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Helicobacter pylori Sialic Acid-Specific Surface Lectin

Hirmo, Siiri LU (2000)
Abstract (Swedish)
Popular Abstract in Swedish

Helicobacter pylori är en Gramnegativ spiralformad human-specifik patogen med förmåga att penetrera magsäckens slemlager och kolonisera i epitelskiktet. H. pylori infektion betraktas som en högriskfaktor för utvecklandet av kronisk gastrit, magsår och ventrikelcancer. H. pylori har en komplex cellyta med ett flertal kolhydratbindande proteiner, sk. lektiner att interagera med eukaryota cellytors glykokonjugat och kolonisera på cellytor. Sialinsyre-bindande proteiner representerar en grupp av dessa specifika lektin-liknande adhesiner som är viktiga i etablerandet av denna kolonisations och infektions process. Vissa stammar av H. pylori har ett område i kromosomen (sk. cagA patogenicitetsön), som... (More)
Popular Abstract in Swedish

Helicobacter pylori är en Gramnegativ spiralformad human-specifik patogen med förmåga att penetrera magsäckens slemlager och kolonisera i epitelskiktet. H. pylori infektion betraktas som en högriskfaktor för utvecklandet av kronisk gastrit, magsår och ventrikelcancer. H. pylori har en komplex cellyta med ett flertal kolhydratbindande proteiner, sk. lektiner att interagera med eukaryota cellytors glykokonjugat och kolonisera på cellytor. Sialinsyre-bindande proteiner representerar en grupp av dessa specifika lektin-liknande adhesiner som är viktiga i etablerandet av denna kolonisations och infektions process. Vissa stammar av H. pylori har ett område i kromosomen (sk. cagA patogenicitetsön), som genetiskt kodar för ungefär 30-tal proteiner av ha betydelse för bakteriens förmåga att kolonisera magsäcken och orsaka vävnadsskada. Dessa högvirulenta stammar är associerade med en mer kronisk infektion. Från studier, baserade på hemagglutinations reaktioner med nativa röda blodkroppar i jämförelse med sialidas-behandlade, visade det sig att en tredjedel av testade H. pylori isolat uttryckte sialinsyra-beroende hemagglutination. Specificitet för terminalt a-2,3-bunden sialinsyra demonstrerades med användning av transsialidas-modifierade röda blodkroppar för hemagglutinationsförsök. Resultat från mikroskopistudier med fluorescence-märkning visade att merparten av bakterierna i populationen utrycker denna sialinsyre-specifika bindning. Elektronmikroskopisk analys avslöjade att sialinsyre-bindande protein (SAL) var lokaliserad på yttermembranet av bakteriecellen i form av komplex, medan bindningen saknades fullständigt på bakteriens rörelseorgan, de sk. flagellerna. Identifiering av proteiner i affinitets-renade SAL komplexet med mass- spektrometri avslöjade närvaro av två närbesläktade ytmembran proteiner AlpA/B, vilka har föreslagits vara involverade i cell adhesion med okänd specificitet. Ytterligare studier behövs emellertid för att identifiera också mindre förekommande proteiner i det isolerade SAL komplexet för att slutsatser kan dragas. H. pylori sialinsyre-specifika lektiner är troligen involverade i interaktioner med mukuslagret i magen som täcker epitelcellerna, och därigenom underlättar för bakterien att nå magsäckens epitel. Mucin-liknande sialylerade glykokonjugat från bovin mjölk visade hög inhiberings potential för H. pylori och kan därför anses som kandidater att testas för att förhindra magsäcks kolonisation. Ett utbrett användande av antibiotika hittills vid H. pylori infektion har lett till en ökad resistensutveckling. Därför har konceptet att söka blockera H pylori infektionen med receptoranaloger blivit alltmer aktuellt. En kyvett-baserad optisk biosensor, IAsys®, kan effektivt användas för att studera H. pylori interaktioner med glykokonjugat och analysera bindningsegenskaper. Det finns inga bevis för sialidas produktion hos H. pylori, istället reglerar patogenen troligen expression av sialinsyre-bindande lektiner genom att lossna från mucin eller från epitelceller för vidare spridning. (Less)
Abstract
Helicobacter pylori is a gastric pathogen colonising the gastric mucus layer and epithelium of gastric tissue and is associated with chronic type B gastritis and peptic ulcer disease. The attachment of H. pylori to gastric epithelial cells involves several structures recognised by specific bacterial surface proteins. Since colonisation is an initial and critical step in the development of a chronic disease, the identification of H. pylori adhesins is important for defining specific interactions between host and pathogen with the aim to develop adhesin-receptor analogues, which can inhibit gastric tissue colonisation. H. pylori sialic acid (Sia)-binding surface proteins represent a group of lectin-like adhesins, which are most likely... (More)
Helicobacter pylori is a gastric pathogen colonising the gastric mucus layer and epithelium of gastric tissue and is associated with chronic type B gastritis and peptic ulcer disease. The attachment of H. pylori to gastric epithelial cells involves several structures recognised by specific bacterial surface proteins. Since colonisation is an initial and critical step in the development of a chronic disease, the identification of H. pylori adhesins is important for defining specific interactions between host and pathogen with the aim to develop adhesin-receptor analogues, which can inhibit gastric tissue colonisation. H. pylori sialic acid (Sia)-binding surface proteins represent a group of lectin-like adhesins, which are most likely crucial for the colonisation of the human stomach mucosa. Haemagglutination experiments with enzymatically derivatised erythrocytes carrying Sias only on defined glycans demonstrated that one third of those H. pylori strains investigated express Sia-binding activity. All of these were specific for a-2,3-linked Sia. This specificity was confirmed by microscopy studies using fluorescent neoglycoconjugates as targets. Further examination by electron microscopy revealed the surface localisation of this Sia-specific lectin (SAL) condensed into complexes. The lectin was extracted from the surface of the bacteria by water extraction and affinity purified on glutardialdehyde-fixed erythrocytes. The analysis of proteins in the isolated H. pylori SAL complex by proteomics approach revealed the presence of two H. pylori outer membrane proteins AlpA/B, which had been proposed to function in H. pylori gastric tissue adherence processes. Since the binding specificity of these proteins is unknown, the Sia-binding activity may reside in a minor component of the complex associated with AlpA/B. H. pylori Sia-binding lectins seem to be involved in interactions with gastrointestinal mucins facilitating the spread of the pathogen also to the gastric epithelium. Mucin-like sialylated components from bovine milk show high inhibitory potencies for H. pylori binding to sialylglycoconjugates and could probably be developed as potent anti-infectious components against this pathogen. A cuvette-based optical biosensor, IAsysâ was efficiently used for analysis of the structural requirements for H. pylori interactions with such glycoconjugates. In contrast to a previous report, no evidence for sialidase activity of H. pylori was obtained. Therefore, it can be assumed that H. pylori may regulate the expression of its Sia-binding lectins to be released from either mucin or cell surfaces for further spreading. (Less)
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author
opponent
  • Prof Feizi, Ten, Imperial College School of Medicine, Northwick Park Institute for Medical Research, Watford Road, Harrow, U.K.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
bakteriologi, mycology, Mikrobiologi, virology, bacteriology, haemagglutinin, Helicobacter pylori, sialic acid, sialidase, gastrointestinal mucin, milk glycoprotein, Microbiology, resonant mirror biosensor, virologi, mykologi
pages
92 pages
publisher
Department of Infectious Diseases and Medical Microbiology, Lund University
defense location
Rune Grubb salen, BMC, Sölvegatan 19, Lund
defense date
2000-05-04 10:15
external identifiers
  • other:ISRN: LUMEDW/MEMI
ISBN
91-628-4012-6
language
English
LU publication?
yes
id
902fa462-e186-450c-86c8-f82305fc9687 (old id 40409)
date added to LUP
2007-08-01 14:07:24
date last changed
2016-09-19 08:45:07
@phdthesis{902fa462-e186-450c-86c8-f82305fc9687,
  abstract     = {Helicobacter pylori is a gastric pathogen colonising the gastric mucus layer and epithelium of gastric tissue and is associated with chronic type B gastritis and peptic ulcer disease. The attachment of H. pylori to gastric epithelial cells involves several structures recognised by specific bacterial surface proteins. Since colonisation is an initial and critical step in the development of a chronic disease, the identification of H. pylori adhesins is important for defining specific interactions between host and pathogen with the aim to develop adhesin-receptor analogues, which can inhibit gastric tissue colonisation. H. pylori sialic acid (Sia)-binding surface proteins represent a group of lectin-like adhesins, which are most likely crucial for the colonisation of the human stomach mucosa. Haemagglutination experiments with enzymatically derivatised erythrocytes carrying Sias only on defined glycans demonstrated that one third of those H. pylori strains investigated express Sia-binding activity. All of these were specific for a-2,3-linked Sia. This specificity was confirmed by microscopy studies using fluorescent neoglycoconjugates as targets. Further examination by electron microscopy revealed the surface localisation of this Sia-specific lectin (SAL) condensed into complexes. The lectin was extracted from the surface of the bacteria by water extraction and affinity purified on glutardialdehyde-fixed erythrocytes. The analysis of proteins in the isolated H. pylori SAL complex by proteomics approach revealed the presence of two H. pylori outer membrane proteins AlpA/B, which had been proposed to function in H. pylori gastric tissue adherence processes. Since the binding specificity of these proteins is unknown, the Sia-binding activity may reside in a minor component of the complex associated with AlpA/B. H. pylori Sia-binding lectins seem to be involved in interactions with gastrointestinal mucins facilitating the spread of the pathogen also to the gastric epithelium. Mucin-like sialylated components from bovine milk show high inhibitory potencies for H. pylori binding to sialylglycoconjugates and could probably be developed as potent anti-infectious components against this pathogen. A cuvette-based optical biosensor, IAsysâ was efficiently used for analysis of the structural requirements for H. pylori interactions with such glycoconjugates. In contrast to a previous report, no evidence for sialidase activity of H. pylori was obtained. Therefore, it can be assumed that H. pylori may regulate the expression of its Sia-binding lectins to be released from either mucin or cell surfaces for further spreading.},
  author       = {Hirmo, Siiri},
  isbn         = {91-628-4012-6},
  keyword      = {bakteriologi,mycology,Mikrobiologi,virology,bacteriology,haemagglutinin,Helicobacter pylori,sialic acid,sialidase,gastrointestinal mucin,milk glycoprotein,Microbiology,resonant mirror biosensor,virologi,mykologi},
  language     = {eng},
  pages        = {92},
  publisher    = {Department of Infectious Diseases and Medical Microbiology, Lund University},
  school       = {Lund University},
  title        = {Helicobacter pylori Sialic Acid-Specific Surface Lectin},
  year         = {2000},
}