Coordinate regulation of virulence and metabolic genes by the transcription factor HbhR in Mycobacterium marinum.

The heparin-binding hemagglutinin (HBHA) is a multifunctional protein involved in adherence of Mycobacterium tuberculosis to non-phagocytic cells and in the formation of intracytosolic lipid inclusions. We demonstrate that the expression of hbhA is regulated by a transcriptional repressor, named HbhR, in Mycobacterium marinum. The hbhR gene, located upstream of hbhA, was identified by screening a transposon insertion library and detailed analysis of a mutant overproducing HBHA.

Deciphering the molecular basis of mycobacteria and lipoglycan recognition by the C-type lectin Dectin-2.

Dectin-2 is a C-type lectin involved in the recognition of several pathogens such as Aspergillus fumigatus, Candida albicans, Schistosoma mansonii, and Mycobacterium tuberculosis that triggers Th17 immune responses. Identifying pathogen ligands and understanding the molecular basis of their recognition is one of the current challenges. Purified M.

Inorganic Phosphate Limitation Modulates Capsular Polysaccharide Composition in Mycobacteria.

Mycobacterium tuberculosis is protected by an unusual and highly impermeable cell envelope that is critically important for the successful colonization of the host. The outermost surface of this cell envelope is formed by capsular polysaccharides that play an important role in modulating the initial interactions once the bacillus enters the body. Although the bioenzymatic steps involved in the production of the capsular polysaccharides are emerging, information regarding the ability of the bacterium to modulate the composition of the capsule is still unknown.

Human Milk Blocks DC-SIGN-Pathogen Interaction via MUC1.

Beneficial effects of breastfeeding are well-recognized and include both immediate neonatal protection against pathogens and long-term protection against allergies and autoimmune diseases. Although several proteins have been identified to have anti-viral or anti-bacterial effects like secretory IgA or lactoferrin, the mechanisms of immune modulation are not fully understood. Recent studies identified important beneficial effects of glycans in human milk, such as those expressed in oligosaccharides or on glycoproteins.

A murine monoclonal antibody to glycogen: characterization of epitope-fine specificity by saturation transfer difference (STD) NMR spectroscopy and its use in mycobacterial capsular α-glucan research.

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a major pathogen responsible for 1.5 million deaths annually. This bacterium is characterized by a highly unusual and impermeable cell envelope, which plays a key role in mycobacterial survival and virulence.

Structure and function of RNase AS, a polyadenylate-specific exoribonuclease affecting mycobacterial virulence in vivo.

The cell-envelope of Mycobacterium tuberculosis plays a key role in bacterial virulence and antibiotic resistance. Little is known about the molecular mechanisms of regulation of cell-envelope formation. Here, we elucidate functional and structural properties of RNase AS, which modulates M.

Mannan core branching of lipo(arabino)mannan is required for mycobacterial virulence in the context of innate immunity.

The causative agent of tuberculosis (TB), Mycobacterium tuberculosis, remains an important worldwide health threat. Although TB is one of the oldest infectious diseases of man, a detailed understanding of the mycobacterial mechanisms underlying pathogenesis remains elusive. Here, we studied the role of the α(1→2) mannosyltransferase MptC in mycobacterial virulence, using the Mycobacterium marinum zebrafish infection model.

Lipoarabinomannan mannose caps do not affect mycobacterial virulence or the induction of protective immunity in experimental animal models of infection and have minimal impact on in vitro inflammatory responses.

Mannose-capped lipoarabinomannan (ManLAM) is considered an important virulence factor of Mycobacterium tuberculosis. However, while mannose caps have been reported to be responsible for various immunosuppressive activities of ManLAM observed in vitro, there is conflicting evidence about their contribution to mycobacterial virulence in vivo. Therefore, we used Mycobacterium bovis BCG and M.

Cyanovirin-N inhibits mannose-dependent Mycobacterium-C-type lectin interactions but does not protect against murine tuberculosis.

Cyanovirin-N (CV-N) is a mannose-binding lectin that inhibits HIV-1 infection by blocking mannose-dependent target cell entry via C-type lectins. Like HIV-1, Mycobacterium tuberculosis expresses mannosylated surface structures and exploits C-type lectins to gain cell access. In this study, we investigated whether CV-N, like HIV-1, can inhibit M.

ESX-5-deficient Mycobacterium marinum is hypervirulent in adult zebrafish.

ESX-5 is a mycobacterial type VII protein secretion system responsible for transport of numerous PE and PPE proteins. It is involved in the induction of host cell death and modulation of the cytokine response in vitro. In this work, we studied the effects of ESX-5 in embryonic and adult zebrafish using Mycobacterium marinum.

Lipoarabinomannan and related glycoconjugates: structure, biogenesis and role in Mycobacterium tuberculosis physiology and host-pathogen interaction.

Approximately one third of the world's population is infected with Mycobacterium tuberculosis, the causative agent of tuberculosis. This bacterium has an unusual lipid-rich cell wall containing a vast repertoire of antigens, providing a hydrophobic impermeable barrier against chemical drugs, thus representing an attractive target for vaccine and drug development. Apart from the mycolyl-arabinogalactan-peptidoglycan complex, mycobacteria possess several immunomodulatory constituents, notably lipomannan and lipoarabinomannan.

Mycobacterium marinum MMAR_2380, a predicted transmembrane acyltransferase, is essential for the presence of the mannose cap on lipoarabinomannan.

Lipoarabinomannan (LAM) is a major glycolipid in the mycobacterial cell envelope. LAM consists of a mannosylphosphatidylinositol (MPI) anchor, a mannan core and a branched arabinan domain. The termini of the arabinan branches can become substituted with one to three α(1→2)-linked mannosyl residues, the mannose cap, producing ManLAM.

Direct visualization by cryo-EM of the mycobacterial capsular layer: a labile structure containing ESX-1-secreted proteins.

The cell envelope of mycobacteria, a group of Gram positive bacteria, is composed of a plasma membrane and a Gram-negative-like outer membrane containing mycolic acids. In addition, the surface of the mycobacteria is coated with an ill-characterized layer of extractable, non-covalently linked glycans, lipids and proteins, collectively known as the capsule, whose occurrence is a matter of debate. By using plunge freezing cryo-electron microscopy technique, we were able to show that pathogenic mycobacteria produce a thick capsule, only present when the cells were grown under unperturbed conditions and easily removed by mild detergents.

A truncated lipoglycan from mycobacteria with altered immunological properties.

Maintenance of cell-wall integrity in Mycobacterium tuberculosis is essential and is the target of several antitubercular drugs. For example, ethambutol targets arabinogalactan and lipoarabinomannan (LAM) biosynthesis through the inhibition of several arabinofuranosyltransferases. Apart from their role in cell-wall integrity, mycobacterial LAMs also exhibit important immunomodulatory activities.

Identification of mycobacterial alpha-glucan as a novel ligand for DC-SIGN: involvement of mycobacterial capsular polysaccharides in host immune modulation.

Mycobacterium tuberculosis possesses a variety of immunomodulatory factors that influence the host immune response. When the bacillus encounters its target cell, the outermost components of its cell envelope are the first to interact. Mycobacteria, including M.

Role of phosphatidylinositol mannosides in the interaction between mycobacteria and DC-SIGN.

The C-type lectin dendritic cell (DC)-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) is the major receptor on DCs for mycobacteria of the Mycobacterium tuberculosis complex. Recently, we have shown that although the mannose caps of the mycobacterial surface glycolipid lipoarabinomannan (ManLAM) are essential for the binding to DC-SIGN, genetic removal of these caps did not diminish the interaction of whole mycobacteria with DC-SIGN and DCs. Here we investigated the role of the structurally related glycolipids phosphatidylinositol mannosides (PIMs) as possible ligands for DC-SIGN.

PPE and PE_PGRS proteins of Mycobacterium marinum are transported via the type VII secretion system ESX-5.

ESX-5 is one of the five type VII secretion systems found in mycobacteria. These secretion systems are also known as ESAT-6-like secretion systems. Here, we have determined the secretome of ESX-5 by a proteomic approach in two different strains of Mycobacterium marinum.

Antigenic mimicry of the HIV envelope by AIDS-associated pathogens.

Only one broadly neutralizing anti-HIV antibody, 2G12, recognises the envelope sugars of HIV. In the present study, we show that 2G12 also recognises Candida albicans and Candida tropicalis with high affinity (11 nmol/l) through a carbohydrate-dependent interaction (50% inhibitory concentration for D-fructose, 12 mmol/l). This is the first report of a neutralizing HIV antibody displaying cross-reactivity with another pathogen, revealing that the carbohydrate neutralization determinant of HIV, defined by 2G12, is more widespread amongst immunogenic, microbial surfaces than previously recognized.

Type VII secretion--mycobacteria show the way.

Recent evidence shows that mycobacteria have developed novel and specialized secretion systems for the transport of extracellular proteins across their hydrophobic, and highly impermeable, cell wall. Strikingly, mycobacterial genomes encode up to five of these transport systems. Two of these systems, ESX-1 and ESX-5, are involved in virulence - they both affect the cell-to-cell migration of pathogenic mycobacteria.

A specific secretion system mediates PPE41 transport in pathogenic mycobacteria.

Mycobacterial genomes contain two unique gene families, the so-called PE and PPE gene families, which are highly expanded in the pathogenic members of this genus. Here we report that one of the PPE proteins, i.e.

Variations in Helicobacter pylori lipopolysaccharide to evade the innate immune component surfactant protein D.

Helicobacter pylori is a common and persistent human pathogen of the gastric mucosa. Surfactant protein D (SP-D), a component of innate immunity, is expressed in the human gastric mucosa and is capable of aggregating H. pylori.

Carbohydrate specificities of the murine DC-SIGN homologue mSIGNR1.

C-type lectins are important receptors expressed by antigen presenting cells that are involved in cellular communications as well as in pathogen uptake. An important C-type lectin family is represented by DC-SIGN and its homologues in human and mouse. Here we have investigated the carbohydrate specificity of cellular mSIGNR1 and compared it with DC-SIGN and L-SIGN.

A multiplexed and miniaturized serological tuberculosis assay identifies antigens that discriminate maximally between TB and non-TB sera.

We have developed a multiplexed and miniaturized TB serological assay with the aim of identifying (combinations of) antigens that maximally discriminate between TB and non-TB patients. It features a microarray accommodating 54 TB antigens, less than 1 microl serum consumption and an indirect immunofluorescence detection protocol. With a panel of 20 TB and 80 non-TB sera we ranked combinations of TB antigens with respect to sensitivity and specificity of TB detection by means of logistic step-forward regression analysis.