Study: Biosynthetic proteins targeting the SARS-CoV-2 spike as anti-virals. Image Credit: Naeblys/Shutterstock

Artificial proteins as specific and versatile neutralizing binders targeting the SARS-CoV-2 . peak

In a recent article posted on the bioRxiv* preprint server, researchers have shown that the biosynthetic proteins called αReps that target severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein may be novel SARS-CoV-2 antivirals

Study: Biosynthetic proteins targeting the SARS-CoV-2 peak as antiviral agents† Image Credit: Naeblys/Shutterstock


The 2019 CoV disease catastrophe (COVID-19), which resulted in approximately six million deaths worldwide in about two years, has highlighted the need to better understand and combat the transmission and emergence of respiratory viruses. This information will help develop more effective antiviral techniques to tackle future pandemics and epidemics.

SARS-CoV-2S binds to angiotensin-converting enzyme 2 (ACE2) receptors in hosts, allowing the virus to enter the cell. Thus, one potential technique for developing antivirals against COVID-19 is to address this interaction.

About the study

In the current work, the researchers wanted to identify ligands that block the SARS-CoV-2-ACE2 interaction. They wanted to develop low-cost, stable antivirals for COVID-19 that could be easily modified against the emerging SARS-CoV-2 variants.

The team identified candidates that recognized the SARS-CoV-2 S receptor binding domain (RBD). To do this, they screened a phage display library of biosynthetic protein sequences built on rigid -helicoidal huntingtin, elongation factor 3 (EF3), protein phosphatase 2A (PP2A), and the yeast kinase target of rapamycin 1 (TOR1) (HEAT)-like scaffold called αReps. .

Competitive binding assays were performed among the Reps to analyze their mechanism of SARS-CoV-2 neutralizations. Furthermore, the researchers showed how αRep bioengineering could stimulate the neutralizing effect of SARS-CoV-2 using a multivalent form. In addition, they assessed the SARS-CoV-2 neutralizing ability of these “Reps” in vitro and in vivo


The study results indicated that of the analyzed artificial proteins, two, namely C2 and F9, bind the SARS-CoV-2 RBD with nanometer affinities, showing a neutralizing effect. in vitro and identifying different sites where F9 spans the ACE2 binding motif. The authors found that C2 and F9 significantly inhibited SARS-CoV-2 entry into the cultured cells. These two compounds neutralized the virus through different pathways, with C2 attaching to a location remote from the receptor binding motif of ACE2, while F9 competes with ACE2 for RBD binding.

For neutralization of SARS-CoV-2, a trivalent αRep form called C2-foldon and the F9-C2 fusion protein had 0.1 nM affinities and a half-maximal effective concentration (EC50) of 8 to 18 nM. The homotrimeric C2 foldon and the F9-C2 heterodimer showed a more robust SARS-CoV-2 neutralization ability than the two parental αReps, with a half-maximal inhibitory concentration (IC50) ranging from 3 to 12 nM. In addition, virus entry at lower concentrations was prevented by assembled αReps via non-covalent or covalent linkages, with a 20-fold increase in activity for a trimeric αRep.

These αReps derivatives effectively neutralized the SARS-CoV-2 Omicron, δ, γ and variants. Notably, with EC50 values ​​ranging from 13 to 32 nM, F9-C2 or C2 foldon successfully neutralized SARS-CoV-2 mutants, such as Omicron and Delta variants.

Introduction of F9-C2 into the nasal cavity during or before SARS-CoV-2 infections significantly inhibited the multiplication of the viral strain with the D614G mutation in the hamster nasal epithelium. Viral titers in nasal swabs and the nasal cavity, the primary SARS-CoV-2 replication site, were reduced by this therapy, as were all inflammatory indicators of the infection. However, the treatment did not completely block SARS-CoV-2 infection in the nasal cavity.

Overall, the scientists reported that αReps represent a viable approach for COVID-19 therapies to target the nasal cavity and reduce viral spread in the proximal environment due to their substantial stability and effectiveness against SARS-CoV-2 variants.


In summary, the research findings showed that two biosynthetic protein sequences, namely C2 and F9, had a strong affinity for the SARS-CoV-2 RBD and effectively prevented the entry of SARS-CoV-2 into cultured cells (in vitro† The neutralizing EC50 values ​​were reduced to the 10 nM range by assembled αReps via non-covalent and covalent linkages. In addition, in the hamster model of SARS-CoV-2, introduction of a αRep dimer into the nasal cavity significantly reduced viral pathogenicity and replication. A C2 homotrimer and the F9-C2 fusion protein potently inhibited SARS-CoV-2 mutants, even the antigenically foreign Omicron variant.

Overall, the current study showed that the artificial proteins, αReps, could be developed into SARS-CoV-2 treatments targeting novel viral variants. Stable proteinaceous inhibitors, such as Reps and their derivatives, could be a promising option to threaten future pandemics associated with various emerging respiratory viruses following initiatives to stabilize them in the nasal cavity and technical improvement in binder selection.

*Important announcement

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, should guide clinical practice/health-related behavior, or be treated as established information.

Reference magazine:

  • Biosynthetic proteins targeting the SARS-CoV-2 peak as antiviral agents; Stephanie Thebault, Nathalie Lejal, Alexis Dogliani, Amelie Donchet, Agathe Urvoas, Marie Valerio-Lepiniec, Muriel Lavie, Cecile Baronti, Franck Touret, Bruno da Costa, Clara Bourgon, Audrey Fraysse, Audrey Saint-Albin-Deliot, Jessica Morel, Bernard Klonjkowski, Xavier de Lamballerie, Jean Dubuisson, Alain Roussel, Philippe Minard, Sophie Le Poder, Nicolas Meunier, Bernard Delmas. bioRxivdoi

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