Antiviral activity of ovotransferrin discloses an evolutionary strategy for the defensive activities of lactoferrin

Genetic resilience in chickens against bacterial, viral and protozoal pathogens

The genome contributes to the uniqueness of an individual breed, and enables distinctive characteristics to be passed from one generation to the next. The allelic heterogeneity of a certain breed results in a different response to a pathogen with different genomic expression. Disease resistance in chicken is a polygenic trait that involves different genes that confer resistance against pathogens. Such resistance also involves major histocompatibility (MHC) molecules, immunoglobulins, cytokines, interleukins, T and B cells, and CD4+ and CD8+ T lymphocytes, which are involved in host protection. The MHC is associated with antigen presentation, antibody production, and cytokine stimulation, which highlight its role in disease resistance. The natural resistance-associated macrophage protein 1 (Nramp-1), interferon (IFN), myxovirus-resistance gene, myeloid differentiation primary response 88 (MyD88), receptor-interacting serine/threonine kinase 2 (RIP2), and heterophile cells are involved in disease resistance and susceptibility of chicken. Studies related to disease resistance genetics, epigenetics, and quantitative trait loci would enable the identification of resistance markers and the development of disease resistance breeds. Microbial infections are responsible for significant outbreaks and have blighted the poultry industry. Breeding disease-resistant chicken strains may be helpful in tackling pathogens and increasing the current understanding on host genetics in the fight against communicable diseases. Advanced technologies, such as the CRISPR/Cas9 system, whole genome sequencing, RNA sequencing, and high-density single nucleotide polymorphism (SNP) genotyping, aid the development of resistant breeds, which would significantly decrease the use of antibiotics and vaccination in poultry. In this review, we aimed to reveal the recent genetic basis of infection and genomic modification that increase resistance against different pathogens in chickens.

Ovotransferrin exerts bidirectional immunomodulatory activities via TLR4-mediated signal transduction pathways in RAW264.7 cells

The immune regulation function of ovotransferrin (OVT) explored using the RAW264.7 was induced by lipopolysaccharide (LPS) as vitro model in this study. The results showed that RAW264.7 cultured with OVT (200 μg/ml) alone not only enhanced the phagocytic activity and the production and expression of inflammatory factors, but also expression of toll-like receptor 4 (TLR4) gene was significantly promoted by OVT. OVT (50 μg/ml) significantly inhibited the secretion and expression of inflammatory factors in LPS-stimulated RAW264.7, but CD14 and TLR4 genes expressions were no obvious effects. Inflammatory cytokines and NO secreted by OVT-induced macrophages pretreated with inhibitors of TLR4 were down-regulated. We further verified the effects of OVT on inflammatory signaling pathway-related proteins through immunofluorescence and western blotting, MyD88, TLR4 and the phosphorylation of IκBα and p65 were significantly promoted by OVT, but there was no significant effects on the phosphorylation of IRF3. OVT promoted the phosphorylation of ERK and p38 in RAW264.7 and inhibited the phosphorylated expression of MAPK in LPS-mediated inflammation. These results indicated that OVT had the bidirectional immunoregulatory function through TLR4-mediated NF-κB/MAPK signaling pathway, that is, anti-inflammatory effect of low concentration and immune-enhancing activity of high concentration were showed. That provides a theoretical utilization for the development and utilization of OVT.

Ovotransferrin Supplementation Improves the Iron Absorption: An In Vitro Gastro-Intestinal Model

Transferrins constitute the most important iron regulation system in vertebrates and some invertebrates. Soluble transferrins, such as bovine lactoferrin and hen egg white ovotransferrin, are glycoproteins with a very similar structure with lobes that complex with iron. In this in vitro study, a comparison of bovine lactoferrin and ovotransferrin was undertaken to confirm the comparability of biological effects. An in vitro gastric barrier model using gastric epithelial cells GTL-16 and an in vitro intestinal barrier model using CaCo-2 cells was employed to evaluate iron absorption and barrier integrity. An analysis of the molecular pathways involving DMT-1 (divalent metal transporter 1), ferritin and ferroportin was also carried out. These in vitro data demonstrate the activity of both 15% saturated and 100% saturated ovotransferrin on the iron regulation system. Compared with the commercial bovine lactoferrin, both 15% saturated and 100% saturated ovotransferrin were found to act in a more physiological manner. Based on these data, it is possible to hypothesise that ovotransferrin may be an excellent candidate for iron supplementation in humans; in particular, 15% saturated ovotransferrin is the overall best performing product. In vivo studies should be performed to confirm this in vitro data.

Functional properties of ovotransferrin from chicken egg white and its derived peptides: a review

With emerging trends in the food and pharmaceutical industries, potential applications of egg-derived bioactive compounds were recognized. Ovotransferrin is a major egg white functional protein responsible for multiple bioactivities. The objectives of this review are to provide scientific evidence of the functional properties of chicken ovotransferrin and its derived peptides and to identify future research approaches and applications. Various easy, economical, and non-toxic methods have been reported to produce ovotransferrin with high yield and purity, and chemical and enzymatic approaches have been employed to release bioactive peptides. The native ovotransferrin is known to have antimicrobial, antioxidant, anticancer, and immunomodulatory activities. The peptides produced from ovotransferrin also are reported to have antioxidant, antimicrobial, antihypertensive, and anticancer properties. However, little or no application of these compounds in the food and pharmaceutical areas is available yet. Therefore, the practical application of OTF in nutraceutical and pharmaceutical areas are among the emerging areas of research.

The potential of lactoferrin, ovotransferrin and lysozyme as antiviral and immune-modulating agents in COVID-19

Coronavirus disease 2019 (COVID-19), caused by SARS coronavirus 2 (SARS-CoV-2), is spreading rapidly with no established effective treatments. While most cases are mild, others experience uncontrolled inflammatory responses with oxidative stress, dysregulation of iron and coagulation as features. Lactoferrin, ovotransferrin and lysozyme are abundant, safe antimicrobials that have wide antiviral as well as immunomodulatory properties. In particular, lactoferrin restores iron homeostasis and inhibits replication of SARS-CoV, which is closely related to SARS-CoV-2. Ovotransferrin has antiviral peptides and activities that are shared with lactoferrin. Both lactoferrin and lysozyme are ‘immune sensing’ as they may stimulate immune responses or resolve inflammation. Mechanisms by which these antimicrobials may treat or prevent COVID-19, as well as sources and forms of these, are reviewed.

In Vitro Immune-Enhancing Activity of Ovotransferrin from Egg White via MAPK Signaling Pathways in RAW 264.7 Macrophages

Ovotransferrin (OTF) is a well-known protein of the transferrin family with strong iron chelating activity, resulting in its antimicrobial activity. Furthermore, OTF is known to have antioxidant, anticancer, and antihypertensive activities. However, there have been few studies about the immune-enhancing activity of OTF. In current study, we investigated the immune-enhancing activity of OTF using the murine macrophage cells in vitro. The effect of OTF on production of pro-inflammatory mediators and cytokines were determined using Griess assay and quantitative real-time PCR. Using Neutral Red uptake assay, we confirmed the effect of OTF on phagocytic activity of macrophages. Ovotransferrin significantly increased the production of nitric oxide (NO) and secretion of inducible nitric oxide synthase (iNOS) mRNA with no cytotoxic activity. Ovotransferrin (2 mg/mL) stimulated NO production up to 31.9±3.5 μM. Ovotransferrin significantly increased the mRNA expression levels of pro-inflammatory cytokines which are tumor necrosis factor-α (TNF-α), Interleukin-1β (IL-1β), and IL-6: OTF (2 mg/mL) treatment increased the secretion of mRNA for TNF-α, IL-1β, and IL-6 by 22.20-, 37.91-, and 6.17-fold of the negative control, respectively. The phagocytic activity of macrophages was also increased by OTF treatment significantly compared with negative control. Also, OTF treatment increased phosphorylation level of MAPK signaling pathways. These results indicated that OTF has immune-enhancing activity by activating RAW 264.7 macrophages via MAPK pathways.

Overexpressing ovotransferrin and avian β-defensin-3 improves antimicrobial capacity of chickens and poultry products

Zoonotic and foodborne diseases pose a significant burden, decreasing both human and animal health. Modifying chickens to overexpress antimicrobials has the potential to decrease bacterial growth on poultry products and boost chicken innate immunity. Chickens overexpressing either ovotransferrin or avian β-defensin-3 (AvβD3) were generated using Tol-2 transposons. Transgene expression at the RNA and protein level was seen in egg white, breast muscle, and serum. There were significant differences in the immune cell populations in the blood, bursa, and spleen associated with transgene expression including an increased proportion of CD8+ cells in the blood of ovotransferrin and AvβD3 transgenic birds. Expression of the antimicrobials inhibited the in vitro growth of human and chicken bacterial pathogens and spoilage bacteria. For example, transgene expression significantly reduced growth of aerobic and coliform bacteria in breast muscle and decreased the growth of Salmonella enterica in egg white. Overall these results indicate that overexpression of antimicrobials in the chicken can impact the immune system and increase the antimicrobial capacity of poultry products.

PC2 Ovotransferrin: Characterization and Alternative Immunotherapeutic Activity

Characterization and evaluation of immunotherapeutic potential of ovotransferrin PC2 (OTf PC2) were performed in this study. The ovoprotein was obtained from egg white from hens immunized with bacterial antigens, pathogenic for humans. For the negative control samples, OTf was extracted from eggs collected from Specific Pathogen-Free (SPF) hens and purified by affinity chromatography on Protein G-agarose column with two eluting peaks: I, representing ovalbumin, and II, ovotransferrin. The final apo-OTf form was reached by successive precipitation with ammonium sulfate and citric acid and the holo-OTf form by saturating the apo-form with FeCl3. Multiple OTf PC2 samples were analyzed through Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and, based on the molecular marker migration model, the ovotransferrin (76.5 kDa) and ovalbumin (45 kDa) were detected. The agglutination reaction exhibited statistically significant high specificity of the multiple OTf PC2, by reacting with the antigens used for hens' immunization. Following ELISA, it was established that OTf PC2 from hyperimmune eggs has specificity for all antigens; the antibody titer was high, indicating that OTf PC2 possesses immunological properties similar to immunoglobulin Y (Ig Y). This study suggests that OTf PC2 immunological activity may play a crucial role in the prevention and treatment of infections resistant to antibiotics and OTf PC2 can also act as a valuable nutraceutical.

The Utility of Ovotransferrin and Ovotransferrin-Derived Peptides as Possible Candidates in the Clinical Treatment of Cardiovascular Diseases

Several of the most prevalent etiological factors which contribute towards global death rates are associated with cardiovascular diseases (CVDs), which include a range of conditions such as angina, rheumatic heart disease, and venous thrombosis. Extensive research has been conducted into the role played by oxidative stress and inflammation in the functional transformations associated with the progression of CVDs, while the research findings from these investigations have been both fruitful and informative. In view of the adverse secondary effects that result from the clinical administration of many synthetic medications, research which explored the treatment of severe and long-lasting conditions, including CVDs, has primarily centered on the potential benefits displayed by natural agents, one of which is food protein-based bioactive peptides. Most importantly, previous research has revealed the possible benefits associated with these products' anti-inflammatory and antioxidant characteristics. In light of these considerations, this paper aims to review the degree to which ovotransferrin (otrf, also referred to as conalbumin) and otrf-derived peptides, including IRW, IQW, and KVREGT, are, by virtue of their anti-inflammatory and antioxidant characteristics, viable treatment agents for endothelial dysfunction and the prevention of CVD.

Chicken Ovotransferrin Variants OTFB and OTFC Harboring Substitution of GAT (Asp) to AAT (Asn) in the Codon 500 and their Antimicrobial Activity

Chicken egg white ovotransferrin (OTF) has been reported to exist in three electrophoretic variants (OTF^A, OTF^B and OTF^C). In this report, we identified a causal polymorphism between the OTF^B and OTF^C variants in Japanese and Taiwanese native chickens and compared the antibacterial activity between these two variants. The cDNA sequence analyses from Satsumadori oviducts revealed that three non-synonymous SNPs T1809G (Ser52Ala), A2258G (Ile96Val) and G7823A (Asp500Asn) corresponded to the OTF electrophoretic phenotypes. Of the three SNPs, the G7823A mutation perfectly corresponded to the electrophoretic phenotypes OTF^B (G/G, Asp500Asp), OTF^B/C (G/A, Asp500Asn) and OTF^C (A/A, Asn500Asn) in three chicken populations. The variants OTF^B and OTF^C exhibited similar antibacterial potency against Gram-positive and Gram-negative bacteria. This study provides, for the first time, molecular information on polymorphism of OTF^B and OTF^C variants of chicken ovotransferrin and its effect on the antimicrobial activity of the respective variants.

Hyphenated Analytical Methods in Determination of Biologically Active Compounds in Hen's Eggs

Hen's egg is a complete material needed for the development of the embryo; it is an important source of nutraceutical compounds, such as protein, fats, vitamins, trace metals, and minerals. Moreover, avian egg contains biologically active compounds that exhibit antibacterial and antimicrobial activities as well as antitumor, antiviral, antioxidant, immunomodulating, and therapeutic properties. Eggs are mostly very good sources of valuable, easily digestible proteins. This review focuses on the biologically active compounds from hen's egg and applications of these compounds in medicine and the pharmaceutical industry. Additionally, it gives an overview of the hyphenated separation techniques, including sample preparation, analysis, and identification, used in the proteomics and lipidomics analysis.

The Nutraceutical Properties of Ovotransferrin and Its Potential Utilization as a Functional Food

Ovotransferrin or conalbumin belong to the transferrin protein family and is endowed with both iron-transfer and protective activities. In addition to its well-known antibacterial properties, ovotransferrin displays other protective roles similar to those already ascertained for the homologous mammalian lactoferrin. These additional functions, in many cases not directly related to iron binding, are also displayed by the peptides derived from partial hydrolysis of ovotransferrin, suggesting a direct relationship between egg consumption and human health.

Lactoferrin and ovotransferrin contribute toward antioxidative effects of Edible Bird's Nest against hydrogen peroxide-induced oxidative stress in human SH-SY5Y cells

There are reports of improved redox outcomes due to consumption of Edible Bird's Nest (EBN). Many of the functional effects of EBN can be linked to its high amounts of antioxidants. Interestingly, dietary components with high antioxidants have shown promise in the prevention of aging and its related diseases like Alzheimer's disease. In this study, the antioxidative potentials of EBN and its constituents, lactoferrin (LF) and ovotransferrin (OVF), were determined and protective effects against hydrogen peroxide (H2O2)- induced toxicity on SH-SY5Y cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and acridine orange and propidium iodide (AO/PI) staining with microscopy were examined. Results showed that EBN and its constituents attenuated H2O2-induced cytotoxicity, and decreased radical oxygen species (ROS) through increased scavenging activity. Furthermore, LF, OVF, and EBN produced transcriptional changes in antioxidant related genes that tended towards neuroprotection as compared to H2O2-treated group. Overall, the results suggest that LF and OVF may produce synergistic or all-or-none antioxidative effects in EBN.

Bioactive peptides from egg: a review

Purpose

– The aim of the article was to focus on various peptides identified in the egg and their probable application as novel ingredients in the development of functional food products. Bioactive peptides of egg origin have attracted increasing interest as one of the prominent candidates for development of various health-promoting functional and designer foods.

Design/methodology/approach

– Traditionally known as a source of highly valuable proteins in human nutrition, eggs are nowadays also considered as an important source of many bioactive peptides which may find wide application in medicine and food production. These specific protein fragments from egg proteins which, above and beyond their nutritional capabilities, have a positive impact on the body’s function or condition by affecting the digestive, endocrine, cardiovascular, immune and nervous systems, and may ultimately influence health.

Findings

– Several peptides that are released in vitro or in vivo from egg proteins have been attributed to different health effects, including antihypertensive effects, antimicrobial properties, antioxidant activities, anticancer activity, immunomodulating activity, antiadhesive properties and enhancement of nutrient absorption and/or bioavailability. Extensive research has been undertaken to identify and characterize these biologically active peptides of egg origin which has changed the image of egg as a new source of biologically active ingredients for the development of functional foods with specific benefits for human health and treatment and prevention of diseases.

Originality/value

– The paper mainly describes the above-stated properties of bioactive peptides derived from egg proteins.

Unraveling molecular mechanistic differences in liver metabolism between lean and fat lines of Pekin duck (Anas platyrhynchos domestica): a proteomic study

Duck is one of the major poultry meat sources for human consumption. To satisfy different eating habits, lean and fat strains of Pekin ducks have been developed. The objective of this study was to determine the molecular mechanistic differences in liver metabolism between two duck strains. The liver proteome of the Pekin duck lines was compared on days 1, 14, 28, and 42 posthatching using 2-DE based proteomics. There was a different abundance of 76 proteins in the livers of the two duck lines. Fat ducks strongly expressed proteins related to pathways of glycolysis, ATP synthesis, and protein catabolism, suggesting enhanced fat deposition rather than protein retention. In contrast, highly expressed proteins in lean ducks improved protein anabolism and reduced protein catabolism, resulting in an enhancement of lean meat deposition. Along with the decrease in fat deposition, the immune system of the lean duck strain may be enhanced by enhanced expression of proteins involved in stress response, immune defense, and antioxidant functions. These results indicate that selection pressure has shaped the two duck lines differently resulting in different liver metabolic capacities. These observed variations between the two strains at the molecular level are matched with physiological changes in growth performance and meat production. This information may have beneficial impacts in areas such as genetic modification through the manipulation of target proteins or genes in specific pathways to improve the efficiency of duck meat production.

BIOLOGICAL SIGNIFICANCE

The objective of this study was to unravel molecular mechanistic differences in liver metabolism between lean and fat Pekin duck (Anas platyrhynchos domestica) strains. There was a different abundance of 76 proteins in the livers of the two duck lines. Enhanced protein expression in the fat ducks related to pathways of glycolysis, ATP synthesis and protein catabolism suggesting increased fat deposition rather than protein retention. In contrast, highly expressed proteins in the lean ducks facilitated protein deposition by increasing protein anabolism and reducing protein catabolism to enhance the lean meat percentage. Along with the decrease of fat deposition, the immunity of lean duck appeared to be enhanced by increased expression of proteins involved in stress response, defense and antioxidant function. This study provides potential target proteins or genes for further functional analysis and genetic manipulation to increase the efficiency of duck meat production and help satisfy the global demand for poultry meat.

Effect of high pressure treatment on ovotransferrin

High pressure processing of ovotransferrin was carried out to study the structural and physiochemical changes of ovotransferrin under various pressure levels. At pH 8 and pressures higher than 200 MPa, a decrease in total sulfhydryl groups and an increase in surface hydrophobicity were observed along with a partial aggregation. A gradual shift of denaturation peak towards higher temperature was noticed up to 500 MPa, leading to a total loss of the enthalpy of denaturation at pressures of 600 and 700 MPa, where a significant decrease in intrinsic fluorescence was also observed. At pH 3, the ovotransferrin adopted a molten globule state, associated with a significant increase in surface hydrophobicity and reactive sulfhydryl content; structurally, no clear denaturation peaks in differential scanning calorimetry (DSC) were detected at any level of pressure treatment whereas a noticeable decrease in intrinsic fluorescence was evidenced up to 600 MPa and then increased at 700 MPa pressure treatment. Fourier transform infrared spectroscopy (FT-IR) revealed that the conformational structure were changed from helices, sheets, turns, and aggregated strand to mostly intermolecular β-sheets or aggregated strands at pH 8 at 200 MPa but switched back to original structure at higher pressures.

Evolution of immune functions of the mammary gland and protection of the infant

Abstract The evolution of immunological agents in milk is intertwined with the general aspects of the evolution of the mammary gland. In that respect, mammalian precursors emerged from basal amniotes some 300 million years ago. In contrast to the predominant dinosaurs, proto-mammals possessed a glandular skin. A secondary palate in the roof of the mouth that directed airflow from the nostrils to the oropharynx and thus allowed mammals to ingest and breathe simultaneously first appeared in cynodonts 230 million years ago. This set the stage for mammalian newborns to nurse from the future mammary gland. Interplays between environmental and genetic changes shaped mammalian evolution including the mammary gland from dermal glands some 160 millions of years ago. It is likely that secretions from early mammary glands provided nutrients and immunological agents for the infant. Natural selection culminated in milks uniquely suited to nourish and protect infants of each species. In human milk, antimicrobial, anti-inflammatory, and immunoregulatory agents and living leukocytes are qualitatively or quantitatively different from those in other mammalian milks. Those in human milk compensate for developmental delays in the immunological system of the recipient infant. Consequently, the immune system in human milk provided by evolution is much of the basis for encouraging breastfeeding for human infants.

Identification of five reptile egg whites protein using MALDI-TOF mass spectrometry and LC/MS-MS analysis

Proteomics of egg white proteins of five reptile species, namely Siamese crocodile (Crocodylus siamensis), soft-shelled turtle (Trionyx sinensis taiwanese), red-eared slider turtle (Trachemys scripta elegans), hawksbill turtle (Eretmochelys imbricate) and green turtle (Chelonia mydas) were studied by 2D-PAGE using IPG strip pH 4-7 size 7 cm and IPG strip pH 3-10 size 24 cm. The protein spots in the egg white of the five reptile species were identified by MALDI-TOF mass spectrometry and LC/MS-MS analysis. Sequence comparison with the database revealed that reptile egg white contained at least seven protein groups, such as serpine, transferrin precursor/iron binding protein, lysozyme C, teneurin-2 (fragment), interferon-induced GTP-binding protein Mx, succinate dehydrogenase iron-sulfur subunit and olfactory receptor 46. This report confirms that transferrin precursor/iron binding protein is the major component in reptile egg white. In egg white of Siamese crocodile, twenty isoforms of transferrin precursor were found. Iron binding protein was found in four species of turtle. In egg white of soft-shelled turtle, ten isoforms of lysozyme were found. Apart from well-known reptile egg white constituents, this study identified some reptile egg white proteins, such as the teneurin-2 (fragment), the interferon-induced GTP-binding protein Mx, the olfactory receptor 46 and the succinate dehydrogenase iron-sulfur subunit.

Physiological roles of ovotransferrin

BACKGROUND

Ovotransferrin is an iron-binding glycoprotein, found in avian egg white and in avian serum, belonging to the family of transferrin iron-binding glycoproteins. All transferrins show high sequence homology. In mammals are presents two different soluble glycoproteins with different functions: i) serum transferrin that is present in plasma and committed to iron transport and iron delivery to cells and ii) lactoferrin that is present in extracellular fluids and in specific granules of polymorphonuclear lymphocytes and committed to the so-called natural immunity. To the contrary, in birds, ovotransferrin remained the only soluble glycoprotein of the transferrin family present both in plasma and egg white.

SCOPE OF REVIEW

Substantial experimental evidences are summarized, illustrating the multiple physiological roles of ovotransferrin in an attempt to overcome the common belief that ovotransferrin is a protein dedicated only to iron transport and to iron withholding antibacterial activity.

MAJOR CONCLUSIONS

Similarly to the better known family member protein lactoferrin, ovotransferrin appears to be a multi-functional protein with a major role in avian natural immunity.

GENERAL SIGNIFICANCE

Biotechnological applications of ovotransferrin and ovotransferrin-related peptides could be considered in the near future, stimulating further research on this remarkable protein. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.

Lactoferrin and cancer disease prevention

Lactoferrin (LF) is an iron-binding glycoprotein that is composed of the transferrin family and is predominantly found in the products of the exocrine glands located in the gateways of the digestive, respiratory, and reproductive systems, suggesting a role in the non-specific defence against invading pathogens. Additionally, several physiological roles have been attributed to LF, namely regulation of iron homeostasis, host defence against infection and inflammation, regulation of cellular growth, and differentiation and protection against cancer development and metastasis. These findings have suggested LF's great potential therapeutic use in cancer disease prevention and/or treatment, namely as a chemopreventive agent. This review looks at the recent advances in understanding the mechanisms underlying the multifunctional roles of LF and future perspectives on its potential therapeutic applications.

Recent advances in the understanding of egg allergens: basic, industrial, and clinical perspectives

The emergence of egg allergy has had both industrial and clinical implications. In industrialized countries, egg allergy accounts for one of the most prevalent food hypersensitivities, especially in children. Atopic dermatitis represents the most common clinical manifestation in infancy; however, the range of clinical signs is broad and encompasses life-threatening anaphylaxis. The dominant egg allergens are proteins and are mainly present in the egg white, for example, ovalbumin, ovomucoid, ovotransferrin, and lysozyme. However, egg yolk also displays low-level allergenicity, for example, alpha-livetin. Strict avoidance of the offending food remains the most common recommendation for egg-allergic individuals. Nevertheless, the omnipresence of egg-derived components in prepackaged or prepared foods makes it difficult. Therefore, more efficient preventive approaches are investigated to protect consumers from inadvertent exposure and ensuing adverse reactions. On the one hand, commercial kits have become readily available that allow for the detection of egg contaminants at trace levels. On the other hand, attempts to produce hypoallergenic egg-containing products through food-processing techniques have met with promising results, but the approach is limited due to its potentially undesirable effects on the unique functional and sensory attributes of egg proteins. Therefore, the development of preventive or curative strategies for egg allergy remains strongly warranted. Pilot studies have suggested that oral immunotherapy (IT) with raw or cooked preparations of egg may represent a safe alternative, immediately available to allergic subjects, but remains applicable to only nonanaphylactic patients. Due to the limitations of conventional IT, novel forms of immunotherapy are sought based on information obtained from the molecular characterization of major egg allergens. In the past decade, promising approaches to the treatment and prevention of egg allergy have been explored and include, among others, the production of hypoallergenic recombinant egg proteins, the development of customized peptides, and bacterial-mediated immunotherapy. Nonspecific approaches have also been evaluated, and preliminary trials with the use of probiotic bacteria have yielded encouraging results. The current understanding of egg allergens offers novel approaches toward the making of food products safe for human consumption and the development of efficient immunotherapeutic strategies.

Evaluation of the prophylactic use of ovotransferrin against chlamydiosis in SPF turkeys

Chlamydophila (C.) psittaci infections are highly prevalent in turkeys and the economical and public health importance of these infections has been recognized since 1950. As there are no vaccines, antibiotic treatment (tetracylines, enrofloxacine) is often needed to allow marketing of poultry. In this study, we explored the use of ovotransferrin (ovoTF), a natural anti-microbial protein, in preventing an experimental C. psittaci infection in specific pathogen free (SPF) turkeys. Turkeys were treated with aerosolized ovoTF prior to the infection. Groups 1 and 2 received a single dose of 10 and 5 mg ovoTF per turkey, respectively. Group 3 received a daily dose of 5mg ovoTF per turkey during 12 days. Group 4 served as untreated, infected control group. Turkeys were aerosol infected using 10(6) TCID(50) of the virulent C. psittaci serovar/genotype D strain 92/1293. Birds were monitored (clinical signs, bacterial excretion) during 12 subsequent days before being necropsied. At necropsy, pathology and C. psittaci replication in various tissues was examined. A single dose of 10mg ovoTF and a repeated daily dose of 5mg ovoTF could not prevent the birds from becoming infected with C. psittaci, but they significantly reduced the outcome of the infection. A single dose of 5mg ovoTF had no influence on the outcome of the infection as compared to the non-treated infected controls. Our results demonstrate the anti-chlamydial effect of ovoTF in vivo and present a base for further research on practical applications of ovoTF on turkey farms.

Utilization of lactoferrin-bound and transferrin-bound iron by Campylobacter jejuni

Campylobacter jejuni NCTC 11168 was capable of growth to levels comparable with FeSO4 in defined iron-limited medium (minimal essential medium alpha [MEMalpha]) containing ferrilactoferrin, ferritransferrin, or ferri-ovotransferrin. Iron was internalized in a contact-dependent manner, with 94% of cell-associated radioactivity from either 55Fe-loaded transferrin or lactoferrin associated with the soluble cell fraction. Partitioning the iron source away from bacteria significantly decreased cellular growth. Excess cold transferrin or lactoferrin in cultures containing 55Fe-loaded transferrin or lactoferrin resulted in reduced levels of 55Fe uptake. Growth of C. jejuni in the presence of ferri- and an excess of apoprotein reduced overall levels of growth. Following incubation of cells in the presence of ferrilactoferrin, lactoferrin became associated with the cell surface; binding levels were higher after growth under iron limitation. A strain carrying a mutation in the cj0178 gene from the iron uptake system Cj0173c-Cj0178 demonstrated significantly reduced growth promotion in the presence of ferrilactoferrin in MEMalpha compared to wild type but was not affected in the presence of heme. Moreover, this mutant acquired less 55Fe than wild type when incubated with 55Fe-loaded protein and bound less lactoferrin. Complementation restored the wild-type phenotype when cells were grown with ferrilactoferrin. A mutant in the ABC transporter system permease gene (cj0174c) showed a small but significant growth reduction. The cj0176c-cj0177 intergenic region contains two separate Fur-regulated iron-repressible promoters. This is the first demonstration that C. jejuni is capable of acquiring iron from members of the transferrin protein family, and our data indicate a role for Cj0178 in this process.

Ovotransferrin expression and release by chicken cell lines infected with Marek's disease virus

Mammals posses both serum transferrin and lactoferrin, whose functions are taken over in birds by ovotransferrin, displaying both iron transport and antibacterial activities. Ovotransferrin also exerts antiviral activity towards Marek's disease virus, an avian member of the herpes family of viruses. This virus infects lymphoid organs and induces the transcription of ovotransferrin in infected chicken embryo fibroblasts. However, it has not yet been established whether ovotransferrin gene transcription is linked to the release of the protein outside the cells or whether ovotransferrin expression and release also occurs in chicken lymphoblastoid cells in which the Marek's disease viral genome is integrated. Our results indicate that both serum and egg-white isoforms of ovotransferrin are expressed and released in the supernatants of chicken embryo fibroblast and lymphoblastoid cells in the absence of infection. Viral infection of chicken embryo fibroblasts caused a slight increase of ovotransferrin release, whereas viral reinfection of lymphoblastoid cells caused a remarkable ovotransferrin release in a virus concentration-dependent manner. These findings suggest that ovotransferrin release in vivo may play a crucial role in protecting the whole organism from viral infection spreading, and support the hypothesis that the antiviral activity of ovotransferrin is an important part of the innate immune response in birds, resembling the antiviral activity of lactoferrin in mammals.

Effect of ovotransferrin and lactoferrins onChlamydophila psittaciadhesion and invasion in HD11 chicken macrophages

The effect of ovotransferrin (ovoTF), human lactoferrin (hLF) and bovine lactoferrin (bLF) on the obligate intracellular pathogen Chlamydophila (Cp.) psittaci was evaluated using a model of Buffalo Green Monkey kidney (BGM) cells and HD11 chicken macrophages as artificial hosts. Firstly, the effect of transferrins on the infectivity of the bacteria was evaluated. Pre-incubation of Cp. psittaci with 0.5 to 5 mg/mL ovoTF prior to infecting BGM cells significantly lowered the infection rate (P < 0.05). For both lactoferrins, the infection rate could only be reduced with 5 mg/mL, albeit not significantly as compared to the infection rate created by the untreated bacteria. Secondly, transferrins were tested for their ability to influence bacterial adhesion and entry in HD11 cells. Maximal non-cytotoxic and non-bactericidal concentrations of 0.05 mg/mL ovoTF and 0.5 mg/mL hLF and bLF were used. Overall, ovoTF was more effective than human and bovine LF in inhibiting bacterial irreversible attachment and cell entry and the latter was accompanied by a dose-dependent reduction of actin recruitment at the bacterial entry site. However, once bacteria had entered HD11 cells, transferrins had apparently no effect on intracellular replication. The present findings suggest a possible role for transferrins and especially ovoTF, in preventing avian Cp. psittaci infections.

Iron withholding as an innate immune mechanism in the American alligator (Alligator mississippiensis)

Pathogenic microbes require Fe and Zn for growth and proliferation. Upon infection, microbes produce proteins, called sidephores, designed to strip serum divalent metals away from host proteins. Higher vertebrates respond to infection by increasing the expression of proteins that sequester serum iron away from bacteria. As a result, host plasma Fe levels decrease during the initial phases of infection. This study was conducted to determine if the American alligator, an ancient reptile, exhibits the same innate immune mechanism to protect against in vivo microbial proliferation. Intraperitoneal injection of juvenile captive alligators with bacterial lipopolysaccharide (LPS) resulted in a time-dependent decrease in plasma Fe, as determined by inductively coupled plasma emission spectroscopy. Plasma Fe levels decreased by 5.9, 10.6, and 18.6% relative to untreated control levels at 3, 6, and 12 hr post-injection, respectively, and remained decreased by 12.0% at 48 hr. Alligators injected with pyrogen-free saline did not exhibit statistically significant changes in plasma Fe concentrations at any time point observed. In contrast, serum Zn and Cu remained unchanged relative to untreated controls. To insure that the decreases in plasma Fe were not due to the repeated blood collections during the course of the kinetic study, another experiment was conducted in which plasma metals were measured at 24 hr post-injection. Once again, plasma Fe was reduced by 30.2%, whereas Zn and Cu did not exhibit appreciable changes. These results show that alligators exhibit low plasma Fe levels during an inflammatory response induced by bacterial lipopolysaccharide.

ESTs from brain and testis of White Leghorn and red junglefowl: annotation, bioinformatic classification of unknown transcripts and analysis of expression levels

We report the generation, assembly and annotation of expressed sequence tags (ESTs) from four chicken cDNA libraries, constructed from brain and testis tissue dissected from red junglefowl and White Leghorn. 21,285 5'-end ESTs were generated and assembled into 2,813 contigs and 9,737 singletons, giving 12,549 tentative unique transcripts. The transcripts were annotated using BLAST by matching to known chicken genes or to putative homologues in other species using the major gene/protein databases. The results for these similarity searches are available on www.sbc.su.se/~arve/chicken. 4,129 (32.9%) of the transcripts remained without a significant match to gene/protein databases, a proportion of unmatched transcripts similar to earlier non-mammalian EST studies. To estimate how many of these transcripts may represent novel genes, they were studied for the presence of coding sequence. It was shown that most of the unique chicken transcripts do not contain coding parts of genes, but it was estimated that at least 400 of the transcripts contain coding sequence, indicating that 3.2% of avian genes belong to previously unknown gene families. Further BLAST search against dbEST left 1,649 (13.1%) of the transcripts unmatched to any library. The number of completely unmatched transcripts containing coding sequence was estimated at 180, giving a measure of the number of putative novel chicken genes identified in this study. 84.3% of the identified transcripts were found only in testis tissue, which has been poorly studied in earlier chicken EST studies. Large differences in expression levels were found between the brain and testis libraries for a large number of transcripts, and among the 525 most frequently represented transcripts, there were at least 20 transcripts with significant difference in expression levels between red junglefowl and White Leghorn.

Advances in the value of eggs and egg components for human health

The avian egg is an important source of nutrients, containing all of the proteins, lipids, vitamins, minerals, and growth factors required by the developing embryo, as well as a number of defense factors to protect against bacterial and viral infection. Moreover, eggs are now understood to contain substances with biological functions beyond basic nutrition, and extensive research has been undertaken to identify and characterize these biologically active components. This review mainly focused on biological activities of proteins and peptides derived from egg components. Several biological activities have now been associated with egg components, including novel antimicrobial activities, antiadhesive properties, immunomodulatory, anticancer, and antihypertensive activities, antioxidant properties, protease inhibitors, nutrient bioavailability, and functional lipids, highlighting the importance of egg and egg components in human health and in disease prevention and treatment. Continued research to identify new and existing biological functions of hen egg components will help to define new methods to further improve the value of eggs as a source of numerous biologically active compounds with specific benefits for human and animal health and secure their role in the therapy and prevention of chronic and infectious disease.

Antiviral activity of ovotransferrin derived peptides

Ovotransferrin and lactoferrin are iron-binding proteins with antiviral and antibacterial activities related to natural immunity, showing marked sequence and structural homologies. The antiviral activity of two hen ovotransferrin fragments DQKDEYELL (hOtrf(219-227)) and KDLLFK (hOtrf(269-301) and hOtrf(633-638)) towards Marek's disease virus infection of chicken embryo fibroblasts is reported here. These fragments have sequence homology with two bovine lactoferrin fragments with antiviral activity towards herpes simplex virus, suggesting that these fragments could have a role for the exploitation of the antiviral activity of the intact proteins towards herpes viruses. NMR analysis showed that these peptides, chemically synthetized, did not possess any favourite conformation in solution, indicating that both the aminoacid sequence and the conformation they display in the intact protein are essential for the antiviral activity.

Mechanisms of TfR-mediated transcytosis and sorting in epithelial cells and applications toward drug delivery

Transferrin receptor has been an important protein for many of the advances made in understanding the intricacies of the intramolecular sorting pathways of endocytosed molecules. The unique internalization and recycling functions of transferrin receptor have also made it an attractive choice for drug targeting and delivery of large protein-based therapeutics and toxins. Recent advances in elucidating the role of the intracellular controllers of transferrin recycling and sorting, such as Rab proteins and their effectors, have led to enhancement of transferrin receptor as a drug delivery vehicle. This review focuses on the use of transferrin receptor as an agent for facilitating drug delivery and targeting, and the role that mechanisms of transferrin receptor sorting and transcytosis play in these events.

The physiology of lactoferrin

This paper reviews our current knowledge of the structure and function of the iron-binding protein lactoferrin. In particular, it attempts to relate the various proposed physiological functions of lactoferrin to its most characteristic biochemical properties, i.e. its ability to bind iron and its highly basic nature. The extent to which various physiological functions can be considered as definitely established is critically reviewed, and suggestions for future research are proposed.