1,721,160 research outputs found
The challenging task of screening and monitoring tuberculosis infection in candidates for biological therapies
No full textComment on: Latent tuberculosis infection in patients with chronic plaque psoriasis who are candidates for biological therapy
The Spectrum of Tuberculosis Infection: New Perspectives in the Era of Biologics
No full textThe risk of developing active tuberculosis (TB) is higher in patients taking immunosuppressive drugs, either as a result of reactivation of a latent TB infection (LTBI) or following a new infection with Mycobacterium tuberculosis (Mtb). We discuss the pathogenesis and spectrum of Mtb infection in light of its implication for the management of patients following biologic regimens. Among recent findings, during LTBI, Mtb can persist in the host for decades, localizing in many tissues and assuming different metabolic states that protect the bacilli from the harsh host immune defenses. Despite the strong host T cell response against Mtb, the bacilli may also replicate and multiply in vivo, and any event impairing immune function may lead to active and uncontrolled bacteria replication and active disease. The classic dichotomy between active and latent disease is being reconsidered in favor of a continuous and dynamic spectrum extending from infection to disease that can coexist in the same individual. This TB spectrum results from the dynamic interaction between the host immune system and the bacilli and can be maintained in equilibrium for decades, although treatments affecting the host immune cells may result in disease reactivation
Functional domains present in the mycobacterial hemagglutinin, HBHA
No full textIdentification and characterization of mycobacterial adhesins and complementary host receptors required for colonization and dissemination of mycobacteria in host tissues are needed for a more complete understanding of the pathogenesis of diseases caused by these bacteria and for the development of effective vaccines. Previous investigations have demonstrated that a 28-kDa heparin-binding mycobacterial surface protein, HBHA, can agglutinate erythrocytes and promote mycobacterial aggregation in vitro. In this study, further molecular and biochemical analysis of HBHA demonstrates that it has three functional domains: a transmembrane domain of 18 amino acids residing near the N terminus, a large domain of 81 amino acids consistent with an alpha-helical coiled-coil region, and a Lys-Pro-Ala-rich C-terminal domain that mediates binding to proteoglycans. Using His-tagged recombinant HBHA proteins and nickel chromatography we demonstrate that HBHA polypeptides which contain the coiled-coil region form multimers. This tendency to oligomerize may be responsible for the induction of mycobacterial aggregation since a truncated N-terminal HBHA fragment containing the coiled-coil domain promotes mycobacterial aggregation. Conversely, a truncated C-terminal HBHA fragment which contains Lys-Pro-Ala-rich repeats binds to the proteoglycan decorin. These results indicate that HBHA contains at least three distinct domains which facilitate intercalation into surface membranes, promote bacterium-bacterium interactions, and mediate the attachment to sulfated glycoconjugates found in host tissues
PGRS domain structures: Doomed to sail the mycomembrane
Full text linkThe impact of artificial intelligence (AI) in understanding biological processes is potentially immense. Structural elucidation of mycobacterial PE_PGRS is sustenance to unveil the role of these enigmatic proteins. We propose a PGRS "sailing" model as a smart tool to diffuse along the mycomembrane, to expose structural motifs for host interactions, and/or to ship functional protein modules at their C-terminus
Alternative therapies against Mycobacterium abscessus infections
Full text linkBackground: Mycobacterium abscessus (Mab) is considered as the most pathogenic rapid-growing mycobacteria in humans, causing pulmonary and extra-pulmonary diseases, especially in patients with cystic fibrosis. Mab shows intrinsic and acquired resistance to many drugs, leaving limited treatment options that lead to a generally poor prognosis. The standard therapeutic regimen last for more than 6 months and consists of a drug cocktail that ideally includes a macrolide and amikacin. Yet, toxicity and efficacy are suboptimal due also to the high toxicity. There is a need to introduce innovative and out-of-the-box approaches to improve treatments. Objectives: In this narrative review, we summarize the recent research on the alternative strategies proposed and discuss the importance of using appropriate experimental assays to assess their activity. Sources: Included articles were identified by searching PubMed and MEDLINE until June 2023. The search terms were 'Mycobacterium abscessus', 'antimicrobial', and 'alternative therapies'. Additional relevant references were obtained from articles retrieved from the primary search. Content: Therapies against Mab including host directed therapies, repurposed drugs, phage therapy, anti-virulence strategies, essential oils, and inhalation therapies. Implications: Alternative treatments may represent a valid tool to cope the burden of antimicrobial resistance in Mab-caused diseases
Expression of the PE_PGRS 33 protein in Mycobacterium smegmatis triggers necrosis in macrophages and enhanced mycobacterial survival
No full textResearch on mycobacteria-specific PE_PGRS genes indicates that they code for cell surface proteins that may influence virulence and the infection of host cells by mycobacteria. In the studies presented here, we have expressed the PE_PGRS 33 gene in a non-pathogenic fast-growing Mycobacterium smegmatis strain and demonstrated that it survives better in macrophage cultures, in vitro as well as in mice after intraperitoneal administration, than the parental strain containing the vector only or a strain expressing only the PE domain of PE_PGRS 33. In macrophages, enhanced colonization by the M. smegmatis expressing PE_PGRS 33 was associated with macrophage aggregation and clearance of macrophage monolayers, visible cell necrosis and significantly greater levels of TNF (TNF-alpha) in the cultures compared with controls. The presence of macrophage cell necrosis was confirmed by measurement of significantly greater levels of lactate dehydrogenase and nucleosomes in the supernatants of the macrophage cultures infected with M. smegmatis expressing PE_PGRS 33. Antibodies directed against TNF partially reduced cytolysis, suggesting that this cytokine is critical but not sufficient for the observed macrophage necrosis and enhanced mycobacterial survival. These results extend earlier observations, which suggested that PE_PGRS proteins may have a role in the pathogenesis of mycobacterial disease and that there may be a specific role for these proteins in influencing host cell responses to infection
Impact of Structural Domains of the Heparin Binding Hemagglutinin of Mycobacterium tuberculosis on Function
No full textAmong the few well characterized virulence factors of Mycobacterium tuberculosis (Mtb) is the heparin-binding hemagglutinin (HBHA). HBHA is a 21-kDa protein that localizes to the mycobacterial surface where it can interact with host components. Interaction with epithelial cells and components of the extracellular matrix is mediated by the methylated lysine-rich C-terminal domain of the protein. The N-terminal end of HBHA contains a coiled coil motif which is involved in protein oligomerization and bacterial-bacterial aggregation. In this report, we will focus our attention on what is known about the structure of the HBHA protein and the protein function and role in TB pathogenesis
Mycobacterium tuberculosis virulence: insights and impact on vaccine development
Full text linkThe existing TB vaccine, the attenuated Mycobacterium bovis strain BCG, is effective in protecting infants from severe forms of the disease, while its efficacy in protecting adults from pulmonary TB is poor. In the last two decades, a renewed interest in TB resulted in the development of several candidate vaccines that are now entering clinical trials. However, most of these vaccines are based on a common rationale and aim to induce a strong T-cell response against Mycobacterium tuberculosis. Recent advancements in the understanding of M. tuberculosis virulence determinants and associated pathogenic strategies are opening a new and broader view of the complex interaction between this remarkable pathogen and the human host, providing insights at molecular level that could lead to a new rationale for the design of novel antitubercular vaccines. A vaccination strategy that simultaneously targets different steps in TB pathogenesis may result in improved protection and reduced TB transmission
The role of IGRA in the diagnosis of tuberculosis infection, differentiating from active tuberculosis, and decision making for initiating treatment or preventive therapy of tuberculosis infection
Full text linkObjectives: The World Health Organization estimated that a quarter of the global population is infected by Mycobacterium tuberculosis (Mtb). A better control of tuberculosis (TB) is based on the ability to detect Mtb infection, identifying the progressors to TB disease, undergoing to preventive therapy and implementing strategies to register the infections and treatment completion. Design: we reviewed the literature regarding the tests available for TB infection diagnosis, the preventive therapies options and the cascade of care for controlling TB at a public health level. Results: current tests for TB infection diagnosis as IFN-γ release assays or tuberculin skin tests are based on the detection of an immune response to Mtb in the absence of clinical disease. The main limit is their low accuracy to detect progressors to disease. New preventive treatments are available with short duration that are associated with better adherence. Options to register TB infections are presented. Conclusions: Tests to diagnose TB infection are available but they lack accuracy to identify the progressors from infection to TB disease. Shorter preventive TB therapy are available but need to be implemented worldwide. A TB infection registry is crucial for improving the cascade of care leading to a better TB control
Bacillus cereus keratitis associated with contact lens wear
No full textWe report the first case of contact lens-related Bacillus cereus keratitis and ulcer associated with B. cereus contamination of the contact lens case. This is also the first study to investigate and establish the genetic identity of an organism isolated from the cornea and contact lens case in a patient with contact lens-associated keratitis
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