PMID: 

PLoS One. 2011 ;6(8):e23710. Epub 2011 Aug 22. PMID: 21887302

Abstract Title: 

Inhibition of SARS pseudovirus cell entry by lactoferrin binding to heparan sulfate proteoglycans.

Abstract: 

It has been reported that lactoferrin (LF) participates in the host immune response against Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) invasion by enhancing NK cell activity and stimulating neutrophil aggregation and adhesion. We further investigated the role of LF in the entry of SARS pseudovirus into HEK293E/ACE2-Myc cells. Our results reveal that LF inhibits SARS pseudovirus infection in a dose-dependent manner. Further analysis suggested that LF was able to block the binding of spike protein to host cells at 4°C, indicating that LF exerted its inhibitory function at the viral attachment stage. However, LF did not disrupt the interaction of spike protein with angiotensin-converting enzyme 2 (ACE2), the functional receptor of SARS-CoV. Previous studies have shown that LF colocalizes with the widely distributed cell-surface heparan sulfate proteoglycans (HSPGs). Our experiments have also confirmed this conclusion. Treatment of the cells with heparinase or exogenous heparin prevented binding of spike protein to host cells and inhibited SARS pseudovirus infection, demonstrating that HSPGs provide the binding sites for SARS-CoV invasion at the early attachment phase. Taken together, our results suggest that, in addition to ACE2, HSPGs are essential cell-surface molecules involved in SARS-CoV cell entry. LF may play a protective role in host defense against SARS-CoV infection through binding to HSPGs and blocking the preliminary interaction between SARS-CoV and host cells. Our findings may provide further understanding of SARS-CoV pathogenesis and aid in treatment of this deadly disease.

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PMID: 

J Virol. 2005 Mar ;79(5):3009-15. PMID: 15709021

Abstract Title: 

Lactoferrin prevents dendritic cell-mediated human immunodeficiency virus type 1 transmission by blocking the DC-SIGN–gp120 interaction.

Abstract: 

One of the cell types first encountered by human immunodeficiency virus type 1 (HIV-1) following sexual transmission are dendritic cells (DC). DC capture HIV-1 through C-type lectin receptors, of which the best studied example is DC-SIGN, which mediates HIV-1 internalization. DC can keep the virus infectious for several days and are able to transmit HIV-1 to CD4(+) T cells. We tested proteins from milk and serum for their ability to block DC-mediated HIV-1 transmission, of which bovine lactoferrin (bLF) is the most potent inhibitor. bLF binds strongly to DC-SIGN, thus preventing virus capture and subsequent transmission. Interestingly, bLF is a much more efficient inhibitor of transmission than human lactoferrin. Since bLF is nontoxic and easy to purify in large quantities, it is an interesting candidate microbicide against HIV-1. Another advantage of bLF is its ability to block HIV-1 replication in T cells. DC-mediated capture of a bLF-resistant HIV-1 variant that was selected during long-term culturing in T cells could still be blocked by bLF. This underscores the usefulness of bLF as a microbicide drug to prevent HIV-1 transmission.

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PMID: 

Antiviral Res. 2004 Sep ;63(3):197-208. PMID: 15451188

Abstract Title: 

Inhibition of cytomegalovirus infection by lactoferrin in vitro and in vivo.

Abstract: 

Lactoferrin is an antimicrobial agent, that, amongst other viruses, inhibits cytomegalovirus (CMV). In this study, we addressed the mechanism(s) by which lactoferrin interacts with CMV and its target cells to inhibit infection. We also studied the antiviral activity of lactoferrin in vivo in rat CMV models with and without immune suppression. We cationized a protein of similar molecular weight, i.e. human serum albumin (HSA), as well as a protein with a smaller molecular weight (beta-lactoglobulin). While HSA itself displayed no anti-CMV activity in vitro, cationic HSA inhibited CMV replication to a similar extent as lactoferrin. Time-of-addition assays indicated that all cationic proteins interacted with an early event in the infection and pre-incubation of cells rather than of virus significantly reduced CMV replication. Rats were treated with lactoferrin (4, 40 or 160 mg/kg, intravenously), beginning at 6h after CMV administration. Subsequently, the rats were treated three times a week. As a positive control, CMV-infected rats were treated with cidofovir, and this agent proved to be highly active in the rat models for CMV. Treatment with lactoferrin was beneficial when infection was initiated with cell-free virus, but not with virus-infected leukocytes. Lactoferrin treatment led to a 10-fold reduction in the final virus titers (salivary glands) at 4 weeks after infection in the immunocompromised rats. Lactoferrin exerted its effects via inhibition of cell entry rather than via stimulation of the immune system.

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PMID: 

Virology. 2008 Sep 15 ;379(1):143-51. Epub 2008 Jul 21. PMID: 18640695

Abstract Title: 

Bovine lactoferrin inhibits Japanese encephalitis virus by binding to heparan sulfate and receptor for low density lipoprotein.

Abstract: 

Lactoferrin is a natural anti-microbial protein which affects Japanese encephalitis virus (JEV) activity. Binding of lactoferrin to cell surface expressed heparan sulfate (HS), one possible receptor for JEV, has been postulated to be the possible mechanism of anti-JEV antiviral activity. In this study, we evaluate the effects of bovine lactoferrin (bLF) against JEV infection in vitro, using both wild-type (WT) and laboratory-adapted strains. bLF inhibited the infectivity of all the JEV strains tested. In particular the infectivity of the HS-adapted JEV strains was strongly reduced, whereas the non HS-adapted JEV strains were inhibited to lesser extent. Using both HS-adapted CJN-S1 and non HS-adapted CJN-L1 viruses, the results showed that bLF inhibited the early events essential to initiate JEV infection, which includes blocking virus attachment to cellular membranes and reducing viral penetration. This anti-JEV activity was the highest using HS-adapted CJN-S1 strain on HS-expressed CHO-K1 cells. Also, binding of bLF to heparin-sepharose blocked JEV binding; and soluble HS attenuated the anti-JEV activity of bLF. The results support the premise that the interaction of bLF with cell surface expressed glycosaminoglycans, in particular the highly sulfated HS, plays an essential role in the antiviral activity of bLF. However, bLF was functional in inhibiting CJN-S1 entry into HS-deficient CHO-pgsA745 cells, and bLF-treated CHO-K1 and -pgsA745 cells also prevented non HS-adapted CJN-L1 virus entry, indicating that a non-HS pathway may be involved in bLF inhibition of JEV entry. The low-density lipoprotein receptor (LDLR), possibly involved in the entry of several RNA viruses, also binds to bLF. We found that both rLDLR and anti-LDLR antibodies reduced the effectiveness of bLF inhibition of JEV infection. This finding provided evidence to suggest that cell surface-expressed LDLR may play a role in JEV infection, especially for non HS-adapted strains.

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PMID: 

Biometals. 2010 Jun ;23(3):465-75. Epub 2010 Mar 16. PMID: 20232110

Abstract Title: 

Bovine lactoferrin inhibits influenza A virus induced programmed cell death in vitro.

Abstract: 

Influenza is one of the main plagues worldwide. The statistical likelihood of a new pandemic outbreak, together with the alarming emergence of influenza virus strains that are resistant to available antiviral medications, highlights the need for new antiviral drugs. Lactoferrin, a 80 kDa bi-globular iron-binding glycoprotein, is a pleiotropic factor with potent antimicrobial and immunomodulatory activities. Although the antiviral effect of lactoferrin is one of its major biological functions, the mechanism of action is still under debate. In this research, we have analyzed the effect of bovine lactoferrin (bLf) on Influenza A virus infection in vitro. Our results showed that (i) Influenza virus infected cells died as a result of apoptosis, (ii) bLf treatment inhibited programmed cell death by interfering with function of caspase 3, a major virus-induced apoptosis effector, and (iii) bLf efficiently blocked nuclear export of viral ribonucleoproteins so preventing viral assembly. These results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of Influenza virus infection.

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PMID: 

Virology. 2004 Jan 5 ;318(1):405-13. PMID: 14972565

Abstract Title: 

Inhibition of herpes simplex virus infection by lactoferrin is dependent on interference with the virus binding to glycosaminoglycans.

Abstract: 

Previous reports have indicated that lactoferrin inhibits herpes simplex virus (HSV) infection during the very early phases of the viral replicative cycle. In the present work we investigated the mechanism of the antiviral activity of lactoferrin in mutant glycosaminoglycan (GAG)-deficient cells. Bovine lactoferrin (BLf) was a strong inhibitor of HSV-1 infection in cells expressing either heparan sulfate (HS) or chondroitin sulfate (CS) or both, but was ineffective or less efficient in GAG-deficient cells or in cells treated with GAG-degrading enzymes. In contrast to wild-type HSV-1, virus mutants devoid of glycoprotein C (gC) were significantly less inhibited by lactoferrin in GAG-expressing cells, indicating that lactoferrin interfered with the binding of viral gC to cell surface HS and/or CS. Finally, we demonstrated that lactoferrin bound directly to both HS and CS isolated from surfaces of the studied cells, as well as to commercial preparations of GAG chains. The results support the hypothesis that the inhibition of HSV-1 infectivity by lactoferrin is dependent on its interaction with cell surface GAG chains of HS and CS.

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PMID: 

Cell Mol Life Sci. 2005 Dec ;62(24):3002-13. PMID: 16261265

Abstract Title: 

Anti herpes simplex virus activity of lactoferrin/lactoferricin — an example of antiviral activity of antimicrobial protein/peptide.

Abstract: 

One of the most common viral infections in humans is caused by the herpes simplex virus (HSV). It was first effectively treated in the 1970s with the introduction of acyclovir, which is still the most commonly used treatment. Naturally occurring antimicrobial proteins and peptides have also been shown to possess antiviral activity against HSV. This review will focus on the anti-HSV activity of one such protein, lactoferrin, and a small peptide fragment from its N-terminal domain, lactoferricin. Both components have been shown to effectively block entry of HSV into the host cell. In addition to blocking HSV entry, the peptides appear to have immune stimulatory activity, although this is still somewhat controversial. Mode of action studies and knowledge about the anti-HSV activity of lactoferricin have also been successfully employed in the design of new, more specific HSV blockers.

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PMID: 

C R Biol. 2014 Oct ;337(10):581-95. Epub 2014 Sep 22. PMID: 25282173

Abstract Title: 

Potential lactoferrin activity against pathogenic viruses.

Abstract: 

Lactoferrin (LF) is an 80-kDa globular glycoprotein with high affinity for metal ions, particularly for iron. This protein possesses many biological functions, including the binding and release of iron and serves as one of the important components of the innate immune system, where it acts as a potent inhibitor of several pathogens. LF has efficacious antibacterial and antiviral activities against a wide range of Gram-positive and Gram-negative bacteria and against both naked and enveloped DNA and RNA viruses. In its antiviral pursuit, LF acts predominantly at the acute phase of the viral infection or even at the intracellular stage, as in hepatitis C virus infection. LF inhibits the entry of viral particles into host cells, either by direct attachment to the viral particles or by blocking their cellular receptors. This wide range of activities may be attributed to the capacity of LF to bind iron and its ability to interfere with the cellular receptors of both hosts and pathogenic microbes.

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PMID: 

J Gen Virol. 2017 Jul ;98(7):1749-1754. Epub 2017 Jul 12. PMID: 28699858

Abstract Title: 

Bovine lactoferrin activity against Chikungunya and Zika viruses.

Abstract: 

Chikungunya (CHIKV) and Zika (ZIKV) viruses are arboviruses which have recently broken their sylvatic isolation and gone on to spread rampantly among humans in some urban areas of the world, especially in Latin America. Given the lack of effective interventions against such viruses, the aim of this work was to evaluate the antiviral potential of bovine lactoferrin (bLf) in their infections. Through viability, plaque, immunofluorescence and nucleic acid quantification assays, our data show that bLf exerts a dose-dependent strong inhibitory effect on the infection of Vero cells by the aforementioned arboviruses, reducing their infection efficiency by up to nearly 80 %, with no expressive cytotoxicity, and that such antiviral activity occurs at the levels of input and output of virus particles. These findings reveal that bLf antimicrobial properties are extendable to CHIKV and ZIKV, underlining a generic inhibition mechanism that can be explored to develop a potential strategy against their infections.

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PMID: 

Int J Mol Sci. 2017 Sep 12 ;18(9). Epub 2017 Sep 12. PMID: 28895925

Abstract Title: 

Bovine Lactoferrin Inhibits Dengue Virus Infectivity by Interacting with Heparan Sulfate, Low-Density Lipoprotein Receptor, and DC-SIGN.

Abstract: 

Bovine lactoferrin (bLF) presents in milk and has been shown to inhibit several viral infections. Effective drugs are unavailable for the treatment of dengue virus (DENV) infection. In this study, we evaluated the antiviral effect of bLF against DENV infection in vivo and in vitro. Bovine LF significantly inhibited the infection of the four serotypes of DENV in Vero cells. In the time-of-drug addition test, DENV-2 infection was remarkably inhibited when bLF was added during or prior to the occurrence of virus attachment. We also revealed that bovine LF blocks binding between DENV-2 and the cellular membrane by interacting with heparan sulfate (HS), dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN), and low-density lipoprotein receptors (LDLR). In addition, bLF inhibits DENV-2 infection and decreases morbidity in a suckling mouse challenge model. This study supports the finding that bLF may inhibit DENV infection by binding to the potential DENV receptors.

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