The mechanisms by which the immune system achieves constant T cell numbers throughout life, thereby controlling autoaggressive cell expansions, are to date not completely understood. Here, we show that the CD25+ subpopulation of naturally activated (CD45RBlow) CD4 T cells, but not CD25− CD45RBlow CD4 T cells, inhibits the accumulation of cotransferred CD45RBhigh CD4 T cells in lymphocyte-deficient mice. However, both CD25+ and CD25− CD45RBlow CD4 T cell subpopulations contain regulatory cells, since they can prevent naive CD4 T cell-induced wasting disease. In the absence of a correlation between disease and the number of recovered CD4+ cells, we conclude that expansion control and disease prevention are largely independent processes. CD25+ CD45RBlow CD4 T cells from IL-10-deficient mice do not protect from disease. They accumulate to a higher cell number and cannot prevent the expansion of CD45RBhigh CD4 T cells upon transfer compared with their wild-type counterparts. Although CD25+ CD45RBlow CD4 T cells are capable of expanding when transferred in vivo, they reach a homeostatic equilibrium at lower cell numbers than CD25− CD45RBlow or CD45RBhigh CD4 T cells. We conclude that CD25+ CD45RBlow CD4 T cells from nonmanipulated mice control the number of peripheral CD4 T cells through a mechanism involving the production of IL-10 by regulatory T cells.

To characterize the genetic determinants of resistance to antituberculosis drugs, we performed a genome-wide association study (GWAS) of 6,465 Mycobacterium tuberculosis clinical isolates from more than 30 countries. A GWAS approach within a mixed-regression framework was followed by a phylogenetics-based test for independent mutations. In addition to mutations in established and recently described resistance-associated genes, novel mutations were discovered for resistance to cycloserine, ethionamide and para-aminosalicylic acid. The capacity to detect mutations associated with resistance to ethionamide, pyrazinamide, capreomycin, cycloserine and para-aminosalicylic acid was enhanced by inclusion of insertions and deletions. Odds ratios for mutations within candidate genes were found to reflect levels of resistance. New epistatic relationships between candidate drug-resistance-associated genes were identified. Findings also suggest the involvement of efflux pumps (drrA and Rv2688c) in the emergence of resistance. This study will inform the design of new diagnostic tests and expedite the investigation of resistance and compensatory epistatic mechanisms.

Background and aims Probiotics and their metabolic products, here called postbiotics, have been proposed as food supplements for a healthier intestinal homeostasis, but also as therapeutic aids in inflammatory bowel disease (IBD) with, however, very little clinical benefit. This may be due to the lack of reliable preclinical models for testing the efficacy of different strains. Methods The activity of three probiotic strains of Lactobacillus (or a postbiotic) was analysed and compared with a pathogenic strain of Salmonella on a novel organ culture system of human healthy and IBD intestinal mucosa developed in our laboratory. The system maintains an apical to basolateral polarity during stimulation due to the presence of a glued cave cylinder. The cylinder is detached at the end of the experiment and the tissue is processed for histology and immunohistochemistry. Cytokines released from the basolateral side are analysed. Results The model system provides several physiological characteristics typical of a mucosal microenvironment including the presence of an organised mucus layer and an apical to basolateral polarity.

Background Mycobacterium tuberculosis infection is thought to induce oxidative stress. N-acetyl-cysteine (NAC) is widely used in patients with chronic pulmonary diseases including tuberculosis due to its mucolytic and anti-oxidant activities. Here, we tested whether NAC exerts a direct antibiotic activity against mycobacteria.MethodsOxidative stress status in plasma was compared between pulmonary TB (PTB) patients and those with latent M. tuberculosis infection (LTBI) or healthy uninfected individuals. Lipid peroxidation, DNA oxidation and cell death, as well as accumulation of reactive oxygen species (ROS) were measured in cultures of primary human monocyte-derived macrophages infected with M. tuberculosis and treated or not with NAC. M. tuberculosis, M. avium and M. bovis BCG cultures were also exposed to different doses of NAC with or without medium pH adjustment to control for acidity. The anti-mycobacterial effect of NAC was assessed in M. tuberculosis infected human THP-1 cells and bone marrow-derived macrophages from mice lacking a fully functional NADPH oxidase system. The capacity of NAC to control M. tuberculosis infection was further tested in vivo in a mouse (C57BL/6) model.ResultsPTB patients exhibited elevated levels of oxidation products and a reduction of anti-oxidants compared with LTBI cases or uninfected controls. NAC treatment in M. tuberculosis-infected human macrophages resulted in a decrease of oxidative stress and cell death evoked by mycobacteria. Importantly, we observed a dose-dependent reduction in metabolic activity and in vitro growth of NAC treated M. tuberculosis, M. avium and M. bovis BCG. Furthermore, anti-mycobacterial activity in infected macrophages was shown to be independent of the effects of NAC on the host NADPH oxidase system in vitro. Short-term NAC treatment of M. tuberculosis infected mice in vivo resulted in a significant reduction of mycobacterial loads in the lungs.ConclusionsNAC exhibits potent anti-mycobacterial effects and may limit M. tuberculosis infection and disease both through suppression of the host oxidative response and through direct antimicrobial activity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0872-7) contains supplementary material, which is available to authorized users.

Significant differences in function have been observed among lectins structurally similar to concanavalin A, but their high homology with this widely used lectin has kept them in obscurity. The observation of large differences in the potency of many of these Diocleinae lectins as stimulators of Interferon-g production by human peripheral blood mononuclear cells has lead to a major effort to unravel their chemical structure and biological activity. Modeling studies of some of these lectins reveal conformational changes in side chains of some residues involved in the carbohydrate-binding site, with possible effects on the ability of these proteins to recognize specific carbohydrate structures. Additionally, all them constitute in fact a mixture of isolectins, which in different proportions could lead to diverse effects. The present review of the biological actions of Diocleinae lectins includes several in vitro and in vivo immunological findings, as well as their effects on insect growth and reproduction. In these systems Diocleinae lectins proved to be quite diverse in their potency. Such diversity in the biological activity of highly related proteins recalls the origin of the name protein: like Proteus, the capability of assuming various forms is the essential feature of this class of molecules.

BackgroundApproximately 10 % of the Mycobacterium tuberculosis genome is made up of two families of genes that are poorly characterized due to their high GC content and highly repetitive nature. The PE and PPE families are typified by their highly conserved N-terminal domains that incorporate proline-glutamate (PE) and proline-proline-glutamate (PPE) signature motifs. They are hypothesised to be important virulence factors involved with host-pathogen interactions, but their high genetic variability and complexity of analysis means they are typically disregarded in genome studies.ResultsTo elucidate the structure of these genes, 518 genomes from a diverse international collection of clinical isolates were de novo assembled. A further 21 reference M. tuberculosis complex genomes and long read sequence data were used to validate the approach. SNP analysis revealed that variation in the majority of the 168 pe/ppe genes studied was consistent with lineage. Several recombination hotspots were identified, notably pe_pgrs3 and pe_pgrs17. Evidence of positive selection was revealed in 65 pe/ppe genes, including epitopes potentially binding to major histocompatibility complex molecules.ConclusionsThis, the first comprehensive study of the pe and ppe genes, provides important insight into M. tuberculosis diversity and has significant implications for vaccine development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2467-y) contains supplementary material, which is available to authorized users.

Pulmonary tuberculosis (TB) is characterized by oxidative stress and lung tissue destruction by matrix metalloproteinases (MMP). The interplay between these distinct pathological processes and the implications for TB diagnosis and disease staging are poorly understood. Heme oxygenase-1 (HO-1) levels have been shown to distinguish active from latent as well as successfully treated Mycobacterium tuberculosis (Mtb) infection. MMP-1 expression is also associated with active TB. Here, we measured plasma levels of these two important biomarkers in distinct TB cohorts from India and Brazil. Patients with active TB expressed either very high levels of HO-1 and low levels of MMP-1 or the converse. Moreover, TB patients with either high HO-1 or MMP-1 levels displayed distinct clinical presentations as well as plasma inflammatory marker profiles. In contrast, in an exploratory North American study, inversely correlated expression of HO-1 and MMP-1 was not observed in patients with other non-tuberculous lung diseases. To assess possible regulatory interactions in the biosynthesis of these two enzymes at the cellular level, we studied expression of HO-1 and MMP-1 in Mtb-infected human and murine macrophages. We found that infection of macrophages with live virulent Mtb is required for robust induction of high levels of HO-1, but not MMP-1. In addition, we observed that carbon monoxide, a product of Mtb induced HO-1 activity, inhibits MMP-1 expression by suppressing c-Jun/AP-1 activation. These findings reveal a mechanistic link between oxidative stress and tissue remodeling that may find applicability in the clinical staging of TB patients.

Considering that nitric oxide (NO) may be involved in anti-tumoral and anti-parasite lectin effects, in this report we investigated whether lectin induces NO production. Lectins from Canavalia brasiliensis, Dioclea grandiflora, Pisum arvense (PAA), and concanavalin A induced murine peritoneal cells to produce NO in vitro. PAA induced similar levels to that obtained with lipopolysaccharide plus interferon-gamma. NO production by adherent cells was significantly lower than that of unfractionated cells, suggesting a combination of lectin stimuli directly on macrophages and via lymphocyte stimulation. Ex vivo experiments showed that cells stimulated in vivo could maintain NO production in vitro without further stimuli. NO synthesis blockage in vivo can significantly increase cell numbers in draining lymph nodes after lectin injection compared to unblocked controls, suggesting an in vivo association of lectin stimuli and NO production. Taken together these data show that lectins can induce NO production both in vitro and in vivo.