In the Thick of It: Formation of the Tuberculous Granuloma and Its Effects on Host and Therapeutic Responses

Unraveling the role of the immune landscape in tuberculosis granuloma

Despite significant advances in research over the past century, Tuberculosis (TB) remains a formidable global health concern. TB granulomas are organized structures composed of immune cells, that serve as the body's primary defense against the spread of Mycobacterium tuberculosis (Mtb). The immune landscape of TB granulomas involves a complex array of immune cells, including CD4+ and CD8+ T cells, B cells, NK cells, and others, which collectively influence the fate of the granuloma. B cells contribute to the formation of the granuloma's germinal center, while the functional state of T cells-particularly their ability to control infection-dictates whether the granuloma is controlling or proliferative. The intricate interplay between T cells and the dynamic microenvironment of the granuloma plays a pivotal role in determining the outcome of the infection. However, several aspects of the immunological basis of tuberculosis are still unknown. This review delves into the immunological landscape of TB granuloma, focusing on the dynamic cellular interplay within the granuloma and its profound influence on disease pathogenesis.

Mycobacterium marinum as a model for understanding principles of mycobacterial pathogenesis

Mycobacterium marinum is a fish pathogen that has become a powerful and well-established model that has accelerated our understanding of the mechanisms of mycobacterial disease. M. marinum is a versatile surrogate for understanding the closely related human pathogen M. tuberculosis, which causes tuberculosis in humans. M. marinum has defined key mechanisms of pathogenesis, both shared with M. tuberculosis and unique to this species. In this review, we discuss the discovery of M. marinum as an occasional human pathogen, the shared aspects of pathogenesis with M. tuberculosis, and how M. marinum has been exploited as a model to define the molecular mechanisms of mycobacterial pathogenesis across several phases of infection.

Unraveling persistent bacteria: Formation, niches, and eradication strategies

Persistent bacteria (persisters) are phenotypic variants that emerge either randomly or in response to a range of adverse environmental conditions. Persistence represents a state whereby a subpopulation of microorganisms can spontaneously enter a "dormant" state in response to environmental factors, while simultaneously exhibiting elevated tolerance to antimicrobial agents. This review provides the current definition of bacterial persistence and summarizes the mechanisms of persisters formation as well as the various niches of bacterial persistence encountered in clinical practice. Strategies targeting persisters are outlined, including but not limited to direct killing, awakening of persistent bacteria, combined clearance, and inhibition of persistence formation, and we conclude by proposing challenges and solutions for addressing bacterial persistence in current clinical practice.

Long non-coding RNA transcripts in Mycobacterium tuberculosis-host interactions

Tuberculosis (TB) persists as a significant health threat, affecting millions of people all over the world. Despite years of control measures, the elimination of TB has become a difficult task as morbidity and mortality rates remain unaffected for several years. Developing new diagnostics and therapeutics is paramount to keeping TB under control. However, it largely depends upon understanding the pathogenic mechanisms of Mycobacterium tuberculosis (Mtb), the causative agent of TB. Mtb is an intracellular pathogen capable of subverting the defensive functions of the immune cells, and it can survive and multiply within humans' mononuclear phagocytes. Emerging evidence indicates that long non-coding RNAs (lncRNAs), a class of RNA molecules with limited coding potential, are critical players in this intricate game as they regulate gene expression at transcriptional and post-transcriptional levels and also by chromatin modification. Moreover, they have been shown to regulate cellular processes by controlling the function of other molecules, such as DNA, RNA, and protein, through binding with them. Recent studies have shown that lncRNAs are differentially regulated in the tissues of TB patients and cells infected in vitro with Mtb. Some dysregulated lncRNAs are associated with essential roles in modulating immune response, apoptosis, and autophagy in the host cells, adding a new dimension to TB pathogenesis. In this article, we provide a comprehensive review of the recent literature in this field and the impact of lncRNAs in unraveling pathogenic mechanisms in TB. We also discuss how the studies involving lncRNAs provide insight into TB pathogenesis, especially Mtb-host interactions.

Cathepsin Z is a conserved susceptibility factor underlying tuberculosis severity

Tuberculosis (TB) outcomes vary widely, from asymptomatic infection to mortality, yet most animal models do not recapitulate human phenotypic and genotypic variation. The genetically diverse Collaborative Cross mouse panel models distinct facets of TB disease that occur in humans and allows identification of genomic loci underlying clinical outcomes. We previously mapped a TB susceptibility locus on mouse chromosome 2. Here, we identify cathepsin Z ( Ctsz ) as a lead candidate underlying this TB susceptibility and show that Ctsz ablation leads to increased bacterial burden, CXCL1 overproduction, and decreased survival in mice. Ctsz disturbance within murine macrophages enhances production of CXCL1, a known biomarker of TB severity. From a Ugandan household contact study, we identify significant associations between CTSZ variants and TB disease severity. Finally, we examine patient-derived TB granulomas and report CTSZ localization within granuloma-associated macrophages, placing human CTSZ at the host-pathogen interface. These findings implicate a conserved CTSZ-CXCL1 axis in humans and genetically diverse mice that mediates TB disease severity.

Multi-omic latent variable data integration reveals multicellular structure pathways associated with resistance to tuberculin skin test (TST)/interferon gamma release assay (IGRA) conversion in Uganda

Understanding the mechanisms of early clearance of Mycobacterium tuberculosis (Mtb) may illuminate new therapeutic strategies for tuberculosis (TB). We previously found genetic, epigenetic, and transcriptomic signatures associated with resistance (resister, RSTR) to tuberculin skin test (TST)/interferon gamma release assay (IGRA) conversion among highly exposed TB contacts. We hypothesized that integration of these datasets with multi-omic latent factor methods would detect pathways differentiating RSTR patients from those with asymptomatic TB infection (TBI, also known as latent TB infection or LTBI) that were not detected in individual dataset analyses. We pre-filtered and scaled features with the largest change between TBI and RSTR groups for 126 patients with data in at least two of five data modalities: single nucleotide polymorphisms (SNP), monocyte RNAseq (baseline and Mtb-stimulated conditions), and monocyte epigenetics (methylation and ATAC-seq). Using multiomic latent factor analysis (MOFA), we generated ten latent factors on the subset of 33 patients with all five datasets available, four of which differed by RSTR status (FDR < 0.1). Factor 4 showed the greatest difference between RSTR and TBI groups (FDR < 0.001). Three additional latent factor integration methods also distinguished the RSTR and TBI groups and identified overlapping features with MOFA. Using pathway analysis and a cluster-based enrichment method, we identified functions associated with latent factors and found that MOFA Factors 2-4 include functions related to cell-cell adhesion, cell shape, and multicellular structure development. In summary, latent variable integration methods uncovered signatures associated with resistance to TST/IGRA conversion that were not detected by individual dataset analyses and included pathways associated with cellular interactions and multicellular structures.

Timing matters in macrophage/CD4+ T cell interactions: an agent-based model comparing Mycobacterium tuberculosis host-pathogen interactions between latently infected and naïve individuals

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a significant health challenge. Clinical manifestations of TB exist across a spectrum with a majority of infected individuals remaining asymptomatic, commonly referred to as latent TB infection (LTBI). In vitro models have demonstrated that cells from individuals with LTBI can better control Mtb growth and form granuloma-like structures more quickly, compared to cells from uninfected (Mtb-naïve) individuals. These in vitro results agree with animal and clinical evidence that LTBI protects, to some degree, against reinfection. However, the mechanisms by which LTBI might offer protection against reinfection remain unclear, and quantifying the relative contributions of multiple control mechanisms is challenging using experimental methods alone. To complement in vitro models, we have developed an in silico agent-based model to help elucidate host responses that might contribute to protection against reinfection. Our simulations indicate that earlier contact between macrophages and CD4+ T cells leads to LTBI simulations having more activated CD4+ T cells and, in turn, more activated infected macrophages, all of which contribute to a decreased bacterial load early on. Our simulations also demonstrate that granuloma-like structures support this early macrophage activation in LTBI simulations. We find that differences between LTBI and Mtb-naïve simulations are driven by TNFα and IFNγ-associated mechanisms as well as macrophage phagocytosis and killing mechanisms. Together, our simulations show how important the timing of the first interactions between innate and adaptive immune cells is, how this impacts infection progression, and why cells from LTBI individuals might be faster to respond to reinfection.IMPORTANCETuberculosis (TB) remains a significant global health challenge, with millions of new infections and deaths annually. Despite extensive research, the mechanisms by which latent TB infection (LTBI) confers protection against reinfection remain unclear. In this study, we developed an in silico agent-based model to simulate early immune responses to Mycobacterium tuberculosis infection based on experimental in vitro infection of human donor cells. Our simulations reveal that early interactions between macrophages and CD4+ T cells, driven by TNFα and IFNγ, are critical for bacterial control and granuloma formation in LTBI. These findings offer new insights into the immune processes involved in TB, which could inform the development of targeted vaccines and host-directed therapies. By integrating experimental data with computational predictions, our research provides a robust framework for understanding TB immunity and guiding future interventions to mitigate the global TB burden.

The role of neutrophil response in lung damage and post-tuberculosis lung disease: a translational narrative review

It is estimated that more than 150 million individuals alive in 2020 had survived tuberculosis (TB). A portion of this large population continues to experience chronic respiratory abnormalities, with or without symptoms, due to previous active pulmonary TB. This condition known as Post-TB Lung Disease (PTLD), involves a complex interaction between pathogen, host and environmental factors. These interactions are believed to drive a hyperinflammatory process in the lungs during active TB, resulting in tissue damage, which may lead to radiological sequelae, impaired pulmonary function, clinical symptoms, such as cough, dyspnea, hemoptysis, and respiratory infections. Such complications impose significant health, financial, and social burdens, which remain poorly understood and inadequately addressed by health care systems. Given the heterogeneity of immune cells and their products infiltrating the airways and the lung parenchyma during acute and chronic inflammation caused by Mycobacterium tuberculosis infection, it is evident that TB immunopathology is multifactorial. Among the various components involved, neutrophils have recently emerged as critical contributors to the deleterious immune response against TB, leading to severe pulmonary damage. In this translational narrative review, we aim to summarize the role of neutrophils and their primary products - proteases (such as elastase), matrix metalloproteinases and neutrophils extracellular traps (NETs) - in pulmonary TB. We highlight new concepts and emerging evidence of neutrophil involvement during the active disease, translating these insights from "bench to bedside" to facilitate dialogue between fundamental researchers and clinical practitioners. Additionally, we present potential targets for future treatment strategies that could mitigate or even prevent PTLD.

Differential expression of vascular endothelial growth factor A (VEGFA) and M1 macrophage marker nitric oxide synthase 2 (NOS2) in lymph node granulomas of BCG-vaccinated and non-vaccinated cattle infected with Mycobacterium bovis

Bovine tuberculosis is mainly caused by Mycobacterium bovis. Bacillus Calmette-Guérin (BCG) is an attenuated strain of M. bovis which provides variable disease protection. Lesions have been characterized in infected cattle, but little comparison has been done with lesions which form in BCG-vaccinates. Here, in situ hybridization examined differences in expression of M. bovis RNA, inducible nitric oxide synthase 2, and vascular endothelial growth factor A in relation to vaccination status and granuloma grade, using two different groups of cattle. Data found no differences between vaccination groups or granuloma grade in average copies of M. bovis mRNA per μm2 of total granuloma area or per μm2 of necrotic areas. Within a vaccination group high-grade granulomas had more NOS2 per cell, per μm2 and a higher percentage of cells expressing NOS2 than low-grade granulomas. Non-vaccinates had a higher percentage of cells producing NOS2 than vaccinates. Differences in NOS2 expression varied by group. Vaccination status and granuloma grade did not affect the average copies of VEGFA per cell or the percent of cells expressing RNA, however VEGFA copies per μm2 varied between groups. These findings suggest NOS2 and VEGFA are likely not mechanisms of BCG vaccination protection but may impact disease severity.

lafK contributes the regulation of swarming motility of Pseudomonas plecoglossicida and bacterial-host interaction

Flagella-mediated swarming motility plays a crucial role in facilitating the rapid colonization and dissemination of bacterial within the host. The swarming motility of Pseudomonas plecoglossicida is intricately associated with its lateral flagella, and notably, the lateral flagella system of P. plecoglossicida encompasses a transcriptional regulator known as LafK. However, the regulatory role of LafK and its impact on bacteria-host interactions remain to be elucidated. In this study, we systematically investigated the regulatory role of LafK by constructing lafK deletion strain on the biological characteristics, virulence, and pathogenic process of P. plecoglossicida, as well as its impact on the host immune response. Our findings demonstrated that the deletion of lafK led to a significant down-regulation in the expression of type III secretion system-associated genes within the lateral flagella of P. plecoglossicida, consequently impairing bacterial swarming motility, biofilm formation, adhesion, and chemotaxis ability. Furthermore, in vitro infection experiments demonstrated that the deletion of lafK resulted in a diminished pathogenicity of P. plecoglossicida through down-regulation of flagella-related genes, thereby triggering an expedited immune response for bacterial clearance, and subsequently leading to reduced bacterial load within the host and attenuated tissue damage during infection. In summary, this study presents a novel theoretical framework for elucidating the regulatory mechanism of virulence in P. plecoglossicida.

Spatial transcriptomic analysis of HIV and tuberculosis coinfection in a humanized mouse model reveals specific transcription patterns, immune responses and early morphological alteration signaling

Mycobacterium tuberculosis (Mtb) and human immunodeficiency virus (HIV) coinfection is one of the biggest public health concerns worldwide. Both pathogens are adept at modulating immune response and, in the case of Mtb, even inducing structural modification of the affected tissue. The present study aimed at understanding the early phenotypical and functional changes in immune cell infiltration in the affected organ, using a humanized mouse model. The humanized mice were infected with either HIV or Mtb in single infection, or with both pathogens in coinfection. Three weeks after the infection, lung samples were collected, and spatial transcriptomics analysis was performed. This analysis revealed high infiltration of CD4+ T cells in Mtb infection, but not in HIV or coinfection. Coinfected mice also showed a minimal number of NK cells compared to the other groups. In addition to infection status, histological features also influenced the immune cell infiltration pattern in the lungs. Two distinct airway regions with distinct immune cell abundance patterns were detected by spatial transcriptome profiling. A lymphoid cell aggregate detected in coinfection lung exhibited distinct transcript profile. The cellular architecture in the lymphoid cell aggregate did not follow the spatial patterns seen in mature granulomas. However, lymphoid cell aggregates exhibited granuloma gene expression signatures, and pathways associated with reactive oxygen species production, oxidative phosphorylation, and TGFβ and interferon signaling similar to granulomas. This study revealed specific transcription patterns, immune responses and morphological alteration signaling in the early stage of HIV and Mtb infections.

Glutathione Depletion Exacerbates Hepatic Mycobacterium tuberculosis Infection

Extrapulmonary tuberculosis (EPTB) accounts for approximately 17% of all Mycobacterium tuberculosis (M.tb) infections globally. Immunocompromised individuals, such as those with HIV infection or type 2 diabetes mellitus (T2DM), are at an increased risk for EPTB. Previous studies have demonstrated that patients with HIV and T2DM exhibit diminished synthesis of glutathione (GSH) synthesizing enzymes. In a murine model, we showed that the diethyl maleate (DEM)-induced depletion of GSH in the lungs led to increased M.tb burden and an impaired pulmonary granulomatous response to M.tb infection. However, the effects of GSH depletion during active EPTB in the liver and spleen have yet to be elucidated. In this study, we evaluated hepatic GSH and malondialdehyde (MDA) levels, as well as cytokine profiles, in untreated and DEM-treated M.tb-infected wild-type (WT) C57BL/6 mice. Additionally, we assessed hepatic and splenic M.tb burdens and tissue pathologies. DEM treatment resulted in a significant decrease in the levels of the reduced form of GSH and an increase in MDA, oxidized GSH, and interleukin (IL)-6 levels. Furthermore, DEM-induced GSH decrease was associated with decreased production of IL-12 and IL-17 and elevated production of interferon-gamma (IFN-γ), tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β. A significant increase in M.tb growth was detected in the liver and spleen in DEM-treated M.tb-infected mice. Large, disorganized lymphocyte infiltrates were detected in the hepatic tissues of DEM-treated mice. Overall, GSH diminishment impaired the granulomatous response to M.tb in the liver and exacerbated M.tb growth in both the liver and spleen. These findings provide critical insights into the immunomodulatory role of GSH in TB pathogenesis and suggest potential therapeutic avenues for the treatment of extrapulmonary M.tb infections.

Growing Challenges of Lung Infections with Non-tuberculous Mycobacteria in Immunocompromised Patients: Epidemiology and Treatment

Non-tuberculous mycobacteria (NTM) are increasingly recognized as opportunistic pathogens in humans and animals, particularly affecting those with compromised immune systems. These bacteria encompass a diverse group of mycobacterial species that are responsible for a range of infections, with pulmonary and skin-related conditions being the most common. The rise in NTM infections in recent years is a growing concern for healthcare, highlighting the urgent need to improve our understanding of NTM epidemiology and treatment strategies. This article reviews the NTM species associated with lung infections in immunocompromised patients and underscores the critical importance of advancing diagnostic and therapeutic approaches. The review is based on a thorough analysis of scientific literature from databases such as PubMed, Scopus, and ScienceDirect, covering studies up to June 2024. Through this comprehensive analysis, the article aims to provide detailed insights into the complexities of NTM diseases and spur further research and innovation in combating these challenging infections.

Leveraging insights from cancer to improve tuberculosis therapy

Exploring and exploiting the microenvironmental similarities between pulmonary tuberculosis (TB) granulomas and malignant tumors has revealed new strategies for more efficacious host-directed therapies (HDTs). This opinion article discusses a paradigm shift in TB therapeutic development, drawing on critical insights from oncology. We summarize recent efforts to characterize and overcome key shared features between tumors and granulomas, including excessive fibrosis, abnormal angiogenesis, hypoxia and necrosis, and immunosuppression. We provide specific examples of cancer therapy application to TB to overcome these microenvironmental abnormalities, including matrix-targeting therapies, antiangiogenic agents, and immune-stimulatory drugs. Finally, we propose a new framework for combining HDTs with anti-TB agents to maximize therapeutic delivery and efficacy while reducing treatment dosages, duration, and harmful side effects to benefit TB patients.

Deciphering the Correlation between the Emergence of Lung Carcinoma Associated with Tuberculosis-related Inflammation

Lung cancer and tuberculosis (TB) are classified as the second-most life-threatening diseases globally. They both are exclusively represented as major public health risks and might exhibit similar symptoms, occasionally diagnosed simultaneously. Several epidemiological studies suggest that TB is a significant risk factor for the progression of lung cancer. The staggering mortality rates of pulmonary disorders are intrinsically connected to lung cancer and TB. Numerous factors play a pivotal role in the development of TB and may promote lung carcinogenesis, particularly among the geriatric population. Understanding the intricacies involved in the association between lung carcinogenesis and TB has become a crucial demand of current research. Consequently, this study aims to comprehensively review current knowledge on the relationship between tuberculosis-related inflammation and the emergence of lung carcinoma, highlighting the impact of persistent inflammation on lung tissue, immune modulation, fibrosis, aspects of reactive oxygen species, and an altered microenvironment that are linked to the progression of tuberculosis and subsequently trigger lung carcinoma.

A Comparative Pharmacokinetics Study of Orally and Intranasally Administered 8-Nitro-1,3-benzothiazin-4-one (BTZ043) Amorphous Drug Nanoparticles

BTZ043 is an 8-nitro-1,3-benzothiazin-4-one with potency against multidrug-resistant Mycobacterium tuberculosis. Low solubility and hepatic metabolism are linked to poor oral bioavailability. Amorphous drug nanoparticles (ADN) were formulated to improve the bioavailability. Comparative pharmacokinetics of BTZ043 ADN following intranasal (2.5 mg kg-1) and oral administration (25 mg kg-1) in Balb/c mice was investigated using oral BTZ043 drug suspensions (neat; 25 mg kg-1) as a standard-of-care reference. Plasma exposure following oral ADN administration was 8-fold higher than for oral neat BTZ043. Intranasal ADN increased plasma exposure 18-fold compared to oral neat BTZ043 after dose normalization. BTZ043 was detectable in lung lining fluid following ADN administration, but not after oral neat BTZ043 dosing. BTZ043 was cleared faster from the lung and plasma following intranasal administration with a shorter time above the minimum inhibitory concentration (MIC) compared to oral ADN. Since time > MIC is reported to drive activity, oral ADN may represent a promising delivery strategy for BTZ043.

Understanding the development of tuberculous granulomas: insights into host protection and pathogenesis, a review in humans and animals

Granulomas, organized aggregates of immune cells which form in response to Mycobacterium tuberculosis (Mtb), are characteristic but not exclusive of tuberculosis (TB). Despite existing investigations on TB granulomas, the determinants that differentiate host-protective granulomas from granulomas that contribute to TB pathogenesis are often disputed. Thus, the goal of this narrative review is to help clarify the existing literature on such determinants. We adopt the a priori view that TB granulomas are host-protective organelles and discuss the molecular and cellular determinants that induce protective granulomas and those that promote their failure. While reports about protective TB granulomas and their failure may initially seem contradictory, it is increasingly recognized that either deficiencies or excesses of the molecular and cellular components in TB granuloma formation may be detrimental to the host. More specifically, insufficient or excessive expression/representation of the following components have been reported to skew granulomas toward the less protective phenotype: (i) epithelioid macrophages; (ii) type 1 adaptive immune response; (iii) type 2 adaptive immune response; (iv) tumor necrosis factor; (v) interleukin-12; (vi) interleukin-17; (vii) matrix metalloproteinases; (viii) hypoxia in the TB granulomas; (ix) hypoxia inducible factor-1 alpha; (x) aerobic glycolysis; (xi) indoleamine 2,3-dioxygenase activity; (xii) heme oxygenase-1 activity; (xiii) immune checkpoint; (xiv) leukotriene A4 hydrolase activity; (xv) nuclear-factor-kappa B; and (xvi) transforming growth factor-beta. Rather, more precise and timely coordinated immune responses appear essential for eradication or containment of Mtb infection. Since there are several animal models of infection with Mtb, other species within the Mtb complex, and the surrogate Mycobacterium marinum - whether natural (cattle, elephants) or experimental (zebrafish, mouse, guinea pig, rabbit, mini pig, goat, non-human primate) infections - we also compared the TB granulomatous response and other pathologic lung lesions in various animals infected with one of these mycobacteria with that of human pulmonary TB. Identifying components that dictate the formation of host-protective granulomas and the circumstances that result in their failure can enhance our understanding of the macrocosm of human TB and facilitate the development of novel remedies - whether they be direct therapeutics or indirect interventions - to efficiently eliminate Mtb infection and prevent its pathologic sequelae.

Novel Prodrug Strategies for the Treatment of Tuberculosis

The emergence of drug-resistant strains of Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis, is on the rise and increasing antimicrobial resistance is a global threat. This phenomenon necessitates new drug design methods such as a prodrug strategy to develop novel antitubercular agents. The prodrug strategy is a viable and useful means to improve the absorption, distribution, metabolism, excretion and toxicity (ADMET) profiles of pharmacologically active agents. Granulomas are a pathological hallmark of M.tb infection and bear a remarkable resemblance to the tumour microenvironment, including regions of hypoxia. The hypoxic environment observed in the two structures offer an exceptional opportunity to deliver antitubercular agents selectively in a similar manner to hypoxia activated prodrugs in cancer therapy. Nitroimidazoles have been studied extensively as bioactivated prodrugs of cancer, and their suitability as substrates for mammalian reductases highlight their huge potential. This review will discuss the mechanism of action and resistance mechanisms of the current prodrugs used for the treatment of tuberculosis. It will also highlight the potential advantages and challenges of using hypoxia activated prodrugs as a viable strategy to target latent M.tb in hypoxic regions of granulomas.

Characterizing the immune response to Mycobacterium tuberculosis: a comprehensive narrative review and implications in disease relapse

Introduction

Tuberculosis remains the leading cause of death from infectious diseases among adults worldwide. To date, an overarching review of the immune response to Mtb in humans has not been fully elucidated, with innate immunity remaining poorly understood due to historic focus on adaptive immunity. Specifically, there is a major gap concerning the contribution of the immune system to overall bacterial clearance, particularly residual bacteria. This review aims to describe the time course of interactions between the host immune system and Mtb, from the start of the infection to the development of the adaptive response. Concordantly, we aim to crystallize the pathogenic effects and immunoevasive mechanisms of Mtb. The translational value of animal data is also discussed.

Methods

The literature search was conducted in the PubMed, ScienceDirect, and Google Scholar databases, which included reported research from 1990 until 2024. A total of 190 publications were selected and screened, of which 108 were used for abstraction and 86 were used for data extraction. Graphical summaries were created using the narrative information (i.e., recruitment, recognition, and response) to generate clear visual representations of the immune response at the cellular and molecular levels.

Results

The key cellular players included airway epithelial cells, alveolar epithelial cells, neutrophils, natural killer cells, macrophages, dendritic cells, T cells, and granulomatous lesions; the prominent molecular players included IFN-γ, TNF-α, and IL-10. The paper also sheds light on the immune response to residual bacteria and applications of the data.

Discussion

We provide a comprehensive characterization of the key immune players that are implicated in pulmonary tuberculosis, in line with the organs or compartments in which mycobacteria reside, offering a broad vignette of the immune response to Mtb and how it responds to residual bacteria. Ultimately, the data presented could provide immunological insights to help establish optimized criteria for identifying efficacious treatment regimens and durations for relapse prevention in the modeling and simulation space and wider fields.

In vivo imaging identified efficient antimicrobial treatment against Mycobacterium marinum infection in mouse footpads

Mycobacterium marinum (M. marinum) is the most common causative bacteria of cutaneous non-tuberculous mycobacterial (NTM) infections, including fish tank granuloma. Treating M. marinum-caused infection takes longer than other NTM diseases because M. marinum is less susceptible to antimicrobial agents. A standard treatment regimen for M. marinum infection has not been established yet, and few in vivo experiments have been performed in mammals to evaluate the bactericidal effects of antimicrobials. In this study, we developed a noninvasive in vivo imaging method to assess the therapeutic efficacy of antimicrobials against M. marinum infection. The data obtained using fluorescent protein or bioluminescence from luciferase will offer valuable insights into bacteria visualization across various bacterial infections. Furthermore, through this imaging technique, we demonstrated that combining clarithromycin, rifampicin, ethambutol, and minocycline effectively cleared M. marinum from the footpad. Granulomas with necrotic abscesses formed on the footpad of M. marinum-infected mice, primarily due to neutrophils involved in the host's cell-mediated immune response. Inflammatory cytokine and chemokine levels significantly increased 7 days post-infection, aligning with the footpad swelling and granuloma formation observed in the untreated group. Interestingly, immune mediators and cells induced by M. marinum footpad infection were crucial factors associated with hypersensitivity and granuloma formation, as seen in pulmonary tuberculosis. This novel imaging analysis using a cutaneous NTM mouse model might be a powerful tool for the comprehensive analysis of mycobacterial infections.

Granulomas in Common Variable Immunodeficiency Display Different Histopathological Features Compared to Other Granulomatous Diseases

Granulomatous disease affects up to 20% of patients with Common Variable Immunodeficiency (CVID). Granulomas are comprised of highly activated immune cells, and emerge in response to antigenic triggers. In CVID granulomas however, the underlying pathophysiology is unclear and the specific trigger remains unknown. Granuloma formation in CVID is often compared to sarcoidosis, although clinical context and prognosis differ, suggesting a different pathogenesis. The aim of this study was to investigate if the cellular organization and proteomics of granulomas in CVID is different from other granulomatous diseases. Therefore, tissue slides from formaldehyde fixed paraffin embedded biopsies obtained from patients with CVID, sarcoidosis, tuberculosis and foreign-material induced pseudo-sarcoidosis were stained with hematoxylin and eosin and assessed for histopathological characteristics. Targeted spatial protein analysis was performed, and immune fluorescent multiplex assays were used to analyze the cellular organization. Histological analysis revealed that CVID granulomas were smaller, less circumscribed, with fewer multinucleated giant cells and minimal fibrosis compared to the other granulomatous diseases. Spatial protein analysis showed that granulomas in all diseases expressed CD68, CD11c, CD44, CD127, and PD-L1. However in CVID, reduced expression of the fibrosis-related protein fibronectin, but enrichment of CD163, CD3 and FAPα inside CVID granulomas was observed. Immunofluorescence analysis conformed a different cellular organization in CVID granulomas with increased influx of neutrophils, macrophages, T and B lymphocytes. In conclusion, granulomas in CVID display a different histological and cellular organization with increased influx of myeloid and lymphoid cells, compared to sarcoidosis, tuberculosis and pseudo-sarcoidosis, indicating a distinct pathogenesis underlying granuloma formation.

Molecular and microbiological methods for the identification of nonreplicating Mycobacterium tuberculosis

Chronic tuberculosis (TB) disease, which requires months-long chemotherapy with multiple antibiotics, is defined by diverse pathological manifestations and bacterial phenotypes. Targeting drug-tolerant bacteria in the host is critical to achieving a faster and durable cure for TB. In order to facilitate this field of research, we need to consider the physiology of persistent MTB during infection, which is often associated with the nonreplicating (NR) state. However, the traditional approach to quantifying bacterial burden through colony enumeration alone only informs on the abundance of live bacilli at the time of sampling, and provides an incomplete picture of the replicative state of the pathogen and the extent to which bacterial replication is balanced by ongoing cell death. Modern approaches to profiling bacterial replication status provide a better understanding of inter- and intra-population dynamics under different culture conditions and in distinct host microenvironments. While some methods use molecular markers of DNA replication and cell division, other approaches take advantage of advances in the field of microfluidics and live-cell microscopy. Considerable effort has been made over the past few decades to develop preclinical in vivo models of TB infection and some are recognized for more closely recapitulating clinical disease pathology than others. Unique lesion compartments presenting different environmental conditions produce significant heterogeneity between Mycobacterium tuberculosis populations within the host. While cellular lesion compartments appear to be more permissive of ongoing bacterial replication, caseous foci are associated with the maintenance of M. tuberculosis in a state of static equilibrium. The accurate identification of nonreplicators and where they hide within the host have significant implications for the way novel chemotherapeutic agents and regimens are designed for persistent infections.

The roles of patient-derived xenograft models and artificial intelligence toward precision medicine

Patient-derived xenografts (PDX) involve transplanting patient cells or tissues into immunodeficient mice, offering superior disease models compared with cell line xenografts and genetically engineered mice. In contrast to traditional cell-line xenografts and genetically engineered mice, PDX models harbor the molecular and biologic features from the original patient tumor and are generationally stable. This high fidelity makes PDX models particularly suitable for preclinical and coclinical drug testing, therefore better predicting therapeutic efficacy. Although PDX models are becoming more useful, the several factors influencing their reliability and predictive power are not well understood. Several existing studies have looked into the possibility that PDX models could be important in enhancing our knowledge with regard to tumor genetics, biomarker discovery, and personalized medicine; however, a number of problems still need to be addressed, such as the high cost and time-consuming processes involved, together with the variability in tumor take rates. This review addresses these gaps by detailing the methodologies to generate PDX models, their application in cancer research, and their advantages over other models. Further, it elaborates on how artificial intelligence and machine learning were incorporated into PDX studies to fast-track therapeutic evaluation. This review is an overview of the progress that has been done so far in using PDX models for cancer research and shows their potential to be further improved in improving our understanding of oncogenesis.

Tuberculosis Diagnosis: Current, Ongoing, and Future Approaches

Tuberculosis (TB) remains an impactful infectious disease, leading to millions of deaths every year. Mycobacterium tuberculosis causes the formation of granulomas, which will determine, through the host-pathogen relationship, if the infection will remain latent or evolve into active disease. Early TB diagnosis is life-saving, especially among immunocompromised individuals, and leads to proper treatment, preventing transmission. This review addresses different approaches to diagnosing TB, from traditional methods such as sputum smear microscopy to more advanced molecular techniques. Integrating these techniques, such as polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP), has significantly improved the sensitivity and specificity of M. tuberculosis identification. Additionally, exploring novel biomarkers and applying artificial intelligence in radiological imaging contribute to more accurate and rapid diagnosis. Furthermore, we discuss the challenges of existing diagnostic methods, including limitations in resource-limited settings and the emergence of drug-resistant strains. While the primary focus of this review is on TB diagnosis, we also briefly explore the challenges and strategies for diagnosing non-tuberculous mycobacteria (NTM). In conclusion, this review provides an overview of the current landscape of TB diagnostics, emphasizing the need for ongoing research and innovation. As the field evolves, it is crucial to ensure that these advancements are accessible and applicable in diverse healthcare settings to effectively combat tuberculosis worldwide.

P-glycoprotein inhibitors as an adjunct therapy for TB

The primary challenge in TB treatment is the emergence of multidrug-resistant TB (MDR-TB). One of the major factors responsible for MDR is the upregulation of efflux pumps. Permeation-glycoprotein (P-gp), an efflux pump, hinders the bioavailability of the administered drugs inside the infected cells. Simultaneously, angiogenesis, the formation of new blood vessels, contributes to drug delivery complexities. TB infection triggers a cascade of events that upregulates the expression of angiogenic factors and P-gp. The combined action of P-gp and angiogenesis foster the emergence of MDR-TB. Understanding these mechanisms is pivotal for developing targeted interventions to overcome MDR in TB. P-gp inhibitors, such as verapamil, and anti-angiogenic drugs, including bevacizumab, have shown improvement in TB drug delivery to granuloma. In this review, we discuss the potential of P-gp inhibitors as an adjunct therapy to shorten TB treatment.

Tuberculosis patients with diabetes co-morbidity experience reduced Mycobacterium tuberculosis complex clearance

Objective

This study aimed to investigate the impact of diabetes mellitus (DM) on tuberculosis (TB) treatment response using bacterial clearance as a surrogate marker.

Method

We compared smear microscopy, culture, and tuberculosis molecular bacterial load assay (TB-MBLA) for treatment monitoring. Following that, bacterial clearance was longitudinally monitored among TB-only (TB without DM) and TB-diabetes (TBDM) patients using TB-MBLA.

Results

Ninety-three participants, including 59 TB-only and 34 TBDM patients, were enrolled. TB-only patients exhibited higher upper zone infiltrations (32/35 vs 16/22, p = 0.059) suggesting a trend towards significance, and significantly more cavitation in the same zone (16/18 vs 7/13, p = 0.028). There was a high proportion of Mycobacterium africanum (Maf) among the TBDM cohort (p = 0.0044).At baseline, TB-only patients exhibited a higher average bacterial burden (4.49 logeCFU/mL) compared to the TBDM group (3.91 logeCFU/mL) (p = 0.042). The bacterial load in the TB-only group decreased significantly during treatment but the TBDM group experienced delayed clearance throughout the intensive phase of anti-TB treatment even at day 56 (p = 0.028). The TB-only group demonstrated a shorter median time to TB-MBLA conversion to negative (57 days) compared to the TBDM group (62 days) (p = 0.022).

Conclusion

These findings underscore the urgent call for understanding the interplay between diabetes and TB, emphasizing the need for tailored interventions in optimizing TB care for individuals comorbid with diabetes.

T Cell Responses during Human Immunodeficiency Virus/Mycobacterium tuberculosis Coinfection

Coinfection with Mycobacterium tuberculosis (Mtb) and the human immunodeficiency virus (HIV) is a significant public health concern. Individuals infected with Mtb who acquire HIV are approximately 16 times more likely to develop active tuberculosis. T cells play an important role as both targets for HIV infection and mediators of the immune response against both pathogens. This review aims to synthesize the current literature and provide insights into the effects of HIV/Mtb coinfection on T cell populations and their contributions to immunity. Evidence from multiple in vitro and in vivo studies demonstrates that T helper responses are severely compromised during coinfection, leading to impaired cytotoxic responses. Moreover, HIV's targeting of Mtb-specific cells, including those within granulomas, offers an explanation for the severe progression of the disease. Herein, we discuss the patterns of differentiation, exhaustion, and transcriptomic changes in T cells during coinfection, as well as the metabolic adaptations that are necessary for T cell maintenance and functionality. This review highlights the interconnectedness of the immune response and the pathogenesis of HIV/Mtb coinfection.

Differential Expression of lncRNAs in HIV Patients with TB and HIV-TB with Anti-Retroviral Treatment

Tuberculosis (TB) is the leading cause of death among people with HIV-1 infection. To improve the diagnosis and treatment of HIV-TB patients, it is important to understand the mechanisms underlying these conditions. Here, we used an integrated genomics approach to analyze and determine the lncRNAs that are dysregulated in HIV-TB patients and HIV-TB patients undergoing anti-retroviral therapy (ART) using a dataset available in the public domain. The analyses focused on the portion of the genome transcribed into non-coding transcripts, which historically have been poorly studied and received less focus. This revealed that Mtb infection in HIV prominently up-regulates the expression of long non-coding RNA (lncRNA) genes DAAM2-AS1, COL4A2-AS1, LINC00599, AC008592.1, and CLRN1-AS1 and down-regulates the expression of lncRNAs AC111000.4, AC100803.3, AC016168.2, AC245100.7, and LINC02073. It also revealed that ART down-regulates the expression of some lncRNA genes (COL4A2-AS1, AC079210.1, MFA-AS1, and LINC01993) that are highly up-regulated in HIV-TB patients. Furthermore, the interrogation of the genomic regions that are associated with regulated lncRNAs showed enrichment for biological processes linked to immune pathways in TB-infected conditions. However, intriguingly, TB patients treated with ART showed completely opposite and non-overlapping pathways. Our findings suggest that lncRNAs could be used to identify critical diagnostic, prognostic, and treatment targets for HIV-TB patients.

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.

Therapeutic Modulation of Arginase with nor-NOHA Alters Immune Responses in Experimental Mouse Models of Pulmonary Tuberculosis including in the Setting of Human Immunodeficiency Virus (HIV) Co-Infection

L-arginine metabolism is strongly linked with immunity to mycobacteria, primarily through the antimicrobial activity of nitric oxide (NO). The potential to modulate tuberculosis (TB) outcomes through interventions that target L-arginine pathways are limited by an incomplete understanding of mechanisms and inadequate in vivo modeling. These gaps in knowledge are compounded for HIV and Mtb co-infections, where activation of arginase-1 due to HIV infection may promote survival and replication of both Mtb and HIV. We utilized in vitro and in vivo systems to determine how arginase inhibition using Nω-hydroxy-nor-L-arginine (nor-NOHA) alters L-arginine pathway metabolism relative to immune responses and disease outcomes following Mtb infection. Treatment with nor-NOHA polarized murine macrophages (RAW 264.7) towards M1 phenotype, increased NO, and reduced Mtb in RAW macrophages. In Balb/c mice, nor-NOHA reduced pulmonary arginase and increased the antimicrobial metabolite spermine in association with a trend towards reduced Mtb CFU in lung. In humanized immune system (HIS) mice, HIV infection increased plasma arginase and heightened the pulmonary arginase response to Mtb. Treatment with nor-NOHA increased cytokine responses to Mtb and Mtb/HIV in lung tissue but did not significantly alter bacterial burden or viral load. Our results suggest that L-arginine pathway modulators may have potential as host-directed therapies to augment antibiotics in TB chemotherapy.

Individualized lipid profile in urine-derived extracellular vesicles from clinical patients with Mycobacterium tuberculosis infections

Background

Lipids are a key nutrient source for the growth and reproduction of Mycobacterium tuberculosis (Mtb). Urine-derived extracellular vesicles (EVs), because of its non-invasive sampling, lipid enrichment, and specific sorting character, have been recognized as a promising research target for biomarker discovery and pathogenesis elucidation in tuberculosis (TB). We aim to profile lipidome of Mtb-infected individuals, offer novel lipid signatures for the development of urine-based TB testing, and provide new insights into the lipid metabolism after Mtb infection.

Methods

Urine-derived extracellular vesicles from 41 participants (including healthy, pulmonary tuberculosis, latent tuberculosis patients, and other lung disease groups) were isolated and individually detected using targeted lipidomics and proteomics technology platforms. Biomarkers were screened by multivariate and univariate statistical analysis and evaluated by SPSS software. Correlation analyses were performed on lipids and proteins using the R Hmisc package.

Results

Overall, we identified 226 lipids belonging to 14 classes. Of these, 7 potential lipid biomarkers for TB and 6 for latent TB infection (LTBI) were identified, all of which were classified into diacylglycerol (DAG), monoacylglycerol (MAG), free fatty acid (FFA), and cholesteryl ester (CE). Among them, FFA (20:1) was the most promising biomarker target in diagnosing TB/LTBI from other compared groups and also have great diagnostic performance in distinguishing TB from LTBI with AUC of 0.952. In addition, enhanced lipolysis happened as early as individuals got latent Mtb infection, and ratio of raft lipids was gradually elevated along TB progression.

Conclusion

This study demonstrated individualized lipid profile of urinary EVs in patients with Mtb infection, revealed novel potential lipid biomarkers for TB/LTBI diagnosis, and explored mechanisms by which EV lipid raft-dependent bio-processes might affect pathogenesis. It lays a solid foundation for the subsequent diagnosis and therapeutic intervention of TB.

A novel humanized mouse model for HIV and tuberculosis co-infection studies

Background

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), continues to be a major public health problem worldwide. The human immunodeficiency virus (HIV) is another equally important life-threatening pathogen. HIV infection decreases CD4+ T cell levels markedly increasing Mtb co-infections. An appropriate animal model for HIV/Mtb co-infection that can recapitulate the diversity of the immune response in humans during co-infection would facilitate basic and translational research in HIV/Mtb infections. Herein, we describe a novel humanized mouse model.

Methods

The irradiated NSG-SGM3 mice were transplanted with human CD34+ hematopoietic stem cells, and the humanization was monitored by staining various immune cell markers for flow cytometry. They were challenged with HIV and/or Mtb, and the CD4+ T cell depletion and HIV viral load were monitored over time. Before necropsy, the live mice were subjected to pulmonary function test and CT scan, and after sacrifice, the lung and spleen homogenates were used to determine Mtb load (CFU) and cytokine/chemokine levels by multiplex assay, and lung sections were analyzed for histopathology. The mouse sera were subjected to metabolomics analysis.

Results

Our humanized NSG-SGM3 mice were able to engraft human CD34+ stem cells, which then differentiated into a full-lineage of human immune cell subsets. After co-infection with HIV and Mtb, these mice showed decrease in CD4+ T cell counts overtime and elevated HIV load in the sera, similar to the infection pattern of humans. Additionally, Mtb caused infections in both lungs and spleen, and induced granulomatous lesions in the lungs. Distinct metabolomic profiles were also observed in the tissues from different mouse groups after co-infections.

Conclusion

The humanized NSG-SGM3 mice are able to recapitulate the pathogenic effects of HIV and Mtb infections and co-infection at the pathological, immunological and metabolism levels and are therefore a reproducible small animal model for studying HIV/Mtb co-infection.

Normalizing granuloma vasculature and matrix improves drug delivery and reduces bacterial burden in tuberculosis-infected rabbits

Host-directed therapies (HDTs) represent an emerging approach for bacterial clearance during tuberculosis (TB) infection. While most HDTs are designed and implemented for immuno-modulation, other host targets-such as nonimmune stromal components found in pulmonary granulomas-may prove equally viable. Building on our previous work characterizing and normalizing the aberrant granuloma-associated vasculature, here we demonstrate that FDA-approved therapies (bevacizumab and losartan, respectively) can be repurposed as HDTs to normalize blood vessels and extracellular matrix (ECM), improve drug delivery, and reduce bacterial loads in TB granulomas. Granulomas feature an overabundance of ECM and compressed blood vessels, both of which are effectively reduced by losartan treatment in the rabbit model of TB. Combining both HDTs promotes secretion of proinflammatory cytokines and improves anti-TB drug delivery. Finally, alone and in combination with second-line antitubercular agents (moxifloxacin or bedaquiline), these HDTs significantly reduce bacterial burden. RNA sequencing analysis of HDT-treated lung and granuloma tissues implicates up-regulated antimicrobial peptide and proinflammatory gene expression by ciliated epithelial airway cells as a putative mechanism of the observed antitubercular benefits in the absence of chemotherapy. These findings demonstrate that bevacizumab and losartan are well-tolerated stroma-targeting HDTs, normalize the granuloma microenvironment, and improve TB outcomes, providing the rationale to clinically test this combination in TB patients.

A Novel Humanized Mouse Model for HIV and Tuberculosis Co-infection Studies

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), continues to be a major public health problem worldwide. The human immunodeficiency virus (HIV) is another equally important life-threatening pathogen. Further, co-infections with HIV and Mtb have severe effects in the host, with people infected with HIV being fifteen to twenty-one times more likely to develop active TB. The use of an appropriate animal model for HIV/Mtb co-infection that can recapitulate the diversity of the immune response in humans would be a useful tool for conducting basic and translational research in HIV/Mtb infections. The present study was focused on developing a humanized mouse model for investigations on HIV-Mtb co-infection. Using NSG-SGM3 mice that can engraft human stem cells, our studies showed that they were able to engraft human CD34+ stem cells which then differentiate into a full-lineage of human immune cell subsets. After co-infection with HIV and Mtb, these mice showed decrease in CD4+ T cell counts overtime and elevated HIV load in the sera, similar to the infection pattern of humans. Additionally, Mtb caused infections in both lungs and spleen, and induced the development of granulomatous lesions in the lungs, detected by CT scan and histopathology. Distinct metabolomic profiles were also observed in the tissues from different mouse groups after co-infections. Our results suggest that the humanized NSG-SGM3 mice are able to recapitulate the effects of HIV and Mtb infections and co-infection in the human host at pathological, immunological and metabolism levels, providing a dependable small animal model for studying HIV/Mtb co-infection.

HIV-TB Coinfection: Current Therapeutic Approaches and Drug Interactions

The co-occurrence of human immunodeficiency virus (HIV) and tuberculosis (TB) infection poses a significant global health challenge. Treatment of HIV and TB co-infection often necessitates combination therapy involving antiretroviral therapy (ART) for HIV and anti-TB medications, which introduces the potential for drug-drug interactions (DDIs). These interactions can significantly impact treatment outcomes, the efficacy of treatment, safety, and overall patient well-being. This review aims to provide a comprehensive analysis of the DDIs between anti-HIV and anti-TB drugs as well as potential adverse effects resulting from the concomitant use of these medications. Furthermore, such findings may be used to develop personalized therapeutic strategies, dose adjustments, or alternative drug choices to minimize the risk of adverse outcomes and ensure the effective management of HIV and TB co-infection.

Automated quantitative assay of fibrosis characteristics in tuberculosis granulomas

Introduction

Granulomas, the pathological hallmark of Mycobacterium tuberculosis (Mtb) infection, are formed by different cell populations. Across various stages of tuberculosis conditions, most granulomas are classical caseous granulomas. They are composed of a necrotic center surrounded by multilayers of histocytes, with the outermost layer encircled by fibrosis. Although fibrosis characterizes the architecture of granulomas, little is known about the detailed parameters of fibrosis during this process.

Methods

In this study, samples were collected from patients with tuberculosis (spanning 16 organ types), and Mtb-infected marmosets and fibrotic collagen were characterized by second harmonic generation (SHG)/two-photon excited fluorescence (TPEF) microscopy using a stain-free, fully automated analysis program.

Results

Histopathological examination revealed that most granulomas share common features, including necrosis, solitary and compact structure, and especially the presence of multinuclear giant cells. Masson's trichrome staining showed that different granuloma types have varying degrees of fibrosis. SHG imaging uncovered a higher proportion (4%~13%) of aggregated collagens than of disseminated type collagens (2%~5%) in granulomas from matched tissues. Furthermore, most of the aggregated collagen presented as short and thick clusters (200~620 µm), unlike the long and thick (200~300 µm) disseminated collagens within the matched tissues. Matrix metalloproteinase-9, which is involved in fibrosis and granuloma formation, was strongly expressed in the granulomas in different tissues.

Discussion

Our data illustrated that different tuberculosis granulomas have some degree of fibrosis in which collagen strings are short and thick. Moreover, this study revealed that the SHG imaging program could contribute to uncovering the fibrosis characteristics of tuberculosis granulomas.

Novel Insights into the Pathogenesis of Human Post-Primary Tuberculosis from Archival Material of the Pre-Antibiotic Era, 1931-1947

OBJECTIVES

Primary and post-primary tuberculosis (TB) are distinct entities. The aim of this study was to study the histopathology of primary and post-primary TB by using the unique human autopsy material from the pre-antibiotic era, 1931-1947.

MATERIAL AND METHODS

Autopsy data were collected from the autopsy journals, and the human tissue was collected from the pathology archives at the Department of Pathology, the Gades Institute.

RESULTS

Histological presentations of TB lesions showed great diversity within a single lung. Post-primary TB starts as a pneumonia forming early lesions, characterized by the infiltration of foamy macrophages containing mycobacterial antigens within alveoli, and progressing to necrotic pneumonias with an increasing density of mycobacterial antigens in the lesions. These necrotic pneumonic lesions appeared to either resolve as fibrocaseous lesions or lead to cavitation. The typical granulomatous inflammation, the hallmark of TB lesions, appeared later in the post-primary TB and surrounded the pneumonic lesions. These post-primary granulomas contained lesser mycobacterial antigens as compared to necrotic pneumonia.

CONCLUSIONS

Immunopathogenesis of post-primary TB is different from primary TB and starts as pneumonia. The early lesions of post-primary TB may progress or regress, holding the key to understanding how a host can develop the disease despite an effective TB immunity.

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.

Necrosis, netosis, and apoptosis in pulmonary tuberculosis and type-2 diabetes mellitus. Clues from the patient's serum

Pulmonary tuberculosis (PTB) and type 2 diabetes mellitus (T2DM) are two inflammatory diseases whose pathology involves neutrophils (NEU) as key participants. Countless inflammatory elements produced at the lesion sites leak into the blood and are distributed systemically. The study aimed to investigate the effect of the serum of patients with PTB, T2DM, and PTB + T2DM on the cellular and nuclear morphology of healthy NEU. Monolayers of NEU were prepared and incubated with sera from PTB (n꓿ 10), T2DM (n꓿10), PTB + T2DM (n꓿ 10) patients, or sera from healthy people (n = 10). Monolayers were stained for histones, elastase, and myeloperoxidase for NETosis, annexin V for apoptosis, and Iris fuchsia for necrosis. Hoechst stain (DNA) was used to identify the nuclear alterations. Necrosis was the predominant alteration. Sera from PTB + T2DM were the most potent change inducers. Normal sera did not induce cell alterations. The blood of TBP and T2DM patients carries a myriad of abnormal elements that induce necrosis of NEU in normal people, thus reflecting what might occur in the neutrophils of the patients themselves. These findings reinforce the participation of NEU in the pathology of these diseases. Necrosis is expected to be the most frequent neutrophil-induced alteration in tuberculosis and diabetes mellitus.

T Cell Response in Tuberculosis-Infected Patients Vaccinated against COVID-19

Many studies have focused on SARS-CoV-2 and Mycobacterium tuberculosis (Mtb) co-infection consequences. However, after a vaccination plan against COVID-19, the cases of severe disease and death are consistently controlled, although cases of asymptomatic and mild COVID-19 still happen together with tuberculosis (TB) cases. Thus, in this context, we sought to compare the T cell response of COVID-19-non-vaccinated and -vaccinated patients with active tuberculosis exposed to SARS-CoV-2 antigens. Flow cytometry was used to analyze activation markers (i.e., CD69 and CD137) and cytokines (IFN-γ, TNFα, IL-17, and IL-10) levels in CD4+ and CD8+ T cells upon exposure to SARS-CoV-2 peptides. The data obtained showed that CD8+ T cells from non-vaccinated TB patients present a high frequency of CD69 and TNF-α after viral challenge compared to vaccinated TB donors. Conversely, CD4+ T cells from vaccinated TB patients show a high frequency of IL-10 after spike peptide stimulus compared to non-vaccinated patients. No differences were observed in the other parameters analyzed. The results suggest that this reduced immune balance in coinfected individuals may have consequences for pathogen control, necessitating further research to understand its impact on clinical outcomes after COVID-19 vaccination in those with concurrent SARS-CoV-2 and Mtb infections.

Visualization of the individual blood microbiome to study the etiology of sarcoidosis

Introduction

Single microbial pathogens or host-microbiome dysbiosis are the causes of lung diseases with suspected infectious etiology. Metagenome sequencing provides an overview of the microbiome content. Due to the rarity of most granulomatous lung diseases collecting large systematic datasets is challenging. Thus, single-patient data often can only be summarized visually.

Objective

To increase the information gain from a single-case metagenome analysis we suggest a quantitative and qualitative approach.

Results

The 16S metagenomic results of 7 patients with pulmonary sarcoidosis were compared with those of 22 healthy individuals. From lysed blood, total microbial DNA was extracted and sequenced. Cleaned data reads were identified taxonomically using Kraken 2 software. Individual metagenomic data were visualized with a Sankey diagram, Krona chart, and a heat-map. We identified five genera that were exclusively present or significantly enhanced in patients with sarcoidosis - Veillonella, Prevotella, Cutibacterium, Corynebacterium, and Streptococcus.

Conclusions

Our approach can characterize the blood microbiome composition and diversity in rare diseases at an individual level. Investigation of the blood microbiome in patients with granulomatous lung diseases of unknown etiology, such as sarcoidosis could enhance our comprehension of their origin and pathogenesis and potentially uncover novel personalized therapeutics.

Comparative pathology of experimental pulmonary tuberculosis in animal models

Research in human tuberculosis (TB) is limited by the availability of human tissues from patients, which is often altered by therapy and treatment. Thus, the use of animal models is a key tool in increasing our understanding of the pathogenesis, disease progression and preclinical evaluation of new therapies and vaccines. The granuloma is the hallmark lesion of pulmonary tuberculosis, regardless of the species or animal model used. Although animal models may not fully replicate all the histopathological characteristics observed in natural, human TB disease, each one brings its own attributes which enable researchers to answer specific questions regarding TB immunopathogenesis. This review delves into the pulmonary pathology induced by Mycobacterium tuberculosis complex (MTBC) bacteria in different animal models (non-human primates, rodents, guinea pigs, rabbits, cattle, goats, and others) and compares how they relate to the pulmonary disease described in humans. Although the described models have demonstrated some histopathological features in common with human pulmonary TB, these data should be considered carefully in the context of this disease. Further research is necessary to establish the most appropriate model for the study of TB, and to carry out a standard characterisation and score of pulmonary lesions.

Cell state transition analysis identifies interventions that improve control of Mycobacterium tuberculosis infection by susceptible macrophages

Understanding cell state transitions and purposefully controlling them to improve therapies is a longstanding challenge in biological research and medicine. Here, we identify a transcriptional signature that distinguishes activated macrophages from the tuberculosis (TB) susceptible and resistant mice. We then apply the cSTAR (cell state transition assessment and regulation) approach to data from screening-by-RNA sequencing to identify chemical perturbations that shift the transcriptional state of tumor necrosis factor (TNF)-activated TB-susceptible macrophages toward that of TB-resistant cells, i.e., prevents their aberrant activation without suppressing beneficial TNF responses. Last, we demonstrate that the compounds identified with this approach enhance the resistance of the TB-susceptible mouse macrophages to virulent Mycobacterium tuberculosis.

The immune response in tubercular uveitis and its implications for treatment: From anti-tubercular treatment to host-directed therapies

Tubercular uveitis (TB-uveitis) remains a conundrum in the uveitis field, which is mainly related to the diverse clinical phenotypes of TB-uveitis. Moreover, it remains difficult to differentiate whether Mycobacterium tuberculosis (Mtb) is present in the ocular tissues, elicits a heightened immune response without Mtb invasion in ocular tissues, or even induces an anti-retinal autoimmune response. Gaps in the immuno-pathological knowledge of TB-uveitis likely delay timely diagnosis and appropriate management. In the last decade, the immunopathophysiology of TB-uveitis and its clinical management, including experts' consensus to treat or not to treat certain conditions with anti-tubercular treatment (ATT), have been extensively investigated. In the meantime, research on TB treatment, in general, is shifting more toward host-directed therapies (HDT). Given the complexities of the host-Mtb interaction, enhancement of the host immune response is expected to boost the effectiveness of ATT and help overcome the rising burden of drug-resistant Mtb strains in the population. This review will summarize the current knowledge on the immunopathophysiology of TB-uveitis and recent advances in treatment modalities and outcomes of TB-uveitis, capturing results gathered from high- and low-burden TB countries with ATT as the mainstay of treatment. Moreover, we outline the recent progress of HDT development in the pulmonary TB field and discuss the possibility of its applicability to TB-uveitis. The concept of HDT might help direct future development of efficacious therapy for TB-uveitis, although more in-depth research on the immunoregulation of this disease is still necessary.

Mycobacterium tuberculosis cell-wall and antimicrobial peptides: a mission impossible?

Mycobacterium tuberculosis (Mtb) is one of the most important infectious agents worldwide and causes more than 1.5 million deaths annually. To make matters worse, the drug resistance among Mtb strains has risen substantially in the last few decades. Nowadays, it is not uncommon to find patients infected with Mtb strains that are virtually resistant to all antibiotics, which has led to the urgent search for new molecules and therapies. Over previous decades, several studies have demonstrated the efficiency of antimicrobial peptides to eliminate even multidrug-resistant bacteria, making them outstanding candidates to counterattack this growing health problem. Nevertheless, the complexity of the Mtb cell wall makes us wonder whether antimicrobial peptides can effectively kill this persistent Mycobacterium. In the present review, we explore the complexity of the Mtb cell wall and analyze the effectiveness of antimicrobial peptides to eliminate the bacilli.

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 Fe2/3+, 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.

Spatiotemporal perspectives on tuberculosis chemotherapy

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), accounts for over ten million infections and over 1.5 million deaths every year [1]. Upon infection, the seesaw between Mtb and our immune systems creates microenvironments that are compositionally distinctive and changing over time. While the field has begun to better understand the spatial complexity of TB disease, our understanding and experimental dissection of the temporal dynamics of TB and TB drug treatment is much more rudimentary. However, it is the combined spatiotemporal heterogeneity of TB disease that creates niches and time windows within which the pathogen can survive and thrive during treatment. Here, we review the emerging data on the interactions of spatial and temporal dynamics as they relate to TB disease and treatment. A better understanding of the interactions of Mtb, host, and antibiotics through space and time will elucidate treatment failure and potentially identify opportunities for new TB treatment regimens.

Cell state transition analysis identifies interventions that improve control of M. tuberculosis infection by susceptible macrophages

Understanding cell state transitions and purposefully controlling them to improve therapies is a longstanding challenge in biological research and medicine. Here, we identify a transcriptional signature that distinguishes activated macrophages from TB-susceptible and TB-resistant mice. We then apply the cSTAR (cell State Transition Assessment and Regulation) approach to data from screening-by-RNA sequencing to identify chemical perturbations that shift the. transcriptional state of the TB-susceptible macrophages towards that of TB-resistant cells. Finally, we demonstrate that the compounds identified with this approach enhance resistance of the TB-susceptible mouse macrophages to virulent M. tuberculosis .