Impact of lactoferrin supplementation on growth and prevalence of Giardia colonization in children

Effect of bovine lactoferrin in a therapeutic hamster model of hepatic amoebiasis

Entamoeba histolytica is the causative agent of amoebiasis, a disease that produces dysentery as a result of the perforation of the large intestine. This parasite often invades other organs, primarily the liver, leading to an amoebic liver abscess (ALA), which can cause death. Metronidazole is the drug of choice for the treatment of ALA; however, it produces toxic side effects in patients. Lactoferrin (Lf) is a glycoprotein of the innate immune response that sequesters iron in the mucosae. Lf possesses immune-regulatory properties, such as antiinflammatory and antioxidant activities. Moreover, the microbicidal activity of apoLf, which lacks bound iron, has been shown. In this study, we evaluated the therapeutic effect of bovine Lf (bLf) against ALA in a model of hepatic amoebiasis in hamsters. Interestingly, hamsters treated intragastrically with Lf (2.5 mg/100 g mass) over a period of 8 days showed no clinical signs of disease and ALA was effectively decreased, with only 0.63% detectable lesion, compared with 63% in untreated animals. Furthermore, liver function and blood cells approached normal levels among those receiving bLf treatment. These results suggest that bLf may aid in the therapy of amoebiasis, likely without producing undesirable effects in patients.

Protection against diarrhea associated with Giardia intestinalis Is lost with multi-nutrient supplementation: a study in Tanzanian children

BACKGROUND

Asymptomatic carriage of Giardia intestinalis is highly prevalent among children in developing countries, and evidence regarding its role as a diarrhea-causing agent in these settings is controversial. Impaired linear growth and cognition have been associated with giardiasis, presumably mediated by malabsorption of nutrients. In a prospective cohort study, we aim to compare diarrhea rates in pre-school children with and without Giardia infection. Because the study was conducted in the context of an intervention trial assessing the effects of multi-nutrients on morbidity, we also assessed how supplementation influenced the relationship between Giardia and diarrhoea rates, and to what extent Giardia modifies the intervention effect on nutritional status.

METHODS AND FINDINGS

Data were collected in the context of a randomized placebo-controlled efficacy trial with 2×2 factorial design assessing the effects of zinc and/or multi-micronutrients on morbidity (n=612; height-for-age z-score <-1.5 SD). Outcomes measures were episodes of diarrhea (any reported, or with ≥3 stools in the last 24 h) and fever without localizing signs, as detected with health-facility based surveillance. Giardia was detected in stool by enzyme-linked immunosorbent assay. Among children who did not receive multi-nutrients, asymptomatic Giardia infection at baseline was associated with a substantial reduction in the rate of diarrhea (HR 0.32; 0.15-0.66) and fever without localizing signs (HR 0.56; 0.36-0.87), whereas no such effect was observed among children who received multi-nutrients (p-values for interaction 0.03 for both outcomes). This interaction was independent of age, HAZ-scores and distance to the research dispensary. There was no evidence that Giardia modified the intervention effect on nutritional status.

CONCLUSION

Although causality of the Giardia-associated reduction in morbidity cannot be established, multi-nutrient supplementation results in a loss of this protection and thus seems to influence the proliferation or virulence of Giardia or associated intestinal pathogens.

Protection against diarrhea associated with Giardia intestinalis Is lost with multi-nutrient supplementation: a study in Tanzanian children

Background

Asymptomatic carriage of Giardia intestinalis is highly prevalent among children in developing countries, and evidence regarding its role as a diarrhea-causing agent in these settings is controversial. Impaired linear growth and cognition have been associated with giardiasis, presumably mediated by malabsorption of nutrients. In a prospective cohort study, we aim to compare diarrhea rates in pre-school children with and without Giardia infection. Because the study was conducted in the context of an intervention trial assessing the effects of multi-nutrients on morbidity, we also assessed how supplementation influenced the relationship between Giardia and diarrhoea rates, and to what extent Giardia modifies the intervention effect on nutritional status.

Methods and Findings

Data were collected in the context of a randomized placebo-controlled efficacy trial with 2×2 factorial design assessing the effects of zinc and/or multi-micronutrients on morbidity (n = 612; height-for-age z-score <−1.5 SD). Outcomes measures were episodes of diarrhea (any reported, or with ≥3 stools in the last 24 h) and fever without localizing signs, as detected with health-facility based surveillance. Giardia was detected in stool by enzyme-linked immunosorbent assay. Among children who did not receive multi-nutrients, asymptomatic Giardia infection at baseline was associated with a substantial reduction in the rate of diarrhea (HR 0.32; 0.15–0.66) and fever without localizing signs (HR 0.56; 0.36–0.87), whereas no such effect was observed among children who received multi-nutrients (p-values for interaction 0.03 for both outcomes). This interaction was independent of age, HAZ-scores and distance to the research dispensary. There was no evidence that Giardia modified the intervention effect on nutritional status.

Conclusion

Although causality of the Giardia-associated reduction in morbidity cannot be established, multi-nutrient supplementation results in a loss of this protection and thus seems to influence the proliferation or virulence of Giardia or associated intestinal pathogens.

Giardia intestinalis is a well-known cause of diarrhea in industrialized countries. In children in developing countries, asymptomatic infections are common and their role as cause of diarrhea has been questioned. In a cohort of rural Tanzanian pre-school children, we assessed the association between the presence of Giardia at baseline and subsequent diarrhea risk. The study was conducted in the context of a randomised trial assessing the effect of supplementation with zinc and other micro-nutrients on malaria, and half of the children daily received a multi-nutrient supplement. Surprisingly, we found that the presence of Giardia at baseline was associated with a substantial reduction in diarrhea risk. Multivariate statistical analysis showed that this protection could not be explained by differences in age or walking distance to the dispensary between children with and without Giardia. Because we cannot exclude that children differed in other (unmeasured) characteristics, we cannot draw firm conclusions about the causality of the observed association, but our findings support the view that the parasite is not an important cause of diarrhea in highly endemic settings. Striking was that the Giardia-associated protection was lost when children received multi-nutrients. Our data do not provide information about the mechanisms involved, but suggest that multi-nutrients may influence the compositionor pathogenicity of intestinal biota.

Lactoferrin and prevention of late-onset sepsis in the pre-term neonates

Late-onset sepsis (LOS) affects a large proportion of pre-term neonates in neonatal intensive care units (NICUs) worldwide, with high morbidity and related mortality, and frequent occurrence of severe late neurodevelopmental impairment. Due to the frequency, severity and difficulties in early diagnosis and prompt therapy, prevention is crucial for decreasing the burden of infection-related complications in NICUs. It is well known that feeding with fresh maternal milk, hygiene measures and the cautious use of H2-blockers are related with a decreased risk of developing sepsis. However, evidence from randomised clinical trials exists only for fluconazole in the prevention of fungal infections in the NICU. Lactoferrin is the main whey protein in mammalian milk, and is involved in innate immune host defences. Notably, human lactoferrin can be found at increased concentrations in colostrum and in milk from mothers of premature neonates. Human (hLF) and bovine lactoferrin (bLF) share a high (77%) amino-acid homology, and the same N-terminal peptide responsible for antimicrobial activity, called lactoferricin. In vitro, bLF shows potent direct antimicrobial activity against all types of pathogens, which occurs via anti-cell wall actions and leads to disintegration of the micro-organism's membranes. bLF is also synergistic with many antimicrobials and antifungals, and promotes growth and differentiation of the immature gut. Based on this background data, a randomised clinical trial was recently conducted in very low birth weight pre-term neonates given bLF alone or with the probiotic Lactobacillus GG. The aim of the trial was to assess the ability of bLF to prevent late-onset sepsis of any origin in the studied infants during their stay in the NICU. This article discusses the preliminary data from this study, along with the proposed mechanisms of action of bLF in pre-term infants.

Bioactive proteins in human milk: mechanisms of action

Human milk contains a multitude of bioactive proteins, with very diverse functions. Some of these proteins are involved in the synthesis and expression of milk, but the majority appears to have evolved to provide physiological activities in the breast-fed infant. These activities are exerted by a wide variety of mechanisms and have largely been unraveled by in vitro studies. To be active in the gastrointestinal tract, these proteins must be able to resist proteolytic degradation, at least for some time. We have evaluated the human milk proteins lactoferrin, haptocorrin, alpha(1)-antitrypsin, and transforming growth factor -beta in an in vitro digestion model, mimicking the conditions of the infant gastrointestinal milieu. These bioactive proteins are resistant against proteolysis and can remain intact or as larger fragments through passage of the gastrointestinal tract. In vitro digestibility assays can be helpful to assess which human milk proteins can resist proteolysis and to what extent.

Use and endocytosis of iron-containing proteins by Entamoeba histolytica trophozoites

Iron is essential for nearly all organisms; in mammals, it is part of proteins such as haemoglobin, and it is captured by transferrin and lactoferrin. Transferrin is present in serum, and lactoferrin is secreted by the mucosa and by neutrophils at infection sites, as a host iron-withholding response, sequestering iron away from invading microorganisms. Additionally, all cells contain ferritin, which sequesters iron when its intracellular levels are increased, detoxifying and preventing damage. Liver ferritin contains 50% of iron corporal reserves. During evolution, pathogens have evolved diverse strategies to obtain iron from their hosts in order to survive. The protozoan Entamoeba histolytica invades the intestinal mucosa, causing dysentery, and the trophozoites often travel to the liver producing hepatic abscesses; thus, intestine and liver proteins could be important iron supplies for E. histolytica. We found that E. histolytica trophozoites can grow in both ferrous and ferric iron, and that they can use haemoglobin, holo-transferrin, holo-lactoferrin, and ferritin as in vitro iron sources. These proteins supported the amoeba growth throughout consecutive passages, similarly to ferric citrate. By confocal microscopy and immunoblotting, iron-binding proteins were observed specifically bound to the amoeba surface, and they were endocytosed, trafficked through the endosomal/lysosomal route, and degraded by neutral and acidic cysteine-proteases. Transferrin and ferritin were mainly internalized through clathrin-coated vesicles, and holo-lactoferrin was mainly internalized by caveola-like structures. In contrast, apo-lactoferrin bound to membrane lipids and cholesterol, inducing cell death. The results suggest that in vivo trophozoites secrete products that can destroy enterocytes, erythrocytes, and hepatocytes, releasing transferrin, haemoglobin, ferritin, and other iron-containing proteins, which, together with lactoferrin derived from neutrophils and acinar cells, could be used as abundant iron supplies by amoebas.

Nutritional roles of lactoferrin

PURPOSE OF REVIEW

Until relatively recently, the only significant source of lactoferrin in the diet was human lactoferrin, provided in breast milk. Today, however, bovine lactoferrin, isolated by dairy technology, as well as recombinant human lactoferrin are commercially available and can be added to foods and clinical products with perceived benefits to the consumer. In this review, the potential biological functions of dietary lactoferrin are described and critically examined.

RECENT FINDINGS

Ingested lactoferrin has been suggested to exert antibacterial and antiviral activities in the intestine, in part through a direct effect on pathogens, but possibly also affecting mucosal immune function. The latter function is most likely mediated by lactoferrin being taken up by cells via a unique receptor-mediated pathway and affecting gene transcription. Lactoferrin has also been shown to enhance iron status of infants and pregnant women, possibly also via the receptor-mediated pathway. In addition, lactoferrin can stimulate intestinal cell proliferation and differentiation, causing expansion of tissue mass and absorptive capacity. On the contrary, lactoferrin has been shown to inhibit carcinogenesis. Recent findings also suggest that oral lactoferrin treatment may have an anti-inflammatory effect on pregnant women, reducing pregnancy complications.

SUMMARY

Lactoferrin treatment may have beneficial preventive and therapeutic effects on infection, inflammation, and cancer as well as enhancing iron status and growth in vulnerable groups.

Travelers' diarrhea: an update on susceptibility, prevention, and treatment

Traditional risk factors do not explain the individual differences in susceptibility to travelers' diarrhea (TD) among the increasing number of travelers to the developing world. Single-nucleotide polymorphisms of the genes encoding for lactoferrin and interleukin 8 (IL-8) have been linked to susceptibility to TD. Subjects with mutations of the FUT2 gene are immune to norovirus infection. The recognition of individual variations in susceptibility to TD will aid in risk stratification of travelers to the developing world. Diagnosis is usually syndromic, but improved diagnostic methods are in development. Quinolones have been the mainstay of antibiotic treatment, but azithromycin (for resistant organisms) and rifaximin (for noninvasive organisms) may provide advantages. Transcutaneous vaccines for the major Escherichia coli enteropathogens are in development. In the future, travel advice, prophylactic medication regimens, and standby treatment for TD will be better tailored to each patient's specific risk factors.

Update on human infections caused by intestinal protozoa

PURPOSE OF REVIEW

To update the reader on the recent literature discussing human infections due to intestinal protozoa.

RECENT FINDINGS

Diarrheal diseases due to intestinal protozoa cause significant morbidity and mortality worldwide in a variety of patient populations. New literature on key pathogens Cryptosporidium, Cyclospora, Isospora, Giardia, and Entamoeba histolytica are discussed.

SUMMARY

The recent medical literature on these pathogens has focused on new advances in understanding human genetic markers associated with susceptibility to infection and the use of molecular diagnostic techniques for both outbreak investigations (molecular epidemiology) and to understand the variability of clinical disease within species and subspecies.

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.