The IL-13/IL-4Rα axis is involved in tuberculosis-associated pathology

Macrophage Differentiation and Metabolic Adaptation in Mycobacterial Infections

The adaptation of macrophages-the most common tissue-resident immune cells-to metabolic and microbial cues with high local variability is essential for the maintenance of organ integrity. In homeostasis, macrophages show largely predictable tissue-specific differentiation, as recently revealed by multidimensional methods. However, chronic infections with human-adapted pathogens substantially contribute to the differentiation complexity of tissue macrophages, which has been only partially resolved. Specifically, the response to mycobacterial species-which range from Mycobacterium tuberculosis (with highest specificity for humans, broad organ tropism, yet tissue-specific disease phenotypes) to environmental mycobacteria with humans as accidental hosts-may serve as a paradigm of tissue macrophage adaptation mechanisms. While mycobacterial species-specific tissue preferences are partially related to the mode of acquisition and pathogen characteristics, evolutionary convergence with macrophages driven by metabolic features of the target organ likely contributes to infection resistance and immunopathology. In this review, we unravel the mechanisms of tissue-specific macrophage differentiation and its limitations in mycobacterial infections.

Aberrant macrophage activation and maladaptive lung repair promote tuberculosis progression uniquely in the lung

Pulmonary tuberculosis (PTB) represents 85% of the disease burden caused by Mycobacterium tuberculosis (Mtb) and promotes aerosol transmission infecting about a quarter of people globally. Most Mtb infections are effectively limited within primary granulomatous lesions. Containment failures lead to hematogenous spread and the formation of post-primary destructive PTB lesions. Factors that favor Mtb survival and replication in the lungs after hematogenous spread despite systemic immunity represent appealing targets for host-directed TB therapies, but are currently unknown. We developed a novel mouse model that mimics progression of chronic post-primary PTB in humans: wherein PTB lesions form after hematogenous spread from a remote primary lesion in immunocompetent but TB-susceptible B6.Sst1S mice. The B6.Sst1S mice developed PTB lesions featuring granulomatous pneumonia, bronchogenic expansion and broncho-occlusion closely resembling post-primary PTB in humans. Using spatial transcriptomic and fluorescent multiplexed immunochemistry, we demonstrated the expansion of myeloid cell populations with the appearance of alternatively activated macrophages, dissolution of initial lymphoid follicles, and accumulation of de-differentiated lung epithelial cells in the advanced PTB lesions. To determine whether lung parenchymal cells or lung oxygenation were necessary for the pulmonary TB progression, we implanted lung and spleen fragments subcutaneously to serve as potential targets for hematogenous spread. The lung (but not spleen) implants displayed characteristic organized granulomas with necrosis and Mtb replication demonstrating that deleterious interactions of aberrantly activated macrophages with the inflammation-injured lung resident cells, and possibly hypoxia, not oxygenation, are critical determinants of PTB progression in immunocompetent hosts. Necrotic TB lesions also developed in subcutaneous implants of human lung tissue in mice with human immune system after respiratory infection. These animal models may serve to further dissect the lung-specific mechanisms of host susceptibility to virulent Mtb and for testing therapeutic interventions targeting these mechanisms.

Arginine metabolism in myeloid cells in health and disease

Metabolic flexibility is key for the function of myeloid cells. Arginine metabolism is integral to the regulation of myeloid cell responses. Nitric oxide (NO) production from arginine is vital for the antimicrobial and pro-inflammatory responses. Conversely, the arginase 1 (ARG1)-dependent switch between the branch of NO production and polyamine synthesis downregulates inflammation and promotes recovery of tissue homeostasis. Creatine metabolism is key for energy supply and proline metabolism is required for collagen synthesis. Myeloid ARG1 also regulates extracellular arginine availability and T cell responses in parasitic diseases and cancer. Cancer, surgery, sepsis and persistent inflammation in chronic inflammatory diseases, such as neuroinflammatory diseases or arthritis, are associated with dysregulation of arginine metabolism in myeloid cells. Here, we review current knowledge on arginine metabolism in different myeloid cell types, such as macrophages, neutrophils, microglia, osteoclasts, tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs) and myeloid-derived suppressor cells (MDSCs). A deeper understanding of the function of arginine metabolism in myeloid cells will improve our knowledge on the pathology of several diseases and may set the platform for novel therapeutic applications.

Fitness costs of Mycobacterium tuberculosis resistant to rifampicin is compensated by rapid Th2 polarization mediated by early and high IL-4 production during mice infection

It was a general belief that drug resistance in Mycobacterium tuberculosis (Mtb) was associated with lesser virulence, particularly rifampicin resistance, which is usually produced by mutations in the RNA polymerase Beta subunit (RpoB). Interestingly, this kind of bacterial mutations affect gene transcription with significant effects on bacterial physiology and metabolism, affecting also the bacterial antigenic constitution that in consequence can produce diverse immune responses and disease outcome. In the present study, we show the results of the Mtb clinical isolate A96, which is resistant to rifampicin and when used to infect BALB/c mice showed hypervirulence, apparently by rapidly polarization of the Th2 immune response through early and high production of IL-4. The 2D-PAGE analysis of the secretome of Mtb A96 showed 204 spots, and by immunoproteome, seven proteins that were differentially recognized with the sera of infected mice on day 28 were identified by LC-MS/MS. The proteins correspond to surface antigens, virulence factors, and energy metabolism enzymes. Some of them are immunodominant antigens, such as LpqH lipoprotein that induces IL-4 secretion in cell suspensions from the lung and spleen of mice infected with Mtb A96 at 28 days postinfection, suggesting that LpqH could be one of the main antigens involved in the Th2 polarization. The reduction of Mtb A96 hypervirulence in IL-4Rα-/- BALB/c mice highlights the importance of IL-4 induction and Th2 response polarization and the immunopathological response. Thus, high and rapid bias to Th2 response is a mechanism of Mtb virulence, which could be mediated by rifampicin-resistant Mtb isolates, probably by high production and secretion of specific antigens.

The clinical-stage drug BTZ-043 accumulates in murine tuberculosis lesions and efficiently acts against Mycobacterium tuberculosis

The development of granulomas with central necrosis harboring Mycobacterium tuberculosis (Mtb) is the hallmark of human tuberculosis (TB). New anti-TB therapies need to effectively penetrate the cellular and necrotic compartments of these lesions and reach sufficient concentrations to eliminate Mtb. BTZ-043 is a novel antibiotic showing good bactericidal activity in humans in a phase IIa trial. Here, we report on lesional BTZ-043 concentrations severalfold above the minimal-inhibitory-concentration and the substantial local efficacy of BTZ-043 in interleukin-13-overexpressing mice, which mimic human TB pathology of granuloma necrosis. High-resolution MALDI imaging further reveals that BTZ-043 diffuses and accumulates in the cellular compartment, and fully penetrates the necrotic center. This is the first study that visualizes an efficient penetration and accumulation of a clinical-stage TB drug in human-like centrally necrotizing granulomas and that also determines its lesional activity. Our results most likely predict a substantial bactericidal effect of BTZ-043 at these hard-to-reach sites in TB patients.

Assessment of lower respiratory tract microbiota associated with pulmonary tuberculosis in children

BACKGROUND

The respiratory microbiota plays a crucial role in the development of tuberculosis (TB). While existing research has underscored imbalances in the respiratory microbiota of adult patients with TB, information regarding the lower respiratory tract (LRT) microbiota in pediatric patients with TB remains scarce.

METHODS

We employed 16S rRNA gene sequencing technology to investigate the LRT microbial communities of 85 children of different ages with active TB of different severities, 33 children with infectious diseases other than TB, and 48 sex- and age-matched healthy children.

RESULTS

A marked imbalance in the respiratory microbiota was observed in children with TB, highlighted by reduced alpha diversity and a distinct microbial community structure. Comparative analysis indicated that patients with severe TB exhibited lower Neisseria levels than those with non-severe TB (1.01% vs. 3.93%, respectively; p = .02). Streptococcus and Gemella levels were lower in bacteriologically confirmed TB cases compared with clinically diagnosed cases, and higher in healthy children younger than 10 years old than in the older group. Spearman correlation analysis demonstrated significant associations between the microbiota of the LRT and cytokine concentrations in the sputum of children with TB (e.g., an inverse correlation between Veillonella and interleukin-17A).

CONCLUSIONS

TB induced significant dysbiosis in the LRT microbiota of children that was associated with disease severity and the immunological response in the respiratory tract. Our findings may offer a deeper understanding of the role of the respiratory microbiome in TB pathogenesis and progression.

Pathogenesis of Post-Tuberculosis Lung Disease: Defining Knowledge Gaps and Research Priorities at the Second International Post-Tuberculosis Symposium

Post-tuberculosis (post-TB) lung disease is increasingly recognized as a major contributor to the global burden of chronic lung disease, with recent estimates indicating that over half of TB survivors have impaired lung function after successful completion of TB treatment. However, the pathologic mechanisms that contribute to post-TB lung disease are not well understood, thus limiting the development of therapeutic interventions to improve long-term outcomes after TB. This report summarizes the work of the Pathogenesis and Risk Factors Committee for the Second International Post-Tuberculosis Symposium, which took place in Stellenbosch, South Africa, in April 2023. The committee first identified six areas with high translational potential: 1) tissue matrix destruction, including the role of matrix metalloproteinase dysregulation and neutrophil activity; 2) fibroblasts and profibrotic activity; 3) granuloma fate and cell death pathways; 4) mycobacterial factors, including pathogen burden; 5) animal models; and 6) the impact of key clinical risk factors, including HIV, diabetes, smoking, malnutrition, and alcohol. We share the key findings from a literature review of those areas, highlighting knowledge gaps and areas where further research is needed.

Investigating the treatment shortening potential of a combination of bedaquiline, delamanid and moxifloxacin with and without sutezolid, in a murine tuberculosis model with confirmed drug exposures

BACKGROUND

New and shorter regimens against multi-drug resistant tuberculosis (TB) remain urgently needed. To inform treatment duration in clinical trials, this study aimed to identify human pharmacokinetic equivalent doses, antimycobacterial and sterilizing activity of a novel regimen, containing bedaquiline, delamanid, moxifloxacin and sutezolid (BDMU), in the standard mouse model (BALB/c) of Mycobacterium tuberculosis (Mtb) infection.

METHODS

Treatment of mice with B25D0.6M200U200, B25D0.6M200, B25D0.6M200(U2003) or H10R10Z150E100 (isoniazid, rifampicin, pyrazinamide, ethambutol, HRZE), started 3 weeks after Mtb infection. Bactericidal activity was assessed after 1, 2, 3 and 4 months of treatment and relapse rates were assessed 3 months after completing treatment durations of 2, 3 and 4 months.

RESULTS

B25D0.6M200U200 generated human equivalent exposures in uninfected BALB/c mice. After 1 month of treatment, a higher bactericidal activity was observed for the B25D0.6M200U200 and the B25D0.6M200 regimen compared to the standard H10R10Z150E100 regimen. Furthermore, 3 months of therapy with both BDM-based regimens resulted in negative lung cultures, whereas all H10R10Z150E100 treated mice were still culture positive. After 3 months of therapy 7% and 13% of mice relapsed receiving B25D0.6M200U200 and B25D0.6M200, respectively, compared to 40% for H10R10Z150E100 treatment showing an increased sterilizing activity of both BDM-based regimens.

CONCLUSIONS

BDM-based regimens, with and without sutezolid, have a higher efficacy than the HRZE regimen in the BALB/c model of TB, with some improvement by adding sutezolid. By translating these results to TB patients, this novel BDMU regimen should be able to reduce treatment duration by 25% compared to HRZE therapy.

Imaging the Architecture of Granulomas Induced by Mycobacterium tuberculosis Infection with Single-molecule Fluorescence In Situ Hybridization

Granulomas are an important hallmark of Mycobacterium tuberculosis infection. They are organized and dynamic structures created when immune cells assemble around the sites of infection in the lungs that locally restrict M. tuberculosis growth and the host's inflammatory responses. The cellular architecture of granulomas is traditionally studied by immunofluorescence labeling of surface markers on the host cells. However, very few Abs are available for model animals used in tuberculosis research, such as nonhuman primates and rabbits, and secreted immunological markers such as cytokines cannot be imaged in situ using Abs. Furthermore, traditional phenotypic surface markers do not provide sufficient resolution for the detection of the many subtypes and differentiation states of immune cells. Using single-molecule fluorescence in situ hybridization (smFISH) and its derivatives, amplified smFISH and iterative smFISH, we developed a platform for imaging mRNAs encoding immune markers in rabbit and macaque tuberculosis granulomas. Multiplexed imaging for several mRNA and protein markers was followed by quantitative measurement of the expression of these markers in single cells. An analysis of the combinatorial expressions of these markers allowed us to classify the cells into several subtypes, and to chart their densities within granulomas. For one mRNA target, hypoxia-inducible factor-1α, we imaged its mRNA and protein in the same cells, demonstrating the specificity of the probes. This method paves the way for defining granular differentiation states and cell subtypes from transcriptomic data, identifying key mRNA markers for these cell subtypes, and then locating the cells in the spatial context of granulomas.

Reappraising the Role of T Cell-Derived IFN-γ in Restriction of Mycobacterium tuberculosis in the Murine Lung

T cells producing IFN-γ have long been considered a stalwart for immune protection against Mycobacterium tuberculosis (Mtb), but their relative importance to pulmonary immunity has been challenged by murine studies that achieved protection by adoptively transferred Mtb-specific IFN-γ-/- T cells. Using IFN-γ-/- T cell chimeric mice and adoptive transfer of IFN-γ-/- T cells into TCRβ-/-δ-/- mice, we demonstrate that control of lung Mtb burden is in fact dependent on T cell-derived IFN-γ, and, furthermore, mice selectively deficient in T cell-derived IFN-γ develop exacerbated disease compared with T cell-deficient control animals, despite equivalent lung bacterial burdens. Deficiency in T cell-derived IFN-γ skews infected and bystander monocyte-derived macrophages to an alternative M2 phenotype and promotes neutrophil and eosinophil influx. Our studies support an important role for T cell-derived IFN-γ in pulmonary immunity against tuberculosis.

Identifying the Interaction Between Tuberculosis and SARS-CoV-2 Infections via Bioinformatics Analysis and Machine Learning

The number of patients with COVID-19 caused by severe acute respiratory syndrome coronavirus 2 is still increasing. In the case of COVID-19 and tuberculosis (TB), the presence of one disease affects the infectious status of the other. Meanwhile, coinfection may result in complications that make treatment more difficult. However, the molecular mechanisms underpinning the interaction between TB and COVID-19 are unclear. Accordingly, transcriptome analysis was used to detect the shared pathways and molecular biomarkers in TB and COVID-19, allowing us to determine the complex relationship between COVID-19 and TB. Two RNA-seq datasets (GSE114192 and GSE163151) from the Gene Expression Omnibus were used to find concerted differentially expressed genes (DEGs) between TB and COVID-19 to identify the common pathogenic mechanisms. A total of 124 common DEGs were detected and used to find shared pathways and drug targets. Several enterprising bioinformatics tools were applied to perform pathway analysis, enrichment analysis and networks analysis. Protein-protein interaction analysis and machine learning was used to identify hub genes (GAS6, OAS3 and PDCD1LG2) and datasets GSE171110, GSE54992 and GSE79362 were used for verification. The mechanism of protein-drug interactions may have reference value in the treatment of coinfection of COVID-19 and TB.

Effect of IL-17A on the immune response to pulmonary tuberculosis induced by high- and low-virulence strains of Mycobacterium bovis

Tuberculosis (TB) is an infectious, chronic, and progressive disease occurring globally. Human TB is caused mainly by Mycobacterium tuberculosis (M. tuberculosis), while the main causative agent of bovine TB is Mycobacterium bovis (M. bovis). The latter is one of the most important cattle pathogens and is considered the main cause of zoonotic TB worldwide. The mechanisms responsible for tissue damage (necrosis) during post-primary TB remain elusive. Recently, IL-17A was reported to be important for protection against M. tuberculosis infection, but it is also related to the production of an intense inflammatory response associated with necrosis. We used two M. bovis isolates with different levels of virulence and high IL-17A production to study this important cytokine's contrasting functions in a BALB/c mouse model of pulmonary TB. In the first part of the study, the gene expression kinetics and cellular sources of IL-17A were determined by real time PCR and immunohistochemistry respectively. Non-infected lungs showed low production of IL-17A, particularly by the bronchial epithelium, while lungs infected with the low-virulence 534 strain showed high IL-17A expression on Day 3 post-infection, followed by a decrease in expression in the early stage of the infection and another increase during late infection, on Day 60, when very low bacillary burdens were found. In contrast, infection with the highly virulent strain 04-303 induced a peak of IL-17A expression on Day 14 of infection, 1 week before extensive pulmonary necrosis was seen, being lymphocytes and macrophages the most important sources. In the second part of the study, the contribution of IL-17A to immune protection and pulmonary necrosis was evaluated by suppressing IL-17A via the administration of specific blocking antibodies. Infection with M. bovis strain 534 and treatment with IL-17A neutralizing antibodies did not affect mouse survival but produced a significant increase in bacillary load and a non-significant decrease in inflammatory infiltrate and granuloma area. In contrast, mice infected with the highly virulent 04-303 strain and treated with IL-17A blocking antibodies showed a significant decrease in survival, an increase in bacillary loads on Day 24 post-infection, and significantly more and earlier necrosis. Our results suggest that high expression of IL-17A is more related to protection than necrosis in a mouse model of pulmonary TB induced by M. bovis strains.

The effect of previous SARS-CoV-2 infection on systemic immune responses in individuals with tuberculosis

Background

The impact of previous SARS-CoV-2 infection on the systemic immune response during tuberculosis (TB) disease has not been explored.

Methods

An observational, cross-sectional cohort was established to evaluate the systemic immune response in persons with pulmonary tuberculosis with or without previous SARS-CoV-2 infection. Those participants were recruited in an outpatient referral clinic in Rio de Janeiro, Brazil. TB was defined as a positive Xpert-MTB/RIF Ultra and/or a positive culture of Mycobacterium tuberculosis from sputum. Stored plasma was used to perform specific serology to identify previous SARS-CoV-2 infection (TB/Prex-SCoV-2 group) and confirm the non- infection of the tuberculosis group (TB group). Plasmatic cytokine/chemokine/growth factor profiling was performed using Luminex technology. Tuberculosis severity was assessed by clinical and laboratory parameters. Participants from TB group (4.55%) and TB/Prex-SCoV-2 (0.00%) received the complete COVID-19 vaccination.

Results

Among 35 participants with pulmonary TB, 22 were classified as TB/Prex-SCoV-2. The parameters associated with TB severity, together with hematologic and biochemical data were similar between the TB and TB/Prex-SCoV-2 groups. Among the signs and symptoms, fever and dyspnea were significantly more frequent in the TB group than the TB/Prex-SCoV-2 group (p < 0,05). A signature based on lower amount of plasma EGF, G-CSF, GM-CSF, IFN-α2, IL-12(p70), IL-13, IL-15, IL-17, IL-1β, IL-5, IL-7, and TNF-β was observed in the TB/Prex-SCoV-2 group. In contrast, MIP-1β was significantly higher in the TB/Prex-SCoV-2 group than the TB group.

Conclusion

TB patients previously infected with SARS-CoV-2 had an immunomodulation that was associated with lower plasma concentrations of soluble factors associated with systemic inflammation. This signature was associated with a lower frequency of symptoms such as fever and dyspnea but did not reflect significant differences in TB severity parameters observed at baseline.

Dermatology practice updates in mycobacterial disease

Atypical mycobacterial infections are commonly acquired through exposure to water, and tuberculosis remains highly endemic in many parts of the world. In this era of global connection, travel, and immigration, it is more important than ever to maintain a high index of suspicion for infection from cutaneous tuberculosis and atypical mycobacteria. Epidemics related to surgical procedures have been related to inadequate sterilization, as almost 50% of public water supplies harbor mycobacteria. Improved diagnostic techniques for these microbes, including Auramine-Rhodamine staining and rapid detection of mycobacteria and drug susceptibilities through PCR and MALDI-TOF, have improved detection and treatment outcomes. Given an increasing number of patients on immunosuppressive therapies, clinicians must remain vigilant.

Re-appraising the role of T-cell derived interferon gamma in restriction of Mycobacterium tuberculosis in the murine lung: T-cell derived IFNγ is required to restrict pulmonary Mtb

T cells producing interferon gamma (IFNγ) have long been considered a stalwart for immune protection against Mycobacterium tuberculosis (Mtb), but their relative importance to pulmonary immunity has been challenged by murine studies which achieved protection by adoptively transferred Mtb-specific IFNγ-/- T cells. Using IFNγ-/- T cell chimeric mice and adoptive transfer of IFNγ-/- T cells into TCRβ-/-δ-/- mice, we demonstrate that control of lung Mtb burden is in fact dependent on T cell-derived IFNγ, and furthermore, mice selectively deficient in T cell-derived IFNγ develop exacerbated disease compared to T cell-deficient controls despite equivalent lung bacterial burdens. Deficiency in T cell-derived IFNγ skews infected and bystander monocyte-derived macrophages (MDMs) to an alternative M2 phenotype, and promotes neutrophil and eosinophil influx. Our studies support an important role for T cell-derived IFNγ in pulmonary immunity against TB.

Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis

Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.

Innate Type-2 Cytokines: From Immune Regulation to Therapeutic Targets

The intricate role of innate type-2 cytokines in immune responses is increasingly acknowledged for its dual nature, encompassing both protective and pathogenic dimensions. Ranging from defense against parasitic infections to contributing to inflammatory diseases like asthma, fibrosis, and obesity, these cytokines intricately engage with various innate immune cells. This review meticulously explores the cellular origins of innate type-2 cytokines and their intricate interactions, shedding light on factors that amplify the innate type-2 response, including TSLP, IL-25, and IL-33. Recent advancements in therapeutic strategies, specifically the utilization of biologics targeting pivotal cytokines (IL-4, IL-5, and IL-13), are discussed, offering insights into both challenges and opportunities. Acknowledging the pivotal role of innate type-2 cytokines in orchestrating immune responses positions them as promising therapeutic targets. The evolving landscape of research and development in this field not only propels immunological knowledge forward but also holds the promise of more effective treatments in the future.

The sound of silent RNA in tuberculosis and the lncRNA role on infection

Tuberculosis (TB) is one of the leading causes of death worldwide, and Diabetes Mellitus is one of the major comorbidities (TB/DM) associated with the disease. A total of 103 differentially expressed ncRNAs have been identified in the TB and TB/DM comparisons. A machine learning algorithm was employed to identify the most informative lncRNAs: ADM-DT, LINC02009, LINC02471, SOX2-OT, and GK-AS1. These lncRNAs presented substantial accuracy in classifying TB from HC (AUCs >0.85) and TB/DM from HC (AUCs >0.90) in the other three countries. Genes with significant correlations with the five lncRNAs enriched common pathways in Brazil and India for both TB and TB/DM. This suggests that lncRNAs play an important role in the regulation of genes related to the TB immune response.

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.

Antimicrobial peptides as drugs with double response against Mycobacterium tuberculosis coinfections in lung cancer

Tuberculosis and lung cancer are, in many cases, correlated diseases that can be confused because they have similar symptoms. Many meta-analyses have proven that there is a greater chance of developing lung cancer in patients who have active pulmonary tuberculosis. It is, therefore, important to monitor the patient for a long time after recovery and search for combined therapies that can treat both diseases, as well as face the great problem of drug resistance. Peptides are molecules derived from the breakdown of proteins, and the membranolytic class is already being studied. It has been proposed that these molecules destabilize cellular homeostasis, performing a dual antimicrobial and anticancer function and offering several possibilities of adaptation for adequate delivery and action. In this review, we focus on two important reason for the use of multifunctional peptides or peptides, namely the double activity and no harmful effects on humans. We review some of the main antimicrobial and anti-inflammatory bioactive peptides and highlight four that have anti-tuberculosis and anti-cancer activity, which may contribute to obtaining drugs with this dual functionality.

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 .

IL-12p40 is essential but not sufficient for Francisella tularensis LVS clearance in chronically infected mice

IL-12p40 plays an important role in F. tularensis Live Vaccine Strain (LVS) clearance that is independent of its functions as a part of the heterodimeric cytokines IL-12p70 or IL-23. In contrast to WT, p35, or p19 knockout (KO) mice, p40 KO mice infected with LVS develop a chronic infection that does not resolve. Here, we further evaluated the role of IL-12p40 in F. tularensis clearance. Despite reduced IFN-γ production, primed splenocytes from p40 KO and p35 KO mice appeared functionally similar to those from WT mice during in vitro co-culture assays of intramacrophage bacterial growth control. Gene expression analysis revealed a subset of genes that were upregulated in re-stimulated WT and p35 KO splenocytes, but not p40 KO splenocytes, and thus are candidates for involvement in F. tularensis clearance. To directly evaluate a potential mechanism for p40 in F. tularensis clearance, we reconstituted protein levels in LVS-infected p40 KO mice using either intermittent injections of p40 homodimer (p80) or treatment with a p40-producing lentivirus construct. Although both delivery strategies yielded readily detectable levels of p40 in sera and spleens, neither treatment had a measurable impact on LVS clearance by p40 KO mice. Taken together, these studies demonstrate that clearance of F. tularensis infection depends on p40, but p40 monomers and/or dimers alone are not sufficient.

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

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

Reinventing the human tuberculosis (TB) granuloma: Learning from the cancer field

Tuberculosis (TB) remains one of the deadliest infectious diseases in the world and every 20 seconds a person dies from TB. An important attribute of human TB is induction of a granulomatous inflammation that creates a dynamic range of local microenvironments in infected organs, where the immune responses may be considerably different compared to the systemic circulation. New and improved technologies for in situ quantification and multimodal imaging of mRNA transcripts and protein expression at the single-cell level have enabled significantly improved insights into the local TB granuloma microenvironment. Here, we review the most recent data on regulation of immunity in the TB granuloma with an enhanced focus on selected in situ studies that enable spatial mapping of immune cell phenotypes and functions. We take advantage of the conceptual framework of the cancer-immunity cycle to speculate how local T cell responses may be enhanced in the granuloma microenvironment at the site of Mycobacterium tuberculosis infection. This includes an exploratory definition of "hot", immune-inflamed, and "cold", immune-excluded TB granulomas that does not refer to the level of bacterial replication or metabolic activity, but to the relative infiltration of T cells into the infected lesions. Finally, we reflect on the current knowledge and controversy related to reactivation of active TB in cancer patients treated with immune checkpoint inhibitors such as PD-1/PD-L1 and CTLA-4. An understanding of the underlying mechanisms involved in the induction and maintenance or disruption of immunoregulation in the TB granuloma microenvironment may provide new avenues for host-directed therapies that can support standard antibiotic treatment of persistent TB disease.

Investigation on Probable Association Between IL-13, IL-13RA1, and IL-13RA2 Genes Polymorphism and Pulmonary Tuberculosis

Objective

Our study aimed to explore the association of IL-13, IL-13RA1, and IL-13RA2 genes polymorphisms with PTB susceptibility and its clinical features.

Methods

Nine SNPs were genotyped by improved multiple ligase detection reaction (iMLDR) in 476 PTB patients and 473 controls. The association between these SNPs and PTB risk was analyzed using SPSS software and haplotype analysis was assessed using SHEsis software.

Results

The IL-13RA1 rs2495636 GA genotype frequency in PTB patients was significantly decreased, and IL-13RA2 rs5946039 A allele was related to the lower risk of PTB. In IL-13 gene, rs20541 variant was found to be associated with PTB risk under recessive mode. Moreover, IL-13RA1 rs141573089 C allele was significantly lower in PTB presenting with fever, drug resistance, and CC genotype was decreased in PTB presenting with leukopenia. IL-13RA1 rs2495636 polymorphism was associated with drug resistance, pulmonary infection, and IL-13RA2 rs3795175, rs638376 polymorphisms were related to drug resistance in PTB patients.

Conclusion

IL-13 rs20541, IL-13RA1 rs2495636, IL-13RA2 rs5946039 polymorphisms might be contributed to the genetic background of PTB in Chinese population.

Conventional and pathogenic Th2 cells in inflammation, tissue repair, and fibrosis

Type 2 helper T (Th2) cells, a subset of CD4⁺ T cells, play an important role in the host defense against pathogens and allergens by producing Th2 cytokines, such as interleukin-4 (IL-4), IL-5, and IL-13, to trigger inflammatory responses. Emerging evidence reveals that Th2 cells also contribute to the repair of injured tissues after inflammatory reactions. However, when the tissue repair process becomes chronic, excessive, or uncontrolled, pathological fibrosis is induced, leading to organ failure and death. Thus, proper control of Th2 cells is needed for complete tissue repair without the induction of fibrosis. Recently, the existence of pathogenic Th2 (Tpath2) cells has been revealed. Tpath2 cells produce large amounts of Th2 cytokines and induce type 2 inflammation when activated by antigen exposure or tissue injury. In recent studies, Tpath2 cells are suggested to play a central role in the induction of type 2 inflammation whereas the role of Tpath2 cells in tissue repair and fibrosis has been less reported in comparison to conventional Th2 cells. In this review, we discuss the roles of conventional Th2 cells and pathogenic Th2 cells in the sequence of tissue inflammation, repair, and fibrosis.

Bacillus Calmette-Guérin-Induced Human Mast Cell Activation Relies on IL-33 Priming

Bacillus Calmette-Guérin (BCG) vaccine is an attenuated strain of Mycobacterium bovis that provides weak protection against tuberculosis (TB). Mast cells (MCs) are tissue-resident immune cells strategically that serve as the first line of defence against pathogenic threats. In this study, we investigated the response of human MCs (hMCs) to BCG. We found that naïve hMCs exposed to BCG did not secrete cytokines, degranulate, or support the uptake and intracellular growth of bacteria. Since we could show that in hMCs IL-33 promotes the transcription of host-pathogen interaction, cell adhesion and activation genes, we used IL-33 for cell priming. The treatment of hMCs with IL-33, but not IFN-γ, before BCG stimulation increased IL-8, MCP-1 and IL-13 secretion, and induced an enhanced expression of the mycobacteria-binding receptor CD48. These effects were comparable to those caused by the recombinant Mycobacterium tuberculosis (Mtb) 19-KDa lipoprotein. Finally, stimulation of hMCs with IL-33 incremented MC-BCG interactions. Thus, we propose that IL-33 may improve the immunogenicity of BCG vaccine by sensitising hMCs.

Genetic and hormonal mechanisms underlying sex-specific immune responses in tuberculosis

Tuberculosis (TB), the world's deadliest bacterial infection, afflicts more human males than females, with a male/female (M/F) ratio of 1.7. Sex disparities in TB prevalence, pathophysiology, and clinical manifestations are widely reported, but the underlying biological mechanisms remain largely undefined. This review assesses epidemiological data on sex disparity in TB, as well as possible underlying hormonal and genetic mechanisms that might differentially modulate innate and adaptive immune responses in males and females, leading to sex differences in disease susceptibility. We consider whether this sex disparity can be extended to the efficacy of vaccines and discuss novel animal models which may offer mechanistic insights. A better understanding of the biological factors underpinning sex-related immune responses in TB may enable sex-specific personalized therapies for TB.

No smoke without fire: the impact of cigarette smoking on the immune control of tuberculosis

Cigarette smoke (CS) exposure is a key risk factor for both active and latent tuberculosis (TB). It is associated with delayed diagnosis, more severe disease progression, unfavourable treatment outcomes and relapse after treatment. Critically, CS exposure is common in heavily populated areas with a high burden of TB, such as China, India and the Russian Federation. It is therefore prudent to evaluate interventions for TB while taking into account the immunological impacts of CS exposure. This review is a mechanistic examination of how CS exposure impairs innate barrier defences, as well as alveolar macrophage, neutrophil, dendritic cell and T-cell functions, in the context of TB infection and disease.

Tuberculostearic Acid-Containing Phosphatidylinositols as Markers of Bacterial Burden in Tuberculosis

One-fourth of the global human population is estimated to be infected with strains of the Mycobacterium tuberculosis complex (MTBC), the causative agent of tuberculosis (TB). Using lipidomic approaches, we show that tuberculostearic acid (TSA)-containing phosphatidylinositols (PIs) are molecular markers for infection with clinically relevant MTBC strains and signify bacterial burden. For the most abundant lipid marker, detection limits of ∼10² colony forming units (CFUs) and ∼10³ CFUs for bacterial and cell culture systems were determined, respectively. We developed a targeted lipid assay, which can be performed within a day including sample preparation—roughly 30-fold faster than in conventional methods based on bacterial culture. This indirect and culture-free detection approach allowed us to determine pathogen loads in infected murine macrophages, human neutrophils, and murine lung tissue. These marker lipids inferred from mycobacterial PIs were found in higher levels in peripheral blood mononuclear cells of TB patients compared to healthy individuals. Moreover, in a small cohort of drug-susceptible TB patients, elevated levels of these molecular markers were detected at the start of therapy and declined upon successful anti-TB treatment. Thus, the concentration of TSA-containing PIs can be used as a correlate for the mycobacterial burden in experimental models and in vitro systems and may prospectively also provide a clinically relevant tool to monitor TB severity.

Mycobacterium tuberculosis infection drives a type I IFN signature in lung lymphocytes

Mycobacterium tuberculosis (Mtb) infects 25% of the world's population and causes tuberculosis (TB), which is a leading cause of death globally. A clear understanding of the dynamics of immune response at the cellular level is crucial to design better strategies to control TB. We use the single-cell RNA sequencing approach on lung lymphocytes derived from healthy and Mtb-infected mice. Our results show the enrichment of the type I IFN signature among the lymphoid cell clusters, as well as heat shock responses in natural killer (NK) cells from Mtb-infected mice lungs. We identify Ly6A as a lymphoid cell activation marker and validate its upregulation in activated lymphoid cells following infection. The cross-analysis of the type I IFN signature in human TB-infected peripheral blood samples further validates our results. These findings contribute toward understanding and characterizing the transcriptional parameters at a single-cell depth in a highly relevant and reproducible mouse model of TB.

Do Anti-tuberculosis Drugs Reach Their Target?─High-Resolution Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging Provides Information on Drug Penetration into Necrotic Granulomas

Tuberculosis (TB) is characterized by mycobacteria-harboring centrally necrotizing granulomas. The efficacy of anti-TB drugs depends on their ability to reach the bacteria in the center of these lesions. Therefore, we developed a mass spectrometry (MS) imaging workflow to evaluate drug penetration in tissue. We employed a specific mouse model that─in contrast to regular inbred mice─strongly resembles human TB pathology. Mycobacterium tuberculosis was inactivated in lung sections of these mice by γ-irradiation using a protocol that was optimized to be compatible with high spatial resolution MS imaging. Different distributions in necrotic granulomas could be observed for the anti-TB drugs clofazimine, pyrazinamide, and rifampicin at a pixel size of 30 μm. Clofazimine, imaged here for the first time in necrotic granulomas of mice, showed higher intensities in the surrounding tissue than in necrotic granulomas, confirming data observed in TB patients. Using high spatial resolution drug and lipid imaging (5 μm pixel size) in combination with a newly developed data analysis tool, we found that clofazimine does penetrate to some extent into necrotic granulomas and accumulates in the macrophages inside the granulomas. These results demonstrate that our imaging platform improves the predictive power of preclinical animal models. Our workflow is currently being applied in preclinical studies for novel anti-TB drugs within the German Center for Infection Research (DZIF). It can also be extended to other applications in drug development and beyond. In particular, our data analysis approach can be used to investigate diffusion processes by MS imaging in general.

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

The defining pathology of tuberculosis is the granuloma, an organized structure derived from host immune cells that surrounds infecting Mycobacterium tuberculosis. As the location of much of the bacteria in the infected host, the granuloma is a central point of interaction between the host and the infecting bacterium. This review describes the signals and cellular reprogramming that drive granuloma formation. Further, as a central point of host-bacterial interactions, the granuloma shapes disease outcome by altering host immune responses and bacterial susceptibility to antibiotic treatment, as discussed herein. This new understanding of granuloma biology and the signaling behind it highlights the potential for host-directed therapies targeting the granuloma to enhance antibiotic access and tuberculosis-specific immune responses.

Cytokine Receptors-Regulators of Antimycobacterial Immune Response

Cytokine receptors are critical regulators of the antimycobacterial immune response, playing a key role in initiating and coordinating the recruitment and activation of immune cells during infection. They recognize and bind specific cytokines and are involved in inducing intracellular signal transduction pathways that regulate a diverse range of biological functions, including proliferation, differentiation, metabolism and cell growth. Due to mutations in cytokine receptor genes, defective signaling may contribute to increased susceptibility to mycobacteria, allowing the pathogens to avoid killing and immune surveillance. This paper provides an overview of cytokine receptors important for the innate and adaptive immune responses against mycobacteria and discusses the implications of receptor gene defects for the course of mycobacterial infection.

Interleukin-13 overexpressing mice represent an advanced pre-clinical model for detecting the distribution of anti-mycobacterial drugs within centrally necrotizing granulomas

The Mycobacterium tuberculosis-harboring granuloma with a necrotic center surrounded by a fibrous capsule is the hallmark of tuberculosis (TB). For a successful treatment, antibiotics need to penetrate these complex structures to reach their bacterial targets. Hence, animal models reflecting the pulmonary pathology of TB patients are of particular importance to improve the preclinical validation of novel drug candidates. M. tuberculosis-infected interleukin-13-overexpressing (IL-13^tg) mice develop a TB pathology very similar to patients and, in contrast to other mouse models, also share pathogenetic mechanisms. Accordingly, IL-13^tg animals represent an ideal model for analyzing the penetration of novel anti-TB drugs into various compartments of necrotic granulomas by matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI-MS imaging). In the present study, we evaluated the suitability of BALB/c IL-13^tg mice for determining the antibiotic distribution within necrotizing lesions. To this end, we established a workflow based on the inactivation of M. tuberculosis by gamma irradiation while preserving lung tissue integrity and drug distribution, which is essential for correlating drug penetration with lesion pathology. MALDI-MS imaging analysis of clofazimine, pyrazinamide, and rifampicin revealed a drug-specific distribution within different lesion types, including cellular granulomas, developing in BALB/c wild-type mice, and necrotic granulomas in BALB/c IL-13^tg animals, emphasizing the necessity of preclinical models reflecting human pathology. Most importantly, our study demonstrates that BALB/c IL-13^tg mice recapitulate the penetration of antibiotics into human lesions. Therefore, our workflow in combination with the IL-13^tg mouse model provides an improved and accelerated evaluation of novel anti-TB drugs and new regimens in the preclinical stage.

Gasdermin D mediates host cell death but not interleukin-1β secretion in Mycobacterium tuberculosis-infected macrophages

Necrotic cell death represents a major pathogenic mechanism of Mycobacterium tuberculosis (Mtb) infection. It is increasingly evident that Mtb induces several types of regulated necrosis but how these are interconnected and linked to the release of pro-inflammatory cytokines remains unknown. Exploiting a clinical cohort of tuberculosis patients, we show here that the number and size of necrotic lesions correlates with IL-1β plasma levels as a strong indicator of inflammasome activation. Our mechanistic studies reveal that Mtb triggers mitochondrial permeability transition (mPT) and subsequently extensive macrophage necrosis, which requires activation of the NLRP3 inflammasome. NLRP3-driven mitochondrial damage is dependent on proteolytic activation of the pore-forming effector protein gasdermin D (GSDMD), which links two distinct cell death machineries. Intriguingly, GSDMD, but not the membranolytic mycobacterial ESX-1 secretion system, is dispensable for IL-1β secretion from Mtb-infected macrophages. Thus, our study dissects a novel mechanism of pathogen-induced regulated necrosis by identifying mitochondria as central regulatory hubs capable of delineating cytokine secretion and lytic cell death.

Inhibition of Granuloma Triglyceride Synthesis Imparts Control of Mycobacterium tuberculosis Through Curtailed Inflammatory Responses

Lipid metabolism plays a complex and dynamic role in host-pathogen interaction during Mycobacterium tuberculosis infection. While bacterial lipid metabolism is key to the success of the pathogen, the host also offers a lipid rich environment in the form of necrotic caseous granulomas, making this association beneficial for the pathogen. Accumulation of the neutral lipid triglyceride, as lipid droplets within the cellular cuff of necrotic granulomas, is a peculiar feature of pulmonary tuberculosis. The role of triglyceride synthesis in the TB granuloma and its impact on the disease outcome has not been studied in detail. Here, we identified diacylglycerol O-acyltransferase 1 (DGAT1) to be essential for accumulation of triglyceride in necrotic TB granulomas using the C3HeB/FeJ murine model of infection. Treatment of infected mice with a pharmacological inhibitor of DGAT1 (T863) led to reduction in granuloma triglyceride levels and bacterial burden. A decrease in bacterial burden was associated with reduced neutrophil infiltration and degranulation, and a reduction in several pro-inflammatory cytokines including IL1β, TNFα, IL6, and IFNβ. Triglyceride lowering impacted eicosanoid production through both metabolic re-routing and via transcriptional control. Our data suggests that manipulation of lipid droplet homeostasis may offer a means for host directed therapy in Tuberculosis.

Channeling macrophage polarization by rocaglates increases macrophage resistance to Mycobacterium tuberculosis

Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatment of primary macrophages with rocaglates enhanced phagosome-lysosome fusion and control of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization toward the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g., chronic bacterial infections, allergies, and, possibly, certain tumors.

WNT6/ACC2-induced storage of triacylglycerols in macrophages is exploited by Mycobacterium tuberculosis

In view of emerging drug-resistant tuberculosis (TB), host-directed adjunct therapies are urgently needed to improve treatment outcomes with currently available anti-TB therapies. One approach is to interfere with the formation of lipid-laden "foamy" macrophages in the host, as they provide a nutrient-rich host cell environment for Mycobacterium tuberculosis (Mtb). Here, we provide evidence that Wnt family member 6 (WNT6), a ligand of the evolutionarily conserved Wingless/Integrase 1 (WNT) signaling pathway, promotes foam cell formation by regulating key lipid metabolic genes including acetyl-CoA carboxylase 2 (ACC2) during pulmonary TB. Using genetic and pharmacological approaches, we demonstrated that lack of functional WNT6 or ACC2 significantly reduced intracellular triacylglycerol (TAG) levels and Mtb survival in macrophages. Moreover, treatment of Mtb-infected mice with a combination of a pharmacological ACC2 inhibitor and the anti-TB drug isoniazid (INH) reduced lung TAG and cytokine levels, as well as lung weights, compared with treatment with INH alone. This combination also reduced Mtb bacterial numbers and the size of mononuclear cell infiltrates in livers of infected mice. In summary, our findings demonstrate that Mtb exploits WNT6/ACC2-induced storage of TAGs in macrophages to facilitate its intracellular survival, a finding that opens new perspectives for host-directed adjunctive treatment of pulmonary TB.

IL-4-Responsive B Cells Are Detrimental During Chronic Tuberculosis Infection in Mice

In tuberculosis, T cell-mediated immunity is extensively studied whilst B cells received limited attention in human and mice. Of interest, Mycobacterium tuberculosis (Mtb) does increase IL-4 Receptor-alpha (IL4Rα) expression in murine B cells. To better understand the role of IL4Rα signalling in B cells, we compared wild type mice with B cell-specific IL4Rα deficient mice (mb1creIL-4Rα-/lox mice). Chronic Mtb aerosol infection in mb1creIL-4Rα-/lox mice reduced lung and spleen bacterial burdens, compared to littermate (IL-4Rα-/lox) control animals. Consequently, lung pathology, inflammation and inducible nitric oxide synthase (iNOS) expression were reduced in the lungs of mb1creIL-4Rα-/lox mice, which was also accompanied by increased lung IgA and decreased IgG1 levels. Furthermore, intratracheal adoptive transfer of wild-type B cells into B cell-specific IL4Rα deficient mice reversed the protective phenotype. Moreover, constitutively mCherry expressing Mtb showed decreased association with B cells from mb1creIL-4Rα-/lox mice ex vivo. In addition, supernatants from Mtb-exposed B cells of mb1creIL-4Rα-/lox mice also increased the ability of macrophages to produce nitric oxide, IL-1β, IL-6 and TNF. Together, this demonstrates that IL-4-responsive B cells are detrimental during the chronic phase of tuberculosis in mice with perturbed antibody profiles, inflammatory cytokines and tnf and stat1 levels in the lungs.

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

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

Targeting of myeloid-derived suppressor cells by all-trans retinoic acid as host-directed therapy for human tuberculosis

Conventional anti-tuberculosis (TB) therapies comprise lengthy antibiotic treatment regimens, exacerbated by multi-drug resistant and extensively drug resistant mycobacterial strains. We assessed the ability of all-trans retinoic acid (ATRA), as repurposed compound serving as host-directed therapy (HDT), to counteract the suppressive effects of myeloid-derived suppressor cells (MDSCs) obtained from active TB cases (untreated or during week one of treatment) on T-cell responsiveness. We show for the first time that MDSCs suppress non-specific T-cell activation and production of interleukin (IL)-2, IL-4, IL-13 and GM-CSF via contact-dependent mechanisms. ATRA treatment decreases MDSC frequency, but fails to mature MDSCs to non-suppressive, terminally differentiated myeloid cells and does not restore T-cell function or cytokine production in the presence of MDSCs. The impact of ATRA treatment on improved immunity, using the concentration tested here, is likely to be minimal, but further identification and development of MDSC-targeting TB host-directed therapies are warranted.

Monocyte progenitors give rise to multinucleated giant cells

The immune response to mycobacteria is characterized by granuloma formation, which features multinucleated giant cells as a unique macrophage type. We previously found that multinucleated giant cells result from Toll-like receptor-induced DNA damage and cell autonomous cell cycle modifications. However, the giant cell progenitor identity remained unclear. Here, we show that the giant cell-forming potential is a particular trait of monocyte progenitors. Common monocyte progenitors potently produce cytokines in response to mycobacteria and their immune-active molecules. In addition, common monocyte progenitors accumulate cholesterol and lipids, which are prerequisites for giant cell transformation. Inducible monocyte progenitors are so far undescribed circulating common monocyte progenitor descendants with high giant cell-forming potential. Monocyte progenitors are induced in mycobacterial infections and localize to granulomas. Accordingly, they exhibit important immunological functions in mycobacterial infections. Moreover, their signature trait of high cholesterol metabolism may be piggy-backed by mycobacteria to create a permissive niche.

A non-canonical type 2 immune response coordinates tuberculous granuloma formation and epithelialization

The central pathogen-immune interface in tuberculosis is the granuloma, a complex host immune structure that dictates infection trajectory and physiology. Granuloma macrophages undergo a dramatic transition in which entire epithelial modules are induced and define granuloma architecture. In tuberculosis, relatively little is known about the host signals that trigger this transition. Using the zebrafish-Mycobacterium marinum model, we identify the basis of granuloma macrophage transformation. Single-cell RNA-sequencing analysis of zebrafish granulomas and analysis of Mycobacterium tuberculosis-infected macaques reveal that, even in the presence of robust type 1 immune responses, countervailing type 2 signals associate with macrophage epithelialization. We find that type 2 immune signaling, mediated via stat6, is absolutely required for epithelialization and granuloma formation. In mixed chimeras, stat6 acts cell autonomously within macrophages, where it is required for epithelioid transformation and incorporation into necrotic granulomas. These findings establish the signaling pathway that produces the hallmark structure of mycobacterial infection.

Pulmonary Mycosis Drives Forkhead Box Protein A2 Degradation and Mucus Hypersecretion through Activation of the Spleen Tyrosine Kinase-Epidermal Growth Factor Receptor-AKT/Extracellular Signal-Regulated Kinase 1/2 Signaling

Pulmonary mycoses are difficult to treat and detrimental to patients. Fungal infections modulate the lung immune response, induce goblet cell hyperplasia and metaplasia, and mucus hypersecretion in the airways. Excessive mucus clogs small airways and reduces pulmonary function by decreasing oxygen exchange, leading to respiratory distress. The forkhead box protein A2 (FOXA2) is a transcription factor that regulates mucus homeostasis in the airways. However, little is known whether pulmonary mycosis modulates FOXA2 function. Herein, we investigated whether Blastomyces dermatitidis and Histoplasma capsulatum-infected canine and feline lungs and airway epithelial cells could serve as higher animal models to examine the relationships between fungal pneumonia and FOXA2-regulated airway mucus homeostasis. The results indicate that fungal infection down-regulated FOXA2 expression in airway epithelial cells, with concomitant overexpression of mucin 5AC (MUC5AC) and mucin 5B (MUC5B) mucins. Mechanistic studies reveal that B. dermatitidis infection, as well as β-glucan exposure, activated the Dectin-1-SYK-epidermal growth factor receptor-AKT/extracellular signal-regulated kinase 1/2 signaling pathway that inhibits the expression of FOXA2, resulting in overexpression of MUC5AC and MUC5B in canine airway cells. Further understanding of the role of FOXA2 in mucus hypersecretion may lead to novel therapeutics against excessive mucus in both human and veterinary patients with pulmonary mycosis.

The Role of gp130 Cytokines in Tuberculosis

Protective immune responses to Mycobacterium tuberculosis (Mtb) infection substantially depend on a delicate balance within cytokine networks. Thus, immunosuppressive therapy by cytokine blockers, as successfully used in the management of various chronic inflammatory diseases, is often connected with an increased risk for tuberculosis (TB) reactivation. Hence, identification of alternative therapeutics which allow the treatment of inflammatory diseases without compromising anti-mycobacterial immunity remains an important issue. On the other hand, in the context of novel therapeutic approaches for the management of TB, host-directed adjunct therapies, which combine administration of antibiotics with immunomodulatory drugs, play an increasingly important role, particularly to reduce the duration of treatment. In both respects, cytokines/cytokine receptors related to the common receptor subunit gp130 may serve as promising target candidates. Within the gp130 cytokine family, interleukin (IL)-6, IL-11 and IL-27 are most explored in the context of TB. This review summarizes the differential roles of these cytokines in protection and immunopathology during Mtb infection and discusses potential therapeutic implementations with respect to the aforementioned approaches.

Non-genetic Heterogeneity of Macrophages in Diseases-A Medical Perspective

Macrophages are sessile immune cells with a high functional plasticity. Initially considered as a uniform population of phagocytic scavengers, it is now widely accepted that these cells also assume developmental and metabolic functions specific of their tissue of residence. Hence, the paradigm is shifting while our comprehension of macrophage heterogeneity improves. Accordingly, exploiting this intrinsic versatility appears more and more promising for the establishment of innovative therapeutic strategies. Nevertheless, identifying relevant therapeutic targets remains a considerable challenge. Herein, we discuss various features of macrophage heterogeneity in five main categories of human diseases: infectious, inflammatory, metabolic, age-related, and neoplastic disorders. We summarize the current understanding of how macrophage heterogeneity may impact the pathogenesis of these diseases and propose a comprehensive overview with the aim to help in establishing future macrophage-targeted therapies.

Cancer cells employ an evolutionarily conserved polyploidization program to resist therapy

Unusually large cancer cells with abnormal nuclei have been documented in the cancer literature since 1858. For more than 100 years, they have been generally disregarded as irreversibly senescent or dying cells, too morphologically misshapen and chromatin too disorganized to be functional. Cell enlargement, accompanied by whole genome doubling or more, is observed across organisms, often associated with mitigation strategies against environmental change, severe stress, or the lack of nutrients. Our comparison of the mechanisms for polyploidization in other organisms and non-transformed tissues suggest that cancer cells draw from a conserved program for their survival, utilizing whole genome doubling and pausing proliferation to survive stress. These polyaneuploid cancer cells (PACCs) are the source of therapeutic resistance, responsible for cancer recurrence and, ultimately, cancer lethality.

Epigenetic regulation of apoptosis via the PARK7 interactome in peripheral blood mononuclear cells donated by tuberculosis patients vs. healthy controls and the response to treatment: A systems biology approach

AIMS

The aims of our study were to determine for the first time differentially expressed genes (DEGs) and enriched molecular pathways involving the PARK7 interactome in PBMCs donated from tuberculosis patients.

METHODS

Data on a previously reconstructed PARK7 interactome (Vavougios et al., 2017) from datasets GDS4966 (Case-Control) and GDS4781 (Treatment Series) were retrieved from the Gene Expression Omnibus (GEO) repository. Gene Enrichment analysis was performed via the STRING algorithm and the GeneTrail2 software.

RESULTS

17 and 22 PARK7 interactores were determined as DEGs in the active TB vs HD and Treatment Series subset analyses, correspondingly, associated with significantly enriched pathways (FDR <0.05) involving p53 and PTEN mediated, stress responsive apoptosis regulation pathways. The treatment subset was characterized by the emergence of an additional layer of transcriptional regulation mediated by polycomb proteins among others, as well as TLR-mediated and cytokine survival signaling. Finally, the enrichment of a Parkinson's disease signature including PARK7 interactors was determined by its differential regulation both in the exploratory analyses (FDR = 0.024), as well as the confirmatory analyses (FDR = 1.81e^-243).

CONCLUSIONS

Our in silico analysis revealed for the first time the role of PARK7's interactome in regulating the epigenetics of the PBMC lifecycle and Mtb symbiosis.