Adhesion of Diarrheagenic Escherichia coli and Inhibition by Glycocompounds Engaged in the Mucosal Innate Immunity (original) (raw)
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FEMS Microbiology Letters, 2000
Binding to a specific receptor is an essential step for most enteropathogens to initiate an intestinal infection. We analyzed the inhibitory effect of human milk and its protein components on adhesion of two diarrheagenic Escherichia coli strains, diffusely adherent E. coli (DAEC) and enteroaggregative E. coli (EAEC), to HeLa cells. Defatted milk, whey proteins, immunoglobulin and non-immunoglobulin fractions, in concentrations lower than usually found in whole milk, inhibited both DAEC and EAEC adhesion, indicating that human milk components may contribute to the defense of the infants against enteropathogens.
Brazilian Journal of Microbiology, 2007
Enterotoxigenic Escherichia coli (ETEC) is the most common cause of diarrhea in children in developing countries and among travelers to ETEC endemic areas. ETEC diarrhea is caused by colonization of the small intestine mediated by colonization factor (CF) antigens, and subsequent elaboration of enterotoxins. Breast feeding has been related to protection against enteric infections. The protective effect of human milk can be ascribed to its immunoglobulin content, specially secretory immunoglobulin A (sIgA), and to nonimmunoglobulin components such as free oligosaccharides, glycoproteins and glycolipids. In this study we investigated the effect of whole human milk and its fractions immunoglobulin and non-immunoglobulin on the adherence of ETEC strains possessing different CFs to Caco-2 cells, as well as the ability of sIgA and free secretory component (fSC) to bind to bacterial superficial proteins. Pooled human milk from three donors were fractionated by gel filtration and analyzed by SDS-PAGE. Our results revealed that whole human milk and its proteins fractions, containing sIgA and fSC, inhibited adhesion ETEC strains harboring different colonization factors antigens. We also verified that sIgA and fSC, using immunoblotting and immunogold labeling assays, bound to some fimbrial proteins and other material present in bacterial surface. Our findings suggest that whole human milk and its fractions may contribute to protection against ETEC infections by blocking bacterial adhesion mediated by different colonization antigens.
FEMS Immunology & Medical Microbiology, 2006
Diarrhea is an important cause of morbidity and mortality amongst infants of low socioeconomic levels in developing countries and in travelers who visit such areas. Enterotoxigenic E. coli strains express two sets of virulence-associated factors: enterotoxins (heat-stable toxins or heat-labile toxins) and colonization factors. Studies have shown that breast-feeding protects infants against infectious diseases, such as diarrhea, as it presents a great variety of immunological components. The aim of this study was to analyze the reactivity of immunoglobulin A from human colostrum to colonization factor antigens I and II. The colostrum ability in preventing enterotoxigenic E. coli adhesion to Caco-2 cells was also evaluated. Colostrum samples were collected from 32 healthy women, and a human colostrum pool was prepared. Enterotoxigenic E. coli strains expressing colonization factor antigens I and II were utilized. The colostrum pool and individual samples showed variable antienterotoxigenic E. coli immunoglobulin A titers, that were reactive with colonization factor antigen I and CS1/CS3 (colonization factor antigen II). The human colostrum pool and individual samples inhibited enterotoxigenic E. coli colonization factor antigen I and II adhesion to Caco-2 cells, at variable levels, and this ability was a result of immunoglobulin A antibodies reactive to these colonization factors. The immunoglobulin A-depleted pool lost this inhibitory ability. As bacterial adhesion is the initial mechanism of enterotoxigenic E. coli infection, breast-feeding could protect the offspring against diarrhea caused by this agent.
Adherence of Diarrheagenic Escherichia coli Strains to Epithelial Cells
Infection and Immunity, 2005
An important early step in the colonization of the human gastrointestinal tract by bacteria is the adhesion of the organism to the host surface. Although adhesion is essential to maintain members of the normal microflora in the intestine, it is also the critical early phase in all diarrheal infections caused by pathogenic Escherichia coli strains. It is important, therefore, to fully understand the mechanisms underlying E. coli adhesion and in that way to be able to develop methods of maintaining the intestinal normal microflora and to prevent pathogenic E. coli from initiating an infectious process. Great progress has been made in recent years in the identification of the adherence factors of different diarrheagenic E. coli strains (Table 1). These protein structures are associated with the bacterial surface and can be subdivided into fimbrial and nonfimbrial adhesins (Fig. 1). In this minireview, we will discuss recent advances in the identification and characterization of previously known and novel adhesion factors from the six major categories of diarrheagenic E. coli strains: enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), and diffusely adhering E. coli (DAEC).
Pediatric Research, 2015
Basic Science Investigation nature publishing group Background: Breast-fed infants have a lower incidence of acute gastroenteritis due to the presence of several anti-infective factors in human milk. The aim of this work is to study the capacity of human milk glycosaminoglycans (GAGs) to inhibit the adhesion of some common pathogenic bacteria. Methods: GAGs were isolated from a pool of milk samples collected from different mothers during the first month of lactation. Experiments were carried out to study the ability of GAGs to inhibit the adhesion of two intestinal microorganisms (enteropathogenic Escherichia coli serotype 0119 and Salmonella fyris) to Caco-2 and Int-407 cell lines. results: The study showed that the GAGs had an anti-adhesive effect on the two pathogenic strains studied with different degrees of inhibition. In particular, in the presence of human milk GAGs, the adhesion of S. fyris to Caco-2 cells and to Int-407 cells of both tested strains was significantly reduced. conclusion: Our results demonstrated that GAGs in human milk can be one of the important defensive factors against acute diarrheal infections in breast-fed infants.
Brazilian Journal of Medical and Biological Research
We have studied the effect of serum from infants with diarrhea and of cord serum on the localized adherence of enteropathogenic Escherichia coli (EPEC) to HeLa cells. Serum samples from 16 infants with diarrhea due to EPEC of serotypes O55:H6, O111: H-, O111:H2, O119:H6 and O142:H6 were used. The adherence ability of EPEC strains belonging to serotypes identical to (homologous) or different from (heterologous) those isolated from the infants' feces was highly inhibited by samples of infant serum collected both during the acute phase of the illness and upon discharge from the hospital. These data confirm the development of antibodies against EPEC adhesins and the cross-reaction between different EPEC serotypes. Cord serum inhibited the localized adherence of EPEC strains at different levels according to the serotype of the strain studied. These results suggest that the placental transfer of adhesin-related antibodies does not protect the newborn against EPEC infections, since half of our patients were less than 30 days old.
Inhibition of enteroaggregative Escherichia coli cell adhesion in-vitro by designed peptides
Microbial Pathogenesis, 2016
Background. Enteroaggregative Escherichia coli (EAEC) is an important agent of the persistent diarrhea among low socioeconomic level children in developing countries that may be associated with chronic undernourishment. Breast-feeding is effective in protecting infants against diarrhea and other infectious diseases. The aim of the study is to verify the ability of human colostrum to inhibit aggregative adhesion of EAEC to HEp-2 cells and the presence of antibodies reactive to antigenic fractions of EAEC in colostrum samples. Methods. Enzyme-linked immunosorbent assay, immunoblotting and adhesion assays of EAEC to HEp-2 cells were done with pooled or individual colostrum samples (n ؍ 35). Assays were performed with a well-known EAEC strain, O44:H18 E. coli (strain 042). Colostral IgA was isolated by affinity chromatography in Sepharose anti-human alpha chain column. Results. Total colostrum and isolated IgA inhibited EAEC adhesion, and this ability was associated with the presence of IgA antibodies against a 15-kDa band, compatible with the subunits of aggregative adherence fimbrial adhesin II, characteristic of the 042 strain, absent in its plasmid-cured isogenic strain, that was used as control. Individual colostrum samples also inhibited adhesion, showed variable antibody titles against EAEC antigens in enzyme-linked immunosorbent assay and recognized many antigenic fractions in immunoblotting assays, including the 15-kDa band. Conclusions. These results confirm that IgA from human colostrum inhibits adhesion of EAEC to HEp-2 cells and suggest that colostrum IgA antibodies reactive to EAEC antigens may play a role in protection of infants against diarrhea caused by these bacteria.
Enteropathogenic Escherichia coli (EPEC) are frequently isolated as a cause of infantile diarrhea in developing countries. Its pathogenicity is distinguished by histopathological alterations at the site of infection, known as attaching and effacing (A/E) lesions, in which bacterial virulence factors and host proteins participate. Intimin, a bacterial adhesin expressed by all EPEC described to date, is responsible for the intimate adherence of the bacteria to host cells and is essential for the formation of A/E lesions. Mucosal vaccination may represent an efficacious intervention to prevent EPEC infection and lower morbidity and mortality rates. Strategies for mucosal vaccinations that use lactic acid bacteria for the delivery of heterologous antigens rely on their safety profile and ability to stimulate the immune system. In the present work, we have constructed Lactobacillus casei strains expressing different fragments of intimin b, a subtype that is frequently expressed by EPEC strains. Mucosal immunization of mice with L. casei expressing intimin fragments induced specific systemic and mucosal antibodies. These antibodies were able to recognize native intimin on the surface of EPEC and to inhibit in vitro EPEC binding to epithelial cells.
Human Milk Glycoproteins Inhibit the Adherence ofSalmonella typhimuriumto HeLa Cells
Microbiology and Immunology, 2006
Diarrhea is one of the major causes of death in children living in developing countries (10) and Salmonella species are important causative agents of diarrhea. Several categories of diarrheagenic Escherichia coli such as enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), enterohemorragic E. coli (EHEC) and enteroaggregative E. coli (EAEC) are also frequently associated with intestinal infections in those geographic areas (17). Diarrhea caused by Salmonella typhimurium occurs in two main steps. First, the pathogen adheres to enterocytes and colonizes the intestinal mucous membrane. This ability is mediated by surface structures, which are encoded in the chromosome, such as type 1 fimbriae, long polar fimbriae and aggregative fimbriae, or plasmids, such as plasmid-encoded fimbriae (13). Once colonized, the host cell is invaded. Takeuchi (24) showed, for the first time, the mechanism by which S. typhimurium penetrates the enterocyte, including a rearrangement of actin cytoskeleton, forming a typical membrane ruffling (12). The invasion mechanism is encoded by five pathogenicity islands (SPI-Salmonella pathogenicity islands) (9, 18). The best characterized SPI-1 is primarily required for bacterial penetration of the intestinal epithelial cells and encodes a type III secretion system, including its regulators and its secreted effectors (18). Diarrheal diseases are important causes of infant mortality and efforts have been made to improve prophylactic measures. Since several studies have shown that breast-feeding protects newborns against enteric infections (11, 22), the understanding of the mechanisms of human milk protection could help in the establishment of valuable procedures to prevent diarrhea. The protective effect of human milk seems to be a complex event and it has been attributed to its immunoglobulin content, mainly secretory IgA (sIgA) and to nonimmunoglobulin content, such as lysozyme, lactoferrin, bifidus factor (11), free secretory component (8) and oligosaccharides (4). Lactoferrin (Lf) is an 80-kDa