Carbohydrate-binding protein from stinging nettle as fusion inhibitor for SARS-CoV-2 variants of concern

Abstract

Urtica dioica agglutinin (UDA) is a carbohydrate-binding small monomeric protein isolated from stinging nettle rhizomes. It inhibits replication of a broad range of viruses, including coronaviruses, in multiple cell types, with appealing selectivity. In this work, we investigated the potential of UDA as a broad-spectrum antiviral agent against SARS-CoV-2. UDA potently blocks transduction of pseudotyped SARS-CoV-2 in A549.ACE2+-TMPRSS2 cells, with IC50 values ranging from 0.32 to 1.22 µM. Furthermore, UDA prevents viral replication of the early Wuhan-Hu-1 strain in Vero E6 cells (IC50 = 225 nM), but also the replication of SARS-CoV-2 variants of concern, including Alpha, Beta and Gamma (IC50 ranging from 115 to 171 nM). In addition, UDA exerts antiviral activity against the latest circulating Delta and Omicron variant in U87.ACE2+ cells (IC50 values are 1.6 and 0.9 µM, respectively). Importantly, when tested in Air-Liquid Interface (ALI) primary lung epithelial cell cultures, UDA preserves antiviral activity against SARS-CoV-2 (20A.EU2 variant) in the nanomolar range. Surface plasmon resonance (SPR) studies demonstrated a concentration-dependent binding of UDA to the viral spike protein of SARS-CoV-2, suggesting interference of UDA with cell attachment or subsequent virus entry. Moreover, in additional mechanistic studies with cell-cell fusion assays, UDA inhibited SARS-CoV-2 spike protein-mediated membrane fusion. Finally, pseudotyped SARS-CoV-2 mutants with N-glycosylation deletions in the S2 subunit of the spike protein remained sensitive to the antiviral activity of UDA. In conclusion, our data establish UDA as a potent fusion inhibitor for the current variants of SARS-CoV-2.

Irreversible Inactivation of SARS-CoV-2 by Lectin Engagement with Two Glycan Clusters on the Spike Protein

“…On this basis, it may be proposed that multivalent targeting of key glycans on SARS-CoV-2 Spike improves the chances of avoiding facile mutational escape by the virus. Indeed, the substantial breadth of lectin antiviral effects observed in this current work and elsewhere (16,(51)(52)(53)(54)(55) for variants of SARS-CoV-2 supports this expectation. Furthermore, the antiviral effects observed with a fully infectious coronavirus that is not in the SARS-CoV-2 line argues for a potential broad spectrum anti-coronavirus activity as has been previously reported for GRFT in an investigation of its activity against SARS-CoV-1 (56).…”

TheUrtica DioicaAgglutinin Prevents Rabies Virus Infection in a Muscle Explant Model

“…Lectins are characterized by their reversible binding to a specific mono-or oligosaccharide [25]. Several lectins have been reported to exert anti-bacterial and antiviral activities [13,14,26] and some lectins have been shown to elicit antiviral activity by binding with viral glycans of enveloped viruses [15][16][17][18][19] such as HIV and SARS-CoV2. Here, in contrast, we found that the mechanism by which UDA inhibits RABV infection stems primarily from an interaction with the host cells.…”

“…HHA, a mannose specific lectin from Hippeastrum Hybrid has been reported to inhibit SARS-CoV at the stage of viral attachment and fusion [18]. UDA, a N-acetylglucosamine specific lectin from Urtica dioica inhibits SARS-CoV-2 infection of cells by binding to the spike protein [19]. Some lectins were shown to reduce infection of cells with the RABV [20,21].…”

Cellular electrical impedance to profile SARS-CoV-2 fusion inhibitors and to assess the fusogenic potential of spike mutants

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“…In previous studies (23,24), we demonstrated that SARS-CoV-2 viral entry can be mimicked by a cell-cell fusion system in which acceptor cells express the cellular human ACE2 receptor and donor cells the complementary viral spike protein. In our current work, the lung epithelial cell line A549 (stably transduced with human ACE2 to elevate the endogenous receptor level) was chosen as acceptor cell, whereas spiketransfected HEK293T cells were selected as donor cells because of the high plasmid transfection efficiency of the latter.…”