Bacteriostatic activity of human lactoferrin against Staphylococcus aureus is a function of its iron-binding properties and is not influenced by antibiotic resistance

The Antimicrobial Activity of Human Defensins at Physiological Non-Permeabilizing Concentrations Is Caused by the Inhibition of the Plasma Membrane H+-ATPases

Human defensins are cysteine-rich peptides (Cys-rich peptides) of the innate immune system. Defensins contain an ancestral structural motif (i.e., γ-core motif) associated with the antimicrobial activity of natural Cys-rich peptides. In this study, low concentrations of human α- and β-defensins showed microbicidal activity that was not associated with cell membrane permeabilization. The cell death pathway was similar to that previously described for human lactoferrin, also an immunoprotein containing a γ-core motif. The common features were (1) cell death not related to plasma membrane (PM) disruption, (2) the inhibition of microbicidal activity via extracellular potassium, (3) the influence of cellular respiration on microbicidal activity, and (4) the influence of intracellular pH on bactericidal activity. In addition, in yeast, we also observed (1) partial K+-efflux mediated via Tok1p K+-channels, (2) the essential role of mitochondrial ATP synthase in cell death, (3) the increment of intracellular ATP, (4) plasma membrane depolarization, and (5) the inhibition of external acidification mediated via PM Pma1p H+-ATPase. Similar features were also observed with BM2, an antifungal peptide that inhibits Pma1p H+-ATPase, showing that the above coincident characteristics were a consequence of PM H+-ATPase inhibition. These findings suggest, for the first time, that human defensins inhibit PM H+-ATPases at physiological concentrations, and that the subsequent cytosolic acidification is responsible for the in vitro microbicidal activity. This mechanism of action is shared with human lactoferrin and probably other antimicrobial peptides containing γ-core motifs.

Engineered Extracellular Vesicles Driven by Erythrocytes Ameliorate Bacterial Sepsis by Iron Recycling, Toxin Clearing and Inflammation Regulation

Sepsis poses a significant challenge in clinical management. Effective strategies targeting iron restriction, toxin neutralization, and inflammation regulation are crucial in combating sepsis. However, a comprehensive approach simultaneously targeting these multiple processes has not been established. Here, an engineered apoptotic extracellular vesicles (apoEVs) derived from macrophages is developed and their potential as multifunctional agents for sepsis treatment is investigated. The extensive macrophage apoptosis in a Staphylococcus aureus-induced sepsis model is discovered, unexpectedly revealing a protective role for the host. Mechanistically, the protective effects are mediated by apoptotic macrophage-released apoEVs, which bound iron-containing proteins and neutralized α-toxin through interaction with membrane receptors (transferrin receptor and A disintegrin and metalloprotease 10). To further enhance therapeutic efficiency, apoEVs are engineered by incorporating mesoporous silica nanoparticles preloaded with anti-inflammatory agents (microRNA-146a). These engineered apoEVs can capture iron and neutralize α-toxin with their natural membrane while also regulating inflammation by releasing microRNA-146a in phagocytes. Moreover, to exploit the microcosmic movement and rotation capabilities, erythrocytes are utilized to drive the engineered apoEVs. The erythrocytes-driven engineered apoEVs demonstrate a high capacity for toxin and iron capture, ultimately providing protection against sepsis associated with high iron-loaded conditions. The findings establish a multifunctional agent that combines natural and engineered antibacterial strategies.

The chronic wound milieu changes essential oils' antibiofilm activity-an in vitro and larval model study

Essential Oils (EOs) are currently being researched as potential antibiofilm agents to combat infections related to chronic wound biofilms. As documented in the literature, EOs' in vitro antibacterial properties are often assessed using standard microbiological media and conditions that do not accurately reflect the actual environment of a chronic wound. To address this issue, In vitro Wound Milieu (IVWM) medium, which closely resembles the environment of a chronic wound, was applied for culturing S. aureus biofilms (n = 12) in this research. Biofilms cultivated in the standard Tryptic Soy Broth (TSB) medium served as a control for the experiment. Key biofilm features were analyzed and compared. Subsequently, staphylococci were exposed to the activity of thyme or rosemary EOs (T-EO and R-EO, respectively). As proof of concept, the cytotoxicity of T-EO and its antimicrobial in vivo activity were assessed using a G. mellonella larvae model. Key features of biofilm-forming cells were lower in the IVWM than in the TSB medium: biomass (up to 8 times), metabolic activity (up to 9 times), cell number (up to 100 times), and the live/dead cells ratio. Conversely, biofilm thickness was higher (up to 25%) in IVWM. These differences translated into varied responses of the biofilms to EOs exposure. The application of T-EO led to a greater reduction (up to 2 times) in 67% of biofilm-forming strains in IVWM compared to the TSB medium. Conversely, exposure to R-EO resulted in a higher reduction (up to 2.6 times) of 83% of biofilm-forming strains in TSB than in IVWM. The application of T-EO was not only non-toxic to G. mellonella larvae but also increased the survival of larvae infected with staphylococci (from 48 to 85%). Our findings suggest that EOs not only show promise as agents for treating biofilm-related wound infections but also that providing conditions reflecting the specific niche of the human body is of paramount importance in influencing the results obtained. However, before clinical application, challenges related to the methods of assessing their activity, microbial intra-species variability, and different levels of activity of various EOs should be analyzed and standardized.

Lactoferrin and Lysozyme Inhibit the Proteolytic Activity and Cytopathic Effect of Naegleria fowleri Enzymes

Naegleria fowleri is a ubiquitous free-living amoeba that causes primary amoebic meningoencephalitis. As a part of the innate immune response at the mucosal level, the proteins lactoferrin (Lf) and lysozyme (Lz) are secreted and eliminate various microorganisms. We demonstrate that N. fowleri survives the individual and combined effects of bovine milk Lf (bLf) and chicken egg Lz (cLz). Moreover, amoebic proliferation was not altered, even at 24 h of co-incubation with each protein. Trophozoites' ultrastructure was evaluated using transmission electron microscopy, and these proteins did not significantly alter their organelles and cytoplasmic membranes. Protease analysis using gelatin-zymograms showed that secreted proteases of N. fowleri were differentially modulated by bLf and cLz at 3, 6, 12, and 24 h. The bLf and cLz combination resulted in the inhibition of N. fowleri-secreted proteases. Additionally, the use of protease inhibitors on bLf-zymograms demonstrated that secreted cysteine proteases participate in the degradation of bLf. Nevertheless, the co-incubation of trophozoites with bLf and/or cLz reduced the cytopathic effect on the MDCK cell line. Our study suggests that bLf and cLz, alone or together, inhibited secreted proteases and reduced the cytopathic effect produced by N. fowleri; however, they do not affect the viability and proliferation of the trophozoites.

Understanding Staphylococcus aureus internalisation and induction of antimicrobial tolerance

INTRODUCTION

Staphylococcus aureus, a human commensal, is also one of the most common and serious pathogens for humans. In recent years, its capacity to survive and replicate in phagocytic and non-phagocytic cells has been largely demonstrated. In these intracellular niches, bacteria are shielded from the immune response and antibiotics, turning host cells into long-term infectious reservoirs. Moreover, neutrophils carry intracellular bacteria in the bloodstream, leading to systemic spreading of the disease. Despite the serious threat posed by intracellular S. aureus to human health, the molecular mechanisms behind its intracellular survival and subsequent antibiotic treatment failure remain elusive.

AREA COVERED

We give an overview of the killing mechanisms of phagocytes and of the impressive arsenal of virulence factors, toxins and stress responses deployed by S. aureus as a response. We then discuss the different barriers to antibiotic activity in this intracellular niche and finally describe innovative strategies to target intracellular persisting reservoirs.

EXPERT OPINION

Intracellular niches represent a challenge in terms of diagnostic and treatment. Further research using ad-hoc in-vivo models and single cell approaches are needed to better understand the molecular mechanisms underlying intracellular survival and tolerance to antibiotics in order to identify strategies to eliminate these persistent bacteria.

Acanthamoeba castellanii Genotype T4: Inhibition of Proteases Activity and Cytopathic Effect by Bovine Apo-Lactoferrin

Acanthamoeba castellanii genotype T4 is a clinically significant free-living amoeba that causes granulomatous amoebic encephalitis and amoebic keratitis in human beings. During the initial stages of infection, trophozoites interact with various host immune responses, such as lactoferrin (Lf), in the corneal epithelium, nasal mucosa, and blood. Lf plays an important role in the elimination of pathogenic microorganisms, and evasion of the innate immune response is crucial in the colonization process. In this study, we describe the resistance of A. castellanii to the microbicidal effect of bovine apo-lactoferrin (apo-bLf) at different concentrations (25, 50, 100, and 500 µM). Acanthamoeba castellanii trophozoites incubated with apo-bLf at 500 µM for 12 h maintained 98% viability. Interestingly, despite this lack of effect on viability, our results showed that the apo-bLf inhibited the cytopathic effect of A. castellanii in MDCK cells culture, and analysis of amoebic proteases by zymography showed significant inhibition of cysteine and serine proteases by interaction with the apo-bLf. From these results, we conclude that bovine apo-Lf influences the activity of A. castellanii secretion proteases, which in turn decreases amoebic cytopathic activity.

Potential of Lactoferrin in the Treatment of Lung Diseases

Lactoferrin (LF) is a multifunctional iron-binding glycoprotein that exhibits a variety of properties, such as immunomodulatory, anti-inflammatory, antimicrobial, and anticancer, that can be used to treat numerous diseases. Lung diseases continue to be the leading cause of death and disability worldwide. Many of the therapies currently used to treat these diseases have limited efficacy or are associated with side effects. Therefore, there is a constant pursuit for new drugs and therapies, and LF is frequently considered a therapeutic agent and/or adjunct to drug-based therapies for the treatment of lung diseases. This article focuses on a review of the existing and most up-to-date literature on the contribution of the beneficial effects of LF on the treatment of lung diseases, including asthma, viral infections, cystic fibrosis, or lung cancer, among others. Although in vitro and in vivo studies indicate significant potency of LF in the treatment of the listed diseases, only in the case of respiratory tract infections do human studies seem to confirm them by demonstrating the effectiveness of LF in reducing episodes of illness and shortening the recovery period. For lung cancer, COVID-19 and sepsis, the reports are conflicting, and for other diseases, there is a paucity of human studies conclusively confirming the beneficial effects of LF.

Mechanisms affecting the gut of preterm infants in enteral feeding trials: a nested cohort within a randomised controlled trial of lactoferrin

OBJECTIVE

To determine the impact of supplemental bovine lactoferrin on the gut microbiome and metabolome of preterm infants.

DESIGN

Cohort study nested within a randomised controlled trial (RCT). Infants across different trial arms were matched on several clinical variables. Bacteria and metabolite compositions of longitudinal stool and urine samples were analysed to investigate the impact of lactoferrin supplementation.

SETTING

Thirteen UK hospitals participating in a RCT of lactoferrin.

PATIENTS

479 infants born <32 weeks' gestation between June 2016 and September 2017.

RESULTS

10 990 stool and 22 341 urine samples were collected. Analyses of gut microbiome (1304 stools, 201 infants), metabolites (171 stools, 83 infants; 225 urines, 90 infants) and volatile organic compounds (314 stools, 117 infants) were performed. Gut microbiome Shannon diversity at 34 weeks corrected age was not significantly different between infants in the lactoferrin (mean=1.24) or placebo (mean=1.06) groups (p=0.11). Lactoferrin receipt explained less than 1% variance in microbiome compositions between groups. Metabolomic analysis identified six discriminative features between trial groups. Hospital site (16%) and postnatal age (6%) explained the greatest variation in microbiome composition.

CONCLUSIONS

This multiomic study identified minimal impacts of lactoferrin but much larger impacts of hospital site and postnatal age. This may be due to the specific lactoferrin product used, but more likely supports the findings of the RCT in which this study was nested, which showed no impact of lactoferrin on reducing rates of sepsis. Multisite mechanistic studies nested within RCTs are feasible and help inform trial interpretation and future trial design.

Optimal dose of lactoferrin reduces the resilience of in vitro Staphylococcus aureus colonies

The rise in antibiotic resistance has stimulated research into adjuvants that can improve the efficacy of broad-spectrum antibiotics. Lactoferrin is a candidate adjuvant; it is a multifunctional iron-binding protein with antimicrobial properties. It is known to show dose-dependent antimicrobial activity against Staphylococcus aureus through iron sequestration and repression of β-lactamase expression. However, S. aureus can extract iron from lactoferrin through siderophores for their growth, which confounds the resolution of lactoferrin's method of action. We measured the minimum inhibitory concentration (MIC) for a range of lactoferrin/ β-lactam antibiotic dose combinations and observed that at low doses (< 0.39 μM), lactoferrin contributes to increased S. aureus growth, but at higher doses (> 6.25 μM), iron-depleted native lactoferrin reduced bacterial growth and reduced the MIC of the β-lactam-antibiotic cefazolin. This differential behaviour points to a bacterial population response to the lactoferrin/ β-lactam dose combination. Here, with the aid of a mathematical model, we show that lactoferrin stratifies the bacterial population, and the resulting population heterogeneity is at the basis of the dose dependent response seen. Further, lactoferrin disables a sub-population from β-lactam-induced production of β-lactamase, which when sufficiently large reduces the population's ability to recover after being treated by an antibiotic. Our analysis shows that an optimal dose of lactoferrin acts as a suitable adjuvant to eliminate S. aureus colonies using β-lactams, but sub-inhibitory doses of lactoferrin reduces the efficacy of β-lactams.

Milieu matters: An in vitro wound milieu to recapitulate key features of, and probe new insights into, mixed-species bacterial biofilms

Bacterial biofilms are a major cause of delayed wound healing. Consequently, the study of wound biofilms, particularly in host-relevant conditions, has gained importance. Most in vitro studies employ refined laboratory media to study biofilms, representing conditions that are not relevant to the infection state. To mimic the wound milieu, in vitro biofilm studies often incorporate serum or plasma in growth conditions, or employ clot or matrix-based biofilm models. While incorporating serum or plasma alone is a minimalistic approach, the more complex in vitro wound models are technically demanding, and poorly compatible with standard biofilm assays. Based on previous reports of clinical wound fluid composition, we have developed an in vitro wound milieu (IVWM) that includes, in addition to serum (to recapitulate wound fluid), matrix elements and biochemical factors. With Luria-Bertani broth and Fetal Bovine Serum (FBS) for comparison, the IVWM was used to study planktonic growth, biofilm features, and interspecies interactions, of common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. We demonstrate that the IVWM recapitulates widely reported in vivo biofilm features such as biomass formation, metabolic activity, increased antibiotic tolerance, 3D structure, and interspecies interactions for monospecies and mixed-species biofilms. Further, the IVWM is simple to formulate, uses laboratory-grade components, and is compatible with standard biofilm assays. Given this, it holds potential as a tractable approach to study wound biofilms under host-relevant conditions.

Characterisation of Lactoferrin Isolated from Acid Whey Using Pilot-Scale Monolithic Ion-Exchange Chromatography

The aim of this study was to characterize the properties of lactoferrin (LF) obtained in a process developed for its isolation from acid whey derived from the production of fresh curd cheese, using a unique technology of ion-exchange chromatography on CIM® monolithic columns. The freeze-dried lactoferrin samples produced on the pilot plant (capacity 1 m3) were examined for the purity, iron-binding capacity, antibacterial activity, and pH- and temperature-stability. Apo-LF inhibited several tested strains (enterobacteria, Staphylococcus, Streptococcus salivarius) except clostridia, lactic acid bacteria, and bifidobacteria. Sample of LF intentionally saturated with Fe3+ lost its antibacterial activity, indicating the involvement of mechanisms based on depriving bacteria of an iron source. All samples, regardless of the iron-saturation level, exhibited stability in pH range 4.0 to 11.0. LF with higher iron content (A-value = 41.9%) showed better thermal stability. Heat treatment up to 72 °C/3 s did not reduce antimicrobial activity against E. coli O157: H7 tox-. Higher purity (above 91%), higher iron-binding capacity and higher inhibitory activity against E. coli O157: H7 tox- compared to some similar products from the market was observed. These results demonstrate a high potential of monolithic ion-exchange chromatography for industrial processing of acid whey as a source of LF that can be used in new products with high-added value. The upscaling of the process is ongoing on a demonstration plant (10–30 m3/day capacity).

Hospital-Associated Multidrug-Resistant MRSA Lineages Are Trophic to the Ocular Surface and Cause Severe Microbial Keratitis

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe and difficult to treat ocular infection. In this study, the population structure of 68 ocular MRSA isolates collected at Massachusetts Eye and Ear between January 2014 and June 2016 was assessed. By using a combination of multilocus sequence typing (MLST) analysis, SCCmec typing and detection of the panton-valentine leukocidin (PVL) gene, we found that the population structure of ocular MRSA is composed of lineages with community and hospital origins. As determined by eBURST analysis of MLST data, the ocular MRSA population consisted of 14 different sequence types (STs) that grouped within two predominant clonal complexes: CC8 (47.0%) and CC5 (41.2%). Most CC8 strains were ST8, harbored type IV SCCmec and were positive for the PVL-toxin (93.7%). The CC5 group was divided between strains carrying SCCmec type II (71.4%) and SCCmec type IV (28.6%). Remaining isolates grouped in 6 different clonal complexes with 3 isolates in CC6 and the other clonal complexes being represented by a single isolate. Interestingly, major MRSA CC5 and CC8 lineages were isolated from discrete ocular niches. Orbital and preseptal abscess/cellulitis were predominantly caused by CC8-SCCmec IV PVL-positive strains. In contrast, infections of the cornea, conjunctiva and lacrimal system were associated with the MDR CC5 lineage, particularly as causes of severe infectious keratitis. This niche specialization of MRSA is consistent with a model where CC8-SCCmec IV PVL-positive strains are better adapted to cause infections of the keratinized and soft adnexal eye tissues, whereas MDR CC5 appear to have greater ability in overcoming innate defense mechanisms of the wet epithelium of the ocular surface.

Prevention of Nosocomial Infections in Critically Ill Patients With Lactoferrin: A Randomized, Double-Blind, Placebo-Controlled Study

OBJECTIVE

To obtain preliminary evidence for the efficacy of lactoferrin as a preventative measure for nosocomial infections and inform the conduct of a definitive study.

DESIGN

Phase 2, multicenter, randomized, double-blind, placebo-controlled study.

SETTING

Medical-surgical ICUs.

PATIENTS

Adult, critically ill patients receiving invasive mechanical ventilation.

INTERVENTIONS

Randomized, eligible, consenting patients expected to require invasive mechanical ventilation more than 48 hours received lactoferrin both enterally and via an oral swab or a placebo of sterile water for up to 28 days.

MEASUREMENTS AND MAIN RESULTS

Of the 214 patients who were randomized, 212 received at least one dose of the intervention and were analyzed (107 lactoferrin and 105 placebo). Protocol adherence was 87.5%. Patients receiving lactoferrin were older (mean [SD], 66.3 [13.5] vs 62.5 [16.2] yr), had a higher Acute Physiology and Chronic Health Evaluation II score (26.8 [7.8] vs 23.5 [7.9]), and need for vasopressors (79% vs 70%). Antibiotic-free days (17.3 [9.0] vs 18.5 [7.1]; p = 0.91) and nosocomial infections (0.3 [0.7] vs 0.4 [0.6] per patient; p = 0.48) did not differ between lactoferrin and placebo groups, respectively. Clinical outcomes for lactoferrin versus placebo were as follows: ICU length of stay (14.5 [18.0] vs 15.0 [37.3] d; p = 0.82), hospital length of stay (25.0 [25.9] vs 28.1 [44.6] d; p = 0.57), hospital mortality (41.1% vs 30.5%; p = 0.11), and 90-day mortality (44.9% vs 32.4%; p = 0.06). Biomarker levels did not differ between the groups.

CONCLUSIONS

Lactoferrin did not improve the primary outcome of antibiotic-free days, nor any of the secondary outcomes. Our data do not support the conduct of a larger phase 3 trial.

IL-36γ regulates mediators of tissue homeostasis in epithelial cells

IL-36 cytokines are critical regulators of mucosal inflammation and homeostasis. IL-36γ regulates the expression of inflammatory cytokines and antimicrobial proteins by gingival epithelial cells (e.g. TIGK cells). Here, we show that IL-36γ also regulates the expression of matrix metalloproteinase 9 (MMP9) and neutrophil gelatinase-associated lipocalin (NGAL), important mediators of antimicrobial immunity and tissue homeostasis in mucosal epithelia. MMP9 and NGAL were not similarly induced by IL-17 or IL-22, thus indicating the importance of IL-36γ in the regulation of MMP9 and NGAL. Mechanistically, MMP9 and NGAL expression was demonstrated to be induced in an IRAK1- and NF-κB-dependent manner. Furthermore, signaling by p38 MAP kinase may enable their expression to be independently regulated by IL-36γ. The stronger IL-36γ-inducible expression of MMP9 and NGAL in terminally differentiating TIGK cells suggests that control of their expression is associated with the maturation of the gingival epithelium. Although MMP9 and NGAL expression in epithelial cells can also be induced by bacteria, their expression in TIGK cells was not induced by the periodontal pathogen Porphyromonas gingivalis, most likely due to antagonism by the gingipain proteinase virulence factors. This study advances our understanding of how IL-36γ may promote oral mucosal immunity and tissue homeostasis, and how this may be dysregulated by bacterial pathogens.

Processed human amniotic fluid retains its antibacterial activity

BACKGROUND

Human amniotic fluid (AF) contains numerous nutrients, trophic factors and defense proteins that provide a nurturing and protective environment for fetal development. Based on reports that AF has antibacterial, anti-inflammatory and regenerative properties, we designed a novel method to process AF for use in clinical care.

METHODS

Six randomly selected lots of processed AF (pAF) were examined to determine whether they retained their antibacterial activity against a panel of wound-associated pathogens E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and E. aerogenes (ESKAPE). To identify proteins in pAF that might be responsible for its antibacterial activity, three different lots of pAF were analyzed with quantitative cytokine arrays that consisted of 400 unique human proteins. One protein identified by microarrays, lactoferrin, and a second prominent antibacterial protein that was not identified by microarrays, lysozyme, were examined by depletion experiments to determine their contribution to the antibacterial activity of pAF.

RESULTS

All six lots of pAF exhibited antibacterial activity against ESKAPE microorganisms, especially against the pathogens predominately found in chronic wounds (i.e. S. aureus and P. aeruginosa). Thirty-one of the peptides on the microarray were annotated as having antibacterial activity and 26 of these were detected in pAF. Cystatin C and lactoferrin were among the most highly expressed antibacterial proteins in pAF. Cystatin C and lactoferrin were confirmed by ELISA to be present in pAF along with lysozyme. Immunoprecipitation of lactoferrin and lysozyme reduced, but did not abolish the antibacterial activities of pAF.

CONCLUSION

Our data demonstrate that pAF maintains antibacterial activity via the preservation of antibacterial proteins against a broad spectrum of wound-associated pathogens.

Cell-specific qRT-PCR of renal epithelial cells reveals a novel innate immune signature in murine collecting duct

The urinary tract is usually culture negative despite its close proximity to microbial flora. The precise mechanism by which the kidneys and urinary tract defends against infection is not well understood. The initial kidney cells to encounter ascending pathogens are the collecting tubule cells that consist of principal cells (PCs) that express aquaporin 2 (AQP2) and intercalated cells (ICs) that express vacuolar H+-ATPase (V-ATPase, B1 subunit). We have previously shown that ICs are involved with the human renal innate immune defense. Here we generated two reporter mice, VATPase B1-cre+tdT+ mice to fluorescently label ICs and AQP2-cre+tdT+ mice to fluorescently label PCs, and then performed flow sorting to enrich PCs and ICs for analysis. Isolated ICs and PCs along with proximal tubular cells were used to measure antimicrobial peptide (AMP) mRNA expression. ICs and PCs were significantly enriched for AMPs. Isolated ICs responded to uropathogenic Escherichia coli (UPEC) challenge in vitro and had higher RNase4 gene expression than control while both ICs and PCs responded to UPEC challenge in vivo by upregulating Defb1 mRNA expression. To our knowledge, this is the first report of isolating murine collecting tubule cells and performing targeted analysis for multiple classes of AMPs.

Antibacterial and Antifungal Activity of Poly(Lactic Acid)-Bovine Lactoferrin Nanofiber Membranes

Antimicrobial materials have become relevant for local therapies preventing microbial resistance induced by systemic antibiotic treatments. This work reports the development of electrospun poly(lactic acid) (PLLA) nanofiber membranes loaded with bovine lactoferrin (bLF) up to 20 wt%. The membranes present smooth and nondefective fibers with mean diameters between 717 ± 197 and 495 ± 127 nm, and an overall porosity of ≈80%. The hydrophobicity of the PLLA membranes is reduced by the presence of bLF. The release profile of bLF correlates with an anomalous transport model, with 17.7 ± 3.6% being released over 7 weeks. The nanofiber mats show no cytotoxicity on human skin fibroblasts and even promote cell proliferation after short exposure periods. Furthermore, the developed membranes display antifungal activity against Aspergillus nidulans by inhibiting spore germination and mycelial growth. These results evidence the strong potential of bLF-PLLA nanofiber membranes to be used as antifungal dressings.

Killing of Cryptosporidium sporozoites by Lactoferrin

Intestinal infection caused by Cryptosporidium is a major contributor to diarrhea morbidity and mortality in young children around the world. Current treatments for children suffering from cryptosporidiosis are suboptimal. Lactoferrin is a glycoprotein found in breast milk. It has showed bacteriostatic and antimicrobial activity in the intestine. However, the effects of lactoferrin on the intestinal parasite Cryptosporidium have not been reported. In this study, we investigated the anticryptosporidial activity of human lactoferrin on different stages of Cryptosporidium. Physiologic concentrations of lactoferrin killed Cryptosporidium parvum sporozoites, but had no significant effect on oocysts viability or parasite intracellular development. Since sporozoites are essential for the infection process, our data reinforce the importance of breastfeeding and point to the potential of lactoferrin as a novel therapeutic agent for cryptosporidiosis.

Prevention of nosocomial infections in critically ill patients with lactoferrin (PREVAIL study): study protocol for a randomized controlled trial

BACKGROUND

Nosocomial infections remain an important source of morbidity, mortality, and increased health care costs in hospitalized patients. This is particularly problematic in intensive care units (ICUs) because of increased patient vulnerability due to the underlying severity of illness and increased susceptibility from utilization of invasive therapeutic and monitoring devices. Lactoferrin (LF) and the products of its breakdown have multiple biological effects, which make its utilization of interest for the prevention of nosocomial infections in the critically ill.

METHODS/DESIGN

This is a phase II randomized, multicenter, double-blinded trial to determine the effect of LF on antibiotic-free days in mechanically ventilated, critically ill, adult patients in the ICU. Eligible, consenting patients will be randomized to receive either LF or placebo. The treating clinician will remain blinded to allocation during the study; blinding will be maintained by using opaque syringes and containers. The primary outcome will be antibiotic-free days, defined as the number of days alive and free of antibiotics 28 days after randomization. Secondary outcomes will include: antibiotic utilization, adjudicated diagnosis of nosocomial infection (longer than 72 h of admission to ICU), hospital and ICU length of stay, change in organ function after randomization, hospital and 90-day mortality, incidence of tracheal colonization, changes in gastrointestinal permeability, and immune function. Outcomes to inform the conduct of a larger definitive trial will also be evaluated, including feasibility as determined by recruitment rates and protocol adherence.

DISCUSSION

The results from this study are expected to provide insight into a potential novel therapeutic use for LF in critically ill adult patients. Further, analysis of study outcomes will inform a future, large-scale phase III randomized controlled trial powered on clinically important outcomes related to the use of LF.

TRIAL REGISTRATION

The trial was registered at www.ClinicalTrials.gov on 18 November 2013.

TRIAL REGISTRATION NUMBER

NCT01996579 .

Prevalence of Class D Carbapenemases among Extended-Spectrum β-Lactamases Producing Escherichia coli Isolates from Educational Hospitals in Shahrekord

INTRODUCTION

Extended-spectrum β-lactamases (ESBLs) are a set of plasmid-borne, various and quickly evolving enzymes that are a main therapeutic issue now-a-days for inpatient and outpatient treatment.

AIM

The aim of this study was to determine multi-drug resistance (MDR) and ESBLs producing E. coli strains, prevalence of class D Carbapenemases among ESBLs producing Escherichia coli isolates from educational hospitals in Shahrekord, Iran.

MATERIALS AND METHODS

Uropathogenic Escherichia coli strains were isolated from patients with Urinary Tract Infections (UTIs). The agar disc diffusion test was used to characterize the antimicrobial sensitivity of the E. coli isolates. The ESBL positive strains were identified by phenotypic double-disk synergy test, by third-generation cephalosporin in combination with or without clavulanic acid. Multiplex PCR was carried out for detection of the three families of OXA-type carbapenamases including OXA-23, OXA-24, and OXA-48 in E. coli strains.

RESULTS

All bacterial isolates were susceptible to meropenem. Ninety isolates produced ESBL, 55 E. coli isolates from inpatients, and 35 isolates from outpatients, with a significant association (p< 0.05). The prevalence of OXA-23, OXA-24, and OXA-48 in the ESBLs producing isolates was respectively 21%, 18%, and 11% for inpatients, and 10%, 8%, and 6% for outpatients.

CONCLUSION

ESBL-producing E. coli isolates are also a major threat in the clinical setting. The findings of this study indicated the high occurrence of ESBLs and multiple antibiotic resistance in E. coli isolates.

Prevalence of Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolates in Nosocomial and Community-Acquired Urinary Tract Infections

Background

Klebsiella pneumoniae is a family member of Enterobacteriaceae. Isolates of K. pneumoniae produce enzymes that cause decomposition of third generation cephalosporins. These enzymes are known as extended-spectrum beta-lactamase (ESBL). Resistance of K. pneumoniae to beta-lactamase antibiotics is commonly mediated by beta-lactamase genes.

Objectives

The aim of this study was to identify the ESBL produced by K. pneumoniae isolates that cause community-acquired and nosocomial urinary tract infections within a one-year period (2013 to 2014) in Kashani and Hajar university hospitals of Shahrekord, Iran.

Patients and Methods

From 2013 to 2014, 150 strains of K. pneumoniae isolate from two different populations with nosocomial and community-acquired infections were collected. The strains were then investigated by double disk synergism and multiplex polymerase chain reaction (PCR).

Results

The study population of 150 patients with nosocomial and community-acquired infections were divided to two groups of 75 each. We found that 48 of the K. pneumoniae isolates in the patients with nosocomial infection and 39 isolates in those with community-acquired infections produced ESBL. The prevalence of TEM1, SHV1 and VEB1 in ESBL-producing isolates in nosocomial patients was 24%, 29.3% and 10.6%, and in community-acquired patients, 17.3%, 22.7% and 8%, respectively.

Conclusions

The prevalence of ESBL-producing K. pneumoniae isolate is of great concern; therefore, continuous investigation seems essential to monitor ESBL-producing bacteria in patients with nosocomial and community-acquired infections.

Therapeutic iron restriction in sepsis

Sepsis represents the systemic immune response to an infection. Mortality of sepsis slightly decreased over the past years, but due to the growing incidence, the absolute number of deaths still increases and belongs to the three most frequent causes of death worldwide. To date, there is no specific treatment for sepsis available yet. Iron is essential to both human beings and microbes and of great significance in many physiological and biochemical processes. Since iron is involved in the bacterial proliferation and immune dysregulation, we hypothesize that restricting host iron levels by application of iron chelators attenuates bacterial growth and improves the detrimental dysregulation of the systemic immune response in sepsis.

Transferrin-mediated iron sequestration as a novel therapy for bacterial and fungal infections

Pathogenic microbes must acquire essential nutrients, including iron, from the host in order to proliferate and cause infections. Iron sequestration is an ancient host antimicrobial strategy. Thus, enhancing iron sequestration is a promising, novel anti-infective strategy. Unfortunately, small molecule iron chelators have proven difficult to develop as anti-infective treatments, in part due to unacceptable toxicities. Iron sequestration in mammals is predominantly mediated by the transferrin family of iron-binding proteins. In this review, we explore the possibility of administering supraphysiological levels of exogenous transferrin as an iron sequestering therapy for infections, which could overcome some of the problems associated with small molecule chelation. Recent studies suggest that transferrin delivery may represent a promising approach to augment both natural resistance and traditional antibiotic therapy.

Antimicrobial protein and Peptide concentrations and activity in human breast milk consumed by preterm infants at risk of late-onset neonatal sepsis

Objective

We investigated the levels and antimicrobial activity of antimicrobial proteins and peptides (AMPs) in breast milk consumed by preterm infants, and whether deficiencies of these factors were associated with late-onset neonatal sepsis (LOS), a bacterial infection that frequently occurs in preterm infants in the neonatal period.

Study design

Breast milk from mothers of preterm infants (≤32 weeks gestation) was collected on days 7 (n = 88) and 21 (n = 77) postpartum. Concentrations of lactoferrin, LL-37, beta-defensins 1 and 2, and alpha-defensin 5 were measured by enzyme-linked immunosorbent assay. The antimicrobial activity of breast milk samples against Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Streptococcus agalactiae was compared to the activity of infant formula, alone or supplemented with physiological levels of AMPs. Samples of breast milk fed to infants with and without subsequent LOS were compared for levels of AMPs and inhibition of bacterial growth.

Results

Levels of most AMPs and antibacterial activity in preterm breast milk were higher at day 7 than at day 21. Lactoferrin was the only AMP that limited pathogen growth >50% when added to formula at a concentration equivalent to that present in breast milk. Levels of AMPs were similar in the breast milk fed to infants with and without LOS, however, infants who developed LOS consumed significantly less breast milk and lower doses of milk AMPs than those who were free from LOS.

Conclusions

The concentrations of lactoferrin and defensins in preterm breast milk have antimicrobial activity against common neonatal pathogens.

Transferrin iron starvation therapy for lethal bacterial and fungal infections

New strategies to treat antibiotic-resistant infections are urgently needed. We serendipitously discovered that stem cell conditioned media possessed broad antimicrobial properties. Biochemical, functional, and genetic assays confirmed that the antimicrobial effect was mediated by supra-physiological concentrations of transferrin. Human transferrin inhibited growth of gram-positive (Staphylococcus aureus), gram-negative (Acinetobacter baumannii), and fungal (Candida albicans) pathogens by sequestering iron and disrupting membrane potential. Serial passage in subtherapeutic transferrin concentrations resulted in no emergence of resistance. Infected mice treated with intravenous human transferrin had improved survival and reduced microbial burden. Finally, adjunctive transferrin reduced the emergence of rifampin-resistant mutants of S. aureus in infected mice treated with rifampin. Transferrin is a promising, novel antimicrobial agent that merits clinical investigation. These results provide proof of principle that bacterial infections can be treated in vivo by attacking host targets (ie, trace metal availability) rather than microbial targets.

Synergistic antibacterial efficacies of the combination of bovine lactoferrin or its hydrolysate with probiotic secretion in curbing the growth of meticillin-resistant Staphylococcus aureus

The occurrence of multidrug-resistant or meticillin-resistant Staphylococcus aureus (MRSA) has become an important issue in clinics. This study evaluated a combinatorial treatment approach by using the well-documented antibacterial protein apo-bovine lactoferrin (apo-bLf) or its hydrolysate and specific probiotic supernatants for controlling MRSA infection. Clinical MRSA strains were isolated from different patient specimens. Apo-bLf-hydrolysate possessed stronger anti-MRSA activity than complete bLf in that it inhibited the growth of most MRSA strains tested in vitro. Otherwise, the supernatants produced by Lactobacillus fermentum (ATCC 11739), Bifidobacterium longum subsp. longum (ATCC 15707) and Bifidobacterium animalis subsp. lactis (BCRC 17394) inhibited the growth of various MRSA strains. Further, L. fermentum or B. animalis subsp. lactis supernatant plus apo-bLf or bLf-hydrolysate led to partially synergistic to synergistic growth-inhibitory activity against MRSA strains. However, L. fermentum and not B. animalis subsp. lactis or B. longum subsp. longum was observed to resist the antibacterial activity of both apo-Lf and bLf-hydrolysate. Therefore, it is suggested that L. fermentum could be the best candidate to be used with apo-bLf or bLf-hydrolysate as a live supplement against MRSA infections.

Antimicrobial potential for the combination of bovine lactoferrin or its hydrolysate with lactoferrin-resistant probiotics against foodborne pathogens

Previous reports have shown that several probiotic strains can resist the antibacterial activity of bovine lactoferrin (bLf), but the results are inconsistent. Moreover, a portion of orally administered apo-bLf is digested in vivo by pepsin to yield bLf hydrolysate, which produces stronger antibacterial activity than that observed with apo-bLf. However, whether bLf hydrolysate affects the growth of probiotic strains is unclear. Therefore, various probiotic strains in Taiwan were collected and evaluated for activity against apo-bLf and bLf hydrolysate in vitro. Thirteen probiotic strains were evaluated, and the growth of Lactobacillus acidophilus ATCC 4356, Lactobacillus salivarius ATCC 11741, Lactobacillus rhamnosus ATCC 53103, Bifidobacterium longum ATCC 15707, and Bifidobacterium lactis BCRC 17394 were inhibited by both apo-bLf and bLf hydrolysate. The growth of 8 strains were not affected by apo-bLf and bLf hydrolysate, including L. rhamnosus ATCC 7469, Lactobacillus reuteri ATCC 23272, Lactobacillus fermentum ATCC 11739, Lactobacillus coryniformis ATCC 25602, L. acidophilus BCRC 14065, Bifidobacterium infantis ATCC 15697, Bifidobacterium bifidum ATCC 29521, and Pediococcus acidilactici ATCC 8081. However, apo-bLf and its hydrolysate inhibited the growth of foodborne pathogens, including Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Enterococcus faecalis. Moreover, the supernatants produced by L. fermentum, B. lactis, and B. longum inhibited the growth of most pathogens. Importantly, a combination of apo-bLf or bLf hydrolysate with the supernatants of cultures of the organisms described above showed synergistic or partially synergistic effects against the growth of most of the selected pathogens. In conclusion, several probiotic strains are resistant to apo-bLf and bLf hydrolysate, warranting clinical studies to evaluate the antimicrobial potential for the combination of apo-bLf or its hydrolysate with specific probiotics.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

Development of a vaccine against Staphylococcus aureus

A vaccine to prevent infections caused by Staphylococcus aureus would have a tremendously beneficial impact on public health. In contrast to typical encapsulated bacterial pathogens, such as Streptococcus pneumoniae, H. influenzae, and Neisseria meningitides, the capsule of S. aureus is not clearly linked to strain virulence in vivo. Furthermore, it is not clear that natural infection caused by S. aureus induces a protective humoral immune response, as does infection caused by typical encapsulated bacteria. Finally, pure B cell or antibody deficiency, in either animal models or in patients, does not predispose to more frequent or more severe S. aureus infections, as it does for infections caused by typical encapsulated bacteria. Rather, primary immune mechanisms necessary for protection against S. aureus infections include professional phagocytes and T lymphocytes (Th17 cells, in particular) which upregulate phagocytic activity. Thus, it is not clear whether an antibody-mediated neutralization of S. aureus virulence factors should be the goal of vaccination. Rather, the selection of antigenic targets which induce potent T cell immune responses that react to the broadest possible array of S. aureus strains should be the focus of antigen selection. Of particular promise is the potential to select antigens which induce both humoral and T cell-mediated immunity in order to generate immune synergy against S. aureus infections. A single-antigen vaccine may achieve this immune synergy. However, multivalent antigens may be more likely to induce both humoral and T cell immunity and to induce protection against a broader array of S. aureus isolates. A number of candidate vaccines are in development, raising the promise that effective vaccines against S. aureus will become available in the not-so-distant future. Possible development programs for such vaccines are discussed.

The thermodynamic and binding properties of the transferrins as studied by isothermal titration calorimetry

BACKGROUND

In mammals, serum-transferrins transport iron from the neutral environment of the blood to the cytoplasm by receptor-mediated endocytosis. Extensive in-vitro studies have focused on the thermodynamics and kinetics of Fe(3+) binding to a number of transferrins. However, little attention has been given to the thermodynamic characterization of the interaction of transferrin with its receptor.

SCOPE OF REVIEW

Iron-loaded transferrin (Tf) binds with high affinity to the specific transferrin receptor (TfR) on the cell surface. The Tf-TfR complex is then internalized via receptor mediated endocytosis into an endosome where iron is released. Here, we provide an overview of recent studies that have used ITC to quantify the interaction of various metal ions with transferrin and highlight our current understanding of the thermodynamics of the transferrin-transferrin receptor system at physiological pH.

GENERAL SIGNIFICANCE

The interaction of the iron-loaded transferrin with the transferrin receptor is a key cellular process that occurs during the normal course of iron metabolism. Understanding the thermodynamics of this interaction is important for iron homeostasis since the physiological requirement of iron must be appropriately maintained to avoid iron-related diseases.

MAJOR CONCLUSIONS

The thermodynamic data revealed stoichiometric binding of all tested metal ions to transferrin with very high affinities ranging between 10(17) and 10(22)M(-1). Iron-loaded transferrin (monoferric or diferric) is shown to bind avidly (K~10(7)-10(8)M(-1)) to the receptor at neutral pH with a stoichiometry of one Tf molecule per TfR monomer. Significantly, both the N- and the C-lobe contribute to the binding interaction which is shown to be both enthalpically and entropically driven. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.

Recombinant human transferrin: beyond iron binding and transport

Iron is indispensible for life and essential for such processes as oxygen transport, electron transfer and DNA synthesis. Transferrin (Tf) is a ubiquitous protein with a central role in iron transport and metabolism. There is evidence, however, that Tf has many other biological roles in addition to its primary function of facilitating iron transport and metabolism, such as its profound effect on mammalian cell growth and productivity. The multiple functions of Tf can be exploited to develop many novel applications. Indeed, over the past several years, considerable efforts have been directed towards exploring human serum Tf (hTf), especially the use of recombinant native hTf and recombinant Tf fusion proteins, for various applications within biotechnology and medicine. Here, we review some of the remarkable progress that has been made towards the application of hTf in these diverse areas and discuss some of the exciting future prospects for hTf.

Structure and mode of action of microplusin, a copper II-chelating antimicrobial peptide from the cattle tick Rhipicephalus (Boophilus) microplus

Microplusin, a Rhipicephalus (Boophilus) microplus antimicrobial peptide (AMP) is the first fully characterized member of a new family of cysteine-rich AMPs with histidine-rich regions at the N and C termini. In the tick, microplusin belongs to the arsenal of innate defense molecules active against bacteria and fungi. Here we describe the NMR solution structure of microplusin and demonstrate that the protein binds copper II and iron II. Structured as a single alpha-helical globular domain, microplusin consists of five alpha-helices: alpha1 (residues Gly-9 to Arg-21), alpha2 (residues Glu-27 to Asn-40), alpha3 (residues Arg-44 to Thr-54), alpha4 (residues Leu-57 to Tyr-64), and alpha5 (residues Asn-67 to Cys-80). The N and C termini are disordered. This structure is unlike any other AMP structures described to date. We also used NMR spectroscopy to map the copper binding region on microplusin. Finally, using the Gram-positive bacteria Micrococcus luteus as a model, we studied of mode of action of microplusin. Microplusin has a bacteriostatic effect and does not permeabilize the bacterial membrane. Because microplusin binds metals, we tested whether this was related to its antimicrobial activity. We found that the bacteriostatic effect of microplusin was fully reversed by supplementation of culture media with copper II but not iron II. We also demonstrated that microplusin affects M. luteus respiration, a copper-dependent process. Thus, we conclude that the antibacterial effect of microplusin is due to its ability to bind and sequester copper II.

Gene-expression signatures of nasal polyps associated with chronic rhinosinusitis and aspirin-sensitive asthma

PURPOSE OF REVIEW

The purpose of this review is to highlight recent advances in gene-expression profiling of nasal polyps in patients with chronic rhinosinusitis and aspirin-sensitive asthma.

RECENT FINDINGS

Gene-expression profiling has allowed simultaneous interrogation of thousands of genes, including the entire genome, to better understand distinct biological and clinical phenotypes associated with nasal polyps. The genes with altered expression in nasal polyps are involved in many cellular processes, including growth and development, immune functions, and signal transduction. The wide-ranging and typically nonoverlapping results reported in the published studies reflect methodological and demographic differences. The identified genes present possible novel therapeutic targets for nasal polyps associated with chronic rhinosinusitis and aspirin-sensitive asthma.

SUMMARY

Gene-expression profiling is a powerful technology that allows definition of expression signatures to characterize patient subgroups, predict response to treatment, and offer novel therapies. Although the ability to interpret the meaning of the individual gene in these signatures remains a challenge, integrated analysis of a large number of these signatures with other genome-scale data sets and more traditional targeted approaches has a potential to revolutionarize understanding and treatment of chronic rhinosinusitis and aspirin-sensitive asthma.

Effect of iron-chelator deferiprone on the in vitro growth of staphylococci

The standard iron-chelator deferoxamine is known to prevent the growth of coagulase-negative staphylococci (CoNS) which are major pathogens in iron-overloaded patients. However, we found that deferoxamine rather promotes the growth of coagulase-positive Staphylococcus aureus. Accordingly, we tested whether deferiprone, a new clinically-available iron-chelator, can prevent the growth of S. aureus strains as well as CoNS. Deferiprone did not at least promote the growth of all S. aureus strains (n=26) and CoNS (n=27) at relatively low doses; moreover, it could significantly inhibit the growth of all staphylococci on non-transferrin-bound-iron and the growth of all CoNS on transferrin-bound iron at relatively high doses. At the same doses, it did not at least promote the growth of all S. aureus strains on transferrin-bound-iron. These findings indicate that deferiprone can be useful to prevent staphylococcal infections, as well as to improve iron overload, in iron-overloaded patients.

Stimulus-dependent impairment of the neutrophil oxidative burst response in lactoferrin-deficient mice

Lactoferrin (LF) is an iron-binding protein found in milk, mucosal secretions, and the secondary granules of neutrophils in which it is considered to be an important factor in the innate immune response against microbial infections. Moreover, LF deficiency in the secondary granules of neutrophils has long been speculated to contribute directly to the hypersusceptibility of specific granule deficiency (SGD) patients to severe, life-threatening bacterial infections. However, the exact physiological significance of LF in neutrophil-mediated host defense mechanisms remains controversial and has not yet been clearly established in vivo using relevant animal models. In this study, we used lactoferrin knockout (LFKO) mice to directly address the selective role of LF in the host defense response of neutrophils and to determine its contribution, if any, to the phenotype of SGD. Neutrophil maturation, migration, phagocytosis, granule release, and antimicrobial response to bacterial challenge were unaffected in LFKO mice. Interestingly, a stimulus-dependent defect in the oxidative burst response of LFKO neutrophils was observed in that normal activation was seen in response to opsonized bacteria whereas an impaired response was evident after phorbol myristate-13-acetate stimulation. Taken together, these results indicate that although LF deficiency alone is not a primary cause of the defects associated with SGD, this protein does play an immunomodulatory role in the oxidative burst response of neutrophils.

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.

Therapeutic potential of iron chelators in diseases associated with iron mismanagement

A considerable array of diseases are now recognized to be associated with misplacement of iron. Excessive deposits of the metal in sensitive tissue sites can result in formation of destructive hydroxyl radicals as well as in stimulation of growth of neoplastic and microbial cell invaders. To counteract potential iron damage, hosts employ the iron chelators, transferrin and lactoferrin. These proteins have been recently developed into pharmaceutical products. Additionally, a variety of low molecular mass iron chelators are being used/tested to treat whole body iron loading, and specific diseases for which the metal is a known or suspected risk factor.

Effect of a derivatized tetrapeptide from lactoferrin on nitric oxide mediated matrix metalloproteinase-2 production by synovial fibroblasts in collagen-induced arthritis in rats

Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteolytic enzymes, which degrade several components of extracellular matrix, in arthritic synovial cells. In cultured synovial fibroblasts, both nitric oxide (NO) and reactive oxygen species (ROS) are potent inducers of MMPs production. PEP1261, a tetrapeptide derivative used in this study, corresponds to residues of 39-42 human lactoferrin. The parent protein lactoferrin is able to inhibit the production of free radicals in rheumatoid joints and it regulates many aspects of inflammation. This study is aimed to examine the effects of PEP1261 on MMP-2 production in the presence of nitric oxide donor in cultured synovial fibroblasts from collagen-induced arthritic rats. PEP1261 affects a significant reduction in nitrite levels as well as in MMP-2 production in SNAP stimulated synovial fibroblasts and this is validated by gelatin zymography and immunoblot analysis. Furthermore, RTPCR analysis has demonstrated that PEP1261 inhibits MMP-2 mRNA expression in SNAP treated synovial fibroblasts. The results of this study suggest that PEP1261 possesses antiarthritic activity by inhibiting nitrite levels as well as MMP-2 expression better than control peptides viz., KRDS and RGDS.

Perspectives on interactions between lactoferrin and bacteriaThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process

Lactoferrin has long been recognized for its antimicrobial properties, initially attributed primarily to iron sequestration. It has since become apparent that interaction between the host and bacteria is modulated by a complex series of interactions between lactoferrin and bacteria, lactoferrin and bacterial products, and lactoferrin and host cells. The primary focus of this review is the interaction between lactoferrin and bacteria, but interactions with the lactoferrin-derived cationic peptide lactoferricin will also be discussed. We will summarize what is currently known about the interaction between lactoferrin (or lactoferricin) and surface or secreted bacterial components, comment on the potential physiological relevance of the findings, and identify key questions that remain unanswered.

Immunolocalization of lactoferrin in healthy and inflamed gingival tissues

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Evolution of the transferrin family: Conservation of residues associated with iron and anion binding

The transferrin family spans both vertebrates and invertebrates. It includes serum transferrin, ovotransferrin, lactoferrin, melanotransferrin, inhibitor of carbonic anhydrase, saxiphilin, the major yolk protein in sea urchins, the crayfish protein, pacifastin, and a protein from green algae. Most (but not all) contain two domains of around 340 residues, thought to have evolved from an ancient duplication event. For serum transferrin, ovotransferrin and lactoferrin each of the duplicated lobes binds one atom of Fe (III) and one carbonate anion. With a few notable exceptions each iron atom is coordinated to four conserved amino acid residues: an aspartic acid, two tyrosines, and a histidine, while anion binding is associated with an arginine and a threonine in close proximity. These six residues in each lobe were examined for their evolutionary conservation in the homologous N- and C-lobes of 82 complete transferrin sequences from 61 different species. Of the ligands in the N-lobe, the histidine ligand shows the most variability in sequence. Also, of note, four of the twelve insect transferrins have glutamic acid substituted for aspartic acid in the N-lobe (as seen in the bacterial ferric binding proteins). In addition, there is a wide spread substitution of lysine for the anion binding arginine in the N-lobe in many organisms including all of the fish, the sea squirt and many of the unusual family members i.e., saxiphilin and the green alga protein. It is hoped that this short analysis will provide the impetus to establish the true function of some of the TF family members that clearly lack the ability to bind iron in one or both lobes and additionally clarify the evolutionary history of this important family of proteins.

Antinociceptive and antipyretic effects of a derivatized tetrapeptide from lactoferrin in rats

PEP1261, a tetrapeptide derivative used in this study, corresponds to residues 39-42 of human lactoferrin. The parent protein lactoferrin is known to exhibit antinociceptive activity and it regulates many aspects of inflammation. This study is aimed to evaluate the antinociceptive and antipyretic activities of PEP1261 in rats. PEP1261 exhibits a significant dose dependent antinociceptive activity with optimal effect at 40 mg/kg body weight (b.w.) (i.p.) in both tail-flick model and acetic acid induced writhing in rats. PEP1261 at the doses of 20 and 40 mg/kg b.w. (i.p.) is also observed to exhibit notable antipyretic effect in lipopolysaccharide-induced pyrexia in rats. In conclusion, the results suggest that PEP1261 possesses antinociceptive and antipyretic activities better than the control peptide KRDS.

Inflammatory gene profiles in gastric mucosa during Helicobacter pylori infection in humans

Helicobacter pylori infection is associated with an inflammatory response in the gastric mucosa, ultimately leading to cellular hyperproliferation and malignant transformation. Hitherto, only expression of a single gene, or a limited number of genes, has been investigated in infected patients. cDNA arrays were therefore used to establish the global pattern of gene expression in gastric tissue of healthy subjects and of H. pylori-infected patients. Two main gene expression profiles were identified based on cluster analysis. The data obtained suggest a strong involvement of selected Toll-like receptors, adhesion molecules, chemokines, and ILs in the mucosal response. This pattern is clearly different from that observed using gastric epithelial cell lines infected in vitro with H. pylori. The presence of a "Helicobacter-infection signature," i.e., a set of genes that are up-regulated in biopsies from H. pylori-infected patients, could be derived from this analysis. The genotype of the bacteria (presence of genes encoding cytotoxin-associated Ag, vacuolating cytotoxin, and blood group Ag-binding adhesin) was analyzed by PCR and shown to be associated with differential expression of a subset of genes, but not the general gene expression pattern. The expression data of the array hybridization was confirmed by quantitative real-time PCR assays. Future studies may help identify gene expression patterns predictive of complications of the infection.

Recombinant human lactoferrin ingestion attenuates indomethacin-induced enteropathy in vivo in healthy volunteers

OBJECTIVE

To determine whether recombinant human lactoferrin ingestion inhibits nonsteroidal antiinflammatory drugs (NSAID)-induced gastroenteropathy in vivo in healthy volunteers as a model for disorders associated with a rise in permeability of the stomach and the small intestine.

DESIGN

A randomized crossover dietary intervention.

SUBJECTS AND INTERVENTIONS

In all, 15 healthy volunteers (age 23+/-1.4 y) were tested. A sucrose and a lactulose/rhamnose (L/R) permeability test was performed to assess gastroduodenal and small intestine permeability as indicator of NSAID-induced gastroenteropathy. All subjects consumed standardized meals for 2 days. On the second day at time=-24 h each subject ingested a drink containing 5 g recombinant human lactoferrin or placebo during breakfast. At t=-9 h, subjects ingested the same drink with 75 mg of the NSAID indomethacin and after an overnight fast at t=-1 h subjects consumed the drink and 50 mg indomethacin. After 1 h, at t=0, a permeability test was performed.

RESULTS

Small intestine permeability after indomethacin and placebo was significantly higher (L/R ratio=0.036; 0.014-0.092, P<0.05) compared to the permeability observed after ingestion of indomethacin and lactoferrin (0.028; 0.015-0.056), whereas gastroduodenal permeability did not differ between the two interventions (P=0.3).

CONCLUSION

Oral recombinant human lactoferrin supplementation during a short-term indomethacin challenge reduced the NSAID-mediated increase in small intestinal permeability and hence may provide a nutritional tool in the treatment of hyperpermeability-associated disorders.

SPONSORSHIP

Grant and human recombinant lactoferrin donated from Agennix Inc., Houston, TX.