Biological role of lactoferrin

Effect of bovine lactoferrin addition to milk in yogurt manufacturing

The aim of this work was to study the effect of milk supplementation with lactoferrin of different iron saturation on the manufacturing and characteristics of yogurt. Bovine lactoferrin was added at concentrations of 0.5, 1, and 2 mg/mL in the holo (iron saturated) and apo (without iron) forms. Some physicochemical properties, such as pH, concentration of lactic acid, and texture of supplemented yogurts, were determined throughout the shelf-life period storage (28 d) at 4°C. We also evaluated the stability of lactoferrin in supplemented yogurt throughout the storage time. The supplementation of milk with bovine lactoferrin did not greatly affect the physical properties of the yogurt, though apo-lactoferrin slightly delayed the decrease of pH. This could be attributed to the partial inhibition observed on the growth of Streptococcus thermophilus. The integrity and immunoreactive concentration of lactoferrin, determined by Western blotting and noncompetitive ELISA, respectively, remained constant throughout the shelf life of yogurt.

Interfacial adsorption and denaturization of human milk and recombinant rice lactoferrin

Lactoferrin (LF) produced from recombinant technologies can achieve almost identical amino acid sequences and three-dimensional structures to those extracted from mammals, but differences often arise in the carbohydrate chains attached through N-glycosylation, with altered sizes, structures, and chemical nature. We compare the differences in solvation and interfacial adsorption from two samples, human milk lactoferrin (hLF) and recombinant rice lactoferrin (rLF). Lactoferrin is a bilobal protein with a molecular weight of about 80 kD. It has three N-glycosylation sites. Each of the three attached glycan chains on rLF contains seven to eight sugar groups. In comparison, each of the three glycan chains attached to hLF contains 12-13 sugar groups and is twice as long. The rLF meting point in 1 mg/ml aqueous solution (pH 7 phosphate buffer, I=20 mM) was 43 degrees C from dynamic light scattering, compared to 53 degrees C for hLF, exhibiting the enhanced solvation and stability of hLF due to its longer carbohydrate side chains. Silicon oxide surfaces provided a model substrate for assessment of lactoferrin adsorption and comparison with other proteins. The time dependent interfacial adsorption studied by spectroscopic ellipsometry (SE) was characterized by a fast initial step followed by a slow relaxation process. In addition, the SE results revealed the persistently higher adsorption of rLF, again showing the effect of glycan side chains. In spite of the different adsorbed amounts, neutron reflection revealed similar interfacial structures of the adsorbed protein layers. At the low lactoferrin concentration around 10 mg/l, a flat-on molecular monolayer formed with both LF lobes attached to the SiO(2) surface through electrostatic attraction. As the protein concentration increased, a secondary molecular layer further adsorbed to the first one and the attachment was again driven by electrostatic attraction. The intermixing between the globular lobes resulted in the dense packing in the middle 60 A with some of the lobes projected toward the aqueous bulk solution.

Human lactoferrin stimulates skin keratinocyte function and wound re-epithelialization

BACKGROUND

Human lactoferrin (hLF), a member of the transferrin family, is known for its antimicrobial and anti-inflammatory effects. Recent studies on various nonskin cell lines indicate that hLF may have a stimulatory effect on cell proliferation.

OBJECTIVES

To study the potential role of hLF in wound re-epithelialization.

MATERIALS AND METHODS

The effects of hLF on cell growth, migration, attachment and survival were assessed, with a rice-derived recombinant hLF (holo-rhLF), using proliferation analysis, scratch migration assay, calcein-AM/propidium iodide staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) method, respectively. The mechanisms of hLF on cell proliferation and migration were explored using specific pathway inhibitors. The involvement of lactoferrin receptor low-density lipoprotein receptor-related protein 1 (LRP1) was examined with RNA interference technique. An in vivo swine second-degree burn wound model was also used to assess wound re-epithelialization.

RESULTS

Studies revealed that holo-rhLF significantly stimulated keratinocyte proliferation which could be blocked by mitogen-activated protein kinase (MAPK) kinase 1 inhibitor. Holo-rhLF also showed strong promoting effects on keratinocyte migration, which could be blocked by either inhibition of the MAPK, Src and Rho/ROCK pathways, or downregulation of the LRP1 receptor. With cells under starving or 12-O-tetradecanoylphorbol-13-acetate exposure, the addition of holo-rhLF was found greatly to increase cell viability and inhibit cell apoptosis. Additionally, holo-rhLF significantly increased the rate of wound re-epithelialization in swine second-degree burn wounds.

CONCLUSIONS

Our studies demonstrate the direct effects of holo-rhLF on wound re-epithelialization including the enhancement of keratinocyte proliferation and migration as well as the protection of cells from apoptosis. The data strongly indicate its potential therapeutic applications in wound healing.

Transport of iron bound to recombinant human lactoferrin from rice and iron citrate across Caco-2 cell monolayers

The possibility of using recombinant human lactoferrin from rice (rhLF) makes it necessary to study its differences from the protein of milk. In this work, the binding of different iron-saturated forms of rhLF to Caco-2 cells was studied. Iron-saturated rhLF bound in higher proportion than the apo-form, but, the data obtained for specific binding were not compatible with receptor-mediated binding. Competition assays showed the same binding capacity for human milk lactoferrin as for rhLF to Caco-2 cells. Another basic protein of milk, lactoperoxidase, was found to compete with rhLF for binding to Caco-2 cell membranes, suggesting an electrostatic interaction. The transport of iron ((59)Fe) bound to rhLF and to citrate and the transport of rhLF ((125)I-labeled) were studied on Caco-2 monolayers. Transport of iron was found to be significantly greater when bound to citrate than to rhLF. The amount of intact lactoferrin that traversed the Caco-2 monolayers was very low, suggesting degradation of it across these cells.

Can lactoferrin prevent neonatal sepsis and necrotizing enterocolitis?

Despite the use of potent antimicrobials, neonatal sepsis and necrotizing enterocolitis are associated with significant mortality and morbidity. The emergence of microbial antibiotic resistance is a grave concern. Inflammation secondary to sepsis and necrotizing enterocolitis increases pulmonary and cerebral morbidity. New strategies that target inflammation and reduce the emergence of antibiotic resistance are urgently needed. Lactoferrin has broad-spectrum antimicrobial and immunomodulatory activities. In animal models of colitis, lactoferrin reduces inflammatory injury. Lactoferrin also induces the receptor-mediated proliferation and differentiation of intestinal cells. A randomized, controlled trial of lactoferrin in premature neonates to prevent late-onset sepsis is currently in progress. Lactoferrin is a promising agent in the prevention of neonatal sepsis and necrotizing enterocolitis but needs further evaluation to confirm its safety, tolerability and efficacy.

Helicobacter pylori usurps cell polarity to turn the cell surface into a replicative niche

Helicobacter pylori (Hp) intimately interacts with the gastric epithelial surface and translocates the virulence factor CagA into host cells in a contact-dependent manner. To study how Hp benefits from interacting with the cell surface, we developed live-cell microscopy methods to follow the fate of individual bacteria on the cell surface and find that Hp is able to replicate and form microcolonies directly over the intercellular junctions. On polarized epithelia, Hp is able to grow directly on the apical cell surface in conditions that do not support the growth of free-swimming bacteria. In contrast, mutants in CagA delivery are defective in colonization of the apical cell surface. Hp perturbs the polarized epithelium in a highly localized manner, since wild-type Hp does not rescue the growth defect of the CagA-deficient mutants upon co-infection. CagA's ability to disrupt host cell polarity is a key factor in enabling colonization of the apical cell surface by Hp, as disruption of the atypical protein kinase C/Par1b polarity pathway leads to rescue of the mutant growth defect during apical infection, and CagA-deficient mutants are able to colonize the polarized epithelium when given access to the basolateral cell surface. Our study establishes the cell surface as a replicative niche and the importance of CagA and its effects on host cell polarity for this purpose.

Meta-analysis: the effect of supplementation with lactoferrin on eradication rates and adverse events during Helicobacter pylori eradication therapy

BACKGROUND

Recent evidence shown that lactoferrin could exert an antimicrobial effect against Helicobacter pylori both in vitro and in vivo models. To systematically evaluate whether adding lactoferrin to H. pylori eradication regimens could improve eradication rates and reduce side-effects during anti-H. pylori treatment.

MATERIALS AND METHODS

Eligible articles were identified by searches of electronic databases. We included all randomized trials comparing lactoferrin supplementation to placebo or no treatment during anti-H. pylori regimens. Statistical analysis was performed with Review Manager 5.0.10. Subanalysis/Sensitivity analysis was also performed.

RESULTS

We identified nine randomized trials (n = 1343). Pooled H. pylori eradication rates were 86.57% (95% confidence interval (CI) = 83.99-89.15%) and 74.44% (95% CI = 71.14-77.74%) for patients with or without lactoferrin by intention-to-treat analysis, respectively, the odds ratio (OR) was 2.26 (95% CI = 1.70-3.00); the occurrence of total side-effects was 9.05% (95% CI = 6.83-11.27%) and 16.28% (95% CI = 13.43%-19.13%) for groups with or without lactoferrin, especially for nausea, the summary OR was 0.15 (95% CI = 0.04-0.54).

CONCLUSIONS

Our review suggests that supplementation with lactoferrin could be effective in increasing eradication rates of anti-H. pylori therapy, and could be considered helpful for patients with eradication failure. Furthermore, lactoferrin shows a positive impact on H. pylori therapy-related side-effects.

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.

Understanding Haemophilus parasuis infection in porcine spleen through a transcriptomics approach

Background

Haemophilus parasuis (HPS) is an important swine pathogen that causes Glässer's disease, which is characterized by fibrinous polyserositis, meningitis and arthritis. The molecular mechanisms that underlie the pathogenesis of the disease remain poorly understood, particularly the resistance of porcine immune system to HPS invasion. In this study, we investigated the global changes in gene expression in the spleen following HPS infection using the Affymetrix Porcine Genechip™.

Results

A total of 931 differentially expressed (DE) transcripts were identified in the porcine spleen 7 days after HPS infection; of these, 92 unique genes showed differential expression patterns based on analysis using BLASTX and Gene Ontology. The DE genes involved in the immune response included genes for inflammasomes (RETN, S100A8, S100A9, S100A12), adhesion molecules (CLDN3, CSPG2, CD44, LGALS8), transcription factors (ZBTB16, SLC39A14, CEBPD, CEBPB), acute-phase proteins and complement (SAA1, LTF, HP, C3), differentiation genes for epithelial cells and keratinocytes (TGM1, MS4A8B, CSTA), and genes related to antigen processing and presentation (HLA-B, HLA-DRB1). Further immunostimulation analyses indicated that mRNA levels of S100A8, S100A9, and S100A12 in porcine PK-15 cells increased within 48 h and were sustained after administration of lipopolysaccharide (LPS) and Poly(I:C) respectively. In addition, mapping of DE genes to porcine health traits QTL regions showed that 70 genes were distributed in 7 different known porcine QTL regions. Finally, 10 DE genes were validated by quantitative PCR.

Conclusion

Our findings demonstrate previously unrecognized changes in gene transcription that are associated with HPS infection in vivo, and many potential cascades identified in the study clearly merit further investigation. Our data provide new clues to the nature of the immune response in mammals, and we have identified candidate genes that are related to resistance to HPS.

Lactoferrin as a natural immune modulator

Lactoferrin, an iron-binding glycoprotein, is a cell-secreted mediator that bridges innate and adaptive immune function in mammals. It is a pleiotropic molecule that directly assists in the influence of presenting cells for the development of T-helper cell polarization. The aim of this review is to provide an overview of research regarding the role of lactoferrin in maintaining immune homeostasis, in particular as a mediator of immune responses to infectious assault, trauma and injury. These findings are critically relevant in the development of both prophylactic and therapeutic interventions in humans. Understanding these particular effects of lactoferrin will provide a logical framework for determining its role in health and disease.

Human recombinant lactoferrin acts synergistically with antimicrobials commonly used in neonatal practice against coagulase-negative staphylococci and Candida albicans causing neonatal sepsis

Neonatal sepsis causes significant mortality and morbidity. Coagulase-negative staphylococci (CoNS) and Candida frequently cause neonatal sepsis at >72 h of age. Lactoferrin, which is present in human milk, is a component of innate immunity and has broad-spectrum antimicrobial activity. The synergistic effects of lactoferrin with antibiotics against neonatal isolates have not been systematically evaluated. Here, eight clinical strains (seven neonatal) of CoNS and three strains (two neonatal) of Candida albicans were studied. MIC50 and MIC90 values of human recombinant lactoferrin (talactoferrin; TLF), vancomycin (VAN) and nafcillin (NAF) against CoNS, and of TLF, amphotericin B (AMB) and fluconazole (FLC) against C. albicans, were evaluated according to established guidelines. Antimicrobial combinations of TLF with NAF or VAN against CoNS, and TLF with AMB or FLC against C. albicans, were evaluated by a checkerboard method with serial twofold dilutions. Synergy was evaluated by the median effects principle, and combination indices and dose reduction indices were reported at 50, 75 and 90% inhibitory effect at several drug-dose ratios. It was found that TLF acted synergistically with NAF and VAN against CoNS, and with AMB and FLC against C. albicans, at multiple dose effects and drug-dose ratios with few exceptions. In synergistic combinations, drug reduction indices indicated a significant reduction in doses of antibiotics, which may be clinically relevant. Thus TLF acts synergistically with anti-staphylococcal and anti-Candida agents commonly used in neonatal practice and is a promising agent that needs to be evaluated in clinical studies.

Ascitic fluid lactoferrin for diagnosis of spontaneous bacterial peritonitis

BACKGROUND & AIMS

The diagnosis of spontaneous bacterial peritonitis (SBP) is based on a manual count of ascitic fluid polymorphonuclear cells (PMNs). This procedure is operator-dependent and lysis of PMNs during transport to the laboratory may lead to false-negative results. Furthermore, ascitic fluid culture is insensitive and leads to delays in diagnosis. The aim of this study was to assess the utility of ascitic fluid lactoferrin (AFLAC) for the diagnosis of SBP and to identify a cut-off level that can be used for future development of a rapid bedside test.

METHODS

A total of 218 consecutive ascites samples from 148 patients (1-8 samples per patient) with cirrhosis at 2 tertiary care medical centers were examined for PMN count, bedside culture, and lactoferrin concentration. AFLAC concentrations were determined using a polyclonal antibody-based enzyme-linked immunosorbent assay. An ascitic fluid PMN count of 250 cells/mL or greater with or without a positive culture was used for diagnosis of SBP.

RESULTS

Twenty-two (10.1%) samples fulfilled diagnostic criteria for SBP. Samples with SBP had a significantly higher lactoferrin concentration (median, 3744 ng/mL; 25th-75th percentiles [P25-P75], 788-9617) compared with non-SBP samples (median, 31 ng/mL; P25-P75, 12-67; P < .001). By using a cut-off level of 242 ng/mL, the sensitivity and specificity of the assay for diagnosis of SBP were 95.5% and 97%, respectively. The area under the receiver operating characteristic curve was 0.98.

CONCLUSIONS

AFLAC can serve as a sensitive and specific test for diagnosis of SBP. Qualitative bedside assays for the measurement of AFLAC can be developed easily and may serve as a rapid and reliable screening tool for SBP in patients with cirrhosis.

Recombinant human lactoferrin and iron transport across Caco-2 monolayers: effect of heat treatment on the binding to cells

Recombinant human lactoferrin (rhLF) from Aspergillus awamori bound to Caco-2 cell membranes in a saturable manner. The dissociation constant for the apo form was (Kd)=2.2 x 10(-7) M; however, the specific binding of the iron-saturated rhLF and of lactoferrin from human milk (hLF) was too low to calculate the binding parameters. Recombinant human lactoferrin subjected to heat treatment did not lose the ability to bind to cell membranes except at high temperature and long time treatments (85 and 89 degrees C for 40 min) for which there was a slight decrease in the binding. No significant differences have been found in the transport of iron bound to rhLF or to hLF across Caco-2 cell monolayers. Nevertheless, the amount of iron-saturated hLF transported across Caco-2 monolayers was significantly higher than that of rhLF. For both lactoferrins, the amount of intact protein in the lower chamber was about 4.5% of the total radioactivity transported, indicating the degradation of lactoferrin in the passage across Caco-2 cells.

Detection and characterization of amplified fragment length polymorphism markers for clinical mastitis in Canadian Holsteins

Mastitis is the most frequent, complex, and costly disease in dairy cattle. Genetic improvement of milk production traits has accompanied an increased susceptibility to mastitis. To determine genome-wide quantitative trait locus-linked markers for mastitis resistance, a total of 200 cows, comprising 100 top clinical mastitis- (CM) resistant and 100 top CM-susceptible cows, were screened by selective DNA pooling and amplified fragment length polymorphism (AFLP) technique. The AFLP analysis on resistant and susceptible pools using 89 selective primer combinations revealed 27 significant AFLP markers at a false discovery rate (FDR) of < 5%. The most promising AFLP marker was then selected for further characterization. Individual AFLP genotyping of the marker on all selected animals confirmed a significant difference. Sequence analysis detected a single nucleotide polymorphism (A<-->G) responsible for the AFLP polymorphism, which was named CGIL4. The PCR-RFLP analysis indicated that the frequency of allele A was significantly higher in the resistant group. The logistic regression analysis demonstrated that the marker was significantly associated with somatic cell score, CM residual values, and production traits. Radiation hybrid mapping assigned the marker to Bos taurus autosome 22. The present study provides promising markers for marker-assisted selection for CM resistance. Our results also demonstrated the capability of AFLP on selective DNA pools as a method for detection of genome regions containing quantitative trait loci.

Recombinant human lactoferrin expressed in glycoengineered Pichia pastoris: effect of terminal N-acetylneuraminic acid on in vitro secondary humoral immune response

Traditional production of therapeutic glycoproteins relies on mammalian cell culture technology. Glycoproteins produced by mammalian cells invariably display N-glycan heterogeneity resulting in a mixture of glycoforms the composition of which varies from production batch to production batch. However, extent and type of N-glycosylation has a profound impact on the therapeutic properties of many commercially relevant therapeutic proteins making control of N-glycosylation an emerging field of high importance. We have employed a combinatorial library approach to generate glycoengineered Pichia pastoris strains capable of displaying defined human-like N-linked glycans at high uniformity. The availability of these strains allows us to elucidate the relationship between specific N-linked glycans and the function of glycoproteins. The aim of this study was to utilize this novel technology platform and produce two human-like N-linked glycoforms of recombinant human lactoferrin (rhLF), sialylated and non-sialylated, and to evaluate the effects of terminal N-glycan structures on in vitro secondary humoral immune responses. Lactoferrin is considered an important first line defense protein involved in protection against various microbial infections. Here, it is established that glycoengineered P. pastoris strains are bioprocess compatible. Analytical protein and glycan data are presented to demonstrate the capability of glycoengineered P. pastoris to produce fully humanized, active and immunologically compatible rhLF. In addition, the biological activity of the rhLF glycoforms produced was tested in vitro revealing the importance of N-acetylneuraminic (sialic) acid as a terminal sugar in propagation of proper immune responses.

IsdA protects Staphylococcus aureus against the bactericidal protease activity of apolactoferrin

An important facet of the Staphylococcus aureus host-pathogen interaction is the ability of the invading bacterium to evade host innate defenses, particularly the cocktail of host antimicrobial peptides. In this work, we showed that IsdA, a surface protein of S. aureus which is required for nasal colonization, binds to lactoferrin, the most abundant antistaphylococcal polypeptide in human nasal secretions. The presence of IsdA on the surface of S. aureus confers resistance to killing by lactoferrin. In addition, the bactericidal activity of lactoferrin was inhibited by addition of phenylmethylsulfonyl fluoride, implicating the serine protease activity of lactoferrin in the killing of S. aureus. Recombinant IsdA was a competitive inhibitor of lactoferrin protease activity. Reciprocally, antibody reactive to IsdA enhanced killing of S. aureus. Thus, IsdA can protect S. aureus against lactoferrin and acts as a protease inhibitor.

Lactoferrin Isolation Using Monolithic Column Coupled with Spectrometric or Micro-Amperometric Detector

Lactoferrin is a multifunctional protein with antimicrobial activity and others tohealth beneficial properties. The main aim of this work was to propose easy to usetechnique for lactoferrin isolation from cow colostrum samples. Primarily we utilizedsodium dodecyl sulphate - polyacrylamide gel electrophoresis for isolation of lactoferrinfrom the real samples. Moreover we tested automated microfluidic Experionelectrophoresis system to isolate lactoferrin from the collostrum sample. The welldeveloped signal of lactoferrin was determined with detection limit (3 S/N) of 20 ng/ml. Inspite of the fact that Experion is faster than SDS-PAGE both separation techniques cannotbe used in routine analysis. Therefore we have tested third separation technique, ionexchange chromatography, using monolithic column coupled with UV-VIS detector (LCUV-VIS). We optimized wave length (280 nm), ionic strength of the elution solution (1.5M NaCl) and flow rate of the retention and elution solutions (0.25 ml/min and 0.75 ml/min.respectively). Under the optimal conditions the detection limit was estimated as 0.1 μg/mlof lactoferrin measured. Using LC-UV-VIS we determined that lactoferrin concentrationvaried from 0.5 g/l to 1.1 g/l in cow colostrums collected in the certain time interval up to 72 hours after birth. Further we focused on miniaturization of detection device. We testedamperometric detection at carbon electrode. The results encouraged us to attempt tominiaturise whole detection system and to test it on analysis of real samples of humanfaeces, because lactoferrin level in faeces is closely associated with the inflammations ofintestine mucous membrane. For the purpose of miniaturization we employed thetechnology of printed electrodes. The detection limit of lactoferrin was estimated as 10μg/ml measured by the screen-printed electrodes fabricated by us. The fabricatedelectrodes were compared with commercially available ones. It follows from the obtainedresults that the responses measured by commercial electrodes are app. ten times highercompared with those measured by the electrodes fabricated by us. This phenomenonrelates with smaller working electrode surface area of the electrodes fabricated by us(about 50 %) compared to the commercial ones. The screen-printed electrodes fabricatedby us were utilized for determination of lactoferrin faeces. Regarding to fact that sample offaeces was obtained from young and healthy man the amount of lactoferrin in sample wasunder the limit of detection of this method.

Iron fortification of infant formula

The purpose of this review is to examine the need for and appropriate level of Fe fortification of infant formula, and to assess any adverse effects of Fe fortification. The appropriate level of Fe fortification of infant formula has been established through studies of Fe absorption or erythrocyte incorporation of Fe, and through clinical trials of formulas with varying levels of Fe that were aimed at preventing the development of Fe deficiency in participating infants. In addition, the effects of varying levels of Fe fortification on the absorption of other minerals and trace elements, and on the incidence of infection and immune function have been studied, as has the effect of adding bovine lactoferrin to formula. Studies of Fe absorption have shown that increasing the level of Fe fortification in formula does not significantly increase the amount absorbed, and that the addition of bovine lactoferrin is unlikely to further increase absorption of Fe. Quite different recommendations for the level of Fe fortification of formula are made in the USA and in Europe. The higher level (12 mg/l) commonly used in the USA is not well supported by the evidence from clinical trials that suggest that lower levels (4 mg/l or less) may be adequate to prevent the development of Fe deficiency. Higher levels of Fe fortification may also interfere with the absorption of other minerals such as Cu and Se. Concerns about potential adverse effects of Fe fortification on immune function and susceptibility to infections have been disproved as have concerns about associated gastrointestinal symptomatology. There are no clearly demonstrated advantages in using ‘follow-on’ formula with high Fe content (up to 13 mg/l) instead of the standard UK formulas with Fe fortification in the range 4–7 mg/l after the age of 6 months, although they may provide an important ‘safety net’ for the prevention of Fe deficiency in communities with weaning diets low in Fe.

Expression and purification of goat lactoferrin from Pichia pastoris expression system

The recombinant goat lactoferrin (rGLF) was expressed in the methylotropic yeast Pichia pastoris using pGAPZalphaC vector, GAP as promoter, and Zeocin as the selective marker. After transformation of the GLF-pGAPZalphaC into Pichia pastoris X-33 expression host, the GLF-pGAPZalphaC vector was integrated into the GAP promoter locus of Pichia pastoris X-33 chromosome. The rGLF was expressed and secreted into the broth using alpha-factor preprosequence. SDS-PAGE and PAS staining analysis indicated that the rGLF could be purified to electrophoretic homogeneity by heparin-Sepharose 6 Fast Flow affinity chromatography and glycosylated by the expression host. The yield of purified rGLF was approximately 2.0 mg/L of culture broth. The N-terminal sequence was identical to the native goat lactoferrin (nGLF). The iron-binding behavior, papain-inhibiting property, and thermal stability of the purified rGLF were comparable to nGLF. This is the 1st report of intact goat lactoferrin expression using the P. pastoris system.

Influence of dietary components on development of the microbiota in single-stomached species

After birth, development of a normal microbial community occurs gradually, and is affected by factors such as the composition of the maternal gut microbiota, the environment, and the host genome. Diet also has a direct influence, both on composition and activity of this community. This influence begins with the milk, when specific components exert their growth-promoting effect on a beneficial microbiota, thereby suppressing potential pathogens. For example, breast-fed infants compared with formula-fed babies usually have a microbial community dominated by bifidobacteria. When solid food is introduced (weaning), dramatic changes in microbial composition occur, so pathogens can gain access to the disturbed gastrointestinal (GI) ecosystem. However, use of specific dietary components can alter the composition and activity of the microbiota positively. Of all dietary components, fermentable carbohydrates seem to be most promising in terms of promoting proliferation of beneficial bacterial species. Carbohydrate fermentation results in the production of SCFA which are known for their trophic and health-promoting effects. Fermentation of proteins, on the other hand, is often associated with growth of potential pathogens, and results in production of detrimental substances including NH3and amines. In terms of the GI microbiota, lipids are often associated with the antimicrobial activity of medium-chain fatty acids and their derivatives. The present review aims to provide deeper insights into the composition and development of the neonatal GI microbiota, how this microbiota can be influenced by certain dietary components, and how this might ultimately lead to improvements in host health.

Lactoferrin enhanced efficacy of the BCG vaccine to generate host protective responses against challenge with virulent Mycobacterium tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a disease with world wide consequences, affecting nearly a third of the world's population. The established vaccine for TB, an attenuated strain of Mycobacterium bovis Calmette Guerin (BCG), has existed since 1921. Lactoferrin, an iron-binding protein found in mucosal secretions and granules of neutrophils was hypothesized to be an ideal adjuvant to enhance the efficacy of the BCG vaccine, specifically because of previous reports of lactoferrin enhancement of IL-12 production from macrophages infected with BCG. Different vaccination protocols were investigated for generation of host protective responses against MTB infection using lactoferrin admixed to the BCG vaccine. Resulting effects demonstrate that BCG/lactoferrin increased host protection against MTB infection by decreasing organ bacterial load and reducing lung histopathology; significant reduction in tissue CFUs and pathology were observed post-challenge compared to those seen with BCG alone. Addition of lactoferrin to the vaccine led to reduced pathological damage upon subsequent infection with virulent MTB, with positive results demonstrated when admixed in oil-based vehicle (incomplete Freund's adjuvant, IFA) or when given with BCG in saline. The observed post-challenge results paralleled increasing production of IFN-gamma and IL-6, but only limited changes to proinflammatory mediators TNF-alpha or IL-1beta from BCG-stimulated splenocytes. Overall, these studies indicate that lactoferrin is a useful and effective adjuvant to improve efficacy of the BCG vaccine, with potential to reduce related tissue damage and pulmonary histopathology.

A calorimetric study of thermal denaturation of recombinant human lactoferrin from rice

Thermal denaturation of recombinant human lactoferrin from transgenic rice with different degrees of iron saturation has been studied by differential scanning calorimetry. The maximum temperature, enthalpy change, and activation energy of denaturation were higher when recombinant lactoferrin was more saturated with iron, indicating an increase in the stability of the protein structure. Maximum temperature and activation energy values for apo- and holo-lactoferrins were practically identical to those reported for the same forms of lactoferrin from human milk, which indicates a similar thermal stability. However, the value of enthalpy change for denaturation of the recombinant lactoferrin was 2.5-3-fold lower than that found for the human milk protein. This finding may reflect the influence that the different glycosylation pattern may have in the relationship between lactoferrin domains. Denaturation of recombinant lactoferrin in milk was compared with denaturation in phosphate buffer, and results indicated that the protein was more heat-sensitive when treated in milk than in buffer.

Differential modulation of human lactoferrin activity against both R5 and X4-HIV-1 adsorption on epithelial cells and dendritic cells by natural antibodies

Human lactoferrin (Lf) is an iron binding glycoprotein that is present in several mucosal secretions. Many biological functions have been ascribed to Lf. In the present study, we showed that Lf limited specifically adsorption of R5- and X4-HIV-1-free particles on endometrial epithelial HEC-1A cells, by inhibiting virus adsorption on heparan-sulfated proteoglycans. But, Lf did not interfere with both R5 and X4-HIV transcytosis. We showed also the efficacy of Lf in preventing R5 and X4-HIV capture by dendritic cells. Conversely, we demonstrated that Lf-reacting natural Abs (NAbs) present within i.v. Ig-enhanced HIV attachment on dendritic cells by forming HIV-Lf-NAbs. HIV particles were able to directly interact with Lf following its interaction with NAbs. We also found Lf-reacting natural Abs within cervicovaginal secretions, suggesting the existence of Lf-NAbs complexes in women genital tract in vivo. In conclusion, this study highlights Lf as a potent microbicides and reports new function for NAbs within the genital compartment that may compartment that may abolish the inhibitory activity of microbicide compounds. Thus, we proposed a model in which Lf would appear as a double-edged sword that could have beneficial or detrimental effects depending on both cellular and molecular environments. This study highlights the use of Lf derivates as microbicide candidates to limit such interferences.

Binding interactions of pefloxacin mesylate with bovine lactoferrin and human serum albumin

The binding of pefloxacin mesylate (PFLX) to bovine lactoferrin (BLf) and human serum albumin (HSA) in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.

Pedimune in recurrent respiratory infection and diarrhoea--the Indian experience--the pride study

OBJECTIVE

To evaluate the efficacy and tolerability of bovine colostrum in preventing recurrent episodes of upper respiratory tract infections and diarrhoea in children

METHODS

605 children (1-8 yrs) having recurrent episodes of upper respiratory tract infections or diarrhea received Bovine Colostrum (Pedimune) for 12 weeks. Total no of episodes of recurrent infections, hospitalization rate, overall well being and adverse events were assessed at every 4 weeks.

RESULTS

Episodes of URTI and diarrhoea reduced significantly by 91.19 % and 86.60% at the end of therapy respectively. High to average improvement in overall well-being in 96 % of the patients were found by pediatrician while overall well-being stated by the patient/care taker was very good to good in 90.56 % of the patients.

CONCLUSION

Bovine colostrum was highly effective in the prophylactic treatment of recurrent URTIs and diarrhea in reducing not only the episodes but also the hospitalization due to them.

Sub-chronic (13-week) oral toxicity study in rats with recombinant human lactoferrin produced in the milk of transgenic cows

The oral toxicity of recombinant human lactoferrin (rhLF) produced in the milk of transgenic cows was investigated in Wistar rats by daily administration via oral gavage for 13 consecutive weeks, 7 days per week. The study used four groups of 20 rats/sex/dose. The control group received physiological saline and the three test groups received daily doses of 200, 600 and 2000 mg of rhLF per kg body weight. Clinical observations, growth, food consumption, food conversion efficiency, water consumption, neurobehavioural testing, ophthalmoscopy, haematology, clinical chemistry, renal concentration test, urinalysis, organ weights and gross examination at necropsy and microscopic examination of various organs and tissues were used as criteria for detecting the effects of treatment. Overall, no treatment-related, toxicologically significant changes were observed. The few findings that may be related to the treatment (lower cholesterol in high-dose females, lower urinary pH in high-dose males and females and very slightly higher kidney weight in high-dose females) were considered of no toxicological significance. Based on the absence of treatment-related, toxicologically relevant changes, the no-observed-adverse-effect level (NOAEL) was considered to be at least 2000 mg/kg body weight/day.

Lactoferrin (Lf): Retinoid interactions in the mammary glands of transgenic mice overexpressing human Lf

Induction of protein expression in a tissue-specific manner by gene transfer over-expression techniques has been one means to define the function of a protein in a biological paradigm. Studies with retinoid reporter constructs transfected in mammary cell lines suggests that lactoferrin (Lf) affects retinoid signaling pathways and alters apoptosis. We tested the effects and interactions of over-expressed mammary-specific human lactoferrin (hLf) and dietary retinol palmitate on lactation and mammary gland development in mice. Increased retinol palmitate in the diet increased daily retinol equivalents (RE) to 2.6-fold over the normal mouse control diet. Transgene (Tg) expression in the dam fed control diet depressed pup weight gain. Severe depression of pup weight gain was observed when homozygote TgTg dams were fed the RE diet. Normal weight gain was restored when pups were placed with a wild type dam fed the RE diet; conversely, normal growing pups from the wild type dams showed declining weight gains when fostered to the TgTg RE-fed dams. Northern analysis of mammary tissue extracts showed a reduction in WAP and an increase in IGFBP-3 mRNA that was associated with the presence of the transgene. Histological evaluation of 3 days lactating mammary tissue showed mammary epithelial cells from TgTg animals contained excessive secretory products, suggesting a block in cellular secretion mechanisms. In addition, the mammary cells displayed a cellular apical membrane puckering that extended into the alveoli lumens. These studies demonstrate an in vivo interaction of Tg-hLf expression and dietary retinoids in mouse mammary glands. While normal mammary gland physiology may not be representative by these experiments because high Lf concentrations during early lactation are abnormal, the demonstrated biological interaction suggests that typical periods of high Lf concentrations may have impact upon developing and involuting mammary glands.

MNN5 encodes an iron-regulated alpha-1,2-mannosyltransferase important for protein glycosylation, cell wall integrity, morphogenesis, and virulence in Candida albicans

The cell walls of microbial pathogens mediate physical interactions with host cells and hence play a key role in infection. Mannosyltransferases have been shown to determine the cell wall properties and virulence of the pathogenic fungus Candida albicans. We previously identified a C. albicans alpha-1,2-mannosyltransferase, Mnn5, for its novel ability to enhance iron usage in Saccharomyces cerevisiae. Here we have studied the enzymatic properties of purified Mnn5 and characterized its function in its natural host. Mnn5 catalyzes the transfer of mannose to both alpha-1,2- and alpha-1,6-mannobiose, and this activity requires Mn2+ as a cofactor and is regulated by the Fe2+ concentration. An mnn5Delta mutant showed a lowered ability to extend O-linked, and possibly also N-linked, mannans, hypersensitivity to cell wall-damaging agents, and a reduction of cell wall mannosylphosphate content, phenotypes typical of many fungal mannosyltransferase mutants. The mnn5Delta mutant also exhibited some unique defects, such as impaired hyphal growth on solid media and attenuated virulence in mice. An unanticipated phenotype was the mnn5Delta mutant's resistance to killing by the iron-chelating protein lactoferrin, rendering it the first protein found that mediates lactoferrin killing of C. albicans. In summary, MNN5 deletion impairs a wide range of cellular events, most likely due to its broad substrate specificity. Of particular interest was the observed role of iron in regulating the enzymatic activity, suggesting an underlying relationship between Mnn5 activity and cellular iron homeostasis.

In vivo expression of the antimicrobial defensin and lactoferrin proteins allowed by the strategic insertion of introns adequately spliced

A major limitation of conventional shuttle expression system, when cloning a bactericidal gene, is the basal expression level in bacteria, which is lethal. Although the expression level is low, the bactericidal feature inherent to the molecule leads to subsequent failure to recover intact transformants when the related gene is cloned into a conventional expression vector. Contrary to popular belief, the human cytomegalovirus immediate-early region 1 promoter (CMV), which is to date one of the most powerful promoters for eukaryotic expression, is active in bacteria. In this study, bactericidal genes were cloned into a conventional shuttle eukaryote expression vector harbouring the CMV promoter, but were interrupted with a sequence independent splicing element (SISE), thus inhibiting lethal gene expression in bacteria. The insertion strategy of the intron uses a universal restriction site-free cloning approach, which has been developed to insert a DNA fragment into a specific location of a gene, through a PCR-based cloning technique. We have found that one intervening sequence, which derives from an adenovirus, can be spliced in a mammalian system without respect to its location, thus the bactericidal protein is synthesized only when transfected into mammalian cells. Therein, lactoferrin and defensin proteins were produced in vivo without the necessity of complex expression systems. By introducing the adeno SISE within the coding sequence of the bactericidal genes, such genes can be easily synthesized in vitro through cloning into bacteria and still are able to express biologically active proteins when introduced into mammalian cells.

Bovine lactoferrin for Helicobacter pylori eradication: an open, randomized, multicentre study

BACKGROUND

Cure rates for eradication of Helicobacter pylori appear to be decreasing, thus more effective therapies must be identified.

AIM

To evaluate the efficacy of bovine lactoferrin in the treatment of H. pylori infection.

METHODS

In a multicentered prospective study, 402 (mean age 52.4, range 19-84 years) H. pylori-positive patients were assigned to one of three regimens: group A - esomeprazole 20 mg b.d., clarithromycin 500 mg b.d. and tinidazole 500 mg b.d. for 7 days; group B - lactoferrin 200 mg b.d. for 7 days followed by the same schedule of group A; group C - esomeprazole 20 mg b.d., clarithromycin 500 mg b.d. and tinidazole 500 mg b.d. plus lactoferrin 200 mg b.d. for 7 days.

RESULTS

Of the 402 patients, 389 completed the study. Six patients were discontinued due to side effects, one patient in group B died and six patients were lost to follow up. The eradication rate (intention-to-treat analysis) was 77% in group A (105/136), 73% in group B (97/132) and 90% in group C (120/134) (chi(2)-test P < 0.01). The incidence of side effects was 9.5% in group A, 9% in group B and 8.2% in group C (chi(2)-test P = 0.1).

CONCLUSION

This study demonstrates that bovine lactoferrin is an effective adjuvant to 7-day triple therapy for eradication of H. pylori infection.

Developmental gene expression of lactoferrin and effect of dietary iron on gene regulation of lactoferrin in mouse mammary gland

This study evaluated the developmental gene expression of lactoferrin (LF) and the effect of supplementary iron on gene expression of LF in the mammary gland of mice using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. In experiment 1, a total of 12 female mice were used to determine the effect of different lactating stages on mRNA expression of LF. The Institute of Cancer Research mice were divided into 4 groups; each group of 3 mice was tested on d 1, 9, 17, and 25 of lactation. In experiment 2, 6 groups of mice (total of 24 female mice at d 12 after mating) were fed purified diets (without iron or supplement iron) and were assigned to 2 treatments (control and treatment). The experimental feeding period lasted 35 d. During the feeding experiment, 6 mice (3 animals in each group) were chosen on d 1, 9, 17, and 25 of lactation to determine the effect of iron on LF mRNA expression of mice at different stages of lactation. The results of experiment 1 showed that LF mRNA had strong expression on d 1 of lactation, decreased gradually on d 9 and 17 of lactation, and then increased again markedly on d 25 of lactation. These results imply that the expression of LF in the mammary gland at different lactating stages is consistent with the changes in LF concentrations in milk. Iron significantly increased LF mRNA expression on d 1 and 25 of lactation. Iron did not statistically increase LF gene expression on d 9 and 17 of lactation. These findings raised the possibility that iron supplementation may play a role in regulation of LF levels in vivo.

Developmental gene expression of lactoferrin in duodenum and effect of weaning age on gene expression of lactoferrin in piglets

Two experiments were conducted to evaluate duodenal gene expression of lactoferrin and effect of weaning age on mRNA expression of lactoferrin in piglets using semi-quantitative RT-PCR analysis. In experiment 1, a total of 15 female Duroc x Landrace x Yorkshire piglets of five groups, each group pigs at 1, 14, 28, 42 and 56 days of age were used to determine developmental gene expression of lactoferrin in duodenum. In experiment 2, a total of 18 female neonatal piglets were divided into three groups, which were weaned at 21, 28 and 35 days of age respectively. In each group, three piglets' duodena were sampled at 21, 28 and 35 days of age and the other three piglets' duodena were sampled 7 days after weaning in each group. The samples were collected for detecting the effect of weaning age on lactoferrin mRNA expression of piglets. The results show that lactoferrin mRNA levels decreased steadily in postnatal day 1-56. But only from day 28-42 (14 days after weaned), the levels of lactoferrin gene expression were decreased markedly (p < 0.05), and the difference of lactoferrin mRNA levels at other stages was not significant. This result suggested that weaning had an effect on gene expression of lactoferrin. The results of experiment 2 showed that when the piglets were weaned at 21-28 and 35 days of age respectively, the expression levels of lactoferrin were decreased by 77%, 53% and 59% at the seventh day after weaning. Our results showed that weaning significantly decreased lactoferrin mRNA expression of piglets.

Pharmacokinetics and brain uptake of lactoferrin in rats

Lactoferrin (Lf) is an iron-binding glycoprotein belonging to the transferrin (Tf) family. Lf was reported to cross the blood brain barrier (BBB) via receptor-mediated transcytosis in an in vitro model of the BBB. In the present study, we compared the in vivo brain uptake of Lf with that of OX26, an anti-Tf receptor antibody, and Tf. These three proteins were radiolabeled with 125I and administered to rats by i.v. injection. We found that Lf was more rapidly eliminated from the blood compared with OX26 and Tf (The half-life of Lf was approximately 8 and 6 times shorter than that of OX26 and Tf, respectively; the area under the blood concentration-time curve of Lf was approximately 15 and 17 times smaller than that of OX26 and Tf, respectively), and mainly accumulated in the liver, spleen, and kidney. Markedly high brain uptake was observed for Lf relative to Tf and OX26. Lf might be useful as a ligand for facilitating drug delivery into the brain.

Fluorometric Study on the Interaction between Lomefloxacin and Bovine Lactoferrin

The binding of lomefloxacin to bovine lactoferrin (BLf) in a dilute aqueous solution was studied using fluorescence spectra. The binding constant (K) and the number of binding sites (n) were obtained by a fluorescence quenching method. The binding distance (r) and energy-transfer efficiency (E) between lomefloxacin and bovine lactoferrin were also obtained according to the mechanism of Foörster-type dipole-dipole nonradiative energy-transfer. The effect of lomefloxacin on the conformation of bovine lactoferrin was also analyzed by synchronous fluorescence spectroscopy. The interaction between lomefloxacin and bovine lactoferrin is strong. Lomefloxacin can affect the conformation of bovine lactoferrin to some degree.

Effect of human milk fortifiers on bacterial growth in human milk

BACKGROUND

As a component in human milk fortifiers (HMF), iron may equilibrate with human milk for as long as 24 hours, bind important bacteriostatic proteins, and potentially affect the host defense properties of human milk.

OBJECTIVE

We compared bacterial growth in human milk prepared with each of two HMF differing in their content of iron.

STUDY DESIGN

Samples of human milk obtained from mothers of premature infants were divided and mixed with one of two HMF and maintained at refrigerator temperature. Refrigerated milk samples were removed at 0, 24, and 72 hours for determination of total bacterial colony counts (TBCC).

RESULTS

TBCC did not differ between groups but declined from 0 to 72 hours, p<0.001.

CONCLUSION

These data suggest that differences in iron content, or other nutrients in HMF, do not affect bacterial growth in human milk. Storage of fortified human milk at refrigerator temperature for 72 hours results in decreased bacterial growth. As a component in human milk fortifiers (HMF), iron may equilibrate with human milk for as long as 24 hours, bind important bacteriostatic proteins, and potentially affect the host defense properties of human milk. We compared bacterial growth in human milk prepared with each of two HMF differing in their content of iron. Samples of human milk obtained from mothers of premature infants were divided and mixed with one of two HMF and maintained at refrigerator temperature. Refrigerated milk samples were removed at 0, 24, and 72 hours for determination of total bacterial colony counts (TBCC).

The protein structure of recombinant human lactoferrin produced in the milk of transgenic cows closely matches the structure of human milk-derived lactoferrin

Human lactoferrin (hLF) is an iron-binding glycoprotein involved in the host defence against infection and excessive inflammation. As the availability of (human milk-derived) natural hLF is limited, alternative means of production of this biopharmaceutical are extensively researched. Here we report the crystal structure of recombinant hLF (rhLF) expressed in the milk of transgenic cows at a resolution of 2.4 A. To our knowledge, the first reported structure of a recombinant protein produced in milk of transgenic livestock. Even though rhLF contains oligomannose- and hybrid-type N-linked glycans next to complex-type glycans, which are the only glycans found on natural hLF, the structures are identical within the experimental error (r.m.s. deviation of only 0.28 A for the main-chain atoms). Of the differences in polymorphic amino acids between the natural and rhLF variant used, only the side-chain of Asp561 could be modeled into the rhLF electron density map. Taken together, the results confirm the structural integrity of the rhLF variant used in this study. It also confirms the validity of the transgenic cow mammary gland as a vehicle to produce recombinant human proteins.

Enhanced clearance of Escherichia coli and Staphylococcus aureus in mice treated with cyclophosphamide and lactoferrin

Previous studies on cyclophosphamide (CP)-immunocompromised mice showed accelerated reconstitution of immune system function following oral treatment with lactoferrin (LF). The aim of this investigation was to evaluate the ability of mice, treated with a sublethal dose of CP and given LF, to combat bacterial infections. Mice were injected with a single, intraperitoneal dose of CP (350 mg/kg body weight). One group of CP-treated mice was also given LF in drinking water (0.5% solution) for 14 days. Untreated and LF-treated mice served as controls. On day 15 following CP administration, mice were infected intravenously with 10(8) Escherichia coli or 5 x 10(7) Staphylococcus aureus. Twenty-four hours later, the number of colony-forming units (CFU) in spleens and livers were determined. Phenotypic analysis of blood leukocytes was determined, as well as the ability of splenic and peritoneal cells to produce IL-6 spontaneously and in the presence of lipopolysaccharide (LPS). Treatment with CP, or with CP and LF, led to profound reduction of E. coli CFU in the liver and the spleen; treatment with LF alone had significant inhibitory effects on organ enumerated CFU. S. aureus CFUs were also significantly reduced in spleens of mice treated with CP or CP/LF and, to a lesser degree, after LF alone. These effects were also significantly reduced in the livers. Analysis of blood cellular phenotype revealed total number of peripheral leukocytes was lower in the CP-treated group (52.6%) but not significantly different from control values in CP/LF and LF-treated groups (90.7% and 104.6%, respectively). Conversely, percentage of blood neutrophils was markedly elevated in CP and CP/LF groups--62% and 42.5% vs. 18.4% in controls. These findings were accompanied by production of IL-6 by splenic and peritoneal cells which was significantly increased in CP- and CP/LF-treated groups. It was concluded that the increased clearance of bacteria in the organs of mice treated with CP and CP/LF may result from a rise in the number of neutrophils infiltrating the organs and contributing to accelerated clearance of bacteria. The study also suggests that the ability of cells from CP- and CP/LF-treated mice to produce significantly more IL-6 may also contribute to increased resistance to infections. Lastly, together with our previous data, this study indicates that LF used to reconstitute the antigen-specific immune response in CP-treated mice does not impair their resistance to infection.

Effects of lactoferrin on non-specific immune responses of gilthead seabream (Sparus auratus L.)

The main innate cellular immune responses of gilthead seabream (Sparus auratus L.) leucocytes were evaluated after in vitro incubation with human lactoferrin (Lf). Isolated head-kidney leucocytes were incubated with 0 (control) to 1 mg ml(-1) Lf-supplemented culture medium for 30, 120, 240 or 360 min and assayed for viability, peroxidase content, and respiratory burst, phagocytic and cytotoxic activities. Only respiratory burst activity was found to increase when using the highest Lf concentration (1 mg ml(-1)) and long incubation times (more than 120 min). Seabream were fed Lf-supplemented diets (0, control, 50, 100 or 200 mg kg(-1) diet). After 1 or 2 weeks of administration the leucocyte peroxidase content, respiratory burst, phagocytic and cytotoxic activities as a measure of cellular immune responses, as well as serum peroxidase and complement activity as a measure of humoral immune responses were evaluated. The results showed that Lf feeding at 100 mg kg(-1) diet for 1 week enhanced the cellular innate immune responses although only the cytotoxic activity did so significantly. The humoral immune response was not influenced by Lf feeding. In conclusion, Lf seems to affect innate immune cellular activity, mainly respiratory burst and natural cytotoxic activity. The possible use of Lf as an immunostimulant for farmed gilthead seabream is discussed.