Mycobacterium tuberculosis Infection-Driven Foamy Macrophages and Their Implications in Tuberculosis Control as Targets for Host-Directed Therapy

PPARdelta: A key modulator in the pathogenesis of diabetes mellitus and Mycobacterium tuberculosis co-morbidity

The interplay between lipid metabolism and immune response in macrophages plays a pivotal role in various infectious diseases, notably tuberculosis (TB). Herein, we illuminate the modulatory effect of heat-killed Mycobacterium tuberculosis (HKMT) on macrophage lipid metabolism and its implications on the inflammatory cascade. Our findings demonstrate that HKMT potently activates the lipid scavenger receptor, CD36, instigating lipid accumulation. While CD36 inhibition mitigated lipid increase, it unexpectedly exacerbated the inflammatory response. Intriguingly, this paradoxical effect was linked to an upregulation of PPARδ. Functional analyses employing PPARδ modulation revealed its central role in regulating both lipid dynamics and inflammation, suggesting it as a potential therapeutic target. Moreover, primary monocytic cells from diabetic individuals, a demographic at amplified risk of TB, exhibited heightened PPARδ expression and inflammation, further underscoring its pathological relevance. Targeting PPARδ in these cells effectively dampened the inflammatory response, offering a promising therapeutic avenue against TB.

The Influence of Body Fat Dynamics on Pulmonary Immune Responses in Murine Tuberculosis: Unraveling Sex-Specific Insights

The World Health Organization (WHO) highlights a greater susceptibility of males to tuberculosis (TB), a vulnerability attributed to sex-specific variations in body fat and dietary factors. Our study delves into the unexplored terrain of how alterations in body fat influence Mycobacterium tuberculosis (Mtb) burden, lung pathology, immune responses, and gene expression, with a focus on sex-specific dynamics. Utilizing a low-dose Mtb-HN878 clinical strain infection model, we employ transgenic FAT-ATTAC mice with modulable body fat to explore the impact of fat loss (via fat ablation) and fat gain (via a medium-fat diet, MFD). Firstly, our investigation unveils that Mtb infection triggers severe pulmonary pathology in males, marked by shifts in metabolic signaling involving heightened lipid hydrolysis and proinflammatory signaling driven by IL-6 and localized pro-inflammatory CD8+ cells. This stands in stark contrast to females on a control regular diet (RD). Secondly, our findings indicate that both fat loss and fat gain in males lead to significantly elevated (1.6-fold (p ≤ 0.01) and 1.7-fold (p ≤ 0.001), respectively) Mtb burden in the lungs compared to females during Mtb infection (where fat loss and gain did not alter Mtb load in the lungs). This upsurge is associated with impaired lung lipid metabolism and intensified mitochondrial oxidative phosphorylation-regulated activity in lung CD8+ cells during Mtb infection. Additionally, our research brings to light that females exhibit a more robust systemic IFNγ (p ≤ 0.001) response than males during Mtb infection. This heightened response may either prevent active disease or contribute to latency in females during Mtb infection. In summary, our comprehensive analysis of the interplay between body fat changes and sex bias in Mtb infection reveals that alterations in body fat critically impact pulmonary pathology in males. Specifically, these changes significantly reduce the levels of pulmonary CD8+ T-cells and increase the Mtb burden in the lungs compared to females. The reduction in CD8+ cells in males is linked to an increase in mitochondrial oxidative phosphorylation and a decrease in TNFα, which are essential for CD8+ cell activation.

The impact of Mycobacterium tuberculosis on the macrophage cholesterol metabolism pathway

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen capable of adapting and surviving within macrophages, utilizing host nutrients for its growth and replication. Cholesterol is the main carbon source during the infection process of Mtb. Cholesterol metabolism in macrophages is tightly associated with cell functions such as phagocytosis of pathogens, antigen presentation, inflammatory responses, and tissue repair. Research has shown that Mtb infection increases the uptake of low-density lipoprotein (LDL) and cholesterol by macrophages, and enhances de novo cholesterol synthesis in macrophages. Excessive cholesterol is converted into cholesterol esters, while the degradation of cholesterol esters in macrophages is inhibited by Mtb. Furthermore, Mtb infection suppresses the expression of ATP-binding cassette (ABC) transporters in macrophages, impeding cholesterol efflux. These alterations result in the massive accumulation of cholesterol in macrophages, promoting the formation of lipid droplets and foam cells, which ultimately facilitates the persistent survival of Mtb and the progression of tuberculosis (TB), including granuloma formation, tissue cavitation, and systemic dissemination. Mtb infection may also promote the conversion of cholesterol into oxidized cholesterol within macrophages, with the oxidized cholesterol exhibiting anti-Mtb activity. Recent drug development has discovered that reducing cholesterol levels in macrophages can inhibit the invasion of Mtb into macrophages and increase the permeability of anti-tuberculosis drugs. The development of drugs targeting cholesterol metabolic pathways in macrophages, as well as the modification of existing drugs, holds promise for the development of more efficient anti-tuberculosis medications.

Mitochondrial electron transport chain in macrophage reprogramming: Potential role in antibacterial immune response

Macrophages restrain microbial infection and reinstate tissue homeostasis. The mitochondria govern macrophage metabolism and serve as pivot in innate immunity, thus acting as immunometabolic regulon. Metabolic pathways produce electron flows that end up in mitochondrial electron transport chain (mtETC), made of super-complexes regulating multitude of molecular and biochemical processes. Cell-intrinsic and extrinsic factors influence mtETC structure and function, impacting several aspects of macrophage immunity. These factors provide the macrophages with alternate fuel sources and metabolites, critical to gain functional competence and overcoming pathogenic stress. Mitochondrial reactive oxygen species (mtROS) and oxidative phosphorylation (OXPHOS) generated through the mtETC are important innate immune attributes, which help macrophages in mounting antibacterial responses. Recent studies have demonstrated the role of mtETC in governing mitochondrial dynamics and macrophage polarization (M1/M2). M1 macrophages are important for containing bacterial pathogens and M2 macrophages promote tissue repair and wound healing. Thus, mitochondrial bioenergetics and metabolism are intimately coupled with innate immunity. In this review, we have addressed mtETC function as innate rheostats that regulate macrophage reprogramming and innate immune responses. Advancement in this field encourages further exploration and provides potential novel macrophage-based therapeutic targets to control unsolicited inflammation.

Fluvastatin Converts Human Macrophages into Foam Cells with Increased Inflammatory Response to Inactivated Mycobacterium tuberculosis H37Ra

Cholesterol biosynthesis inhibitors (statins) protect hypercholesterolemic patients against developing active tuberculosis, suggesting that these drugs could help the host to control the pathogen at the initial stages of the disease. This work studies the effect of fluvastatin on the early response of healthy peripheral blood mononuclear cells (PBMCs) to inactivated Mycobacterium tuberculosis (Mtb) H37Ra. We found that in fluvastatin-treated PBMCs, most monocytes/macrophages became foamy cells that overproduced NLRP3 inflammasome components in the absence of immune stimulation, evidencing important cholesterol metabolism/immunity connections. When both fluvastatin-treated and untreated PBMCs were exposed to Mtb H37Ra, a small subset of macrophages captured large amounts of bacilli and died, concentrating the bacteria in necrotic areas. In fluvastatin-untreated cultures, most of the remaining macrophages became epithelioid cells that isolated these areas of cell death in granulomatous structures that barely produced IFNγ. By contrast, in fluvastatin-treated cultures, foamy macrophages surrounded the accumulated bacteria, degraded them, markedly activated caspase-1 and elicited a potent IFNγ/cytotoxic response. In rabbits immunized with the same bacteria, fluvastatin increased the tuberculin test response. We conclude that statins may enhance macrophage efficacy to control Mtb, with the help of adaptive immunity, offering a promising tool in the design of alternative therapies to fight tuberculosis.

Pathogenic mycobacterium upregulates cholesterol 25-hydroxylase to promote granuloma development via foam cell formation

Pathogenic mycobacteria orchestrate the complex cell populations known as granuloma that is the hallmark of tuberculosis. Foam cells, a lipid-rich cell-type, are considered critical for granuloma formation; however, the causative factor in foam cell formation remains unclear. Atherosclerosis is a chronic inflammatory disease characterized by the abundant accumulation of lipid-laden-macrophage-derived foam cells during which cholesterol 25-hydroxylase (CH25H) is crucial in foam cell formation. Here, we show that M. marinum (Mm), a relative of M. tuberculosis, induces foam cell formation, leading to granuloma development following CH25H upregulation. Moreover, the Mm-driven increase in CH25H expression is associated with the presence of phthiocerol dimycocerosate, a determinant for Mm virulence and integrity. CH25H-null mice showed decreased foam cell formation and attenuated pathology. Atorvastatin, a recommended first-line lipid-lowering drug, promoted the elimination of M. marinum and concomitantly reduced CH25H production. These results define a previously unknown role for CH25H in controlling macrophage-derived foam cell formation and Tuberculosis pathology.

Tropheryma whipplei infection in the lung of a patient with long COVID: a case report

BACKGROUND

Immune dysregulation in individuals with long COVID has been detected. Differential diagnosis of diffuse infiltration on chest CT in long COVID is challenging.

CASE PRESENTATION

A 62-year-old man presented with a 10-month history of dyspnea after COVID-19 infection. Dyspnea became worse in the one month preceding presentation. The chest CT showed multifocal, subpleural, bilateral opacities due to long-COVID, and infiltration around the bronchovascular bundle in the bilateral lower lung field. The pathology for the transbronchial cryobiopsy (TBCB) first reported chronic inflammation (mainly interstitial pneumonia). The patient had positive results on tests for the antibody, RO-52+, EJ+. The presumptive diagnosis of connective tissue disease-interstitial lung disease was made. Prednisone and cyclophosphamide were given. At follow-up one month later, the chest CT showed new diffuse ground-glass infiltration. The previous TBCB specimen was re-evaluated. Foamy macrophages were found in the alveolar air space. Periodic acid-Schiff (PAS) staining was performed. Numerous intracytoplasmic organisms were detected, with morphologic features consistent with those of Tropheryma whipplei. The patient recovered after intravenous ceftriaxone and oral trimethoprim-sulfamethoxazole. The final diagnosis was lung T. whipplei infection and long COVID-19.

CONCLUSION

This is the first case report of Tropheryma whipplei infection in the lung of a patient with long COVID-19. T. whipplei should be considered as a potential pathogen for diffuse lung infiltration in the post-COVID-19 era.

Host cell environments and antibiotic efficacy in tuberculosis

The aetiologic agent of tuberculosis (TB), Mycobacterium tuberculosis (Mtb), can survive, persist, and proliferate in a variety of heterogeneous subcellular compartments. Therefore, TB chemotherapy requires antibiotics crossing multiple biological membranes to reach distinct subcellular compartments and target these bacterial populations. These compartments are also dynamic, and our understanding of intracellular pharmacokinetics (PK) often represents a challenge for antitubercular drug development. In recent years, the development of high-resolution imaging approaches in the context of host-pathogen interactions has revealed the intracellular distribution of antibiotics at a new level, yielding discoveries with important clinical implications. In this review, we describe the current knowledge regarding cellular PK of antibiotics and the complexity of drug distribution within the context of TB. We also discuss the recent advances in quantitative imaging and highlight their applications for drug development in the context of how intracellular environments and microbial localisation affect TB treatment efficacy.

The Role of Rv1476 in Regulating Stress Response and Intracellular Survival of Mycobacterium tuberculosis

The virulence of Mycobacterium tuberculosis (M. tuberculosis) is related to many factors, including intracellular survival, cell wall permeability, and cell envelope proteins. However, the biological function of the M. tuberculosis membrane protein Rv1476 remains unclear. To investigate the potential role played by Rv1476, we constructed an Rv1476 overexpression strain and found that overexpression of Rv1476 enhanced the intracellular survival of M. tuberculosis, while having no impact on the growth rate in vitro. Stress experiments demonstrated that the Rv1476 overexpression strain displayed increased susceptibility to different stresses compared to the wild-type strain. Transcriptome analysis showed that Rv1476 overexpression causes changes in the transcriptome of THP-1 cells, and differential genes are mainly enriched in cell proliferation, fatty acid degradation, cytokine-cytokine receptor interaction, and immune response pathways. Rv1476 overexpression inhibited the expression of some anti-tuberculosis-related genes, such as CCL1, IL15, IL16, ISG15, GBP5, IL23, ATG2A, IFNβ, and CSF3. Altogether, we conclude that Rv1476 may play a critical role for M. tuberculosis in macrophage survival.

Tuberculosis and lung cancer: metabolic pathways play a key role

Despite the fact that some cases of tuberculosis (TB) are undiagnosed and untreated, it remains a serious global public health issue. In the diagnosis, treatment, and control of latent and active TB, there may be a lack of effectiveness. An understanding of metabolic pathways can be fundamental to treat latent TB infection and active TB disease. Rather than targeting Mycobacterium tuberculosis, the control strategies aim to strengthen host responses to infection and reduce chronic inflammation by effectively enhancing host resistance to infection. The pathogenesis and progression of TB are linked to several metabolites and metabolic pathways, and they are potential targets for host-directed therapies. Additionally, metabolic pathways can contribute to the progression of lung cancer in patients with latent or active TB. A comprehensive metabolic pathway analysis is conducted to highlight lung cancer development in latent and active TB. The current study aimed to emphasize the association between metabolic pathways of tumor development in patients with latent and active TB. Health control programs around the world are compromised by TB and lung cancer due to their special epidemiological and clinical characteristics. Therefore, presenting the importance of lung cancer progression through metabolic pathways occurring upon TB infection can open new doors to improving control of TB infection and active TB disease while stressing that further evaluations are required to uncover this correlation.

A Case of Whipple's Disease With Concomitant Esophageal Candidiasis

Whipple's Disease (WD) is a rare disease caused by the infection of Tropheryma whipplei. It can lead to immunosuppression and a multitude of effects on different organ systems, resulting in a constellation of seemingly unrelated findings. Although treatment may appear straightforward, T. whipplei can be difficult to eradicate. We present the case of a 36-year-old male with months of progressively worsening watery diarrhea, migratory arthralgias, and weight loss. He had undergone an extensive evaluation for rheumatologic, oncologic, and infectious disorders without positive findings. Esophagogastroduodenoscopy and colonoscopy revealed esophageal candidiasis, Helicobacter pylori infection, and foamy macrophages in the lamina propria of the duodenum and ileum with positive polymerase chain reaction for T. whipplei. There were no other risk factors for esophageal candidiasis. He received treatment for his esophageal candidiasis and H. pylori infection and was treated for WD with ceftriaxone for 2 weeks, followed by hydroxychloroquine and doxycycline for 1 year. Symptoms resolved after 3 months of therapy. One year later, repeat bidirectional endoscopy was performed. Biopsies were negative for T. whipplei, although there were persistent foamy macrophages. There have been previously reported cases of patients with WD with concomitant esophageal candidiasis, and this association implies a likely state of relative immunosuppression associated with WD, which is thought to be the result of impaired T helper cell 1 activity. This impairment likely contributes to the high rate of relapse. Having a low threshold for repeat evaluation is advisable for recurrent symptoms, but long-term surveillance strategies are not clearly defined.

Dual-specificity phosphatase 5-mediated fatty acid oxidation promotes Mycobacterium bovis BCG -induced inflammatory responses

Mycobacterium tuberculosis (Mtb) reprograms FAs metabolism of macrophages during infection and affects inflammatory reaction eventually, however, the mechanism remains poorly understood. Here we show that Mycobacterium bovis (BCG) induces DUSP5 expression through TLR2-MAPKs signaling pathway and promotes fatty acid oxidation (FAO). Silencing DUSP5 by adeno-associated virus vector (AAV) ameliorates lung injury and DUSP5 knockdown reduces the expression of IL-1β, IL-6 and inactivated NF-κB signaling in BCG-infected macrophages. Of note, DUSP5 specific siRNA increases the content of free fatty acids (FFAs) and triglyceride (TG), but represses the expression of FAO associated enzymes such as CPT1A and PPARα, suggesting DUSP5 mediated FAO during BCG infection. Moreover, Inhibiting FAO by pharmacological manner suppresses IL-1β, IL-6, TNF-α expression and relieves lung damage. Taken together, our data indicates DUSP5 mediates FAO reprogramming and promotes inflammatory response to BCG infection.

Polyphosphate kinase-1 regulates bacterial and host metabolic pathways involved in pathogenesis of Mycobacterium tuberculosis

Inorganic polyphosphate (polyP) is primarily synthesized by Polyphosphate Kinase-1 (PPK-1) and regulates numerous cellular processes, including energy metabolism, stress adaptation, drug tolerance, and microbial pathogenesis. Here, we report that polyP interacts with acyl CoA carboxylases, enzymes involved in lipid biosynthesis in Mycobacterium tuberculosis. We show that deletion of ppk-1 in M. tuberculosis results in transcriptional and metabolic reprogramming. In comparison to the parental strain, the Δppk-1 mutant strain had reduced levels of virulence-associated lipids such as PDIMs and TDM. We also observed that polyP deficiency in M. tuberculosis is associated with enhanced phagosome-lysosome fusion in infected macrophages and attenuated growth in mice. Host RNA-seq analysis revealed decreased levels of transcripts encoding for proteins involved in either type I interferon signaling or formation of foamy macrophages in the lungs of Δppk-1 mutant-infected mice relative to parental strain-infected animals. Using target-based screening and molecular docking, we have identified raloxifene hydrochloride as a broad-spectrum PPK-1 inhibitor. We show that raloxifene hydrochloride significantly enhanced the activity of isoniazid, bedaquiline, and pretomanid against M. tuberculosis in macrophages. Additionally, raloxifene inhibited the growth of M. tuberculosis in mice. This is an in-depth study that provides mechanistic insights into the regulation of mycobacterial pathogenesis by polyP deficiency.

Early innate cell interactions with Mycobacterium tuberculosis in protection and pathology of tuberculosis

Tuberculosis (TB) remains a significant global health challenge, claiming the lives of up to 1.5 million individuals annually. TB is caused by the human pathogen Mycobacterium tuberculosis (Mtb), which primarily infects innate immune cells in the lungs. These immune cells play a critical role in the host defense against Mtb infection, influencing the inflammatory environment in the lungs, and facilitating the development of adaptive immunity. However, Mtb exploits and manipulates innate immune cells, using them as favorable niche for replication. Unfortunately, our understanding of the early interactions between Mtb and innate effector cells remains limited. This review underscores the interactions between Mtb and various innate immune cells, such as macrophages, dendritic cells, granulocytes, NK cells, innate lymphocytes-iNKT and ILCs. In addition, the contribution of alveolar epithelial cell and endothelial cells that constitutes the mucosal barrier in TB immunity will be discussed. Gaining insights into the early cellular basis of immune reactions to Mtb infection is crucial for our understanding of Mtb resistance and disease tolerance mechanisms. We argue that a better understanding of the early host-pathogen interactions could inform on future vaccination approaches and devise intervention strategies.

Leprosy-specific subsets of macrophages and Schwann cells identified by single-cell RNA-sequencing

In Mycobacterium leprae (M. leprae)-infection, inflammatory cells' subsets and dynamics as well as the interactions with Schwann cells have remained elusive. We investigated individual cells in M. leprae-inoculated nude mice by single-cell RNA-sequencing (scRNA-seq). For macrophages, we dissected two M1-like subsets and five M2-like subsets, where lipid-associated signatures were pervasive in both M1-like and M2-like subsets. There were four macrophage trajectories showing: (i) pro-inflammatory (M1), (ii) lipid metabolism-related (M2), (iii) anti-inflammatory (M2), and (iv) interferon-stimulated gene-related (M2) fates. They displayed early divergence without ever rejoining along the paths, suggesting simultaneous or continuous stimuli for macrophage activation in leprosy. The scRNA-seq predicted Schwann cell-macrophage interactions (Notch1-Jag1, Plxnb1-Sema4d interactions). An immature Schwann cell subset showing Tfap2a expression was identified, indicating Schwann cell dedifferentiation in leprosy tissues. Expressions of Notch1, Jag1, Plxnb1, Sema4d, and Tfap2a were validated in mouse or human leprosy tissues by immunohistochemistry. We identified both pro-inflammatory and inflammation-resolution signatures, where lipid-associated signatures were pervasive to the macrophages, representing leprosy-specific macrophage states for prolonged and repeated episodes of inflammation and resolution. Our study identified refined molecular states and interactions of macrophages and Schwann cells, suggesting novel insights into the pathogenesis of unhealed inflammation with neuropathy and potential therapeutic targets for leprosy.

Revolutionizing control strategies against Mycobacterium tuberculosis infection through selected targeting of lipid metabolism

Lipid species play a critical role in the growth and virulence expression of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB). During Mtb infection, foamy macrophages accumulate lipids in granulomas, providing metabolic adaptation and survival strategies for Mtb against multiple stresses. Host-derived lipid species, including triacylglycerol and cholesterol, can also contribute to the development of drug-tolerant Mtb, leading to reduced efficacy of antibiotics targeting the bacterial cell wall or transcription. Transcriptional and metabolic analyses indicate that lipid metabolism-associated factors of Mtb are highly regulated by antibiotics and ultimately affect treatment outcomes. Despite the well-known association between major antibiotics and lipid metabolites in TB treatment, a comprehensive understanding of how altered lipid metabolites in both host and Mtb influence treatment outcomes in a drug-specific manner is necessary to overcome drug tolerance. The current review explores the controversies and correlations between lipids and drug efficacy in various Mtb infection models and proposes novel approaches to enhance the efficacy of anti-TB drugs. Moreover, the review provides insights into the efficacious control of Mtb infection by elucidating the impact of lipids on drug efficacy. This review aims to improve the effectiveness of current anti-TB drugs and facilitate the development of innovative therapeutic strategies against Mtb infection by making reverse use of Mtb-favoring lipid species.

Characteristics of plasma exosomes in drug-resistant tuberculosis patients

BACKGROUND

Increasing prevalence of drug-resistant tuberculosis (DR-TB) poses a major challenge to the early detection and effective control of tuberculosis (TB). Exosomes carrying proteins and nucleic acid mediate intercellular communication between host and pathogen including Mycobacterium tuberculosis. However, molecular events of exosomes indicating the status and development of DR-TB remain unknown. This study determined the proteomics of exosome in DR-TB and explored the potential pathogenesis of DR-TB.

METHODS

Plasma samples were collected from 17 DR-TB patients and 33 non-drug-resistant tuberculosis (NDR-TB) patients using grouped case-control study design. After exosomes of plasma were isolated and confirmed by compositional and morphological measurement for exosomal characteristics, a label-free quantitative proteomics of exosomes was performed and differential protein components were determined via bioinformatics analysis.

RESULTS

Compared with the NDR-TB group, we identified 16 up-regulated proteins and 10 down-regulated proteins in the DR-TB group. The down-regulated proteins were mainly apolipoproteins and mainly enriched in cholesterol metabolism-related pathways. Apolipoproteins family including APOA1, APOB, APOC1 were key proteins in protein-protein interaction network.

CONCLUSION

Differentially expressed proteins in the exosomes may indicate the status of DR-TB from NDR-TB. Apolipoproteins family including APOA1, APOB, APOC1 may be involved in the pathogenesis of DR-TB by regulating cholesterol metabolism via exosomes.

Metal-Organic Framework-Based Nanomedicines for the Treatment of Intracellular Bacterial Infections

Metal-organic frameworks (MOFs) are a highly versatile class of ordered porous materials, which hold great promise for different biomedical applications, including antibacterial therapy. In light of the antibacterial effects, these nanomaterials can be attractive for several reasons. First, MOFs exhibit a high loading capacity for numerous antibacterial drugs, including antibiotics, photosensitizers, and/or photothermal molecules. The inherent micro- or meso-porosity of MOF structures enables their use as nanocarriers for simultaneous encapsulation of multiple drugs resulting in a combined therapeutic effect. In addition to being encapsulated into an MOF's pores, antibacterial agents can sometimes be directly incorporated into an MOF skeleton as organic linkers. Next, MOFs contain coordinated metal ions in their structure. Incorporation of Fe^2/3+, Cu²⁺, Zn²⁺, Co²⁺, and Ag⁺ can significantly increase the innate cytotoxicity of these materials for bacteria and cause a synergistic effect. Finally, abundance of functional groups enables modifying the external surface of MOF particles with stealth coating and ligand moieties for improved drug delivery. To date, there are a number of MOF-based nanomedicines available for the treatment of bacterial infections. This review is focused on biomedical consideration of MOF nano-formulations designed for the therapy of intracellular infections such as Staphylococcus aureus, Mycobacterium tuberculosis, and Chlamydia trachomatis. Increasing knowledge about the ability of MOF nanoparticles to accumulate in a pathogen intracellular niche in the host cells provides an excellent opportunity to use MOF-based nanomedicines for the eradication of persistent infections. Here, we discuss advantages and current limitations of MOFs, their clinical significance, and their prospects for the treatment of the mentioned infections.

Adaptation to the intracellular environment of primary human macrophages influences drug susceptibility of Mycobacterium tuberculosis

As a facultative intracellular pathogen, M. tuberculosis (Mtb) is highly adapted to evading antibacterial mechanisms in phagocytic cells. Both the macrophage and pathogen experience transcriptional and metabolic changes from the onset of phagocytosis. To account for this interaction in the assessment of intracellular drug susceptibility, we allowed a 3-day preadaptation phase post-macrophage infection prior to drug treatment. We found that intracellular Mtb in human monocyte-derived macrophages (MDM) presents dramatic alterations in susceptibility to isoniazid, sutezolid, rifampicin and rifapentine when compared to axenic culture. Infected MDM gradually accumulate lipid bodies, adopting a characteristic appearance reminiscent of foamy macrophages in granulomas. Furthermore, TB granulomas in vivo develop hypoxic cores with decreasing oxygen tension gradients across their radii. Accordingly, we evaluated the effects of hypoxia on preadapted intracellular Mtb in our MDM model. We observed that hypoxia induced greater lipid body formation and no additional shifts in drug tolerance, suggesting that the adaptation of intracellular Mtb to baseline host cell conditions under normoxia dominates changes to intracellular drug susceptibility. Using unbound plasma concentrations in patients as surrogates for free drug concentrations in lung interstitial fluid, we estimate that intramacrophage Mtb in granulomas are exposed to bacteriostatic concentrations of most study drugs.

Integrated bioinformatic analyses investigate macrophage-M1-related biomarkers and tuberculosis therapeutic drugs

Tuberculosis (TB) is a common infectious disease linked to host genetics and the innate immune response. It is vital to investigate new molecular mechanisms and efficient biomarkers for Tuberculosis because the pathophysiology of the disease is still unclear, and there aren't any precise diagnostic tools. This study downloaded three blood datasets from the GEO database, two of which (GSE19435 and 83456) were used to build a weighted gene co-expression network for searching hub genes associated with macrophage M1 by the CIBERSORT and WGCNA algorithms. Furthermore, 994 differentially expressed genes (DEGs) were extracted from healthy and TB samples, four of which were associated with macrophage M1, naming RTP4, CXCL10, CD38, and IFI44. They were confirmed as upregulation in TB samples by external dataset validation (GSE34608) and quantitative real-time PCR analysis (qRT-PCR). CMap was used to predict potential therapeutic compounds for tuberculosis using 300 differentially expressed genes (150 downregulated and 150 upregulated genes), and six small molecules (RWJ-21757, phenamil, benzanthrone, TG-101348, metyrapone, and WT-161) with a higher confidence value were extracted. We used in-depth bioinformatics analysis to investigate significant macrophage M1-related genes and promising anti-Tuberculosis therapeutic compounds. However, more clinical trials were necessary to determine their effect on Tuberculosis.

Cardiovascular Involvement in Tuberculosis: From Pathophysiology to Diagnosis and Complications-A Narrative Review

Although primarily a lung disease, extra-pulmonary tuberculosis (TB) can affect any organ or system. Of these, cardiovascular complications associated with disease or drug toxicity significantly worsen the prognosis. Approximately 60% of patients with TB have a cardiovascular disease, the most common associated pathological entities being pericarditis, myocarditis, and coronary artery disease. We searched the electronic databases PubMed, MEDLINE, and EMBASE for studies that evaluated the impact of TB on the cardiovascular system, from pathophysiological mechanisms to clinical and paraclinical diagnosis of cardiovascular involvement as well as the management of cardiotoxicity associated with antituberculosis medication. The occurrence of pericarditis in all its forms and the possibility of developing constrictive pericarditis, the association of concomitant myocarditis with severe systolic dysfunction and complication with acute heart failure phenomena, and the long-term development of aortic aneurysms with risk of complications, as well as drug-induced toxicity, pose complex additional problems in the management of patients with TB. In the era of multidisciplinarity and polymedication, evidence-based medicine provides various tools that facilitate an integrative management that allows early diagnosis and treatment of cardiac pathologies associated with TB.

Expression of scavenger receptors CD163, CD204, and CD206 on macrophages in patients with pulmonary tuberculosis

The aim of the study was to evaluate the expression of scavenger receptors (CD163, CD204, CD206) on macrophages in patients with pulmonary tuberculosis, depending on the clinical form of the disease and sensitivity of the pathogen to anti-tuberculosis drugs.

Materials and methods. 64 patients with pulmonary tuberculosis (TB) were examined: 26 patients with disseminated pulmonary tuberculosis (DTB) and 38 patients with infiltrative pulmonary tuberculosis (ITB). Of these, 42 patients secreted Mycobacterium tuberculosis (MBT) sensitive to basic antituberculosis drugs (ATBD), and 22 patients secreted MBT resistant to first-line anti-TB drugs. Material for the study was venous blood. To isolate monocytes from the whole blood in order to transform them into macrophages, Ficoll density gradient centrifugation with a density of 1.077 g / cm3 was used followed by immunomagnetic separation of CD14+ cells. Monocytes were cultured in the X-VIVO 10 medium with gentamicin and phenol red with the addition of macrophage colony-stimulating factor (M-CSF) (5 ng / ml) at a concentration of 1×106 cells / ml with stimulators: interleukin (IL)-4 (10 ng / ml) and interferon (IFN) γ (100 ng / ml). Immunophenotyping of macrophages was performed using monoclonal antibodies to CD163, CD204, and CD206 on the Beckman Coulter CytoFLEX LX Flow Cytometer. The analysis of the obtained data was carried out using the CytExpert 2.0 software. The results were analyzed using statistical methods.

Results. Switching the phenotype of macrophages from the M1-like proinflammatory phenotype to M2-like antiinflammatory one contributes to the chronic course of pulmonary TB, dissemination, and persistence of infection. In the present study, we analyzed the features of the expression of CD163, CD204, and CD206 scavenger receptors on macrophages in patients with pulmonary TB. An increase in the number of macrophages carrying markers of the M2 subpopulation (CD163, CD204, and CD206) on their surface was noted, regardless of the clinical form of pulmonary TB and drug resistance of M. tuberculosis.

Conclusion. Studying the mechanisms underlying M1 or M2 activation of macrophages is necessary for a deeper understanding of the immunopathogenesis of TB and the role of innate immunity cells in protecting the body from mycobacteria. The analysis of the expression of scavenger receptors CD163, CD204, and CD206 on macrophages allowed to conclude that, in pulmonary TB, especially in patients with drug resistant M. tuberculosis and infiltrative TB, regulatory mechanisms that suppress the activation of innate immunity are implemented together with polarization of macrophage differentiation towards the M2 phenotype. It may be the cause of immune deficiency induced by the pathogen.

Mouse Models for Mycobacterium tuberculosis Pathogenesis: Show and Do Not Tell

Science has been taking profit from animal models since the first translational experiments back in ancient Greece. From there, and across all history, several remarkable findings have been obtained using animal models. One of the most popular models, especially for research in infectious diseases, is the mouse. Regarding research in tuberculosis, the mouse has provided useful information about host and bacterial traits related to susceptibility to the infection. The effect of aging, sexual dimorphisms, the route of infection, genetic differences between mice lineages and unbalanced immunity scenarios upon Mycobacterium tuberculosis infection and tuberculosis development has helped, helps and will help biomedical researchers in the design of new tools for diagnosis, treatment and prevention of tuberculosis, despite various discrepancies and the lack of deep study in some areas of these traits.

A Persistent Tuberculosis Outbreak in the UK Is Characterized by Hydrophobic fadB4-Deficient Mycobacterium tuberculosis That Replicates Rapidly in Macrophages

The genetic diversity of Mycobacterium tuberculosis can influence disease severity and transmissibility. To better understand how this diversity influences individuals and communities, we phenotyped M. tuberculosis that was causing a persistent outbreak in the East Midlands, United Kingdom. Compared to nonoutbreak isolates, bacilli had higher lipid contents and more hydrophobic cell surfaces. In macrophage infection models, the bacteria increased more rapidly, provoked the enhanced accumulation of macrophage lipid droplets and enhanced the secretion of IL-1β. Natural deletions in fadB4, nrdB, and plcC distinguished the outbreak isolates from other lineage 3 isolates in the region. fadB4 is annotated with a putative role in cell envelope biosynthesis, so the loss of this gene has the potential to alter the interactions of bacteria with immune cells. Reintroduction of fadB4 to the outbreak strain led to a phenotype that more closely resembled those of nonoutbreak strains. The improved understanding of the microbiological characteristics and the corresponding genetic polymorphisms that associate with outbreaks have the potential to inform tuberculosis control. IMPORTANCE Tuberculosis (TB) killed 1.5 million people in 2020 and affects every country. The extent to which the natural genetic diversity of Mycobacterium tuberculosis influences disease manifestation at both the individual and epidemiological levels remains poorly understood. Insights into how pathogen polymorphisms affect patterns of TB have the potential to translate into clinical and public health practice. Two distinct lineage 3 strains isolated from local TB outbreaks, one of which (CH) was rapidly terminated and the other of which (Lro) persistently transmitted for over a decade, provided us with an opportunity to study these issues. We compared genome sequences, microbiological characteristics, and early immune responses that were evoked upon infection. Our results indicate that the natural lack of fadB4 in the Lro strain contributes to its unique features.

Airway microecology in rifampicin-resistant and rifampicin-sensitive pulmonary tuberculosis patients

BACKGROUND

Pulmonary tuberculosis is a chronic infectious disease of the respiratory system. It is still one of the leading causes of death from a single infectious disease, but it has been stuck in the study of a single pathogen. Recent studies have shown that many diseases are associated with disruption of the native microbiota. In this study we investigated the occurrence of tuberculosis and the correlation between drug resistance and respiratory flora. High-throughput 16 S rRNA gene sequencing was used to characterize the respiratory microbiota composition of 30 tuberculosis (TB) affected patients and compared with 30 healthy (H) controls. According to their Gene Xpert results, 30 pulmonary tuberculosis patients were divided into 12 persons in the drug-sensitive group (DS0) and 18 persons in the drug-resistant group (DR0). The microbial flora of the two were compared with the H group.

RESULTS

The data generated by sequencing showed that Firmicutes, Proteus, Bacteroides, Actinomyces and Fusobacterium were the five main bacterial phyla detected, and they constituted more than 96% of the microbial community. The relative abundances of Fusobacterium, Haemophilus, Porphyromonas, Neisseria, TM7, Spirochetes, SR1, and Tenericutes in the TB group was lower than that of the H group, and Granulicatella was higher than the H group. The PcoA diagrams of the two groups had obvious clustering differences. The Alpha diversity of the TB group was lower than that of the H group, and the Beta diversity was higher than that of the H group (P < 0.05). The relative abundance of Streptococcus in the DS0 group was significantly higher than that in the DR0 group (P < 0.05).

CONCLUSION

Pulmonary tuberculosis can cause disorders of the respiratory tract microbial flora, in which the relative abundance of Streptococcus was significantly different between rifampicin-sensitive and rifampicin-resistant patients.

Mycobacterium tuberculosis Rv0790c inhibits the cellular autophagy at its early stage and facilitates mycobacterial survival

Rv0790c is predicted to be a conserved hypothetical protein encoded by Mycobacterium tuberculosis (Mtb). However, its function in Mtb infection remains largely unknown. In this study, we found that Rv0790c promoted bacillary survival of M. smegmatis (Ms), both in vitro and in vivo. The bacillary burden of Ms exogenously expressing Rv0790c increased, whereas in Rv0790c-knockouts the bacillary burden decreased in infected macrophages. Multiple cellular processes were analyzed to explore the underlying mechanisms. We found that neither inflammatory regulation nor apoptotic induction were responsible for the promotion of bacillary survival mediated by Rv0790c. Interestingly, we found that Rv0790c facilitates mycobacterial survival through cellular autophagy at its early stage. Immunoprecipitation assay of autophagy initiation-related proteins indicated that Rv0790c interacted with mTOR and enhanced its activity, as evidenced by the increased phosphorylation level of mTOR downstream substrates, ULK-1, at Ser757 and P70S6K, at Thr389. Our study uncovers a novel autophagy suppressor encoded by mycobacterial Rv0790c, which inhibits the early stage of cellular autophagy induction upon Mtb infection and takes an important role in maintaining intracellular mycobacterial survival. It may aid in understanding the mechanism of Mtb evasion of host cellular degradation, as well as hold the potential to develop new targets for the prevention and treatment of tuberculosis.

Transcription factor MAFB controls type I and II interferon response-mediated host immunity in Mycobacterium tuberculosis-infected macrophages

MAFB, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B, has been identified as a candidate gene for early tuberculosis (TB) onset in Thai and Japanese populations. Here, we investigated the genome-wide transcriptional profiles of MAFB-knockdown (KD) macrophages infected with Mycobacterium tuberculosis (Mtb) to highlight the potential role of MAFB in host immunity against TB. Gene expression analysis revealed impaired type I and type II interferon (IFN) responses and enhanced oxidative phosphorylation in MAFB-KD macrophages infected with Mtb. The expression of inflammatory chemokines, including IFN-γ-inducible genes, was confirmed to be significantly reduced by knockdown of MAFB during Mtb infection. A similar effect of MAFB knockdown on type I and type II IFN responses and oxidative phosphorylation was also observed when Mtb-infected macrophages were activated by IFN-γ. Taken together, our results demonstrate that MAFB is involved in the immune response and metabolism in Mtb-infected macrophages, providing new insight into MAFB as a candidate gene to guide further study to control TB.

Spatial multiomic profiling reveals the novel polarization of foamy macrophages within necrotic granulomatous lesions developed in lungs of C3HeB/FeJ mice infected with Mycobacterium tuberculosis

Infection with Mycobacterium tuberculosis leads to the development of tuberculosis (TB) with the formation of granulomatous lesions. Foamy macrophages (FM) are a hallmark of TB granulomas, because they provide the primary platform of M. tuberculosis proliferation and the main source of caseous necrosis. In this study, we applied spatial multiomic profiling to identify the signatures of FM within the necrotic granulomas developed in a mouse model resembling human TB histopathology. C3HeB/FeJ mice were infected with M. tuberculosis to induce the formation of necrotic granulomas in the lungs. Using laser microdissection, necrotic granulomas were fractionated into three distinct regions, including the central caseous necrosis, the rim containing FM, and the peripheral layer of macrophages and lymphocytes, and subjected to proteomic and transcriptomic analyses. Comparison of proteomic and transcriptomic analyses of three distinct granulomatous regions revealed that four proteins/genes are commonly enriched in the rim region. Immunohistochemistry confirmed the localization of identified signatures to the rim of necrotic granulomas. We also investigated the localization of the representative markers for M1 macrophages in granulomas because the signatures of the rim included M2 macrophage markers. The localization of both macrophage markers suggests that FM in necrotic granulomas possessed the features of M1 or M2 macrophages. Gene set enrichment analysis of transcriptomic profiling revealed the upregulation of genes related to M2 macrophage activation and mTORC1 signaling in the rim. These results will provide new insights into the process of FM biogenesis, leading to further understanding of the pathophysiology of TB granulomas.

Host-directed therapies in pulmonary tuberculosis: Updates on anti-inflammatory drugs

Tuberculosis (TB) is a lethal disease and remains one of the top ten causes of mortality by an infectious disease worldwide. It can also result in significant morbidity related to persistent inflammation and tissue damage. Pulmonary TB treatment depends on the prolonged use of multiple drugs ranging from 6 months for drug-susceptible TB to 6–20 months in cases of multi-drug resistant disease, with limited patient tolerance resulting from side effects. Treatment success rates remain low and thus represent a barrier to TB control. Adjunct host-directed therapy (HDT) is an emerging strategy in TB treatment that aims to target the host immune response to Mycobacterium tuberculosis in addition to antimycobacterial drugs. Combined multi-drug treatment with HDT could potentially result in more effective therapies by shortening treatment duration, improving cure success rates and reducing residual tissue damage. This review explores the rationale and challenges to the development and implementation of HDTs through a succinct report of the medications that have completed or are currently being evaluated in ongoing clinical trials.

Comprehensive lipid and lipid-related gene investigations of host immune responses to characterize metabolism-centric biomarkers for pulmonary tuberculosis

Despite remarkable success in the prevention and treatment of tuberculosis (TB), it remains one of the most devastating infectious diseases worldwide. Management of TB requires an efficient and timely diagnostic strategy. In this study, we comprehensively characterized the plasma lipidome of TB patients, then selected candidate lipid and lipid-related gene biomarkers using a data-driven, knowledge-based framework. Among 93 lipids that were identified as potential biomarker candidates, ether-linked phosphatidylcholine (PC O–) and phosphatidylcholine (PC) were generally upregulated, while free fatty acids and triglycerides with longer fatty acyl chains were downregulated in the TB group. Lipid-related gene enrichment analysis revealed significantly altered metabolic pathways (e.g., ether lipid, linolenic acid, and cholesterol) and immune response signaling pathways. Based on these potential biomarkers, TB patients could be differentiated from controls in the internal validation (random forest model, area under the curve [AUC] 0.936, 95% confidence interval [CI] 0.865–0.992). PC(O-40:4), PC(O-42:5), PC(36:0), and PC(34:4) were robust biomarkers able to distinguish TB patients from individuals with latent infection and healthy controls, as shown in the external validation. Small changes in expression were identified for 162 significant lipid-related genes in the comparison of TB patients vs. controls; in the random forest model, their utilities were demonstrated by AUCs that ranged from 0.829 to 0.956 in three cohorts. In conclusion, this study introduced a potential framework that can be used to identify and validate metabolism-centric biomarkers.

The 1, 2-ethylenediamine SQ109 protects against tuberculosis by promoting M1 macrophage polarization through the p38 MAPK pathway

Directly Observed Treatment Short-course (DOTs), is an effective and widely recommended treatment for tuberculosis (TB). The antibiotics used in DOTs, are immunotoxic and impair effector T cells, increasing the risk of re-infections and reactivation. Multiple reports suggest that addition of immune-modulators along with antibiotics improves the effectiveness of TB treatment. Therefore, drugs with both antimicrobial and immunomodulatory properties are desirable. N¹-(Adamantan-2-yl)-N²-[(2E)-3,7-dimethylocta-2,6-dien-1-yl]ethane-1,2-diamine (SQ109) is an asymmetric diamine derivative of adamantane, that targets Mycobacterial membrane protein Large 3 (MmpL3). SQ109 dissipates the transmembrane electrochemical proton-gradient necessary for cell-wall biosynthesis and bacterial activity. Here, we examined the effects of SQ109 on host-immune responses using a murine TB model. Our results suggest the pro-inflammatory nature of SQ109, which instigates M1-macrophage polarization and induces protective pro-inflammatory cytokines through the p38-MAPK pathway. SQ109 also promotes Th1 and Th17-immune responses that inhibit the bacillary burden in a murine model of TB. These findings put forth SQ109 as a potential-adjunct to TB antibiotic therapy.

The adamantine derivative SQ109 induces protective pro-inflammatory cytokines and promotes Th1 and Th17-immune responses that inhibit bacterial burden in a tuberculosis mouse model.

Recent Advances in Host-Directed Therapies for Tuberculosis and Malaria

Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis, and malaria, caused by parasites from the Plasmodium genus, are two of the major causes of death due to infectious diseases in the world. Both diseases are treatable with drugs that have microbicidal properties against each of the etiologic agents. However, problems related to treatment compliance by patients and emergence of drug resistant microorganisms have been a major problem for combating TB and malaria. This factor is further complicated by the absence of highly effective vaccines that can prevent the infection with either M. tuberculosis or Plasmodium. However, certain host biological processes have been found to play a role in the promotion of infection or in the pathogenesis of each disease. These processes can be targeted by host-directed therapies (HDTs), which can be administered in conjunction with the standard drug treatments for each pathogen, aiming to accelerate their elimination or to minimize detrimental side effects resulting from exacerbated inflammation. In this review we discuss potential new targets for the development of HDTs revealed by recent advances in the knowledge of host-pathogen interaction biology, and present an overview of strategies that have been tested in vivo, either in experimental models or in patients.

Foamy macrophages potentially inhibit tuberculous wound healing by inhibiting the TLRs/NF-κB signalling pathway

To characterise the distribution, classification, and quantity of foamy macrophages (FMs) in tuberculous wound tissue and the relationship between FM and delayed healing of tuberculous wounds. Morphological studies were performed to explore the distribution of FM and Mycobacterium tuberculosis (Mtb) in tuberculous wounds, with acute and chronic wounds included for comparison. Phorbol-12-myristate-13-acetate stimulation-differentiated THP-1 cells were treated with Mtb to induce their differentiation into FM with oxidised low-density lipoprotein treatment serving as a control. Relative cytokine levels were determined by quantitative PCR and Western blotting. Varied co-culture combinations of Mtb, THP-1, FM, and fibroblasts were performed, and proliferation, migration, ability to contract collagen gel, and protein levels of the chemokines in the supernatants of the fibroblasts were assessed. The differentially expressed genes in human skin fibroblasts (HSFs) after co-culture with or without FM were identified using microarray. Many FM were found in the tissues of tuberculous wounds. The FM that did not engulf Mtb (NM-FM) were mainly distributed in tissues surrounding tuberculous wounds, whereas the FM that engulfed Mtb (M-FM) were dominantly located within granulomatous tissues. Co-culture experiments showed that, with the Mtb co-culture, the portions of NM-FM in the total FM grew over time. The migration, proliferation, chemokine secretion, and the ability of fibroblasts to contract collagen gel were inhibited when co-cultured with Mtb, FM, or a combination of the two. Further investigation showed that the TLRs/NF-κB signalling pathway is involved in fibroblast function under the stimulation of FM. TLRs and NF-κB agonists could reverse the phenotypic changes in HSFs after co-culture with FM. The tuberculous wound microenvironment composed of Mtb and FM may affect wound healing by inhibiting the functions of fibroblasts. FM potentially inhibit fibroblasts' function by inhibiting the TLRs/NF-κB signalling pathway in tuberculous wounds.

PPARγ Ameliorates Mycobacterium tuberculosis H37Ra-Induced Foamy Macrophage Formation via the ABCG1-Dependent Cholesterol Efflux Pathway in THP-1 Macrophages

Foamy macrophages are present during the course of Mycobacterium tuberculosis (Mtb) infection and seems to be nutrient-rich reservoir and secure reservoir for the bacilli, which leads to bacterial persistence and infection transmission. Peroxisome proliferator activated receptor γ (PPARγ) is a key transcription factor for cholesterol metabolism in macrophages and its role in regulating atherosclerosis related foamy macrophages (FMs) formation has been well-studied. However, knowledge about the mechanism of PPARγ regulating Mtb infection induced FM formation remains very limited. In this study, we investigate the functional role of PPARγ in Mtb H37Ra infection-induced foamy macrophages formation. H37Ra infection induced a time-dependent decreased expression of PPARγ that paralleled the augmented lipid body formation in THP1-derived macrophages. PPARγ antagonist GW9662 significantly potentiate H37Ra induced lipid body formation and inhibit ABCG1 expression, overexpression of ABCG1 by transduced macrophages with lentivirus significantly reversed the promotion effect of GW9662 on FM formation. Moreover, Treatment with a TLR2 neutralizing antibody ameliorated the activation of ABCG1 by Mtb H37Ra without significantly effecting the suppression of PPARγ, suggesting a greater role for TLR2 to regulate ABCG1 compared to PPARγ. Overall, this study showed that PPARγ is involved in ameliorating FM formation by regulating ABCG1 expression, these observations expose a novel role of PPARγ in the Mtb infection induced FM formation.

Host lipidome and tuberculosis treatment failure

INTRODUCTION

Host lipids play important roles in tuberculosis (TB) pathogenesis. Whether host lipids at TB treatment initiation (baseline) affect subsequent treatment outcomes has not been well characterised. We used unbiased lipidomics to study the prospective association of host lipids with TB treatment failure.

METHODS

A case-control study (n=192), nested within a prospective cohort study, was used to investigate the association of baseline plasma lipids with TB treatment failure among adults with pulmonary TB. Cases (n=46) were defined as TB treatment failure, while controls (n=146) were those without failure. Complex lipids and inflammatory lipid mediators were measured using liquid chromatography mass spectrometry techniques. Adjusted least-square regression was used to assess differences in groups. In addition, machine learning identified lipids with highest area under the curve (AUC) to classify cases and controls.

RESULTS

Baseline levels of 32 lipids differed between controls and those with treatment failure after false discovery rate adjustment. Treatment failure was associated with lower baseline levels of cholesteryl esters and oxylipin, and higher baseline levels of ceramides and triglycerides compared to controls. Two cholesteryl ester lipids combined in a unique classifier model provided an AUC of 0.79 (95% CI 0.65-0.93) in the test dataset for prediction of TB treatment failure.

CONCLUSIONS

We identified lipids, some with known roles in TB pathogenesis, associated with TB treatment failure. In addition, a lipid signature with prognostic accuracy for TB treatment failure was identified. These lipids could be potential targets for risk-stratification, adjunct therapy and treatment monitoring.

Progress of the Art of Macrophage Polarization and Different Subtypes in Mycobacterial Infection

Mycobacteriosis, mostly resulting from Mycobacterium tuberculosis (MTb), nontuberculous mycobacteria (NTM), and Mycobacterium leprae (M. leprae), is the long-standing granulomatous disease that ravages several organs including skin, lung, and peripheral nerves, and it has a spectrum of clinical-pathologic features based on the interaction of bacilli and host immune response. Histiocytes in infectious granulomas mainly consist of infected and uninfected macrophages (Mφs), multinucleated giant cells (MGCs), epithelioid cells (ECs), and foam cells (FCs), which are commonly discovered in lesions in patients with mycobacteriosis. Granuloma Mφ polarization or reprogramming is the crucial appearance of the host immune response to pathogen aggression, which gets a command of endocellular microbe persistence. Herein, we recapitulate the current gaps and challenges during Mφ polarization and the different subpopulations of mycobacteriosis.

Early Lesion of Post-Primary Tuberculosis: Subclinical Driver of Disease and Target for Vaccines and Host-Directed Therapies

The characteristic lesion of primary tuberculosis is the granuloma as is widely studied in human tissues and animal models. Post-primary tuberculosis is different. It develops only in human lungs and begins as a prolonged subclinical obstructive lobular pneumonia that slowly accumulates mycobacterial antigens and host lipids in alveolar macrophages with nearby highly sensitized T cells. After several months, the lesions undergo necrosis to produce a mass of caseous pneumonia large enough to fragment and be coughed out to produce a cavity or be retained as the focus of a post-primary granuloma. Bacteria grow massively on the cavity wall where they can be coughed out to infect new people. Here we extend these findings with the demonstration of secreted mycobacterial antigens, but not acid fast bacilli (AFB) of M. tuberculosis in the cytoplasm of ciliated bronchiolar epithelium and alveolar pneumocytes in association with elements of the programmed death ligand 1 (PD-L1), cyclo-oxygenase (COX)-2, and fatty acid synthase (FAS) pathways in the early lesion. This suggests that M. tuberculosis uses its secreted antigens to coordinate prolonged subclinical development of the early lesions in preparation for a necrotizing reaction sufficient to produce a cavity, post-primary granulomas, and fibrocaseous disease.

PE_PGRS3 ensures provision of the vital phospholipids cardiolipin and phosphatidylinositols by promoting the interaction between M. tuberculosis and host cells

PE_PGRS proteins of Mycobacterium tuberculosis (Mtb) constitute a large family of complex modular proteins whose role is still unclear. Among those, we have previously shown, using the heterologous expression in Mycobacterium smegmatis, that PE_PGRS3 containing a unique arginine-rich C-terminal domain, promotes adhesion to host cells. In this study, we investigate the role of PE_PGRS3 and its C-terminal domain directly in Mtb using functional deletion mutants. The results obtained here show that PE_PGRS3 is localized on the mycobacterial cell wall and its arginine-rich C-terminal region protrudes from the mycobacterial membrane and mediates Mtb entry into epithelial cells. Most importantly, this positively charged helical domain specifically binds phosphorylated phosphatidylinositols and cardiolipin, whereas it is unable to bind other phospholipids. Interestingly, administration of cardiolipin and phosphatidylinositol but no other phospholipids was able to turn-off expression of pe_pgrs3 activated by phosphate starvation conditions. These findings suggest that PE_PGRS3 has the key role to serve as a bridge between mycobacteria and host cells by interacting with specific host phospholipids and extracting them from host cells, for their direct integration or as a source of phosphate, during phases of TB pathogenesis when Mtb is short of phosphate supply.

Systematic measurement of combination-drug landscapes to predict in vivo treatment outcomes for tuberculosis

Lengthy multidrug chemotherapy is required to achieve a durable cure in tuberculosis. However, we lack well-validated, high-throughput in vitro models that predict animal outcomes. Here, we provide an extensible approach to rationally prioritize combination therapies for testing in in vivo mouse models of tuberculosis. We systematically measured Mycobacterium tuberculosis response to all two- and three-drug combinations among ten antibiotics in eight conditions that reproduce lesion microenvironments, resulting in >500,000 measurements. Using these in vitro data, we developed classifiers predictive of multidrug treatment outcome in a mouse model of disease relapse and identified ensembles of in vitro models that best describe in vivo treatment outcomes. We identified signatures of potencies and drug interactions in specific in vitro models that distinguish whether drug combinations are better than the standard of care in two important preclinical mouse models. Our framework is generalizable to other difficult-to-treat diseases requiring combination therapies. A record of this paper's transparent peer review process is included in the supplemental information.

Game theory applications in host-microbe interactions toward disease manifestation: Mycobacterium tuberculosis infection as an example

OBJECTIVES

Game theory describes the interactions between two players and the pay-off from winning, losing, or compromising. In the present study, Mycobacterium tuberculosis (Mtb)-host interactions were used as an example for the application of game theory to describe and predict the different outcomes of Mtb-infection and introducing target molecules for use in protection or therapy.

MATERIALS AND METHODS

The gene expression for eight main markers (CCR1, CCR2, IDO, Tbet, TGFβ, iNOS, MMP3, MMP9) of host response and three Mtb virulence factors (Ag85B, CFP-10, ESAT-6) were assessed in broncho-alveolar lavage of TB⁺ and TB^- patients.

RESULTS

The players' strategies in the "Nash equilibrium", showed that Ag85B is the main virulence factor for Mtb in active phase, and also the most immunogenic factor, if the host can respond by high expression of T-bet and iNOS toward a Th1 response. In this situation, Mtb can express high levels of ESAT-6 and CFP10 and change the game to the latency, in which host responses by medium expression of T-bet and iNOS and medium level of TGF-β and IDO. Consistently, the IDO expression was 134-times higher in TB⁺s than the TB^-s,and the T-bet expression,~200-times higher in the TB^-s than the TB⁺s. Furthermore, Mtb-Ag85B had a strong positive association with CCR2, T-bet and iNOS, but had a negative correlation with IDO.

CONCLUSION

Ag85B and maybe ESAT6 (without its suppressive C-terminal) should be considered for making subunit vaccines. And, preventing IDO formation in dendritic cells might be a novel target for immunotherapy of tuberculosis, to reduce the pressure of immune-suppression on Th1 responses.

Ang II-Induced Hypertension Exacerbates the Pathogenesis of Tuberculosis

It has been known that infection plays a role in the development of hypertension. However, the role of hypertension in the progression of infectious diseases remain unknown. Many countries with high rates of hypertension show geographical overlaps with those showing high incidence rates of tuberculosis (TB). To explore the role of hypertension in tuberculosis, we compared the effects of hypertension during mycobacterial infection, we infected both hypertensive Angiotensin II (Ang II) and control mice with Mycobacterium tuberculosis (Mtb) strain H37Ra by intratracheal injection. Ang II-induced hypertension promotes cell death through both apoptosis and necrosis in Mtb H37Ra infected mouse lungs. Interestingly, we found that lipid accumulation in pulmonary tissues was significantly increased in the hypertension group compared to the normal controls. Ang II-induced hypertension increases the formation of foamy macrophages during Mtb infection and it leads to cell death. Moreover, the hypertension group showed more severe granuloma formation and fibrotic lesions in comparison with the control group. Finally, we observed that the total number of mycobacteria was increased in the lungs in the hypertension group compared to the normal controls. Taken together, these results suggest that hypertension increases intracellular survival of Mtb through formation of foamy macrophages, resulting in severe pathogenesis of TB.

Novel Role for Macrophage Galactose-Type Lectin-1 to Regulate Innate Immunity against Mycobacterium tuberculosis

Tuberculosis (TB) caused by infection with Mycobacterium tuberculosis is characterized by inflammatory pathology and poorly understood mechanisms of innate immunity. Pattern recognition receptors, expressed on the surface of macrophages, determine the balance of inflammatory and antimicrobial functions that influence disease outcome. Carbohydrate moieties displayed by mycobacteria can serve as pattern recognition receptor ligands for some members of the C-type lectin receptor (CLR) family, interactions that mediate a variety of incompletely understood immune outcomes. This work identifies a novel role for the CLR macrophage galactose-type lectin (MGL)-1 in a mouse model (C57BL/6 and MGL-1^-/-) of experimental TB. Murine macrophages upregulated MGL-1 following in vitro exposure to M. tuberculosis, whereas MGL⁺ cells accumulated at sites of mycobacteria-driven inflammation in the lung. Pulmonary macrophages from MGL-1-deficient mice displayed increased production of proinflammatory cytokines (IL-1β, IL-6, and IFN-γ) that were associated with greater lipid accumulation, following M. tuberculosis infection. Surprisingly, for a CLR, we also observed MGL-1-dependent antimycobacterial activity as evidenced by greater M. tuberculosis proliferation in bone marrow-derived macrophages, and the lung, of MGL-1-deficient mice. Differential transcriptome analysis further revealed that loss of MGL-1 perturbs the activation of various genes involved in the regulation of inflammation and lipid metabolism in the setting of M. tuberculosis infection. These results identify MGL-1 signaling as an important mechanism that regulates innate immunity against M. tuberculosis and indicates the potential for the MGL pathway as a novel therapeutic target for anti-TB immunity.

Key Macrophage Responses to Infection With Mycobacterium tuberculosis Are Co-Regulated by microRNAs and DNA Methylation

Tuberculosis (TB) is the leading cause of death from infection with a single bacterial pathogen. Host macrophages are the primary cell type infected with Mycobacterium tuberculosis (Mtb), the organism that causes TB. Macrophage response pathways are regulated by various factors, including microRNAs (miRNAs) and epigenetic changes that can shape the outcome of infection. Although dysregulation of both miRNAs and DNA methylation have been studied in the context of Mtb infection, studies have not yet investigated how these two processes may jointly co-regulate critical anti-TB pathways in primary human macrophages. In the current study, we integrated genome-wide analyses of miRNA abundance and DNA methylation status with mRNA transcriptomics in Mtb-infected primary human macrophages to decipher which macrophage functions may be subject to control by these two types of regulation. Using in vitro macrophage infection models and next generation sequencing, we found that miRNAs and methylation changes co-regulate important macrophage response processes, including immune cell activation, macrophage metabolism, and AMPK pathway signaling.

Effective host-directed therapy for tuberculosis by targeted depletion of myeloid-derived suppressor cells and related cells using a diphtheria toxin-based fusion protein

Myeloid-derived suppressor cells (MDSCs) are present in elevated numbers in TB patients and have been found to be permissive for Mycobacterium tuberculosis (Mtb) proliferation. To determine whether depletion of MDSCs may improve host control of TB, we used a novel diphtheria toxin-based fusion protein known as DABIL-4 that targets and depletes IL-4-receptor positive cells. We show that DABIL-4 depletes both PMN-MDSCs and M-MDSC, increases IFNγ + T-cells, and reduces the lung bacillary burden in the mouse TB model. These results indicate that MDSC-depleting therapies targeting the IL-4 receptor are beneficial in TB and offer an avenue towards host-directed TB therapy.

Transcription Factors Interplay Orchestrates the Immune-Metabolic Response of Leishmania Infected Macrophages

Leishmaniasis is a group of heterogenous diseases considered as an important public health problem in several countries. This neglected disease is caused by over 20 parasite species of the protozoa belonging to the Leishmania genus and is spread by the bite of a female phlebotomine sandfly. Depending on the parasite specie and the immune status of the patient, leishmaniasis can present a wide spectrum of clinical manifestations. As an obligate intracellular parasite, Leishmania colonize phagocytic cells, mainly the macrophages that orchestrate the host immune response and determine the fate of the infection. Once inside macrophages, Leishmania triggers different signaling pathways that regulate the immune and metabolic response of the host cells. Various transcription factors regulate such immune-metabolic responses and the associated leishmanicidal and inflammatory reaction against the invading parasite. In this review, we will highlight the most important transcription factors involved in these responses, their interactions and their impact on the establishment and the progression of the immune response along with their effect on the physiopathology of the disease.

Mycobacterium tuberculosis Load in Host Cells and the Antibacterial Activity of Alveolar Macrophages Are Linked and Differentially Regulated in Various Lung Lesions of Patients with Pulmonary Tuberculosis

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis (Mtb) infection with the formation of a broad range of abnormal lung lesions within a single patient. Although host-pathogen interactions determine disease outcome, they are poorly understood within individual lesions at different stages of maturation. We compared Mtb load in a tuberculoma wall and the lung tissue distant from tuberculomas in TB patients. These data were combined with an analysis of activation and bactericidal statuses of alveolar macrophages and other cell subtypes examined both in ex vivo culture and on the histological sections obtained from the same lung lesions. The expression of pattern recognition receptors CD14, CD11b, and TLR-2, transcription factors HIF-1α, HIF-2α, and NF-κB p50 and p65, enzymes iNOS and COX-2, reactive oxygen species (ROS) biosynthesis, and lipid production were detected for various lung lesions, with individual Mtb loads in them. The walls of tuberculomas with insufficient inflammation and excessive fibrosis were identified as being the main niche for Mtb survival (single or as colonies) in non-foamy alveolar macrophages among various lung lesions examined. The identification of factors engaged in the control of Mtb infection and tissue pathology in local lung microenvironments, where host-pathogen relationships take place, is critical for the development of new therapeutic strategies.

Understanding Metabolic Regulation Between Host and Pathogens: New Opportunities for the Development of Improved Therapeutic Strategies Against Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) causes chronic granulomatous lung disease in humans. Recently, novel strategies such as host-directed therapeutics and adjunctive therapies that enhance the effect of existing antibiotics have emerged to better control Mtb infection. Recent advances in understanding the metabolic interplay between host immune cells and pathogens have provided new insights into how their interactions ultimately influence disease outcomes and antibiotic-treatment efficacy. In this review, we describe how metabolic cascades in immune environments and relevant metabolites produced from immune cells during Mtb infection play critical roles in the progression of diseases and induction of anti-Mtb protective immunity. In addition, we introduce how metabolic alterations in Mtb itself can lead to the development of persister cells that are resistant to host immunity and can eventually evade antibiotic attacks. Further understanding of the metabolic link between host cells and Mtb may contribute to not only the prevention of Mtb persister development but also the optimization of host anti-Mtb immunity together with enhanced efficacy of existing antibiotics. Overall, this review highlights novel approaches to improve and develop host-mediated therapeutic strategies against Mtb infection by restoring and switching pathogen-favoring metabolic conditions with host-favoring conditions.

Protective Immunity Against Neospora caninum Infection Induced by 14-3-3 Protein in Mice

Neospora caninum is an apicomplexan parasite that infects many mammals and remains a threatening disease worldwide because of the lack of effective drugs and vaccines. Our previous studies demonstrated that N. caninum 14-3-3 protein (Nc14-3-3), which is included in N. caninum extracellular vesicles (NEVs), can induce effective immune responses and stimulate cytokine expression in mouse peritoneal macrophages. However, whether Nc14-3-3 has a protective effect and its mechanisms are poorly understood. Here, we evaluated the immune responses and protective effects of Nc14-3-3 against exposure to 2 × 10⁷ Nc-1 tachyzoites. Antibody (IgG, IgGl, and IgG2a) levels and Th1-type (IFN-γ and IL-12) and Th2-type (IL-4 and IL-10) cytokines in mouse serum, survival rates, survival times, and parasite burdens were detected. In the present study, the immunostimulatory effect of Nc14-3-3 was confirmed, as it triggered Th1-type cytokine (IFN-γ and IL-12) production in mouse serum 2 weeks after the final immunization. Moreover, the immunization of C57BL/6 mice with Nc14-3-3 induced high IgG antibody levels and significant increases in CD8⁺ T lymphocytes in the spleens of mice, indicating that the cellular immune response was significantly stimulated. Mouse survival rates and times were significantly prolonged after immunization; the survival rates were 40% for Nc14-3-3 immunization and 60% for NEV immunization, while mice that received GST, PBS, or blank control all died at 13, 9, or 8 days, respectively, after intraperitoneal N. caninum challenge. In addition, qPCR analysis indicated that there was a reduced parasite burden and diminished pathological changes in the mice immunized with Nc14-3-3. Our data demonstrate that vaccination of mice with Nc14-3-3 elicits both cellular and humoral immune responses and provides partial protection against acute neosporosis. Thus, Nc14-3-3 could be an effective antigen candidate for vaccine development for neosporosis.