Asunto(s)
Desoxirribonucleasas de Localización Especificada Tipo II/metabolismo , Sialiltransferasas/genética , Porcinos/genética , Animales , Exones , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa/veterinaria , Polimorfismo de Longitud del Fragmento de Restricción , beta-D-Galactósido alfa 2-6-SialiltransferasaRESUMEN
Bacteria have been associated with a wide variety of syndromes in animals and humans. These include enteropathies, urinary infections, meningitis and septicemia. Among the distinct set of tactics to prevail within the host, is the ability of bacteria to adhere to cellular targets. Adhesion to the gut by enteric bacteria occurs via several types of adhesins. During the last 15 years, much information has become available on bacterial adhesins and mechanisms governing bacteria-host interactions. Due to their location on the cell surface, establishing a carbohydrate frontier, and their inherent variability, glycosphingolipids and glycoproteins provide a wide range of binding sites for bacteria, toxins and more generally lectins. Bacterial lectins are localized either on the tip or along fimbrial filaments or on nonfimbrial structures. We examine in this short review, a collection of pathogen lectins, through their different receptor specificities. For sialic acid-binding lectins, the conformation of terminal sialic acid is essential for adhesion, whereas for other bacterial lectins, complementary sugars may be arranged in specific linear and/or branched sequences. Finally, it appears that the composition and structure of cell carbohydrates could in part explain the bacterial tropism and susceptibility or resistance of the host to enteric diseases.
Asunto(s)
Bacterias/patogenicidad , Adhesión Bacteriana , Enfermedades Intestinales/microbiología , Intestinos/microbiología , Acetilglucosamina , Animales , Galactósidos , Genes Bacterianos , Glicoconjugados/química , Hemaglutininas , Humanos , Lectinas , Microvellosidades/química , Microvellosidades/microbiología , Ácidos SiálicosRESUMEN
Enteropathogenic K88 fimbricated E. coli colonize the piglet small intestine. In swine, it has been previously established that some pigs lack intestinal receptors for K88 lectins and that these animals are resistant to infections by K88-positive E. coli. The receptor is inherited as a simple mendelian character. The interactions established between the glycoconjugate receptors of pig brush borders and K88 lectins are mediated by O- and N-linked glycoproteins which differ between adhesive and non-adhesive piglets. In this study the adhesion of E. coli K88+ in crossbred F2 (LW x MS) x (LW x MS) populations. By using in vitro brush border test, we observed modulation of the adhesion of K88 fimbriae and distinguished high and low affinity receptors. Furthermore, we correlated the attachment with glycoprotein pattern of epithelial cells and mucus. Epithelial cells and mucus contained several glycopeptides (from 42 to 74 kDa) recognized by K88ab fimbriae. The 74 kDa glycoprotein was characteristic of adhesive phenotype and was a mucosal transferrin (iTf). It appeared that iTf was more abundant in adhesive intestines than in non-adhesive ones, suggesting that susceptibility/resistance phenotype could be related to iron metabolism in the intestinal tract. Furthermore, we visualized the intestinal transferrin receptors on the brush border membrane of epithelial cells, probably implicated in iron absorption.
Asunto(s)
Antígenos Bacterianos , Antígenos de Superficie/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Proteínas Fimbrias , Intestino Delgado/microbiología , Hierro/metabolismo , Animales , Transporte Biológico , Membrana Celular/metabolismo , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/patología , Infecciones por Escherichia coli/veterinaria , Glicoproteínas/metabolismo , Intestino Delgado/metabolismo , Mucinas/metabolismo , Receptores de Transferrina/metabolismo , Porcinos , Transferrina/metabolismoRESUMEN
Enterotoxigenic Escherichia coli (ETEC) strains expressing F5 (K99) fimbriae cause diarrhoea in the young animal through adhesion to specific sialoglycolipids of the small intestine surface. We studied here an infant mouse diarrhoea model, as CBA infant mice are susceptible to F5-positive ETEC infection, whereas DBA/2 ones are resistant. In an attempt to determine an enzymatic basis for susceptibility and resistance, we investigated the intestine ganglioside pattern in relation to the activity of glycosyltransferases responsible for the globo- and ganglio-series. We observed that the intestine of susceptible CBA infant mice displayed a characteristic sialoglycolipid pattern containing mainly the F5 receptors. The two murine strains differed in the relative activities of galactosyltransferases (GbOse3Cer and GM1 synthases), N-acetylgalactosylaminyltransferases (GA2 and GM2 synthases) and sialytransferases (GM3 and GD3 synthases). An elevated GM3-synthase activity was observed in the intestine of susceptible CBA infant mice, at the age of high susceptibility. Hence, we conclude that the marked specificity of mouse type correlated with susceptibility and resistance to F5-positive ETEC infection which could be controlled through the regulation of glycosyltransferase activities.
Asunto(s)
Toxinas Bacterianas , Infecciones por Escherichia coli/etiología , Escherichia coli/patogenicidad , Glicosiltransferasas/metabolismo , Mucosa Intestinal/enzimología , Animales , Animales Recién Nacidos , Antígenos de Superficie , Adhesión Bacteriana , Secuencia de Carbohidratos , Bovinos , Diarrea/enzimología , Diarrea/etiología , Escherichia coli/inmunología , Escherichia coli/fisiología , Infecciones por Escherichia coli/enzimología , Femenino , Gangliósidos/química , Gangliósidos/metabolismo , Glucolípidos/química , Glucolípidos/metabolismo , Técnicas In Vitro , Masculino , Ratones , Ratones Endogámicos CBA , Ratones Endogámicos DBA , Datos de Secuencia Molecular , Ratas , Especificidad de la Especie , PorcinosRESUMEN
Putative receptors of Escherichia coli K88 fimbriae are either tightly membrane bound or an integral part of membranes. Thus, proteins associated with piglet small intestinal mucosae were solubilized by a detergent (deoxycholate). A 74-kDa glycoprotein (GP74) purified from enterocyte and brush border membrane preparations was specifically detected in vitro by K88ab fimbriae. GP74 was recognized only in the mucosae of phenotypically adhesive animals. Metaperiodate treatment abolished the recognition, indicating that K88ab fimbriae-GP74 binding required the carbohydrate moiety. This glycoprotein belongs to the transferrin family and differed from the serum transferrin of the same adhesive-phenotype piglets. Unlike intestinal transferrin, serum transferrin was recognized independently of the adhesion phenotype. The glycan moieties of intestinal and serum transferrins differed in their molar compositions. Transferrin GP74 contained one monosialylated and monofucosylated glycan chain of the N-acetyllactosamine type. Intestinal holotransferrin exhibited pI values of 5.2, 5.3, 5.5, and 5.6, whereas serum holotransferrin pI values ranged between 5.4 and 6.2. Since mucosal transferrin was found intimately entrapped on membranes, we hypothesize that a K88ab fimbriae-transferrin-cell transferrin receptor complex might allow the bacteria to adhere to specific sites of the mucosa.
Asunto(s)
Escherichia coli/fisiología , Fimbrias Bacterianas/fisiología , Mucosa Intestinal/microbiología , Transferrina/metabolismo , Secuencia de Aminoácidos , Aminoácidos/análisis , Animales , Adhesión Bacteriana , Glicoproteínas/aislamiento & purificación , Punto Isoeléctrico , Datos de Secuencia Molecular , PorcinosRESUMEN
The specificity of N-acetylglucosamine-binding F17 fimbrial lectin of coli (also called FY or Att25) for the oligosacharide structures was investigated by mannose-resistant hemagglutination inhibition tests and direct binding assays. The linkage position of N-acetyl-glucosamine influenced its affinity in the preferential order of beta 1-3 > beta 1-6 > beta 1-4 beta > beta 1-2. Minimal GlcNAc beta 1-3Gal beta 1-sequence strongly bound to F17 lectin, whether located in terminal nonreducing position or internally in carbohydrate moieties. F17 lectin specifically interacted with this unit in O-glycosidically linked oligosaccharides of the bovine glycophorins and intestinal mucins. On the contrary, GlcNAc beta 1-NAsn, GlcNAc beta 1-6Man beta- and GlcNAc beta 1-4GlcNAc- of N-glycosylated proteins failed to bind to the lectin. Our findings emphasized the presence of multiple F17 mucosal receptor complex in the newborn calf intestines. Furthermore, the density of receptors for F17 fimbrial lectin seemed to depend on the age of the calf and the intestinal segment.
Asunto(s)
Adhesinas Bacterianas/metabolismo , Escherichia coli/metabolismo , Complejo GPIb-IX de Glicoproteína Plaquetaria , Glicoproteínas de Membrana Plaquetaria , Receptores de Superficie Celular/metabolismo , Animales , Secuencia de Carbohidratos , Bovinos , Eritrocitos/metabolismo , Glicoproteínas/metabolismo , Mucosa Intestinal/metabolismo , Lectinas/metabolismo , Datos de Secuencia Molecular , Receptores de Superficie Celular/químicaRESUMEN
The porcine brush border glycoproteins of 210 and 240 kDa, recognized by Escherichia coli K88ac fimbriae, contained O-linked oligosaccharides. The carbohydrate moieties were analysed by deglycosylation, lectin-binding and agglutination assays. Neuraminidase susceptibility of the 210 kDa receptor suggested that a sialoglycoprotein may act as receptor for the K88ac fimbriae. In contrast, K88ac-binding to the 210 and 240 kDa glycoproteins totally disappeared after fucosidase treatment, indicating the critical role of fucosyl residues at the receptor sites. Among the oligosaccharides extracted from these O-glycoproteins, K88ac fimbriae showed affinity for neutral sugar chains while sialylated species were not recognized. Our data suggest a possible role of the polypeptide backbone in the definition of receptor sites. Specific agglutination by K88ac-fimbriated E. coli of the erythrocytes of the hamster Mesocricetus auratus was inhibited by the anti-T peanut lectin and the lectins of Datura stramonium, Aleuria aurantia and Maackia amurensis. Hence, we propose that Gal beta 1-3GalNAc- and Fuc alpha 1-2Gal beta 1-3/4GlcNAc- are the main sequences mediating K88ac fimbrial binding. These structures were not detected in the non-adhesive piglet brush borders characterized by a high carbohydrate content. Additional oligosaccharides probably masked the underlying receptor structures.
Asunto(s)
Fimbrias Bacterianas/metabolismo , Yeyuno/metabolismo , Polisacáridos/metabolismo , Animales , Adhesión Bacteriana/efectos de los fármacos , Secuencia de Carbohidratos , Cricetinae , Glicoproteínas/química , Glicoproteínas/metabolismo , Glicosilación , Hemaglutinación/efectos de los fármacos , Técnicas In Vitro , Yeyuno/microbiología , Lectinas/química , Lectinas/farmacología , Microvellosidades/metabolismo , Datos de Secuencia Molecular , Peso Molecular , Neuraminidasa/farmacología , Oligosacáridos/química , Oligosacáridos/metabolismo , Polisacáridos/química , Porcinos , alfa-L-Fucosidasa/farmacologíaRESUMEN
Enterotoxigenic Escherichia coli (ETEC) frequently occurs in diarrheal disease afflicting domestic animals. In this paper is summarized the research carried out over the last decade on the two important determinants of virulence that plays a role in the development of the infection, namely the colonizing ability of the small intestine mediated by specific fimbrial adhesins acting as lectins and the production of enterotoxins. Recent progress in knowledge of the phenomenon led to alternative strategies of prevention and cure of enteric infection. Since bacterial recognition of mucosa surface receptors in an initial event in colonization, several approaches based on the competitive inhibition of ETEC adhesion have been developed. This review examines the following approaches: competitive colonization with non pathogenic strains, design of adhesin or toxin vaccines, receptor analog therapy and methods for in vivo suppression of virulence factors.
Asunto(s)
Toxinas Bacterianas/inmunología , Enfermedades de los Bovinos/microbiología , Diarrea/veterinaria , Enterotoxinas/inmunología , Infecciones por Escherichia coli/veterinaria , Proteínas de Escherichia coli , Escherichia coli/inmunología , Enfermedades de los Porcinos/microbiología , Secuencia de Aminoácidos , Animales , Adhesión Bacteriana/inmunología , Vacunas Bacterianas/inmunología , Bovinos , Enfermedades de los Bovinos/prevención & control , Diarrea/inmunología , Diarrea/prevención & control , Epítopos , Infecciones por Escherichia coli/inmunología , Infecciones por Escherichia coli/prevención & control , Datos de Secuencia Molecular , Porcinos , Enfermedades de los Porcinos/prevención & control , Vacunas Sintéticas/inmunologíaRESUMEN
Evidence for the existence of two phenotypes of piglets born to experimental herds was obtained based on the susceptibility of intestinal brush borders to adhesion of K99-positive Escherichia coli. The enterocytes of the K99-receptive piglets displayed a characteristic sialoglycolipid pattern, with a higher content of the monosialoglycolipids II3NeuGc-LacCer (GM3Gc), IV3NeuGc-nLcOse4Cer (SPGGc) and IV3NeuAc-nLcOse4Cer (SPG) and the oligosialogangliosides IV3NeuAc,II3NeuAc-GgOse4Cer (GD1a), II3(NeuAc)2-GgOse3Cer (GD2), II3(NeuAc)2-GgOse4Cer (GD1b) and IV3NeuAc,II3(NeuAc)2-GgOse4Cer (GT1b) when compared to the gangliosides of non-receptive piglets. The gangliosides from enterocytes of the non-receptive piglets were mainly the monosialogangliosides II3NeuAc-GgOse3Cer (GM2) and II3NeuAc-LacCer (GM3), only traces of the other sialoglycolipids being detected. Adhesion of 14C-labelled K99-positive E. coli cells to the piglet small intestinal sialoglycolipids, as tested by the thin-layer chromatogram overlay assay, revealed that the receptive enterocyte membrane was richer in glycolipids containing K99 receptor structures than the non-receptive enterocyte. Adhesion of K99-positive E. coli correlated with the degree of sialylation of the brush border glycolipids.
Asunto(s)
Antígenos de Superficie/metabolismo , Adhesión Bacteriana/fisiología , Toxinas Bacterianas , Escherichia coli/fisiología , Glucolípidos/metabolismo , Mucosa Intestinal/microbiología , Yeyuno/microbiología , Animales , Secuencia de Carbohidratos , Cromatografía en Capa Delgada , Epitelio/metabolismo , Epitelio/microbiología , Escherichia coli/inmunología , Femenino , Fimbrias Bacterianas/metabolismo , Vida Libre de Gérmenes , Glucolípidos/análisis , Yeyuno/metabolismo , Masculino , Microvellosidades/metabolismo , Microvellosidades/microbiología , Datos de Secuencia Molecular , Fenotipo , PorcinosRESUMEN
Calf diarrhea due to infection by enterotoxigenic Escherichia coli was treated by administration of glycoprotein glycans derived from bovine plasma. The glycan moieties of the nonimmunoglobulin fraction of plasma mimicked the oligosaccharide moiety of intestinal receptors recognized by K99 pili. These glycoprotein glycans inhibited adhesion of E. coli K99+ ST+ to erythrocyte glycoconjugates in vitro, and they protected colostrum-deprived newborn calves against lethal doses of enterotoxigenic E. coli (10(10) bacteria). Adhesion of bacteria to the intestines (duodenum, jejunum, and ileum) was significantly reduced (by 2 orders of magnitude) in treated calves.
Asunto(s)
Infecciones por Escherichia coli/terapia , Glicopéptidos/administración & dosificación , Animales , Adhesión Bacteriana/efectos de los fármacos , Secuencia de Carbohidratos , Bovinos , Enfermedades de los Bovinos/terapia , Diarrea/terapia , Diarrea/veterinaria , Heces/microbiología , Hemaglutinación/efectos de los fármacos , Concentración de Iones de Hidrógeno , Mucosa Intestinal/microbiología , Datos de Secuencia Molecular , Potasio/metabolismo , Sodio/metabolismo , Relación Estructura-ActividadRESUMEN
In this study we show that the adhesion to mucus of the enterotoxigenic Escherichia coli strains responsible for diarrhea in calves involves a bacterium-mucin recognition phenomenon in which the bacterial pili and specific mucus receptors carried by the glycoproteins (2,000 to 400 kilodalton) play a major role. An adhesion maximum was observed at a pH of less than 6 (4.75 to 5.25). The sialic acids and galactose appeared to be at least partly responsible for the attachment of K99 pili, whereas F41 pili preferentially recognized desialylated receptors. The attachment of different strains of E. coli characterized by the presence of the three main pili, K99, F41, and FY, known to be responsible for the binding of enterotoxigenic E. coli to the intestinal epithelium of the calf, was studied using Scatchard and Hill analyses. The attachment mechanism of bacteria carrying K99 pili showed positive cooperativity. FY and F41 pili recognized independent receptor sites, the first on sialylated mucus and the second on sialidase-treated mucus. Moreover, F41 pili were found to bind the native mucus according to a negative cooperativity phenomenon. Finally, the recognition sites carried by bacterial pilins may be saturated by some animal glycoprotein glycans which are therefore adhesion inhibitors.