Parasiticidal effect of synthetic bovine lactoferrin peptides on the enteric parasite Giardia intestinalis

Therapeutic potential of antimicrobial peptides against pathogenic protozoa

Protozoal infections cause significant morbidity and mortality in humans and animals. The use of several antiprotozoal drugs is associated with serious adverse effects and resistance development, and drugs that are more effective are urgently needed. Microorganisms, mammalian cells and fluids, insects, and reptiles are sources of antimicrobial peptides (AMPs) that act against pathogenic microorganisms; these AMPs have been widely studied as a promising alternative therapeutic option to conventional antibiotics, aiming to treat infections caused by multidrug-resistant pathogens. One advantage of AMP molecules is their adaptability, as they can be easily fine-tuned for broad-spectrum or targeted activity by changing the amino acid residues in their sequence. Consequently, these variations in structural and physicochemical properties can alter the antimicrobial activities of AMPs and decrease resistance development. This article presents an overview of peptide activities against amebiasis, giardiasis, trichomoniasis, Chagas disease, leishmaniasis, malaria, and toxoplasmosis. AMPs and their analogs demonstrate great potential as therapeutics, with potent and selective activity, when compared with commercially available drugs, and hold the potential to act as new scaffolds for the development of novel anti-protozoal drugs.

Production of Bioactive Porcine Lactoferrin through a Novel Glucose-Inducible Expression System in Pichia pastoris: Unveiling Antimicrobial and Anticancer Functionalities

Lactoferrin (LF) stands as one of the extensively investigated iron-binding glycoproteins within milk, exhibiting diverse biological functionalities. The global demand for LF has experienced consistent growth. Biotechnological strategies aimed at enhancing LF productivity through microbial expression systems offer substantial cost-effective advantages and exhibit fewer constraints compared to traditional animal bioreactor technologies. This study devised a novel recombinant plasmid, wherein the AOX1 promoter was replaced with a glucose-inducible G1 promoter (PG1) to govern the expression of recombinant porcine LF (rpLF) in Pichia pastoris GS115. High-copy-number PG1-rpLF yeast clones were meticulously selected, and subsequent induction with 0.05 g/L glucose demonstrated robust secretion of rpLF. Scaling up production transpired in a 5 L fermenter, yielding an estimated rpLF productivity of approximately 2.8 g/L by the conclusion of glycerol-fed fermentation. A three-step purification process involving tangential-flow ultrafiltration yielded approximately 6.55 g of rpLF crude (approximately 85% purity). Notably, exceptional purity of rpLF was achieved through sequential heparin and size-exclusion column purification. Comparatively, the present glucose-inducible system outperformed our previous methanol-induced system, which yielded a level of 87 mg/L of extracellular rpLF secretion. Furthermore, yeast-produced rpLF demonstrated affinity for ferric ions (Fe3+) and exhibited growth inhibition against various pathogenic microbes (E. coli, S. aureus, and C. albicans) and human cancer cells (A549, MDA-MB-231, and Hep3B), similar to commercial bovine LF (bLF). Intriguingly, the hydrolysate of rpLF (rpLFH) manifested heightened antimicrobial and anticancer effects compared to its intact form. In conclusion, this study presents an efficient glucose-inducible yeast expression system for large-scale production and purification of active rpLF protein with the potential for veterinary or medical applications.

Repurposing Terfenadine as a Novel Antigiardial Compound

Giardia lamblia is a highly infectious protozoan that causes giardiasis, a gastrointestinal disease with short-term and long-lasting symptoms. The currently available drugs for giardiasis treatment have limitations such as side effects and drug resistance, requiring the search for new antigiardial compounds. Drug repurposing has emerged as a promising strategy to expedite the drug development process. In this study, we evaluated the cytotoxic effect of terfenadine on Giardia lamblia trophozoites. Our results showed that terfenadine inhibited the growth and cell viability of Giardia trophozoites in a time-dose-dependent manner. In addition, using scanning electron microscopy, we identified morphological damage; interestingly, an increased number of protrusions on membranes and tubulin dysregulation with concomitant dysregulation of Giardia GiK were observed. Importantly, terfenadine showed low toxicity for Caco-2 cells, a human intestinal cell line. These findings highlight the potential of terfenadine as a repurposed drug for the treatment of giardiasis and warrant further investigation to elucidate its precise mechanism of action and evaluate its efficacy in future research.

Time to Kill and Time to Heal: The Multifaceted Role of Lactoferrin and Lactoferricin in Host Defense

Lactoferrin is an iron-binding glycoprotein present in most human exocrine fluids, particularly breast milk. Lactoferrin is also released from neutrophil granules, and its concentration increases rapidly at the site of inflammation. Immune cells of both the innate and the adaptive immune system express receptors for lactoferrin to modulate their functions in response to it. On the basis of these interactions, lactoferrin plays many roles in host defense, ranging from augmenting or calming inflammatory pathways to direct killing of pathogens. Complex biological activities of lactoferrin are determined by its ability to sequester iron and by its highly basic N-terminus, via which lactoferrin binds to a plethora of negatively charged surfaces of microorganisms and viruses, as well as to mammalian cells, both normal and cancerous. Proteolytic cleavage of lactoferrin in the digestive tract generates smaller peptides, such as N-terminally derived lactoferricin. Lactoferricin shares some of the properties of lactoferrin, but also exhibits unique characteristics and functions. In this review, we discuss the structure, functions, and potential therapeutic uses of lactoferrin, lactoferricin, and other lactoferrin-derived bioactive peptides in treating various infections and inflammatory conditions. Furthermore, we summarize clinical trials examining the effect of lactoferrin supplementation in disease treatment, with a special focus on its potential use in treating COVID-19.

Stem-Loop Structures in Iron-Regulated mRNAs of Giardia duodenalis

Giardia duodenalis is a significant cause of waterborne and foodborne infections, day-care center outbreaks, and traveler's diarrhea worldwide. In protozoa such as Trichomonas vaginalis and Entamoeba histolytica, iron affects the growth, pathogenicity mechanisms, and expression of virulence genes. One of the proposed iron regulatory mechanisms is at the post-transcriptional level through an IRE/IRP-like (iron responsive element/iron regulatory protein) system. Recently, the expression of many putative giardial virulence factors in the free-iron levels has been reported in subsequent RNAseq experiments; however, the iron regulatory mechanism remains unknown. Thus, this work aimed to determine the effects of iron on the growth, gene expression, and presence of IRE-like structures in G. duodenalis. First, the parasite's growth kinetics at different iron concentrations were studied, and the cell viability was determined. It was observed that the parasite can adapt to an iron range from 7.7 to 500 µM; however, in conditions without iron, it is unable to survive in the culture medium. Additionally, the iron modulation of three genes was determined by RT-PCR assays. The results suggested that Actin, glucosamine-6-phosphate deaminase, and cytochrome b5 mRNA were down-regulated by iron. To investigate the presence of IRE-like structures, in silico analyses were performed for different mRNAs from the Giardia genome database. The Zuker mfold v2.4 web server and theoretical analysis were used to predict the secondary structures of the 91 mRNAs analyzed. Interestingly, the iron-induced downregulation of the genes analyzed corresponds to the location of the stem-loop structures found in their UTR regions. In conclusion, iron modulates the growth and expression of specific genes, likely due to the presence of IRE-like structures in G. duodenalis mRNAs.

Human Milk Microbiome and Microbiome-Related Products: Potential Modulators of Infant Growth

Infant growth trajectory may influence later-life obesity. Human milk provides a wide range of nutritional and bioactive components that are vital for infant growth. Compared to formula-fed infants, breastfed infants are less likely to develop later-onset obesity, highlighting the potential role of bioactive components present in human milk. Components of particular interest are the human milk microbiota, human milk oligosaccharides (HMOs), short-chain fatty acids (SCFAs), and antimicrobial proteins, each of which influence the infant gut microbiome, which in turn has been associated with infant body composition. SCFAs and antimicrobial proteins from human milk may also systemically influence infant metabolism. Although inconsistent, multiple studies have reported associations between HMOs and infant growth, while studies on other bioactive components in relation to infant growth are sparse. Moreover, these microbiome-related components may interact with each other within the mammary gland. Here, we review the evidence around the impact of human milk microbes, HMOs, SCFAs, and antimicrobial proteins on infant growth. Breastfeeding is a unique window of opportunity to promote optimal infant growth, with aberrant growth trajectories potentially creating short- and long-term public health burdens. Therefore, it is important to understand how bioactive components of human milk influence infant growth.

Activity of Apo-Lactoferrin on Pathogenic Protozoa

Parasites and other eventually pathogenic organisms require the ability to adapt to different environmental conditions inside the host to assure survival. Some host proteins have evolved as defense constituents, such as lactoferrin (Lf), which is part of the innate immune system. Lf in its iron-free form (apo-Lf) and its peptides obtained by cleavage with pepsin are microbicides. Parasites confront Lf in mucosae and blood. In this work, the activity of Lf against pathogenic and opportunistic parasites such as Cryptosporidium spp., Eimeria spp., Entamoeba histolytica, Giardia duodenalis, Leishmania spp., Trypanosoma spp., Plasmodium spp., Babesia spp., Toxoplasma gondii, Trichomonas spp., and the free-living but opportunistic pathogens Naegleria fowleri and Acanthamoeba castellani were reviewed. The major effects of Lf could be the inhibition produced by sequestering the iron needed for their survival and the production of oxygen-free radicals to more complicated mechanisms, such as the activation of macrophages to phagocytes with the posterior death of those parasites. Due to the great interest in Lf in the fight against pathogens, it is necessary to understand the exact mechanisms used by this protein to affect their virulence factors and to kill them.

Lactoferrin as a Human Genome “Guardian”—An Overall Point of View

Structural abnormalities causing DNA modifications of the ethene and propanoadducts can lead to mutations and permanent damage to human genetic material. Such changes may cause premature aging and cell degeneration and death as well as severe impairment of tissue and organ function. This may lead to the development of various diseases, including cancer. In response to a damage, cells have developed defense mechanisms aimed at preventing disease and repairing damaged genetic material or diverting it into apoptosis. All of the mechanisms described above are part of the repertoire of action of Lactoferrin—an endogenous protein that contains iron in its structure, which gives it numerous antibacterial, antiviral, antifungal and anticancer properties. The aim of the article is to synthetically present the new and innovative role of lactoferrin in the protection of human genetic material against internal and external damage, described by the modulation mechanisms of the cell cycle at all its levels and the mechanisms of its repair.

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.

LFchimera: a synthetic mimic of the two antimicrobial domains of bovine lactoferrin

Saliva is essential for the maintenance of oral health. When salivary flow is impaired, the risk of various oral diseases such as caries and candidiasis increases drastically. Under healthy conditions, saliva provides effective protection against microbial colonization by the collaborative action of numerous host-defense molecules. This review describes how saliva has been the guideline for the design and characterization of a heterodimeric antimicrobial construct called LFchimera. This construct mimics the helical parts of two antimicrobial domains in the crystal structure of bovine lactoferrin. It shows high antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and parasites including biowarfare agents such as Bacillus anthracis, Burkholderia pseudomallei, and Yersinia pestis. Further, sublethal concentrations of LFchimera inhibited biofilm formation, the invasiveness of HeLa cells by Yersinia spp., and prevented haemolysis of enteropathogenic Escherichia coli, demonstrating the versatility of these peptides.

Lactoferrin and Its Derived Peptides: An Alternative for Combating Virulence Mechanisms Developed by Pathogens

Due to the emergence of multidrug-resistant pathogens, it is necessary to develop options to fight infections caused by these agents. Lactoferrin (Lf) is a cationic nonheme multifunctional glycoprotein of the innate immune system of mammals that provides numerous benefits. Lf is bacteriostatic and/or bactericidal, can stimulate cell proliferation and differentiation, facilitate iron absorption, improve neural development and cognition, promote bone growth, prevent cancer and exert anti-inflammatory and immunoregulatory effects. Lactoferrin is present in colostrum and milk and is also produced by the secondary granules of polymorphonuclear leukocytes, which store this glycoprotein and release it at sites of infection. Lf is also present in many fluids and exocrine secretions, on the surfaces of the digestive, respiratory and reproductive systems that are commonly exposed to pathogens. Apo-Lf (an iron-free molecule) can be microbiostatic due to its ability to capture ferric iron, blocking the availability of host iron to pathogens. However, apo-Lf is mostly microbicidal via its interaction with the microbial surface, causing membrane damage and altering its permeability function. Lf can inhibit viral entry by binding to cell receptors or viral particles. Lf is also able to counter different important mechanisms evolved by microbial pathogens to infect and invade the host, such as adherence, colonization, invasion, production of biofilms and production of virulence factors such as proteases and toxins. Lf can also cause mitochondrial and caspase-dependent regulated cell death and apoptosis-like in pathogenic yeasts. All of these mechanisms are important targets for treatment with Lf. Holo-Lf (the iron-saturated molecule) can contain up to two ferric ions and can also be microbicidal against some pathogens. On the other hand, lactoferricins (Lfcins) are peptides derived from the N-terminus of Lf that are produced by proteolysis with pepsin under acidic conditions, and they cause similar effects on pathogens to those caused by the parental Lf. Synthetic analog peptides comprising the N-terminus Lf region similarly exhibit potent antimicrobial properties. Importantly, there are no reported pathogens that are resistant to Lf and Lfcins; in addition, Lf and Lfcins have shown a synergistic effect with antimicrobial and antiviral drugs. Due to the Lf properties being microbiostatic, microbicidal, anti-inflammatory and an immune modulator, it represents an excellent natural alternative either alone or as adjuvant in the combat to antibiotic multidrug-resistant bacteria and other pathogens. This review aimed to evaluate the data that appeared in the literature about the effects of Lf and its derived peptides on pathogenic bacteria, protozoa, fungi and viruses and how Lf and Lfcins inhibit the mechanisms developed by these pathogens to cause disease.

Iron in infection and immunity

Iron is an essential micronutrient for virtually all living cells. In infectious diseases, both invading pathogens and mammalian cells including those of the immune system require iron to sustain their function, metabolism and proliferation. On the one hand, microbial iron uptake is linked to the virulence of most human pathogens. On the other hand, the sequestration of iron from bacteria and other microorganisms is an efficient strategy of host defense in line with the principles of 'nutritional immunity'. In an acute infection, host-driven iron withdrawal inhibits the growth of pathogens. Chronic immune activation due to persistent infection, autoimmune disease or malignancy however, sequesters iron not only from infectious agents, autoreactive lymphocytes and neoplastic cells but also from erythroid progenitors. This is one of the key mechanisms which collectively result in the anemia of chronic inflammation. In this review, we highlight the most important interconnections between iron metabolism and immunity, focusing on host defense against relevant infections and on the clinical consequences of anemia of inflammation.

A Novel Anti-Microbial Peptide from Pseudomonas, REDLK Induced Growth Inhibition of Leishmania tarentolae Promastigote In Vitro

Leishmaniasis is a prevalent cause of death and animal morbidity in underdeveloped countries of endemic area. However, there is few vaccine and effective drugs. Antimicrobial peptides are involved in the innate immune response in many organisms and are being developed as novel drugs against parasitic infections. In the present study, we synthesized a 5-amino acid peptide REDLK, which mutated the C-terminus of Pseudomonas exotoxin, to identify its effect on the Leishmania tarentolae. Promastigotes were incubated with different concentration of REDLK peptide, and the viability of parasite was assessed using MTT and Trypan blue dye. Morphologic damage of Leishmania was analyzed by light and electron microscopy. Cellular apoptosis was observed using the annexin V-FITC/PI apoptosis detection kit, mitochondrial membrane potential assay kit and flow cytometry. Our results showed that Leishmania tarentolae was susceptible to REDLK in a dose-dependent manner, disrupt the surface membrane integrity and caused parasite apoptosis. In our study, we demonstrated the leishmanicidal activity of an antimicrobial peptide REDLK from Pseudomonas aeruginosa against Leishmania tarentolae in vitro and present a foundation for further research of anti-leishmanial drugs.

Drug resistance in Giardia: Mechanisms and alternative treatments for Giardiasis

The use of chemotherapeutic drugs is the main resource against clinical giardiasis due to the lack of approved vaccines. Resistance of G. duodenalis to the most used drugs to treat giardiasis, metronidazole and albendazole, is a clinical issue of growing concern and yet unknown impact, respectively. In the search of new drugs, the completion of the Giardia genome project and the use of biochemical, molecular and bioinformatics tools allowed the identification of ligands/inhibitors for about one tenth of ≈150 potential drug targets in this parasite. Further, the synthesis of second generation nitroimidazoles and benzimidazoles along with high-throughput technologies have allowed not only to define overall mechanisms of resistance to metronidazole but to screen libraries of repurposed drugs and new pharmacophores, thereby increasing the known arsenal of anti-giardial compounds to some hundreds, with most demonstrating activity against metronidazole or albendazole-resistant Giardia. In particular, cysteine-modifying agents which include omeprazole, disulfiram, allicin and auranofin outstand due to their pleiotropic activity based on the extensive repertoire of thiol-containing proteins and the microaerophilic metabolism of this parasite. Other promising agents derived from higher organisms including phytochemicals, lactoferrin and propolis as well as probiotic bacteria/fungi have also demonstrated significant potential for therapeutic and prophylactic purposes in giardiasis. In this context the present chapter offers a comprehensive review of the current knowledge, including commonly prescribed drugs, causes of therapeutic failures, drug resistance mechanisms, strategies for the discovery of new agents and alternative drug therapies.

In vitro leishmanicidal activity of antimicrobial peptide KDEL against Leishmania tarentolae

Leishmaniasis, caused by the intracellular protozoan parasite Leishmania, remains an important neglected tropical infectious disease. Infection may be lethal if untreated. Currently, the available drugs for the disease are limited by high toxicity and drug resistance. There is an urgent need to develop novel anti-leishmanial strategies. Antimicrobial peptides (AMPs) have been described as the first-line immune defense against pathogenic microbes and are being developed as emerging anti-parasitic therapies. In the present study, we showed the anti-leishmanial activity of the synthetic 4-amino acid peptide lysine, aspartic acid, glutamic acid, and leucine (KDEL), the endoplasmic reticulum retention sequence, against Leishmania tarentolae promastigote and amastigote. Different concentrations of KDEL peptides were incubated with promastigotes, MTT viability assay, and promastigote assay were carried out. Macrophages infected with GFP-transfected L. tarentolae promastigotes were incubated with KDEL peptides, and the anti-amastigote activity of the KDEL peptides was measured by fluorescence microscopy. The damage of L. tarentolae was observed by light microscopy and electron microscopy. The cell apoptosis was analyzed using the Annexin V-FITC/PI apoptosis detection kit and mitochondrial membrane potential assay kit and by flow cytometry. Results showed that L. tarentolae was susceptible to KDEL peptides in a dose-dependent manner, and KDEL peptides disrupted the surface membrane integrity and caused cell apoptosis. In our study, we found for the first time an AMP KDEL from Pseudomonas aeruginosa and proved its significant therapeutic potential as a novel anti-leishmanial drug.

Synthetic bovine lactoferrin peptide Lfampin kills Entamoeba histolytica trophozoites by necrosis and resolves amoebic intracecal infection in mice

Amoebiasis caused by the protozoan parasite Entamoeba histolytica remains a public health problem in developing countries, making the identification of new anti-amoebic compounds a continuing priority. Previously, we have shown that lactoferrin (Lf) and several Lf-derived peptides exhibit in vitro anti-amoebic activity independently of their iron-binding activity. Here, we evaluated the amoebicidal effect of synthetic Lf-derived peptides Lfcin-B, Lfcin 17-30, and Lfampin, analyzed the mechanism of death induced by the peptides and determined their therapeutic effects on murine intestinal amoebiasis. MTT assays in trophozoite cultures of E. histolytica exposed to each peptide (1–1000 μM) showed that Lfampin is far more amoebicidal than Lfcins. Lfampin killed 80% of trophozoites at doses higher than 100 μM in 24 h, and FACs analysis using Annexin V/propidium iodide showed that death occurred mainly by necrosis. In contrast, Lfcin-B and Lfcin 17-30 appeared to have no significant effect on amoebic viability. FACs and confocal microscopy analysis using FITC-labeled peptides showed that all three peptides are internalized by the amoeba mainly using receptor (PI3K signaling) and actin-dependent pathways but independent of clathrin. Docking studies identified cholesterol in the amoeba’s plasma membrane as a possible target of Lfampin. Oral treatment of intracecally infected mice with the abovementioned peptides at 10 mg/kg for 4 days showed that Lfampin resolved 100% of the cases of intestinal amoebiasis, whereas Lfcin 17-30 and Lfcin-B were effective in resolving infection in 80 and 70% of cases, respectively. These data show that although synthetic bovine Lf-derived peptides exhibit varying amoebicidal potentials in vitro, they do resolve murine intestinal amoebiasis efficiently, suggesting that they may be useful as a therapeutic treatment.

Lactoferrin and lactoferricin endocytosis halt Giardia cell growth and prevent infective cyst production

Lactoferrin (LF) is an 80 KDa iron-binding glycoprotein that plays a significant role in the innate immune system and is considered to be an important microbicide molecule. It has been suggested to be effective in the treatment of giardiasis, an intestinal disease caused by the protozoan parasite G. lamblia. However, the molecular mechanisms by which LF exerts its effect on this parasite are unknown. Most of the microbicidal activity of human or bovine LF (hLF or bLF) has been associated with the N-terminal region of the mature LF - lactoferricin (LFcin). LFcin is produced by pepsin cleavage of the native protein in vitro and likely in vivo. In this work, we analyse the participation of the endocytic machinery of G. lamblia in the internalization of bLF and bLFcin and their effects on cell homeostasis. Our results show that, when bLF or bLFcin are internalized by receptor-mediated endocytosis, cell growth stops, and morphological changes are produced in the trophozoites, which ultimately will produce immature cysts. Our findings contribute to disclose the fine mechanism by which bLF and bLFcin may function as an antigiardial molecule and why they have therapeutic potential to eradicate giardiasis.

Antibacterial and immunomodulatory activities of bovine lactoferrin against Escherichia coli O157:H7 infections in cattle

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a zoonotic pathogen that causes food-borne disease in humans ranging from watery diarrhea to bloody diarrhea and severe hemorrhagic colitis, renal failure and hemolytic uremic syndrome. Cattle, the most important source of E. coli O157:H7 transmission to humans, harbor the bacteria in their gastrointestinal tract without showing clinical symptoms. Prevention of E. coli O157:H7 infections in ruminants could diminish the public health risk. However, there is no specific treatment available nor a vaccine or a therapeutic agent which completely prevents E. coli O157:H7 infections in cattle. This paper provides an overview of latest research data on eradicating enterohemorrhagic E. coli O157:H7 in ruminants by use of bovine lactoferrin administration. The article provides insights into the anti-microbial and immunomodulatory activities of bovine lactoferrin against E. coli O157:H7 infections in cattle.

Bovine Lactoferrin and Lactoferrin-Derived Peptides Inhibit the Growth of Vibrio cholerae and Other Vibrio species

Vibrio is a genus of Gram-negative bacteria, some of which can cause serious infectious diseases. Vibrio infections are associated with the consumption of contaminated food and classified in Vibrio cholera infections and non-cholera Vibrio infections. In the present study, we investigate whether bovine lactoferrin (bLF) and several synthetic peptides corresponding to bLF sequences, are able to inhibit the growth or have bactericidal effect against V. cholerae and other Vibrio species. The antibacterial activity of LF and LF-peptides was assessed by kinetics of growth or determination of colony forming unit in bacteria treated with the peptides and antibiotics. To get insight in the mode of action, the interaction between bLF and bLF-peptides (coupled to FITC) and V. cholera was evaluated. The damage of effector-induced bacterial membrane permeability was measured by inclusion of the fluorescent dye propidium iodide using flow cytometry, whereas the bacterial ultrastructural damage in bacteria treated was observed by transmission electron microscopy. The results showed that bLF and LFchimera inhibited the growth of the V. cholerae strains; LFchimera permeabilized the bacteria which membranes were seriously damaged. Assays with a multidrug-resistant strain of Vibrio species indicated that combination of sub-lethal doses of LFchimera with ampicillin or tetracycline strongly reduced the concentration of the antibiotics to reach 95% growth inhibition. Furthermore, LFchimera were effective to inhibit the V. cholerae counts and damage due to this bacterium in a model mice. These data suggest that LFchimera and bLF are potential candidates to combat the V. cholerae and other multidrug resistant Vibrio species.

Lactoferrin: Balancing Ups and Downs of Inflammation Due to Microbial Infections

Lactoferrin (Lf) is a glycoprotein of the primary innate immune-defense system of mammals present in milk and other mucosal secretions. This protein of the transferrin family has broad antimicrobial properties by depriving pathogens from iron, or disrupting their plasma membranes through its highly cationic charge. Noteworthy, Lf also exhibits immunomodulatory activities performing up- and down-regulation of innate and adaptive immune cells, contributing to the homeostasis in mucosal surfaces exposed to myriad of microbial agents, such as the gastrointestinal and respiratory tracts. Although the inflammatory process is essential for the control of invasive infectious agents, the development of an exacerbated or chronic inflammation results in tissue damage with life-threatening consequences. In this review, we highlight recent findings in in vitro and in vivo models of the gut, lung, oral cavity, mammary gland, and liver infections that provide experimental evidence supporting the therapeutic role of human and bovine Lf in promoting some parameters of inflammation and protecting against the deleterious effects of bacterial, viral, fungal and protozoan-associated inflammation. Thus, this new knowledge of Lf immunomodulation paves the way to more effective design of treatments that include native or synthetic Lf derivatives, which may be useful to reduce immune-mediated tissue damage in infectious diseases.