Capsular Polysaccharides and Their Role in Virulence

Taylor, Craig; Roberts, Ian S.

doi:10.1159/000081689

Cited by 82 publications

(65 citation statements)

References 49 publications

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“…Polysaccharide capsules are expressed by many pathogenic bacteria and play an important role during infection (10,11). Although the presence of a capsule on mycobacteria was already recognized many decades ago (57), so far only a few studies have been aimed at investigating its function.…”

Section: Discussionmentioning

confidence: 99%

“…Compounds that are secreted across the mycomembrane are the polysaccharides that make up the outermost layer of the cell-envelope, that is, the capsule (7). Bacterial capsules are protective structures expressed by many pathogenic bacteria and have been shown to be important for the successful colonization of the host (10,11). The mycobacterial capsule is loosely attached to the surface and is mainly composed of proteins and polysaccharides (7).…”

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confidence: 99%

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Identification of Mycobacterial α-Glucan As a Novel Ligand for DC-SIGN: Involvement of Mycobacterial Capsular Polysaccharides in Host Immune Modulation

Geurtsen

Chedammi

Mesters

et al. 2009

The Journal of Immunology

117

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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. tuberculosis, are surrounded by a loosely attached capsule that is mainly composed of proteins and polysaccharides. Although the chemical composition of the capsule is relatively well studied, its biological function is only poorly understood. The aim of this study was to further assess the functional role of the mycobacterial capsule by identifying host receptors that recognize its constituents. We focused on α-glucan, which is the dominant capsular polysaccharide. Here we demonstrate that M. tuberculosis α-glucan is a novel ligand for the C-type lectin DC-SIGN (dendritic cell-specific ICAM-3-grabbing nonintegrin). By using related glycogen structures, we show that recognition of α-glucans by DC-SIGN is a general feature and that the interaction is mediated by internal glucosyl residues. As for mannose-capped lipoarabinomannan, an abundant mycobacterial cell wall-associated glycolipid, binding of α-glucan to DC-SIGN stimulated the production of immunosuppressive IL-10 by LPS-activated monocyte-derived dendritic cells. By using specific inhibitors, we show that this IL-10 induction was DC-SIGN-dependent and also required acetylation of NF-κB. Finally, we demonstrate that purified M. tuberculosis α-glucan, in contrast to what has been reported for fungal α-glucan, was unable to activate TLR2.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Identification of Mycobacterial α-Glucan As a Novel Ligand for DC-SIGN: Involvement of Mycobacterial Capsular Polysaccharides in Host Immune Modulation

Geurtsen

Chedammi

Mesters

et al. 2009

The Journal of Immunology

117

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“…The degree of virulence depends on several virulence factors (Price, 2008) which includes capsular polysaccharide (Taylor and Roberts, 2005;Lindberg et al, 1979), capsule, DNase, coagulase, fibrinolysin, proteolytic, haemolysin, bacteriocin production, haemagglutination, serum sensitivity, epithelial cells attachment, hydrophobicity (Avila-Campos et al, 2000), lipase, antiphagocytic factor, biofilm (Prasad et al, 2009), extracellular enzymes production, presence of surface layer, lysine decarboxylase production and pili, (Pin et al, 1997) etc. There are several in vivo and in vitro assays to determine these virulence factors (Calderone et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Virulence determination of bacterial isolates through culture in India ink including broth

Behera¹

2013

J. Microbiol. Antimicrob.

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Virulency is the degree of pathogenicity exhibited by most of the pathogens and it is a measure that effectively differentiates pathogenic and non-pathogenic strains. In the present study, culture of bacteria for 10 to 12 h (overnight) at 37°C in 10% India ink included broth that can be used as marker test for initial virulence identification while screening a number of bacterial isolates. These results were further confirmed by the in vivo virulence tests. Although, this is the first report, there is no clear explanation to the degradation of India ink by virulent bacteria which was obtained but this could act as a marker for initial screening of isolates for their virulence. Moreover, India ink is used as a suitable capsular stain and capsule act as a virulence factor for most of the bacteria. So virulence test by 10% India ink including broth acts as a simple, low cost and easy method for initial screening of virulent from non virulent strains.

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“…The capsule is often the outermost structure of a bacterial cell and therefore is critical for interactions with the environment. Depending on the organism, capsules assist bacteria in resisting desiccation, forming biofilms, colonizing host tissues, resisting bacteriophages, and reducing opsonophagocytosis and complement-mediated killing (2). In Salmonella enterica, the virulence capsular polysaccharide, known as "Vi antigen," is produced by human-restricted serovar Typhi (hereafter S. Typhi, the etiological agent of typhoid fever) and serovar Paratyphi C, but it is absent in other serovars commonly associated with gastroenteritis.…”

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confidence: 99%

Unique lipid anchor attaches Vi antigen capsule to the surface of Salmonella enterica serovar Typhi

Liston

Ovchinnikova

Whitfield

2016

Proc. Natl. Acad. Sci. U.S.A.

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Polysaccharide capsules are surface structures that are critical for the virulence of many Gram-negative pathogenic bacteria. Salmonella enterica serovar Typhi is the etiological agent of typhoid fever. It produces a capsular polysaccharide known as “Vi antigen,” which is composed of nonstoichiometrically O-acetylated α-1,4-linked N-acetylgalactosaminuronic acid residues. This glycan is a component of currently available vaccines. The genetic locus for Vi antigen production is also present in soil bacteria belonging to the genus Achromobacter. Vi antigen assembly follows a widespread general strategy with a characteristic glycan export step involving an ATP-binding cassette transporter. However, Vi antigen producers lack the enzymes that build the conserved terminal glycolipid characterizing other capsules using this method. Achromobacter species possess a Vi antigen-specific depolymerase enzyme missing in S. enterica Typhi, and we exploited this enzyme to isolate acylated Vi antigen termini. Mass spectrometry analysis revealed a reducing terminal N-acetylhexosamine residue modified with two β-hydroxyl acyl chains. This terminal structure resembles one half of lipid A, the hydrophobic portion of bacterial lipopolysaccharides. The VexE protein encoded in the Vi antigen biosynthesis locus shares similarity with LpxL, an acyltransferase from lipid A biosynthesis. In the absence of VexE, Vi antigen is produced, but its physical properties are altered, its export is impaired, and a Vi capsule structure is not assembled on the cell surface. The structure of the lipidated terminus dictates a unique assembly mechanism and has potential implications in pathogenesis and vaccine production.

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Capsular Polysaccharides and Their Role in Virulence

Cited by 82 publications

References 49 publications

Identification of Mycobacterial α-Glucan As a Novel Ligand for DC-SIGN: Involvement of Mycobacterial Capsular Polysaccharides in Host Immune Modulation

Identification of Mycobacterial α-Glucan As a Novel Ligand for DC-SIGN: Involvement of Mycobacterial Capsular Polysaccharides in Host Immune Modulation

Virulence determination of bacterial isolates through culture in India ink including broth

Unique lipid anchor attaches Vi antigen capsule to the surface of Salmonella enterica serovar Typhi

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