In a recent study published in PLoS ONE, researchers explored the activity of angiotensin-converting enzyme-2 (ACE2) decoy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant.

Study: High activity of an affinity-matured ACE2 decoy against Omicron SARS-CoV-2 and pre-emergent coronaviruses. Image Credit: Kateryna Kon/Shutterstock

Background

The effectiveness of therapeutic monoclonal antibodies and vaccinations that focus on the spike protein is now gravely threatened by SARS-CoV-2 variants resembling Omicron BA.1 and Omicron BA.2. A big number of genetically different sarbecoviruses, including the pandemic viruses SARS-CoV-2 and SARS-CoV-1, have been produced in animal populations by viral evolution over a considerably longer duration. The present efforts to develop medications in anticipation of future pandemics just like the coronavirus disease 2019 (COVID-19) are complicated by the genetic variety and vast zoonotic potential of those viruses.

In regards to the study

In the current study, researchers discussed a technique of decoy-based therapy and passive protection to reduce the COVID-19 pandemic’s current threat and any future airway virus risks.

The team sought to find out whether our ACE2 decoy could neutralize newly arising SARS-CoV-2 strains. We first produced and purified the viral receptor-binding domains (RBDs), performing surface plasmon resonance binding evaluation to guage the binding between the CoV RBDs and decoy. The team looked for an RBD binding test that might enable us to guage the decoy compatibility of a big selection of viral variants. A yeast display system was employed to guage the binding of the decoy to several RBDs.

The researchers created budding yeast that exhibits viral RBDs as fusion proteins to the yeast protein Aga2, which is coupled to the surface of cells. After incubating the RBD yeast with the CDY14HL-Fc1 fusion protein, the certain decoy was stained with a fluorescent secondary antibody to measure decoy binding using flow cytometry.

The capability of CDY14HL to bind RBDs from quite a lot of coronaviruses with pandemic potential was then assessed. They found 23 sarbecoviruses isolated from bats in Asia, Africa, and Europe along with SARS-CoV-1 and SARS-CoV-2, a lot of that are suspected of employing ACE2 as a receptor. For the binding study, the study cloned artificial RBD genes into the yeast display format. Also, the genetically different RBD were added from the human coronavirus NL63, an Alpha-CoV that has been demonstrated to enter cells via ACE2. Flow cytometry was used to investigate the binding affinities of yeast-displayed RBD to CDY14HL-Fc1.

Results

The SARS-CoV-2 ancestral (Wuhan-Hu-1) RBD was certain by CDY14HL-Fc1 with an apparent affinity of 0.14 nM. For all VoC RBDs, CDY14HL retained sub-nanomolar binding affinity. This result agrees with CDY14HL’s widespread resistance to SARS-CoV-2 variant evolution previously noted in binding and pseudotype neutralization investigations. The Omicron BA.1 variant RBD differs from the unique strain by 15 amino acids, whereas the Omicron BA.2 variant RBD differs from the ancestral strain by 16 amino acids, in contrast to earlier variants which have one, two, or three RBD mutations.

First-generation vaccinations and nearly all of monoclonal antibodies created for therapeutic and passive prophylactic applications have lessened effectiveness attributable to this amount of mutation. In comparison with the ancestral RBD, the decoy-bound yeast exhibited Omicron RBDs a minimum of 4 times more tightly.

Omicron BA.1 and BA.2 were more effectively neutralized by CDY14HL-Fc1 than by the ancestor strain. We expanded this technique to cover six more variants, including Delta, Delta Plus, Kappa, Lambda, Mu, and Zeta. With IC50 values near or lower than the potency of the ancestral strain, Wuhan, against which it was designed, CDY14HL neutralized all SARS-CoV-2 strain pseudotypes examined. The CDY14HL decoy has a large tolerance for CoV-2 strain development, showing almost no efficacy within the face of considerable viral spike remodeling under the evolutionary constraints of a multi-year worldwide pandemic, in accordance with binding data and this variant neutralization data.

In decoy binding, several patterns were observed. Within the yeast display test, sarboviruses from clades 1a and 1b certain CDY14HL with sub-nanomolar affinities. RaTG13 has poorer binding to human ACE2 as in comparison with that to other members of the lineage, in accordance with current research. This behavior shows a detailed connection between the natural human ACE2 receptor and the decoy’s affinity. Our suspicion that these clade 2 and three RBDs were unable to bind human ACE2 was validated within the yeast display system employing a soluble wild-type human ACE2-Fc1 fusion protein at a concentration of 100 nM.

Conclusion

The study findings demonstrated that every one the SARS-CoV-2 variants examined, including Delta, Delta Plus, Omicron BA.1, and Omicron BA.2, retained broad neutralizing ability against the affinity-matured decoy. These findings emphasize a key distinction between receptor-based decoy molecules and other biologic viral spike inhibitors: unlike monoclonal antibodies, decoy binding of a variation is intimately linked to receptor binding and, consequently, to viral fitness through evolution.