M. tuberculosis.
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2.
Macrophage-microbe interaction: lessons learned from the pathogen Mycobacterium tuberculosis.
BoseDasgupta, S, Pieters, J
Seminars in immunopathology. 2018;(6):577-591
Abstract
Macrophages, being the cornerstone of the immune system, have adapted the ancient nutrient acquisition mechanism of phagocytosis to engulf various infectious organisms thereby helping to orchestrate an appropriate host response. Phagocytosis refers to the process of internalization and degradation of particulate material, damaged and senescent cells and microorganisms by specialized cells, after which the vesicle containing the ingested particle, the phagosome, matures into acidic phagolysosomes upon fusion with hydrolytic enzyme-containing lysosomes. The destructive power of the macrophage is further exacerbated through the induction of macrophage activation upon a variety of inflammatory stimuli. Despite being the end-point for many phagocytosed microbes, the macrophage can also serve as an intracellular survival niche for a number of intracellular microorganisms. One microbe that is particularly successful at surviving within macrophages is the pathogen Mycobacterium tuberculosis, which can efficiently manipulate the macrophage at several levels, including modulation of the phagocytic pathway as well as interfering with a number of immune activation pathways that normally would lead to eradication of the internalized bacilli. M. tuberculosis excels at circumventing destruction within macrophages, thus establishing itself successfully for prolonged times within the macrophage. In this contribution, we describe a number of general features of macrophages in the context of their function to clear an infection, and highlight the strategies employed by M. tuberculosis to counter macrophage attack. Interestingly, research on the evasion tactics employed by M. tuberculosis within macrophages not only helps to design strategies to curb tuberculosis, but also allows a better understanding of host cell biology.
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3.
RNase 7 but not psoriasin nor sPLA2-IIA associates with Mycobacterium tuberculosis during airway epithelial cell infection.
Torres-Juarez, F, Touqui, L, Leon-Contreras, J, Rivas-Santiago, C, Enciso-Moreno, JA, Hernández-Pando, R, Rivas-Santiago, B
Pathogens and disease. 2018;(2)
Abstract
Tuberculosis is a disease caused by Mycobacterium tuberculosis (Mtb). Innate immunity is the first line of defense against Mtb and malfunctions in any of its components are associated with the susceptibility to the disease. Epithelial products such as host defense peptides (HDPs) are the first molecules produced to counteract the infection. Although a wide variety of HDPs are produced by epithelial cells only a few of them have been studied during Mtb infection. Here, we assessed the expression and production of the HDPs psoriasin, secreted phospholipases A2 (sPLA2-IIA) and Ribonuclease (RNase) 7 in airway epithelial cells (NCI-H292), type II pneumocytes (A549 cells) and monocyte-derived macrophages from human peripheral blood mononuclear cells and from the human cell line THP1 after Mtb in vitro infection. Results show that psoriasin and sPLA2-IIA were not induced by Mtb in any of the evaluated cells, while RNase 7 was overexpressed in infected airway epithelial cells. Intracellular analysis by flow cytometry demonstrated that the highest levels of RNase 7 were observed 6 h post-infection and the induction was dependent on direct interaction between airway epithelial cells and Mtb. In addition, analysis by electron microscopy showed that RNase 7 was capable of attaching to the cell wall of intracellular mycobacteria. Our studies suggest that the induction of RNase 7 in response to Mtb could have a role in anti-mycobacterial immunity, which needs to be studied as an innate immune mechanism.
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4.
Potential Effect of Statins on Mycobacterium tuberculosis Infection.
Guerra-De-Blas, PDC, Torres-González, P, Bobadilla-Del-Valle, M, Sada-Ovalle, I, Ponce-De-León-Garduño, A, Sifuentes-Osornio, J
Journal of immunology research. 2018;:7617023
Abstract
Tuberculosis is one of the 10 leading causes of death in the world. The current treatment is based on a combination of antimicrobials administered for six months. It is essential to find therapeutic agents with which the treatment time can be shortened and strengthen the host immune response against Mycobacterium tuberculosis. M. tuberculosis needs cholesterol to infect and survive inside the host, but the progression of the infection depends to a large extent on the capacity of the immune response to contain the infection. Statins inhibit the synthesis of cholesterol and have pleiotropic effects on the immune system, which have been associated with better results in the treatment of several infectious diseases. Recently, it has been reported that cells treated with statins are more resistant to M. tuberculosis infection, and they have even been proposed as adjuvants in the treatment of M. tuberculosis infection. The aim of this review is to summarize the immunopathogenesis of tuberculosis and its mechanisms of evasion and to compile the available scientific information on the effect of statins in the treatment of tuberculosis.
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5.
Mycobacterium tuberculosis PE1 and PE2 proteins carrying conserved α/β-serine hydrolase domain are esterases hydrolyzing short to medium chain p-nitrophenyl esters.
Divya M, B, Vemula, M, Balakrishnan, K, Banerjee, S, Guruprasad, L
Progress in biophysics and molecular biology. 2018;:90-102
Abstract
The distinctive PE and PPE families of proteins in Mycobacterium tuberculosis (M.tb), the tuberculosis (TB) causing bacteria, have been associated primarily with antigenicity, immune-modulation and virulence. Earlier, using structure-based sequence annotation, we identified a 225 amino acid conserved PE-PPE domain (Pfam: PF08237) commonly present in some PE and PPE proteins which was observed to comprise α/β-serine hydrolase fold. The prediction was supported by experimental validations of PE16 that was shown to exhibit esterase activity. In this study, we undertook the characterization of the probable operonic ORFs Rv0151c (pe1) and Rv0152c (pe2). Here we demonstrated that pe1 and pe2 are operonic in organization and are co-transcribed. Both PE1 and PE2 proteins possess esterase activity and hydrolyze short to medium chain p-nitrophenyl esters with more specific activity for p-nitrophenyl caproate (C6) with the optimal catalytic conditions of 37-38 °C and pH 7.0-8.0. The thermal denaturation temperature of PE1 and PE2 proteins were found to be 50 °C. The esterase activity of full length PE1, PE2 and their PE-PPE (α/β-serine hydrolase) domains are similar indicating that the function of PE-PPE domain is independent of the rest of the protein. The esterase activity of these proteins was validated by mutagenesis of the active site Ser; using PE1 Ser246Ala and PE2 Ser163Ala mutants. With these experiments, we conclusively show that the co-transcribed pe1 and pe2 genes code for enzymes belonging to the esterase family of proteins.
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6.
Commercial products to preserve specimens for tuberculosis diagnosis: a systematic review.
Reeve, BWP, McFall, SM, Song, R, Warren, R, Steingart, KR, Theron, G
The international journal of tuberculosis and lung disease : the official journal of the International Union against Tuberculosis and Lung Disease. 2018;(7):741-753
Abstract
SETTING Eliminating tuberculosis in high-burden settings requires improved diagnostic capacity. Important tests such as Xpert® MTB/RIF and culture are often performed at centralised laboratories that are geographically distant from the point of specimen collection. Preserving specimen integrity during transportation, which could affect test performance, is challenging. OBJECTIVE To conduct a systematic review of commercial products for specimen preservation for a World Health Organization technical consultation. DESIGN Databases were searched up to January 2018. Methodological quality was assessed using Quality Assessment of Technical Studies, a new technical study quality-appraisal tool, and Quality Assessment of Diagnostic Accuracy Studies-2. Studies were analysed descriptively in terms of the different products, study designs and diagnostic strategies used. RESULTS Four products were identified from 16 studies: PrimeStore-Molecular-Transport-Medium (PS-MTM), FTA card, GENO•CARD (all for nucleic acid amplification tests [NAATs]) and OMNIgene•SPUTUM (OMS; culture, NAATs). PS-MTM, but not FTA card or GENO•CARD, rendered Mycobacterium tuberculosis non-culturable. OMS reduced Löwenstein-Jensen but not MGIT™ 960™ contamination, led to delayed MGIT time-to-positivity, resulted in Xpert performance similar to cold chain-transported untreated specimens, and obviated the need for N-acetyl-L-cysteine-sodium hydroxide decontamination. Data from paucibacillary specimens were limited. Evidence that a cold chain improves culture was mixed and absent for Xpert. The effect of the product alone could be discerned in only four studies. CONCLUSION Limited evidence suggests that transport products result in test performance comparable to that seen in cold chain-transported specimens.
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7.
The Synergistic Effects of the Glutathione Precursor, NAC and First-Line Antibiotics in the Granulomatous Response Against Mycobacterium tuberculosis.
Teskey, G, Cao, R, Islamoglu, H, Medina, A, Prasad, C, Prasad, R, Sathananthan, A, Fraix, M, Subbian, S, Zhong, L, et al
Frontiers in immunology. 2018;:2069
Abstract
Mycobacterium tuberculosis (M. tb), the causative bacterial agent responsible for tuberculosis (TB) continues to afflict millions of people worldwide. Although the human immune system plays a critical role in containing M. tb infection, elimination proves immensely more challenging. Consequently, there has been a worldwide effort to eradicate, and limit the spread of M. tb through the conventional use of first-line antibiotics. Unfortunately, with the emergence of drug resistant and multi-drug resistant strains of M. tb the archetypical antibiotics no longer provide the same ascendancy as they once did. Furthermore, when administered, these first-line antibiotics commonly present severe complications and side effects. The biological antioxidant glutathione (GSH) however, has been demonstrated to have a profound mycobactericidal effect with no reported adverse consequences. Therefore, we examined if N-Acetyl Cysteine (NAC), the molecular precursor to GSH, when supplemented in combination with suboptimal levels of standalone first-line antibiotics would be sufficient to completely clear M. tb infection within in vitro derived granulomas from healthy subjects and individuals with type 2 diabetes (T2DM). Our results revealed that by virtue of immune modulation, the addition of NAC to subprime levels of isoniazid (INH) and rifampicin (RIF) was indeed capable of inducing complete clearance of M. tb among healthy individuals.
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8.
Antimycobacterial activity of novel hydrazide-hydrazone derivatives with 2H-chromene and coumarin scaffold.
Angelova, VT, Valcheva, V, Vassilev, NG, Buyukliev, R, Momekov, G, Dimitrov, I, Saso, L, Djukic, M, Shivachev, B
Bioorganic & medicinal chemistry letters. 2017;(2):223-227
Abstract
This study reports the synthesis of new 2H-chromene or coumarin based acylhydrazones, which were evaluated for their in vitro antimycobacterial activity against reference strain Mycobacterium tuberculosis H37Rv and compared to the first-line antituberculosis drugs, isoniazid (INH) and ethambutol (EMB). The most active compounds 7m (MIC 0.13μM), 7o (MIC 0.15μM) and 7k (MIC 0.17μM) demonstrated antimycobacterial activity at submicromolar concentration level and remarkably minimal associated cytotoxicity in the human embryonic kidney cell line HEK-293T. Structure-activity relationship for this class of compounds has been established.
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9.
High prevalence of Mycobacterium tuberculosis bacteraemia among a cohort of HIV-infected patients with severe sepsis in Lusaka, Zambia.
Muchemwa, L, Shabir, L, Andrews, B, Bwalya, M
International journal of STD & AIDS. 2017;(6):584-593
Abstract
Tuberculosis is recognised as one of the leading causes of severe sepsis among HIV-infected patients. Most patients with Mycobacterium tuberculosis bacteraemia have advanced HIV disease with CD4 counts less than 100 cells/μl and its presentation is non-specific in most instances. This was a cross-sectional study which was done by analyzing data from 201 adult HIV-infected patients who met the inclusion criteria for severe sepsis. The prevalence of Mycobacterium tuberculosis bactraemia in the study population was 34.8%. Severe sepsis caused by other etiologies was observed in 33 (16.4%) of the participants. Concomitant infection of Mycobacterium tuberculosis bactraemia with other organisms is not uncommon in patients with severe sepsis. This cohort of HIV-infected patients had severe immunosuppression with a median CD4 count of 51 (20-136) cells/μl with moderate anaemia, mean haemoglobin 8.0 (3.0) g/dl, and were generally underweight with a mean mid upper arm circumference (MUAC) of 21.0 (3.4) cm. Mycobacterium tuberculosis bacteraemia is very common in HIV-infected patients with advanced HIV disease who present with severe sepsis. Mycobacterium tuberculosis bacteraemia co-infection with aerobic organisms is not uncommon. Factors that were independently associated with Mycobacterium tuberculosis bacteraemia in our study population were MUAC and sodium level.
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10.
Design, Synthesis, and Experimental Validation of Peptide Ligands Targeting Mycobacterium tuberculosis σ Factors.
Vishwanath, S, Banerjee, S, Jamithireddy, AK, Srinivasan, N, Gopal, B, Chatterjee, J
Biochemistry. 2017;(16):2209-2218
Abstract
Transcription in prokaryotes is a multistep process and is primarily regulated at the initiation stage. σ factors are involved in promoter recognition and thus govern prokaryotic gene expression. Mycobacterium tuberculosis (Mtb) σ factors have been previously suggested as important drug targets through large-scale genome analyses. Here we demonstrate the feasibility of specific targeting of Mtb σ factors using designed peptides. A peptide library was generated using three-dimensional structural features corresponding to the interface regions of σ factors and the RNA polymerase. In silico optimization of the peptides, employing structural as well as sequence features, aided specific targeting of σA and σB. We synthesized and characterized the best hit peptide from the peptide library along with other control peptides and studied the interaction of these peptides with σB using biolayer interferometry. The experimental data validate the design strategy. These studies suggest the feasibility of designing specific peptides via in silico methods that bind σB with nanomolar affinity. We note that this strategy can be broadly applied to modulate prokaryotic transcription by designed peptides, thereby providing a tool for studying bacterial adaptation as well as host-pathogen interactions in infectious bacteria.