Publications by authors named "Mumtaz Virji"

34 Publications

spp. target human CEACAM1 via the trimeric autotransporter adhesin CbpF.

J Oral Microbiol 2019 24;11(1):1565043. Epub 2019 Jan 24.

School of Cellular & Molecular Medicine, University of Bristol, UK.

, and are pathogenic bacteria adapted to reside on human respiratory mucosal epithelia. One common feature of these species is their ability to target members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, especially CEACAM1, which is achieved via structurally distinct ligands expressed by each species. Beside respiratory epithelial cells, cells at the dentogingival junction express high levels of CEACAM1. It is possible that bacterial species resident within the oral cavity also utilise CEACAM1 for colonisation and invasion of gingival tissues. From a screen of 59 isolates from the human oral cavity representing 49 bacterial species, we identified strains from bound to CEACAM1. Of the species tested, the CEACAM1-binding property was exhibited by (Fn) and (Fv) but not (Fp) or (Fa) strains tested. These studies identified that CEACAM adhesion was mediated using a trimeric autotransporter adhesin (TAA) for which no function has thus far been defined. We therefore propose the name CEACAM binding protein of (CbpF). CbpF was identified to be present in the majority of unspeciated isolates confirming a subset of spp. are able to target human CEACAM1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/20002297.2018.1565043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6346709PMC
January 2019

Bioinformatic analysis of meningococcal Msf and Opc to inform vaccine antigen design.

PLoS One 2018 16;13(3):e0193940. Epub 2018 Mar 16.

School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom.

Neisseria meningitidis is an antigenically and genetically variable Gram-negative bacterium and a causative agent of meningococcal meningitis and septicaemia. Meningococci encode many outer membrane proteins, including Opa, Opc, Msf, fHbp and NadA, identified as being involved in colonisation of the host and evasion of the immune response. Although vaccines are available for the prevention of some types of meningococcal disease, none currently offer universal protection. We have used sequences within the Neisseria PubMLST database to determine the variability of msf and opc in 6,500 isolates. In-silico analysis revealed that although opc is highly conserved, it is not present in all isolates, with most isolates in clonal complex ST-11 lacking a functional opc. In comparison, msf is found in all meningococcal isolates, and displays diversity in the N-terminal domain. We identified 20 distinct Msf sequence variants (Msf SV), associated with differences in number of residues within the putative Vn binding motifs. Moreover, we showed distinct correlations with certain Msf SVs and isolates associated with either hyperinvasive lineages or those clonal complexes associated with a carriage state. We have demonstrated differences in Vn binding between three Msf SVs and generated a cross reactive Msf polyclonal antibody. Our study has highlighted the importance of using large datasets to inform vaccine development and provide further information on the antigenic diversity exhibited by N. meningitidis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193940PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5856348PMC
June 2018

Identification and therapeutic potential of a vitronectin binding region of meningococcal msf.

PLoS One 2015 31;10(3):e0124133. Epub 2015 Mar 31.

School of Cellular & Molecular Medicine, Medical Sciences Building, University Walk, University of Bristol, Bristol, BS8 ITD, United Kingdom.

The human pathogen Neisseria meningitides (Nm) attains serum resistance via a number of mechanisms, one of which involves binding to the host complement regulator protein vitronectin. We have shown previously that the Meningococcal surface fibril (Msf), a trimeric autotransporter, binds to the activated form of vitronectin (aVn) to increase Nm survival in human serum. In this study, we aimed to identify the aVn-binding region of Msf to assess its potential as an antigen which can elicit antibodies that block aVn binding and/or possess bactericidal properties. Using several recombinant Msf fragments spanning its surface-exposed region, the smallest aVn-binding recombinants were found to span residues 1-86 and 39-124. The use of further deletion constructs and overlapping recombinant Msf fragments suggested that a region of Msf comprising residues 39-82 may be primarily important for aVn binding and that other regions may also be involved but to a lesser extent. Molecular modelling implicated K66 and K68, conserved in all available Msf sequences, to be involved in the interaction. Recombinant fragments which bound to aVn were able to reduce the survival advantage conveyed by aVn-interaction in serum bactericidal assays. Antibodies raised against one such fragment inhibited aVn binding to Msf. In addition, the antibodies enhanced specific killing of Msf-expressing Nm in a dose-dependent manner. Overall, this study identifies an aVn-binding region of Msf, an adhesin known to impart serum resistance properties to the pathogen; and shows that this region of Msf can elicit antibodies with dual properties which reduce pathogen survival within the host and thus has potential as a vaccine antigen.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0124133PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4380367PMC
March 2016

Selection for a CEACAM receptor-specific binding phenotype during Neisseria gonorrhoeae infection of the human genital tract.

Infect Immun 2015 Apr 20;83(4):1372-83. Epub 2015 Jan 20.

Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada

Infections by Neisseria gonorrhoeae are increasingly common, are often caused by antibiotic-resistant strains, and can result in serious and lasting sequelae, prompting the reemergence of gonococcal disease as a leading global health concern. N. gonorrhoeae is a human-restricted pathogen that primarily colonizes urogenital mucosal surfaces. Disease progression varies greatly between the sexes: men usually present with symptomatic infection characterized by a painful purulent urethral discharge, while in women, the infection is often asymptomatic, with the most severe pathology occurring when the bacteria ascend from the lower genital tract into the uterus and fallopian tubes. Classical clinical studies demonstrated that clinically infectious strains uniformly express Opa adhesins; however, their specificities were unknown at the time. While in vitro studies have since identified CEACAM proteins as the primary target of Opa proteins, the gonococcal specificity for this human family of receptors has not been addressed in the context of natural infection. In this study, we characterize a collection of low-passage-number clinical-specimen-derived N. gonorrhoeae isolates for Opa expression and assess their CEACAM-binding profiles. We report marked in vivo selection for expression of phase-variable Opa proteins that bind CEACAM1 and CEACAM5 but selection against expression of Opa variants that bind to the neutrophil-restricted decoy receptor CEACAM3. This is the first study showing phenotypic selection for distinct CEACAM-binding phenotypes in vivo, and it supports the opposing functions of CEACAMs that facilitate infection versus driving inflammation within the genital tract.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363431PMC
http://dx.doi.org/10.1128/IAI.03123-14DOI Listing
April 2015

Moraxella catarrhalis adhesin UspA1-derived recombinant fragment rD-7 induces monocyte differentiation to CD14+CD206+ phenotype.

PLoS One 2014 5;9(3):e90999. Epub 2014 Mar 5.

School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom.

Circulating monocytes in the bloodstream typically migrate to other tissues and differentiate into tissue resident macrophages, the process being determined by the constituents of the microenvironments encountered. These may include microbes and their products. In this study, we investigated whether Moraxella catarrhalis Ubiquitous Surface Protein A1 (UspA1), known to bind to a widely expressed human cell surface receptor CEACAM1, influences monocyte differentiation as receptor engagement has been shown to have profound effects on monocytes. We used the recombinant molecules corresponding to the regions of UspA1 which either bind (rD-7; UspA1527-665) or do not bind (r6-8; UspA1659-863) to CEACAM1 and investigated their effects on CD206, CD80 and CD86 expression on freshly isolated human CD14+ monocytes from peripheral blood mononuclear cells (PBMC). Exposure to rD-7, but not r6-8, biased monocyte differentiation towards a CD14+CD206+ phenotype, with reduced CD80 expression. Monocytes treated with rD-7 also secreted high levels of IL-1ra and chemokine IL-8 but not IL-10 or IL-12p70. The effects of rD-7 were independent of any residual endotoxin. Unexpectedly, these effects of rD-7 were also independent of its ability to bind to CEACAM1, as monocyte pre-treatment with the anti-CEACAM antibody A0115 known to inhibit rD-7 binding to the receptor, did not affect rD-7-driven differentiation. Further, another control protein rD-7/D (a mutant form of rD-7, known not to bind to CEACAMs), also behaved as the parent molecule. Our data suggest that specific regions of M. catarrhalis adhesin UspA1 may modulate inflammation during infection through a yet unknown receptor on monocytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0090999PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3944954PMC
November 2014

A novel group of Moraxella catarrhalis UspA proteins mediates cellular adhesion via CEACAMs and vitronectin.

PLoS One 2012 25;7(9):e45452. Epub 2012 Sep 25.

School of Cellular & Molecular Medicine, University of Bristol, Bristol, United Kingdom.

Moraxella catarrhalis (Mx) is a common cause of otitis media and exacerbation of chronic obstructive pulmonary disease, an increasing worldwide problem. Surface proteins UspA1 and UspA2 of Mx bind to a number of human receptors and may function in pathogenesis. Genetic recombination events in the pathogen can generate hybrid proteins termed UspA2H. However, whether certain key functions (e.g. UspA1-specific CEACAM binding) can be exchanged between these adhesin families remains unknown. In this study, we have shown that Mx can incorporate the UspA1 CEACAM1-binding region not only into rare UspA1 proteins devoid of CEACAM-binding ability, but also into UspA2 which normally lack this capacity. Further, a screen of Mx isolates revealed the presence of novel UspA2 Variant proteins (UspA2V) in ∼14% of the CEACAM-binding population. We demonstrate that the expression of UspA2/2V with the CEACAM-binding domain enable Mx to bind both to cell surface CEACAMs and to integrins, the latter via vitronectin. Such properties of UspA2/2V have not been reported to date. The studies demonstrate that the UspA family is much more heterogeneous than previously believed and illustrate the in vivo potential for exchange of functional regions between UspA proteins which could convey novel adhesive functions whilst enhancing immune evasion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0045452PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458076PMC
April 2013

Involvement of the autophagy pathway in trafficking of Mycobacterium tuberculosis bacilli through cultured human type II epithelial cells.

Cell Microbiol 2012 Sep 25;14(9):1402-14. Epub 2012 May 25.

Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.

Interactions between Mycobacterium tuberculosis bacilli and alveolar macrophages have been extensively characterized, while similar analyses in epithelial cells have not been performed. In this study, we microscopically examined endosomal trafficking of M. tuberculosis strain Erdman in A549 cells, a human type II pneumocyte cell line. Immuno-electron microscopic (IEM) analyses indicate that M. tuberculosis bacilli are internalized to a compartment labelled first with Rab5 and then with Rab7 small GTPase proteins. This suggests that, unlike macrophages, M. tuberculosis bacilli traffic to late endosomes in epithelial cells. However, fusion of lysosomes with the bacteria-containing compartment appears to be inhibited, as illustrated by IEM studies employing LAMP-2 and cathepsin-L antibodies. Examination by transmission electron microscopy and IEM revealed M. tuberculosis-containing compartments surrounded by double membranes and labelled with antibodies against the autophagy marker Lc3, providing evidence for involvement and intersection of the autophagy and endosomal pathways. Interestingly, inhibition of the autophagy pathway using 3-methyladenine improved host cell viability and decreased numbers of viable intracellular bacteria recovered after 72 h post infection. Collectively, these data suggest that trafficking patterns for M. tuberculosis bacilli in alveolar epithelial cells differ from macrophages, and that autophagy is involved this process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2012.01804.xDOI Listing
September 2012

Meningococcal surface fibril (Msf) binds to activated vitronectin and inhibits the terminal complement pathway to increase serum resistance.

Mol Microbiol 2011 Dec 4;82(5):1129-49. Epub 2011 Nov 4.

Schools of Cellular & Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK.

Complement evasion is an important survival strategy of Neisseria meningitidis (Nm) during colonization and infection. Previously, we have shown that Nm Opc binds to serum vitronectin to inhibit complement-mediated killing. In this study, we demonstrate meningococcal interactions with vitronectin via a novel adhesin, Msf (meningococcal surface fibril, previously NhhA or Hsf). As with Opc, Msf binds preferentially to activated vitronectin (aVn), engaging at its N-terminal region but the C-terminal heparin binding domain may also participate. However, unlike Opc, the latter binding is not heparin-mediated. By binding to aVn, Msf or Opc can impart serum resistance, which is further increased in coexpressers, a phenomenon dependent on serum aVn concentrations. The survival fitness of aVn-binding derivatives was evident from mixed population studies, in which msf/opc mutants were preferentially depleted. In addition, using vitronectin peptides to block Msf-aVn interactions, aVn-induced inhibition of lytic C5b-9 formation and of serum killing could be reversed. As Msf-encoding gene is ubiquitous in the meningococcal strains examined and is expressed in vivo, serum resistance via Msf may be of significance to meningococcal pathogenesis. The data imply that vitronectin binding may be an important strategy for the in vivo survival of Nm for which the bacterium has evolved redundant mechanisms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-2958.2011.07876.xDOI Listing
December 2011

Meningococcal ligands and molecular targets of the host.

Methods Mol Biol 2012 ;799:143-52

School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.

Meningococcal mechanisms of adhesion are complex, involving multiple adhesins and their respective target receptors on host cells. Three major surface structures--pili, Opa, and Opc--have been known for some time to mediate meningococcal adhesion to target human cells. More recently, several other relatively minor adhesins have also come to light. The literature on bacterial adhesion mechanisms provides numerous examples of various adhesins acting cooperatively in an apparently hierarchical and sequential manner; in other instances, adhesins may act in concert leading to high avidity interactions, often a prelude to cellular invasion and tissue penetration. Such examples are also present in the case of meningococci, although our knowledge of adhesin cooperation and synergy is far from complete. Meningococcal mechanisms used to target the host, which are often specific for the host or a tissue within the host, include both lectin-like interactions and protein-protein interactions; the latter tend to determine specificity in general. Understanding (a) what determines specificity (i.e. molecular features of adhesins and receptors), (b) encourages cellular penetration (i.e. adhesin pairs, which act in concert or synergistically to deliver effective signals for invasion and induce other cellular responses), (c) level of redundancy (more than one mechanisms of targeting host receptors), (d) host situations that encourage tissue penetration (inflammatory situations during which circulating cytokines upregulate target cell receptors, effectively encouraging greater adhesion/invasion), and (e) down-stream effects on host functions in general are all clearly important in our future strategies of controlling meningococcal pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-61779-346-2_9DOI Listing
February 2012

Correlation of in situ mechanosensitive responses of the Moraxella catarrhalis adhesin UspA1 with fibronectin and receptor CEACAM1 binding.

Proc Natl Acad Sci U S A 2011 Sep 29;108(37):15174-8. Epub 2011 Aug 29.

School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom.

Bacterial cell surfaces are commonly decorated with a layer formed from multiple copies of adhesin proteins whose binding interactions initiate colonization and infection processes. In this study, we investigate the physical deformability of the UspA1 adhesin protein from Moraxella catarrhalis, a causative agent of middle-ear infections in humans. UspA1 binds a range of extracellular proteins including fibronectin, and the epithelial cellular receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Electron microscopy indicates that unliganded UspA1 is densely packed at, and extends about 800 Å from, the Moraxella surface. Using a modified atomic force microscope, we show that the adhesive properties and thickness of the UspA1 layer at the cell surface varies on addition of either fibronectin or CEACAM1. This in situ analysis is then correlated with the molecular structure of UspA1. To provide an overall model for UspA1, we have determined crystal structures for two N-terminal fragments which are then combined with a previous structure of the CEACAM1-binding site. We show that the UspA1-fibronectin complex is formed between UspA1 head region and the 13th type-III domain of fibronectin and, using X-ray scattering, that the complex involves an angular association between these two proteins. In combination with a previous study, which showed that the CEACAM1-UspA1 complex is distinctively bent in solution, we correlate these observations on isolated fragments of UspA1 with its in situ response on the cell surface. This study therefore provides a rare direct demonstration of protein conformational change at the cell surface.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1106341108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3174611PMC
September 2011

Visualisation and quantification of intracellular interactions of Neisseria meningitidis and human α-actinin by confocal imaging.

J Vis Exp 2010 Oct 24(44). Epub 2010 Oct 24.

Department of Cellular and Molecular Medicine, University of Bristol, UK.

The Opc protein of Neisseria meningitidis (Nm, meningococcus) is a surface-expressed integral outer membrane protein, which can act as an adhesin and an effective invasin for human epithelial and endothelial cells. We have identified endothelial surface-located integrins as major receptors for Opc, a process which requires Opc to first bind to integrin ligands such as vitronectin and via these to the cell-expressed receptors(1). This process leads to bacterial invasion of endothelial cells(2). More recently, we observed an interaction of Opc with a 100 kDa protein found in whole cell lysates of human cells(3). We initially observed this interaction when host cell proteins separated by electrophoresis and blotted on to nitrocellulose were overlaid with Opc-expressing Nm. The interaction was direct and did not involve intermediate molecules. By mass spectrometry, we established the identity of the protein as α-actinin. As no surface expressed α-actinin was found on any of the eight cell lines examined, and as Opc interactions with endothelial cells in the presence of serum lead to bacterial entry into the target cells, we examined the possibility of the two proteins interacting intracellularly. For this, cultured human brain microvascular endothelial cells (HBMECs) were infected with Opc-expressing Nm for extended periods and the locations of internalised bacteria and α-actinin were examined by confocal microscopy. We observed time-dependent increase in colocalisation of Nm with the cytoskeletal protein, which was considerable after an eight hour period of bacterial internalisation. In addition, the use of quantitative imaging software enabled us to obtain a relative measure of the colocalisation of Nm with α-actinin and other cytoskeletal proteins. Here we present a protocol for visualisation and quantification of the colocalisation of the bacterium with intracellular proteins after bacterial entry into human endothelial cells, although the procedure is also applicable to human epithelial cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3791/2045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3185616PMC
October 2010

Neisseria meningitidis Opc invasin binds to the sulphated tyrosines of activated vitronectin to attach to and invade human brain endothelial cells.

PLoS Pathog 2010 May 20;6(5):e1000911. Epub 2010 May 20.

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol, UK.

The host vasculature is believed to constitute the principal route of dissemination of Neisseria meningitidis (Nm) throughout the body, resulting in septicaemia and meningitis in susceptible humans. In vitro, the Nm outer membrane protein Opc can enhance cellular entry and exit, utilising serum factors to anchor to endothelial integrins; but the mechanisms of binding to serum factors are poorly characterised. This study demonstrates that Nm Opc expressed in acapsulate as well as capsulate bacteria can increase human brain endothelial cell line (HBMEC) adhesion and entry by first binding to serum vitronectin and, to a lesser extent, fibronectin. This study also demonstrates that Opc binds preferentially to the activated form of human vitronectin, but not to native vitronectin unless the latter is treated to relax its closed conformation. The direct binding of vitronectin occurs at its Connecting Region (CR) requiring sulphated tyrosines Y(56) and Y(59). Accordingly, Opc/vitronectin interaction could be inhibited with a conformation-dependent monoclonal antibody 8E6 that targets the sulphotyrosines, and with synthetic sulphated (but not phosphorylated or unmodified) peptides spanning the vitronectin residues 43-68. Most importantly, the 26-mer sulphated peptide bearing the cell-binding domain (45)RGD(47) was sufficient for efficient meningococcal invasion of HBMECs. To our knowledge, this is the first study describing the binding of a bacterial adhesin to sulphated tyrosines of the host receptor. Our data also show that a single region of Opc is likely to interact with the sulphated regions of both vitronectin and of heparin. As such, in the absence of heparin, Opc-expressing Nm interact directly at the CR but when precoated with heparin, they bind via heparin to the heparin-binding domain of the activated vitronectin, although with a lower affinity than at the CR. Such redundancy suggests the importance of Opc/vitronectin interaction in meningococcal pathogenesis and may enable the bacterium to harness the benefits of the physiological processes in which the host effector molecule participates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/journal.ppat.1000911DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2873925PMC
May 2010

Cellular and molecular biology of Neisseria meningitidis colonization and invasive disease.

Clin Sci (Lond) 2010 Feb 9;118(9):547-64. Epub 2010 Feb 9.

Department of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK.

The human species is the only natural host of Neisseria meningitidis, an important cause of bacterial meningitis globally, and, despite its association with devastating diseases, N. meningitidis is a commensal organism found frequently in the respiratory tract of healthy individuals. To date, antibiotic resistance is relatively uncommon in N. meningitidis isolates but, due to the rapid onset of disease in susceptible hosts, the mortality rate remains approx. 10%. Additionally, patients who survive meningococcal disease often endure numerous debilitating sequelae. N. meningitidis strains are classified primarily into serogroups based on the type of polysaccharide capsule expressed. In total, 13 serogroups have been described; however, the majority of disease is caused by strains belonging to one of only five serogroups. Although vaccines have been developed against some of these, a universal meningococcal vaccine remains a challenge due to successful immune evasion strategies of the organism, including mimicry of host structures as well as frequent antigenic variation. N. meningitidis express a range of virulence factors including capsular polysaccharide, lipopolysaccharide and a number of surface-expressed adhesive proteins. Variation of these surface structures is necessary for meningococci to evade killing by host defence mechanisms. Nonetheless, adhesion to host cells and tissues needs to be maintained to enable colonization and ensure bacterial survival in the niche. The aims of the present review are to provide a brief outline of meningococcal carriage, disease and burden to society. With this background, we discuss several bacterial strategies that may enable its survival in the human respiratory tract during colonization and in the blood during infection. We also examine several known meningococcal adhesion mechanisms and conclude with a section on the potential processes that may operate in vivo as meningococci progress from the respiratory niche through the blood to reach the central nervous system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1042/CS20090513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2830671PMC
February 2010

Opa+ and Opa- isolates of Neisseria meningitidis and Neisseria gonorrhoeae induce sustained proliferative responses in human CD4+ T cells.

Infect Immun 2009 Nov 31;77(11):5170-80. Epub 2009 Aug 31.

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol, United Kingdom.

T cells may interact with a number of bacterial surface antigens, an encounter which has the potential to downmodulate host immune responses. Neisseria meningitidis, a human colonizer and an agent of septicemia and meningitis, expresses Opa proteins which interact with the CEACAM1 receptor expressed on activated T cells. Since CEACAM1 can act as an inhibitory receptor and T cells in subepithelial tissues may encounter whole bacteria, which often express Opa proteins in vivo, this study assessed primarily if Opa proteins expressed on meningococci affect T-cell functions. In addition, Opa-containing outer membrane vesicles (OMV) have been used as vaccine antigens, and therefore Opa+ and Opa- OMV were also studied. While Opa+ bacteria adhered to CEACAM-expressing T cells, both the Opa+ and Opa- phenotypes induced no to a small transient depression, followed by a prolonged increase in proliferation as well as cytokine production. Such responses were also observed with heat-killed bacteria or OMV. In addition, while anti-CEACAM antibodies alone inhibited proliferation, on coincubation of T cells with bacteria and the antibodies, bacterial effects predominated and were Opa independent. Thus, while Opa proteins of N. meningitidis can bind to T-cell-expressed CEACAM1, this is not sufficient to overcome the T-cell recognition of bacterial factors, which results in a proliferative and cytokine response, an observation consistent with the ability of the host to establish lasting immunity to Opa-expressing meningococci that it frequently encounters. The data also imply that Opa-proficient vaccine preparations may not necessarily inhibit T-cell functions via CEACAM1 binding.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/IAI.00355-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2772550PMC
November 2009

Meningococcal interactions with the host.

Vaccine 2009 Jun 28;27 Suppl 2:B78-89. Epub 2009 May 28.

INSERM, unité 570, Université Paris Descartes, 156 rue de Vaugirard, Paris 75015, France.

Neisseria meningitidis interacts with host tissues through hierarchical, concerted and co-ordinated actions of a number of adhesins; many of which undergo antigenic and phase variation, a strategy that helps immune evasion. Three major structures, pili, Opa and Opc predominantly influence bacterial adhesion to host cells. Pili and Opa proteins also determine host and tissue specificity while Opa and Opc facilitate efficient cellular invasion. Recent studies have also implied a role of certain adhesin-receptor pairs in determining increased host susceptibility to infection. This chapter examines our current knowledge of meningococcal adhesion and invasion mechanisms particularly related to human epithelial and endothelial cells which are of primary importance in the disease process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vaccine.2009.04.069DOI Listing
June 2009

Pathogenic neisseriae: surface modulation, pathogenesis and infection control.

Authors:
Mumtaz Virji

Nat Rev Microbiol 2009 Apr;7(4):274-86

Department of Cellular and Molecular Medicine, School of Medical Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK.

Although renowned as a lethal pathogen, Neisseria meningitidis has adapted to be a commensal of the human nasopharynx. It shares extensive genetic and antigenic similarities with the urogenital pathogen Neisseria gonorrhoeae but displays a distinct lifestyle and niche preference. Together, they pose a considerable challenge for vaccine development as they modulate their surface structures with remarkable speed. Nonetheless, their host-cell attachment and invasion capacity is maintained, a property that could be exploited to combat tissue infiltration. With the primary focus on N. meningitidis, this Review examines the known mechanisms used by these pathogens for niche establishment and the challenges such mechanisms pose for infection control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nrmicro2097DOI Listing
April 2009

Ins and outs of microbial adhesion.

Authors:
Mumtaz Virji

Top Curr Chem 2009 ;288:139-56

Department of Cellular and Molecular Medicine School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK,

Microbial adhesion is generally a complex process, involving multiple adhesins on a single microbe and their respective target receptors on host cells. In some situations, various adhesins of a microbe may co-operate in an apparently hierarchical and sequential manner whereby the first adhesive event triggers the target cell to express receptors for additional microbial adhesins. In other instances, adhesins may act in concert leading to high avidity interactions, often a prelude to cellular invasion and tissue penetration. Mechanisms used to target the host include both lectin-like interactions and protein-protein interactions; the latter are often highly specific for the host or a tissue within the host. This reflective chapter aims to offer a point of view on microbial adhesion by presenting some experiences and thoughts especially related to respiratory pathogens and explore if there can be any future hope of controlling bacterial infections via preventing adhesion or invasion stages of microbial pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/128_2008_15DOI Listing
October 2012

Nontypeable Haemophilus influenzae as a pathogen in children.

Pediatr Infect Dis J 2009 Jan;28(1):43-8

University at Buffalo, the State University of New York, Buffalo, NY.

Nontypeable Haemophilus influenzae is a significant pathogen in children, causing otitis media, sinusitis, conjunctivitis, pneumonia, and occasionally invasive infections. H. influenzae type b conjugate vaccines have no effect on infections caused by nontypeable strains because nontypeable strains are nonencapsulated. Approximately, one-third of episodes of otitis media are caused by nontypeable H. influenzae and the bacterium is the most common cause of recurrent otitis media. Recent progress in elucidating molecular mechanisms of pathogenesis, understanding the role of biofilms in otitis media and an increasing understanding of immune responses have potential for development of novel strategies to improve prevention and treatment of otitis media caused by nontypeable H. influenzae. Feasibility of vaccination for prevention of otitis media due to nontypeable H. influenzae was recently demonstrated in a clinical trial with a vaccine that included the surface virulence factor, protein D.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/INF.0b013e318184dba2DOI Listing
January 2009

Neisseria meningitidis Opc invasin binds to the cytoskeletal protein alpha-actinin.

Cell Microbiol 2009 Mar 7;11(3):389-405. Epub 2008 Nov 7.

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol, UK.

Neisseria meningitidis Opc protein is an effective invasin for human endothelial cells. We have investigated novel human endothelial receptors targeted by Opc and observed that Opc-expressing bacteria interacted with a 100 kDa protein in whole-cell lysates of human endothelial and epithelial cells. The identity of the protein was established as alpha-actinin by mass spectrometry. Opc expression was essential for the recognition of alpha-actinin whether provided in a purified form or in cell extracts. The interaction of the two proteins did not involve intermediate molecules. As there was no demonstrable expression of alpha-actinin on the surfaces of any of the eight cell lines studied, the likelihood of the interactions after meningococcal internalization was examined. Confocal imaging demonstrated considerable colocalization of N. meningitidis with alpha-actinin especially after a prolonged period of internalization. This may imply that bacteria and alpha-actinin initially occur in separate compartments and co-compartmentalization occurs progressively over the 8 h infection period used. In conclusion, these studies have identified a novel and an intracellular target for the N. meningitidis Opc invasin. Since alpha-actinin is a modulator of a variety of signalling pathways and of cytoskeletal functions, its targeting by Opc may enable bacteria to survive/translocate across endothelial barriers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2008.01262.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2688670PMC
March 2009

The Moraxella adhesin UspA1 binds to its human CEACAM1 receptor by a deformable trimeric coiled-coil.

EMBO J 2008 Jun 22;27(12):1779-89. Epub 2008 May 22.

Department of Biochemistry, University of Bristol, Bristol, UK.

Moraxella catarrhalis is a ubiquitous human-specific bacterium commonly associated with upper and lower respiratory tract infections, including otitis media, sinusitis and chronic obstructive pulmonary disease. The bacterium uses an autotransporter protein UspA1 to target an important human cellular receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Using X-ray crystallography, we show that the CEACAM1 receptor-binding region of UspA1 unusually consists of an extended, rod-like left-handed trimeric coiled-coil. Mutagenesis and binding studies of UspA1 and the N-domain of CEACAM1 have been used to delineate the interacting surfaces between ligand and receptor and guide assembly of the complex. However, solution scattering, molecular modelling and electron microscopy analyses all indicate that significant bending of the UspA1 coiled-coil stalk also occurs. This explains how UspA1 can engage CEACAM1 at a site far distant from its head group, permitting closer proximity of the respective cell surfaces during infection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/emboj.2008.101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2396876PMC
June 2008

Characterization of epithelial IL-8 response to inflammatory bowel disease mucosal E. coli and its inhibition by mesalamine.

Inflamm Bowel Dis 2008 Feb;14(2):162-75

Division of Gastroenterology, University School of Clinical Science, Liverpool, UK.

Background: Mucosally adherent E. coli are found in inflammatory bowel disease (IBD) and colon cancer. They promote release of the proinflammatory cytokine interleukin-8 (IL-8). We explored mechanisms for this release and its inhibition by drugs.

Methods: IL-8 release from colon epithelial cells in response to mucosal E. coli isolates from IBD, colon cancer, and controls was characterized at the cellular and molecular level.

Results: IL-8 response of HT29 cells was greater with Crohn's disease (689 +/- 298 [mean +/- SD] pg IL-8/mL at 4 hours, n = 7) and colon cancer isolates (532 +/- 415 pg/mL, n = 14) than with ulcerative colitis (236 +/- 58 pg/mL, n = 6) or control isolates (236 +/- 100 pg/mL, n = 6, P < 0.0001). Bacterial supernatants contained shed flagellin that triggered IL-8 release. For whole bacteria the IL-8 response to E. coli that agglutinate red blood cells (548 +/- 428 pg IL-8/mL, n = 16), a function that correlates with epithelial invasion, was greater than for nonhemagglutinators (281 +/- 253 pg/mL, n = 17; P < 0.0001). This was particularly marked among E. coli that, although flagellate, could not release IL-8 from TLR5-transfected HEK293 cells. IL-8 release was mediated by extracellular-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) and inhibited by mesalamine, but not hydrocortisone, at therapeutic concentrations.

Conclusions: Mucosa-associated E. coli shed flagellin that elicits epithelial IL-8 release but this may only become relevant when the mucosal barrier is weakened to expose basolateral TLR5. Adherent and invasive IBD and colon cancer E. coli isolates also elicit a flagellin-independent IL-8 response that may be relevant when the mucosal barrier is intact. The IL-8 release is MAPK-dependent and inhibited by mesalamine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ibd.20296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7108638PMC
February 2008

IFN-gamma amplifies NFkappaB-dependent Neisseria meningitidis invasion of epithelial cells via specific upregulation of CEA-related cell adhesion molecule 1.

Cell Microbiol 2007 Dec 30;9(12):2968-83. Epub 2007 Aug 30.

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK.

Temporal relationship between viral and bacterial infections has been observed, and may arise via the action of virus-induced inflammatory cytokines. These, by upregulating epithelial receptors targeted by bacteria, may encourage greater bacterial infiltration. In this study, human epithelial cells exposed to interferon-gamma but not tumour necrosis factor-alpha or interleukin 1-beta supported increased meningococcal adhesion and invasion. The increase was related to Opa but not Opc or pili adhesin expression. De novo synthesis of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a major Opa receptor, occurred in epithelial cells exposed to the cytokine, or when infected with Opa-expressing bacteria. Cell line-dependent differences in invasion that were observed could be correlated with CEACAM expression levels. There was also evidence for Opa/pili synergism leading to high levels of monolayer infiltration by capsulate bacteria. The use of nuclear factor-kappa B (NFkappaB) inhibitors, diferuloylmethane (curcumin) and SN50, abrogated bacterial infiltration of both untreated and interferon-gamma-treated cells. The studies demonstrate the importance of CEACAMs as mediators of increased cellular invasion under conditions of inflammation and bring to light the potential role of NFkappaB pathway in Opa-mediated invasion by meningococci. The data imply that cell-surface remodelling by virally induced cytokines could be one factor that increases host susceptibility to bacterial infection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2007.01038.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3020365PMC
December 2007

Mutational analysis of human CEACAM1: the potential of receptor polymorphism in increasing host susceptibility to bacterial infection.

Cell Microbiol 2007 Feb 31;9(2):329-46. Epub 2006 Aug 31.

Department of Cellular and Molecular Medicine, University of Bristol, Bristol, BS8 1TD, UK.

A common overlapping site on the N-terminal IgV-like domain of human carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) is targeted by several important human respiratory pathogens. These include Neisseria meningitidis (Nm) and Haemophilus influenzae (Hi) that can cause disseminated or persistent localized infections. To define the precise structural features that determine the binding of distinct pathogens with CEACAMs, we have undertaken molecular modelling and mutation of the receptor molecules at previously implicated key target residues required for bacterial binding. These include Ser-32, Tyr-34, Val-39, Gln-44 and Gln-89, in addition to Ile-91, the primary docking site for the pathogens. Most, but not all, of these residues located adjacent to each other in a previous N-domain model of human CEACAM1, which was based on REI, CD2 and CD4. In the current studies, we have refined this model based on the mouse CEACAM1 crystal structure, and observe that all of the above residues form an exposed continuous binding region on the N-domain. Examination of the model also suggested that substitution of two of these residues 34 and 89 could affect the accessibility of Ile-91 for ligand binding. By introducing selected mutations at the positions 91, 34 and 89, we confirmed the primary importance of Ile-91 in all bacterial binding to CEACAM1 despite the inter- and intraspecies structural differences between the bacterial CEACAM-binding ligands. The studies further indicated that the efficiency of binding was significantly enhanced for specific strains by mutations such as Y34F and Q89N, which also altered the hierarchy of Nm versus Hi strain binding. These studies imply that distinct polymorphisms in human epithelial CEACAMs have the potential to decrease or increase the risk of infection by the receptor-targeting pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2006.00789.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1859983PMC
February 2007

Co-ordinate action of bacterial adhesins and human carcinoembryonic antigen receptors in enhanced cellular invasion by capsulate serum resistant Neisseria meningitidis.

Cell Microbiol 2007 Jan 2;9(1):154-68. Epub 2006 Aug 2.

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.

Neisseria meningitidis (Nm) is a human specific opportunistic pathogen that occasionally penetrates mucosal barriers via the action of adhesins and invasins and evades host immune mechanisms during further dissemination via capsule expression. From in vitro studies, the primary adhesion of capsulate bacteria is believed to be mediated by polymeric pili, followed by invasion via outer membrane adhesins such as Opa proteins. As the latter requires the surface capsule to be down-modulated, invading bacteria would be serum sensitive and thus avirulent. However, there is recent evidence that capsulate bacteria may interact via Opa proteins when host cells express high levels of carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), their target receptors. Such a situation may arise following increased circulation of inflammatory cytokines that upregulate certain adhesion molecules on host cells. In this study, using a tetracycline controlled expression system, we have developed cell lines with inducible CEACAM expression to mimic post-inflammation state of target tissues and analysed the interplay between the three surface components capsule, pili and Opa proteins in cellular interactions. With two distinct cell lines, not only the level but also the rate of adhesion of capsulate Opa-expressing Nm increased concurrently with CEACAM density. Moreover, when threshold levels of receptor were reached, cellular invasion ensued in an Opa-dependent manner. In studies with cell lines intrinsically expressing pilus receptors, notable synergism in cellular interactions between pili and Opa of several meningococcal strains was observed and was independent of capsule type. A number of internalized bacteria were shown to express capsule and when directly isolated from host cells, these bacteria were as serum resistant as the inoculated phenotype. Furthermore, we observed that agents that block Opa-CEACAM binding substantially reduced cellular invasion, while maintaining a low level of cellular adhesion. These studies highlight some of the factors that may determine increased host susceptibility to infection by serum resistant phenotypes; and demonstrate the potential of selective inhibition of key interactions in preventing target tissue penetration while maintaining a level of colonization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2006.00775.xDOI Listing
January 2007

Limited sampling strategy for cyclosporine (Neoral) area under the curve monitoring in pediatric kidney transplant recipients.

Pediatr Transplant 2005 Oct;9(5):566-73

The British Columbia Transplant Society, Vancouver, British Columbia, Canada.

Cyclosporine (CSA; Neoral) is one of the most common immunosuppressants used in pediatric renal transplantation. Research in adult renal transplant recipients has shown that 2-h post-dose concentration (C2) monitoring and limited sampling strategies (LSSs) are better at predicting drug exposure and outcome than trough concentrations (C0). While C0 monitoring is the usual practice in pediatric renal transplant patients, area under the curve (AUC) monitoring has been shown to be superior in terms of predictive ability and outcomes. However, AUC monitoring is impractical and inconvenient in a clinic setting because it involves many blood samples. An LSS provides a reliable alternative. The purpose of this study was to prospectively define an LSS (AUC(0-12)) for CSA monitoring and to test its predictive performance. As well, an LSS (AUC(0-4)) for CSA was developed and its predictive performance tested. Blood samples for CSA concentrations were collected in 29 stable pediatric renal transplant patients prior to (t = 0) and at 0.5, 1, 2, 4, 6, and 8 h following a steady-state morning CSA dose. AUC was calculated by the trapezoidal method; LSSs for AUC(0-12) and AUC(0-4) were determined using multiple regression analysis in 14 patients; and the LSSs' predictive performance was tested in 15 additional patients. Both LSSs require two blood samples. For the LSS (AUC(0-12)), blood samples are required immediately before the dose and 2 h post-dose: AUC(0-12) = 12.45 C0 + 2.17 C2 + 723.16 (r2 = 0.909). For the LSS (AUC(0-4)), blood samples are required at one and 2 h post-dose, AUC(0-4) = 1.17 C1 + 1.85 C2 - 41.00 (r2 = 0.971). The LSSs demonstrated low bias and high precision for both AUC(0-12) and AUC(0-4). Our two-concentration LSSs are accurate and precise predictors that are more clinically useful for our patient population than other LSSs that have been developed for pediatric renal transplant patients. Our study template provides a guide for other centers to develop accurate and precise LSSs specific to their own patient population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1399-3046.2005.00339.xDOI Listing
October 2005

Critical determinants of the interactions of capsule-expressing Neisseria meningitidis with host cells: the role of receptor density in increased cellular targeting via the outer membrane Opa proteins.

Cell Microbiol 2005 Oct;7(10):1490-503

Department of Pathology and Microbiology, School of Medical Sciences, University of Bristol, UK.

Neisseria meningitidis capsule is an important virulence determinant required for survival in the blood but is reportedly involved in inhibiting cellular interactions mediated by meningococcal outer membrane adhesins. However, evidence from our previous studies suggested that target receptor density on host cells may determine whether or not capsulate bacteria can adhere via outer membrane proteins such as Opa. To confirm this and evaluate the impact of capsulation on bacterial interactions, we used Opa(+) and Opa(-) derivatives of capsulate and acapsulate meningococcal isolates and transfected cell lines expressing CEACAM1, a receptor targeted by Opa proteins. To assess the extent and rate of cell association, subpopulations of stably transfected Chinese hamster ovary cells with different receptor levels were derived. A quantitative correlation of CEACAM1 levels and Opa-dependent binding of both capsulate and acapsulate bacteria was demonstrated, which was accelerated at high receptor densities. However, it appears that invasion by Opa(+) capsulate bacteria only occurs when a threshold level of CEACAM density has been reached. Target cells expressing high levels of CEACAM1 (MFI c. 400) bound threefold more, but internalized 20-fold more Opa(+) capsulate bacteria than those with intermediate expression (MFI c. 100). No overall selection of acapsulate phenotype was observed in the internalized population. These observations confirm that capsule may not be an adequate barrier for cellular interactions and demonstrate the role of a host factor that may determine capsulate bacterial invasion potential. Upregulation of CEACAMs, which can occur in response to inflammatory cytokines, could lead to translocation of a small number of fully capsulate bacteria across mucosal epithelium into the bloodstream sufficient to cause a rapid onset of disseminated disease. Thus the data also suggest a novel rationale for the epidemiological observations that individuals with prior infectious/inflammatory conditions carry a high risk of invasive meningococcal disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1462-5822.2005.00572.xDOI Listing
October 2005

Recognition of saccharides by the OpcA, OpaD, and OpaB outer membrane proteins from Neisseria meningitidis.

J Biol Chem 2005 Sep 8;280(36):31489-97. Epub 2005 Jul 8.

Faculty of Life Sciences, University of Manchester, Manchester, M60 1QD United Kingdom.

The adhesion of the pathogen Neisseria meningitidis to host cell surface proteoglycan, mediated by the integral outer membrane proteins OpcA and Opa, plays an important part in the processes of colonization and invasion by the bacterium. The precise specificities of the OpcA and Opa proteins are, however, unknown. Here we use a fluorescence-based binding assay to show that both proteins bind to mono- and disaccharides with high affinity. Binding of saccharides caused a quench in the intrinsic fluorescence emission of both proteins, and mutation of selected Tyr residues within the external loop regions caused a substantial decrease in fluorescence. We suggest that the intrinsic fluorescence arises from resonance energy transfer from Tyr to Trp residues in the beta-barrel portion of the structure. OpcA bound sialic acid with a Kd of 0.31 microM and was shown to be specific for pyranose saccharides. The binding specificities of two different Opa proteins were compared; unlike OpcA, neither protein bound to monosaccharides, but both bound to maltose, lactose, and sialic acid-containing oligosaccharides, with Kd values in the micromolar range. OpaB had a 10-fold higher affinity for sialic acid-containing ligands than OpaD as a result of the mutation Y165V, which was shown to restore this specificity to OpaD. Finally, the OpcA- and Opa-dependent adhesion of meningococci to epithelial cells was shown to be partially inhibited by exogenously added sialic acid and maltose. The results show that OpcA and the Opa proteins can be thought of as outer membrane lectins and that simple saccharides can modulate their recognition of complex proteoglycan receptors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M506354200DOI Listing
September 2005

Carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-binding recombinant polypeptide confers protection against infection by respiratory and urogenital pathogens.

Mol Microbiol 2005 Mar;55(5):1515-27

Department of Pathology and Microbiology, University of Bristol, Bristol, BS8 1TD, UK.

The human-specific pathogens Neisseria meningitidis, N. gonorrhoea, Haemophilus influenzae and Moraxella catarrhalis share the property of targeting the carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) expressed on human epithelia. CEACAMs are signalling receptors implicated in cell adhesion and regulation of several physiological functions. Their targeting by pathogens can lead to tissue invasion. Although the CEACAM-binding ligands of the bacteria are structurally diverse, they target a common site on the receptor. We have generated a recombinant polypeptide that blocks the interactions of the mucosal pathogens with human epithelial cells and antibodies against it inhibit M. catarrhalis interactions with the receptor. As such, it is a potential antimicrobial agent to prevent infection via a strategy unlikely to promote bacterial resistance and a vaccine candidate against M. catarrhalis. In addition, it could serve more widely as a novel research tool and as a potential therapeutic agent in CEACAM-based physiological disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-2958.2005.04487.xDOI Listing
March 2005

Unique modifications with phosphocholine and phosphoethanolamine define alternate antigenic forms of Neisseria gonorrhoeae type IV pili.

Proc Natl Acad Sci U S A 2004 Jul 12;101(29):10798-803. Epub 2004 Jul 12.

Centre for Molecular Biology and Neuroscience, University of Oslo, 0316 Oslo, Norway.

Several major bacterial pathogens and related commensal species colonizing the human mucosa express phosphocholine (PC) at their cell surfaces. PC appears to impact host-microbe biology by serving as a ligand for both C-reactive protein and the receptor for platelet-activating factor. Type IV pili of Neisseria gonorrhoeae (Ng) and Neisseria meningitidis, filamentous protein structures critical to the colonization of their human hosts, are known to react variably with monoclonal antibodies recognizing a PC epitope. However, the structural basis for this reactivity has remained elusive. To address this matter, we exploited the finding that the PilE pilin subunit in Ng mutants lacking the PilV protein acquired the PC epitope independent of changes in pilin primary structure. Specifically, we show by using mass spectrometry that PilE derived from the pilV background is composed of a mixture of subunits bearing O-linked forms of either phosphoethanolamine (PE) or PC at the same residue, whereas the wild-type background carries only PE at that same site. Therefore, PilV can influence pilin structure and antigenicity by modulating the incorporation of these alternative modifications. The disaccharide covalently linked to Ng pilin was also characterized because it is present on the same peptides bearing the PE and PC modifications and, contrary to previous reports, was found to be linked by means of 2,4-diacetamido-2,4,6-trideoxyhexose. Taken together, these findings provide new insights into Ng type IV pilus structure and antigenicity and resolve long-standing issues regarding the nature of both the PC epitope and the pilin glycan.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.0402397101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC490014PMC
July 2004
-->