Human Cathelicidin Inhibits SARS-CoV-2 Infection: Killing Two Birds with One Stone

Abstract

SARS-CoV-2 infection begins with the association of its spike 1 (S1) protein with host angiotensin-converting enzyme-2 (ACE2). Targeting the interaction between S1 and ACE2 is a practical strategy against SARS-CoV-2 infection. Herein, we show encouraging results indicating that human cathelicidin LL37 can simultaneously block viral S1 and cloak ACE2. LL37 binds to the receptor-binding domain (RBD) of S1 with high affinity (11.2 nM) and decreases subsequent recruitment of ACE2. Owing to the RBD blockade, LL37 inhibits SARS-CoV-2 S pseudovirion infection, with a half-maximal inhibitory concentration of 4.74 μg/mL. Interestingly, LL37 also binds to ACE2 with an affinity of 25.5 nM and cloaks the ligand-binding domain (LBD), thereby decreasing S1 adherence and protecting cells against pseudovirion infection in vitro . Intranasal administration of LL37 to C57 mice infected with adenovirus expressing human ACE2 either before or after pseudovirion invasion decreased lung infection. The study identified a versatile antimicrobial peptide in humans as an inhibitor of SARS-CoV-2 attachment using dual mechanisms, thus providing a potential candidate for coronavirus disease 2019 (COVID-19) prevention and treatment.

Ramping Up Antimicrobial Peptides Against Severe Acute Respiratory Syndrome Coronavirus-2

“…Recent in silico molecular docking studies predicted strong binding interactions of LL-37 (Lokhande et al, 2020) and hBD-2 (Zhang L et al, 2021) with the receptor-binding domain (RBD) of SARS-CoV-2, suggesting an RBD blocking potential for these two peptides. Biophysical assays using bio-layer interferometry (BLI) and microscale thermophoresis (MST) supported the in silico findings for LL-37 (Wang C. et al, 2021) and hBD-2 (Zhang L. •Aggregates IAV and enhances neutrophil-mediated clearance [Hartshorn et al (2006), Tecle et al (2007), Doss et al (2009)] •Inhibits IAV replication through the inhibition of protein kinase C (PKC) in infected cells [Salvatore et al (2007)] HD5…”

“…Additionally, biochemical studies with hBD-2 showed that it inhibited the RBD from binding ACE2 and prevented S protein-expressing pseudovirions from infecting ACE2-expressing human cells (Zhang L. et al, 2021). Interestingly, LL-37 has been found to suppress S pseudovirion infection in a dose-dependent manner with an IC 50 value of 1.05 μM (Wang C. et al, 2021). By using a clever in vivo model that incorporated ACE2-expressing adenovirions, either with or without S protein-expressing pseudovirions, Wang J. et al (2021) were able to show that intranasal administration of LL-37 protected mice from pulmonary infection (Wang C. et al, 2021).…”

“…Interestingly, LL-37 has been found to suppress S pseudovirion infection in a dose-dependent manner with an IC 50 value of 1.05 μM (Wang C. et al, 2021). By using a clever in vivo model that incorporated ACE2-expressing adenovirions, either with or without S protein-expressing pseudovirions, Wang J. et al (2021) were able to show that intranasal administration of LL-37 protected mice from pulmonary infection (Wang C. et al, 2021). This is the first demonstration of a natural AMP that can inhibit CoV-2 entry via a dual mechanism.…”

“…FIGURE 1 | Schematic representation showing differential binding of human AMPs to SARS-CoV-2 S protein or ACE2 on cell surfaces. LL-37 and hBD-2 bind to SARS-CoV-2 S protein and inhibit its binding to ACE2 on the cell surface prior to entry(Lokhande et al, 2020;Roth et al, 2020;Wang C. et al, 2021;Zhang L. et al, 2021). In contrast, HD-5 binds to ACE2 to inhibit viral entry(Wang et al, 2020a) [LL-37 has also been shown to bind ACE2, however, with lower affinity than S-RBD(Wang C. et al, 2021)].…”

A Fungal Defensin Targets the SARS−CoV−2 Spike Receptor−Binding Domain

“…For example, human β−defensin 2 (hBD−2), an epithelial cell−derived AMP, binds to RBD with a K D of ~300 nM [ 17 ]. Human intestinal α−defensin 5 (HD−5) and LL37 can simultaneously attach both ACE2 and the Spike protein [ 18 , 19 , 20 ]. A defensin−like peptide P9R exhibited potent antiviral activity against multiple viruses including SARS−CoV−2.…”