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Bacteria naturally release membrane vesicles (MVs) under a variety of growth environments. Their production is associated with virulence due to their capacity to concentrate toxins and immunomodulatory molecules. In this report, we show that the 2 medically important species of mycobacteria, Mycobacterium tuberculosis and Mycobacterium bovis bacille Calmette-Guerin, release MVs when growing in both liquid culture and within murine phagocytic cells in vitro and in vivo.We documented MV production in a variety of virulent and nonvirulent mycobacterial species, indicating that release of MVs is a property conserved among mycobacterial species. Extensive proteomic analysis revealed that only MVs from the virulent strains contained TLR2 lipoprotein agonists. The interaction of MVs with macrophages isolated from mice stimulated the release of cytokines and chemokines in a TLR2-dependent fashion, and infusion of MVs into mouse lungs elicited a florid inflammatory response inWT but not TLR2-deficient mice. When MVs were administered to mice before M. tuberculosis pulmonary infection, an accelerated local inflammatory response with increased bacterial replication was seen in the lungs and spleens. Our results provide strong evidence that actively released mycobacterial vesicles are a deliverymechanism for immunologically active molecules that contribute tomycobacterial virulence. These findings may open up new horizons for understanding the pathogenesis of tuberculosis and developing vaccines., Introduction Many intracellular bacterial pathogens use membrane vesicles (MVs) as an alternative way to deliver ligands that can be recognized by host cells (1, 2). These MVs have been extensively [...]

Background: Up to date, Mycobacterium tuberculosis (Mtb) remains as the worst intracellular killer pathogen. To establish infection, inside the granuloma, Mtb reprograms its metabolism to support both growth and survival, keeping a balance between catabolism, anabolism and energy supply. Mtb knockouts with the faculty of being essential on a wide range of nutritional conditions are deemed as target candidates for tuberculosis (TB) treatment. Constraint-based genome-scale modeling is considered as a promising tool for evaluating genetic and nutritional perturbations on Mtb metabolic reprogramming. Nonetheless, few in silico assessments of the effect of nutritional conditions on Mtb's vulnerability and metabolic adaptation have been carried out. Results: A genome-scale model (GEM) of Mtb, modified from the H37Rv iOSDD890, was used to explore the metabolic reprogramming of two Mtb knockout mutants (pfkA-and icl-mutants), lacking key enzymes of central carbon metabolism, while exposed to changing nutritional conditions (oxygen, and carbon and nitrogen sources). A combination of shadow pricing, sensitivity analysis, and flux distributions patterns allowed us to identify metabolic behaviors that are in agreement with phenotypes reported in the literature. During hypoxia, at high glucose consumption, the Mtb pfkA-mutant showed a detrimental growth effect derived from the accumulation of toxic sugar phosphate intermediates (glucose-6-phosphate and fructose-6-phosphate) along with an increment of carbon fluxes towards the reductive direction of the tricarboxylic acid cycle (TCA). Furthermore, metabolic reprogramming of the icl-mutant (icl1&icl2) showed the importance of the methylmalonyl pathway for the detoxification of propionyl-CoA, during growth at high fatty acid consumption rates and aerobic conditions. At elevated levels of fatty acid uptake and hypoxia, we found a drop in TCA cycle intermediate accumulation that might create redox imbalance. Finally, findings regarding Mtb-mutant metabolic adaptation associated with asparagine consumption and acetate, succinate and alanine production, were in agreement with literature reports. Conclusions: This study demonstrates the potential application of genome-scale modeling, flux balance analysis (FBA), phenotypic phase plane (PhPP) analysis and shadow pricing to generate valuable insights about Mtb metabolic reprogramming in the context of human granulomas. [ABSTRACT FROM AUTHOR]

Background: Invariant natural killer t cells (iNkt) can be activated by certain types of glycolipids that have the potential to generate adjuvant effects which could be used to develop effective and safe immunotherapies. Many of these glycolipids have been isolated from natural organisms, but there is a great amount of these organisms completely unexplored as a source of these types of compounds. Some of these organisms are lichens which are complex symbiotic organisms that have been showed to contain glycolipids. Objectives: We decide to test if glycolipids isolated from lichens would be able to activate iNkt cells in vitro and in vivo. Methods: We have used extracted glycolipids from 43 different species of lichens from Colombia. We have used iNkt hybridoma cells, C57BL/6 mice, IL-2 ELISA and the B16 melanoma to test for the adjuvant capabilities of glycolipids isolated from lichens. Results: In this study we have found two glycolipids with the capacity to activate iNkt cells in vitro. one of the glycolipids was able to activate iNkt cells in vivo, and was competent to induce protection against the B16 melanoma in the mouse model. Conclusions: We propose a possible chemical structure for a novel glycolipid called β-GalCer-lich (1) derived from the lichen Stereocaulon ramulosum. [ABSTRACT FROM AUTHOR]

Control of HIV-1 viremia and progression to AIDS has been associated with specific HLA genes. The tumor necrosis factor (TNF) and the non-classical major histocompatibility (MHC) class I chain-related A (MICA) genes are located in the genomic segment between the HLA class I and II genes and variants of both genes have been identified. We thus analyzed TNF promoter and MICA variants in a well-characterized group of HIV-1 infected individuals with different abilities to control HIV-1 viremia. In our cohort, the -1030/-862-linked TNF promoter single-nucleotide polymorphisms (SNPs), but not MICA variants, are significantly associated with lack of control of HIV-1 viremia (P=0.03). This association is independent of those HLA-B35 alleles associated with HIV-1 disease progression with which the -862 TNF SNP has previously been independently associated. Thus, non-randomly associated genes near the TNF locus are likely involved in control of HIV-1 viremia. [ABSTRACT FROM AUTHOR]

A great amount of knowledge on natural killer T cells (iNKTs) is now available, but a consensus about their activation mechanisms has not been reached. These cells recognize different glycolipid antigens through the CD1d molecule. Such antigens may be endogenous, derived from bacteria (foreign) and synthetic, the latter have been developed for clinical applications. There exists much interest in understanding how these different glycolipid compounds induce different types of polarization, but it has been difficult to reach a consensus due to the fact that responses depend on different factors such as: the nature of the molecule, the internalization process and the presentation of the glycolipids. Moreover, activation of iNKT cells is determined by the type and state of the antigen presenting cell, the co-stimulatory molecules, the transactivation mechanisms and the location of the glycolipid-CD1d complexes on the plasma membrane, such as the lipid rafts. This review explores the evidence about the factors that affect activation of iNKT cells in order to understand their immune-modulatory potential.