Mycobacterium tuberculosis with different virulence reside within intact phagosomes and inhibit phagolysosomal biogenesis in alveolar macrophages of patients with pulmonary tuberculosis

Drug-Tolerant Mycobacterium tuberculosis Adopt Different Survival Strategies in Alveolar Macrophages of Patients with Pulmonary Tuberculosis

The rapid spread of drug-resistant M. tuberculosis (Mtb) strains and the phenomenon of phenotypic tolerance to drugs present challenges toward achieving the goal of tuberculosis (TB) elimination worldwide. By using the ex vivo cultures of alveolar macrophages obtained from lung tissues of TB patients after intensive antimicrobial chemotherapy before surgery, different subpopulations of multidrug-tolerant Mtb with a spectrum of phenotypic and growth features were identified in the same TB lesions. Our results are indicative of not only passive mechanisms generating nonheritable resistance of Mtb to antibiotics, which are associated mainly with a lack of Mtb growth, but also some active mechanisms of Mtb persistence, such as cell wall and metabolic pathway remodeling. In one of the subpopulations, non-acid-fast Mtb have undergone significant reprogramming with the restoration of acid-fastness, lipoarabinomannan expression and replication in host cells of some patients after withdrawal of anti-TB drugs. Our data indicate the universal stress protein Rv2623 as a clinically relevant biomarker of Mtb that has lost acid-fastness in human lungs. The studies of Mtb survival, persistence, dormancy, and resumption and the identification of biomarkers characterizing these phenomena are very important concerning the development of vaccines and drug regimens with individualized management of patients for overcoming the resistance/tolerance crisis in anti-TB therapy.

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.

Recent advances in PLGA micro/nanoparticle delivery systems as novel therapeutic approach for drug-resistant tuberculosis

Tuberculosis is a severe infectious disease caused by Mycobacterium tuberculosis and is a significant public health concern globally. The World Health Organization (WHO) recommends a combination regimen of several drugs, such as rifampicin (RIF), isoniazid (INH), pyrazinamide (PZA), and ethambutol (ETB), to treat tuberculosis. However, these drugs have low plasma concentrations after oral administration and require multiple high doses, which may lead to the occurrence and development of drug-resistant tuberculosis. Micro/Nanotechnology drug delivery systems have considerable potential in treating drug-resistant tuberculosis, allowing the sustained release of the drug and delivery of the drug to a specific target. These system properties could improve drug bioavailability, reduce the dose and frequency of administration, and solve the problem of non-adherence to the prescribed therapy. This study systematically reviewed the recent advances in PLGA micro/nanoparticle delivery systems as a novel therapeutic approach for drug-resistant tuberculosis.

Diagnostic value of Long non-coding Ribonucleic Acid non-coding activated by Deoxyribonucleic Acid damage in pulmonary tuberculosis and its regulatory role in Mycobacterium tuberculosis infection of macrophages

Pulmonary tuberculosis (PTB) infection is a chronic inflammatory response caused by Mycobacterium tuberculosis (Mtb). The purpose of this study was to confirm the value of Long non-coding RNA (LncRNA) non-coding activated by DNA damage (NORAD) in the diagnosis of PTB and to explore its mechanism in Mtb-infected macrophages. NORAD serum levels were estimated by qRT-PCR in 90 PTB patients and 85 healthy individuals. ROC curves were employed to assess the diagnostic value of NORAD for PTB. Human and murine macrophages were infected with Mtb strain H37Rv. CCK-8 and ELISA detected macrophages viability and inflammatory cytokine secretion. A dual-luciferase reporter assay was performed to analyze the targeting relationship between NORAD and microRNA (miR)-618. NORAD was significantly elevated in patients with PTB, and its positivity was correlated with inflammatory cytokines IL-1 β (r = 0.854), TNF-α (r = 0.617), IL-6 (r = 0.585). With an AUC of 0.918, and sensitivity and specificity of 80.0% and 89.4%, respectively, NORAD remarkedly identified PTB patients from healthy individuals. Furthermore, Mtb infection significantly increased NORAD levels in THP-1 and RAW264.7 and increased their viability and inflammation (P <0.001). However, this increased effect was weakened by reduced NORAD. Dual-luciferase reporter assay confirmed that miR-618 in macrophages was a target miRNA for NORAD and can be negatively regulated by it. Moreover, elevated miR-618 suppressed macrophage viability and inflammation in Mtb infection. NORAD is a potential diagnostic biomarker for PTB and is involved in Mtb infected macrophage activity and inflammation by targeting miR-618. This article is protected by copyright. All rights reserved.

Mycobacterium tuberculosis Load in Host Cells and the Antibacterial Activity of Alveolar Macrophages Are Linked and Differentially Regulated in Various Lung Lesions of Patients with Pulmonary Tuberculosis

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis (Mtb) infection with the formation of a broad range of abnormal lung lesions within a single patient. Although host-pathogen interactions determine disease outcome, they are poorly understood within individual lesions at different stages of maturation. We compared Mtb load in a tuberculoma wall and the lung tissue distant from tuberculomas in TB patients. These data were combined with an analysis of activation and bactericidal statuses of alveolar macrophages and other cell subtypes examined both in ex vivo culture and on the histological sections obtained from the same lung lesions. The expression of pattern recognition receptors CD14, CD11b, and TLR-2, transcription factors HIF-1α, HIF-2α, and NF-κB p50 and p65, enzymes iNOS and COX-2, reactive oxygen species (ROS) biosynthesis, and lipid production were detected for various lung lesions, with individual Mtb loads in them. The walls of tuberculomas with insufficient inflammation and excessive fibrosis were identified as being the main niche for Mtb survival (single or as colonies) in non-foamy alveolar macrophages among various lung lesions examined. The identification of factors engaged in the control of Mtb infection and tissue pathology in local lung microenvironments, where host-pathogen relationships take place, is critical for the development of new therapeutic strategies.

TNFRp75-dependent immune regulation of alveolar macrophages and neutrophils during early Mycobacterium tuberculosis and Mycobacterium bovis BCG infection

TNF signalling through TNFRp55 and TNFRp75, and receptor shedding is important for immune activation and regulation. TNFRp75 deficiency leads to improved control of Mycobacterium tuberculosis (M. tuberculosis) infection, but the effects of early innate immune events in this process are unclear. We investigated the role of TNFRp75 on cell activation and apoptosis of alveolar macrophages and neutrophils during M. tuberculosis and M. bovis BCG infection. We found increased microbicidal activity against M. tuberculosis occurred independently of IFNy and NO generation, and displayed an inverse correlation with alveolar macrophages (AMs) apoptosis. Both M. tuberculosis and M. bovis BCG induced higher expression of MHC-II in TNFRp75^-/- AMs; however, M bovis BCG infection did not alter AM apoptosis in the absence of TNFRp75. Pulmonary concentrations of CCL2, CCL3 and IL-1β were increased in TNFRp75^-/- mice during M, bovis BCG infection, but had no effect on neutrophil responses. Thus, TNFRp75-dependent regulation of mycobacterial replication is virulence dependent and occurs independently of early alveolar macrophage apoptosis and neutrophil responses.

IgG4 antibodies from patients with asymptomatic bancroftian filariasis inhibit the binding of IgG1 and IgG2 to C1q in a Fc-Fc-dependent mechanism

A striking feature of lymphatic filariasis (LF) is the clinical heterogeneity among exposed individuals. While endemic normals (EN) remain free of infection despite constant exposure to the infective larvae, a small group of patients, generally microfilaria free (Mf-) develops severe pathology (CP) such as lymphedema or hydrocele. Another group of infected individuals remains asymptomatic while expressing large amounts of microfilariae (Mf+). This Mf+ group is characterized by an immune-suppressed profile with high levels of anti-inflammatory cytokines and elevated IgG4. This particular immunoglobulin is unable to activate the complement. The complement system plays a critical role in both innate and adaptive immunity. However, its importance and regulation during LF is not fully understood. Using affinity chromatography and solid-phase-enzyme-immunoassays, we investigated the ability of antibody isotypes from LF clinical groups to bind C1q, the first element of the complement’s classical pathway. The results indicate that while C1q is similarly expressed in all LF clinical groups, IgG1–2 in the plasma from Mf+ individuals presented significantly lower affinity to C1q compared to EN, Mf−, and CP. In addition, selective depletion of IgG4 significantly enhanced the affinity of IgG1–2 to C1q in Mf+ individuals. Strikingly, no effect was seen on the ability of IgG3 to bind C1q in the same conditions. More interestingly, papain-generated IgG4-Fc-portions interacted with Fc portions of IgG1–2 as revealed by far-western blot analysis. These data suggest that while being unable to bind C1q, IgG4 inhibits the first steps of the complement classical pathway by IgG1 or IgG2 via Fc-Fc interactions.