Carbohydrate specificity of the surface lectins of Escherichia coli, Klebsiella pneumoniae, and Salmonella typhimurium

Antimicrobial, anti-inflammatory and anti-arthritic activity of hemolymph lectin (NagLec) isolated from the freshwater crab, Oziotelphusanaga

Lectins are non-immune glycoproteins or proteins having a unique capacity to interact with carbohydrate ligands found on the surface of their host cells. In the present investigation, the lectin was purified from the hemolymph of freshwater crab, Oziotelphusa naga and its antimicrobial, anti-inflammatory and anti-arthritic activity was analysed. The preliminary characterization of the hemagglutinin was carried out to identify the erythrocyte and sugar specificity, optimum pH and temperature and cation dependency. The agglutinin was found to be highly specific to rabbit erythrocyte and inhibited by fetuin and α-lactose. Maximum hemagglutination activity was noted at pH 7.5-8 and temperature 20-40 °C. An O-acetyl sialic acid specific 75 kDa hemolymph lectin, designated as NagLec was isolated from the freshwater crab, Oziotelphusa naga by affinity chromatography on fetuin coupled Sepharose 4 B, with a purification fold of 185. The bacteria Staphylococcus aureus, Proteus mirabilis and fungus Candida albicans had the greatest zone of inhibition when treated with NagLec. The results of the Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) assays showed that the purified lectin inhibited the growth of Staphylococcus aureus at 0.031 and 0.065 μg/ml, which proved the bactericidal property of NagLec. NagLec generated alterations on the bacterial cells and led to protein leakage, which was dosage (24 and 48 μg/ml) and time dependent (10-40 min). COX and LOX enzyme was inhibited to 49.43% and 61.81% with 100 μg/ml concentration of NagLec respectively, demonstrating NagLec's ability to reduce inflammation. Furthermore, NagLec (500 μg) suppressed protein denaturation up to 77.12% whereas diclofenac sodium (a standard drug) was inhibited by 89.36%. The results indicate that NagLec, a sialic acid specific lectin isolated from the freshwater crab O. naga could be formulated as a nano drug in future owing to its antimicrobial, anti-inflammatory and anti-arthritic potential that could be targeted to specific pathogenic microbes and treat arthritis.

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

Differential impact of yeast cell wall products in recovery of porcine intestinal epithelial cell barrier function following Lipopolysaccharide challenge

BACKGROUND

In swine intestinal barrier deterioration can be caused by exposure to harmful bacteria, toxins or contaminants that can lead to a leaky gut and post weaning diarrhoea. A leaky gut leads to increased infection, inflammation and poor nutrient absorption that can impair piglet growth and ultimately survival. Application of yeast cell wall (YCW) products may offer an opportunity to reduce the intestinal barrier damage caused by microbial challenge. A Mannan rich fraction (MRF) and three YCW products were compared by examining their impact on intestinal barrier function using a Jejunal model of intestine in response to a bacterial challenge using Salmonella LPS.

RESULTS

Trans epithelial electrical resistance (TEER) readings showed MRF had a significantly higher barrier function (P ≤ 0.05) over the positive control while YCW products A, B and C demonstrated no significant improvement to the positive control. Transcriptome analysis of the IPEC-J2 cells showed that differentially expressed genes associated with the gene ontology (GO) term for Structural molecule activity was significantly upregulated in the MRF treated cells over the positive control cells with 56 genes upregulated compared to product B (50 genes), Product C, (25 genes) and the negative control's 60 genes. Product A had no functional grouping under the structural molecule activity term. Both qPCR and western blotting analysis of tight junction associated genes showed that MRF treated cells demonstrated significantly higher Claudin 3 junctional gene expression (P ≤ 0.05) over the positive control and treatments A, B and C. Occludin expression was significantly higher in MRF treated cells (P ≤ 0.05) over the positive control and product B. A nonsignificant rise in TJP-1 gene expression was observed in the MRF treated cells when compared to the positive control. Protein abundances of Claudin 3, Occludin and TJP-1 were significantly (P ≤ 0.05) higher following MRF application to LPS challenged IPEC-J2 cells over the positive control.

CONCLUSIONS

The difference in each YCW products production and composition appeared to influence intestinal barrier integrity. The action of MRF demonstrates its potential ability to raise intestinal barrier integrity of IPEC-J2 intestinal cells on an in vitro level through significantly elevated intracellular connections.

Purification and structural characterization of lectin with antibacterial and anticancer properties from grubs of hide beetle, Dermestes frischii

Lectins or haemagglutinins are diverse classes of non-immune proteins; they bind to carbohydrates and are abundant in nature. In the present study, a coleopteran lectin from grubs of hide beetle, Dermestes frischii called DFL, was purified by glutaraldehyde (fixative-agent) fixed hen erythrocytes and characterized further for its functional properties. The purified DFL was stable between pH range 5 to 9 and heat-stable up to 50C. It was insensitive to EDTA and did not require any divalent cations. DFL native molecular mass was approximately 69 kDa with three different polypeptide subunits of 33 (pI ~4.4), 22 (pI ~6) and 14 (pI ~4.4) kDa. Haemagglutinating activity of DFL was highly inhibited by N-acetyl-D-glucosamine. DFL partial peptide sequences obtained from peptide mass fingerprinting experiments matched with amino acid sequences of lectins from different organisms confirmed its nature. Biological properties of purified DFL namely antibacterial and bacterial agglutination experiments revealed that DFL have both the effects against laboratory cultures of Aeromonas hydrophila, Enterococcus faecalis, Escherichia coli and habitat bacterial isolates of Staphylococcus cohnii and Bacillus cereus. In addition, the DFL exhibited substantial anticancer properties against HeLa cells. These results concluded that purified DFL could serve as a potent therapeutic agent for various biomedical applications.

Impact of down-stream processing on functional properties of yeasts and the implications on gut health of Atlantic salmon (Salmo salar)

Yeasts are becoming popular as novel ingredients in fish feeds because of their potential to support better growth and concomitantly ensure good fish health. Here, three species of yeasts (Cyberlindnera jadinii, Blastobotrys adeninivorans and Wickerhamomyces anomalus), grown on wood sugars and hydrolysates of chicken were subjected to two down-stream processes, either direct heat-inactivation or autolysis, and the feed potential of the resulting yeast preparations was assessed through a feeding trial with Atlantic salmon fry. Histological examination of distal intestine based on widening of lamina propria, showed that autolyzed W. anomalus was effective in alleviating mild intestinal enteritis, while only limited effects were observed for other yeasts. Our results showed that the functionality of yeast in counteracting intestinal enteritis in Atlantic salmon was dependent on both the type of yeast and the down-stream processing method, and demonstrated that C. jadinii and W. anomalus have promising effects on gut health of Atlantic salmon.

Developments in Mannose-Based Treatments for Uropathogenic Escherichia coli-Induced Urinary Tract Infections

During their lifetime almost half of women will experience a symptomatic urinary tract infection (UTI) with a further half experiencing a relapse within six months. Currently UTIs are treated with antibiotics, but increasing antibiotic resistance rates highlight the need for new treatments. Uropathogenic Escherichia coli (UPEC) is responsible for the majority of symptomatic UTI cases and thus has become a key pathological target. Adhesion of type one pilus subunit FimH at the surface of UPEC strains to mannose-saturated oligosaccharides located on the urothelium is critical to pathogenesis. Since the identification of FimH as a therapeutic target in the late 1980s, a substantial body of research has been generated focusing on the development of FimH-targeting mannose-based anti-adhesion therapies. In this review we will discuss the design of different classes of these mannose-based compounds and their utility and potential as UPEC therapeutics.

Secretory IgA N-glycans contribute to the protection against E. coli O55 infection of germ-free piglets

Mucosal surfaces are colonized by highly diverse commensal microbiota. Coating with secretory IgA (SIgA) promotes the survival of commensal bacteria while it inhibits the invasion by pathogens. Bacterial coating could be mediated by antigen-specific SIgA recognition, polyreactivity, and/or by the SIgA-associated glycans. In contrast to many in vitro studies, only a few reported the effect of SIgA glycans in vivo. Here, we used a germ-free antibody-free newborn piglets model to compare the protective effect of SIgA, SIgA with enzymatically removed N-glycans, Fab, and Fc containing the secretory component (Fc-SC) during oral necrotoxigenic E. coli O55 challenge. SIgA, Fab, and Fc-SC were protective, whereas removal of N-glycans from SIgA reduced SIgA-mediated protection as demonstrated by piglets' intestinal histology, clinical status, and survival. In vitro analyses indicated that deglycosylation of SIgA did not reduce agglutination of E. coli O55. These findings highlight the role of SIgA-associated N-glycans in protection. Further structural studies of SIgA-associated glycans would lead to the identification of those involved in the species-specific inhibition of attachment to corresponding epithelial cells.

Yeast cell wall mannan rich fraction modulates bacterial cellular respiration potentiating antibiotic efficacy

Now more than ever there is a demand to understand the mechanisms surrounding antibiotic resistance and look for alternative ways to impact phenotypic antibiotic outcome. Cellular energetics can be impacted by many bacteriostatic and bactericidal antibiotics, which affect metabolism and energy output, resulting in a reduction of cell growth or induction of cell death respectively. In this study, we provide evidence that a mannan rich fraction (MRF) from the cell wall of Saccharomyces cerevisiae modulates growth of antibiotic susceptible and resistant Escherichia coli and potentiates bactericidal antibiotic efficiency through modulation of bacterial cellular respiration. The role of MRF in modulating bactericidal impact and cellular metabolic state were assessed in E. coli by monitoring microbial growth and by measuring oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) using the Seahorse XFe96 Analyser, respectively. This work further illustrates the link between bacterial susceptibility to antibiotics (phenotypic resistance) and resistance through modulation of bacterial metabolism. This is the first example of yeast MRF enabling collateral sensitivity to antibiotics in vitro and supports the search for alternative strategies to promote animal health without contributing to the growing issue of antimicrobial resistance.

Supplementation of Yeast Cell Wall Fraction Tends to Improve Intestinal Health in Adult Dogs Undergoing an Abrupt Diet Transition

When owners decide to change their pet's food, a rapid transition may cause gastrointestinal distress. Yeast products may help with digestive upset during diet transition due to the bioactive compounds they possess, which may lead to improved intestinal morphology and integrity, modified gut microbiota, and modulated immune responses. The objective of this study was to determine the effects of a yeast cell wall fraction supplement on measures of gut integrity and fecal characteristics of adult dogs undergoing an abrupt diet transition. Twelve adult female beagles (mean age: 5.16 ± 0.87 years; mean body weight: 13.37 ± 0.68 kg) were used in a replicated 4 × 4 Latin square design with four 28-day experimental periods. During days 1-14, dogs were fed a dry kibble diet and supplemented with a placebo (cellulose; 125 mg/d) or yeast product (365 mg/d; equivalent to 0.2% of diet). During days 15-28, dogs remained on their placebo or yeast treatments but were rapidly transitioned to a canned diet or high-fiber diet. Fresh fecal samples were collected on days 13, 16, 20, 24, and 27 for measurement of pH, dry matter, calprotectin, immunoglobulin A (IgA), Escherichia coli, and Clostridium perfringens. Blood samples were collected on days 14, 17, and 28 to measure serum lipopolysaccharide-binding protein concentrations. All data were analyzed using the Mixed Models procedure of SAS 9.4. Fecal pH, dry matter, calprotectin, IgA, and E. coli were not affected (P > 0.05) by treatment before diet transition. Dogs supplemented with yeast cell wall fraction tended to have higher (P = 0.06) fecal C. perfringens counts than the controls. After diet transition, most parameters were not altered (P > 0.05) by treatment except that yeast-supplemented dogs tended to have higher (P = 0.06) fecal IgA than controls. Our results suggest that the yeast product may modestly improve intestinal health after an abrupt diet transition in adult dogs by enhancing intestinal immunity.

Inhibition of Salmonella Binding to Porcine Intestinal Cells by a Wood-Derived Prebiotic

Numerous Salmonellaenterica serovars can cause disease and contamination of animal-produced foods. Oligosaccharide-rich products capable of blocking pathogen adherence to intestinal mucosa are attractive alternatives to antibiotics as these have potential to prevent enteric infections. Presently, a wood-derived prebiotic composed mainly of glucose-galactose-mannose-xylose oligomers was found to inhibit mannose-sensitive binding of select SalmonellaTyphimurium and Escherichia coli strains when reacted with Saccharomyces boulardii. Tests for the ability of the prebiotic to prevent binding of a green fluorescent protein (GFP)-labeled S.Typhimurium to intestinal porcine epithelial cells (IPEC-J2) cultured in vitro revealed that prebiotic-exposed GFP-labeled S.Typhimurium bound > 30% fewer individual IPEC-J2 cells than did GFP-labeled S.Typhimurium having no prebiotic exposure. Quantitatively, 90% fewer prebiotic-exposed GFP-labeled S.Typhimurium cells were bound per individual IPEC-J2 cell compared to non-prebiotic exposed GFP-labeled S.Typhimurium. Comparison of invasiveness of S.Typhimurium DT104 against IPEC-J2 cells revealed greater than a 90% decrease in intracellular recovery of prebiotic-exposed S.Typhimurium DT104 compared to non-exposed controls (averaging 4.4 ± 0.2 log₁₀ CFU/well). These results suggest compounds within the wood-derived prebiotic bound to E. coli and S.Typhimurium-produced adhesions and in the case of S.Typhimurium, this adhesion-binding activity inhibited the binding and invasion of IPEC-J2 cells.

FimH and Anti-Adhesive Therapeutics: A Disarming Strategy Against Uropathogens

Chaperone-usher fimbrial adhesins are powerful weapons against the uropathogens that allow the establishment of urinary tract infections (UTIs). As the antibiotic therapeutic strategy has become less effective in the treatment of uropathogen-related UTIs, the anti-adhesive molecules active against fimbrial adhesins, key determinants of urovirulence, are attractive alternatives. The best-characterized bacterial adhesin is FimH, produced by uropathogenic Escherichia coli (UPEC). Hence, a number of high-affinity mono- and polyvalent mannose-based FimH antagonists, characterized by different bioavailabilities, have been reported. Given that antagonist affinities are firmly associated with the functional heterogeneities of different FimH variants, several FimH inhibitors have been developed using ligand-drug discovery strategies to generate high-affinity molecules for successful anti-adhesion therapy. As clinical trials have shown d-mannose's efficacy in UTIs prevention, it is supposed that mannosides could be a first-in-class strategy not only for UTIs, but also to combat other Gram-negative bacterial infections. Therefore, the current review discusses valuable and effective FimH anti-adhesive molecules active against UTIs, from design and synthesis to in vitro and in vivo evaluations.

Anti-Pathogenic Functions of Non-Digestible Oligosaccharides In Vitro

Non-digestible oligosaccharides (NDOs), complex carbohydrates that resist hydrolysis by salivary and intestinal digestive enzymes, fulfill a diversity of important biological roles. A lot of NDOs are known for their prebiotic properties by stimulating beneficial bacteria in the intestinal microbiota. Human milk oligosaccharides (HMOs) represent the first prebiotics that humans encounter in life. Inspired by these HMO structures, chemically-produced NDO structures (e.g., galacto-oligosaccharides and chito-oligosaccharides) have been recognized as valuable food additives and exert promising health effects. Besides their apparent ability to stimulate beneficial microbial species, oligosaccharides have shown to be important inhibitors of the development of pathogenic infections. Depending on the type and structural characteristics, oligosaccharides can exert a number of anti-pathogenic effects. The most described effect is their ability to act as a decoy receptor, thereby inhibiting adhesion of pathogens. Other ways of pathogenic inhibition, such as interference with pathogenic cell membrane and biofilm integrity and DNA transcription, are less investigated, but could be equally impactful. In this review, a comprehensive overview of In vitro anti-pathogenic properties of different NDOs and associated pathways are discussed. A framework is created categorizing all anti-pathogenic effects and providing insight into structural necessities for an oligosaccharide to exert one of these effects.

Mannan oligosaccharide supplementation in diets of sow and (or) their offspring improved immunity and regulated intestinal bacteria in piglet1

The objectives of the current study were to explore the effects of mannan oligosaccharide (MOS) supplementation in the diets of sow and (or) their offspring on intestinal bacteria, intestinal and systemic inflammation in the piglet. A total of 60 multiparous sows (4 ± 1 parity; Landrace × Yorkshire) were fed either control diet (sCON, n = 30) or a diet containing 400 mg kg-1 MOS (sMOS, n = 30) from day 86 of gestation until weaning (day 20 of postpartum). On day 7 of age, offspring (Duroc × Landrace Yorkshire) were assigned within sow treatments and fed control diet (pCON) or diet containing 800 mg kg-1 MOS (pMOS) for 28 d (end at 35 d of age), resulting in four piglet diet groups (n = 15 litters per diet group): sCON-pCON, sCON-pMOS, sMOS-pCON, and sMOS-pMOS. Results found that piglet diet MOS increased or tend to increase Lactobacillus amount in the ileum digesta (P < 0.01) and jejunum digesta (P = 0.07), respectively; while tend to decrease Escherichia coli amount in jejunum digesta (P =0.06) and cecum digesta (P = 0.08). Both sow and piglet diets add MOS (sMOS-pMOS) increased Lactobacillus amount but decreased E. coli amount in jejunum digesta (P < 0.05) compared with the sCON-pCON diet group. In addition, sow diet MOS (rather than piglet diet MOS) increased sIgA content in piglet jejunum mucosa compared with control (P = 0.04). Sow diet MOS decreased toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4), and interleukin 8 (IL-8) mRNA levels (P < 0.05) and tended to decrease nuclear factor-κB p65 (NF-κB p65) mRNA level (P = 0.07) in piglet intestinal lymphatic. The interaction effects between sow and piglet diets were found on the mRNA levels of NF- κB p65 (P = 0.03) and IL-8 (P = 0.02) in piglet jejunum. Finally, the sow diet MOS decreased proinflammatory cytokines IL-2 (P < 0.01) and IL-4 (P < 0.01) concentrations in piglet serum. Piglets diet MOS decreased the contents of IL-2 (P = 0.03), IL-4 (P = 0.01) and interferon (IFN)-γ (P < 0.01) while increased anti-inflammatory cytokine IL-10 (P < 0.01) content in serum. The interaction effects between sows and piglet diets on IL-4 (P = 0.02), IL-10 (P < 0.01), and IFN-γ (P = 0.08) were observed. In conclusion, sow and/or piglet diet MOS could improve intestinal microbiota, enhance intestinal mucosal immune competence, and suppress intestinal and systemic inflammation in the piglet.

The effects of coarse corn and refined functional carbohydrates on the live performance and cecal Salmonella prevalence in coccidiosis-vaccinated broilers1

The interaction between corn particle size and feed additives as it pertains to broiler live performance has been overlooked. This study evaluated the effects of corn particle size and refined-functional carbohydrates (RFC; 100 g/MT) on live performance and Salmonella prevalence in coccidiosis-vaccinated broilers. The following treatments were applied: fine corn (FC), coarse corn (CC), FC+RFC, CC+RFC, and CC+SAL (salinomycin). A natural, non-experimental necrotic enteritis (NE) outbreak began at 12 D of age, and mortality was impacted by dietary treatments. The use of RFC was observed to increase NE-associated mortality compared to broilers fed CC+SAL (P ≤ 0.10). At 19 D, greater than 50% of all broilers were found to be Salmonella-positive; however, at 48 D the use of RFC was shown to decrease cecal Salmonella prevalence. Although differences in early mortality were observed, coccidiosis-vaccinated broilers fed CC or CC+RFC exhibited similar BW and FCR as broilers fed CC+SAL at 48 D (P ≤ 0.05). These data suggested that CC use after 10 D may provide value in a production system free of antibiotic growth promoters and coccidiostats by ameliorating live performance losses associated with coccidiosis vaccination. Further research is warranted to determine how RFC and CC specifically affect Eimeria cycling and the immune response following coccidiosis vaccination and an NE challenge.

Immunomodulatory effects of whole yeast cells and capsicum in weanling pigs challenged with pathogenic Escherichia coli1

An experiment was conducted to evaluate growth performance, fecal bacterial counts, frequency of diarrhea, and clinical blood parameters in weanling pigs inoculated with enterotoxigenic Escherichia coli (ETEC) who were fed a whole yeast cell (WYC) product and capsicum, a plant essential oil. Weanling pigs (34 barrows and 30 gilts, 21 d of age, 5.90 ± 1.03 kg BW) were allotted to experimental treatments in a randomized complete block design based on litter, sex, and initial BW. Four pigs were individually housed within each containment chamber and assigned to 1 of 4 dietary treatments, which included a control diet without or with 0.2% WYC (CitriStim; ADM, Decatur, IL) or 10 ppm of capsicum (XTract 6933; Pancosma, Geneva, Switzerland), provided either alone or in combination. After receiving diets for 13 d, pigs were orally inoculated with F18+ ETEC and maintained on their assigned diets for an additional 10 d; a separate cohort of 12 pigs receiving the control diet was sham-inoculated using PBS. Body and feeder weights were recorded, and fecal swabs collected, on 0, 5, and 10 d postinoculation (DPI), with blood sampled at 0, 2, 7, and 10 DPI for isolation of peripheral blood mononuclear cells. Pigs challenged with ETEC and fed diets containing WYC or capsicum alone had a higher frequency of diarrhea when compared with pigs receiving diets without those compounds (P < 0.05). Total fecal bacterial counts in pigs fed the combination of additives were highest when compared with either additive alone (interaction, P = 0.03) at 10 DPI. Blood leukocyte counts were increased in challenged pigs receiving the combination of additives compared with all other challenged treatment groups (interaction, P = 0.04). The addition of WYC increased (main effect, P = 0.01) lymphocyte counts at 7 DPI. Proportions of CD8+ and CD4+CD8+ cells were lower in pigs fed the combination of additives compared with pigs fed either additive alone at 0 and 7 DPI. In conclusion, these data indicate that the combination of the 2 additives elicited higher ETEC shedding and circulating leukocyte counts, and reduced the proportions of cytotoxic and memory T-cells than either additive alone.

Everything You Always Wanted to Know About Salmonella Type 1 Fimbriae, but Were Afraid to Ask

Initial attachment to host intestinal mucosa after oral infection is one of the most important stages during bacterial pathogenesis. Adhesive structures, widely present on the bacterial surface, are mainly responsible for the first contact with host cells and of host-pathogen interactions. Among dozens of different bacterial adhesins, type 1 fimbriae (T1F) are one of the most common adhesive organelles in the members of the Enterobacteriaceae family, including Salmonella spp., and are important virulence factors. Those long, thin structures, composed mainly of FimA proteins, are responsible for recognizing and binding high-mannose oligosaccharides, which are carried by various glycoproteins and expressed at the host cell surface, via FimH adhesin, which is presented at the top of T1F. In this review, we discuss investigations into the functions of T1F, from the earliest work published in 1958 to operon organization, organelle structure, T1F biogenesis, and the various functions of T1F in Salmonella-host interactions. We give special attention to regulation of T1F expression and their role in binding of Salmonella to cells, cell lines, organ explants, and other surfaces with emphasis on biofilm formation and discuss T1F role as virulence factors based on work using animal models. We also discuss the importance of allelic variation in fimH to Salmonella pathogenesis, as well as role of FimH in Salmonella host specificity.

Sialylated Oligosaccharides and Glycoconjugates of Human Milk. The Impact on Infant and Newborn Protection, Development and Well-Being

Human milk not only has nutritional value, but also provides a wide range of biologically active molecules, which are adapted to meet the needs of newborns and infants. Mother’s milk is a source of sialylated oligosaccharides and glycans that are attached to proteins and lipids, whose concentrations and composition are unique. Sialylated human milk glycoconjugates and oligosaccharides enrich the newborn immature immune system and are crucial for their proper development and well-being. Some of the milk sialylated oligosaccharide structures can locally exert biologically active effects in the newborn’s and infant’s gut. Sialylated molecules of human milk can be recognized and bound by sialic acid-dependent pathogens and inhibit their adhesion to the epithelial cells of newborns and infants. A small amount of intact sialylated oligosaccharides can be absorbed from the intestine and remain in the newborn’s circulation in concentrations high enough to modulate the immunological system at the cellular level and facilitate proper brain development during infancy. Conclusion: The review summarizes the current state of knowledge on sialylated human milk oligosaccharides and glycoconjugates, discusses the significance of sialylated structures of human milk in newborn protection and development, and presents the advantages of human milk over infant formula.

Emerging nano-biosensing with suspended MNP microbial extraction and EANP labeling

Emerging nano-biosensing with suspended MNP microbial extraction and EANP labeling may ensure a secure microbe-free food supply, as rapid response detection of microbial contamination is of utmost importance. Many biosensor designs have been proposed over the past two decades, covering a broad range of binding ligands, signal amplification, and detection mechanisms. These designs may consist of self-contained test strips developed from the base up with complicated nanoparticle chemistry and intricate ligand immobilization. Other methods use multiple step-wise additions, many based upon ELISA 96-well plate technology with fluorescent detection. In addition, many biosensors use expensive antibody receptors or DNA ligands. But many of these proposed designs are impracticable for most applications or users, since they don't FIRST address the broad goals of any biosensor: Field operability, Inexpensive, with Real-time detection that is both Sensitive and Specific to target, while being as Trouble-free as possible. Described in this review are applications that utilize versatile magnetic nanoparticles (MNP) extraction, electrically active nanoparticles (EANP) labeling, and carbohydrate-based ligand chemistry. MNP provide rapid pathogen extraction from liquid samples. EANP labeling improves signal amplification and expands signaling options to include optical and electrical detection. Carbohydrate ligands are inexpensive, robust structures that are increasingly synthesized for higher selectivity. Used in conjunction with optical or electrical detection of gold nanoparticles (AuNP), carbohydrate-functionalized MNP-cell-AuNP nano-biosensing advances the goal of being the FIRST biosensor of choice in detecting microbial pathogens throughout our food supply chain.

Developments in strategies for Quorum Sensing virulence factor inhibition to combat bacterial drug resistance

Quorum sensing (QS) is a complex bacterial intercellular communication system. It is mediated by molecules called auto-inducers (AIs) and allows coordinated responses to a variety of environmental signals by inducing alterations in gene expression. Communication through QS can tremendously stimulate the pathogenicity and virulence via multiple mechanisms in pathogenic bacteria. The present review explores the major types of multitudinous QS systems known in Gram-positive and Gram-negative bacteria and their roles in bacterial pathogenesis and drug resistance. Because bacterial resistance to antibiotics is increasingly becoming a significant clinical challenge to human health; alternate strategies to combat drug resistance are warranted. Targeting bacterial pathogenicity by interruptions in QS using natural QS inhibitors and synthetic quorum-quenching analogs are being increasingly considered for development of next generation antimicrobials. The review highlights the recent advancements in discovery of promising new QS modulators and their efficiency in controlling infections caused by multidrug-resistant bacterial pathogens.

Sites for Dynamic Protein-Carbohydrate Interactions of O- and C-Linked Mannosides on the E. coli FimH Adhesin

Antagonists of the Escherichia coli type-1 fimbrial adhesin FimH are recognized as attractive alternatives for antibiotic therapies and prophylaxes against acute and recurrent bacterial infections. In this study α-d-mannopyranosides O- or C-linked with an alkyl, alkene, alkyne, thioalkyl, amide, or sulfonamide were investigated to fit a hydrophobic substituent with up to two aryl groups within the tyrosine gate emerging from the mannose-binding pocket of FimH. The results were summarized into a set of structure-activity relationships to be used in FimH-targeted inhibitor design: alkene linkers gave an improved affinity and inhibitory potential, because of their relative flexibility combined with a favourable interaction with isoleucine-52 located in the middle of the tyrosine gate. Of particular interest is a C-linked mannoside, alkene-linked to an ortho-substituted biphenyl that has an affinity similar to its O-mannosidic analog but superior to its para-substituted analog. Docking of its high-resolution NMR solution structure to the FimH adhesin indicated that its ultimate, ortho-placed phenyl ring is able to interact with isoleucine-13, located in the clamp loop that undergoes conformational changes under shear force exerted on the bacteria. Molecular dynamics simulations confirmed that a subpopulation of the C-mannoside conformers is able to interact in this secondary binding site of FimH.

Rational design strategies for FimH antagonists: new drugs on the horizon for urinary tract infection and Crohn's disease

INTRODUCTION

The bacterial adhesin FimH is a virulence factor and an attractive therapeutic target for urinary tract infection (UTI) and Crohn's Disease (CD). Located on type 1 pili of uropathogenic E. coli (UPEC), the FimH adhesin plays an integral role in the pathogenesis of UPEC. Recent efforts have culminated in the development of small-molecule mannoside FimH antagonists that target the mannose-binding lectin domain of FimH, inhibiting its function and preventing UPEC from binding mannosylated host cells in the bladder, thereby circumventing infection. Areas covered: The authors describe the structure-guided design of mannoside ligands, and review the structural biology of the FimH lectin domain. Additionally, they discuss the lead optimization of mannosides for therapeutic application in UTI and CD, and describe various assays used to measure mannoside potency in vitro and mouse models used to determine efficacy in vivo. Expert opinion: To date, mannoside optimization has led to a diverse set of small-molecule FimH antagonists with oral bioavailability. With clinical trials already initiated in CD and on the horizon for UTI, it is the authors, opinion that mannosides will be a 'first-in-class' treatment strategy for UTI and CD, and will pave the way for treatment of other Gram-negative bacterial infections.

Identification of Multiple Druggable Secondary Sites by Fragment Screening against DC-SIGN

DC-SIGN is a cell-surface receptor for several pathogenic threats, such as HIV, Ebola virus, or Mycobacterium tuberculosis. Multiple attempts to develop inhibitors of the underlying carbohydrate-protein interactions have been undertaken in the past fifteen years. Still, drug-like DC-SIGN ligands are sparse, which is most likely due to its hydrophilic, solvent-exposed carbohydrate-binding site. Herein, we report on a parallel fragment screening against DC-SIGN applying SPR and a reporter displacement assay, which complements previous screenings using ¹⁹ F NMR spectroscopy and chemical fragment microarrays. Hit validation by SPR and ¹ H-¹⁵ N HSQC NMR spectroscopy revealed that although no fragment bound in the primary carbohydrate site, five secondary sites are available to harbor drug-like molecules. Building on key interactions of the reported fragment hits, these pockets will be targeted in future approaches to accelerate the development of DC-SIGN inhibitors.

Prodruggability of carbohydrates — oral FimH antagonists

The bacterial lectin FimH is a promising therapeutic target for the nonantibiotic prevention and treatment of urinary tract infections. In this communication, an ester prodrug approach is described to achieve oral bioavailability for FimH antagonists. By introducing short-chain acyl promoieties at the C-6 position of a biphenyl α-d-mannopyranoside, prodrugs with an excellent absorption potential were obtained. The human carboxylesterase 2 was identified as a main enzyme mediating rapid bioconversion to the active principle. Despite their propensity to hydrolysis within the enterocytes during absorption, these ester prodrugs present a considerable progress in the development of orally available FimH antagonists.

FimH Antagonists: Phosphate Prodrugs Improve Oral Bioavailability

The widespread occurrence of urinary tract infections has resulted in frequent antibiotic treatment, contributing to the emergence of antimicrobial resistance. Alternative approaches are therefore required. In the initial step of colonization, FimH, a lectin located at the tip of bacterial type 1 pili, interacts with mannosylated glycoproteins on the urothelial mucosa. This initial pathogen/host interaction is efficiently antagonized by biaryl α-d-mannopyranosides. However, their poor physicochemical properties, primarily resulting from low aqueous solubility, limit their suitability as oral treatment option. Herein, we report the syntheses and pharmacokinetic evaluation of phosphate prodrugs, which show an improved aqueous solubility of up to 140-fold. In a Caco-2 cell model, supersaturated solutions of the active principle were generated through hydrolysis of the phosphate esters by brush border-associated enzymes, leading to a high concentration gradient across the cell monolayer. As a result, the in vivo application of phosphate prodrugs led to a substantially increased Cmax and prolonged availability of FimH antagonists in urine.

A review of 733 published trials on Bio-Mos®, a mannan oligosaccharide, and Actigen®, a second generation mannose rich fraction, on farm and companion animals

Mannan-oligosaccharides (MOS), as zootechnical feed ingredients, are widely used in animal nutrition. MOS has been commercially available since the launch of Bio-Mos® in the early 1990's and has a substantial body of scientific papers and practical examples of its efficacy. Since 1999, the use of MOS in animal feed has become more prominent, mainly due to the European ban on prophylactic antibiotic growth promoters in animal feed. MOS, with its ability to bind and limit the colonisation of gut pathogens, has proven to be an effective solution for antibiotic-free diets, as well as providing support for immunity and digestion. MOS has been shown to improve gastrointestinal health, thus improving wellbeing, energy levels and performance. Most MOS products, particularly those that have been scientifically developed, derive from the cell wall of the yeast,Saccharomyces cerevisiae. In 2009, a mannose-rich fraction (MRF) product was commercially launched as a ‘second generation’ of these MOS-type products, with enhanced activities in immune modulation and intestinal health. The purpose of this paper is to review the existing data on the benefits of MOS for all species of animals, discuss its mechanisms of actionin vivoand compare the benefits of using second generation MRF to original MOS.

FimH antagonists: bioisosteres to improve the in vitro and in vivo PK/PD profile

Urinary tract infections (UTIs), predominantly caused by uropathogenic Escherichia coli (UPEC), belong to the most prevalent infectious diseases worldwide. The attachment of UPEC to host cells is mediated by FimH, a mannose-binding adhesin at the tip of bacterial type 1 pili. To date, UTIs are mainly treated with antibiotics, leading to the ubiquitous problem of increasing resistance against most of the currently available antimicrobials. Therefore, new treatment strategies are urgently needed. Here, we describe the development of an orally available FimH antagonist. Starting from the carboxylate substituted biphenyl α-d-mannoside 9, affinity and the relevant pharmacokinetic parameters (solubility, permeability, renal excretion) were substantially improved by a bioisosteric approach. With 3'-chloro-4'-(α-d-mannopyranosyloxy)biphenyl-4-carbonitrile (10j) a FimH antagonist with an optimal in vitro PK/PD profile was identified. Orally applied, 10j was effective in a mouse model of UTI by reducing the bacterial load in the bladder by about 1000-fold.

Effect of inulin and mannan-oligosaccharides compared with zinc-bacitracin on growing performance, nutrient digestibility and hematological profiles of growing rabbits

The study aimed to evaluate the effect of inulin and mannan-oligosaccharides (MOS) vs zinc-bacitracin (ZnB) on rabbit growth performance, nutrient digestibility, and blood profiles. In total, 108 rabbits 32 days of age were divided into four homogeneous groups fed the same basal diet and submitted to the following dietary treatments: control group, without supplementation; inulin group, supplemented with inulin (0.25 g/rabbit.day); MOS group, supplemented with MOS (0.083 g/rabbit.day); and ZnB group, supplemented with ZnB (0.083 g/rabbit.day). The supplements were administered 2 days per week from 32 to 81 days of age. At 32, 56 and 81 days, the rabbits were weighed and feed intake was measured. Mortality was recorded daily. Nutrient digestibility was measured at 65 days by an ingesta–excreta balance. Samples of blood were collected at 53, 67 and 81 days of age. The control group showed the highest (P < 0.01) mortality rate throughout the trial (17.0%), followed by ZnB (8.18%), inulin (3.7%) and then the MOS group, which had the lowest mortality (1.6%; P < 0.01). Addition of MOS led to a more favourable (P < 0.05) feed conversion ratio than addition of ZnB at 32–56 days of age and inulin for the entire trial period. The MOS group showed increased (P < 0.01) digestibility of dry matter, organic matter, ash and crude fibre relative to the control group. All supplements increased (P < 0.01) protein digestibility relative to the control. The level of alanine aminotransferase was reduced due to the use of feed supplements, and MOS supplementation gave the lowest (P < 0.01) value. Administration of prebiotics to growing rabbits as an alternative to ZnB can lead some advantages compared with both antibiotic and unsupplemented diets; MOS was more effective than inulin.

Branched α-d-mannopyranosides: a new class of potent FimH antagonists

We report branched α-d-mannopyranosides as potent FimH antagonists that exploit the previously unexplored lipophilic region formed by Phe142 and Ile13.

Effect of Aminophenyl and Aminothiahexyl α-D-Glycosides of the Manno-, Gluco-, and Galacto-Series on Type 1 Fimbriae-Mediated Adhesion of Escherichia coli

Adhesion of bacteria to the glycosylated surface of their target cells is typically mediated by fimbrial lectins, exposed on the bacterial surface. Among the best-investigated and most important fimbriae are type 1 fimbriae, for which α-d-mannopyranoside-specificity has been described. This carbohydrate specificity is mediated by the type 1 fimbrial lectin FimH. In this account, we have employed four different set-ups to assay type 1 fimbriae-mediated bacterial adhesion, including tailor-made glycoarrays. The focus of our study was on testing FimH specificity with regard to the glycone part of a glycosidic ligand by testing a series of synthetic α-mannosides, as well as α-glucosides and α-galactosides. Unexpectedly, it was found that in solution all tested aminothiahexyl glycosides inhibit bacterial adhesion but that this effect is unspecific. Instead it is due to cytotoxicity of the respective glycosides at high mm concentrations.

Effect of dietary prebiotic (mannan oligosaccharide) supplementation on the caecal bacterial community structure of turkeys

The identification of specific bacterial species influenced by mannan oligosaccharide (MOS) supplementation may assist in the formulation of new and improved diets that promote intestinal health and improve bird performance, offering suitable alternatives to antimicrobials in feed for sustainable poultry production. This study has been conducted to evaluate the use of a MOS compound derived from the yeast cell wall of Saccharomyces cerevisiae on turkey performance, bacterial community structure and their phylogenetic associations. A 42-day turkey trial was carried out on birds fed control and MOS-supplemented diets. Bird performance data (weight gains, feed consumption and feed efficiency ratios) were collected, and caecal contents were extracted from randomly caught poults on days 28, 35 and 42 posthatch. Bird performance data showed no improvements as a result of dietary supplementation. Automated ribosomal intergenic spacer analysis (ARISA) revealed the bacterial community structure to be significantly altered on days 28 and 35 posthatch but not day 42 as a result of dietary supplementation. This technique was coupled with 16S rRNA gene sequence analysis to elucidate phylogenetic identities of bacteria. The dominant bacteria of the caecum on all days in both treatment groups were members of phylum Firmicutes, followed by the Bacteroidetes and Proteobacteria phyla, respectively. Statistical analysis of the 16S rRNA gene libraries showed that the composition of the MOS clone library differed significantly to the control on day 35 posthatch. It can be concluded that MOS alters the bacterial community structure in the turkey caecum.

Structural insight in histo-blood group binding by the F18 fimbrial adhesin FedF

F18-positive enterotoxigenic and Shiga toxin-producing Escherichia coli are responsible for post-weaning diarrhoea and oedema disease in pigs and lead to severe production losses in the farming industry. F18 fimbriae attach to the small intestine of young piglets by latching onto glycosphingolipids with A/H blood group determinants on type 1 core. We demonstrate the N-terminal domain of the F18 fimbrial subunit FedF to be responsible for ABH-mediated attachment and present its X-ray structure in ligand-free form and bound to A and B type 1 hexaoses. The FedF lectin domain comprises a 10-stranded immunoglobulin-like β-sandwich. Three linear motives, Q(47) -N(50), H(88) -S(90) and R(117) -T(119), form a shallow glycan binding pocket near the tip of the domain that is selective for type 1 core glycans in extended conformation. In addition to the glycan binding pocket, a polybasic loop on the membrane proximal surface of FedF lectin domain is shown to be required for binding to piglet enterocytes. Although dispensable for ABH glycan recognition, the polybasic surface adds binding affinity in the context of the host cell membrane, a mechanism that is proposed to direct ABH-glycan binding to cell-bound glycosphingolipids and could allow bacteria to avoid clearance by secreted glycoproteins.

A modified glucomannan mycotoxin-adsorbing agent counteracts the reduced weight gain and diminishes cecal colonization of Salmonella Typhimurium in T-2 toxin exposed pigs

The aim of the study was to investigate the effect of a modified glucomannan binder on the course of a Salmonella Typhimurium infection in pigs. Therefore, four pig diets were provided during 23 days: (1) free of mycotoxins, (2) containing 1g binder per kg feed, (3) containing 83 μg T-2 toxin per kg feed and (4) containing 83 μg T-2 toxin and 1g binder per kg feed. After 18 days, all pigs were inoculated with Salmonella Typhimurium and euthanized five days later. The addition of the binder to T-2 toxin contaminated feed counteracted the reduced weight gain of pigs caused by T-2 toxin and reduced the amount of Salmonella Typhimurium in the cecum and cecal contents. In vitro findings might indicate that the binder captures Salmonella. We thus conclude that the binder counteracts T-2 toxin induced weight loss and possibly binds Salmonella, resulting in a reduced cecal colonization.

FimH antagonists: structure-activity and structure-property relationships for biphenyl α-D-mannopyranosides

Urinary tract infections (UTIs) are caused primarily by uropathogenic Escherichia coli (UPEC), which encode filamentous surface-adhesive organelles called type 1 pili. FimH is located at the tips of these pili. The initial attachment of UPEC to host cells is mediated by the interaction of the carbohydrate recognition domain (CRD) of FimH with oligomannosides on urothelial cells. Blocking these lectins with carbohydrates or analogues thereof prevents bacterial adhesion to host cells and therefore offers a potential therapeutic approach for prevention and/or treatment of UTIs. Although numerous FimH antagonists have been developed so far, few of them meet the requirement for clinical application due to poor pharmacokinetics. Additionally, the binding mode of an antagonist to the CRD of FimH can switch from an in-docking mode to an out-docking mode, depending on the structure of the antagonist. In this communication, biphenyl α-D-mannosides were modified to improve their binding affinity, to explore their binding mode, and to optimize their pharmacokinetic properties. The inhibitory potential of the FimH antagonists was measured in a cell-free competitive binding assay, a cell-based flow cytometry assay, and by isothermal titration calorimetry. Furthermore, pharmacokinetic properties such as log D, solubility, and membrane permeation were analyzed. As a result, a structure-activity and structure-property relationships were established for a series of biphenyl α-D-mannosides.