Mycobacterium tuberculosis hijacks host macrophages-derived interleukin 16 to block phagolysosome maturation for enhancing intracellular growth

The discovery of promising cytokines and clarification of their immunological mechanisms in controlling the intracellular fate of Mycobacterium tuberculosis (Mtb) are necessary to identify effective diagnostic biomarkers and therapeutic targets. To escape immune clearance, Mtb can manipulate and inhibit the normal host process of phagosome maturation. Phagosome maturation arrest by Mtb involves multiple effectors and much remains unknown about this important aspect of Mtb pathogenesis. In this study, we found that interleukin 16 (IL-16) is elevated in the serum samples of Tuberculosis (TB) patients and can serve as a specific target for treatment TB. There was a significant difference in IL-16 levels among active TB, latent TB infection (LTBI), and non-TB patients. This study first revealed that macrophages are the major source of IL-16 production in response to Mtb infection, and elucidated that IL-16 can promote Mtb intracellular survival by inhibiting phagosome maturation and suppressing the expression of Rev-erbα which can inhibit IL-10 secretion. The experiments using zebrafish larvae infected with M. marinum and mice challenged with H37Rv demonstrated that reducing IL-16 levels resulted in less severe pathology and improved survival, respectively. In conclusion, this study provided direct evidence that Mtb hijacks the host macrophages-derived interleukin 16 to enhance intracellular growth. It is suggesting the immunosuppressive role of IL-16 during Mtb infection, supporting IL-16 as a promising therapeutic target.

The Rise of Bacterial G-Quadruplexes in Current Antimicrobial Discovery

Antimicrobial resistance (AMR) is a silent critical issue that poses several challenges to health systems. While the discovery of novel antibiotics is currently stalled and prevalently focused on chemical variations of the scaffolds of available drugs, novel targets and innovative strategies are urgently needed to face this global threat. In this context, bacterial G-quadruplexes (G4s) are emerging as timely and profitable targets for the design and development of antimicrobial agents. Indeed, they are expressed in regulatory regions of bacterial genomes, and their modulation has been observed to provide antimicrobial effects with translational perspectives in the context of AMR. In this work, we review the current knowledge of bacterial G4s as well as their modulation by small molecules, including tools and techniques suitable for these investigations. Finally, we critically analyze the needs and future directions in the field, with a focus on the development of small molecules as bacterial G4s modulators endowed with remarkable drug-likeness.

Identification of novel resistance-associated mutations and discrimination within whole-genome sequences of fluoroquinolone-resistant Mycobacterium tuberculosis isolates

This study aims to elucidate additional mutation loci associated with fluoroquinolone (FQ) resistance and evaluate the discriminatory capacity of mutation loci and allele mutation frequencies in identifying FQ-resistant Mycobacterium tuberculosis (MTB) isolates. A random selection of isolates was extracted from an ongoing collection. Drug resistance was determined using the resazurin microtiter assay (REMA) as the gold standard. Mutation loci and the burden of mutations in the quinolone resistance-determining region (QRDR) were elucidated through whole-genome sequencing (WGS). Novel amino acid mutations, namely, G520D and G520T, were identified in the gyrB and associated with FQ resistance. In the context of distinguishing FQ-resistant isolates, the AUC for the QRDR mutation frequency burden (0.969) surpassed that of the mutation locus (0.929), and this difference was statistically significant (P = 0.03). Furthermore, using the resistance mutation locus as a reference, setting the QRDR mutation frequency burden threshold at 1.31% resulted in a 3.60% increase in the accuracy of classifying FQ-resistant isolates (NRI = 3.60%, P < 0.001). The QRDR mutation frequency burden appears to offer superior diagnostic efficacy in discriminating FQ-resistant isolates compared to qualitative detection of mutant loci.IMPORTANCEFluoroquinolone (FQ) drugs are recommended as second-line drugs for the treatment of multidrug-resistant tuberculosis. With the massive use of FQ drugs in the clinical treatment of tuberculosis (TB), there is an increasing rate of drug resistance to FQ drugs. In this study, we identified and demonstrated novel amino acid mutations associated with FQ resistance in Mycobacterium tuberculosis (MTB), and we quantified the mutation sites and identified the quinolone resistance-determining region (QRDR) mutation frequency burden as a novel diagnostic method for FQ resistance. We hope that the results of this study will provide data support and a theoretical basis for the rapid diagnosis of FQ-resistant MTB.

Myeloid cell expression of CD200R is modulated in active TB disease and regulates Mycobacterium tuberculosis infection in a biomimetic model

A robust immune response is required for resistance to pulmonary tuberculosis (TB), the primary disease caused by Mycobacterium tuberculosis (Mtb). However, pharmaceutical inhibition of T cell immune checkpoint molecules can result in the rapid development of active disease in latently infected individuals, indicating the importance of T cell immune regulation. In this study, we investigated the potential role of CD200R during Mtb infection, a key immune checkpoint for myeloid cells. Expression of CD200R was consistently downregulated on CD14+ monocytes in the blood of subjects with active TB compared to healthy controls, suggesting potential modulation of this important anti-inflammatory pathway. In homogenized TB-diseased lung tissue, CD200R expression was highly variable on monocytes and CD11b+HLA-DR+ macrophages but tended to be lowest in the most diseased lung tissue sections. This observation was confirmed by fluorescent microscopy, which showed the expression of CD200R on CD68+ macrophages surrounding TB lung granuloma and found expression levels tended to be lower in macrophages closest to the granuloma core and inversely correlated with lesion size. Antibody blockade of CD200R in a biomimetic 3D granuloma-like tissue culture system led to significantly increased Mtb growth. In addition, Mtb infection in this system reduced gene expression of CD200R. These findings indicate that regulation of myeloid cells via CD200R is likely to play an important part in the immune response to TB and may represent a potential target for novel therapeutic intervention.

Exploring TSPAN4 promoter methylation as a diagnostic biomarker for tuberculosis

Background

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a persistent infectious disease threatening human health. The existing diagnostic methods still have significant shortcomings, including a low positivity rate in pathogen-based diagnoses and the inability of immunological diagnostics to detect active TB. Hence, it is urgent to develop new techniques to detect TB more accurate and earlier. This research aims to scrutinize and authenticate DNA methylation markers suitable for tuberculosis diagnosis. Concurrently, Providing a new approach for tuberculosis diagnosis.

Methods

Blood samples from patients with newly diagnosed tuberculosis and healthy controls (HC) were utilized in this study. Examining methylation microarray data from 40 whole blood samples (22TB + 18HC), we employed two procedures: signature gene methylated position analysis and signature region methylated position analysis to pinpoint distinctive methylated positions. Based on the screening results, diagnostic classifiers are constructed through machine learning, and validation was conducted through pyrosequencing in a separate queue (22TB + 18HC). Culminating in the development of a new tuberculosis diagnostic method via quantitative real-time methylation specific PCR (qMSP).

Results

The combination of the two procedures revealed a total of 10 methylated positions, all of which were located in the promoter region. These 10 signature methylated positions facilitated the construction of a diagnostic classifier, exhibiting robust diagnostic accuracy in both cross-validation and external test sets. The LDA model demonstrated the best classification performance, achieving an AUC of 0.83, specificity of 0.8, and sensitivity of 0.86 on the external test set. Furthermore, the validation of signature methylated positions through pyrosequencing demonstrated high agreement with screening outcomes. Additionally, qMSP detection of 2 potential hypomethylated positions (cg04552852 and cg12464638) exhibited promising results, yielding an AUC of 0.794, specificity of 0.720, and sensitivity of 0.816.

Conclusion

Our study demonstrates that the validated signature methylated positions through pyrosequencing emerge as plausible biomarkers for tuberculosis diagnosis. The specific methylation markers in the TSPAN4 gene, identified in whole blood samples, hold promise for improving tuberculosis diagnosis. This approach could significantly enhance diagnostic accuracy and speed, offering a new avenue for early detection and treatment.

Important role of DNA methylation hints at significant potential in tuberculosis

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb) infection, has persisted as a major global public health threat for millennia. Until now, TB continues to challenge efforts aimed at controlling it, with drug resistance and latent infections being the two main factors hindering treatment efficacy. The scientific community is still striving to understand the underlying mechanisms behind Mtb's drug resistance and latent infection. DNA methylation, a critical epigenetic modification occurring throughout an individual's growth and development, has gained attention following advances in high-throughput sequencing technologies. Researchers have observed abnormal DNA methylation patterns in the host genome during Mtb infection. Given the escalating issue of drug-resistant Mtb, delving into the role of DNA methylation in TB's development is crucial. This review article explores DNA methylation's significance in human growth, development and disease, and its role in regulating Mtb's evolution and infection processes. Additionally, it discusses potential applications of DNA methylation research in tuberculosis.

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.

Mycobacterial Rv1804c binds to the PEST domain of IκBα and activates macrophage-mediated proinflammatory responses

Recognition of the components of Mycobacterium tuberculosis (Mtb) by macrophages is vital for initiating a cascade of host immune responses. However, the recognition of Mtb-secretory proteins by the receptor-independent pathways of the host remains unclear. Rv1804c is a highly conserved secretory protein in Mtb. However, its exact function and underlying mechanism in Mtb infection remain poorly understood. In the present study, we observed that Rv1804c activates macrophage-mediated proinflammatory responses in an IKKα-independent manner. Furthermore, we noted that Rv1804c inhibits mycobacterial survival. By elucidating the underlying mechanisms, we observed that Rv1804c activates IκBα by directly interacting with its PEST domain. Moreover, Rv1804c was enriched in attenuated but not in virulent mycobacteria and associated with the disease process of tuberculosis. Our findings provide an alternative pathway via which a mycobacterial secretory protein activates macrophage-mediated proinflammatory responses. Our study findings may shed light on the prevention and treatment of tuberculosis.

Myc Dysregulation in Activated Macrophages Initiates Iron-Mediated Lipid Peroxidation that Fuels Type I Interferon and Compromises TB Resistance

A quarter of human population is infected with Mycobacterium tuberculosis, but less than 10% of those infected develop clinical, mostly pulmonary, TB. To dissect mechanisms of susceptibility in immunocompetent individuals, we developed a genetically defined sst1-susceptible mouse model that uniquely reproduces a defining feature of human TB: development of necrotic lung lesions after infection with virulent Mtb. In this study, we explored the connectivity of the sst1-regulated pathways during prolonged macrophage activation with TNF. We determined that the aberrant response of the sst1-susceptible macrophages to TNF was primarily driven by conflicting Myc and antioxidant response pathways that resulted in a coordinated failure to properly sequester intracellular iron and activate ferroptosis inhibitor enzymes. Consequently, iron-mediated lipid peroxidation fueled IFNβ superinduction and sustained the Type I Interferon (IFN-I) pathway hyperactivity that locked the sst1-susceptible macrophages in a state of unresolving stress and compromised their resistance to Mtb. The accumulation of the aberrantly activated, stressed, macrophages within granuloma microenvironment led to the local failure of anti-tuberculosis immunity and tissue necrosis. Our findings suggest a novel link between metabolic dysregulation in macrophages and susceptibility to TB, offering insights into potential therapeutic targets aimed at modulating macrophage function and improving TB control.

Mathematical modeling suggests heterogeneous replication of Mycobacterium tuberculosis in rabbits

Tuberculosis (TB), the disease caused by Mycobacterium tuberculosis (Mtb), remains a major health problem with 10.6 million cases of the disease and 1.6 million deaths in 2021. It is well understood that pulmonary TB is due to replication of Mtb in the lung but quantitative details of Mtb replication and death in lungs of patients and how these rates are related to the degree of lung pathology are unknown. We performed experiments with rabbits infected with a novel, virulent clinical Mtb isolate of the Beijing lineage, HN878, carrying an unstable plasmid pBP10. In our in vitro experiments we found that pBP10 is more stable in HN878 strain than in a more commonly used laboratory-adapted Mtb strain H37Rv (the segregation coefficient being s = 0 . 10 in HN878 vs. s = 0 . 18 in H37Rv). Interestingly, the kinetics of plasmid-bearing bacteria in lungs of Mtb-infected rabbits did not follow an expected monotonic decline; the percent of plasmid-bearing cells increased between 28 and 56 days post-infection and remained stable between 84 and 112 days post-infection despite a large increase in bacterial numbers in the lung at late time points. Mathematical modeling suggested that such a non-monotonic change in the percent of plasmid-bearing cells can be explained if the lung Mtb population consists of several (at least 2) sub-populations with different replication/death kinetics: one major population expanding early and being controlled/eliminated, while another, a smaller population expanding at later times causing a counterintuitive increase in the percent of plasmid-bearing cells. Given that HN878 forms well circumscribed granulomas in rabbits, our results suggest independent bacterial dynamics in subsets of such granulomas. Our model predictions can be tested in future experiments in which HN878-pBP10 dynamics in individual granulomas is followed over time.

Immunopathology of Pulmonary Mycobacterium tuberculosis Infection in a Humanized Mouse Model

Despite the availability of antibiotic therapy, tuberculosis (TB) is prevailing as a leading killer among human infectious diseases, which highlights the need for better intervention strategies to control TB. Several animal model systems, including mice, guinea pigs, rabbits, and non-human primates have been developed and explored to understand TB pathogenesis. Although each of these models contributes to our current understanding of host-Mycobacterium tuberculosis (Mtb) interactions, none of these models fully recapitulate the pathological spectrum of clinical TB seen in human patients. Recently, humanized mouse models are being developed to improvise the limitations associated with the standard mouse model of TB, including lack of necrotic caseation of granulomas, a pathological hallmark of TB in humans. However, the spatial immunopathology of pulmonary TB in humanized mice is not fully understood. In this study, using a novel humanized mouse model, we evaluated the spatial immunopathology of pulmonary Mtb infection with a low-dose inoculum. Humanized NOD/LtSscidIL2Rγ null mice containing human fetal liver, thymus, and hematopoietic CD34+ cells and treated with human cytokines were aerosol challenged to implant <50 pathogenic Mtb (low dose) in the lungs. At 2 and 4 weeks post infection, the tissue bacterial load, disease pathology, and spatial immunohistology were determined in the lungs, liver, spleen, and adipose tissue using bacteriological, histopathological, and immunohistochemical techniques. The results indicate that implantation of <50 bacteria can establish a progressive disease in the lungs that transmits to other tissues over time. The disease pathology in organs correspondingly increased with the bacterial load. A distinct spatial distribution of T cells, macrophages, and natural killer cells were noted in the lung granulomas. The kinetics of spatial immune cell distribution were consistent with the disease pathology in the lungs. Thus, the novel humanized model recapitulates several key features of human pulmonary TB granulomatous response and can be a useful preclinical tool to evaluate potential anti-TB drugs and vaccines.

Host-directed therapy against mycobacterium tuberculosis infections with diabetes mellitus

Tuberculosis (TB) is caused by the bacterial pathogen Mycobacterium tuberculosis (MTB) and is one of the principal reasons for mortality and morbidity worldwide. Currently, recommended anti-tuberculosis drugs include isoniazid, rifampicin, ethambutol, and pyrazinamide. TB treatment is lengthy and inflicted with severe side-effects, including reduced patient compliance with treatment and promotion of drug-resistant strains. TB is also prone to other concomitant diseases such as diabetes and HIV. These drug-resistant and complex co-morbid characteristics increase the complexity of treating MTB. Host-directed therapy (HDT), which effectively eliminates MTB and minimizes inflammatory tissue damage, primarily by targeting the immune system, is currently an attractive complementary approach. The drugs used for HDT are repositioned drugs in actual clinical practice with relative safety and efficacy assurance. HDT is a potentially effective therapeutic intervention for the treatment of MTB and diabetic MTB, and can compensate for the shortcomings of current TB therapies, including the reduction of drug resistance and modulation of immune response. Here, we summarize the state-of-the-art roles and mechanisms of HDT in immune modulation and treatment of MTB, with a special focus on the role of HDT in diabetic MTB, to emphasize the potential of HDT in controlling MTB infection.

CD4+ T cells are homeostatic regulators during Mtb reinfection

Immunological priming - either in the context of prior infection or vaccination - elicits protective responses against subsequent Mycobacterium tuberculosis (Mtb) infection. However, the changes that occur in the lung cellular milieu post-primary Mtb infection and their contributions to protection upon reinfection remain poorly understood. Here, using clinical and microbiological endpoints in a non-human primate reinfection model, we demonstrate that prior Mtb infection elicits a long-lasting protective response against subsequent Mtb exposure and that the depletion of CD4+ T cells prior to Mtb rechallenge significantly abrogates this protection. Leveraging microbiologic, PET-CT, flow cytometric, and single-cell RNA-seq data from primary infection, reinfection, and reinfection-CD4+ T cell depleted granulomas, we identify differential cellular and microbial features of control. The data collectively demonstrate that the presence of CD4+ T cells in the setting of reinfection results in a reduced inflammatory lung milieu characterized by reprogrammed CD8+ T cell activity, reduced neutrophilia, and blunted type-1 immune signaling among myeloid cells, mitigating Mtb disease severity. These results open avenues for developing vaccines and therapeutics that not only target CD4+ and CD8+ T cells, but also modulate innate immune cells to limit Mtb disease.

Pathogenicity and virulence of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, an infectious disease with one of the highest morbidity and mortality rates worldwide. Leveraging its highly evolved repertoire of non-protein and protein virulence factors, Mtb invades through the airway, subverts host immunity, establishes its survival niche, and ultimately escapes in the setting of active disease to initiate another round of infection in a naive host. In this review, we will provide a concise synopsis of the infectious life cycle of Mtb and its clinical and epidemiologic significance. We will also take stock of its virulence factors and pathogenic mechanisms that modulate host immunity and facilitate its spread. Developing a greater understanding of the interface between Mtb virulence factors and host defences will enable progress toward improved vaccines and therapeutics to prevent and treat tuberculosis.

Vaccine development against tuberculosis before and after Covid-19

Coronavirus disease (Covid-19) has not only shaped awareness of the impact of infectious diseases on global health. It has also provided instructive lessons for better prevention strategies against new and current infectious diseases of major importance. Tuberculosis (TB) is a major current health threat caused by Mycobacterium tuberculosis (Mtb) which has claimed more lives than any other pathogen over the last few centuries. Hence, better intervention measures, notably novel vaccines, are urgently needed to accomplish the goal of the World Health Organization to end TB by 2030. This article describes how the research and development of TB vaccines can benefit from recent developments in the Covid-19 vaccine pipeline from research to clinical development and outlines how the field of TB research can pursue its own approaches. It begins with a brief discussion of major vaccine platforms in general terms followed by a short description of the most widely applied Covid-19 vaccines. Next, different vaccination regimes and particular hurdles for TB vaccine research and development are described. This specifically considers the complex immune mechanisms underlying protection and pathology in TB which involve innate as well as acquired immune mechanisms and strongly depend on fine tuning the response. A brief description of the TB vaccine candidates that have entered clinical trials follows. Finally, it discusses how experiences from Covid-19 vaccine research, development, and rollout can and have been applied to the TB vaccine pipeline, emphasizing similarities and dissimilarities.

An Oxygen Supply Strategy for Sonodynamic Therapy in Tuberculous Granuloma Lesions Using a Catalase-Loaded Nanoplatform

Purpose

Tuberculosis (TB) is a chronic disease caused by Mycobacterium tuberculosis (MTB) that remains a major global health challenge. One of the main obstacles to effective treatment is the heterogeneous microenvironment of TB granulomas. This study aimed to investigate the potential of a hypoxic remission-based strategy to enhance the outcome of tuberculosis treatment when implemented in combination with ultrasound.

Methods

A PLGA nanoparticle (LEV@CAT-NPs) loaded with levofloxacin (LEV) and catalase (CAT) was fabricated by a double emulsification method, and its physical characteristics, oxygen production capacity, drug release capacity, and biosafety were thoroughly investigated. The synergistic therapeutic effects of ultrasound (US)-mediated LEV@CAT-NPs were evaluated using an experimental mouse model of subcutaneous tuberculosis granuloma induced by Bacille Calmette-Guérin (BCG) as a substitute for MTB.

Results

LEV@CAT-NPs exhibited excellent oxygen production capacity, biosafety, and biocompatibility. Histological analysis revealed that ultrasound-mediated LEV@CAT-NPs could effectively remove bacteria from tuberculous granulomas, significantly alleviate the hypoxia state, reduce the necrotic area and inflammatory cells within the granuloma, and increase the penetration of dyes in granuloma tissues. The combined treatment also reduced the serum levels of inflammatory cytokines (eg, TNF-α, IL-6, and IL-8), and significantly downregulated the expression of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF). These results suggested that the synergistic treatment of ultrasound-mediated LEV@CAT-NPs effectively eradicated the bacterial infection and reversed the hypoxic microenvironment of tuberculous granulomas, further promoting tissue repair.

Conclusion

This study provides a non-invasive and new avenue for treating refractory tuberculosis infections. The potential role of regulating hypoxia within infected lesions as a therapeutic target for infection deserves further exploration in future studies.

Immunosuppression is a conserved driver of tuberculosis susceptibility

Mycobacterium tuberculosis ( Mtb ) causes 1.6 million deaths a year 1 . However, no individual mouse model fully recapitulates the hallmarks of human tuberculosis disease. Here we report that a comparison across three different susceptible mouse models identifies Mtb -induced gene signatures that predict active TB disease in humans significantly better than a signature from the standard C57BL/6 mouse model. An increase in lung myeloid cells, including neutrophils, was conserved across the susceptible mouse models, mimicking the neutrophilic inflammation observed in humans 2,3 . Myeloid cells in the susceptible models and non-human primates exhibited high expression of immunosuppressive molecules including the IL-1 receptor antagonist, which inhibits IL-1 signaling. Prior reports have suggested that excessive IL-1 signaling impairs Mtb control 4-6 . By contrast, we found that enhancement of IL-1 signaling via deletion of IL-1 receptor antagonist promoted bacterial control in all three susceptible mouse models. IL-1 signaling enhanced cytokine production by lymphoid and stromal cells, suggesting a mechanism for IL-1 signaling in promoting Mtb control. Thus, we propose that myeloid cell expression of immunosuppressive molecules is a conserved mechanism exacerbating Mtb disease in mice, non-human primates, and humans.

Key advances in vaccine development for tuberculosis-success and challenges

Breakthrough findings in the clinical and preclinical development of tuberculosis (TB) vaccines have galvanized the field and suggest, for the first time since the development of bacille Calmette-Guérin (BCG), that a novel and protective TB vaccine is on the horizon. Here we highlight the TB vaccines that are in the development pipeline and review the basis for optimism in both the clinical and preclinical space. We describe immune signatures that could act as immunological correlates of protection (CoP) to facilitate the development and comparison of vaccines. Finally, we discuss new animal models that are expected to more faithfully model the pathology and complex immune responses observed in human populations.

Turning foes into permissive hosts: manipulation of macrophage polarization by intracellular bacteria

Macrophages function as tissue-immune sentinels and mediate key antimicrobial responses against bacterial pathogens. Yet, they can also act as a cellular niche for intracellular bacteria, such as Salmonella enterica, to persist in infected tissues. Macrophages exhibit heterogeneous activation or polarization, states that are linked to differential antibacterial responses and bacteria permissiveness. Remarkably, recent studies demonstrate that Salmonella and other intracellular bacteria inject virulence effectors into the cellular cytoplasm to skew the macrophage polarization state and reprogram these immune cells into a permissive niche. Here, we review mechanisms of macrophage reprogramming by Salmonella and highlight manipulation of macrophage polarization as a shared bacterial pathogenesis strategy. In addition, we discuss how the interplay of bacterial effector mechanisms, microenvironmental signals, and ontogeny may shape macrophage cell states and functions. Finally, we propose ideas of how further research will advance our understanding of macrophage functional diversity and immunobiology.

Mycobacterium tuberculosis and its clever approaches to escape the deadly macrophage

Mycobacterium tuberculosis (Mt.b), a deadly disease causer, is a facultative parasite. This microorganism has developed several methods to defend itself, once internalized within specialised vacuoles in the macrophages. A wide array of receptors like the complement receptor mannose receptors, scavenger receptor assists the entry of the microbe within the phagocytic macrophages. However, Mt.b is clever enough to protect itself from the hostile environment of the macrophage thereby prevailing within it. The microbe can efficiently inhibit processes like phagosome-lysosome fusion, acidification of phagosomes, release of proinflammatory cytokines and stop crucial events like apoptosis. Additionally, it also adopts resistance to killing by reactive oxygen intermediates and reactive nitrogen intermediates. There are multiple genes both in host and the pathogen which are involved in this successful survival of Mt.b. The regulation of phagolysosome fusion is mediated by proteins such as Coronin, TlyA, SapM, PnkG, EsxH. The microbe has certain mechanisms to even acquire iron from the host cell, to withstand iron deprivation as a mode of host's defence mechanism. This review focuses on the various defensive adaptations acquired by Mt.b for fighting against the deprived conditions existing within the macrophages and their capability of proliferating successfully within it, thereby resulting in a diseased condition.

A half-century of research on tuberculosis: Successes and challenges

Great progress has been made over the past half-century, but TB remains a formidable global health problem, particularly in low- and middle-income countries. Understanding the mechanisms of pathogenesis and necessary and sufficient conditions for protection are critical. The need for inexpensive and sensitive point-of-care diagnostic tests for earlier detection of infection and disease, shorter and less-toxic drug regimens for drug-sensitive and -resistant TB, and a more effective vaccine than BCG is immense. New and better tools, greater support for international research, collaborations, and training will be required to dramatically reduce the burden of this devastating disease which still kills 1.6 million people annually.

The Many Hosts of Mycobacteria 9 (MHM9): A conference report

The Many Hosts of Mycobacteria (MHM) meeting series brings together basic scientists, clinicians and veterinarians to promote robust discussion and dissemination of recent advances in our knowledge of numerous mycobacterial diseases, including human and bovine tuberculosis (TB), nontuberculous mycobacteria (NTM) infection, Hansen's disease (leprosy), Buruli ulcer and Johne's disease. The 9th MHM conference (MHM9) was held in July 2022 at The Ohio State University (OSU) and centered around the theme of "Confounders of Mycobacterial Disease." Confounders can and often do drive the transmission of mycobacterial diseases, as well as impact surveillance and treatment outcomes. Various confounders were presented and discussed at MHM9 including those that originate from the host (comorbidities and coinfections) as well as those arising from the environment (e.g., zoonotic exposures), economic inequality (e.g. healthcare disparities), stigma (a confounder of leprosy and TB for millennia), and historical neglect (a confounder in Native American Nations). This conference report summarizes select talks given at MHM9 highlighting recent research advances, as well as talks regarding the historic and ongoing impact of TB and other infectious diseases on Native American Nations, including those in Southwestern Alaska where the regional TB incidence rate is among the highest in the Western hemisphere.

Mechanisms of lung damage in tuberculosis: implications for chronic obstructive pulmonary disease

Pulmonary tuberculosis is increasingly recognized as a risk factor for COPD. Severe lung function impairment has been reported in post-TB patients. Despite increasing evidence to support the association between TB and COPD, only a few studies describe the immunological basis of COPD among TB patients following successful treatment completion. In this review, we draw on well-elaborated Mycobacterium tuberculosis-induced immune mechanisms in the lungs to highlight shared mechanisms for COPD pathogenesis in the setting of tuberculosis disease. We further examine how such mechanisms could be exploited to guide COPD therapeutics.

Spatial mapping reveals granuloma diversity and histopathological superstructure in human tuberculosis

The hallmark of tuberculosis (TB) is the formation of immune cell-enriched aggregates called granulomas. While granulomas are pathologically diverse, their tissue-wide heterogeneity has not been spatially resolved at the single-cell level in human tissues. By spatially mapping individual immune cells in every lesion across entire tissue sections, we report that in addition to necrotizing granulomas, the human TB lung contains abundant non-necrotizing leukocyte aggregates surrounding areas of necrotizing tissue. These cellular lesions were more diverse in composition than necrotizing lesions and could be stratified into four general classes based on cellular composition and spatial distribution of B cells and macrophages. The cellular composition of non-necrotizing structures also correlates with their proximity to necrotizing lesions, indicating these are foci of distinct immune reactions adjacent to necrotizing granulomas. Together, we show that during TB, diseased lung tissue develops a histopathological superstructure comprising at least four different types of non-necrotizing cellular aggregates organized as satellites of necrotizing granulomas.

A nomogram for predicting mortality of patients initially diagnosed with primary pulmonary tuberculosis in Hunan province, China: a retrospective study

Objective

According to the Global Tuberculosis Report for three consecutive years, tuberculosis (TB) is the second leading infectious killer. Primary pulmonary tuberculosis (PTB) leads to the highest mortality among TB diseases. Regretfully, no previous studies targeted the PTB of a specific type or in a specific course, so models established in previous studies cannot be accurately feasible for clinical treatments. This study aimed to construct a nomogram prognostic model to quickly recognize death-related risk factors in patients initially diagnosed with PTB to intervene and treat high-risk patients as early as possible in the clinic to reduce mortality.

Methods

We retrospectively analyzed the clinical data of 1,809 in-hospital patients initially diagnosed with primary PTB at Hunan Chest Hospital from January 1, 2019, to December 31, 2019. Binary logistic regression analysis was used to identify the risk factors. A nomogram prognostic model for mortality prediction was constructed using R software and was validated using a validation set.

Results

Univariate and multivariate logistic regression analyses revealed that drinking, hepatitis B virus (HBV), body mass index (BMI), age, albumin (ALB), and hemoglobin (Hb) were six independent predictors of death in in-hospital patients initially diagnosed with primary PTB. Based on these predictors, a nomogram prognostic model was established with high prediction accuracy, of which the area under the curve (AUC) was 0.881 (95% confidence interval [Cl]: 0.777-0.847), the sensitivity was 84.7%, and the specificity was 77.7%.Internal and external validations confirmed that the constructed model fit the real situation well.

Conclusion

The constructed nomogram prognostic model can recognize risk factors and accurately predict the mortality of patients initially diagnosed with primary PTB. This is expected to guide early clinical intervention and treatment for high-risk patients.

Circular RNA circTRAPPC6B Enhances IL-6 and IL-1β Expression and Repolarizes Mycobacteria Induced Macrophages from M2- to M1-Like Phenotype by Targeting miR-892c-3p

Mycobacterium tuberculosis (Mtb) infection elicits macrophage polarization into M2 phenotype to block the host's protective immune response. However, it remains unclear how Mtb regulates macrophage polarization. Recent studies have suggested that noncoding RNA may play a role in macrophage polarization. In this study, we investigated the potential involvement of circTRAPPC6B, a circular RNA that is downregulated in tuberculosis (TB) patients, in regulating macrophage polarization. We found that Mtb infection downregulated M1-related IL-6 and IL-1β while highly expressed M2-related CCL22 and CD163. Overexpressed circTRAPPC6B had switched Mtb-infected macrophages from M2- to M1-like phenotype, accompanied by upregulation of IL-6 and IL-1β. Meanwhile overexpressed circTRAPPC6B significantly inhibited Mtb growth in macrophages. Our findings suggest that circTRAPPC6B may regulate macrophage polarization by targeting miR-892c-3p, which is highly expressed in TB patients and M2-like macrophages. And miR-892c-3p inhibitor decreased intracellular Mtb growth in macrophages. Thus, TB-inhibited circTRAPPC6B could specifically induce IL-6 and IL-1β expression to switch/antagonize Mtb-induced macrophage polarization from M2- to M1-like phenotype by targeting miR-892c-3p, leading to enhanced host clearance of Mtb. Our results reveal a potential role for circTRAPPC6B in regulating macrophage polarization during Mtb infection and provide new insights into the molecular mechanisms underlying host defense against Mtb.

Immune cell interactions in tuberculosis

Despite having been identified as the organism that causes tuberculosis in 1882, Mycobacterium tuberculosis has managed to still evade our understanding of the protective immune response against it, defying the development of an effective vaccine. Technology and novel experimental models have revealed much new knowledge, particularly with respect to the heterogeneity of the bacillus and the host response. This review focuses on certain immunological elements that have recently yielded exciting data and highlights the importance of taking a holistic approach to understanding the interaction of M. tuberculosis with the many host cells that contribute to the development of protective immunity.

Characteristics of alveolar macrophages in bronchioalveolar lavage fluids from active tuberculosis patients identified by single-cell RNA sequencing

Tuberculosis (TB), is an infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), and presents with high morbidity and mortality. Alveolar macrophages play an important role in TB pathogenesis although there is heterogeneity and functional plasticity. This study aimed to show the characteristics of alveolar macrophages from bronchioalveolar lavage fluid (BALF) in active TB patients. Single-cell RNA sequencing (scRNA-seq) was performed on BALF cells from three patients with active TB and additional scRNA-seq data from three healthy adults were established as controls. Transcriptional profiles were analyzed and compared by differential geneexpression and functional enrichment analysis. We applied pseudo-temporal trajectory analysis to investigate correlations and heterogeneity within alveolar macrophage subclusters. Alveolar macrophages from active TB patients at the single-cell resolution are described. We found that TB patients have higher cellular percentages in five macrophage subclusters. Alveolar macrophage subclusters with increased percentages were involved in inflammatory signaling pathways as well as the basic macrophage functions. The TB-increased alveolar macrophage subclusters might be derived from M1-like polarization state, before switching to an M2-like polarization state with the development ofM. tuberculosis infection. Cell-cell communications of alveolar macrophages also increased and enhanced in active TB patients. Overall, our study demonstrated the characteristics of alveolar macrophages from BALF in active TB patients by using scRNA-seq.