Blockade of TMPRSS2-mediated priming of SARS-CoV-2 by lactoferricin

Abstract

In addition to vaccines, there is an urgent need for supplemental antiviral therapeutics to dampen the persistent COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The transmembrane protease serine 2 (TMPRSS2), that is responsible for proteolytic priming of the SARS-CoV-2 spike protein, appears as a rational therapeutic target. Accordingly, selective inhibitors of TMPRSS2 represent potential tools for prevention and treatment of COVID-19. Previously, we identified the human milk glycoprotein lactoferrin as a natural inhibitor of plasminogen conversion to plasmin, a serine protease homologous to TMPRSS2. Here, we tested whether lactoferrin and lactoferricin, a biologically active natural peptide produced by pepsin-mediated digestion of lactoferrin, together with synthetic peptides derived from lactoferrin, were able to block TMPRSS2 and SARS-CoV-2 infection. Particularly, we revealed that both lactoferricin and the N-terminal synthetic peptide pLF1 significantly inhibited: i) proteolytic activity of TMPRSS2 and plasmin, ii) proteolytic processing of the SARS-CoV-2 spike protein, and iii) SARS-CoV-2 infection of SARS-CoV-2-permissive cells. Thus, natural and synthetic peptides derived from lactoferrin represent feasible candidates for supporting prevention and treatment of COVID-19.

Importance, Applications and Features of Assays Measuring SARS-CoV-2 Neutralizing Antibodies

“…MNT coupled to in-cell ELISA was found to be equally sensitive to PRNT in evaluating NAbs in tested sera [ 69 ], and neutralization titers determined by MNT significantly correlated with S protein-binding antibody titers determined by standard ELISA [ 68 , 70 ]. Since MNT uses an authentic virus that can undergo several replication cycles, the assay can be easily adapted to measure the inhibitory effect of various antiviral drugs or inhibitors of pathways that are employed by the virus for cell entry, replication or egress [ 67 , 69 , 71 , 72 , 73 , 74 , 75 ].…”

S Protein, ACE2 and Host Cell Proteases in SARS-CoV-2 Cell Entry and Infectivity; Is Soluble ACE2 a Two Blade Sword? A Narrative Review

“…For any route of the virus entry, the importance of the proteolytic destabilizing cleavage of S1/S2 junction (see Section 3 , gaining U from D states in RBDs) and subsequent proteases-induced transition of S2 subunit to fusogenic configuration should be emphasized [ 66 ]. In silico and cell culture studies showed peptidomimetic binding compounds as well as lactoferricin and lactoferrin hinder the infectivity of SARS-CoV-2 significantly through inhibition of TMPRSS2-induced priming of S protein [ 67 , 68 ]. However, a recent study on HEK293T cells revealed that both TMPRSS2 and metalloproteases, particularly ADAM17, individually or co-operatively, promote activation of S2′ segment of S protein and syncytia formation in infection by SARS-CoV-2 and its emerging variants of concern [ 69 ].…”

S protein, ACE2 and Host Cell Proteases in SARS-CoV2 Cell Entry and Infectivity; Is Soluble ACE2 a Two Blade Sword?

“…For any route of the virus entry, the importance of the proteolytic destabilizing cleavage of S1/S2 junction (see above, gaining U from D states in RBDs) and subsequent proteases-induced transition of S2 subunit to fusogenic configuration should be emphasized [59]. In Silico and cell culture studies showed peptidomimetic binding compounds as well as lactoferricin and lactoferrin hinder the infectivity of SARS-CoV2 significantly through inhibition of TMPRSS2-induced priming of S protein [60,61]. However, a recent study on HEK293T cells revealed that both TMPRSS2 and metalloproteases, particularly ADAM17, individually or co-operatively, promote activation of S2' segment of S protein and syncytia formation in infection by SARS-CoV2 and its emerging variants of concern [62].…”