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Lactoferrin
Lactoferrin
Lactoferrin
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LTF
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesLTF, GIG12, HEL110, HLF2, LF, lactotransferrin
External IDsOMIM: 150210; MGI: 96837; HomoloGene: 1754; GeneCards: LTF; OMA:LTF - orthologs
Orthologs
SpeciesHumanMouse
Entrez

4057

17002

Ensembl

ENSG00000012223

ENSMUSG00000032496

UniProt

P02788

P08071

RefSeq (mRNA)

NM_002343
NM_001199149
NM_001321121
NM_001321122

NM_008522

RefSeq (protein)

NP_001186078
NP_001308050
NP_001308051
NP_002334

NP_032548

Location (UCSC)Chr 3: 46.44 – 46.49 MbChr 9: 110.85 – 110.87 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Lactoferrin (LF), also known as lactotransferrin (LTF), is a multifunctional protein of the transferrin family. Lactoferrin is a globular glycoprotein with a molecular mass of about 80 kDa that is widely represented in various secretory fluids, such as milk, saliva, tears, and nasal secretions. Lactoferrin is also present in secondary granules of PMNs and is secreted by some acinar cells. Lactoferrin can be purified from milk or produced recombinantly. Human colostrum ("first milk") has the highest concentration, followed by human milk, then cow milk (150 mg/L).[5]

Lactoferrin is one of the components of the immune system of the body; it has antimicrobial activity (bacteriocide, fungicide) and is part of the innate defense, mainly at mucosas.[5] It is constantly produced and released into saliva, tears, as well as seminal and vaginal fluid.[6] Lactoferrin provides antibacterial activity to human infants.[7][8] Lactoferrin interacts with DNA and RNA, polysaccharides and heparin, and shows some of its biological functions in complexes with these ligands.

Lactoferrin supplements reduce the risk of respiratory tract infections, based on a recent meta-analysis of randomized controlled trials.[9] As with any supplements sold online, quality may be an issue because nutritional supplement production quality controls are not subject to the same strict regulatory process as medicines.[10]

History

[edit]

Occurrence of iron-containing red protein in bovine milk was reported as early as in 1939;[11] however, the protein could not be properly characterized because it could not be extracted with sufficient purity. Its first detailed studies were reported around 1960. They documented the molecular weight, isoelectric point, optical absorption spectra and presence of two iron atoms per protein molecule.[12][13] The protein was extracted from milk, contained iron and was structurally and chemically similar to serum transferrin. Therefore, it was named lactoferrin in 1961, though the name lactotransferrin was used in some earlier publications, and later studies demonstrated that the protein is not restricted to milk. The antibacterial action of lactoferrin was also documented in 1961, and was associated with its ability to bind iron.[14]

Recombinant lactoferrin production began in the 1990s with the expression of human lactoferrin (hLF) in microbial hosts, notably filamentous fungi such as Aspergillus oryzae, achieving yields exceeding 2 g/L in some cases.[15] Yeast expression systems, particularly Pichia pastoris, were subsequently developed for scalable and cost-effective production.[16] In a landmark development, Sydney-based biotechnology company All G became the first in the world to gain regulatory approval to sell recombinant bovine lactoferrin in China, achieved in November 2024 through precision fermentation (animal-free, microbe-based production).[17]

Structure

[edit]

Genes of lactoferrin

[edit]

At least 60 gene sequences of lactoferrin have been characterized in 11 species of mammals.[18] In most species, stop codon is TAA, and TGA in Mus musculus. Deletions, insertions and mutations of stop codons affect the coding part and its length varies between 2,055 and 2,190 nucleotide pairs. Gene polymorphism between species is much more diverse than the intraspecific polymorphism of lactoferrin. There are differences in amino acid sequences: 8 in Homo sapiens, 6 in Mus musculus, 6 in Capra hircus, 10 in Bos taurus and 20 in Sus scrofa. This variation may indicate functional differences between different types of lactoferrin.[18]

In humans, lactoferrin gene LTF is located on the third chromosome in the locus 3q21-q23. In oxen, the coding sequence consists of 17 exons and has a length of about 34,500 nucleotide pairs. Exons of the lactoferrin gene in oxen have a similar size to the exons of other genes of the transferrin family, whereas the sizes of introns differ within the family. Similarity in the size of exons and their distribution in the domains of the protein molecule indicates that the evolutionary development of lactoferrin gene occurred by duplication.[19] Study of polymorphism of genes that encode lactoferrin helps selecting livestock breeds that are resistant to mastitis.[20]

Molecular structure

[edit]

Lactoferrin is one of the transferrin proteins that transfer iron to the cells and control the level of free iron in the blood and external secretions. It is present in the milk of humans and other mammals,[13] in the blood plasma and neutrophils and is one of the major proteins of virtually all exocrine secretions of mammals, such as saliva, bile, tears and pancreas.[21] Concentration of lactoferrin in the milk varies from 7 g/L in the colostrum to 1 g/L in mature milk.[citation needed][clarification needed]

X-ray diffraction reveals that lactoferrin is based on one polypeptide chain that contains about 700 amino acids and forms two homologous globular domains named N-and C-lobes. N-lobe corresponds to amino acid residues 1-333 and C-lobe to 345-692, and the ends of those domains are connected by a short α-helix.[22][23] Each lobe consists of two subdomains, N1, N2 and C1, C2, and contains one iron binding site and one glycosylation site. The degree of glycosylation of the protein may be different and therefore the molecular weight of lactoferrin varies between 76 and 80 kDa. The stability of lactoferrin has been associated with the high glycosylation degree.[24]

Lactoferrin belongs to the basic proteins, its isoelectric point is 8.7. It exists in two forms: iron-rich hololactoferrin and iron-free apolactoferrin. Their tertiary structures are different; apolactoferrin is characterized by "open" conformation of the N-lobe and the "closed" conformation of the C-lobe, and both lobes are closed in the hololactoferrin.[25]

Each lactoferrin molecule can reversibly bind two ions of iron, zinc, copper or other metals.[26] The binding sites are localized in each of the two protein globules. There, each ion is bonded with six ligands: four from the polypeptide chain (two tyrosine residues, one histidine residue and one aspartic acid residue) and two from carbonate or bicarbonate ions.

Lactoferrin forms a reddish complex with iron; its affinity for iron is 300 times higher than that of transferrin.[27] The affinity increases in weakly acidic medium. This facilitates the transfer of iron from transferrin to lactoferrin during inflammations, when the pH of tissues decreases due to accumulation of lactic and other acids.[28] The saturated iron concentration in lactoferrin in human milk is estimated as 10 to 30% (100% corresponds to all lactoferrin molecules containing 2 iron atoms). It is demonstrated that lactoferrin is involved not only in the transport of iron, zinc and copper, but also in the regulation of their intake.[29] Presence of loose ions of zinc and copper does not affect the iron binding ability of lactoferrin, and might even increase it.

Polymeric forms

[edit]

Both in blood plasma and in secretory fluids lactoferrin can exist in different polymeric forms ranging from monomers to tetramers. Lactoferrin tends to polymerize both in vitro and in vivo, especially at high concentrations.[28] Several authors found that the dominant form of lactoferrin in physiological conditions is a tetramer, with the monomer:tetramer ratio of 1:4 at the protein concentrations of 10−5 M.[30][31][32]

It is suggested that the oligomer state of lactoferrin is determined by its concentration and that polymerization of lactoferrin is strongly affected by the presence of Ca2+ ions. In particular, monomers were dominant at concentrations below 10−10−10−11 M in the presence of Ca2+, but they converted into tetramers at lactoferrin concentrations above 10−9−10−10 M.[30][33] Titer of lactoferrin in the blood corresponds to this particular "transition concentration" and thus lactoferrin in the blood should be presented both as a monomer and tetramer. Many functional properties of lactoferrin depend on its oligomeric state. In particular, monomeric, but not tetrameric lactoferrin can strongly bind to DNA.

Function

[edit]

Lactoferrin belongs to the innate immune system. Apart from its main biological function, namely binding and transport of iron ions, lactoferrin also has antibacterial, antiviral, antiparasitic, catalytic, anti-cancer, and anti-allergic functions and properties.[34]

Enzymatic activity of lactoferrin

[edit]

Lactoferrin hydrolyzes RNA and exhibits the properties of pyrimidine-specific secretory ribonucleases [citation needed]. In particular, by destroying the RNA genome, milk RNase inhibits reverse transcription of retroviruses that cause breast cancer in mice.[35] Parsi women in West India have the milk RNase level markedly lower than in other groups, and their breast cancer rate is three times higher than average.[36] Thus, ribonucleases of milk, and lactoferrin in particular, might play an important role in pathogenesis.

Lactoferrin receptor

[edit]

The lactoferrin receptor plays an important role in the internalization of lactoferrin; it also facilitates absorption of iron ions by lactoferrin. It was shown that gene expression increases with age in the duodenum and decreases in the jejunum.[37] The moonlighting glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been demonstrated to function as a receptor for lactoferrin.[38]

Bone activity

[edit]

Ribonuclease-enriched lactoferrin has been used to examine how lactoferrin affects bone. Lactoferrin has shown to have positive effects on bone turnover. It has aided in decreasing bone resorption and increasing bone formation. This was indicated by a decrease in the levels of two bone resorption markers (deoxypyridinoline and N-telopeptide) and an increase in the levels two bone formation markers (osteocalcin and alkaline phosphatase).[39] It has reduced osteoclast formation, which signifies a decrease in pro-inflammatory responses and an increase in anti-inflammatory responses [40] which indicates a reduction in bone resorption as well.

Interaction with nucleic acids

[edit]

One of the important properties of lactoferrin is its ability to bind with nucleic acids. The fraction of protein extracted from milk, contains 3.3% RNA,[30] but, the protein preferably binds to double-stranded DNA rather than single-stranded DNA. The ability of lactoferrin to bind DNA is used for its isolation and purification using affinity chromatography with columns containing immobilized DNA-containing sorbents, such as agarose with the immobilized single-stranded DNA.[41]

Clinical significance

[edit]
Lactoferrin is a protein found in the immune system, and is a common defense against bacterial infections, which it is able to do by binding to iron with a higher affinity than most proteins.
Lactoferrin (larger protein) and a siderophore of E. coli (smaller protein) are shown. Lactoferrin is a protein found in the immune system, and is a common defense against bacterial infections. Lactoferrin restricts access to host iron by binding to iron with a higher affinity than bacterial proteins.[42]

Antibacterial activity

[edit]

Lactoferrin's primary role is to sequester free iron, and in doing so remove essential substrate required for bacterial growth.[43] Antibacterial action of lactoferrin is also explained by the presence of specific receptors on the cell surface of microorganisms. Lactoferrin binds to lipopolysaccharide of bacterial walls, and the oxidized iron part of the lactoferrin oxidizes bacteria via formation of peroxides. This affects the membrane permeability and results in the cell breakdown (lysis).[43]

Although lactoferrin also has other antibacterial mechanisms not related to iron, such as stimulation of phagocytosis,[44] the interaction with the outer bacterial membrane described above is the most dominant and most studied.[45] Lactoferrin not only disrupts the membrane, but even penetrates into the cell. Its binding to the bacteria wall is associated with the specific peptide lactoferricin, which is located at the N-lobe of lactoferrin and is produced by in vitro cleavage of lactoferrin with another protein, trypsin.[46][47] A mechanism of the antimicrobial action of lactoferrin has been reported as lactoferrin targets H+-ATPase and interferes with proton translocation in the cell membrane, resulting in a lethal effect in vitro.[48]

Lactoferrin prevents the attachment of H. pylori in the stomach, which in turn, aids in reducing digestive system disorders. Bovine lactoferrin has more activity against H. pylori than human lactoferrin.[49]

Antiviral activity

[edit]

Lactoferrin in sufficient strength acts on a wide range of human and animal viruses based on DNA and RNA genomes,[50] including the herpes simplex virus 1 and 2,[51][52][53] cytomegalovirus,[54] HIV,[52][55] hepatitis C virus,[56][57] hantaviruses, rotaviruses, poliovirus type 1,[58] human respiratory syncytial virus, murine leukemia viruses[47] and Mayaro virus.[59] Activity against COVID-19 has been speculated but not proven.[60][61][62][63]

The most studied mechanism of antiviral activity of lactoferrin is its diversion of virus particles from the target cells. Many viruses tend to bind to the lipoproteins of the cell membranes and then penetrate into the cell.[57] Lactoferrin binds to the same lipoproteins thereby repelling the virus particles. Iron-free apolactoferrin is more efficient in this function than hololactoferrin; and lactoferricin, which is responsible for antimicrobial properties of lactoferrin, shows almost no antiviral activity.[50]

Beside interacting with the cell membrane, lactoferrin also directly binds to viral particles, such as the hepatitis viruses.[57] This mechanism is also confirmed by the antiviral activity of lactoferrin against rotaviruses,[47] which act on different cell types.

Lactoferrin also suppresses virus replication after the virus penetrated into the cell.[47][55] Such an indirect antiviral effect is achieved by affecting natural killer cells, granulocytes and macrophages – cells, which play a crucial role in the early stages of viral infections, such as severe acute respiratory syndrome (SARS).[64]

Antifungal activity

[edit]

Lactoferrin and lactoferricin inhibit in vitro growth of Trichophyton mentagrophytes, which are responsible for several skin diseases such as ringworm.[65] Lactoferrin also acts against the Candida albicans – a diploid fungus (a form of yeast) that causes opportunistic oral and genital infections in humans.[66][67] Fluconazole has long been used against Candida albicans, which resulted in emergence of strains resistant to this drug. However, a combination of lactoferrin with fluconazole can act against fluconazole-resistant strains of Candida albicans as well as other types of Candida: C. glabrata, C. krusei, C. parapsilosis and C. tropicalis.[66] Antifungal activity is observed for sequential incubation of Candida with lactoferrin and then with fluconazole, but not vice versa. The antifungal activity of lactoferricin exceeds that of lactoferrin. In particular, synthetic peptide 1–11 lactoferricin shows much greater activity against Candida albicans than native lactoferricin.[66]

Administration of lactoferrin through drinking water to mice with weakened immune systems and symptoms of aphthous ulcer reduced the number of Candida albicans strains in the mouth and the size of the damaged areas in the tongue.[68] Oral administration of lactoferrin to animals also reduced the number of pathogenic organisms in the tissues close to the gastrointestinal tract. Candida albicans could also be completely eradicated with a mixture containing lactoferrin, lysozyme and itraconazole in HIV-positive patients who were resistant to other antifungal drugs.[69] Such antifungal action when other drugs deem inefficient is characteristic of lactoferrin and is especially valuable for HIV-infected patients.[70] Contrary to the antiviral and antibacterial actions of lactoferrin, very little is known about the mechanism of its antifungal action. Lactoferrin seems to bind the plasma membrane of C. albicans inducing an apoptotic-like process.[67][71]

Anticarcinogenic activity

[edit]

The anticancer activity of bovine lactoferrin (bLF) has been demonstrated in experimental lung, bladder, tongue, colon, and liver carcinogeneses on rats, possibly by suppression of phase I enzymes, such as cytochrome P450 1A2 (CYP1A2).[72] Also, in another experiment done on hamsters, bovine lactoferrin decreased the incidence of oral cancer by 50%.[73] Currently, bLF is used as an ingredient in yogurt, chewing gums, infant formulas, and cosmetics.[73]

Cystic fibrosis

[edit]

The human lung and saliva contain a wide range of antimicrobial compound including lactoperoxidase system, producing hypothiocyanite and lactoferrin, with hypothiocyanite missing in cystic fibrosis patients.[74] Lactoferrin, a component of innate immunity, prevents bacterial biofilm development.[75][76] The loss of microbicidal activity and increased formation of biofilm due to decreased lactoferrin activity is observed in patients with cystic fibrosis.[77] In cystic fibrosis, antibiotic susceptibility may be modified by lactoferrin.[78] These findings demonstrate the important role of lactoferrin in human host defense and especially in lung.[79] Lactoferrin with hypothiocyanite has been granted orphan drug status by the EMEA[80] and the FDA.[81]

Necrotizing enterocolitis

[edit]

Low quality evidence suggests that oral lactoferrin supplementation with or without the addition of a probiotic may decrease late onset of sepsis and necrotizing enterocolitis (stage II or III) in preterm infants with no adverse effects.[82]

In diagnosis

[edit]

Lactoferrin levels in tear fluid have been shown to decrease in dry eye diseases such as Sjögren's syndrome.[83] A rapid, portable test utilizing microfluidic technology has been developed to enable measurement of lactoferrin levels in human tear fluid at the point-of-care with the aim of improving diagnosis of Sjögren's syndrome and other forms of dry eye disease.[84]

Technology

[edit]

Extraction

[edit]

Bovine lactoferrin can be isolated from raw milk, colostrum, or whey using methods such as salt extraction, chromatography, and membrane filtration. Lactoferrin from a variety of species, including humans, can also be produced using transgenic organisms as a recombinant protein.[85]

Nanotechnology

[edit]

Lactotransferrin has been used in the synthesis of fluorescent gold quantum clusters, which has potential applications in nanotechnology.[86]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Lactoferrin

View on Grokipedia
from Grokipedia
Lactoferrin is a multifunctional, cationic belonging to the family, with a molecular weight of approximately 80 , first in in and later characterized in human in 1960. It consists of a single polypeptide chain of about 700 amino acids, folded into two symmetrical lobes (N-terminal and C-terminal) connected by an α-helix, each lobe capable of binding one iron ion with high affinity, which contributes to its role in iron homeostasis and antimicrobial defense. Lactoferrin is synthesized by epithelial cells and neutrophils and is present in high concentrations in mammalian —particularly , where levels can reach 7 g/L in humans—as well as in exocrine secretions such as , , nasal fluids, bile, and seminal plasma. In the body, it is primarily stored in the secondary granules of neutrophils, from which it is released during to support innate immune responses. Among its key biological functions, lactoferrin exhibits potent activity, including bacteriostatic and bactericidal effects against a broad spectrum of pathogens by sequestering iron essential for microbial growth and directly disrupting bacterial membranes through its cationic nature. It also demonstrates antiviral properties, such as inhibiting viral entry by binding to host cell receptors like proteoglycans (HSPGs) and potentially (ACE2), with demonstrated activity against viruses including , , and . Additionally, lactoferrin modulates by regulating production, promotes and differentiation, and acts as an , protecting against . Beyond innate immunity, lactoferrin has emerged as a and therapeutic agent; bovine lactoferrin, approved by the FDA as "" (GRAS), is used in supplements for its non-toxic profile and potential benefits in gut health, , and as a for infections and inflammatory conditions. Its iron-binding capacity also aids in preventing in infants while limiting proliferation in the .

History

Discovery

Lactoferrin was first identified in during studies on the iron-binding components of bovine , when Mogens Sørensen and isolated a reddish protein fraction from while fractionating milk proteins. This red coloration, attributed to its iron-binding capacity, distinguished it from other whey proteins, though its full characterization remained elusive for decades. In the 1950s, researchers noted similarities between this milk protein and serum , the primary iron-transport protein in blood, leading to initial confusion as the two shared strong iron-binding affinities and structural resemblances. This overlap prompted speculation that the milk protein might function analogously in iron absorption, but by the early , targeted isolation efforts clarified its distinct identity. The protein was independently purified and named "lactoferrin" in 1960 by Merton L. Groves, who isolated it from bovine milk and highlighted its affinity for iron in a lactose-containing environment, deriving the name from "lacto" (milk) and "ferrin" (iron-binding). Concurrent work by Montreuil et al. and Johansson confirmed its presence in human milk, further distinguishing it from through differences in composition, , and tissue distribution. Early experiments in the began revealing lactoferrin's properties, with Masson et al. demonstrating its bacteriostatic effects in secretions by showing it inhibited through iron sequestration. These findings, building on its iron-binding role, marked the initial recognition of lactoferrin's potential as a host defense factor beyond mere nutrient transport.

Research milestones

In the and , foundational work on lactoferrin focused on its primary , with partial sequencing efforts beginning in the early that revealed its chain composition and overall makeup, comprising approximately 692 residues in the form. These sequencing studies, building on its initial isolation in , demonstrated significant homology to serum , confirming lactoferrin as a distinct member of the transferrin family with about 60% sequence identity, which underscored its shared iron-binding capabilities. By the late , this structural relatedness was further solidified through comparative analyses, highlighting lactoferrin's unique adaptations for mucosal environments compared to serum . During the 1980s, research advanced with the identification of specific lactoferrin receptors, first reported in 1979 on human small intestinal enterocytes, enabling insights into its cellular uptake and iron delivery mechanisms. Subsequent studies in the early 1980s extended this to immune cells like lymphocytes and macrophages, revealing a 100-110 receptor protein that facilitated lactoferrin's immunomodulatory roles. Although initial recombinant expression efforts targeted eukaryotic systems, pioneering work in the late 1980s and early 1990s achieved functional human lactoferrin production in fungal hosts like , overcoming challenges to yield iron-binding active protein for biochemical studies. The 1990s and 2000s brought structural breakthroughs, including the 1995 crystallographic refinement of the diferric human lactoferrin at 2.2 Å resolution, which detailed the bilobal architecture and iron coordination sites involving aspartate, , , and ligands. Concurrently, kinetic studies elucidated the iron-binding mechanism, showing a high-affinity, -dependent process with association rates around 10^6 M^{-1} s^{-1} and release favored below 5, distinguishing lactoferrin's tighter grip on iron compared to . These findings, supported by stopped-flow and , clarified conformational shifts between open and closed states upon metal binding, informing its sequestration of iron. In the and , biopharming progressed with optimized recombinant systems, including high-yield expression in transgenic and reaching up to several grams per liter in liquid cultures, enabling scalable production for research and potential therapeutics. Clinical trials expanded, with over 50 registered studies by 2020 evaluating lactoferrin supplementation for conditions like and , often as an adjuvant to standard care. Recent reviews from 2023 to 2025 have highlighted its antiviral potential against , emphasizing interference with viral entry via ACE2 receptor competition and immunomodulation, based on and observational data. A notable 2023 milestone involved examining lactoferrin in its nascent, reduced state, revealing a molten globule-like conformation with hyper-reactive cysteines that drive hierarchical disulfide formation, providing new insights into its folding and stability. By 2025, research has continued to explore lactoferrin's applications in and enhanced production methods, with no major new structural breakthroughs reported.

Structure

Gene and expression

The human lactoferrin gene, denoted as LTF, is located on chromosome 3 at position 3p21.31 and spans approximately 34 kb of genomic DNA, organized into 17 exons. The bovine ortholog, also named LTF, resides on chromosome 22 and consists of 17 exons spanning about 33 kb. The promoter region of the LTF gene contains multiple regulatory elements that respond to inflammatory signals, including binding sites for the transcription factor NF-κB, which facilitates activation during immune responses. These elements enable rapid transcriptional upregulation in response to proinflammatory cues, ensuring timely production of lactoferrin in activated cells. Expression of the LTF gene exhibits tissue-specific patterns, with prominent levels in neutrophils, , salivary glands, , and lactating mammary , where it is stored in secretory granules or secreted into exocrine fluids. The gene is upregulated by inflammatory stimuli such as (LPS) and cytokines including IL-1β, which activate pathways to enhance transcription in epithelial and myeloid cells. The LTF gene demonstrates strong evolutionary conservation across mammals, reflecting its essential role in innate immunity, with approximately 70% amino acid sequence identity between and bovine orthologs, particularly in the coding exons that encode functional domains. This conservation underscores shared regulatory mechanisms and protein functionality despite species-specific variations in expression levels.

Molecular architecture

Lactoferrin is a with a of approximately 80 , consisting of a single polypeptide chain that varies slightly by species, such as 691 in humans and 689 in bovines. The protein's primary structure is derived from a gene-encoded sequence, with the mature chain lacking an N-terminal . The tertiary structure of lactoferrin features two homologous globular lobes—the N-terminal lobe (residues 1–332) and the C-terminal lobe (residues 344–691 in humans)—each subdivided into two domains (N1/N2 and C1/C2) that form a bilobal architecture. These lobes are connected by a flexible region comprising a short α-helix (residues 333–343 in humans), which allows for relative movement between the lobes. Each domain adopts a Rossmann-like fold, characterized by a central mixed β-sheet flanked by α-helices, with the predominant secondary structural elements being approximately 33–34% α-helices and 17–18% β-strands across the protein. Each lobe contains a single iron-binding site located in the inter-domain cleft, coordinated by four protein —two residues, one , and one aspartate—and a synergistic anion (CO₃²⁻) that serves as the fifth . In the apo form (iron-free), the inter-domain cleft is open, facilitating iron access, whereas binding of Fe³⁺ in the holo form induces a conformational change that closes the cleft by approximately 7–10 Å through hinge motion at the β-strands linking the domains, enhancing iron affinity. Lactoferrin is N-glycosylated at multiple sites, with humans featuring three conserved sites (Asn137, Asn478, and Asn565) and bovines having four to five (Asn233, Asn368, Asn476, Asn545, and variably Asn281), primarily bearing complex and hybrid glycans. These N-linked glycans contribute to the protein's conformational stability by shielding protease-sensitive regions and modulating interactions with cellular receptors.

Polymeric variants

Lactoferrin exists predominantly as a in under standard physiological conditions, reflecting its globular structure with two homologous lobes connected by a short α-helix. However, it undergoes self-association to form dimers at neutral pH (around 7.0) and low , where the protein's positive charge facilitates intermolecular interactions. This dimerization is concentration-dependent, becoming more pronounced at higher protein levels, and the interface involves helix-helix contacts primarily in the C-lobes of adjacent molecules. Under specific conditions, such as elevated concentrations or the presence of calcium ions, lactoferrin assembles into higher-order oligomers, including tetramers observed at molecular weights of approximately 300–350 . Tetrameric forms are among the most abundant multimeric in bovine , alongside dimers and even higher oligomers like trimers. Polymeric variants, including dimers and tetramers, have been detected in biological secretions such as , where reveals multiple molecular forms of lactoferrin. The oligomeric state of lactoferrin exhibits pH dependence, with monomers dominating at acidic values like 2.0 due to enhanced electrostatic repulsion, while dimers predominate at neutral 7.0. This transition influences the protein's and functional availability in varying physiological environments, such as the acidic milieu of infected tissues. A notable variant is delta-lactoferrin (ΔLf), a shorter intracellular isoform produced via of the lactoferrin gene, lacking the and N-terminal region of the canonical form. Unlike the secreted monomeric lactoferrin, ΔLf localizes to the nucleus and , functioning as a that regulates genes involved in arrest and antiproliferation. and bovine lactoferrins share approximately 70% sequence identity, but differences in and lobe flexibility lead to variations in stability, with bovine forms showing greater propensity for multimerization in milk due to environmental factors.

Biosynthesis and sources

Genetic regulation

The expression of the lactoferrin gene (LTF) is primarily regulated at the transcriptional level through the action of acute-phase response factors, which are activated in response to inflammatory stimuli such as cytokines and lipopolysaccharide (LPS). During inflammation, signal transducer and activator of transcription 3 (STAT3) binds to specific sites in the LTF promoter, facilitating rapid induction of gene expression; for instance, in bovine mammary epithelial cells, LPS stimulation leads to STAT3 activation via the Janus kinase (JAK)-STAT pathway, enhancing LTF transcription as part of the innate immune response. Similarly, CCAAT/enhancer-binding protein (C/EBP) family members, particularly C/EBPε and C/EBPβ, are essential for promoter activation, cooperating with Sp1 to drive LTF expression during myeloid differentiation and acute inflammation; studies in human promyelocytic cell lines demonstrate that C/EBP binding to the proximal promoter region is required for cytokine-induced upregulation. These factors integrate signals from proinflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), positioning LTF as a key acute-phase reactant that modulates iron homeostasis and antimicrobial defense. Epigenetic modifications further fine-tune LTF expression by altering accessibility at the promoter region, particularly in epithelial cells. at CpG islands within the LTF proximal promoter represses transcription in non-expressing tissues, while hypomethylation correlates with active expression; in human mammary epithelial cells, treatment with inhibitors increases LTF mRNA levels by reducing methylation occupancy, thereby permitting access. acetylation, mediated by histone acetyltransferases, promotes an open conformation that enhances LTF inducibility; in mammary epithelial models, inflammatory stimuli induce and H4 at the promoter, facilitating C/EBP and recruitment and boosting expression during or . These modifications provide a stable yet reversible mechanism for regulating LTF in response to environmental cues, ensuring context-specific protein production without altering the underlying DNA sequence. Species-specific differences influence LTF inducibility, notably in response to LPS. In bovine cells, the LTF promoter exhibits stronger LPS responsiveness due to multiple NF-κB and STAT3 binding sites, resulting in robust upregulation during mastitis; bovine mammary epithelial cells show 10- to 20-fold increases in LTF mRNA upon LPS exposure, compared to more modest 2- to 5-fold induction in human counterparts. This disparity arises from promoter architecture variations, with bovine LTF more sensitive to Toll-like receptor 4 (TLR4) signaling, reflecting adaptations to ruminant immune challenges.

Natural occurrence

Lactoferrin is primarily found in mammalian exocrine secretions and immune cells, serving as a key component of innate immunity. The highest concentrations occur in , the initial milk produced after birth. In humans, typically contains 5–7 g/L of lactoferrin, with levels declining sharply to 1–3 g/L in mature milk as progresses. In bovine , concentrations can reach up to 8 g/L, similarly decreasing in subsequent milk production. These elevated levels in support neonatal immune defense by providing antimicrobial protection and iron regulation. Lactoferrin is also present in other exocrine secretions at mucosal sites, contributing to barrier . In human saliva, concentrations range from approximately 0.008 g/L, while contain 1–2 g/L, and nasal secretions exhibit levels around 0.001 g/L. Within neutrophils, lactoferrin is a major constituent of secondary (specific) granules, comprising 15–20% of their protein content and enabling rapid release during inflammatory responses. These distributions highlight lactoferrin's role in local innate immunity at epithelial surfaces. Concentrations of lactoferrin vary across species, with higher levels generally observed in humans and bovines compared to other mammals; it is notably absent or present at very low levels in non-mammalian vertebrates, where fulfills similar functions. Factors such as age, physiological state, and health influence levels—for instance, concentrations increase during due to enhanced neutrophil degranulation and glandular secretion. This dynamic occurrence underscores lactoferrin's adaptive contribution to mucosal immunity, particularly in protecting vulnerable interfaces like the respiratory and gastrointestinal tracts.

Functions

Iron binding and transport

Lactoferrin binds ferric iron (Fe³⁺) with exceptionally high affinity, characterized by a (K_d) of approximately 10^{-20} M at physiological 7.4. This binding occurs at two symmetric sites, one in each of the protein's N- and C-terminal lobes, and requires a synergistic anion, most commonly (CO₃²⁻), which coordinates bidentately with the iron ion to stabilize the complex. The coordination involves specific residues, including aspartate, , and , forming an octahedral geometry around the metal. Iron release from lactoferrin is -dependent, occurring efficiently only at low values below 4, where disrupts the and opens the protein's lobes. In cellular contexts, lactoferrin undergoes , facilitating intracellular iron transport via endosomal pathways, though it retains its iron load in the mildly acidic endosomal environment unlike other iron carriers. Following processing, lactoferrin is directed toward exocytic vesicles for export into mucosal secretions, where it delivers bioavailable iron to epithelial cells and supports local at barrier sites such as the . This export mechanism ensures controlled iron distribution in exocrine fluids, including and . Lactoferrin plays a key role in iron by sequestering free iron, thereby preventing its availability to extracellular pathogens in a process known as nutritional immunity. In the intestinal lumen, it modulates systemic iron absorption by binding dietary iron and facilitating its uptake through enterocytes via specific receptors, while limiting excess free iron that could fuel microbial growth during . Relative to serum , lactoferrin exhibits tighter iron binding affinity and enhanced stability, retaining Fe³⁺ across a wider range down to 4, whereas releases iron at approximately 5.5 in endosomes to support cellular uptake. This property underscores lactoferrin's adaptation for mucosal defense and extracellular iron management rather than systemic circulation.

Receptor interactions

Lactoferrin primarily interacts with the low-density lipoprotein receptor-related protein 1 (), a multifunctional endocytic receptor expressed on hepatocytes, macrophages, and various other cell types, facilitating and intracellular signaling. binds both apo- and holo-lactoferrin forms, enabling cellular uptake primarily through clathrin-mediated endocytosis into early endosomes, which supports iron delivery to cells while regulating extracellular levels. This interaction is independent of for certain signaling events, allowing lactoferrin to activate downstream pathways even when internalization is blocked. Other receptors include intelectin-1 (ITLN1), predominantly expressed on enterocytes in the , which mediates lactoferrin uptake and subcellular trafficking in a species-specific manner; for instance, human intelectin-1 binds human lactoferrin efficiently, while porcine counterparts show homology but vary in affinity for cross-species binding. Additionally, , found on monocytes, macrophages, and other immune cells, interacts with lactoferrin to modulate inflammatory responses, often by competing with for binding and inhibiting pro-inflammatory signaling. These receptor interactions exhibit species differences, with porcine lactoferrin receptors sharing structural homology to human ones but displaying altered expression patterns during intestinal development. Upon binding, lactoferrin-LRP1 engagement activates signaling pathways such as /extracellular signal-regulated kinase (MAPK/ERK), promoting anti-inflammatory effects by regulating production and cell survival in immune and epithelial cells. Internalization via these receptors occurs rapidly, with a plasma of approximately 10 minutes following intravenous administration, reflecting quick endocytic clearance primarily by the . Receptor density varies in pathological conditions; for example, expression is upregulated in cancer cells, including those of , pancreatic, and origins, correlating with enhanced tumor , , and poor prognosis, potentially facilitating lactoferrin-mediated modulation of tumor microenvironments.

Enzymatic and catalytic roles

Lactoferrin exhibits peroxidase-like activity in the presence of (H₂O₂), enabling the oxidation of substrates including to generate such as hydroxyl radicals, which possess bactericidal properties by damaging microbial membranes through peroxidation. This prooxidant mechanism is enhanced by the apo-form of lactoferrin (iron-free) and requires H₂O₂ as a cofactor, contributing to innate immune defense without relying on iron sequestration. In addition to its oxidative roles, lactoferrin displays intrinsic nuclease activities, functioning as both a deoxyribonuclease (DNase) and ribonuclease (RNase) capable of hydrolyzing microbial DNA and RNA. These metal-dependent enzymatic functions, optimal at neutral pH (7.0–7.5), target foreign nucleic acids to disrupt pathogen replication and are particularly relevant in acidic microenvironments like phagolysosomes. The DNase activity converts supercoiled DNA to relaxed or linear forms, while RNase preferentially cleaves single-stranded RNA substrates such as poly C. Lactoferrin also mimics superoxide dismutase by scavenging superoxide radicals (O₂⁻), catalyzing their dismutation to reduce and protect host cells from ROS-induced damage. This catalysis occurs independently of bound iron, with the apo-form showing enhanced efficacy, and operates at a rate comparable to spontaneous dismutation (approximately 10⁶ M⁻¹ s⁻¹). The structural basis for these active sites resides in lactoferrin's N- and C-terminal lobes, where cationic residues facilitate substrate binding.

Nucleic acid and bone interactions

Lactoferrin exhibits electrostatic binding to polyanionic nucleic acids such as DNA and RNA due to its positively charged surface regions interacting with the negatively charged phosphate backbone. This interaction facilitates DNA condensation, which is leveraged in non-viral gene delivery systems where lactoferrin compacts plasmid DNA into stable nanoparticles for targeted cellular uptake. Additionally, lactoferrin provides protective stabilization to host DNA by shielding it from oxidative damage induced by reactive oxygen species, such as hydroxyl radicals, thereby preserving genomic integrity during stress conditions. In bone remodeling, lactoferrin promotes osteogenesis by stimulating osteoblast proliferation and differentiation primarily through the receptor-related protein 1 (), a key receptor that mediates its mitogenic signaling via pathways like ERK activation. Concentrations ranging from 1 to 100 μg/mL, which align with physiological levels, enhance osteoblast activity, leading to increased expression and matrix mineralization. Concurrently, lactoferrin inhibits osteoclastogenesis by suppressing RANKL-induced differentiation of precursor cells, thereby reducing without affecting mature osteoclast function. Lactoferrin accelerates in animal models, with of bovine lactoferrin at 85 mg/kg/day promoting tibial repair in ovariectomized s by enhancing formation and mechanical strength. Local application in calvarial defect models similarly increases volume and regeneration, demonstrating its potential in supporting recovery through balanced osteoblast-osteoclast regulation.

Antimicrobial properties

Antibacterial mechanisms

Lactoferrin exhibits potent antibacterial activity primarily through iron sequestration, a mechanism that deprives bacteria of this essential nutrient required for growth and replication. By binding ferric iron with high affinity, apo-lactoferrin (iron-free form) creates an iron-limited environment in biological fluids, exerting a bacteriostatic effect on pathogens such as and . This inhibition is evident at minimum inhibitory concentrations (MICs) typically ranging from 10 to 100 μg/mL, where bacterial proliferation is halted without direct cell killing. The bacteriostatic nature can be reversed by exogenous iron supplementation, underscoring the centrality of nutritional deprivation in this process. In addition to iron withholding, lactoferrin and its derived peptides directly target bacterial membranes, leading to bactericidal outcomes. Upon pepsin-mediated hydrolysis in the stomach, lactoferrin yields lactoferricin, a cationic peptide (e.g., bovine lactoferricin spanning residues 17-41) that interacts electrostatically with the negatively charged lipopolysaccharide (LPS) layer of Gram-negative bacteria or teichoic acids in Gram-positive species. This binding disrupts membrane integrity, increases permeability to dyes like N-phenyl-1-naphthylamine, depolarizes the cytoplasmic membrane, and causes leakage of intracellular contents such as β-galactosidase, ultimately resulting in cell lysis. Studies using scanning electron microscopy and transmission electron microscopy confirm physical membrane damage in E. coli strains exposed to these peptides at concentrations around 1-4 μM. This multifactorial membrane interaction extends efficacy against both Gram-negative (E. coli, P. aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria. Lactoferrin further potentiates conventional antibiotics through synergistic interactions, enhancing their penetration and efficacy against resistant strains. For instance, it amplifies the activity of against methicillin-resistant S. aureus (MRSA) by up to four-fold, lowering required doses and mitigating toxicity while disrupting bacterial defenses. This synergy arises from lactoferrin's ability to destabilize outer membranes, facilitating influx. Bacterial resistance to lactoferrin remains exceedingly rare, attributable to its diverse, non-single-target modes of action that overwhelm adaptive pathways. Moreover, lactoferrin effectively combats biofilms—structured communities that confer tolerance—by inhibiting initial adhesion and formation (e.g., in P. aeruginosa for up to 24 hours) and eradicating mature biofilms (e.g., in S. epidermidis for up to 72 hours) through iron limitation and direct matrix disruption.

Antiviral effects

Lactoferrin exerts antiviral effects primarily by blocking viral entry into host cells through direct binding to glycoproteins. For instance, it interacts with the gp120 protein on HIV-1, inhibiting viral attachment and fusion with a half-maximal inhibitory concentration () of approximately 35 μg/mL. Similarly, lactoferrin and its derived peptides bind to the E2 envelope protein of (HCV), preventing infection of hepatocytes; studies report values around 0.6–0.7 μM for related pseudovirus models. These interactions disrupt the virus's ability to engage host receptors, such as proteoglycans (HSPGs), thereby impeding attachment and internalization across enveloped viruses. Beyond entry blockade, lactoferrin demonstrates intracellular inhibition by interfering with viral replication processes. In the case of human papillomavirus (HPV), it modulates signaling to suppress viral gene expression and replication, in addition to preventing initial binding and uptake into . This dual action—early interference at the cell surface and later modulation of host pathways—contributes to its broad inhibitory profile without direct virucidal effects. Recent studies from 2023–2024 highlight lactoferrin's efficacy against , where it blocks the spike protein-ACE2 receptor interaction and inhibits - or TMPRSS2-dependent entry pathways. Bovine lactoferrin suppressed replication by up to 93% via inhibition and reduced viral loads in animal models. Liposomal formulations of lactoferrin further enhance this potency, achieving greater than 50% reduction against pseudoviruses at concentrations where free lactoferrin shows minimal activity, indicating improved cellular uptake and targeted delivery. Lactoferrin also displays broad-spectrum activity against arboviruses like Zika and Dengue by preventing attachment to host cell receptors. It inhibits Zika virus infection in Vero cells by up to 80% in a dose-dependent manner, acting at both input and output stages of the replication cycle. For Dengue virus serotypes 1–4, bovine lactoferrin binds HSPGs, low-density lipoprotein receptor, and DC-SIGN, reducing infectivity with IC50 values around 40–166 μg/mL and significantly lowering plaque formation.

Antifungal and antiparasitic activities

Lactoferrin exhibits antifungal activity primarily through iron sequestration, which deprives fungal cells of essential iron for growth, and direct membrane disruption that compromises cell integrity. Against , a common opportunistic pathogen, bovine lactoferrin demonstrates inhibitory effects with minimum inhibitory concentrations (MICs) typically ranging from 50 to 200 μg/mL, depending on strain susceptibility and assay conditions. This dual mechanism—iron deprivation limiting metabolic processes and membrane damage inducing leakage—has been observed , where lactoferrin binds to fungal cell surfaces and alters permeability. Lactoferrin enhances the efficacy of conventional antifungals, notably synergizing with to reduce required doses and overcome resistance in Candida species. Studies show that combining lactoferrin with results in potent fungistasis at sub-MIC levels, as the protein facilitates membrane targeting while the drug disrupts integrity. Derived peptides like lactoferricin contribute to this activity, exhibiting MICs of 5-50 μg/mL against fungi through rapid membrane permeabilization and (ROS) generation that exacerbates . In antiparasitic contexts, lactoferrin inhibits growth by binding and disrupting hemozoin formation, a critical process in the parasite's food , thereby accumulating toxic intermediates. For Giardia lamblia, an intestinal protozoan, lactoferrin blocks parasite attachment to host epithelial cells, preventing colonization while also inducing endocytosis-mediated growth arrest and morphological alterations at effective concentrations around 1000 μg/mL (12.5 μM). These actions extend to ROS-mediated toxicity, where lactoferrin and its peptides elevate intracellular ROS and nitric oxide levels, leading to parasite death without relying solely on iron . Recent reviews underscore lactoferrin's emerging potential in treatment, highlighting its immunomodulatory effects that enhance activation and reduce parasite burden in Leishmania species, often in combination therapies to improve clinical outcomes in canine models; a study showed stable clinical scores with nucleotide-lactoferrin supplementation over 6 months. Lactoferricin derivatives amplify this by directly targeting parasite membranes at low μg/mL concentrations, positioning lactoferrin as a versatile adjunct for eukaryotic control.

Clinical applications

Iron deficiency and anemia treatment

Oral supplementation with lactoferrin at doses of 100–250 mg/day has demonstrated efficacy in increasing levels among patients with . A 2024 meta-analysis of seven randomized clinical trials involving 1,397 participants found that oral bovine lactoferrin produced a statistically significant greater rise in compared to ferrous sulfate, with a standardized mean difference of 0.81 (95% CI: 0.42–1.21, p < 0.0001). In representative studies included in such analyses, increases averaged approximately 1.5 g/dL with lactoferrin versus 0.8 g/dL with ferrous sulfate after 1–2 months of treatment. This approach leverages lactoferrin's role in iron binding and transport to deliver iron more efficiently. The mechanism underlying lactoferrin's benefits involves enhanced intestinal absorption of iron through receptor-mediated uptake by enterocytes in the small intestine. Unlike non-specific iron salts, lactoferrin binds iron tightly and facilitates its endocytosis via lactoferrin receptors on the apical membrane of intestinal epithelial cells, followed by transcytosis and release into the bloodstream. This process not only improves bioavailability but also minimizes gastrointestinal side effects such as nausea and constipation, which are common with ferrous sulfate and contribute to treatment discontinuation. Clinical evidence supports lactoferrin's use particularly in vulnerable populations like pregnant women and infants, where iron needs are heightened. A 2023 review of trials indicated that lactoferrin supplementation effectively corrects anemia in pregnancy by improving hematological parameters with superior tolerability compared to iron salts. Similarly, a 2025 randomized trial in pediatric patients showed significant hemoglobin elevations with oral lactoferrin, achieving target levels in over 80% of cases versus around 50% with traditional iron therapies, alongside higher overall compliance rates of 93% for lactoferrin compared to 77% for ferrous sulfate in related studies. Lactoferrin's safety profile is favorable, with no reported risk of iron overload due to its high-affinity binding that regulates iron release and prevents free iron accumulation in tissues. This controlled delivery contrasts with the potential for oxidative stress from unbound iron in salt-based supplements, positioning lactoferrin as a reliable option for anemia management without long-term toxicity concerns.

Gastrointestinal and inflammatory diseases

Lactoferrin has demonstrated protective effects against necrotizing enterocolitis (NEC) in preterm infants, a severe gastrointestinal condition characterized by intestinal inflammation and necrosis. Clinical trials and meta-analyses from 2020 onward indicate that enteral supplementation with bovine lactoferrin at a dose of 100 mg/kg/day has been associated with potential reductions in the incidence of NEC, though evidence from meta-analyses indicates limited and non-significant effects for lactoferrin alone (e.g., RR 0.68, 95% CI 0.30-1.52); benefits are more consistent when combined with , with relative risk reductions ranging from 30% to 50% compared to placebo or standard care. This benefit is attributed to lactoferrin's antimicrobial and immunomodulatory properties, which help mitigate gut and inflammation in vulnerable neonates, though intravenous administration shows similar efficacy in some studies. In cystic fibrosis (CF), a genetic disorder affecting the gastrointestinal tract through impaired mucus clearance and chronic infections, lactoferrin plays a role in modulating intestinal inflammation and infection susceptibility. It contributes to reducing bacterial overgrowth in the gut by binding iron and disrupting microbial biofilms, thereby indirectly alleviating infection-related complications in the CF intestine. Elevated fecal lactoferrin levels serve as a reliable biomarker for detecting intestinal inflammation in CF patients, with concentrations above normal ranges (typically >7.25 μg/g) correlating with active mucosal inflammation and dysbiosis. While direct evidence on lactoferrin's impact on gastrointestinal mucus viscosity in CF is limited, its anti-inflammatory actions support overall gut homeostasis in this population. Lactoferrin exhibits potent anti-inflammatory effects in models of (IBD), including and , by suppressing key proinflammatory cytokines and enhancing gut barrier function. In dextran sulfate sodium-induced mouse models, bovine lactoferrin administration significantly downregulates the expression of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in colonic tissue, reducing histological scores. Furthermore, it promotes intestinal barrier integrity by upregulating tight junction proteins such as claudin-1, , and zonula occludens-1 (ZO-1), which helps prevent epithelial permeability and translocation of pathogens. These mechanisms position lactoferrin as a supportive therapeutic agent in IBD management, complementing its roles without overlapping into iron repletion strategies. Lactoferrin shows promise in the eradication of , a bacterium implicated in chronic and peptic ulcers, through synergistic interactions with standard regimens. When added to levofloxacin-based triple therapy, bovine lactoferrin enhances eradication rates from approximately 70% to over 85% in clinical trials, by inhibiting bacterial adhesion and formation while potentiating efficacy against resistant strains. This combination approach reduces treatment failures and supports mucosal healing in H. pylori-associated gastrointestinal inflammation.

Anticancer potential

Lactoferrin exhibits anticancer potential through multiple mechanisms, including the induction of in tumor cells and the suppression of vascular support for tumor growth. studies demonstrate that bovine lactoferrin promotes in human cell lines, such as HT-29, by activating caspases-3 and -9 at concentrations ranging from 50 to 200 μg/mL, leading to increased expression of pro-apoptotic proteins like BAX while downregulating anti-apoptotic BCL-2. This selective spares normal cells, highlighting lactoferrin's targeted action against malignant phenotypes. Another key mechanism involves inhibition of , where lactoferrin downregulates (VEGF) and its receptor VEGFR2, thereby limiting nutrient supply to tumors. Oral administration of bovine lactoferrin has been shown to systemically suppress VEGF-mediated in rat models, reducing vessel formation in response to tumor stimuli. In mouse models of colon cancer, lactoferrin treatment has been shown to inhibit by suppressing VEGF expression, correlating with reduced tumor volumes and microvessel density. Lactoferrin also enhances the efficacy of conventional chemotherapies by improving and sensitizing cancer cells. Conjugation of to bovine lactoferrin nanoparticles resulted in a fourfold increase in against cells ( of 0.2 μM versus 0.8 μM for free ), attributed to receptor-mediated uptake and amplified induction. Similarly, lactoferrin synergizes with in metastatic models, boosting antiproliferative effects by approximately 2.5-fold while mitigating toxicity. In preventive contexts, dietary supplementation with bovine lactoferrin has demonstrated chemopreventive effects in animal models of colon carcinogenesis. In azoxymethane-induced models, oral bovine lactoferrin at 0.2% of the diet reduced the incidence of aberrant crypt foci—precursors to colon tumors—by about 40%, alongside suppressing tumor multiplicity. Clinical evidence supports lactoferrin's translational potential, particularly in reducing side effects and aiding tumor control. A 2011 phase II of oral recombinant human lactoferrin (talactoferrin) in advanced non-small cell patients, when combined with standard regimens like and , suggested a potential in (median 7.0 vs. 4.2 months, not statistically significant) and a favorable safety profile with decreased adverse events compared to . A randomized in patients with existing colorectal polyps indicated that oral bovine lactoferrin (3 g/day) modestly inhibited polyp growth, with a -4.9% change in diameter overall (not significant) and up to -29.7% in female subgroups, suggesting potential chemopreventive effects. Ongoing research as of 2025 continues to explore its role in and cancers, building on preclinical synergies.

Diagnostic and therapeutic uses in infections

Lactoferrin serves as a valuable in the of various infections, particularly through its measurement in biological fluids. Elevated serum lactoferrin levels exceeding 200 ng/mL have been associated with systemic inflammatory responses in conditions like , reflecting activation and aiding in early detection. In gastrointestinal infections, fecal lactoferrin levels provide a non-invasive indicator of mucosal inflammation, with reported sensitivity around 75-93% for detecting active in inflammatory bowel conditions often linked to infections. For ocular infections, lactoferrin concentrations in can signal underlying pathology, as reduced levels correlate with compromised function and increased susceptibility to bacterial or viral invaders, supporting its use in . Standardized enzyme-linked immunosorbent assay () methods for quantifying lactoferrin in tears, serum, and other fluids have been refined and commercially available since the , enabling reliable with high specificity. Therapeutically, lactoferrin acts as an adjuvant in managing viral infections, notably in , where oral supplementation at doses around 200 mg daily has shown potential to reduce hospitalization risks by approximately 24% in meta-analyses of clinical trials as of 2025, likely by modulating immune responses and limiting viral replication. For infections, topical application of lactoferrin inhibits viral entry and plaque formation in ocular and mucosal tissues, demonstrating in preclinical models and early therapeutic studies. Emerging highlights lactoferrin's role as a therapeutic marker in arboviral infections; 2025 studies have identified elevated plasma lactoferrin as an indicator of activation in severe post-Zika dengue cases, suggesting its utility in monitoring disease progression and response to interventions.

Osteoporosis and bone health

Preclinical studies in animal models, including ovariectomized rats as a model for postmenopausal osteoporosis, have shown that lactoferrin promotes bone formation by stimulating osteoblast proliferation and differentiation, increases bone mineral density, and reduces bone resorption by inhibiting osteoclastogenesis. These effects suggest potential therapeutic benefits for osteopenia and osteoporosis. However, as of 2025, human clinical evidence remains markedly limited, with no large-scale randomized trials confirming efficacy or safety for bone health applications. Therefore, lactoferrin is not currently recommended as a treatment for osteoporosis.

Autoimmune diseases

There are no completed or ongoing clinical trials specifically evaluating lactoferrin as a treatment for autoimmune diseases. Lactoferrin has demonstrated immunomodulatory and anti-inflammatory properties in preclinical studies and some human trials focused on other conditions (e.g., infection, inflammation in the elderly, or COVID-19), but patients with autoimmune diseases are frequently excluded from these trials. Research suggests potential roles in regulating inflammation, but no human clinical evidence supports its use for autoimmune conditions.

Production and applications

Extraction methods

Lactoferrin is primarily extracted from natural sources such as bovine and , where it occurs at low concentrations. Early isolation methods in the 1980s utilized cation-exchange with CM-Sephadex resins to separate lactoferrin from acid , involving batch adsorption followed by with salt gradients at neutral pH. The most widely adopted technique remains cation-exchange chromatography applied to , leveraging lactoferrin's positive charge at acidic (around 3.5-4.0) for binding to sulfopropyl (SP) or carboxymethyl (CM) resins. is first clarified and adjusted to low , then loaded onto the column; lactoferrin is selectively eluted using a sodium chloride gradient in buffer at 7.0-7.7, achieving yields of 50-80% and purities exceeding 95% in optimized . Complementary methods, often combined with iron saturation to enhance selectivity, involve adjusting to 4.0-4.6 after adding ferric ions (e.g., FeCl3) to form holo-lactoferrin, which precipitates impurities while lactoferrin remains soluble or is recovered via subsequent acidification and . Membrane-based techniques, including and , serve as gentle pretreatment steps in milk processing to concentrate lactoferrin from without harsh chemicals, using membranes with 10-100 kDa cutoffs to retain the protein while removing smaller solutes and fats. These methods yield recoveries of 70-90% and integrate well with downstream , minimizing denaturation. Extraction faces challenges due to lactoferrin's low abundance, constituting approximately 0.1-0.2% of proteins in bovine sources, necessitating large volumes of starting material for commercial-scale production. Scalability is further limited by variability in composition, resin in , and the need for cost-effective purification to achieve food-grade purity.

Recombinant production

Recombinant production of lactoferrin utilizes biotechnological expression systems to achieve scalable yields while addressing limitations in natural extraction, such as low abundance in . Bacterial hosts like enable expression, with yields reaching up to 100-200 mg/L using vectors such as pET28a+, though the resulting protein is unglycosylated, potentially impacting its stability and compared to native forms. Fungal systems, particularly species, offer an advantage through mammalian-like N-glycosylation, which enhances and function; for instance, A. awamori has achieved yields up to 2 g/L with the pPLF-19 vector, while A. oryzae produces around 25 mg/L. Transgenic approaches in and animals provide eukaryotic and cost-effective biopharming. Since the 2000s, has been engineered for seed-specific expression, yielding 0.5–5.0 g/kg of dehusked via promoters like pAPI135, making it suitable for nutritional . In transgenic , mammary gland-targeted expression using vectors such as pBC1 results in yields of 1–3 g/L, with optimized lines reaching up to 16 g/L of bioactive recombinant human lactoferrin. Advances from 2023–2025 in plant-based production, including / editing for enhanced expression in crops like and novel platforms by companies such as Forte Protein, have improved scalability and purity for "plantibody"-like recombinant proteins, bridging agricultural and pharmaceutical applications. Purification of recombinant lactoferrin typically involves with His-tags incorporated via expression vectors like pET28a+, achieving high purity (>90%) but requiring optimization to resolve challenges in proper bond formation for folding and iron-binding site saturation, which are critical for and iron-sequestering functions. Iron incorporation often necessitates post-purification saturation under controlled conditions to mimic native holo-lactoferrin. Regulatory milestones include FDA GRAS status for recombinant bovine lactoferrin produced in systems like Komagataella phaffii, with the notice (GRN 1219) approved on May 7, 2025, affirming its safety for and supplement use.

Food, nutrition, and nanotechnology uses

Lactoferrin is incorporated into various products to enhance al value and functionality, particularly in infant formulas where it is added at concentrations typically ranging from 50 to 100 mg/L to mimic the levels found in human breast milk and support gut health. In production, lactoferrin supplementation promotes the growth of beneficial bacteria such as species by providing iron and modulating the intestinal , leading to improved probiotic viability and potential health benefits for consumers. Additionally, lactoferrin's properties help extend the shelf life of dairy and other perishable foods by inhibiting pathogens like , , and Salmonella typhimurium in a dose-dependent manner, with applications up to 20 ppm demonstrating extended storage stability without compromising sensory qualities. In nutritional applications, lactoferrin is widely used as a to bolster immune function, with typical adult dosages of 200-400 mg per day showing benefits in reducing and enhancing immune cell activity, such as T-cell activation. Recent 2024 reviews confirm its safety profile, indicating no significant toxicity at doses up to 4.5 g per day, supported by clinical trials demonstrating tolerability in healthy adults without adverse effects on gastrointestinal or systemic health. However, while short-term use is well-established, gaps remain in understanding long-term dosing effects beyond several months, particularly in vulnerable populations. Advancements in have leveraged lactoferrin for nanoencapsulation in systems like liposomes and micelles to improve its stability against gastrointestinal degradation and enhance by 2-3 fold compared to free forms. These carriers protect lactoferrin during , facilitating targeted delivery and sustained release in the gut. In 2025 developments, lactoferrin-conjugated nanoparticles have enabled co-delivery of , a with properties, improving penetration and therapeutic efficacy in models of through enhanced and crossing of biological barriers. Regulatory bodies have endorsed lactoferrin's use in food and nutrition since 2012, with the European Union authorizing bovine lactoferrin as a novel food ingredient following EFSA evaluation (Commission Implementing Decision 2012/727/EU), and the FDA granting GRAS status for applications in infant formula and general foods, affirming its safety at proposed levels but emphasizing the need for further data on chronic high-dose consumption.

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