Unraveling the Role of MicroRNAs in Mycobacterium tuberculosis Infection and Disease: Advances and Pitfalls

Zebrafish tsc1 and cxcl12a increase susceptibility to mycobacterial infection

Regulation of host miRNA expression is a contested node that controls the host immune response to mycobacterial infection. The host must counter subversive efforts of pathogenic mycobacteria to launch a protective immune response. Here, we examine the role of miR-126 in the zebrafish-Mycobacterium marinum infection model and identify a protective role for infection-induced miR-126 through multiple effector pathways. We identified a putative link between miR-126 and the tsc1a and cxcl12a/ccl2/ccr2 signalling axes resulting in the suppression of non-tnfa expressing macrophage accumulation at early M. marinum granulomas. Mechanistically, we found a detrimental effect of tsc1a expression that renders zebrafish embryos susceptible to higher bacterial burden and increased cell death via mTOR inhibition. We found that macrophage recruitment driven by the cxcl12a/ccl2/ccr2 signalling axis was at the expense of the recruitment of classically activated tnfa-expressing macrophages and increased cell death around granulomas. Together, our results delineate putative pathways by which infection-induced miR-126 may shape an effective immune response to M. marinum infection in zebrafish embryos.

Diagnostic performance of microRNA-29a in active pulmonary tuberculosis: a systematic review and meta-analysis

BACKGROUND

In recent years, more and more studies have shown that microRNA-29a (miRNA-29a) can be used as a potential biomarker for active tuberculosis, but the results of these studies are not consistent.

OBJECTIVE

To comprehensively evaluate the value of miRNA-29a in the diagnosis of active tuberculosis by meta-analysis.

METHODS

The databases of CNKI, WanFang, PubMed, The Cochrane Library, Web of Science and EMBASE were searched for relevant studies. Studies were screened strictly according to inclusion and exclusion criteria. QUADAS-2 scale was used to evaluate the quality of the included studies. Data were extracted and analyzed by Meta-DiSc 1.4 and Stata 16.0 software.

RESULTS

13 articles were included, including a total of 1598 subjects, including 872 active tuberculosis patients and 726 controls. The combined sensitivity and specificity of miRNA-29a in the diagnosis of active tuberculosis were 78 % and 76 %, respectively, and the area under the overall summary receiver operating characteristic curve was 0.8564.

CONCLUSION

miRNA-29a can be used as a biomarker for the diagnosis of active tuberculosis.

Plasmodium falciparum infection reshapes the human microRNA profiles of red blood cells and their extracellular vesicles

Plasmodium falciparum, a human malaria parasite, develops in red blood cells (RBCs), which represent approximately 70% of all human blood cells. Additionally, RBC-derived extracellular vesicles (RBC-EVs) represent 7.3% of the total EV population. The roles of microRNAs (miRNAs) in the consequences of P. falciparum infection are unclear. Here, we analyzed the miRNA profiles of non-infected human RBCs (niRBCs), ring-infected RBCs (riRBCs), and trophozoite-infected RBCs (trRBCs), as well as those of EVs secreted from these cells. Hsa-miR-451a was the most abundant miRNA in all RBC and RBC-EV populations, but its expression level was not affected by P. falciparum infection. Overall, the miRNA profiles of RBCs and their EVs were altered significantly after infection. Most of the differentially expressed miRNAs were shared between RBCs and their EVs. A target prediction analysis of the miRNAs revealed the possible identity of the genes targeted by these miRNAs (CXCL10, OAS1, IL7, and CCL5) involved in immunomodulation.

Diagnosis and biomarkers for ocular tuberculosis: From the present into the future

Tuberculosis is an airborne disease caused by Mycobacterium tuberculosis (Mtb) and can manifest both pulmonary and extrapulmonary disease, including ocular tuberculosis (OTB). Accurate diagnosis and swift optimal treatment initiation for OTB is faced by many challenges combined with the lack of standardized treatment regimens this results in uncertain OTB outcomes. The purpose of this study is to summarize existing diagnostic approaches and recently discovered biomarkers that may contribute to establishing OTB diagnosis, choice of anti-tubercular therapy (ATT) regimen, and treatment monitoring. The keywords ocular tuberculosis, tuberculosis, Mycobacterium, biomarkers, molecular diagnosis, multi-omics, proteomics, genomics, transcriptomics, metabolomics, T-lymphocytes profiling were searched on PubMed and MEDLINE databases. Articles and books published with at least one of the keywords were included and screened for relevance. There was no time limit for study inclusion. More emphasis was placed on recent publications that contributed new information about the pathogenesis, diagnosis, or treatment of OTB. We excluded abstracts and articles that were not written in the English language. References cited within the identified articles were used to further supplement the search. We found 10 studies evaluating the sensitivity and specificity of interferon-gamma release assay (IGRA), and 6 studies evaluating that of tuberculin skin test (TST) in OTB patients. IGRA (Sp = 71-100%, Se = 36-100%) achieves overall better sensitivity and specificity than TST (Sp = 51.1-85.7%; Se = 70.9-98.5%). For nuclear acid amplification tests (NAAT), we found 7 studies on uniplex polymerase chain reaction (PCR) with different Mtb targets, 7 studies on DNA-based multiplex PCR, 1 study on mRNA-based multiplex PCR, 4 studies on loop-mediated isothermal amplification (LAMP) assay with different Mtb targets, 3 studies on GeneXpert assay, 1 study on GeneXpert Ultra assay and 1 study for MTBDRplus assay for OTB. Specificity is overall improved but sensitivity is highly variable for NAATs (excluding uniplex PCR, Sp = 50-100%; Se = 10.5-98%) as compared to IGRA. We also found 3 transcriptomic studies, 6 proteomic studies, 2 studies on stimulation assays, 1 study on intraocular protein analysis and 1 study on T-lymphocyte profiling in OTB patients. All except 1 study evaluated novel, previously undiscovered biomarkers. Only 1 study has been externally validated by a large independent cohort. Future theranostic marker discovery by a multi-omics approach is essential to deepen pathophysiological understanding of OTB. Combined these might result in swift, optimal and personalized treatment regimens to modulate the heterogeneous mechanisms of OTB. Eventually, these studies could improve the current cumbersome diagnosis and management of OTB.

Diagnostic biomarkers for active tuberculosis: progress and challenges

Tuberculosis (TB) is a leading cause of morbidity and mortality from a single infectious agent, despite being preventable and curable. Early and accurate diagnosis of active TB is critical to both enhance patient care, improve patient outcomes, and break Mycobacterium tuberculosis (Mtb) transmission cycles. In 2020 an estimated 9.9 million people fell ill from Mtb, but only a little over half (5.8 million) received an active TB diagnosis and treatment. The World Health Organization has proposed target product profiles for biomarker- or biosignature-based diagnostics using point-of-care tests from easily accessible specimens such as urine or blood. Here we review and summarize progress made in the development of pathogen- and host-based biomarkers for active TB diagnosis. We describe several unique patient populations that have posed challenges to development of a universal diagnostic TB biomarker, such as people living with HIV, extrapulmonary TB, and children. We also review additional limitations to widespread validation and utilization of published biomarkers. We conclude with proposed solutions to enhance TB diagnostic biomarker validation and uptake.

The Multifaceted Roles of Autophagy in Infectious, Obstructive, and Malignant Airway Diseases

Autophagy is a highly conserved dynamic process by which cells deliver their contents to lysosomes for degradation, thus ensuring cell homeostasis. In response to environmental stress, the induction of autophagy is crucial for cell survival. The dysregulation of this degradative process has been implicated in a wide range of pathologies, including lung diseases, representing a relevant potential target with significant clinical outcomes. During lung disease progression and infections, autophagy may exert both protective and harmful effects on cells. In this review, we will explore the implications of autophagy and its selective forms in several lung infections, such as SARS-CoV-2, Respiratory Syncytial Virus (RSV) and Mycobacterium tuberculosis (Mtb) infections, and different lung diseases such as Cystic Fibrosis (CF), Chronic Obstructive Pulmonary Disease (COPD), and Malignant Mesothelioma (MM).

Mammalian host microRNA response to plasmodial infection: role as therapeutic target and potential biomarker

The appearance of increasing drug resistance in apicomplexan intracellular Plasmodium falciparum presents a significant challenge. P. falciparum infection results in cerebral malaria (CM), causing irreversible damage to the brain leading to high mortality cases. To enhance the clinical outcome of the disease, further research is required to identify new molecular targets involved in disease manifestations. Presently, the role of non-coding microRNAs (miRNAs) derived from different cells implicated in CM pathogenesis is still barely understood. Despite the absence of miRNA machinery in Plasmodium, host-parasite interactions can lead to disease severity or impart resistance to malaria. Cytoadherence and sequestration of parasitized RBCs dysregulate the miRNA profile of brain endothelial cells, leukocytes, monocytes, and platelets, disrupting blood-brain barrier integrity and activating inflammatory signaling pathways. The abundance of miRNA in blood plasma samples of CM patients directly correlates to cerebral symptoms compared to non-CM patients and healthy individuals. Moreover, the differential host-miRNA signatures distinguish P. falciparum from P. vivax infection. Here, we review the diverse functions of host-miRNA, either protective, pathogenic, or a combination of the two, which may act as prognostic markers and novel antimalarial drug targets.

MicroRNA-155 Modulates Macrophages' Response to Non-Tuberculous Mycobacteria through COX-2/PGE2 Signaling

Non-tuberculous mycobacteria (NTM) have been recognized as a causative agent of various human diseases, including severe infections in immunocompromised patients, such as people living with HIV. The most common species identified is the Mycobacterium avium-intracellulare complex (MAI/MAC), accounting for a majority of infections. Despite abundant information detailing the clinical significance of NTM, little is known about host–pathogen interactions in NTM infection. MicroRNAs (miRs) serve as important post-transcriptional regulators of gene expression. Using a microarray profile, we found that the expression of miR-155 and cyclo-oxygenase 2 (COX-2) is significantly increased in bone-marrow-derived macrophages from mice and human monocyte-derived macrophages from healthy volunteers that are infected with NTM. Antagomir against miR-155 effectively suppressed expression of COX-2 and reduced Prostaglandin E₂(PGE2) secretion, suggesting that COX-2/PGE2 expression is dependent on miR-155. Mechanistically, we found that inhibition of NF-κB activity significantly reduced miR-155/COX-2 expression in infected macrophages. Most importantly, blockade of COX-2, E-prostanoid receptors (EP2 and EP4) enhanced killing of MAI in macrophages. These findings provide novel mechanistic insights into the role of miR-155/COX-2/PGE2 signalling and suggest that induction of these pathways enhances survival of mycobacteria in macrophages. Defining host–pathogen interactions can lead to novel immunomodulatory therapies for NTM infections which are difficult to treat.

Human genetic background in susceptibility to tuberculosis

Tuberculosis (TB), especially in developing countries, is a major threat to human health. The pathogenesis of TB remains poorly understood, and <5%-10% of individuals infected with Mycobacterium tuberculosis (MTB) will develop clinical disease. The human genetic factors contributing to susceptibility or resistance to TB pathogenesis have been investigated by high-throughput and low-throughput association studies. Genetic polymorphisms of several genes including TLR, IGRM, VDR, ASAP1, AGMO, FOXP1, and UBLCP1 effect on the disease phenotype and also the outcome of TB treatment. Recently, microRNAs (miRNAs), which negatively regulated gene expression at the posttranscriptionally level, have gained increasing attention due to their altered expression in various human diseases, including some infections. They are crucial posttranscriptional regulators of immune response in both innate and adaptive immunity. It has been established in recent studies that the host immune response against MTB is regulated by many miRNAs, most of which are induced by MTB infection. Moreover, differential expression of miRNAs in TB patients may help distinguish between TB patients and healthy individuals or latent TB. In this review, we summarize and discuss the literature and highlight the role of selected single nucleotide polymorphisms and miRNAs that have been associated with TB infection.

The Role of microRNAs and Long Non-Coding RNAs in the Regulation of the Immune Response to Mycobacterium tuberculosis Infection

Non-coding RNAs have emerged as critical regulators of the immune response to infection. MicroRNAs (miRNAs) are small non-coding RNAs which regulate host defense mechanisms against viruses, bacteria and fungi. They are involved in the delicate interplay between Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), and its host, which dictates the course of infection. Differential expression of miRNAs upon infection with M. tuberculosis, regulates host signaling pathways linked to inflammation, autophagy, apoptosis and polarization of macrophages. Experimental evidence suggests that virulent M. tuberculosis often utilize host miRNAs to promote pathogenicity by restricting host-mediated antibacterial signaling pathways. At the same time, host- induced miRNAs augment antibacterial processes such as autophagy, to limit bacterial proliferation. Targeting miRNAs is an emerging option for host-directed therapies. Recent studies have explored the role of long non-coding RNA (lncRNAs) in the regulation of the host response to mycobacterial infection. Among other functions, lncRNAs interact with chromatin remodelers to regulate gene expression and also function as miRNA sponges. In this review we attempt to summarize recent literature on how miRNAs and lncRNAs are differentially expressed during the course of M. tuberculosis infection, and how they influence the outcome of infection. We also discuss the potential use of non-coding RNAs as biomarkers of active and latent tuberculosis. Comprehensive understanding of the role of these non-coding RNAs is the first step towards developing RNA-based therapeutics and diagnostic tools for the treatment of TB.

Integrative Multi-Omics Reveals Serum Markers of Tuberculosis in Advanced HIV

Tuberculosis (TB) accounts for disproportionate morbidity and mortality among persons living with HIV (PLWH). Conventional methods of TB diagnosis, including smear microscopy and Xpert MTB/RIF, have lower sensitivity in PLWH. Novel high-throughput approaches, such as miRNAomics and metabolomics, may advance our ability to recognize subclinical and difficult-to-diagnose TB, especially in very advanced HIV. We conducted a case-control study leveraging REMEMBER, a multi-country, open-label randomized controlled trial comparing 4-drug empiric standard TB treatment with isoniazid preventive therapy in PLWH initiating antiretroviral therapy (ART) with CD4 cell counts <50 cells/μL. Twenty-three cases of incident TB were site-matched with 32 controls to identify microRNAs (miRNAs), metabolites, and cytokines/chemokines, associated with the development of newly diagnosed TB in PLWH. Differentially expressed miRNA analysis revealed 11 altered miRNAs with a fold change higher than 1.4 or lower than -1.4 in cases relative to controls (p<0.05). Our analysis revealed no differentially abundant metabolites between cases and controls. We found higher TNFα and IP-10/CXCL10 in cases (p=0.011, p=0.0005), and higher MDC/CCL22 in controls (p=0.0072). A decision-tree algorithm identified gamma-glutamylthreonine and hsa-miR-215-5p as the optimal variables to classify incident TB cases (AUC 0.965; 95% CI 0.925-1.000). hsa-miR-215-5p, which targets genes in the TGF-β signaling pathway, was downregulated in cases. Gamma-glutamylthreonine, a breakdown product of protein catabolism, was less abundant in cases. To our knowledge, this is one of the first uses of a multi-omics approach to identify incident TB in severely immunosuppressed PLWH.

Regulatory Mechanisms of Autophagy-Targeted Antimicrobial Therapeutics Against Mycobacterial Infection

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen causing human tuberculosis, an infectious disease that still remains as a global health problem. Autophagy, a lysosomal degradative process, has emerged as a critical pathway to restrict intracellular Mtb growth through enhancement of phagosomal maturation. Indeed, several autophagy-modulating agents show promise as host-directed therapeutics for Mtb infection. In this Review, we discuss recent progress in our understanding the molecular mechanisms underlying the action of autophagy-modulating agents to overcome the immune escape strategies mediated by Mtb. The factors and pathways that govern such mechanisms include adenosine 5'-monophosphate-activated protein kinase, Akt/mammalian TOR kinase, Wnt signaling, transcription factor EB, cathelicidins, inflammation, endoplasmic reticulum stress, and autophagy-related genes. A further understanding of these mechanisms will facilitate the development of host-directed therapies against tuberculosis as well as infections with other intracellular bacteria targeted by autophagic degradation.

MicroRNA research: The new dawn of Tuberculosis

Tuberculosis (TB) is global, one of the most fatal communicable diseases and leading cause of worldwide mortality. One-third of the global population is latently affected by Mtb (Mycobacterium tuberculosis) due to its ability to circumvent the host's immune response for its own survival. MicroRNAs (miRNAs) are small, non-coding RNAs which function at the post-transcriptional level and are critical in fine-tuning immune responses regulating the repertoire of genes expressed in immune cells. Recent studies have established their crucial role against TB. Furthermore, the differential expression pattern of miRNAs has revealed the potential role of miRNAs as biomarkers which could be utilized to differentiate between healthy controls and active TB patients or between active and latent TB. The recent advancements made in the field of miRNA regulation of the host responses against TB, as well as the potential of miRNAs as biomarkers for TB diagnosis are discussed here in this review.

Tuberculosis-Associated MicroRNAs: From Pathogenesis to Disease Biomarkers

Tuberculosis (TB) caused by Mycobacterium tuberculosis is one of the most lethal infectious diseases with estimates of approximately 1.4 million human deaths in 2018. M. tuberculosis has a well-established ability to circumvent the host immune system to ensure its intracellular survival and persistence in the host. Mechanisms include subversion of expression of key microRNAs (miRNAs) involved in the regulation of host innate and adaptive immune response against M. tuberculosis. Several studies have reported differential expression of miRNAs during active TB and latent tuberculosis infection (LTBI), suggesting their potential use as biomarkers of disease progression and response to anti-TB therapy. This review focused on the miRNAs involved in TB pathogenesis and on the mechanism through which miRNAs induced during TB modulate cell antimicrobial responses. An attentive study of the recent literature identifies a group of miRNAs, which are differentially expressed in active TB vs. LTBI or vs. treated TB and can be proposed as candidate biomarkers.

Pediatric Tuberculosis: The Impact of "Omics" on Diagnostics Development

Tuberculosis (TB) is a major public health concern for all ages. However, the disease presents a larger challenge in pediatric populations, partially owing to the lack of reliable diagnostic standards for the early identification of infection. Currently, there are no biomarkers that have been clinically validated for use in pediatric TB diagnosis. Identification and validation of biomarkers could provide critical information on prognosis of disease, and response to treatment. In this review, we discuss how the “omics” approach has influenced biomarker discovery and the advancement of a next generation rapid point-of-care diagnostic for TB, with special emphasis on pediatric disease. Limitations of current published studies and the barriers to their implementation into the field will be thoroughly reviewed within this article in hopes of highlighting future avenues and needs for combating the problem of pediatric tuberculosis.