We May Need a New Defense Against New COVID Variants

Roberta Villa

June 01, 2023

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

At the end of 2022, the European Medicines Agency's Emergency Task Force warned European regulatory bodies, governments, and doctors that monoclonal antibodies authorized for COVID-19 are unlikely to be effective against emerging strains of SARS-CoV-2. Antiviral drugs remain available but have many limitations. And, of course, there are still vaccines, which can significantly reduce (but not remove) the risk of severe cases and decrease the number of deaths, although they have lost the efficacy that they once had in countering the original virus.

Research therefore continues. Immunologists continue to search for new targets to synthesize broadly neutralizing monoclonal antibodies for treating or preventing the infection. These results could also lead to new vaccines that induce longer-lasting immunity not only against the thousands of subvariants and recombinant versions of SARS-CoV-2 being identified around the world, but also possibly against other coronaviruses that could emerge in the coming years. A study conducted at Stanford and published in the journal Science Translational Medicine has afforded a glimmer of hope by discovering the broadly neutralizing efficacy of some antibodies produced by macaque monkeys in response to vaccination with AS03 (squalene)‑adjuvanted monovalent subunit vaccines.

The speed with which the virus continues to evolve has rendered the plan for annual vaccine updates, which initially was envisioned early in the pandemic, unfeasible for the time being. In 2020, scientists were considering updating vaccines annually based on the prevalent variants of the disease, similar to the approach to the flu. Perhaps that day will come, but in the meantime, laboratories are pursuing other routes: finding spike epitopes that are preserved more than others each time the virus evolves or focusing on other virus proteins that still manage to induce a neutralizing antibody response.

Eventually, artificial intelligence might be able to custom design monoclonal antibodies that are even more effective than natural ones. Or researchers could completely change tack and shift their attention to the host, rather than the virus itself.

This is the approach taken by one study published in Nature Microbiology, which starts from a simple assumption: SARS-CoV-2 continues to modify its spike protein because of the evolutionary pressure of the antibodies produced by millions of infected people, but all these variants and subvariants, both present and future, enter cells by binding — not solely, but mostly — to the ACE2 receptor. Instead of neutralizing the virus, why not try to block its access to the cells occupying its route in? In this way, we could also be ready for future emerging sarbecoviruses that will have a spike sequence that cannot yet be predicted.

Researchers at The Rockefeller University in New York City have generated six human monoclonal antibodies that bind to the ACE2 receptor, rather than to the spike, preventing infection by all sarbecoviruses tested, even at low concentrations, including the virus that originated in Wuhan, China; the aggressive Delta variant; and various forms of Omicron.

The monoclonal antibodies bind to the ACE2 receptor at a part of the protein that is distal to the active enzyme portion that converts angiotensin and does not modify its expression on the cell surface. Therefore, no adverse effects are expected at this level. In animal models, these monoclonal antibodies succeed in stopping the infection. Moving into the clinical phase will be needed to find out if it will be possible to create products adapted to preventing and treating all SARS-CoV-2 variants, and perhaps also the next coronavirus large enough to spill over into a new epidemic that threatens the human race.

This article was translated from Univadis Italy, which is part of the Medscape Professional Network.

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