Therapeutic host-directed strategies to improve outcome in tuberculosis

The role of family support in medication adherence and quality of life among tuberculosis patients: A scoping review

BACKGROUND

Tuberculosis (TB) remains one of the leading infectious diseases globally, causing high mortality rates. A significant factor contributing to this issue is nonadherence to treatment, which is influenced by family support and impacts the quality of life (QoL) of patients.

AIM

The purpose of this study was to describe the role of family support in enhancing medication adherence and improving QoL in individuals with TB.

METHODS

This study utilized a scoping review method to examine literature from the PubMed, Scopus, and EBSCO databases. The keywords used in the search included "social support OR online social support OR perceived social support OR family support" AND "Tuberculosis OR TB OR TBC" AND "medication adherence OR medication compliance OR drug adherence OR drug compliance OR adherence OR compliance OR lost to follow-up" AND "QoL OR HRQoL OR health-related QoL." The inclusion criteria were full-text articles in English, primary research studies, and publications from the last 10 years (2012-2022).

RESULTS

Thirteen articles met the inclusion criteria, with sample sizes ranging from 50 to 1342 respondents, predominantly using cross-sectional methods. The study found that family support is crucial in promoting medication adherence and positively influencing the QoL of TB patients. Family members provide emotional and practical support, including supervision of medication intake and encouragement of healthy habits. This support enhances patients' confidence, motivation, and overall treatment outcomes.

CONCLUSIONS

The findings underscore the indispensable role of family support in addressing the complex interplay between medication adherence and QoL for individuals with TB.

Drug repurposing against antibiotic resistant bacterial pathogens

The growing prevalence of MDR and XDR bacterial pathogens is posing a critical threat to global health. Traditional antibiotic development paths have encountered significant challenges and are drying up thus necessitating innovative approaches. Drug repurposing, which involves identifying new therapeutic applications for existing drugs, offers a promising alternative to combat resistant pathogens. By leveraging pre-existing safety and efficacy data, drug repurposing accelerates the development of new antimicrobial therapy regimes. This review explores the potential of repurposing existing FDA approved drugs against the ESKAPE and other clinically relevant bacterial pathogens and delves into the identification of suitable drug candidates, their mechanisms of action, and the potential for combination therapies. It also describes clinical trials and patent protection of repurposed drugs, offering perspectives on this evolving realm of therapeutic interventions against drug resistance.

Sirtuin inhibitors reduce intracellular growth of M. tuberculosis in human macrophages via modulation of host cell immunity

Host-directed therapies aiming to strengthen the body's immune system, represent an underexplored opportunity to improve treatment of tuberculosis (TB). We have previously shown in Mycobacterium tuberculosis (Mtb)-infection models and clinical trials that treatment with the histone deacetylase (HDAC) inhibitor, phenylbutyrate (PBA), can restore Mtb-induced impairment of antimicrobial responses and improve clinical outcomes in pulmonary TB. In this study, we evaluated the efficacy of different groups of HDAC inhibitors to reduce Mtb growth in human immune cells. A panel of 21 selected HDAC inhibitors with different specificities that are known to modulate infection or inflammation was tested using high-content live-cell imaging and analysis. Monocyte-derived macrophages or bulk peripheral blood cells (PBMCs) were infected with the green fluorescent protein (GFP)-expressing Mtb strains H37Ra or H37Rv and treated with HDAC inhibitors in the micromolar range in parallel with a combination of the first-line antibiotics, rifampicin, and isoniazid. Host cell viability in HDAC inhibitor treated cell cultures was monitored with Cytotox-red. Seven HDAC inhibitors were identified that reduced Mtb growth in macrophages > 45-75% compared to average 40% for PBA. The most effective compounds were inhibitors of the class III HDAC proteins, the sirtuins. While these compounds may exhibit their effects by improving macrophage function, one of the sirtuin inhibitors, tenovin, was also highly effective in extracellular killing of Mtb bacilli. Antimicrobial synergy testing using checkerboard assays revealed additive effects between selected sirtuin inhibitors and subinhibitory concentrations of rifampicin or isoniazid. A customized macrophage RNA array including 23 genes associated with cytokines, chemokines and inflammation, suggested that Mtb-infected macrophages are differentially modulated by the sirtuin inhibitors as compared to PBA. Altogether, these results demonstrated that sirtuin inhibitors may be further explored as promising host-directed compounds to support immune functions and reduce intracellular growth of Mtb in human cells.

Application of MIDD to accelerate the development of anti-infectives: Current status and future perspectives

This review examines the role of model-informed drug development (MIDD) in advancing antibacterial and antiviral drug development, with an emphasis on the inclusion of host system dynamics into modeling efforts. Amidst the growing challenges of multidrug resistance and diminishing market returns, innovative methodologies are crucial for continuous drug discovery and development. The MIDD approach, with its robust capacity to integrate diverse data types, offers a promising solution. In particular, the utilization of appropriate modeling and simulation techniques for better characterization and early assessment of drug resistance are discussed. The evolution of MIDD practices across different infectious disease fields is also summarized, and compared to advancements achieved in oncology. Moving forward, the application of MIDD should expand into host system dynamics as these considerations are critical for the development of "live drugs" (e.g. chimeric antigen receptor T cells or bacteriophages) to address issues like antibiotic resistance or latent viral infections.

Genome-wide screen of Mycobacterium tuberculosis-infected macrophages revealed GID/CTLH complex-mediated modulation of bacterial growth

The eukaryotic Glucose Induced Degradation/C-Terminal to LisH (GID/CTLH) complex is a highly conserved E3 ubiquitin ligase involved in a broad range of biological processes. However, a role of this complex in host anti-microbial defenses has not been described. We exploited Mycobacterium tuberculosis (Mtb) induced cytotoxicity in macrophages in a FACS based CRISPR genetic screen to identify host determinants of intracellular Mtb growth restriction. Our screen identified 5 (GID8, YPEL5, WDR26, UBE2H, MAEA) of the 12 predicted members of the GID/CTLH complex as determinants of intracellular growth of both Mtb and Salmonella serovar Typhimurium. We show that the anti-microbial properties of the GID/CTLH complex knockout macrophages are mediated by enhanced GABAergic signaling, activated AMPK, increased autophagic flux and resistance to Mtb induced necrotic cell death. Meanwhile, Mtb isolated from GID/CTLH knockout macrophages are nutritionally starved and oxidatively stressed. Our study identifies the GID/CTLH complex activity as broadly suppressive of host anti-microbial responses against intracellular bacterial infections.

Predicting Treatment Outcomes in Patients with Drug-Resistant Tuberculosis and Human Immunodeficiency Virus Coinfection, Using Supervised Machine Learning Algorithm

Drug-resistant tuberculosis (DR-TB) and HIV coinfection present a conundrum to public health globally and the achievement of the global END TB strategy in 2035. A descriptive, retrospective review of medical records of patients, who were diagnosed with DR-TB and received treatment, was conducted. Student's t-test was performed to assess differences between two means and ANOVA between groups. The Chi-square test with or without trend or Fischer's exact test was used to test the degree of association of categorical variables. Logistic regression was used to determine predictors of DR-TB treatment outcomes. A decision tree classifier, which is a supervised machine learning algorithm, was also used. Python version 3.8. and R version 4.1.1 software were used for data analysis. A p-value of 0.05 with a 95% confidence interval (CI) was used to determine statistical significance. A total of 456 DR-TB patients were included in the study, with more male patients (n = 256, 56.1%) than female patients (n = 200, 43.9%). The overall treatment success rate was 61.4%. There was a significant decrease in the % of patients cured during the COVID-19 pandemic compared to the pre-pandemic period. Our findings showed that machine learning can be used to predict TB patients' treatment outcomes.

Actionable mechanisms of drug tolerance and resistance in Mycobacterium tuberculosis

The emergence of antimicrobial resistance (AMR) across bacterial pathogens presents a serious threat to global health. This threat is further exacerbated in tuberculosis (TB), mainly due to a protracted treatment regimen involving a combination of drugs. A diversity of factors contributes to the emergence of drug resistance in TB, which is caused by the pathogen Mycobacterium tuberculosis (Mtb). While the traditional genetic mutation-driven drug resistance mechanisms operate in Mtb, there are also several additional unique features of drug resistance in this pathogen. Research in the past decade has enriched our understanding of such unconventional factors as efflux pumps, bacterial heterogeneity, metabolic states, and host microenvironment. Given that the discovery of new antibiotics is outpaced by the emergence of drug resistance patterns displayed by the pathogen, newer strategies for combating drug resistance are desperately needed. In the context of TB, such approaches include targeting the efflux capability of the pathogen, modulating the host environment to prevent bacterial drug tolerance, and activating the host anti-mycobacterial pathways. In this review, we discuss the traditional mechanisms of drug resistance in Mtb, newer understandings and the shaping of a set of unconventional approaches to target both the emergence and treatment of drug resistance in TB.

Targeting CCRL2 enhances therapeutic outcomes in a tuberculosis mouse model

Tuberculosis (TB) remains among the leading infectious causes of death. Due to the limited number of antimicrobials in the TB drug discovery pipeline, interest has developed in host-directed approaches to improve TB treatment outcomes. C-C motif chemokine-like receptor 2 (CCRL2) is a unique seven-transmembrane domain receptor that is upregulated by inflammatory signals and mediates leucocyte migration. However, little is known about its role in the setting of TB infection. Here, we show that Mycobacterium tuberculosis (Mtb) infection increases CCRL2 protein expression in macrophages and in mouse lungs. To target selectively CCRL2-expressing cells in vivo, we developed a novel mouse anti-CCRL2 antibody-drug conjugate (ADC) linked with the cytotoxic drug SG3249. We tested its adjunctive therapeutic efficacy against TB when combined with the first-line regimen for drug-susceptible TB (isoniazid, rifampin, pyrazinamide, ethambutol; RHZE). The anti-CCRL2 ADC treatment potentiated RHZE efficacy in Mtb-infected mice and decreased gross lung inflammation. CCRL2 expression in lung dendritic cells and alveolar macrophages was lower in mice receiving anti-CCRL2 ADC treatment + RHZE compared to those receiving RHZE alone or the control group, although the total innate cell populations did not differ across treatment groups. Interestingly, neutrophils were completely absent in the anti-CCRL2 ADC treatment + RHZE group, unlike in the other treatment groups. IFN-γ+ and IL17-Α+ T-cell responses, which are associated with optimal TB control, were also elevated in the anti-CCRL2 ADC treatment + RHZE group. Collectively, our findings suggest that CCRL2-targeting approaches may improve TB treatment outcomes, possibly through selective killing of Mtb-infected innate immune cells.

Adjunctive Pascolizumab in Rifampicin-Susceptible Pulmonary Tuberculosis: Proof-of-Concept, Partially-Randomized, Double-Blind, Placebo-Controlled, Dose-Escalation Trial

BACKGROUND

Interleukin 4 (IL-4), increased in tuberculosis infection, may impair bacterial killing. Blocking IL-4 confers benefit in animal models. We evaluated safety and efficacy of pascolizumab (humanized anti-IL-4 monoclonal antibody) as adjunctive tuberculosis treatment.

METHODS

Participants with rifampicin-susceptible pulmonary tuberculosis received a single intravenous infusion of pascolizumab or placebo, and standard 6-month tuberculosis treatment. Pascolizumab dose increased in successive cohorts: (1) nonrandomized 0.05 mg/kg (n = 4); (2) nonrandomized 0.5 mg/kg (n = 4); (3) randomized 2.5 mg/kg (n = 9) or placebo (n = 3); and (4) randomized 10 mg/kg (n = 9) or placebo (n = 3). Coprimary safety outcome was study-drug-related grade 4 or serious adverse event (G4/SAE) in all cohorts (1-4). Coprimary efficacy outcome was week 8 sputum culture time-to-positivity (TTP) in randomized cohorts (3-4) combined.

RESULTS

Pascolizumab levels exceeded IL-4 50% neutralizing dose for 8 weeks in 78%-100% of participants in cohorts 3-4. There were no study-drug-related G4/SAEs. Median week-8 TTP was 42 days in pascolizumab and placebo groups (P = .185). Rate of TTP increase was greater with pascolizumab (difference from placebo 0.011 log10 TTP/day; 95% Bayesian credible interval 0.006 to 0.015 log10 TTP/day).

CONCLUSIONS

There was no evidence to suggest blocking IL-4 was unsafe. Preliminary efficacy findings are consistent with animal models. This supports further investigation of adjunctive anti-IL-4 interventions for tuberculosis in larger phase 2 trials.

CLINICAL TRIALS REGISTRATION

NCT01638520.

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.

Breaking the Cycle: Matrix Metalloproteinase Inhibitors as an Alternative Approach in Managing Tuberculosis Pathogenesis and Progression

Mycobacterium tuberculosis (Mtb) has long posed a significant challenge to global public health, resulting in approximately 1.6 million deaths annually. Pulmonary tuberculosis (TB) instigated by Mtb is characterized by extensive lung tissue damage, leading to lesions and dissemination within the tissue matrix. Matrix metalloproteinases (MMPs) exhibit endopeptidase activity, contributing to inflammatory tissue damage and, consequently, morbidity and mortality in TB patients. MMP activities in TB are intricately regulated by various components, including cytokines, chemokines, cell receptors, and growth factors, through intracellular signaling pathways. Primarily, Mtb-infected macrophages induce MMP expression, disrupting the balance between MMPs and tissue inhibitors of metalloproteinases (TIMPs), thereby impairing extracellular matrix (ECM) deposition in the lungs. Recent research underscores the significance of immunomodulatory factors in MMP secretion and granuloma formation during Mtb pathogenesis. Several studies have investigated both the activation and inhibition of MMPs using endogenous MMP inhibitors (i.e., TIMPs) and synthetic inhibitors. However, despite their promising pharmacological potential, few MMP inhibitors have been explored for TB treatment as host-directed therapy. Scientists are exploring novel strategies to enhance TB therapeutic regimens by suppressing MMP activity to mitigate Mtb-associated matrix destruction and reduce TB induced lung inflammation. These strategies include the use of MMP inhibitor molecules alone or in combination with anti-TB drugs. Additionally, there is growing interest in developing novel formulations containing MMP inhibitors or MMP-responsive drug delivery systems to suppress MMPs and release drugs at specific target sites. This review summarizes MMPs' expression and regulation in TB, their role in immune response, and the potential of MMP inhibitors as effective therapeutic targets to alleviate TB immunopathology.

Neutrophil extracellular traps characterize caseating granulomas

Tuberculosis (TB) remains one of the top 10 causes of death worldwide and still poses a serious challenge to public health. Recent attention to neutrophils has uncovered unexplored areas demanding further investigation. Therefore, the aim of this study was to determine neutrophil activation and circulatory neutrophil extracellular trap (NET) formation in various types of TB. Sera from TB patients (n = 91) and healthy controls (NHD; n = 38) were analyzed for NE-DNA and MPO-DNA complexes, cell-free DNA (cfDNA), and protease activity (elastase). We show that these NET parameters were increased in TB sera. Importantly, NET formation and NE activity were elevated in TB patients with extensive tissue damage when compared to those with minor damage and in patients with relapse, compared to new cases. We discuss the importance of balancing NET formation to prevent tissue damage or even relapse and argue to analyze circulating NET parameters to monitor the risk of disease relapse. To investigate the tissues for NETs and to find the source of the circulating NET degradation products, we collected sections of granulomas in lung and lymph node biopsies. Samples from other diseases with granulomas, including sarcoidosis (SARC) and apical periodontitis (AP), served as controls. Whereas NET formation characterizes the caseating granulomas, both caseating and non-caseating granulomas harbor DNA with unusual conformation. As TB is associated with hypercoagulation and thromboembolism, we further imaged the pulmonary vessels of TB patients and detected vascular occlusions with neutrophil aggregates. This highlights the dual role of neutrophils in the pathology of TB.

Inhibition of leukotriene-B4 signalling-mediated host response to tuberculosis is a potential mode of adjunctive host-directed therapy

Treatment of tuberculosis (TB) is faced with several challenges including the long treatment duration, drug toxicity and tissue pathology. Host-directed therapy provides promising avenues to find compounds for adjunctively assisting antimycobacterials in the TB treatment regimen, by promoting pathogen eradication or limiting tissue destruction. Eicosanoids are a class of lipid molecules that are potent mediators of inflammation and have been implicated in aspects of the host response against TB. Here, we have explored the blood transcriptome of pulmonary TB patients to understand the activity of leukotriene B4, a pro-inflammatory eicosanoid. Our study shows a significant upregulation in the leukotriene B4 signalling pathway in active TB patients, which is reversed with TB treatment. We have further utilized our in-house network analysis algorithm, ResponseNet, to identify potential downstream signal effectors of leukotriene B4 in TB patients including STAT1/2 and NADPH oxidase at a systemic as well as local level, followed by experimental validation of the same. Finally, we show the potential of inhibiting leukotriene B4 signalling as a mode of adjunctive host-directed therapy against TB. This study provides a new mode of TB treatment along with mechanistic insights which can be further explored in pre-clinical trials.

The advances in adjuvant therapy for tuberculosis with immunoregulatory compounds

Tuberculosis (TB) is a chronic bacterial disease, as well as a complex immune disease. The occurrence, development, and prognosis of TB are not only related to the pathogenicity of Mycobacterium tuberculosis (Mtb), but also related to the patient's own immune state. The research and development of immunotherapy drugs can effectively regulate the body's anti-TB immune responses, inhibit or eliminate Mtb, alleviate pathological damage, and facilitate rehabilitation. This paper reviews the research progress of immunotherapeutic compounds for TB, including immunoregulatory compounds and repurposing drugs, and points out the existing problems and future research directions, which lays the foundation for studying new agents for host-directed therapies of TB.

Host stress drives tolerance and persistence: The bane of anti-microbial therapeutics

Antibiotic resistance, typically associated with genetic changes within a bacterial population, is a frequent contributor to antibiotic treatment failures. Antibiotic persistence and tolerance, which we collectively term recalcitrance, represent transient phenotypic changes in the bacterial population that prolong survival in the presence of typically lethal concentrations of antibiotics. Antibiotic recalcitrance is challenging to detect and investigate-traditionally studied under in vitro conditions, our understanding during infection and its contribution to antibiotic failure is limited. Recently, significant progress has been made in the study of antibiotic-recalcitrant populations in pathogenic species, including Mycobacterium tuberculosis, Staphylococcus aureus, Salmonella enterica, and Yersiniae, in the context of the host environment. Despite the diversity of these pathogens and infection models, shared signals and responses promote recalcitrance, and common features and vulnerabilities of persisters and tolerant bacteria have emerged. These will be discussed here, along with progress toward developing therapeutic interventions to better treat recalcitrant pathogens.

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.

Combating antimicrobial resistance in malaria, HIV and tuberculosis

Antimicrobial resistance poses a significant threat to the sustainability of effective treatments against the three most prevalent infectious diseases: malaria, human immunodeficiency virus (HIV) infection and tuberculosis. Therefore, there is an urgent need to develop novel drugs and treatment protocols capable of reducing the emergence of resistance and combating it when it does occur. In this Review, we present an overview of the status and underlying molecular mechanisms of drug resistance in these three diseases. We also discuss current strategies to address resistance during the research and development of next-generation therapies. These strategies vary depending on the infectious agent and the array of resistance mechanisms involved. Furthermore, we explore the potential for cross-fertilization of knowledge and technology among these diseases to create innovative approaches for minimizing drug resistance and advancing the discovery and development of new anti-infective treatments. In conclusion, we advocate for the implementation of well-defined strategies to effectively mitigate and manage resistance in all interventions against infectious diseases.

Adjunctive administration of parabiotic Lactobacillus sakei CVL-001 ameliorates drug-induced toxicity and pulmonary inflammation during antibiotic treatment for tuberculosis

Tuberculosis (TB) treatment requires a long therapeutic duration and induces adverse effects such as hepatotoxicity, causing discontinuation of treatment. Reduced adherence to TB medications elevates the risk of recurrence and the development of drug resistance. Additionally, severe cavitary TB with a high burden of Mycobacterium tuberculosis (Mtb) and inflammation-mediated tissue damage may need an extended treatment duration, resulting in a higher tendency of drug-induced toxicity. We previously reported that the administration of Lactobacillus sakei CVL-001 (L. sakei CVL-001) regulates inflammation and improves mucosal barrier function in a murine colitis model. Since accumulating evidence has reported the functional roles of probiotics in drug-induced liver injury and pulmonary inflammation, we employed a parabiotic form of the L. sakei CVL-001 to investigate whether this supplement may provide beneficial effects on the reduction in drug-induced liver damage and pulmonary inflammation during chemotherapy. Intriguingly, L. sakei CVL-001 administration slightly reduced Mtb burden without affecting lung inflammation and weight loss in both Mtb-resistant and -susceptible mice. Moreover, L. sakei CVL-001 decreased T cell-mediated inflammatory responses and increased regulatory T cells along with an elevated antigen-specific IL-10 production, suggesting that this parabiotic may restrain excessive inflammation during antibiotic treatment. Furthermore, the parabiotic intervention significantly reduced levels of alanine aminotransferase, an indicator of hepatotoxicity, and cell death in liver tissues. Collectively, our data suggest that L. sakei CVL-001 administration has the potential to be an adjunctive therapy by reducing pulmonary inflammation and liver damage during anti-TB drug treatment and may benefit adherence to TB medication in lengthy treatment.

Genome-wide screen of Mycobacterium tuberculosis- infected macrophages identified the GID/CTLH complex as a determinant of intracellular bacterial growth

The eukaryotic GID/CTLH complex is a highly conserved E3 ubiquitin ligase involved in a broad range of biological processes. However, a role of this complex in host antimicrobial defenses has not been described. We exploited Mycobacterium tuberculosis ( Mtb ) induced cytotoxicity in macrophages in a FACS based CRISPR genetic screen to identify host determinants of intracellular Mtb growth restriction. Our screen identified 5 ( GID8 , YPEL5 , WDR26 , UBE2H , MAEA ) of the 10 predicted members of the GID/CTLH complex as determinants of intracellular growth of both Mtb and Salmonella serovar Typhimurium. We show that the antimicrobial properties of the GID/CTLH complex knockdown macrophages are mediated by enhanced GABAergic signaling, activated AMPK, increased autophagic flux and resistance to cell death. Meanwhile, Mtb isolated from GID/CTLH knockdown macrophages are nutritionally starved and oxidatively stressed. Our study identifies the GID/CTLH complex activity as broadly suppressive of host antimicrobial responses against intracellular bacterial infections.

Graphical abstract

Potential of Neuroinflammation-Modulating Strategies in Tuberculous Meningitis: Targeting Microglia

Tuberculous meningitis (TBM) is the most severe complication of tuberculosis (TB) and is associated with high rates of disability and mortality. Mycobacterium tuberculosis (M. tb), the infectious agent of TB, disseminates from the respiratory epithelium, breaks through the blood-brain barrier, and establishes a primary infection in the meninges. Microglia are the core of the immune network in the central nervous system (CNS) and interact with glial cells and neurons to fight against harmful pathogens and maintain homeostasis in the brain through pleiotropic functions. However, M. tb directly infects microglia and resides in them as the primary host for bacillus infections. Largely, microglial activation slows disease progression. The non-productive inflammatory response that initiates the secretion of pro-inflammatory cytokines and chemokines may be neurotoxic and aggravate tissue injuries based on damages caused by M. tb. Host-directed therapy (HDT) is an emerging strategy for modulating host immune responses against diverse diseases. Recent studies have shown that HDT can control neuroinflammation in TBM and act as an adjunct therapy to antibiotic treatment. In this review, we discuss the diverse roles of microglia in TBM and potential host-directed TB therapies that target microglia to treat TBM. We also discuss the limitations of applying each HDT and suggest a course of action for the near future.

4-(Benzyloxy)phenol-induced p53 exhibits antimycobacterial response triggering phagosome-lysosome fusion through ROS-dependent intracellular Ca2+ pathway in THP-1 cells

Drug-resistant tuberculosis (TB) outbreak has emerged as a global public health crisis. Therefore, new and innovative therapeutic options like host-directed therapies (HDTs) through novel modulators are urgently required to overcome the challenges associated with TB. In the present study, we have investigated the anti-mycobacterial effect of 4-(Benzyloxy)phenol. Cell-viability assay asserted that 50 μM of 4-(Benzyloxy)phenol was not cytotoxic to phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 (dTHP-1) cells. It was observed that 4-(Benzyloxy)phenol activates p53 expression by hindering its association with KDM1A. Increased ROS, intracellular Ca2+ and phagosome-lysosome fusion, were also observed upon 4-(Benzyloxy)phenol treatment. 4-(Benzyloxy)phenol mediated killing of intracellular mycobacteria was abrogated in the presence of specific inhibitors of ROS, Ca2+ and phagosome-lysosome fusion like NAC, BAPTA-AM, and W7, respectively. We further demonstrate that 4-(Benzyloxy)phenol mediated enhanced ROS production is mediated by acetylation of p53. Blocking of p53 acetylation by Pifithrin-α (PFT- α) enhanced intracellular mycobacterial growth by blocking the mycobactericidal effect of 4-(Benzyloxy)phenol. Altogether, the results showed that 4-(Benzyloxy)phenol executed its anti-mycobacterial effect by modulating p53-mediated ROS production to regulate phagosome-lysosome fusion through Ca2+ production.

Therapeutic developments for tuberculosis and nontuberculous mycobacterial lung disease

Tuberculosis (TB) drug discovery and development has undergone nothing short of a revolution over the past 20 years. Successful public-private partnerships and sustained funding have delivered a much-improved understanding of mycobacterial disease biology and pharmacology and a healthy pipeline that can tolerate inevitable attrition. Preclinical and clinical development has evolved from decade-old concepts to adaptive designs that permit rapid evaluation of regimens that might greatly shorten treatment duration over the next decade. But the past 20 years also saw the rise of a fatal and difficult-to-cure lung disease caused by nontuberculous mycobacteria (NTM), for which the drug development pipeline is nearly empty. Here, we discuss the similarities and differences between TB and NTM lung diseases, compare the preclinical and clinical advances, and identify major knowledge gaps and areas of cross-fertilization. We argue that applying paradigms and networks that have proved successful for TB, from basic research to clinical trials, will help to populate the pipeline and accelerate curative regimen development for NTM disease.

HIV–A prognostic factor of tuberculous meningitis: A retrospective cohort study among adults in peninsular Malaysia

<b>Background:</b> Tuberculous meningitis is a major public health issue, despite showing low incidence, tuberculous meningitis causes substantial mortality. For better clinical management, identification of prognostic factors is crucial to reduce health risk of Malaysian society. Therefore, the aim of this study was to determine the prognostic factors of adult tuberculous meningitis in peninsular Malaysia.<br /> <b>Materials &amp; methods:</b> Initially, a retrospective cohort study and one-year of follow-up period was carried out. In addition, a total of 217 adult tuberculous meningitis patients treated or had follow-up in four tertiary hospitals in peninsular Malaysia were recruited. Cox proportional hazards regression was employed to perform multivariable analysis.<br /> <b>Results:</b> The overall survival probability of adult tuberculous meningitis was 36.8% with median survival time 244 days. Significant prognostic factors were Glasgow coma scale score (aHR=0.71, 95% CI=0.65, 0.76; p&lt;0.001), HIV status (aHR=1.94, 95% confidence interval [CI]=1.19, 3.15; p=0.008), headache (aHR=0.48, 95% CI=0.31, 0.76; p=0.002) and meningeal enhancement (aHR=0.47, 95% CI=0.30, 0.74; p=0.001), nausea (aHR=2.21, 95% CI=1.33, 3.66; p=0.002), and vomit (aHR=0.58, 95% CI=0.36, 0.93; p=0.023).<br /> <b>Conclusions:</b> Evidently, the survival of among adults with tuberculous meningitis was low. Since HIV positive has a significant influence in mortality; early screening, diagnosis, and prompt treatment in this subgroup of patients play a key role in survival.

Homodimeric Granzyme A Opsonizes Mycobacterium tuberculosis and Inhibits Its Intracellular Growth in Human Monocytes via Toll-Like Receptor 4 and CD14

Mycobacterium tuberculosis (Mtb)-specific γ9δ2 T cells secrete granzyme A (GzmA) protective against intracellular Mtb growth. However, GzmA-enzymatic activity is unnecessary for pathogen inhibition, and the mechanisms of GzmA-mediated protection remain unknown. We show that GzmA homodimerization is essential for opsonization of mycobacteria, altered uptake into human monocytes, and subsequent pathogen clearance within the phagolysosome. Although monomeric and homodimeric GzmA bind mycobacteria, only homodimers also bind cluster of differentiation 14 (CD14) and Toll-like receptor 4 (TLR4). Without access to surface-expressed CD14 and TLR4, GzmA fails to inhibit intracellular Mtb. Upregulation of Rab11FIP1 was associated with inhibitory activity. Furthermore, GzmA colocalized with and was regulated by protein disulfide isomerase AI (PDIA1), which cleaves GzmA homodimers into monomers and prevents Mtb inhibitory activity. These studies identify a previously unrecognized role for homodimeric GzmA structure in opsonization, phagocytosis, and elimination of Mtb in human monocytes, and they highlight PDIA1 as a potential host-directed therapy for prevention and treatment of tuberculosis, a major human disease.

The Cyclooxygenase 2 Inhibitor Etoricoxib as Adjunctive Therapy in Tuberculosis Impairs Macrophage Control of Mycobacterial Growth

BACKGROUND

Current tuberculosis treatment regimens could be improved by adjunct host-directed therapies (HDT) targeting host responses. We investigated the antimycobacterial capacity of macrophages from patients with tuberculosis in a phase 1/2 randomized clinical trial (TBCOX2) of the cyclooxygenase-2 inhibitor etoricoxib.

METHODS

Peripheral blood mononuclear cells from 15 patients with tuberculosis treated with adjunctive COX-2i and 18 controls (standard therapy) were collected on day 56 after treatment initiation. The ex vivo capacity of macrophages to control mycobacterial infection was assessed by challenge with Mycobacterium avium, using an in vitro culture model. Macrophage inflammatory responses were analyzed by gene expression signatures, and concentrations of cytokines were analyzed in supernatants by multiplex.

RESULTS

Macrophages from patients receiving adjunctive COX-2i treatment had higher M. avium loads than controls after 6 days, suggesting an impaired capacity to control mycobacterial infection compared to macrophages from the control group. Macrophages from the COX-2i group had lower gene expression of TNF, IL-1B, CCL4, CXCL9, and CXCL10 and lowered production of cytokines IFN-β and S100A8/A9 than controls.

CONCLUSIONS

Our data suggest potential unfavorable effects with impaired macrophage capacity to control mycobacterial growth in patients with tuberculosis receiving COX-2i treatment. Larger clinical trials are required to analyze the safety of COX-2i as HDT in patients with tuberculosis.

CLINICAL TRIALS REGISTRATION

NCT02503839.

More Tailored Approaches to Tuberculosis Treatment and Prevention

Recent advances in the treatment of tuberculosis (TB) have led to improvements unprecedented in our lifetime. Decades of research in developing new drugs, especially for multidrug-resistant TB, have created not only multiple new antituberculous agents but also a new approach to development and treatment, with a focus on maximizing the benefit to the individual patient. Prevention of TB disease has also been improved and recognized as a critical component of global TB control. While the momentum is positive, it will take continued investment at all levels, especially training of new dedicated TB researchers and advocates around the world, to maintain this progress.

Mycobacterium tuberculosis PE_PGRS45 (Rv2615c) Promotes Recombinant Mycobacteria Intracellular Survival via Regulation of Innate Immunity, and Inhibition of Cell Apoptosis

Tuberculosis (TB), a bacterial infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), is a significant global public health problem. Mycobacterium tuberculosis expresses a unique family of PE_PGRS proteins that have been implicated in pathogenesis. Despite numerous studies, the functions of most PE_PGRS proteins in the pathogenesis of mycobacterium infections remain unclear. PE_PGRS45 (Rv2615c) is only found in pathogenic mycobacteria. In this study, we successfully constructed a recombinant Mycobacterium smegmatis (M. smegmatis) strain which heterologously expresses the PE_PGRS45 protein. We found that overexpression of this cell wall-associated protein enhanced bacterial viability under stress in vitro and cell survival in macrophages. MS_PE_PGRS45 decreased the secretion of pro-inflammatory cytokines such as IL-1β, IL-6, IL-12p40, and TNF-α. We also found that MS_PE_PGRS45 increased the expression of the anti-inflammatory cytokine IL-10 and altered macrophage-mediated immune responses. Furthermore, PE_PGRS45 enhanced the survival rate of M. smegmatis in macrophages by inhibiting cell apoptosis. Collectively, our findings show that PE_PGRS45 is a virulent factor actively involved in the interaction with the host macrophage.

An Update to Novel Therapeutic Options for Combating Tuberculosis: Challenges and Future Prospectives

Drug repurposing is an ongoing and clever strategy that is being developed to eradicate tuberculosis amid challenges, of which one of the major challenges is the resistance developed towards antibiotics used in standard directly observed treatment, short-course regimen. Surpassing the challenges in developing anti-tuberculous drugs, some novel host-directed therapies, repurposed drugs, and drugs with novel targets are being studied, and few are being approved too. After almost 4 decades since the approval of rifampicin as a potent drug for drugsusceptible tuberculosis, the first drug to be approved for drug-resistant tuberculosis is bedaquiline. Ever since the urge to drug discovery has been at a brisk as this milestone in tuberculosis treatment has provoked the hunt for novel targets in tuberculosis. Host-directed therapy and repurposed drugs are in trend as their pharmacological and toxicological properties have already been researched for some other diseases making the trial facile. This review discusses the remonstrance faced by researchers in developing a drug candidate with a novel target, the furtherance in tuberculosis research, novel anti-tuberculosis agents approved so far, and candidates on trial including the host-directed therapy, repurposed drug and drug combinations that may prove to be potential in treating tuberculosis soon, aiming to augment the awareness in this context to the imminent researchers.

Deciphering drug discovery and microbial pathogenesis research in tuberculosis during the two decades of postgenomic era using entity mining approach

We examined literature on Mycobacterium tuberculosis (Mtb) subsequent to its genome release, spanning years 1999-2020. We employed scientometric mapping, entity mining, visualization techniques, and PubMed and PubTator databases. Most popular keywords, most active research groups, and growth in quantity of publications were determined. By gathering annotations from the PubTator, we determined direction of research in the areas of drug hypersensitivity, drug resistance (AMR), and drug-related side effects. Additionally, we examined the patterns in research on Mtb metabolism and various forms of tuberculosis, including skin, brain, pulmonary, extrapulmonary, and latent tuberculosis. We discovered that 2011 had the highest annual growth rate of publications, at 19.94%. The USA leads the world in publications with 18,038, followed by China with 14,441, and India with 12,158 publications. Studies on isoniazid and rifampicin resistance showed an enormous increase. Non-tuberculous mycobacteria also been the subject of more research in effort to better understand Mtb physiology and as model organisms. Researchers also looked at co-infections like leprosy, hepatitis, plasmodium, HIV, and other opportunistic infections. Host perspectives like immune response, hypoxia, and reactive oxygen species, as well as comorbidities like arthritis, cancer, diabetes, and kidney disease etc. were also looked at. Symptomatic aspects like fever, coughing, and weight loss were also investigated. Vitamin D has gained popularity as a supplement during illness recovery, however, the interest of researchers declined off late. We delineated dominant researchers, journals, institutions, and leading nations globally, which is crucial for aligning ongoing and evolving landscape of TB research efforts. Recognising the dominant patterns offers important information about the areas of focus for current research, allowing biomedical scientists, clinicians, and organizations to strategically coordinate their efforts with the changing priorities in the field of tuberculosis research.

Histone deacetylase (HDAC) inhibitors- based drugs are effective to control Mycobacterium tuberculosis infection and promote the sensibility for rifampicin in MDR strain

BACKGROUND

Tuberculosis (TB) is a major public health problem, which has been aggravated by the alarming growth of drug-resistant tuberculosis. Therefore, the development of a safer and more effective treatment is needed.

OBJECTIVES

The aim of this work was repositioning and evaluate histone deacetylases (HDAC) inhibitors- based drugs with potential antimycobacterial activity.

METHODS

Using an in silico pharmacological repositioning strategy, three molecules that bind to the catalytic site of histone deacetylase were selected. Pneumocytes type II and macrophages were infected with Mycobacterium tuberculosis and treated with pre-selected HDAC inhibitors (HDACi). Subsequently, the ability of each of these molecules to directly promote the elimination of M. tuberculosis was evaluated by colony-forming unit (CFU)/mL. We assessed the expression of antimicrobial peptides and respiratory burst using reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

FINDINGS

Aminoacetanilide (ACE), N-Boc-1,2-phenylenediamine (N-BOC), 1,3-Diphenylurea (DFU), reduce bacillary loads in macrophages and increase the production of β-defensin-2, LL-37, superoxide dismutase (SOD) 3 and inducible nitric oxide synthase (iNOS). While only the use of ACE in type II pneumocytes decreases the bacterial load through increasing LL-37 expression. Furthermore, the use of ACE and rifampicin inhibited the survival of intracellular multi-drug resistance M. tuberculosis.

MAIN CONCLUSIONS

Our data support the usefulness of in silico approaches for drug repositioning to provide a potential adjunctive therapy for TB.

Tuberculosis Severity Predictive Model Using Mtb Variants and Serum Biomarkers in a Colombian Cohort of APTB Patients

Currently, tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis (Mtb) that primarily affects the lungs. The severity of active pulmonary TB (APTB) is an important determinant of transmission, morbidity, mortality, disease experience, and treatment outcomes. Several publications have shown a high prevalence of disabling complications in individuals who have had severe APTB. Furthermore, certain strains of Mtb were associated with more severe disease outcomes. The use of biomarkers to predict severe APTB patients who are candidates for host-directed therapies, due to the high risk of developing post-tuberculous lung disease (PTLD), has not yet been implemented in the management of TB patients. We followed 108 individuals with APTB for 6 months using clinical tools, flow cytometry, and whole-genome sequencing (WGS). The median age of the study population was 26.5 years, and the frequency of women was 53.7%. In this study, we aimed to identify biomarkers that could help us to recognize individuals with APTB and improve our understanding of the immunopathology in these individuals. In this study, we conducted a follow-up on the treatment progress of 121 cases of APTB. The follow-up process commenced at the time of diagnosis (T0), continued with a control visit at 2 months (T2), and culminated in an exit appointment at 6 months following the completion of medical treatment (T6). People classified with severe APTB showed significantly higher levels of IL-6 (14.7 pg/mL; p < 0.05) compared to those with mild APTB (7.7 pg/mL) at T0. The AUCs for the ROC curves and the Matthews correlation coefficient values (MCC) demonstrate correlations ranging from moderate to very strong. We conducted WGS on 88 clinical isolates of Mtb, and our analysis revealed a total of 325 genes with insertions and deletions (Indels) within their coding regions when compared to the Mtb H37Rv reference genome. The pattern of association was found between serum levels of CHIT1 and the presence of Indels in Mtb isolates from patients with severe APTB. A key finding in our study was the high levels of CHIT1 in severe APTB patients. We identified a biomarker profile (IL-6, IFN-γ, IL-33, and CHIT1) that allows us to identify individuals with severe APTB, as well as the identification of a panel of polymorphisms (125) in clinical isolates of Mtb from individuals with severe APTB. Integrating these findings into a predictive model of severity would show promise for the management of APTB patients in the future, to guide host-directed therapy and reduce the prevalence of PTLD.

Dual Inhibition of Mycobacterium tuberculosis and the Host TGFBR1 by an Anilinoquinazoline

Tuberculosis (TB) control is complicated by the emergence of drug resistance. Promising strategies to prevent drug resistance are the targeting of nonreplicating, drug-tolerant bacterial populations and targeting of the host, but inhibitors and targets for either are still rare. In a cell-based screen of ATP-competitive inhibitors, we identified compounds with in vitro activity against replicating Mycobacterium tuberculosis (Mtb), and an anilinoquinazoline (AQA) that also had potent activity against nonreplicating and persistent Mtb. AQA was originally developed to inhibit human transforming growth factor receptor 1 (TGFBR1), a host kinase that is predicted to have host-adverse effects during Mtb infection. The structure-activity relationship of this dually active compound identified the pyridyl-6-methyl group as being required for potent Mtb inhibition but a liability for P450 metabolism. Pyrrolopyrimidine (43) emerged as the optimal compound that balanced micromolar inhibition of nonreplicating Mtb and TGFBR1 while also demonstrating improved metabolic stability and pharmacokinetic profiles.

Functionalizing Dendrimers for Targeted Delivery of Bioactive Molecules to Macrophages: A Potential Treatment for Mycobacterium tuberculosis Infection-A Review

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis that replicates inside human alveolar macrophages. This disease causes significant morbidity and mortality throughout the world. According to the World Health Organization 1.4 million people died of this disease in 2021. This indicates that despite the progress of modern medicine, improvements in diagnostics, and the development of drug susceptibility tests, TB remains a global threat to public health. In this sense, host-directed therapy may provide a new approach to the cure of TB, and the expression of miRNAs has been correlated with a change in the concentration of various inflammatory mediators whose concentrations are responsible for the pathophysiology of M. tuberculosis infection. Thus, the administration of miRNAs may help to modulate the immune response of organisms. However, direct administration of miRNAs, without adequate encapsulation, exposes nucleic acids to the activity of cytosolic nucleases, limiting their application. Dendrimers are a family of highly branched molecules with a well-defined architecture and a branched conformation which gives rise to cavities that facilitate physical immobilization, and functional groups that allow chemical interaction with molecules of interest. Additionally, dendrimers can be easily functionalized to target different cells, macrophages among them. In this sense, various studies have proposed the use of different cell receptors as target molecules to aim dendrimers at macrophages and thus release drugs or nucleic acids in the cell of interest. Based on the considerations, the primary objective of this review is to comprehensively explore the potential of functionalized dendrimers as delivery vectors for miRNAs and other therapeutic agents into macrophages. This work aims to provide insights into the use of functionalized dendrimers as an innovative approach for TB treatment, focusing on their ability to target and deliver therapeutic cargo to macrophages.

High and Low Levels of ABCB1 Expression Are Associated with Two Distinct Gene Signatures in Lung Tissue of Pulmonary TB Patients with High Inflammation Activity

P-glycoprotein (encoded by the ABCB1 gene) has a dual role in regulating inflammation and reducing chemotherapy efficacy in various diseases, but there are few studies focused on pulmonary TB patients. In this study, our objective was to identify a list of genes that correlate with high and low levels of ABCB1 gene expression in the lungs of pulmonary TB patients with different activity of chronic granulomatous inflammation. We compared gene expression in two groups of samples (with moderate and high activity of tuberculomas) to identify their characteristic gene signatures. Gene expression levels were determined using quantitative PCR in samples of perifocal area of granulomas, which were obtained from 65 patients after surgical intervention. Subsequently, two distinct gene signatures associated with high inflammation activity were identified. The first signature demonstrated increased expression of HIF1a, TGM2, IL6, SOCS3, and STAT3, which correlated with high ABCB1 expression. The second signature was characterized by high expression of TNFa and CD163 and low expression of ABCB1. These results provide insight into various inflammatory mechanisms and association with P-gp gene expression in lung tissue of pulmonary TB patients and will be useful in the development of a host-directed therapy approach to improving the effectiveness of anti-TB treatment.

Harnessing host-pathogen interactions for innovative drug discovery and host-directed therapeutics to tackle tuberculosis

Tuberculosis (TB) is a highly contagious bacterial infection caused by Mycobacterium tuberculosis (Mtb), which has been ranked as the second leading cause of death worldwide from a single infectious agent. As an intracellular pathogen, Mtb has well adapted to the phagocytic host microenvironment, influencing diverse host processes such as gene expression, trafficking, metabolism, and signaling pathways of the host to its advantage. These responses are the result of dynamic interactions of the bacteria with the host cell signaling pathways, whereby the bacteria attenuate the host cellular processes for their survival. Specific host genes and the mechanisms involved in the entry and subsequent stabilization of M. tuberculosis intracellularly have been identified in various genetic and chemical screens recently. The present understanding of the co-evolution of Mtb and macrophage system presented us the new possibilities for exploring host-directed therapeutics (HDT). Here, we discuss the host-pathogen interaction for Mtb, including the pathways adapted by Mtb to escape immunity. The review sheds light on different host-directed therapies (HDTs) such as repurposed drugs and vitamins, along with their targets such as granuloma, autophagy, extracellular matrix, lipids, and cytokines, among others. The article also examines the available clinical data on these drug molecules. In conclusion, the review presents a perspective on the current knowledge in the field of HDTs and the need for additional research to overcome the challenges associated HDTs.

Impaired resolution of blood transcriptomes through tuberculosis treatment with diabetes comorbidity

BACKGROUND

People with diabetes are more likely to develop tuberculosis (TB) and to have poor TB-treatment outcomes than those without. We previously showed that blood transcriptomes in people with TB-diabetes (TB-DM) co-morbidity have excessive inflammatory and reduced interferon responses at diagnosis. It is unknown whether this persists through treatment and contributes to the adverse outcomes.

METHODS

Pulmonary TB patients recruited in South Africa, Indonesia and Romania were classified as having TB-DM, TB with prediabetes, TB-related hyperglycaemia or TB-only, based on glycated haemoglobin concentration at TB diagnosis and after 6 months of TB treatment. Gene expression in blood at diagnosis and intervals throughout treatment was measured by unbiased RNA-Seq and targeted Multiplex Ligation-dependent Probe Amplification. Transcriptomic data were analysed by longitudinal mixed-model regression to identify whether genes were differentially expressed between clinical groups through time. Predictive models of TB-treatment response across groups were developed and cross-tested.

RESULTS

Gene expression differed between TB and TB-DM patients at diagnosis and was modulated by TB treatment in all clinical groups but to different extents, such that differences remained in TB-DM relative to TB-only throughout. Expression of some genes increased through TB treatment, whereas others decreased: some were persistently more highly expressed in TB-DM and others in TB-only patients. Genes involved in innate immune responses, anti-microbial immunity and inflammation were significantly upregulated in people with TB-DM throughout treatment. The overall pattern of change was similar across clinical groups irrespective of diabetes status, permitting models predictive of TB treatment to be developed.

CONCLUSIONS

Exacerbated transcriptome changes in TB-DM take longer to resolve during TB treatment, meaning they remain different from those in uncomplicated TB after treatment completion. This may indicate a prolonged inflammatory response in TB-DM, requiring prolonged treatment or host-directed therapy for complete cure. Development of transcriptome-based biomarker signatures of TB-treatment response should include people with diabetes for use across populations.

Ac-93,253 inhibits intracellular growth of mycobacteria in human macrophages by inducing apoptosis in mitochondrial-dependent manner

Recent studies suggest that apoptosis in macrophages plays a significant role in host defence against intracellular pathogens like viruses, fungi, protozoan, and bacteria, including Mycobacterium tuberculosis (M. tb). It is still unclear if micromolecules inducing apoptosis could be an attractive approach to combat the intracellular burden of M. tb. Hence, the present study has investigated the anti-mycobacterial effect of apoptosis mediated through phenotypic screening of micromolecules. Through MTT and trypan blue exclusion assay, 0.5 μM of Ac-93,253 was found to be non-cytotoxic even after 72 h of treatment in phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 (dTHP-1) cells. Significant regulation in the expression of various pro-apoptotic genes like Bcl-2, Bax, and Bad and the cleaved caspase 3 was observed upon treatment with a non-cytotoxic dose of Ac-93,253. Ac-93,253 treatment also leads to DNA fragmentation and increased phosphatidylserine accumulation in the plasma membrane's outer leaflet. Further, Ac-93,253 also effectively reduced the growth of mycobacteria in infected macrophages, Z-VAD-FMK a broad-range apoptosis inhibitor significantly brought back the mycobacterial growth in Ac-93,253 treated macrophages. These findings suggest apoptosis may be the probable effector response through which Ac-93,253 manifests its anti-mycobacterial property.

Development of prognostic scoring system for predicting 1-year mortality among pulmonary tuberculosis patients in South India

BACKGROUND

Development of a prediction model using baseline characteristics of tuberculosis (TB) patients at the time of diagnosis will aid us in early identification of the high-risk groups and devise pertinent strategies accordingly. Hence, we did this study to develop a prognostic-scoring model for predicting the death among newly diagnosed drug sensitive pulmonary TB patients in South India.

METHODS

We undertook a longitudinal analysis of cohort data under the Regional Prospective Observational Research for Tuberculosis India consortium. Multivariable cox regression using the stepwise backward elimination procedure was used to select variables for the model building and the nomogram-scoring system was developed with the final selected model.

RESULTS

In total, 54 (4.6%) out of the 1181 patients had died during the 1-year follow-up period. The TB mortality rate was 0.20 per 1000 person-days. Eight variables (age, gender, functional limitation, anemia, leukopenia, thrombocytopenia, diabetes, neutrophil-lymphocyte ratio) were selected and a nomogram was built using these variables. The discriminatory power was 0.81 (95% confidence interval: 0.75-0.86) and this model was well-calibrated. Decision curve analysis showed that the model is beneficial at a threshold probability ~15-65%.

CONCLUSIONS

This scoring system could help the clinicians and policy makers to devise targeted interventions and in turn reduce the TB mortality in India.

Effect of Low Doses of Dexamethasone on Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is the deadliest disease caused by a bacterial agent. Glucocorticoids (GCs) have a typical anti-inflammatory effect, but recently it has been shown that they can present proinflammatory activity, mainly by increasing molecules from innate immunity. In the current study, we evaluated the effect of low doses of dexamethasone on Mycobacterium tuberculosis in vivo and in vitro. We used an established mice model of progressing tuberculosis (TB) in the in vivo studies. Intratracheal or intranasal dexamethasone therapy administered with conventional antibiotics in the late stage of the disease decreased the lung bacilli load and lung pneumonia, and increased the survival of the animals. Finally, the treatment decreased the inflammatory response in the SNC and, therefore, sickness behavior and neurological abnormalities in the infected animals. In the in vitro experiments, we used a cell line of murine alveolar macrophages infected with Mtb. Low-dose dexamethasone treatment increased the clearance capacity of Mtb by MHS macrophages, MIP-1α, and TLR2 expression, decreased proinflammatory and anti-inflammatory cytokines, and induced apoptosis, a molecular process that contributes to the control of the mycobacteria. In conclusion, the administration of low doses of dexamethasone represents a promising adjuvant treatment for pulmonary TB.

Advances in immunomodulatory strategies for host-directed therapies in combating tuberculosis

Tuberculosis (TB) maintains its infamous status regarding its detrimental effect on global health, causing the highest mortality by a single infectious agent. The presence of resistance and immune compromising disease favours the disease in maintaining its footing in the health care burden despite various anti-TB drugs used to fight it. Main factors contributing to resistance and difficulty in treating disease include prolonged treatment duration (at least 6 months) and severe toxicity, which further leads to patient non-compliance, and thus a ripple effect leading to therapeutic non-efficacy. The efficacy of new regimens demonstrates that targeting host factors concomitantly with the Mycobacterium tuberculosis (M.tb) strain is urgently required. Due to the huge expenses and time required of up to 20 years for new drug research and development, drug repurposing may be the most economical, circumspective, and conveniently faster journey to embark on. Host-directed therapy (HDT) will dampen the burden of the disease by acting as an immunomodulator, allowing it to defend the body against antibiotic-resistant pathogens whilst minimizing the possibility of developing new resistance to susceptible drugs. Repurposed drugs in TB act as host-directed therapies, acclimatizing the host immune cell to the presence of TB, improving its antimicrobial activity and time taken to get rid of the disease, whilst minimizing inflammation and tissue damage. In this review, we, therefore, explore possible immunomodulatory targets, HDT immunomodulatory agents, and their ability to improve clinical outcomes whilst minimizing the risk of drug resistance, through various pathway targeting and treatment duration reduction.

IL-10 Modulation Increases Pyrazinamide's Antimycobacterial Efficacy against Mycobacterium tuberculosis Infection in Mice

Mechanisms to shorten the duration of tuberculosis (TB) treatment include new drug formulations or schedules and the development of host-directed therapies (HDTs) that better enable the host immune system to eliminate Mycobacterium tuberculosis. Previous studies have shown that pyrazinamide, a first-line antibiotic, can also modulate immune function, making it an attractive target for combinatorial HDT/antibiotic therapy, with the goal to accelerate clearance of M. tuberculosis. In this study, we assessed the value of anti-IL-10R1 as an HDT along with pyrazinamide and show that short-term anti-IL-10R1 blockade during pyrazinamide treatment enhanced the antimycobacterial efficacy of pyrazinamide, resulting in faster clearance of M. tuberculosis in mice. Furthermore, 45 d of pyrazinamide treatment in a functionally IL-10-deficient environment resulted in sterilizing clearance of M. tuberculosis. Our data suggest that short-term IL-10 blockade with standard TB drugs has the potential to improve clinical outcome by reducing the treatment duration.

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.

Beyond the Clinic: The Activation of Diverse Cellular and Humoral Factors Shapes the Immunological Status of Patients with Active Tuberculosis

Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis (TB), has killed nearly one billion people in the last two centuries. Nowadays, TB remains a major global health problem, ranking among the thirteen leading causes of death worldwide. Human TB infection spans different levels of stages: incipient, subclinical, latent and active TB, all of them with varying symptoms, microbiological characteristics, immune responses and pathologies profiles. After infection, Mtb interacts with diverse cells of both innate and adaptive immune compartments, playing a crucial role in the modulation and development of the pathology. Underlying TB clinical manifestations, individual immunological profiles can be identified in patients with active TB according to the strength of their immune responses to Mtb infection, defining diverse endotypes. Those different endotypes are regulated by a complex interaction of the patient's cellular metabolism, genetic background, epigenetics, and gene transcriptional regulation. Here, we review immunological categorizations of TB patients based on the activation of different cellular populations (both myeloid and lymphocytic subsets) and humoral mediators (such as cytokines and lipid mediators). The analysis of the participating factors that operate during active Mtb infection shaping the immunological status or immune endotypes of TB patients could contribute to the development of Host Directed Therapy.

Intranasal multivalent adenoviral-vectored vaccine protects against replicating and dormant M.tb in conventional and humanized mice

Viral-vectored vaccines are highly amenable for respiratory mucosal delivery as a means of inducing much-needed mucosal immunity at the point of pathogen entry. Unfortunately, current monovalent viral-vectored tuberculosis (TB) vaccine candidates have failed to demonstrate satisfactory clinical protective efficacy. As such, there is a need to develop next-generation viral-vectored TB vaccine strategies which incorporate both vaccine antigen design and delivery route. In this study, we have developed a trivalent chimpanzee adenoviral-vectored vaccine to provide protective immunity against pulmonary TB through targeting antigens linked to the three different growth phases (acute/chronic/dormancy) of Mycobacterium tuberculosis (M.tb) by expressing an acute replication-associated antigen, Ag85A, a chronically expressed virulence-associated antigen, TB10.4, and a dormancy/resuscitation-associated antigen, RpfB. Single-dose respiratory mucosal immunization with our trivalent vaccine induced robust, sustained tissue-resident multifunctional CD4⁺ and CD8⁺ T-cell responses within the lung tissues and airways, which were further quantitatively and qualitatively improved following boosting of subcutaneously BCG-primed hosts. Prophylactic and therapeutic immunization with this multivalent trivalent vaccine in conventional BALB/c mice provided significant protection against not only actively replicating M.tb bacilli but also dormant, non-replicating persisters. Importantly, when used as a booster, it also provided marked protection in the highly susceptible C3HeB/FeJ mice, and a single respiratory mucosal inoculation was capable of significant protection in a humanized mouse model. Our findings indicate the great potential of this next-generation TB vaccine strategy and support its further clinical development for both prophylactic and therapeutic applications.

Advancing personalized medicine for tuberculosis through the application of immune profiling

While early and precise diagnosis is the key to eliminating tuberculosis (TB), conventional methods using culture conversion or sputum smear microscopy have failed to meet demand. This is especially true in high-epidemic developing countries and during pandemic-associated social restrictions. Suboptimal biomarkers have restricted the improvement of TB management and eradication strategies. Therefore, the research and development of new affordable and accessible methods are required. Following the emergence of many high-throughput quantification TB studies, immunomics has the advantages of directly targeting responsive immune molecules and significantly simplifying workloads. In particular, immune profiling has been demonstrated to be a versatile tool that potentially unlocks many options for application in TB management. Herein, we review the current approaches for TB control with regard to the potentials and limitations of immunomics. Multiple directions are also proposed to hopefully unleash immunomics' potential in TB research, not least in revealing representative immune biomarkers to correctly diagnose TB. The immune profiles of patients can be valuable covariates for model-informed precision dosing-based treatment monitoring, prediction of outcome, and the optimal dose prediction of anti-TB drugs.

JFD, a Novel Natural Inhibitor of Keap1 Alkylation, Suppresses Intracellular Mycobacterium Tuberculosis Growth through Keap1/Nrf2/SOD2-Mediated ROS Accumulation

It is an effective strategy to treat tuberculosis by enhancing reactive oxygen species- (ROS-) mediated killing of Mycobacterium tuberculosis in macrophages, but there are no current therapeutic agents targeting this pathway. Honeysuckle has been used as the traditional medicine for tuberculosis treatment for 1500 years. Japoflavone D (JFD) is a novel biflavonoid isolated from Honeysuckle promoting ROS accumulation by Nrf2 pathway in hepatocarcinoma cells. However, its activity to kill M. tuberculosis in macrophages and molecular mechanism has not been reported. Our results showed that JFD enhances the M. tuberculosis elimination by boosting ROS levels in THP-1 cells. Moreover, the massive ROS accumulation activates p38 to induce apoptosis. Notably, the mechanism revealed that JFD suppresses the nuclear transport of Nrf2, thereby inhibiting SOD2 transcription, leading to a large ROS accumulation. Further studies showed that JFD disrupts the Keap1 alkylation at specific residues Cys14, Cys257, and Cys319, which is crucial for Nrf2 activation, thereby interrupts the nuclear transport of Nrf2. In pharmacokinetic study, JFD can stay as the prototype for 24 h in mice and can be excreted in feces without any toxicity. Our data reveal for the first time that a novel biflavonoid JFD as a potent inhibitor of Keap1 alkylation can suppress the nuclear transport of Nrf2. And it is the first research of the inhibitor of Keap1 alkylation. Furthermore, JFD robustly promotes M. tuberculosis elimination from macrophages by inhibiting Keap1/Nrf2/SOD2 pathway, resulting in the ROS accumulation. This work identified Keap1 alkylation as a new drug target for tuberculosis and provides a preliminary basis for the development of antituberculosis lead compounds based on JFD.

Host-directed immunotherapy of viral and bacterial infections: past, present and future

The advent of COVID-19 and the persistent threat of infectious diseases such as tuberculosis, malaria, influenza and HIV/AIDS remind us of the marked impact that infections continue to have on public health. Some of the most effective protective measures are vaccines but these have been difficult to develop for some of these infectious diseases even after decades of research. The development of drugs and immunotherapies acting directly against the pathogen can be equally challenging, and such pathogen-directed therapeutics have the potential disadvantage of selecting for resistance. An alternative approach is provided by host-directed therapies, which interfere with host cellular processes required for pathogen survival or replication, or target the host immune response to infection (immunotherapies) to either augment immunity or ameliorate immunopathology. Here, we provide a historical perspective of host-directed immunotherapeutic interventions for viral and bacterial infections and then focus on SARS-CoV-2 and Mycobacterium tuberculosis, two major human pathogens of the current era, to indicate the key lessons learned and discuss candidate immunotherapeutic approaches, with a focus on drugs currently in clinical trials.

BORC complex specific components and Kinesin-1 mediate autophagy evasion by the autophagy-resistant Mycobacterium tuberculosis Beijing strain

Autophagy induction by starvation has been shown to enhance lysosomal delivery to mycobacterial phagosomes, resulting in the restriction of the Mycobacterium tuberculosis reference strain H37Rv. In contrast to H37Rv, our previous study showed that strains belonging to the notorious M. tuberculosis Beijing genotype could evade autophagic elimination. Our recent RNA-Seq analysis also discovered that the autophagy-resistant M. tuberculosis Beijing strain (BJN) evaded autophagic control by upregulating the expression of Kxd1, a BORC complex component, and Plekhm2, both of which function in lysosome positioning towards the cell periphery in host macrophages, thereby suppressing enhanced lysosomal delivery to its phagosome and sparing the BJN from elimination as a result. In this work, we further characterised the other specific components of the BORC complex, BORC5-8, and Kinesin proteins in autophagy resistance by the BJN. Depletion of BORCS5-8 and Kinesin-1, but not Kinesin-3, reverted autophagy avoidance by the BJN, resulting in increased lysosomal delivery to the BJN phagosomes. In addition, the augmented lysosome relocation towards the perinuclear region could now be observed in the BJN-infected host cells depleted in BORCS5-8 and Kinesin-1 expressions. Taken together, the data uncovered new roles for BORCS5-8 and Kinesin-1 in autophagy evasion by the BJN.

Host-directed therapy against tuberculosis: Concept and recent developments

Tuberculosis (TB) continues to remain at the forefront of the infectious disease burden globally, albeit with some aberrations during the COVID-19 pandemic. Among many factors, the emergence of drug resistance or antimicrobial resistance (AMR) has necessitated a renewed focus on developing novel and repurposed drugs against TB. Host-directed therapy (HDT) has emerged as an attractive alternative and a complementary strategy to the conventional antibiotic-based therapy of tuberculosis since HDT enjoys the advantage of disarming the pathogen of its ability to develop drug resistance. Considering the imminent threat of AMR across the spectrum of bacterial pathogens, HDT promises to overcome the drug shortage against superbugs. While all these make HDT a very attractive strategy, identifying the right set of host targets to develop HDT remains a challenge, despite remarkable development in the field over the past decade. In this review, we examine the host mechanisms, that either inadvertently or through targeted perturbation by the pathogen, help TB pathogenesis, and we discuss the latest developments in the targeting of some of the key pathways to achieve newer TB therapeutics.

Measurement of Autophagy Activity Reveals Time-Dependent, Bacteria-Specific Turnover during Mycobacterium tuberculosis Infection

The intracellular pathogen, Mycobacterium tuberculosis (M. tb) uses various mechanisms to evade its killing. One of such is phagosomal damage and cytosolic translocation which is then targeted by the host's bactericidal autophagy pathway. It is suggested that cytosolic translocation of M. tb is time-dependent, occurring at later time points of 48 to 72 h post-infection. It is, however, not known whether increased autophagic targeting correlates with these time points of infection. We investigated the time-dependent profile of autophagy activity through the course of M. tb infection in mammalian macrophages. Autophagy activity was inferred by the turnover measurement of autophagy markers and M. tb bacilli in THP-1 and RAW 264.7 macrophages. Over a period of 4 to 72 h, we observed highest autophagy turnover at 48 h of infection in M. tb-containing cells. This was evident by the highest turnover levels of p62 and intracellular M. tb. This supports observations of phagosomal damage mostly occurring at this time point and reveal the correlation of increased autophagy activity. The findings support the preservation of autophagy activity despite M. tb infection while also highlighting time-dependent differences in M. tb-infected macrophages. Future studies may explore time-dependent exogenous autophagy targeting towards host-directed anti-tuberculosis therapy.