Screening for complex carbohydrates inhibiting hemagglutinations by CFA/I- and CFA/II-expressing enterotoxigenicEscherichia colistrains

Inhibition of the binding of enterotoxigenic Escherichia coli Pb176 to human intestinal epithelial cell line HCT-8 by an extracellular protein fraction containing BIF of Bifidobacterium longum SBT2928: suggestive evidence of blocking of the binding receptor gangliotetraosylceramide on the cell surface

The extracellular protein fraction (P100V) containing the protein BIF produced by Bifidobacterium longum SBT2928 (BL2928), which inhibits the binding of enterotoxigenic Escherichia coli Pb176 (ETEC) to the glycolipid binding receptor gangliotetraosylceramide (GA1) also inhibited the binding of ETEC to the human intestinal epithelial cell line HCT-8 (ATCC CCL 244) in a dose-dependent manner. ETEC-binding inhibitory experiments using crude colonization factor antigen (CFA)-II prepared from ETEC, rabbit anti-GA1 antiserum, medium containing GA1 and media containing lectins, as the binding-inhibitors, suggest that the interaction between the CFA-II antigen present on the cell surface of ETEC and GA1 expressed on HCT-8 cells plays a significant role in the adherence between them. It is strongly suggested that the P100V fraction works as a blocker for the ETEC receptor GA1 on HCT-8 cells.

Biological activities of bovine glycomacropeptide

Biological activity of bovine kappa-caseino glycomacropeptide (GMP) has received much attention in recent years. Research has focused on the ability of GMP to bind cholera and Escherichia coli enterotoxins, inhibit bacterial and viral adhesion, suppress gastric secretions, promote bifidobacterial growth and modulate immune system responses. Of these, protection against toxins, bacteria, and viruses and modulation of the immune system are the most promising applications.

Glucose up-regulates expression of the differentiation-associated brush border binding site for enterotoxigenic Escherichia coli colonization factor antigen I in cultured human enterocyte-like cells

The association of enterotoxigenic Escherichia coli expressing colonization factor antigen I (CFA/I) with the cultured human colon adenocarcinoma cell, a model of the mature enterocyte of the small intestine, is dependent on the binding of CFA/I to a brush border-associated component. Binding of the purified radiolabeled [125I]CFA/I- and 14C-labeled CFA/I-positive bacteria could be displaced by an increasing concentration of unlabeled CFA/I. Moreover, we showed that expression of the specific CFA/I binding developed as a function of cell differentiation in Caco-2 cells, whereas expression of the nonspecific binding did not. Expression of the brush border differentiation-associated component acting as a binding site for CFA/I was up-regulated by glucose. Indeed, the enterocyte-like HT-29 glc- cell subpopulation not expressing the CFA/I binding site when cultured in dialyzed serum and hexose-free medium regained the ability to bind CFA/I when the cells were returned to culture medium containing glucose. Furthermore, expression of the brush border-associated CFA/I binding site in the enterocyte-like Caco-2 cells was repressed when the cells were cultured in hexose-free conditions.

Lactobacillus acidophilus LA 1 binds to cultured human intestinal cell lines and inhibits cell attachment and cell invasion by enterovirulent bacteria

Four human Lactobacillus acidophilus strains were tested for their ability to adhere onto human enterocyte like Caco-2 cells in culture. The LA 1 strain exhibited a high calcium independent adhesive property. This adhesion onto Caco-2 cells required a proteinaceous adhesion promoting factor, which was present in the spent bacterial broth culture supernatant. LA 1 strain also strongly bound to the mucus secreted by the homogeneous cultured human goblet cell line HT29-MTX. The inhibitory effect of LA 1 organisms against Caco-2 cell adhesion and cell invasion by a large variety of diarrhoeagenic bacteria was investigated. As a result, the following dose dependent inhibitions were obtained: (a) against the cell association of enterotoxigenic, diffusely adhering and enteropathogenic Escherichia coli, and Salmonella typhimurium; (b) against the cell invasion by enteropathogenic Escherichia coli, Yersinia pseudotuberculosis, and Salmonella typhimurium. Incubations of L acidophilus LA 1 before and together with enterovirulent E coli were more effective than incubation after infection by E coli.

In vitro inhibition of adhesion of Candida albicans clinical isolates to human buccal epithelial cells by Fuc alpha 1----2Gal beta-bearing complex carbohydrates

The role of cell surface glycoconjugates as possible adhesion receptors for Candida albicans yeasts on human buccal epithelial cells was investigated by using a quantitative radiometric assay involving 14C-metabolically labeled microorganisms. Various structurally defined soluble glycopeptides and oligosaccharides were tested at a low concentration (1 mg/ml) for their ability to competitively inhibit yeast adhesion to such exfoliated cells. Comparisons were also made with various molecular species previously proposed to act as adhesion molecules. A preparation of glycopeptides derived from pooled human newborn meconiums inhibited the attachment (up to 55%) of all three clinical isolates examined. The mild hydrolysis of fucosyl residues from the above mixture totally abolished its inhibitory potency. By using human milk oligosaccharide probes, the minimal structural requirement for activity was found to be the Fuc alpha 1----2Gal beta determinant (the H sugar sequence found on all blood group substances of the ABO [H] system). By contrast, the fucosylated determinants of the Lewis blood group system were found to be totally inactive. Total adhesion inhibitions were never obtained in the present experiments, suggesting that H disaccharide-bearing cell surface glycoconjugates could act as host receptors for C. albicans on human buccal epithelial cells as a part of a mechanism involving multireceptor specificities.

Specific and nonspecific inhibition of adhesion of oral actinomyces and streptococci to erythrocytes and polystyrene by caseinoglycopeptide derivatives

Various caseinoglycopeptide derivatives prepared from mammalian milk were evaluated as inhibitors of hemagglutinations mediated by Actinomyces viscosus Ny1, Streptococcus sanguis OMZ9, and, for comparative purposes, plant lectins from Arachis hypogaea and Bauhinia purpurea. It was found that recognition of the beta-D-galactose-(1----3)-2-acetamido-2-deoxy-D-galactose carbohydrate chain by Actinomyces viscosus Ny1 organisms and Arachis hypogaea and B. purpurea agglutinins had similar structural requirements; in all cases, the desialylated bovine caseinoglycomacropeptide, on which several units of the above mentioned disaccharide are clustered, behaved as the most potent hemagglutination inhibitor. By contrast, none of the preparations tested inhibited erythrocyte agglutination by S. sanguis OMZ9. Thus, the desialylated bovine caseinoglycomacropeptide acts as a potent and specific inhibitor of oral Actinomyces adhesion to cell membranes (a soft surface) and could be used as a probe for the study of recognition mechanisms mediated by Actinomyces galactose-binding lectins. During the present study, both native and desialylated variants of the same bovine glycomacropeptide also totally prevented the adhesion of Actinomyces viscosus Ny1, S. sanguis OMZ9, and S. mutans OMZ176 to polystyrene surfaces. Comparative evaluations of various structurally different compounds gave the following results. Neither mono- nor disaccharides related to caseinoglycopeptide carbohydrates prevented adhesion; highly positively or negatively charged polypeptides and polysaccharides were either not or only moderately active. Besides these glycomacropeptides, an inhibitory activity was also exhibited by other mucin-type glycoproteins carrying short O-linked carbohydrate chains (including bovine submaxillary mucin), polyethylene glycol, and bovine serum albumin. Consequently, caseinoglycopeptide prevention of oral bacterial adhesion to polystyrene tubes (a hard surface) takes place with no species specificity and can be compared to nonspecific inhibition exhibited by various polymers with very different structural characteristics.