by Noelle Patno, PhD
Lactoferrin (LF) has been advocated by researchers1–3 as a potential method to prevent or treat COVID-19. These recent reviews promote a hypothesis that the natural, endogenous compound which has shown antiviral capabilities for other viruses including SARS-CoV may be effective against the SARS-CoV-2 virus as well. With over 70 years since the discovery of this glycoprotein, this iron-scavenging milk protein now deserves greater attention. The current literature demonstrates that LF has many anti-inflammatory, immunomodulatory, and even anticarcinogenic effects; what remains to be discovered is its specific activity against the pandemic virus of our times, SARS-CoV-2. A large body of in vitro evidence suggests that lactoferrin may have efficacy because of its ability to inhibit viruses and bind to viral surface receptors, which are related to SARS-CoV-2 mechanisms. Now is the time to discover more about this glycoprotein and its potential against SARS-CoV-2.
Mechanism of binding to heparan sulfate
A recent paper (published in Cell, November 2020) demonstrated that SARS-CoV-2 infection depends on attachment to cellular heparan sulfate (HS) and ACE2.4 While ACE2’s role was predicted in January5 and subsequently demonstrated in March,6 this revelation in November reveals the importance of HS as an essential factor in the virus’s attachment and entry to infect the cell. Heparan sulfate, a complex carbohydrate on almost every cell’s surface, is useful to the host to determine the cell’s response to stimuli such as metabolic or inflammatory stimuli and critically as part of immune functions.7 However, many viruses hijack HS to bind and depend on it for their infection. In vitro evidence supports this mechanism for other viruses including the Nipah and Hendra viruses;8 entrovirus 71, which is associated with hand foot mouth disease;9 enteroaggregative E. coli, which is a significant cause of diarrhea and foodborne outbreaks;10 rift valley fever virus;11 and human papillomavirus.12 This list overlaps with the list of pathogenic viruses that lactoferrin inhibits in vitro, which includes but is not limited to the following: herpes simplex virus, hepatitis B virus, hepatitis C virus (HCV), avian flu, enterovirus 71, Japanese encephalitis virus, respiratory syncytial virus, influenza A virus, parainfluenza virus, cytomegalovirus, poliovirus, rotavirus, and human immunodeficiency virus (HIV), with clinical evidence for enterovirus 71, HCV, norovirus, and rotavirus.2 With lactoferrin’s previous ability demonstrated to prevent the Japanese encephalitis virus,13 alphavirus,14 Toscana virus,15 dengue virus,16 and the SARS pseudovirus17 from entering cells through HS receptors and infecting the cells, then LF has the possibility of preventing SARS-CoV2 from entering cells as well.
Potential mechanisms by which LF might help against SARS-CoV-2 are therefore the following:1
- Prevent attachment to heparan sulfate receptors on the cell and inhibit viral entry4,13
- Prevent attachment to ACE2 and inhibit viral entry/infection of the cell18
- Prevent attachment to DC-SIGN, dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin receptor and thereby prevent infection of the cell3
- Prevent attachment and viral entry via other receptors17
- Inhibit viral replication15,19
- Decrease IL-6,20 which is part of the cytokine storm
Current clinical trials evaluating lactoferrin in COVID-19
The table below lists the current clinical trials on clinicaltrials.gov evaluating lactoferrin in COVID-19.
Three recent publications further suggest that lactoferrin may help against SARS-CoV-2:
- In vitro, bovine lactoferrin was able to decrease significantly the numbers of SARS-CoV-2-infected bronchial epithelial cell mimetics, the single compound mentioned in the abstract of the preprinted paper, and one of 17 dose-responsive compounds from a 1,425 library in a drug-repurposing high throughput screen19
- The completed randomized clinical study listed above, in 32 patients with confirmed COVID-19 by RT-PCR, showed an early clearance of the virus, recovery from symptoms, and statistically significant reduction in IL-6 , with additional in vitro and in silico support for lactoferrin’s ability to prevent cells from infection through preincubation as well as simulated binding of lactoferrin to the ACE2 receptor.18
- A 10-day study evaluating the effect of a liposomal bovine lactoferrin syrup that included vitamin C alone or with zinc (for a total of 256 to 384 mg of lactoferrin per day) and additional nasal and mouth spray or aerosol application for additional symptoms. IgM/IgG antibody rapid test in whole blood was used for confirmed COVID-19 diagnosis in 75 people. Symptoms were scored on a scale of 0 to 3 in severity twice a day for 10 days and then a follow-up after one month. By the fifth day, all patients recovered from respiratory distress and headache symptoms. The percentage of patients without symptoms of coughing, muscular pain, nasal congestion, tiredness, and diarrhea all increased by 48 hours and 5 days after study start.21
There are many limitations to the above three studies. The first two preprinted articles have not been peer-reviewed. The third lacked clear dosing instructions, did not use the more accurate SARS-CoV-2 diagnostic tests; did not follow-up test for the virus after-treatment; used additional interventions for subsets of patients; lacked more rigorous, randomized, and controlled design and more objective and validated methodology; and was not the complete data set for the study, among other limitations. Clinical studies on the effects of lactoferrin supplementation in COVID-19 patients is a promising and interesting research advancement to watch.
- Campione E et al. Lactoferrin as protective natural barrier of respiratory and intestinal mucosa against coronavirus infection and inflammation. Int J Mol Sci. 2020;21(14):4903.
- Chang R et al. Lactoferrin as potential preventative and adjunct treatment for COVID-19. Int J Antimicrob Agents. 2020;56(3):106118.
- Wang Y et al. Lactoferrin for the treatment of COVID-19 (Review). Exp Ther Med. 2020;20(6).
- Clausen TM et al. SARS-CoV-2 infection depends on cellular heparan sulfate and ACE2. Cell. 2020;183(4):1043-1057.e15.
- Wan Y et al. Receptor recognition by the novel coronavirus from Wuhan: an analysis based on decade-long structural studies of SARS coronavirus. J Virol. 2020;94(7).
- Hoffmann M et al. SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor. Cell. 2020;181(2):271-280.e8.
- Simon Davis DA et al. Heparan sulfate: a ubiquitous glycosaminoglycan with multiple roles in immunity. Front Immunol. 2013;4.
- Mathieu C et al. Heparan sulfate-dependent enhancement of henipavirus infection. mBio. 2015;6(2).
- Kobayashi K et al. Heparan sulfate attachment receptor is a major selection factor for attenuated enterovirus 71 mutants during cell culture adaptation. PLOS Pathogens. 2020;16(3):e1008428.
- Rajan A et al. Enteroaggregative E. coli adherence to human heparan sulfate proteoglycans drives segment and host specific tesponses to infection. PLOS Pathogens. 2020;16(9):e1008851.
- de Boer SM et al. Heparan sulfate facilitates Rift Valley fever virus entry into the cell. J Virol. 2012;86(24):13767-13771.
- Selinka H-C et al. Inhibition of transfer to secondary receptors by heparan sulfate-binding drug or antibody induces noninfectious uptake of human papillomavirus. J Virol. 2007;81(20):10970-10980.
- Chien Y-J et al. Bovine lactoferrin inhibits Japanese encephalitis virus by binding to heparan sulfate and receptor for low density lipoprotein. Virology. 2008;379(1):143-151.
- Waarts B-L et al. Antiviral activity of human lactoferrin: inhibition of alphavirus interaction with heparan sulfate. Virology. 2005;333(2):284-292.
- Pietrantoni A et al. Bovine lactoferrin inhibits Toscana virus infection by binding to heparan sulphate. Viruses. 2015;7(2):480-495.
- Chen J-M et al. Bovine lactoferrin inhibits dengue virus infectivity by interacting with heparan sulfate, low-density lipoprotein receptor, and DC-SIGN. Int J Mol Sci. 2017;18(9).
- Lang J et al. Inhibition of SARS pseudovirus cell entry by lactoferrin binding to heparan sulfate proteoglycans. PLoS One. 2011;6(8). doi:10.1371/journal.pone.0023710
- Campione E et al. Pleiotropic effect of Lactoferrin in the prevention and treatment of COVID-19 infection: randomized clinical trial, in vitro and in silico preliminary evidences. bioRxiv. Published online August 17, 2020:2020.08.11.244996.
- Mirabelli C et al. Morphological cell profiling of SARS-CoV-2 infection identifies drug repurposing candidates for COVID-19. bioRxiv. Published online September 28, 2020.
- Lepanto MS et al. Efficacy of lactoferrin oral administration in the treatment of anemia and anemia of inflammation in pregnant and non-pregnant women: an interventional study. Front Immunol. 2018;9.
- Serrano G et al. Liposomal lactoferrin as potential preventative and cure for COVID-19. Int J Res Health Sci. 2020;8(1):8.
Noelle Patno, PhD received her PhD in Molecular Metabolism and Nutrition and Masters in Translational Science from the University of Chicago, studying the role of microbial components in intestinal epithelial cell survival related to inflammatory bowel disease. Prior to her graduate studies, Dr. Patno received a chemical engineering degree from Stanford University and worked as an engineer. She has personal experience and interest in preventive nutrition and nutritional therapies for chronic disease, and her current role involves researching and developing probiotics, prebiotics, and other nutritional programs for the promotion of digestive and overall health.