Inhibitory effects of bovine lactoferrin on the adherence of enterotoxigenic Escherichia coli to host cells

The Role of Lactoferrin in Intestinal Health

The intestine represents one of the first barriers where microorganisms and environmental antigens come into tight contact with the host immune system. A healthy intestine is essential for the well-being of humans and animals. The period after birth is a very important phase of development, as the infant moves from a protected environment in the uterus to one with many of unknown antigens and pathogens. In that period, mother's milk plays an important role, as it contains an abundance of biologically active components. Among these components, the iron-binding glycoprotein, lactoferrin (LF), has demonstrated a variety of important benefits in infants and adults, including the promotion of intestinal health. This review article aims to provide a compilation of all the information related to LF and intestinal health, in infants and adults.

Effect of bovine lactoferrin on recurrent urinary tract infections: in vitro and in vivo evidences

Uropathogenic Escherichia coli (UPEC) strains are the primary cause of urinary tract infections (UTIs). UPEC strains are able to invade, multiply and persisting in host cells. Therefore, UPEC strains are associated to recurrent UTIs requiring long-term antibiotic therapy. However, this therapy is suboptimal due to the increase of multidrug-resistant UPEC. The use of non-antibiotic treatments for managing UTIs is required. Among these, bovine lactoferrin (bLf), a multifunctional cationic glycoprotein, could be a promising tool because inhibits the entry into the host cells of several intracellular bacteria. Here, we demonstrate that 100 μg/ml bLf hinders the invasion of 2.0 ± 0.5 × 10⁴ CFU/ml E. coli CFT073, prototype of UPEC, infecting 2.0 ± 0.5 × 10⁵ cells/ml urinary bladder T24 epithelial cells. The highest protection (100%) is due to the bLf binding with host surface components even if an additional binding to bacterial surface components cannot be excluded. Of note, in the absence of bLf, UPEC survives and multiplies, while bLf significantly decreases bacterial intracellular survival. After these encouraging results, an observational survey on thirty-three patients affected by recurrent cystitis was performed. The treatment consisted in the oral administration of bLf alone or in combination with antibiotics and/or probiotics. After the observation period, a marked reduction of cystitis episodes was observed (p < 0.001) in all patients compared to the episodes occurred during the 6 months preceding the bLf-treatment. Twenty-nine patients did not report cystitis episodes (87.9%) whereas the remaining four (12.1%) experienced only one episode, indicating that bLf could be a worthwhile and safe treatment in counteracting recurrent cystitis.

Diverse Mechanisms of Antimicrobial Activities of Lactoferrins, Lactoferricins, and Other Lactoferrin-Derived Peptides

Lactoferrins are an iron-binding glycoprotein that have important protective roles in the mammalian body through their numerous functions, which include antimicrobial, antitumor, anti-inflammatory, immunomodulatory, and antioxidant activities. Among these, their antimicrobial activity has been the most studied, although the mechanism behind antimicrobial activities remains to be elucidated. Thirty years ago, the first lactoferrin-derived peptide was isolated and showed higher antimicrobial activity than the native lactoferrin lactoferricin. Since then, numerous studies have investigated the antimicrobial potencies of lactoferrins, lactoferricins, and other lactoferrin-derived peptides to better understand their antimicrobial activities at the molecular level. This review defines the current antibacterial, antiviral, antifungal, and antiparasitic activities of lactoferrins, lactoferricins, and lactoferrin-derived peptides. The primary focus is on their different mechanisms of activity against bacteria, viruses, fungi, and parasites. The role of their structure, amino-acid composition, conformation, charge, hydrophobicity, and other factors that affect their mechanisms of antimicrobial activity are also reviewed.

Lactoferrin in the Prevention and Treatment of Intestinal Inflammatory Pathologies Associated with Colorectal Cancer Development

The connection between inflammation and cancer is well-established and supported by genetic, pharmacological and epidemiological data. The inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis, have been described as important promoters for colorectal cancer development. Risk factors include environmental and food-borne mutagens, dysbalance of intestinal microbiome composition and chronic intestinal inflammation, with loss of intestinal epithelial barrier and enhanced cell proliferation rate. Therapies aimed at shutting down mucosal inflammatory response represent the foundation for IBDs treatment. However, when applied for long periods, they can alter the immune system and promote microbiome dysbiosis and carcinogenesis. Therefore, it is imperative to find new safe substances acting as both potent anti-inflammatory and anti-pathogen agents. Lactoferrin (Lf), an iron-binding glycoprotein essential in innate immunity, is generally recognized as safe and used as food supplement due to its multifunctionality. Lf possesses a wide range of immunomodulatory and anti-inflammatory properties against different aseptic and septic inflammatory pathologies, including IBDs. Moreover, Lf exerts anti-adhesive, anti-invasive and anti-survival activities against several microbial pathogens that colonize intestinal mucosa of IBDs patients. This review focuses on those activities of Lf potentially useful for the prevention/treatment of intestinal inflammatory pathologies associated with colorectal cancer development.

Porcine and Bovine Forms of Lactoferrin Inhibit Growth of Porcine Enterotoxigenic Escherichia coli and Degrade Its Virulence Factors

Postweaning diarrhea (PWD) is an economically important, multifactorial disease affecting pigs within the first 2 weeks after weaning. The most common agent associated with PWD is enterotoxigenic Escherichia coli (ETEC). Currently, antibiotics are used to control PWD, and this has most likely contributed to an increased prevalence of antibiotic-resistant strains. This puts pressure on veterinarians and farmers to decrease or even abandon the use of antibiotics, but these measures need to be supported by alternative strategies for controlling these infections. Naturally derived molecules, such as lactoferrin, could be potential candidates due to their antibacterial or immune-modulating activities. Here, we analyzed the ability of bovine lactoferrin (bLF), porcine lactoferrin (pLF), and ovotransferrin (ovoTF) to inhibit ETEC growth, degrade ETEC virulence factors, and inhibit adherence of these pathogens to porcine intestinal epithelial cells. Our results revealed that bLF and pLF, but not ovoTF, inhibit the growth of ETEC. Furthermore, bLF and pLF can degrade several virulence factors produced by ETEC strains, more specifically F4 fimbriae, F18 fimbriae, and flagellin. On the other hand, ovoTF degrades F18 fimbriae and flagellin but not F4 fimbriae. An in vitro adhesion assay showed that bLF, ovoTF, and pLF can decrease the number of bacteria adherent to epithelial cells. Our findings demonstrate that lactoferrin can directly affect porcine ETEC strains, which could allow lactoferrin to serve as an alternative to antimicrobials for the prevention of ETEC infections in piglets.IMPORTANCE Currently, postweaning F4⁺ and F18⁺ Escherichia coli infections in piglets are controlled by the use of antibiotics and zinc oxide, but the use of these antimicrobial agents most likely contributes to an increase in antibiotic resistance. Our work demonstrates that bovine and porcine lactoferrin can inhibit the growth of porcine enterotoxigenic E. coli strains. In addition, we also show that lactoferrin can reduce the adherence of these strains to small intestinal epithelial cells, even at a concentration that does not inhibit bacterial growth. This research could allow us to develop lactoferrin as an alternative strategy to prevent enterotoxigenic E. coli (ETEC) infections in piglets.

Enterotoxigenic Escherichia coli Heat-Stable Toxin Increases the Rate of Zinc Release from Metallothionein and Is a Zinc- and Iron-Binding Peptide

Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries. Previous studies have identified heat-stable enterotoxin (ST)-producing ETEC as one of the major diarrhea-causing pathogens in children younger than five years. In this study, we examined iron and zinc binding by both human and porcine ST variants and determined how host metallothionein could detoxify ST. We found that ST purified from ETEC culture supernatants eluted as a doublet during C18 reverse-phase chromatography. Leading edge fractions of the ST doublet were found to be devoid of iron, while trailing edge fractions of the ST doublet were found to contain measurable iron. Next, we found that purified ST could be reconstituted with iron under reducing and anaerobic conditions, and iron-bound ST attenuated the induction of cGMP in T84 epithelial cells. Moreover, we demonstrated that supernatants of ETEC 214-4 grown under increasing iron concentrations were only able to induce cGMP at iron concentrations greater than 5 μM. In vitro studies also demonstrated that ST binds zinc, and once bound, zinc removal from ST required denaturing conditions. Zinc-bound ST also failed to induce cGMP. We found that ST contributes disulfide bonds to the perceived oxidized glutathione pool, increases the rate of zinc release from metallothionein, and can be detoxified by metallothionein. Lastly, we showed ST induces transcriptional changes in genes previously shown to be regulated by deferoxamine. These studies demonstrate ST ETEC pathogenesis may be tied intimately to host mucosal metal status.IMPORTANCE Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries, deployed military personnel, and travelers to regions of endemicity. The heat-stable toxin (ST) is a small nonimmunogenic secreted peptide with 3 disulfide bonds. It has been appreciated that dietary disulfides modulate intestinal redox potential and that ST could be detoxified using exogenous reductants. Using biochemical and spectroscopic approaches, we demonstrated that ST can separately bind iron and zinc under reducing conditions, thereby reducing ST toxicity. Moreover, we demonstrated that ST modulates the glutathione (GSH)/oxidized glutathione (GSSG) ratio and that ST should be considered a toxin oxidant. ST can be detoxified by oxidizing zinc-loaded metallothionine, causing free zinc to be released. These studies help lay a foundation to understand how diarrheal pathogens modulate intestinal redox potential and may impact how we design therapeutics and/or vaccines for the pathogens that produce them.

Bovine Lactoferrin Pre-Treatment Induces Intracellular Killing of AIEC LF82 and Reduces Bacteria-Induced DNA Damage in Differentiated Human Enterocytes

LF82, a prototype of adherent-invasive E. coli (AIEC), is able to adhere to, invade, survive and replicate into intestinal epithelial cells. LF82 is able to enhance either its adhesion and invasion by up-regulating carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM-6), the main cell surface molecule for bacterial adhesion, and its intracellular survival by inducing host DNA damage, thus blocking the cellular cycle. Lactoferrin (Lf) is a multifunctional cationic glycoprotein of natural immunity, exerting an anti-invasive activity against LF82 when added to Caco-2 cells at the moment of infection. Here, the infection of 12 h Lf pre-treated Caco-2 cells was carried out at a time of 0 or 3 or 10 h after Lf removal from culture medium. The effect of Lf pre-treatment on LF82 invasiveness, survival, cell DNA damage, CEACAM-6 expression, apoptosis induction, as well as on Lf subcellular localization, has been evaluated. Lf, even if removed from culture medium, reduced LF82 invasion and survival as well as bacteria-induced DNA damage in Caco-2 cells independently from induction of apoptosis, modulation of CEACAM-6 expression and Lf sub-cellular localization. At our knowledge, this is the first study showing that the sole Lf pre-treatment can activate protective intracellular pathways, reducing LF82 invasiveness, intracellular survival and cell-DNA damages.

Immunomodulation to Prevent or Treat Neonatal Sepsis: Past, Present, and Future

Despite continued advances in neonatal medicine, sepsis remains a leading cause of death worldwide in neonatal intensive care units. The clinical presentation of sepsis in neonates varies markedly from that in older children and adults, and distinct acute inflammatory responses results in age-specific inflammatory and protective immune response to infection. This review first provides an overview of the neonatal immune system, then covers current mainstream, and experimental preventive and adjuvant therapies in neonatal sepsis. We also discuss how the distinct physiology of the perinatal period shapes early life immune responses and review strategies to reduce neonatal sepsis-related morbidity and mortality. A summary of studies that characterize immune ontogeny and neonatal sepsis is presented, followed by discussion of clinical trials assessing interventions such as breast milk, lactoferrin, probiotics, and pentoxifylline. Finally, we critically appraise future treatment options such as stem cell therapy, other antimicrobial protein and peptides, and targeting of pattern recognition receptors in an effort to prevent and/or treat sepsis in this highly vulnerable neonatal population.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

Inhibition of Cronobacter sakazakii Adhesion to Caco-2 Cells by Commercial Dairy Powders and Raw Buttermilk

Cronobacter sakazakii is a foodborne pathogen that has been associated with severe infections, mainly in neonates. The binding of this bacterium to host cell surfaces represents the first step in the pathogenesis of disease. An ELISA-based assay has been developed using a polyclonal antiserum against C. sakazakii to determine its adhesion to Caco-2 cells. The antiserum used recognized many of the outer membrane proteins of C. sakazakii. A positive correlation was found between the absorbance values obtained by ELISA and the number of bacteria adhered to cells determined by plate counting. The inhibitory effect on bacterial adhesion to cells observed with some dairy products was concentration-dependent. Commercial buttermilk caused the maximal reduction of the adhesion percentage (33.0 ± 5.07) at the highest concentration assayed (20 mg/mL), followed by butter serum (31.9 ± 5.36), skim milk (30.4 ± 5.07), and raw buttermilk (25.6 ± 3.80). In some cases, significant differences (p < 0.05) were found in the inhibition exerted by the different products evaluated. The results obtained in this study demonstrate that dairy products contain some components with the ability to inhibit the adhesion of C. sakazakii to Caco-2 cells.

Two outer membrane proteins are bovine lactoferrin-binding proteins in Mannheimia haemolytica A1

Mannheimia haemolytica is a Gram negative bacterium that is part of the bovine respiratory disease, which causes important economic losses in the livestock industry. In the present work, the interaction between M. haemolytica A1 and bovine lactoferrin (BLf) was studied. This iron-chelating glycoprotein is part of the mammalian innate-immune system and is present in milk and mucosal secretions; Lf is also contained in neutrophils secondary granules, which release this glycoprotein at infection sites. It was evidenced that M. haemolytica was not able to use iron-charged BLf (BholoLf) as a sole iron source; nevertheless, iron-lacked BLf (BapoLf) showed a bactericidal effect against M. haemolytica with MIC of 4.88 ± 1.88 and 7.31 ± 1.62 μM for M. haemolytica strain F (field isolate) and M. haemolytica strain R (reference strain), respectively. Through overlay assays and 2-D electrophoresis, two OMP of 32.9 and 34.2 kDa with estimated IP of 8.18 and 9.35, respectively, were observed to bind both BapoLf and BholoLf; these OMP were identified by Maldi-Tof as OmpA (heat-modifiable OMP) and a membrane protein (porin). These M. haemolytica BLf binding proteins could be interacting in vivo with both forms of BLf depending on the iron state of the bovine.

Use of lactoferrin in the newborn: where do we stand?

Sepsis and necrotizing enterocolitis (NEC) cause significant morbidity and mortality in the newborn. Their ill effects persist in spite of appropriate and effective antibiotic therapy. Lactoferrin as an adjunct to antibiotics in the treatment of sepsis or NEC in the newborn may improve the clinical outcomes by enhancing the host defense and modulating the inflammatory response. This review focuses on the various aspects of lactoferrin use in the newborn.

Adhesion of Diarrheagenic Escherichia coli and Inhibition by Glycocompounds Engaged in the Mucosal Innate Immunity

Escherichia coli colonizes the human intestine shortly after birth, with most strains engaging in a commensal relationship. However, some E. coli strains have evolved toward acquiring genetic traits associated with virulence. Currently, five categories of enteroadherent E. coli strains are well-recognized, and are classified in regard to expressed adhesins and the strategy used during the colonization. The high morbidity associated with diarrhea has motivated investigations focusing on E. coli adhesins, as well on factors that inhibit bacterial adherence. Breastfeeding has proved to be the most effective strategy for preventing diarrhea in children. Aside from the immunoglobulin content, glycocompounds and oligosaccharides in breast milk play a critical role in the innate immunity against diarrheagenic E. coli strains. This review summarizes the colonization factors and virulence strategies exploited by diarrheagenic E. coli strains, addressing the inhibitory effects that oligosaccharides and glycocompounds, such as lactoferrin and free secretory components, exert on the adherence and virulence of these strains. This review thus provides an overview of experimental data indicating that human milk glycocompounds are responsible for the universal protective effect of breastfeeding against diarrheagenic E. coli pathotypes.

Neonatal immune adaptation of the gut and its role during infections

The intestinal tract is engaged in a relationship with a dense and complex microbial ecosystem, the microbiota. The establishment of this symbiosis is essential for host physiology, metabolism, and immune homeostasis. Because newborns are essentially sterile, the first exposure to microorganisms and environmental endotoxins during the neonatal period is followed by a crucial sequence of active events leading to immune tolerance and homeostasis. Contact with potent immunostimulatory molecules starts immediately at birth, and the discrimination between commensal bacteria and invading pathogens is essential to avoid an inappropriate immune stimulation and/or host infection. The dysregulation of these tight interactions between host and microbiota can be responsible for important health disorders, including inflammation and sepsis. This review summarizes the molecular events leading to the establishment of postnatal immune tolerance and how pathogens can avoid host immunity and induce neonatal infections and sepsis.

Bovine lactoferrin decreases cholera-toxin-induced intestinal fluid accumulation in mice by ganglioside interaction

Secretory diarrhea caused by cholera toxin (CT) is initiated by binding of CT’s B subunit (CTB) to GM1-ganglioside on the surface of intestinal cells. Lactoferrin, a breast milk glycoprotein, has shown protective effect against several enteropathogens. The aims of this study were to determine the effect of bovine-lactoferrin (bLF) on CT-induced intestinal fluid accumulation in mice, and the interaction between bLF and CT/CTB with the GM1-ganglioside receptor. Fluid accumulation induced by CT was evaluated in the mouse ileal loop model using 56 BALB/c mice, with and without bLF added before, after or at the same time of CT administration. The effect of bLF in the interaction of CT and CTB with GM1-ganglioside was evaluated by a GM1-enzyme-linked immunosorbent assay. bLF decreased CT-induced fluid accumulation in the ileal loop of mice. The greatest effect was when bLF was added before CT (median, 0.066 vs. 0.166 g/cm, with and without bLF respectively, p<0.01). We conclude that bLF decreases binding of CT and CTB to GM1-ganglioside, suggesting that bLF suppresses CT-induced fluid accumulation by blocking the binding of CTB to GM1-ganglioside. bLF may be effective as adjunctive therapy for treatment of cholera diarrhea.

Mini-review: Lactoferrin: a bioinspired, anti-biofilm therapeutic

Medically relevant biofilms have gained a significant level of interest, in part because of the epidemic rise in obesity and an aging population in the developed world. The associated comorbidities of chronic wounds such as pressure ulcers, venous leg ulcers, and diabetic foot wounds remain recalcitrant to the therapies available currently. Development of chronicity in the wound is due primarily to an inability to complete the wound healing process owing to the presence of a bioburden, specifically bacterial biofilms. New therapies are clearly needed which specifically target biofilms. Lactoferrin is a multifaceted molecule of the innate immune system found primarily in milk. While further investigation is warranted to elucidate mechanisms of action, in vitro analyses of lactoferrin and its derivatives have demonstrated that these complex molecules are structurally and functionally well suited to address the heterogeneity of bacterial biofilms. In addition, use of lactoferrin and its derivatives has proven promising in the clinic.

Growth comparison of several Escherichia coli strains exposed to various concentrations of lactoferrin using linear spline regression

Background

We wanted to compare growth differences between 13 Escherichia coli strains exposed to various concentrations of the growth inhibitor lactoferrin in two different types of broth (Syncase and Luria-Bertani (LB)). To carry this out, we present a simple statistical procedure that separates microbial growth curves that are due to natural random perturbations and growth curves that are more likely caused by biological differences.

Bacterial growth was determined using optical density data (OD) recorded for triplicates at 620 nm for 18 hours for each strain. Each resulting growth curve was divided into three equally spaced intervals. We propose a procedure using linear spline regression with two knots to compute the slopes of each interval in the bacterial growth curves. These slopes are subsequently used to estimate a 95% confidence interval based on an appropriate statistical distribution. Slopes outside the confidence interval were considered as significantly different from slopes within. We also demonstrate the use of related, but more advanced methods known collectively as generalized additive models (GAMs) to model growth. In addition to impressive curve fitting capabilities with corresponding confidence intervals, GAM’s allow for the computation of derivatives, i.e. growth rate estimation, with respect to each time point.

Results

The results from our proposed procedure agreed well with the observed data. The results indicated that there were substantial growth differences between the E. coli strains. Most strains exhibited improved growth in the nutrient rich LB broth compared to Syncase. The inhibiting effect of lactoferrin varied between the different strains. The atypical enteropathogenic aEPEC-2 grew, on average, faster in both broths than the other strains tested while the enteroinvasive strains, EIEC-6 and EIEC-7 grew slower. The enterotoxigenic ETEC-5 strain, exhibited exceptional growth in Syncase broth, but slower growth in LB broth.

Conclusions

Our results do not indicate clear growth differences between pathogroups or pathogenic versus non-pathogenic E. coli.

Lactoferrin increases both resistance to Salmonella typhimurium infection and the production of antibodies in mice

Lactoferrin (Lf) is a multifunctional iron-binding glycoprotein with antibacterial and immunomodulatory activities. The antibacterial influence of orally administered bovine Lf (bLf) against murine infection caused by Salmonella typhimurium (S. typhimurium) has scarcely been explored. In the current study, Balb/c mice were treated orally for 7 days with either 5 or 100mg of bovine lactoferrin (bLf). On day 7 of treatment, mice were intragastrically infected with a lethal or sublethal dose of colony forming units (CFU) of S. typhimurium. During treatment with bLf, feces from mice sublethally infected were harvested daily to prepare fecal suspensions, which were serially diluted and plated onto Salmonella Shigella agar to estimate CFU/g of feces. After sacrificing the animals on day 7, 14 or 21 post-infection, samples of intestinal fluid, Peyer's patches (PP), liver and spleen were collected to count the number of CFU by plate dilution. Intestinal secretions were also employed, along with serum samples, to evaluate total IgA, IgG and IgM antibodies, and those against Salmonella surface proteins and bLf by ELISA assay. In lethally infected mice both bLf doses decreased mortality. In sublethally infected mice, both bLf doses decreased bacterial shedding in feces and intestinal fluid, and also reduced bacterial colonization at PP and bacterial translocation in the liver and spleen. Levels of total and those IgG and IgM in serum and IgA in intestinal secretions against Salmonella surface proteins and bLf were enhanced with both doses of bLf. These findings suggest that the effect of bLf against the infection by S. typhimurium in mice may be the result of an antimicrobial activity linked with its modulatory effect on immunocompetent cells (from intestinal and peripheral organs) involved in antibody production.

Effect of lactoferrin on enteric pathogens

Much has been learned in recent years about the mechanisms by which breastfeeding improves child health and survival. However, there has been little progress in using these insights to improve pediatric care. Factors that are important for protecting the breast fed infant might be expected to decrease the adverse effects of weaning on diarrhea, growth, and development. Lactoferrin, an iron-binding protein with multiple physiological functions (anti-microbial, anti-inflammatory, and immunomodulatory), is one of the most important proteins present in mammalian milk. Protection against gastroenteritis is the most likely biologically relevant activity of lactoferrin. Multiple in vitro and animal studies have shown a protective effect of lactoferrin on infections with enteric microorganisms, including rotavirus, Giardia, Shigella, Salmonella and the diarrheagenic Escherichia coli. Lactoferrin has two major effects on enteric pathogens: it inhibits growth and it impairs function of surface expressed virulence factors thereby decreasing their ability to adhere or to invade mammalian cells. Thus, lactoferrin may protect infants from gastrointestinal infection by preventing the attachment by enteropathogens in the gut. Recently several clinical trials in children have started to address this issue. Whether lactoferrin can prevent a significant portion of diarrheal disease remains to be determined.

Effect of lactoferrin on EnteroaggregativeE. coli(EAEC)This paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal’s usual peer review process

We previously demonstrated that lactoferrin inhibits adherence of enteropathogenic Escherichia coli to HEp-2 cells and decreases invasiveness of Shigella flexneri in HeLa cells by disruption of the type III secretory system (TTSS) of both enteropathogens. To determine whether these effects were specific to the TTSS, we assessed the activity of bovine lactoferrin on enteroaggregative E. coli (EAEC), enteropathogens whose virulence is not TTSS dependent. Bovine lactoferrin at a concentration of 1.0 and 0.1 mg/mL inhibited EAEC growth. Saturation with iron reversed the bacteriostatic effect. Lactoferrin under nonbacteriostatic conditions decreased EAEC adherence to HEp-2 cells as evaluated by microscopy and CFUs; this effect was not iron dependent. Lactoferrin inhibited EAEC biofilm formation and increased autoagglutination. Lactoferrin blocks EAEC adherence by inducing release and degradation of aggregative adherence fimbria, a key element of EAEC pathogenesis. We hypothesized that lactoferrin binding to lipid A of lipopolysaccharide disrupts the virulence proteins anchored to the bacterial outermembrane. These data suggest that the effect of lactoferrin on surface proteins is not restricted to organisms having a TTSS.

Immunolocalization of lactoferrin in healthy and inflamed gingival tissues

BACKGROUND

It has been reported that lactoferrin prevents biofilm formation and exerts antimicrobial activity. The aim of the present study was to evaluate the cellular source of lactoferrin in healthy and inflamed gingiva.

METHODS

Lactoferrin synthesis was examined in relation to disease manifestation in biopsies of the marginal gingiva by immunohistochemistry. The expression of lactoferrin in cell cultures was studied by immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Healthy gingiva demonstrated no immunoreactivity to lactoferrin in epithelial and connective tissue cells. In inflamed specimens, lactoferrin staining was related to inflammatory cells. These results were confirmed by cell cultures of keratinocytes that did not show any immunoreactivity against lactoferrin. No mRNA message for lactoferrin was detected by RT-PCR in keratinocytes.

CONCLUSIONS

These data provide evidence that lactoferrin is not synthesized in healthy gingival tissues. Therefore, elevated lactoferrin levels in the crevicular fluid of inflamed tissues originate from invading cells of the inflammatory reaction.

Inv-mediated apoptosis of epithelial cells infected with enteropathogenic Yersinia: A protective effect of lactoferrin

Yersinia spp., Gram-negative bacteria infecting animals and humans, contain plasmid and chromosomal genes coding for different virulence factors, of which outer membrane proteins are the most important. Among these, the inv gene product allows bacterial adherence and penetration of cells exposed at the intestinal lumen surface, and subsequent colonization of lymph nodes. In this research, we have studied the effects of bovine lactoferrin (bLf) on Y. enterocolitica and Y. pseudotuberculosis Inv-mediated interactions with epithelial cells. In particular, we analyzed bLf activity toward adhesion, invasion, and cell death induction by Yersinia spp. and the Escherichia coli HB101 (pRI203) strain (expressing the cloned Yersinia inv gene). Results showed that bLf was ineffective in bacterial adhesivity and invasivity whereas it inhibited apoptosis with a dose-dependent relationship. As epithelial cell apoptosis helps enteropathogenic Yersinia to attack the host and to gain access to the tissue, our results demonstrate a new potential antimicrobial application for bLf.

Intestinal adherent bacteria and bacterial translocation in breast-fed and formula-fed rats in relation to susceptibility to infection

The barrier function of the intestinal mucosa is immature in the newborn mammal, and is strengthened by breast milk. We investigated this effect of breast milk by comparing the susceptibility to infection assessed in terms of adherent bacterial colonization of the intestinal tissue (AdC) and bacterial translocation (BT) between breast-fed and formula-fed newborn rats. Three-day-old rat pups were assigned to one of three groups: mother-reared (MR), pseudo-cannulated (sham), and artificially reared (AR). AR rats were infused with formula through an intragastric cannula, under the control of a computer-regulated pumping machine. MR and sham rat pups were reared with their respective dams and received breast milk until weaning in a specially designed cage. In 10-d-old rats, there was no significant difference in the fecal or cecal flora between the AR and MR groups, whereas the AdC and the BT to the liver were greater in the AR than MR group. Enterobacteriaceae, Streptococcus and/or Enterococcus, and Staphylococcus were dominantly detected as microorganisms in AdC flora and BT. The AdC flora did not directly reflect the bacterial colonization flora. These findings suggest that AR rat pups mature normally, although there is a greater colonization of Enterobacteriaceae and BT in AR than MR pups. Consequently, the intestinal barrier function of the pups reared by artificial feeding may become susceptible to BT, and AdC may be more indicative than bacterial colonization of the susceptibility to BT.

Lactoferrin protects rabbits from Shigella flexneri-induced inflammatory enteritis

Shigella species cause bacillary dysentery in humans by invasion, intracellular multiplication, spread to adjacent cells, and induction of brisk inflammatory responses in the intestinal epithelium. In vitro data suggest that lactoferrin, a glycoprotein present in human mucosal secretions, has a role in protection from bacterial enteric infections. We sought to determine the activity of lactoferrin in vivo, using the concentration present in human colostrum, to investigate its effect on the development of clinical and pathological evidence of inflammation in a rabbit model of enteritis. Lactoferrin protected rabbits infected with Shigella flexneri from developing inflammatory intestinal disease. Typical histological changes in ill animals included villous blunting with sloughing of epithelial cells, submucosal edema, infiltration of leukocytes, venous congestion, and hemorrhage. Lactoferrin at a concentration normally found in human colostrum blocks development of S. flexneri-induced inflammatory enteritis.

Bovine colostrum in oral treatment of enterogenic endotoxaemia in rats

INTRODUCTION

Under conditions of shock, bacteria and endotoxins in the intestines can traverse the mucosal barrier by translocation and enter the blood and lymphatic system. Immunoglobulins and lactoferrin have been reported to neutralize endotoxins and bacteria. We studied the essential therapeutic factors of colostrum products in an animal experiment.

METHOD

We simulated endotoxaemia by per-oral administration of a suspension of Escherichia coli and antibiotics into the duodenum of anaesthetized rats after giving intraperitoneal carrageenan. At the same time, pure bovine colostrum or lactoferrin-enriched bovine colostrum was given. Therapeutic effects were studied by examining plasma endotoxin activity and bacterial contamination of mesenterial lymph nodes and peritoneal lavages. Albumin was used in a control group.

RESULTS

The most effective bovine colostrum was able to reduce the maximum plasma endotoxin value by 67% as compared with the albumin group. The combination of this colostrum with lactoferrin brought about a reduction by 80%. The reduction in bacterial contamination of lymph nodes and peritoneal lavages was also evident.

CONCLUSION

Both gammaglobulin and lactoferrin may help to eliminate endotoxins when bovine colostrum is administered into the gut in conditions of septic shock.

Inhibitory effect of bovine milk lactoferrin on the interaction between a streptococcal surface protein antigen and human salivary agglutinin

Human whole saliva induces aggregation of Streptococcus mutans cells via an interaction between a surface protein antigen (PAc) of the organism and salivary agglutinin. Bovine milk inhibits the saliva-induced aggregation of S. mutans. In this study, the milk component that possesses inhibitory activity against this aggregation was isolated and found to be lactoferrin. Surface plasmon resonance analysis indicated that bovine lactoferrin binds more strongly to salivary agglutinin, especially to high molecular mass glycoprotein, which is a component of the agglutinin, than to recombinant PAc. The binding of bovine lactoferrin to salivary agglutinin was thermostable, and the optimal pH for binding was 4.0. To identify the saliva-binding region of bovine lactoferrin, 11 truncated bovine lactoferrin fragments were constructed. A fragment corresponding to the C-terminal half of the lactoferrin molecule had a strong inhibitory effect on the saliva-induced aggregation of S. mutans, whereas a fragment corresponding to the N-terminal half had a weak inhibitory effect. Seven shorter fragments corresponding to lactoferrin residues 473-538 also showed a high ability to inhibit the aggregation of S. mutans. These results suggest that residues 473-538 of bovine lactoferrin are important in the inhibition of saliva-induced aggregation of S. mutans.