guanylin and Escherichia-coli-Infections

Some E. coli cause diarrhea by elaborating heat-labile and heat-stable (ST) enterotoxins which stimulate intestinal secretion. E. coli ST's are small peptides which bind to intestinal luminal epithelial cell receptors. The ST receptor, one of a family of receptor-cyclases called guanylyl cyclase C (GC-C), is a membrane spanning protein containing an extracellular binding domain and intracellular protein kinase and catalytic domains. The intestine synthesizes and secretes homologous peptides, guanylin and uroguanylin. The kidney also synthesizes uroguanylin. ST, guanylin or uroguanylin binding to GC-C results in increased cGMP, phosphorylation of the CFTR Cl- channel and secretion. Proguanylin and prouroguanylin circulate in blood and bind to receptors in intestine, kidney, liver, brain etc. In the kidney, they stimulate the excretion of Na+ and K+. Study of GC-C "knock-out" mice reveal that GC-C is important to intestinal salt and water secretion, duodenal bicarbonate secretion, recovery from CCl4-induced liver injury, and to intestinal polyp formation in Min mice lacking GC-C.

Topics: Amino Acid Sequence; Animals; Bacterial Toxins; Diarrhea; Enterotoxins; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Gastrointestinal Hormones; Guanylate Cyclase; Humans; Intestinal Polyps; Mice; Mice, Knockout; Models, Biological; Molecular Sequence Data; Natriuretic Peptides; Peptides; Receptors, Enterotoxin; Receptors, Guanylate Cyclase-Coupled; Receptors, Peptide

Enterotoxigenic Escherichia coli (ETEC) causes diarrhoea by secreting enterotoxins into the small intestine. Human ETEC strains may secrete any combination of three enterotoxins: the heat-labile toxin (LT) and the heat-stable toxins (ST), of which there are two variants, called human ST (STh) and porcine ST (STp). Strains expressing STh, either alone or in combination with LT and/or STp, are among the four most important diarrhoea-causing pathogens affecting children in low- and middle-income countries. ST is therefore an attractive target for ETEC vaccine development. To produce a safe ST-based vaccine, several challenges must be solved. ST must be rendered immunogenic and non-toxic, and antibodies elicited by an ST vaccine should neutralize ST but not cross-react with the endogenous ligands uroguanylin and guanylin. Virus-like particles (VLPs) tend to be highly immunogenic and are increasingly being used as carriers for presenting heterologous antigens in new vaccines. In this study, we have coupled native STh and the STh-A14T toxoid to the coat protein of Acinetobacter phage AP205 by using the SpyCatcher system and immunized mice with these VLPs without the use of adjuvants. We found that both STs were efficiently coupled to the VLP, that both the STh and STh-A14T VLPs were immunogenic in mice, and that the resulting serum antibodies could completely neutralize the toxic activities of native STh. The serum antibodies showed a high degree of immunological cross-reaction to STp, while there was little or no unwanted cross-reaction to uroguanylin and guanylin. Moreover, compared to native STh, the STh-A14T mutation did not seem to negatively impact the immunogenicity of the construct or the neutralizing ability of the resulting sera. Taken together, these findings demonstrate that VLPs are suitable carriers for making STs immunogenic, and that the STh-A14T-coupled AP205 VLP represents a promising ETEC vaccine candidate.

Topics: Acinetobacter; Animals; Antibodies, Bacterial; Antibodies, Neutralizing; Antigens, Bacterial; Bacterial Toxins; Bacteriophages; Cross Reactions; Enterotoxigenic Escherichia coli; Escherichia coli Infections; Escherichia coli Vaccines; Female; Gastrointestinal Hormones; Immunization; Mice; Mice, Inbred BALB C; Natriuretic Peptides; Toxoids; Vaccines, Subunit; Vaccines, Virus-Like Particle

Infection with enterotoxigenic

Topics: Animals; Antibodies, Bacterial; Antibodies, Neutralizing; Bacterial Toxins; Cross Reactions; Enterotoxigenic Escherichia coli; Enterotoxins; Escherichia coli Infections; Escherichia coli Proteins; Escherichia coli Vaccines; Gastrointestinal Hormones; Humans; Immunization; Mice; Mice, Inbred BALB C; Natriuretic Peptides; Swine

Heat-stable toxin (STa)-producing enterotoxigenic

Topics: Animals; Antibodies, Bacterial; Antibodies, Neutralizing; Antigens, Bacterial; Bacterial Toxins; Child; Cross Reactions; Enterotoxigenic Escherichia coli; Enterotoxins; Escherichia coli Infections; Female; Gastrointestinal Hormones; Hot Temperature; Humans; Immunization; Mice; Mutation; Natriuretic Peptides; Toxoids

In previous work, we identified xanthine oxidase (XO) as an important enzyme in the interaction between the host and enteropathogenic Escherichia coli(EPEC) and Shiga-toxigenic E. coli(STEC). Many of the biological effects of XO were due to the hydrogen peroxide produced by the enzyme. We wondered, however, if uric acid generated by XO also had biological effects in the gastrointestinal tract. Uric acid triggered inflammatory responses in the gut, including increased submucosal edema and release of extracellular DNA from host cells. While uric acid alone was unable to trigger a chloride secretory response in intestinal monolayers, it did potentiate the secretory response to cyclic AMP agonists. Uric acid crystals were formed in vivo in the lumen of the gut in response to EPEC and STEC infections. While trying to visualize uric acid crystals formed during EPEC and STEC infections, we noticed that uric acid crystals became enmeshed in the neutrophilic extracellular traps (NETs) produced from host cells in response to bacteria in cultured cell systems and in the intestine in vivo Uric acid levels in the gut lumen increased in response to exogenous DNA, and these increases were enhanced by the actions of DNase I. Interestingly, addition of DNase I reduced the numbers of EPEC bacteria recovered after a 20-h infection and protected against EPEC-induced histologic damage.

Topics: Animals; Cell Line; Colforsin; Enterohemorrhagic Escherichia coli; Escherichia coli Infections; Gastrointestinal Hormones; Humans; Intestines; Natriuretic Peptides; Rabbits; Shiga-Toxigenic Escherichia coli; Uric Acid; Xanthine Oxidase

Tight junctions contribute to the formation and establishment of intestinal epithelial barriers against microbial infections. However, a variety of enteric pathogens have developed strategies to adhere to and invade epithelial cells and disrupt epithelial integrity. The aim of this study was to ascertain if enterotoxigenic Escherichia coli heat-stable enterotoxin (STa) can cause deterioration of epithelial barrier integrity. Since STa shows amino acid similarity to guanylin, we evaluated the effects of both of these molecules on T84 epithelial cells. T84 epithelial monolayers were grown on 24-well Transwell filters and barrier integrity was assayed by measurement of transepithelial electrical resistance (TER). Macromolecular permeability of the monolayers was determined by measuring the paracellular passage of FITC-labeled dextran 4000 from apical to basolateral compartments of the Transwell filter culture. Treatment of T84 monolayers with either ST or guanylin did not increase paracellular permeability to FITC-dextran. However, although guanylin, which is a physiological guanylate cyclase activator, did not change TER in polarized T84 monolayers, ST did elicit a reduction in TER within 2h, at concentrations above 4μM. These data suggest that STa causes not only induction of water secretion but also intestinal barrier dysfunction.

Topics: Bacterial Toxins; Cell Line; Cell Membrane Permeability; Electric Impedance; Enterotoxins; Epithelial Cells; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Gastrointestinal Hormones; Humans; Intestine, Small; Natriuretic Peptides