Lactoferrin Binding to SARS-CoV-2 Spike Glycoprotein Blocks Pseudoviral Entry and Relieves Iron Protein Dysregulation in Several In Vitro Models

Abstract

SARS-CoV-2 causes COVID-19, a predominantly pulmonary disease characterized by a burst of pro-inflammatory cytokines and an increase in free iron. The viral glycoprotein Spike mediates fusion to the host cell membrane, but its role as a virulence factor is largely unknown. Recently, the antiviral activity of lactoferrin against SARS-CoV-2 was demonstrated in vitro and shown to occur via binding to cell surface receptors, and its putative interaction with Spike was suggested by in silico analyses. We investigated the anti-SARS-CoV-2 activity of bovine and human lactoferrins in epithelial and macrophagic cells using a Spike-decorated pseudovirus. Lactoferrin inhibited pseudoviral fusion and counteracted the deleterious effects of Spike on iron and inflammatory homeostasis by restoring basal levels of iron-handling proteins and of proinflammatory cytokines IL-1β and IL-6. Using pull-down assays, we experimentally proved for the first time that lactoferrin binds to Spike, immediately suggesting a mechanism for the observed effects. The contribution of transferrin receptor 1 to Spike-mediated cell fusion was also experimentally demonstrated. In silico analyses showed that lactoferrin interacts with transferrin receptor 1, suggesting a multifaceted mechanism of action for lactoferrin. Our results give hope for the use of bovine lactoferrin, already available as a nutraceutical, as an adjuvant to standard therapies in COVID-19.

Green synthesis, characterization, anti-SARS-CoV-2 entry, and replication of lactoferrin-coated zinc nanoparticles with halting lung fibrosis induced in adult male albino rats

“…They also demonstrated that hLF may bind the ACE2 receptor ectodomain with a high affinity without binding to the RBD 46 . In agreement with our findings, in-silico 48 and experimental studies 47 discovered that LF is a promising candidate for preventing SARS-CoV-2 infection due to its ability to bind to the RBD C-terminal domain. The outcomes of molecular docking between LF and various Spike variants clearly imply that single-point mutations in different SARS-CoV-2 variants do not affect LF’s capacity to interact with Spike.…”

“…The outcomes of molecular docking between LF and various Spike variants clearly imply that single-point mutations in different SARS-CoV-2 variants do not affect LF’s capacity to interact with Spike. This finding lends support to the use of LF in the early stages of SARS-CoV-2 infection 47 . The RdRp is essential enzyme that directly involved in RNA synthesis for SARS-CoV-2 virus.…”

“…The RBD of the SARS-CoV-2 viral spike glycoprotein interacts with human ACE2 with great affinity 46 . Spikes are the main virulent factor of SARS-CoV-2, and all research efforts have been directed at identifying compounds that can interact with Spike and therefore prevent SARS-CoV-2 infection 47 . The spike protein is a 1273-amino acid single-pass transmembrane protein with a transmembrane helix, a long N-terminal ectodomain exposed on the surface of the virus, and a short C-terminal tail on the inside of the virus.…”

Liposomal Lactoferrin Exerts Antiviral Activity against HCoV-229E and SARS-CoV-2 Pseudoviruses In Vitro

“…The mechanism of action of Lf against SARS-CoV-2 is also explained by its direct interaction with the receptor binding domain (RBD) of the Spike protein [30,31] and its binding to heparan sulfate proteoglycans, thus preventing the early attachment phase [14]. In addition, some in silico studies showed that Lf also interacts with the transferrin receptor 1, which can be an alternative co-receptor for SARS-CoV-2 entry [31,32].…”

Lactoferrins in Their Interactions with Molecular Targets: A Structure-Based Overview

“…In another study [ 122 ], computational analysis revealed the interaction between lactoferrin and transferrin receptor 1, indicating a diverse mechanism of action for lactoferrin. Protein-protein molecular docking simulations were carried out using the CLUSPRO method to explore the interaction between TfR1 and Lfs [ 123 ], considering in particular different variants of SARS-CoV-2.…”