Lactoferricin: a lactoferrin-derived peptide with antimicrobial, antiviral, antitumor and immunological properties

Lactation and Intestinal Microbiota: How Early Diet Shapes the Infant Gut

Breast milk is a multifunctional biofluid that provides nutrients along with highly diverse non-nutritive bioactive components such as antibodies, glycans, bacteria, and immunomodulatory proteins. Research over the past decade has confirmed the essential role of breast milk bioactives in the establishment a healthy intestinal microbiota within the infant. The intestinal microbiota of an exclusively breastfed baby is dominated by several species of Bifidobacteria - the most influential member of which is Bifidobacterium longum subspecies infantis (B. infantis) - and is referred to as the milk-oriented microbiome (MOM). MOM is associated with reduced risk of infection in infancy as well as a reduced risk of certain chronic illnesses in adulthood. Establishment and persistence of MOM is dependent on the selective digestion of complex sugar structures in breast milk that are otherwise indigestible to the infant by B. infantis and its relatives. This review focuses primarily on the influence of breast milk glycans and glycosylated proteins on the development of the intestinal microbiome, and how maternal phenotype may influence the development of MOM providing a framework to understand how variation in diet shapes a protective intestinal microbiome.

A Tetrameric Peptide Derived from Bovine Lactoferricin Exhibits Specific Cytotoxic Effects against Oral Squamous-Cell Carcinoma Cell Lines

Several short linear peptides derived from cyclic bovine lactoferricin were synthesized and tested for their cytotoxic effect against the oral cavity squamous-cell carcinoma (OSCC) cell lines CAL27 and SCC15. As a control, an immortalized and nontumorigenic cell line, Het-1A, was used. Linear peptides based on the RRWQWR core sequence showed a moderate cytotoxic effect and specificity towards tumorigenic cells. A tetrameric peptide, LfcinB(20–25)₄, containing the RRWQWR motif, exhibited greater cytotoxic activity (>90%) in both OSCC cell lines compared to the linear lactoferricin peptide or the lactoferrin protein. Additionally, this tetrameric peptide showed the highest specificity towards tumorigenic cells among the tested peptides. Interestingly, this effect was very fast, with cell shrinkage, severe damage to cell membrane permeability, and lysis within one hour of treatment. Our results are consistent with a necrotic effect rather than an apoptotic one and suggest that this tetrameric peptide could be considered as a new candidate for the therapeutic treatment of OSCC.

Lactoferrin Expression in Human and Murine Ocular Tissue

PURPOSE

Lactoferrin (LF) is a multifunctional protein known to provide innate defense due to its antimicrobial and anti-inflammatory properties. In the eye, LF has been identified in the tears and vitreous humor. Its presence in other ocular tissues has not been determined. Our aim is to assess the presence of LF in the cornea, iris, retina and retinal pigment epithelium (RPE) of humans and mice.

METHODS

To test for the endogenous production of LF, reverse transcription polymerase chain reaction was performed in cultured human cells from the cornea and RPE and in murine tissues. To confirm LF localization in specific ocular tissue, immunohistochemistry was performed on flat mounts of cornea, retina and RPE in human donor eyes. The presence of LF was assessed by western blotting in human and mouse ocular tissue and human culture cells (cornea and RPE). To verify antibody specificity, purified human LF and transferrin (TF) were used on 1D and 2D western blots.

RESULTS

LF gene expression was confirmed in the cornea and RPE cell cultures from humans, suggesting that LF is an endogenously produced protein. PCR results from mouse ocular tissue showed LF expression in cornea, iris, RPE, but not in retina. These results were also consistent with immunohistochemical localization of LF in human donor tissue. Antibody reaction for human LF was specific and western blotting showed its presence in the cornea, iris and RPE tissues. A faint reaction for the retina was observed but was likely due to contamination from other ocular tissues. Multiple commercially available antibodies for murine LF cross-reacted with TF, so no reliable results were obtained for murine western blot.

CONCLUSION

LF is expressed in multiple eye tissues of humans and mice. This widespread expression and multifunctional activity of LF suggests that it may play an important role in protecting eye tissues from inflammation-associated diseases.

Efficacy of Bovine Lactoferrin Supplementation in Preventing Late-onset Sepsis in low Birth Weight Neonates: A Randomized Placebo-Controlled Clinical Trial

OBJECTIVES

To evaluate the efficacy of bovine lactoferrin (BLF) in preventing first episode of late-onset sepsis (LOS) in low birth weight (LBW) neonates.

METHODS

In this study conducted from May 2012 to July 2013 in the neonatal intensive care unit (NICU) of a tertiary care hospital, inborn asymptomatic neonates, <2000 g, admitted to NICU in first 12 h of birth with no maternal risk factors for sepsis were randomized to receive BLF or placebo from 1st to 28th day of life. The incidence of culture-proven sepsis and sepsis-attributable mortality after 72 h of life was recorded. Increasing doses of BLF were used with higher birth weights.

RESULTS

Incidence of first episode of culture-proven LOS was significantly lower in the BLF group vs. placebo [2/63 (3.2%) vs. 9/67(13.4%); risk ratio, 0.211; 95% CI, 0.044-1.019; p = 0.036]. Statistically significant reduction in the sepsis-attributable mortality was also seen after use of prophylactic BLF [0/63 (0%) vs. 5/67 (7.5%); p = 0.027].

CONCLUSION

BLF supplementation in LBW neonates reduced the incidence of first episode of LOS.

In vitro and in vivo effect of human lactoferrin on glioblastoma growth

OBJECT

Human lactoferrin (HLF) is a natural protein with antitumor activity. The aim of this study was to investigate the effects of HLF alone and in combination with temozolomide (TMZ), a conventional chemotherapeutic, on human glioblastoma (GBM) cells.

METHODS

The authors cultured fresh human primary cell lines NMD and FN and the continuous cell line U87MG to evaluate proliferation in the presence of HLF alone at different doses (1, 10, and 100 mg/ml, and 1 mg/ml) and in combination with TMZ. In in vivo experiments they assessed tumor size reduction in CD1 nude mice carrying an orthotopic GBM xenograft and orally treated with HLF.

RESULTS

Lactoferrin causes growth inhibition in the NMD and FN primary cell lines and in the U87MG continuous cell line. This inhibition seemed to be modulated by the downregulation of cyclin D1 and D4. Western blot and fluorescence-activated cell sorting analysis showed inhibition of the cell cycle in G0/G1 and G2 phases. When administered in nude mice, HLF (60 mg/kg/day) decreased tumor size about 30%, as shown in both histological analyses and high-field brain MRI. Administration of HLF with TMZ enhanced the effect of chemotherapy both in vitro and in vivo.

CONCLUSIONS

This study demonstrated that HLF can inhibit GBM cell growth, suggesting that this nontoxic substance may have a role in potentiating the effect of current TMZ treatment of GBM.

Antimicrobial activity of synthetic cationic peptides and lipopeptides derived from human lactoferricin against Pseudomonas aeruginosa planktonic cultures and biofilms

Background

Infections by Pseudomonas aeruginosa constitute a serious health threat because this pathogen –particularly when it forms biofilms – can acquire resistance to the majority of conventional antibiotics. This study evaluated the antimicrobial activity of synthetic peptides based on LF11, an 11-mer peptide derived from human lactoferricin against P. aeruginosa planktonic and biofilm-forming cells. We included in this analysis selected N-acylated derivatives of the peptides to analyze the effect of acylation in antimicrobial activity. To assess the efficacy of compounds against planktonic bacteria, microdilution assays to determine the minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill studies were conducted. The anti-biofilm activity of the agents was assessed on biofilms grown under static (on microplates) and dynamic (in a CDC-reactor) flow regimes.

Results

The antimicrobial activity of lipopeptides differed from that of non-acylated peptides in their killing mechanisms on planktonic and biofilm-forming cells. Thus, acylation enhanced the bactericidal activity of the parental peptides and resulted in lipopeptides that were uniformly bactericidal at their MIC. In contrast, acylation of the most potent anti-biofilm peptides resulted in compounds with lower anti-biofilm activity. Both peptides and lipopeptides displayed very rapid killing kinetics and all of them required less than 21 min to reduce 1,000 times the viability of planktonic cells when tested at 2 times their MBC. The peptides, LF11-215 (FWRIRIRR) and LF11-227 (FWRRFWRR), displayed the most potent anti-biofilm activity causing a 10,000 fold reduction in cell viability after 1 h of treatment at 10 times their MIC. At that concentration, these two compounds exhibited low citotoxicity on human cells. In addition to its bactericidal activity, LF11-227 removed more that 50 % of the biofilm mass in independent assays. Peptide LF11-215 and two of the shortest and least hydrophobic lipopeptides, DI-MB-LF11-322 (2,2-dimethylbutanoyl-PFWRIRIRR) and DI-MB-LF11-215, penetrated deep into the biofilm structure and homogenously killed biofilm-forming bacteria.

Conclusion

We identified peptides derived from human lactoferricin with potent antimicrobial activity against P. aeruginosa growing either in planktonic or in biofilm mode. Although further structure-activity relationship analyses are necessary to optimize the anti-biofilm activity of these compounds, the results indicate that lactoferricin derived peptides are promising anti-biofilm agents.

Antimicrobial peptide resistance in Neisseria meningitidis

Antimicrobial peptides (AMPs) play an important role as a host defense against microbial pathogens and are key components of the human innate immune response. Neisseria meningitidis frequently colonizes the human nasopharynx as a commensal but also is a worldwide cause of epidemic meningitis and rapidly fatal sepsis. In the human respiratory tract, the only known reservoir of N. meningitidis, meningococci are exposed to human endogenous AMPs. Thus, it is not surprising that meningococci have evolved effective mechanisms to confer intrinsic and high levels of resistance to the action of AMPs. This article reviews the current knowledge about AMP resistance mechanisms employed by N. meningitidis. Two major resistance mechanisms employed by meningococci are the constitutive modification of the lipid A head groups of lipooligosaccharides by phosphoethanolamine and the active efflux pump mediated excretion of AMPs. Other factors influencing AMP resistance, such as the major porin PorB, the pilin biogenesis apparatus, and capsular polysaccharides, have also been identified. Even with an inherently high intrinsic resistance, several AMP resistance determinants can be further induced upon exposure to AMPs. Many well-characterized AMP resistance mechanisms in other Gram-negative bacteria are not found in meningococci. Thus, N. meningitidis utilizes a limited but highly effective set of molecular mechanisms to mediate antimicrobial peptide resistance. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.

Tumor regression following intravenous administration of lactoferrin- and lactoferricin-bearing dendriplexes

The possibility of using gene therapy for the treatment of cancer is limited by the lack of safe, intravenously administered delivery systems able to selectively deliver therapeutic genes to tumors. In this study, we investigated if the conjugation of the polypropylenimine dendrimer to lactoferrin and lactoferricin, whose receptors are overexpressed on cancer cells, could result in a selective gene delivery to tumors and a subsequently enhanced therapeutic efficacy. The conjugation of lactoferrin and lactoferricin to the dendrimer significantly increased the gene expression in the tumor while decreasing the non-specific gene expression in the liver. Consequently, the intravenous administration of the targeted dendriplexes encoding TNFα led to the complete suppression of 60% of A431 tumors and up to 50% of B16-F10 tumors over one month. The treatment was well tolerated by the animals. These results suggest that these novel lactoferrin- and lactoferricin-bearing dendrimers are promising gene delivery systems for cancer therapy.

From the Clinical Editor

Specific targeting of cancer cells should enhance the delivery of chemotherapeutic agents. This is especially true for gene delivery. In this article, the authors utilized a dendrimer-based system and conjugated this with lactoferrin and lactoferricin to deliver anti-tumor genes. The positive findings in animal studies should provide the basis for further clinical studies.

Lactoferrin Enhanced Apoptosis and Protected Against Thioacetamide-Induced Liver Fibrosis in Rats

BACKGROUND:

Liver fibrosis is the common pathologic consequence of all chronic liver diseases.

AIM:

Lactoferrin (Lf) was investigated for its possible hepatoprotective effect against thioacetamide (TAA)-induced liver fibrosis rat model.

MATERIAL AND METHODS:

Rats received TAA (200 mg/kg/biweekly, ip) for four successive weeks. Lf (200 mg/kg/day, p.o.) or vehicle (VHC) was administered for one month before and another month during TAA injection. Body weight and mortality rate were assessed during the month of TAA-intoxication. Thereafter, serum and liver tissues were analyzed for liver function, oxidative, fibrotic and apoptotic markers.

RESULTS:

Lf conserved rats against TAA-induced body weight-loss and mortality. Preservation of serum albumin, alkaline phosphatase and total bilirubin levels was also observed. Lf also protected rats against TAA-induced decrease in reduced glutathione and increase in malondialdehyde liver contents. Normal liver contents of hydroxyproline, nuclear factor kappa B and alpha fetoprotein; as markers of fibrosis; were increased with TAA and conserved with Lf-TAA. Lf maintained the normal architecture of the liver and immunohistochemical findings revealed increase in apoptotic bodies compared to TAA that favored necrosis.

CONCLUSION:

In conclusion, Lf improved liver function, reduced oxidative stress and liver fibrosis, and enhanced apoptosis in rats with liver fibrosis, suggesting it to have useful therapeutic potential in patients with liver fibrosis.

Oral lactoferrin for the prevention of sepsis and necrotizing enterocolitis in preterm infants

BACKGROUND

Lactoferrin, a normal component of human colostrum and milk, can enhance host defense and may be effective in the prevention of sepsis and necrotizing enterocolitis (NEC) in preterm neonates.

OBJECTIVES

Primary objective To assess the safety and effectiveness of oral lactoferrin in the prevention of sepsis and NEC in preterm neonates. Secondary objectives1. To determine the effects of oral lactoferrin used to prevent neonatal sepsis and/or NEC on duration of positive-pressure ventilation, development of chronic lung disease (CLD) or periventricular leukomalacia (PVL), length of hospital stay to discharge among survivors, and adverse neurological outcomes at two years of age or later.2. To determine the adverse effects of oral lactoferrin in the prophylaxis of neonatal sepsis and/or NEC.When data were available, we analyzed the following subgroups.1. Gestational age < 32 weeks and 32 to 36 weeks.2. Birth weight < 1000 g (extremely low birth weight (ELBW) infants) and birth weight < 1500 g (very low birth weight (VLBW) infants).3. Type of feeding: breast milk versus formula milk.

SEARCH METHODS

We used the search strategy of the Cochrane Neonatal Review Group (CNRG) and updated our search in July 2014. We searched the databases Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PREMEDLINE, EMBASE, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL), as well as trials registries and conference proceedings.

SELECTION CRITERIA

Randomized controlled trials (RCTs) evaluating oral lactoferrin at any dose or duration to prevent sepsis or NEC in preterm neonates.

DATA COLLECTION AND ANALYSIS

Review authors used standard methods of the CNRG.

MAIN RESULTS

Four RCTs are included in this review. Oral lactoferrin supplementation decreased late-onset sepsis (typical risk ratio (RR) 0.49, 95% confidence interval (CI) 0.32 to 0.73; typical risk difference (RD) -0.09, 95% CI -0.14 to -0.04; number needed to treat for an additional beneficial outcome (NNTB) 11, 95% CI 7 to 25; four trials, 678 participants, moderate-quality evidence), NEC stage II or greater (typical RR 0.30, 95% CI 0.12 to 0.76; typical RD -0.05, 95% CI -0.08 to -0.01; NNTB 20, 95% CI 12.5 to 100; two studies, 505 participants, low-quality evidence), and "all-cause mortality" (typical RR 0.30, 95% CI 0.12 to 0.75; typical RD -0.05, 95% CI -0.08 to -0.01; NNTB 20, 95% CI 12.5 to 100; two studies, 505 participants, low-quality evidence).Oral lactoferrin supplementation with a probiotic decreased late-onset sepsis (RR 0.27, 95% CI 0.12 to 0.60; RD -0.13, 95% CI -0.19 to -0.06; NNTB 8, 95% CI 5 to 17; one study, 321 participants, low-quality evidence) and NEC stage II or greater (RR 0.04, 95% CI 0.00 to 0.62; RD -0.05, 95% CI -0.08 to -0.03; NNTB 20, 95% CI 12.5 to 33.3; one study, 496 participants, low-quality evidence), but not "all-cause mortality."Oral lactoferrin with or without probiotics decreased fungal sepsis but not chronic lung disease or length of hospital stay (from one study, low-quality evidence). No adverse effects were reported. Long-term neurological outcomes or periventricular leukomalacia was not evaluated.

AUTHORS' CONCLUSIONS

Evidence of moderate to low quality suggests that oral lactoferrin prophylaxis with or without probiotics decreases late-onset sepsis and NEC stage II or greater in preterm infants without adverse effects. Completion of ongoing trials will provide evidence from more than 6000 preterm neonates and may enhance the quality of the evidence. Clarifications regarding optimum dosing regimens, type of lactoferrin (human or bovine), and long-term outcomes are still needed.

Cationic antimicrobial peptides as potential new therapeutic agents in neonates and children: a review

PURPOSE OF REVIEW

Antimicrobial resistance towards conventional antibiotics is a serious problem for modern medicine and for our society. Multidrug-resistant bacteria are very difficult to treat and treatment options have begun to run out. Here, we summarize the newest studies of drug development using cationic antimicrobial peptides as lead molecules for novel antimicrobial drugs.

RECENT FINDINGS

A new development is the use of antimicrobial peptides not only as direct antimicrobial lead structures but also using their ability to influence the immune system. Such approaches can be used to develop drugs that influence the immune system in a unique way, supporting specific branches of immune cells in order to clear infection. Applying such an 'immune boost' would also minimize the danger of new resistance emerging in bacteria. In addition, searching for and testing substances that trigger the production of host antimicrobial peptides is still ongoing and opens up a totally new avenue for the use of antimicrobial peptides against infections. Currently, more than 10 clinical trials, phase 2 or 3, using antimicrobial peptides are in progress or have been recently completed.

SUMMARY

Multidrug resistance is an urgent problem for modern medicine and novel antimicrobials are needed. Despite some drawbacks, antimicrobial peptides seem now to appear more numerous in clinical trials, indicating the success in developing peptides into novel therapeutics. This can be critical especially for neonates and children, as treatment options for infections with Gram-negatives in neonatal ICUs are becoming rare.

Inhibition of initial bacterial adhesion on titanium surfaces by lactoferrin coating

Because dental implant abutments are located at transmucosal sites, their surface should inhibit bacterial accumulation to prevent peri-implantitis. The authors examined the effects of human lactoferrin (LF), an antibacterial protein present in saliva, as an antibacterial coating on the titanium surface and evaluated its effects before and after mucin-containing artificial saliva (AS) incubation. In the control group, titanium disks were soaked in distilled water, whereas in the LF group, titanium disks were soaked in LF solution to coat the disks. In the control-AS and LF-AS groups, half of the control and LF disks were incubated with AS. To confirm LF adsorption, the fluorescence intensity of fluorescein isothiocyanate-labeled LF was measured. The LF and LF-AS groups showed significantly higher intensity than the control and control-AS groups (P < 0.01). There was no significant difference between the LF and LF-AS groups (P > 0.05). The amount of adhered Streptococcus gordonii significantly increased by incubation with AS (P < 0.01) and significantly decreased by adsorption of LF (P < 0.01). There was no interaction between the two factors, LF adsorption and AS incubation (P = 0.561). These results suggest that the adsorbed LF inhibited bacterial adhesion following AS incubation. According to qualitative LIVE/DEAD analysis, viable bacteria appeared to be decreased in the presence of LF and SEM observation indicated that altered morphologies increased in LF and LF-AS groups. These results suggest that the adsorbed LF remained on the titanium surface after incubation with AS, and the remaining LF inhibited bacterial adhesion and exhibited bactericidal effects. Therefore, the adsorption of LF on the abutment material appears to be effective in preventing peri-implantitis.

Illness in breastfeeding infants relates to concentration of lactoferrin and secretory Immunoglobulin A in mother's milk

BACKGROUND AND OBJECTIVES

This study aims to better understand the relationship between immune compounds in human milk and infant health. We hypothesized that the concentration of immune compounds in milk would relate to infant illness symptoms according to two possible theoretical paradigms. In the 'protective' paradigm, high concentrations of immune compounds prevent infant illness. The converse, the 'responsive' framework, posits that concentrations of immune compounds are elevated in response to infection.

METHODOLOGY

Milk samples (n = 110) and illness data were collected among the Toba of Argentina from 30 mother-infant dyads. Samples were assayed for two immune proteins, lactoferrin and secretory immunoglobulin A (sIgA). Generalized estimating equations were used to assess the relationship between immune composition of milk and symptoms of illness in infants.

RESULTS

Lactoferrin was positively associated with symptoms of illness in infants (odds ratios >1), both in the month preceding the sample collection and the subsequent month. sIgA was negatively associated with symptoms (odds ratios <1) in the preceding and subsequent months, an association which was particularly strong for gastrointestinal symptoms.

CONCLUSIONS AND IMPLICATIONS

The two compounds investigated in our study had opposite relationships with symptoms of illness; the positive relationship between lactoferrin and illness lends support to our 'responsive' paradigm, and the negative relationship between sIgA and symptoms of illness was consistent with our 'protective' framework. That elevated lactoferrin is restricted to periods of illness suggests that there may be a cost to mother or infant associated with persistently elevated lactoferrin that is not incurred with elevated sIgA.

Purification and modeling amphipathic alpha helical antimicrobial peptides from skin secretions of Euphlyctis cyanophlyctis

Antimicrobial peptides as ancient immune system are found in almost all types of living organisms. Amphibian's skin is an important source of bioactive peptides with strong antibacterial, antiviral, and antitumor properties. They have important role in inducing apoptosis as well as cancer therapy in vitro. In this study, we extracted and purified antimicrobial peptides from skin secretions of Euphlyctis cyanophlyctis and named them brevinin-Eu and cyanophlyctin β. They showed favorable antibacterial properties on both Gram-positive and Gram-negative bacteria with ignorable hemolytic activity of <1.9% and 0.7% at very high concentrations of brevinin-Eu and cyanophlyctin β, respectively. For antibacterial activity and MIC determination, two Gram-positive (Staphylococcus aureus PTCC1431 and B. cereus PTCC1247) and two Gram-negative bacteria (Escherichia coli HP101BA 7601c and Klebsiella pneumoniae PTCC1388) were assayed. MIC values of extracted peptides demonstrated that they can inhibit bacterial growth at very low concentration (17 and 12 μg/mL) for brevinin-Eu and cyanophlyctin β, respectively. Structural prediction suggested that the brevinin-Eu can efficiently bind and destroy bacterial membrane, but cyanophlyctin β uses a diverse mode of action.

Unraveling the mechanisms of action of lactoferrin-derived antihypertensive peptides: ACE inhibition and beyond

The characterization of lactoferrin-derived antihypertensive peptides shows that they might act on several molecular targets.

The Antimicrobial and Antiviral Applications of Cell-Penetrating Peptides

Over the past two decades, cell-penetrating peptides (CPPs) have become increasingly popular both in research and in application. There have been numerous studies on the physiochemical characteristics and behavior of CPPs in various environments; likewise, the mechanisms of entry and delivery capabilities of these peptides have also been extensively researched. Besides the fundamental issues, there is an enormous interest in the delivery capabilities of the peptides as the family of CPPs is a promising and mostly non-toxic delivery vector candidate for numerous medical applications such as gene silencing, transgene delivery, and splice correction. Lately, however, there has been an emerging field of study besides the high-profile gene therapy applications-the use of peptides and CPPs to combat various infections caused by harmful bacteria, fungi, and viruses.In this chapter, we aim to provide a short overview of the history and properties of CPPs which is followed by more thorough descriptions of antimicrobial and antiviral peptides. To achieve this, we analyze the origin of such peptides, give an overview of the mechanisms of action and discuss the various practical applications which are ongoing or have been suggested based on research.

Matrix-immobilized yeast for large-scale production of recombinant human lactoferrin

An improved method of recombinant human lactoferrin (hLF) expression in rich culture medium is demonstrated using macroporous microencapsulation.

Evaluation of cationic micropeptides derived from the innate immune system as inhibitors of marine biofouling

A series of 13 short synthetic amphiphilic cationic micropeptides, derived from the antimicrobial iron-binding innate defence protein lactoferrin, have been evaluated for their capacity to inhibit the marine fouling process. The whole biofouling process was studied and microfouling organisms such as marine bacteria and microalgae were included as well as the macrofouling barnacle Balanus improvisus. In total 19 different marine fouling organisms (18 microfoulers and one macrofouler) were included and both the adhesion and growth of the microfoulers were investigated. It was shown that the majority of the peptides inhibited barnacle cyprid settlement via a reversible nontoxic mechanism, with IC50 values as low as 0.5 μg ml(-1). Six peptides inhibited adhesion and growth of microorganisms. Two of these were particularly active against the microfoulers with MIC-values ranging between 0.01 and 1 μg ml(-1), which is comparable with the commercial reference antifoulant SeaNine.

Antimicrobial peptides in the female reproductive tract: a critical component of the mucosal immune barrier with physiological and clinical implications

BACKGROUND

At the interface of the external environment and the mucosal surface of the female reproductive tract (FRT) lies a first-line defense against pathogen invasion that includes antimicrobial peptides (AMP). Comprised of a unique class of multifunctional, amphipathic molecules, AMP employ a wide range of functions to limit microbial invasion and replication within host cells as well as independently modulate the immune system, dampen inflammation and maintain tissue homeostasis. The role of AMP in barrier defense at the level of the skin and gut has received much attention as of late. Given the far reaching implications for women's health, maternal and fetal morbidity and mortality, and sexually transmissible and polymicrobial diseases, we herein review the distribution and function of key AMP throughout the female reproductive mucosa and assess their role as an essential immunological barrier to microbial invasion throughout the reproductive cycle of a woman's lifetime.

METHODS

A comprehensive search in PubMed/Medline was conducted related to AMP general structure, function, signaling, expression, distribution and barrier function of AMP in the FRT, hormone regulation of AMP, the microbiome of the FRT, and AMP in relation to implantation, pregnancy, fertility, pelvic inflammatory disease, complications of pregnancy and assisted reproductive technology.

RESULTS

AMP are amphipathic peptides that target microbes for destruction and have been conserved throughout all living organisms. In the FRT, several major classes of AMP are expressed constitutively and others are inducible at the mucosal epithelium and by immune cells. AMP expression is also under the influence of sex hormones, varying throughout the menstrual cycle, and dependent on the vaginal microbiome. AMP can prevent infection with sexually transmissible and opportunistic pathogens of the female reproductive tissues, although emerging understanding of vaginal dysbiosis suggests induction of a unique AMP profile with increased susceptibility to these pathogens. During pregnancy, AMP are key immune effectors of the fetal membranes and placenta and are dysregulated in states of intrauterine infection and other complications of pregnancy.

CONCLUSIONS

At the level of the FRT, AMP serve to inhibit infection by sexually and vertically transmissible as well as by opportunistic bacteria, fungi, viruses, and protozoa and must do so throughout the hormone flux of menses and pregnancy. Guarding the exclusive site of reproduction, AMP modulate the vaginal microbiome of the lower FRT to aid in preventing ascending microbes into the upper FRT. Evolving in parallel with, and in response to, pathogenic insults, AMP are relatively immune to the resistance mechanisms employed by rapidly evolving pathogens and play a key role in barrier function and host defense throughout the FRT.

Clearance of Escherichia coli O157:H7 infection in calves by rectal administration of bovine lactoferrin

Enterohemorrhagic Escherichia coli (EHEC) strains, of which E. coli O157:H7 is the best-studied serotype, are an important group of foodborne pathogens causing severe illness in humans worldwide. The main reservoirs for EHEC are ruminants, mostly cattle, which harbor the bacteria in their intestinal tracts without showing clinical symptoms. In this study, we used bovine lactoferrin, a natural occurring bactericidal and immunomodulating protein, as an antibacterial agent against EHEC infection in cattle. Nine 3-month-old Holstein-Friesian calves were experimentally infected with EHEC (strain NCTC12900). Three animals received a daily rectal spray treatment with bovine lactoferrin, three animals received an oral treatment, and three animals served as a control group. Blood samples were collected weekly and fecal samples twice weekly to monitor antibody responses and fecal excretion, respectively. Animals in the rectal group ceased shedding within 26 days of the experimental treatment and remained negative. This beneficial effect of bovine lactoferrin was not observed in the oral group, where animals were still shedding at the time of euthanasia (day 61). All groups developed serum responses, but no clear differences could be observed between the groups. However, the results indicate that the use of bovine lactoferrin as a rectal treatment can be a useful strategy to preclude further transmission of EHEC infections from cattle to humans.

Therapeutic interventions in sepsis: current and anticipated pharmacological agents

Sepsis is a clinical syndrome characterized by a multisystem response to a pathogenic assault due to underlying infection that involves a combination of interconnected biochemical, cellular and organ-organ interactive networks. After the withdrawal of recombinant human-activated protein C (rAPC), researchers and physicians have continued to search for new therapeutic approaches and targets against sepsis, effective in both hypo- and hyperinflammatory states. Currently, statins are being evaluated as a viable option in clinical trials. Many agents that have shown favourable results in experimental sepsis are not clinically effective or have not been clinically evaluated. Apart from developing new therapeutic molecules, there is great scope for for developing a variety of drug delivery strategies, such as nanoparticulate carriers and phospholipid-based systems. These nanoparticulate carriers neutralize intracorporeal LPS as well as deliver therapeutic agents to targeted tissues and subcellular locations. Here, we review and critically discuss the present status and new experimental and clinical approaches for therapeutic intervention in sepsis.

Use of lactoferrin in the newborn: where do we stand?

Sepsis and necrotizing enterocolitis (NEC) cause significant morbidity and mortality in the newborn. Their ill effects persist in spite of appropriate and effective antibiotic therapy. Lactoferrin as an adjunct to antibiotics in the treatment of sepsis or NEC in the newborn may improve the clinical outcomes by enhancing the host defense and modulating the inflammatory response. This review focuses on the various aspects of lactoferrin use in the newborn.

The structure of lactoferrin-binding protein B from Neisseria meningitidis suggests roles in iron acquisition and neutralization of host defences

Pathogens have evolved a range of mechanisms to acquire iron from the host during infection. Several Gram-negative pathogens including members of the genera Neisseria and Moraxella have evolved two-component systems that can extract iron from the host glycoproteins lactoferrin and transferrin. The homologous iron-transport systems consist of a membrane-bound transporter and an accessory lipoprotein. While the mechanism behind iron acquisition from transferrin is well understood, relatively little is known regarding how iron is extracted from lactoferrin. Here, the crystal structure of the N-terminal domain (N-lobe) of the accessory lipoprotein lactoferrin-binding protein B (LbpB) from the pathogen Neisseria meningitidis is reported. The structure is highly homologous to the previously determined structures of the accessory lipoprotein transferrin-binding protein B (TbpB) and LbpB from the bovine pathogen Moraxella bovis. Docking the LbpB structure with lactoferrin reveals extensive binding interactions with the N1 subdomain of lactoferrin. The nature of the interaction precludes apolactoferrin from binding LbpB, ensuring the specificity of iron-loaded lactoferrin. The specificity of LbpB safeguards proper delivery of iron-bound lactoferrin to the transporter lactoferrin-binding protein A (LbpA). The structure also reveals a possible secondary role for LbpB in protecting the bacteria from host defences. Following proteolytic digestion of lactoferrin, a cationic peptide derived from the N-terminus is released. This peptide, called lactoferricin, exhibits potent antimicrobial effects. The docked model of LbpB with lactoferrin reveals that LbpB interacts extensively with the N-terminal lactoferricin region. This may provide a venue for preventing the production of the peptide by proteolysis, or directly sequestering the peptide, protecting the bacteria from the toxic effects of lactoferricin.

Influence of Dimerization of Lipopeptide Laur-Orn-Orn-Cys-NH2 and an N-terminal Peptide of Human Lactoferricin on Biological Activity

Lactoferrin (LF) is a naturally occurring antimicrobial peptide that is cleaved by pepsin to lactoferricin (LFcin). LFcin has an enhanced antimicrobial activity as compared to that of LF. Recently several hetero- and homodimeric antimicrobial peptides stabilized by a single disulfide bond linking linear polypeptide chains have been discovered. We have demonstrated that the S–S bond heterodimerization of lipopeptide Laur-Orn-Orn-Cys–NH₂ (peptide III) and the synthetic N-terminal peptide of human lactoferricin (peptide I) yields a dimer (peptide V), which is almost as microbiologically active as the more active monomer and at the same time it is much less toxic. Furthermore, it has been found that the S–S bond homodimerization of both peptide I and peptide III did not affect antimicrobial and haemolytic activity of the compounds. The homo- and heterodimerization of peptides I and III resulted in either reduction or loss of antifungal activity. This work suggests that heterodimerization of antimicrobial lipopeptides via intermolecular disulfide bond might be a powerful modification deserving consideration in the design of antimicrobial peptides.

Characterization of hLF1-11 immobilization onto chitosan ultrathin films, and its effects on antimicrobial activity

hLF1-11 (GRRRRSVQWCA) is an antimicrobial peptide (AMP) with high activity against methicillin-resistant Staphylococcus aureus (MRSA), the most prevalent species in implant-associated infection. In this work, the effect of the surface immobilization on hLF1-11 antimicrobial activity was studied. Immobilization was performed onto chitosan thin films as a model for an implant coating due to its reported osteogenic and antibacterial properties. Chitosan thin films were produced by spin-coating on gold surfaces. hLF1-11 was immobilized onto these films by its C-terminal cysteine in an orientation that exposes the antimicrobial activity-related arginine-rich portion of the peptide. Two levels of exposure (with and without a polyethylene glycol (PEG) spacer) were analyzed. Covalent immobilization was further compared with the AMP physical adsorption onto chitosan films. Surfaces were characterized using ellipsometry, contact angle measurements, atomic force microscopy, infrared and X-ray photoelectron spectroscopies and using a fluorimetric assay for hLF1-11 quantification. Surface antimicrobial activity was assessed through surface adhesion and viability assays using an MRSA (S. aureus ATCC 33591). The incorporation of hLF1-11 increased significantly bacterial adhesion to chitosan films. However, the presence of hLF1-11, namely when immobilized through a PEG spacer, decreased the viability of adherent bacteria with regard to the control surface. These results demonstrated that hLF1-11 after covalent immobilization by its cysteine can maintain activity, particularly if a spacer is applied. However, further studies, exploring the opposite orientation or the same C-terminal orientation, but non-cysteine related, can help to clarify the potential of the hLF1-11 immobilization strategy.

Plant-based biopharming of recombinant human lactoferrin

Recombinant proteins are currently recognized as pharmaceuticals, enzymes, food constituents, nutritional additives, antibodies and other valuable products for industry, healthcare, research, and everyday life. Lactoferrin (Lf), one of the promising human milk proteins, occupies the expanding biotechnological food market niche due to its important versatile properties. Lf shows antiviral, antimicrobial, antiprotozoal and antioxidant activities, modulates cell growth rate, binds glycosaminoglycans and lipopolysaccharides, and also inputs into the innate/specific immune responses. Development of highly efficient human recombinant Lf expression systems employing yeasts, filamentous fungi and undoubtedly higher plants as bioreactors for the large-scale Lf production is a biotechnological challenge. This review highlights the advantages and disadvantages of the existing non-animal Lf expression systems from the standpoint of protein yield and its biological activity. Special emphasis is put on the benefits of monocot plant system for Lf expression and the biosafety aspects of the transgenic Lf-expressing plants.

Killing of melanoma cells and their metastases by human lactoferricin derivatives requires interaction with the cancer marker phosphatidylserine

Despite favorable advancements in therapy cancer is still not curative in many cases, which is often due to inadequate specificity for tumor cells. In this study derivatives of a short cationic peptide derived from the human host defense peptide lactoferricin were optimized in their selective toxicity towards cancer cells. We proved that the target of these peptides is the negatively charged membrane lipid phosphatidylserine (PS), specifically exposed on the surface of cancer cells. We have studied the membrane interaction of three peptides namely LF11-322, its N-acyl derivative 6-methyloctanoyl-LF11-322 and its retro repeat derivative R(etro)-DIM-P-LF11-322 with liposomes mimicking cancerous and non-cancerous cell membranes composed of PS and phosphatidylcholine (PC), respectively. Calorimetric and permeability studies showed that N-acylation and even more the repeat derivative of LF11-322 leads to strongly improved interaction with the cancer mimic PS, whereas only the N-acyl derivative also slightly affects PC. Tryptophan fluorescence of selective peptide R-DIM-P-LF11-322 revealed specific peptide penetration into the PS membrane interface and circular dichroism showed change of its secondary structure by increase of proportion of β-sheets just in the presence of the cancer mimic. Data correlated with in vitro studies with cell lines of human melanomas, their metastases and melanocytes, revealing R-DIM-P-LF11-322 to exhibit strongly increased specificity for cancer cells. This indicates the need of high affinity to the target PS, a minimum length and net positive charge, an adequate but moderate hydrophobicity, and capability of adoption of a defined structure exclusively in presence of the target membrane for high antitumor activity.

Immunomodulatory effects of lactoferrin

Lactoferrin (Lf) is an iron-binding glycoprotein of the transferrin family, which is expressed in most biological fluids with particularly high levels in mammalian milk. Its multiple activities lie in its capacity to bind iron and to interact with the molecular and cellular components of hosts and pathogens. Lf can bind and sequester lipopolysaccharides, thus preventing pro-inflammatory pathway activation, sepsis and tissue damages. Lf is also considered a cell-secreted mediator that bridges the innate and adaptive immune responses. In the recent years much has been learned about the mechanisms by which Lf exerts its activities. This review summarizes the recent advances in understanding the mechanisms underlying the multifunctional roles of Lf, and provides a future perspective on its potential prophylactic and therapeutic applications.

Killing of Mycobacterium avium by lactoferricin peptides: improved activity of arginine- and D-amino-acid-containing molecules

Mycobacterium avium causes respiratory disease in susceptible individuals, as well as disseminated infections in immunocompromised hosts, being an important cause of morbidity and mortality among these populations. Current therapies consist of a combination of antibiotics taken for at least 6 months, with no more than 60% overall clinical success. Furthermore, mycobacterial antibiotic resistance is increasing worldwide, urging the need to develop novel classes of antimicrobial drugs. One potential and interesting alternative strategy is the use of antimicrobial peptides (AMP). These are present in almost all living organisms as part of their immune system, acting as a first barrier against invading pathogens. In this context, we investigated the effect of several lactoferrin-derived AMP against M. avium. Short peptide sequences from both human and bovine lactoferricins, namely, hLFcin1-11 and LFcin17-30, as well as variants obtained by specific amino acid substitutions, were evaluated. All tested peptides significantly inhibited the axenic growth of M. avium, the bovine peptides being more active than the human. Arginine residues were found to be crucial for the display of antimycobacterial activity, whereas the all-d-amino-acid analogue of the bovine sequence displayed the highest mycobactericidal activity. These findings reveal the promising potential of lactoferricins against mycobacteria, thus opening the way for further research on their development and use as a new weapon against mycobacterial infections.

Therapeutic potential of the antimicrobial peptide OH-CATH30 for antibiotic-resistant Pseudomonas aeruginosa keratitis

The therapeutic potential of antimicrobial peptides (AMPs) has been evaluated in many infectious diseases. However, the topical application of AMPs for ocular bacterial infection has not been well investigated. The AMP OH-CATH30, which was identified in the king cobra, exhibits potent antimicrobial activity. In this study, we investigated the therapeutic potential of OH-CATH30 for Pseudomonas aeruginosa keratitis. Ten isolates of P. aeruginosa from individuals with keratitis were susceptible to OH-CATH30 but not to cefoperazone, ciprofloxacin, gentamicin, and levofloxacin. The microdilution checkerboard assay showed that OH-CATH30 exhibited synergistic activity with ciprofloxacin and levofloxacin against antibiotic-resistant P. aeruginosa. Meanwhile, P. aeruginosa did not develop resistance to OH-CATH30, even after exposure at 0.5× the MIC for up to 25 subcultures. Furthermore, treatment with OH-CATH30, alone or in combination with levofloxacin, significantly improved the clinical outcomes of rabbit keratitis induced by antibiotic-resistant P. aeruginosa. Taken together, our data indicate that the topical application of OH-CATH30 is efficacious against drug-resistant P. aeruginosa keratitis. In addition, our study highlights the potential application of AMPs in treating ocular bacterial infections.

Design and high-level expression of a hybrid antimicrobial peptide LF15-CA8 in Escherichia coli

Antimicrobial peptides (AMPs) have been paid considerable attention owing to their broad-spectrum antimicrobial activity and have great potential as novel antimicrobials. In this study, a novel hybrid peptide LF15-CA8 was designed on the basis of bovine lactoferricin (LfcinB) and cecropin A. The gene segment encoding LF15-CA8 was synthesized and cloned into pGEX-4T-BH to form pGEX-4T-LC1 containing one copy of the LF15-CA8 coding region. A series of recombinant vectors containing up to six multiple-copy LF15-CA8 coding regions, i.e., pGEX-4T-LCn (n = 1–6), were subsequently constructed, and used for transformation in Escherichia coli BL21(DE3). After induction with IPTG, pGEX-4T-LC1 and pGEX-4T-LC2 transformants successfully expressed fusion proteins GST-LF15-CA8 and GST-(LF15-CA8)2 in the form of inclusion bodies, respectively. The inclusion bodies were dissolved and the peptide was successfully released in 70 % formic acid in a single step. After purification, about 10.0 mg of the recombinant peptide LF15-CA8 with purity more than 97 % was obtained from 1 l of bacteria culture of pGEX-4T-LC2 transformants. LF15-CA8 caused an increase in antibacterial activity against Gram-positive bacterium (Staphylococcus aureus ATCC 25923) compared with the parent peptides and did not show obvious hemolytic activity against human erythrocytes in the range of effective antibacterial concentration. These results suggest that the peptide LF15-CA8 could be a promising candidate for therapeutic applications, and may lead to a cost-effective solution for the large-scale production of AMPs.

Lactoferrin and the newborn: current perspectives

Neonatal sepsis and necrotizing enterocolitis (NEC) are associated with significant mortality and morbidity. Inflammation secondary to sepsis and NEC increases morbidity, especially those related to the lung, brain and eye. Therapeutic strategies that target inflammation and decrease the emergence of antibiotic resistance are urgently needed. Lactoferrin (Lf) is a multifunctional protein that modulates inflammation, cell growth and differentiation and has broad antimicrobial activity. Studies evaluating the efficacy and safety of Lf in the prevention of neonatal sepsis and NEC are currently in progress, and one completed study shows significant promise. In this article, the functions of this multifunctional molecule and current clinical evidence for its use in the newborn are reviewed. Lf prophylaxis and therapy may have a significant impact in improving clinical outcomes of vulnerable preterm neonates.

Penetration of milk-derived antimicrobial peptides into phospholipid monolayers as model biomembranes

Three antimicrobial peptides derived from bovine milk proteins were examined with regard to penetration into insoluble monolayers formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DPPG). Effects on surface pressure (Π) and electric surface potential (ΔV) were measured, Π with a platinum Wilhelmy plate and ΔV with a vibrating plate. The penetration measurements were performed under stationary diffusion conditions and upon the compression of the monolayers. The two type measurements showed greatly different effects of the peptide-lipid interactions. Results of the stationary penetration show that the peptide interactions with DPPC monolayer are weak, repulsive, and nonspecific while the interactions with DPPG monolayer are significant, attractive, and specific. These results are in accord with the fact that antimicrobial peptides disrupt bacteria membranes (negative) while no significant effect on the host membranes (neutral) is observed. No such discrimination was revealed from the compression isotherms. The latter indicate that squeezing the penetrant out of the monolayer upon compression does not allow for establishing the penetration equilibrium, so the monolayer remains supersaturated with the penetrant and shows an under-equilibrium orientation within the entire compression range, practically.

TGF-β2, a protective intestinal cytokine, is abundant in maternal human milk and human-derived fortifiers but not in donor human milk

OBJECTIVE

This study compared cytokines (in particular transforming growth factor [TGF]-β2) and lactoferrin in maternal human milk (MHM), human-derived milk fortifier (HDMF), and donor human milk (DHM).

MATERIALS AND METHODS

MHM was randomly collected from breastfeeding mothers who had no infectious illness at the time of milk expression. HDMF and DHM were products derived from human milk processed by Holder pasteurization. MHM samples were collected at different times (early/late) and gestations (preterm/term). Lactoferrin was analyzed by western blotting, and cytokines were quantified using commercial enzyme-linked immunosorbent assays. Significance was determined using analysis of variance.

RESULTS

In the 164 samples analyzed, TGF-β2 concentrations in HDMF and preterm MHM (at all collection times) were fivefold higher than in DHM (p<0.05). Early preterm MHM had levels of interleukin (IL)-10 and IL-18, 11-fold higher than DHM (p<0.05). IL-6 in DHM was 0.3% of the content found in MHM. IL-18 was fourfold higher in early MHM versus late MHM regardless of gestational age (p<0.05). Lactoferrin concentration in DHM was 6% of that found in MHM.

CONCLUSIONS

Pasteurization decreases concentrations of most cytokines and lactoferrin in DHM. TGF-β2, a protective intestinal cytokine, has comparable concentrations in HDMF to MHM despite pasteurization.