In a new study, researchers found that an antibody in a blood sample from a patient who recovered from Severe Acute Respiratory Syndrome in 2003 could inhibit related coronaviruses, including the cause of COVID-19.
The antibody, called S309, is now on a fast-track development and testing path in the next step toward possible clinical tests.
What makes this antibody different is that its search did not take place in people who had COVID-19, but in someone who had been infected 17 years ago during a SARS epidemic.
If the antibody is shown to work against the novel coronavirus in people, it could become part of the pandemic armamentarium.
The research was conducted by a team at the University of Washington.
In the study, the scientists identified several monoclonal antibodies of interest from memory B cells of the SARS survivor. Memory B cells form following an infectious illness.
Their lineage can last, sometimes for life. They usually remember a pathogen, or one similar to it, that the body has ousted in the past, and launch an antibody defense against a re-infection.
Several of the antibodies from the SARS survivor’s memory B cells are directed at a protein structure on coronaviruses.
This structure is critical to the coronaviruses’ ability to recognize a receptor on a cell, fuse to it, and inject their genetic material into the cell. This infectivity machinery is located in the spikes that crown the coronavirus.
The S309 antibody is particularly potent at targeting and disabling the spike protein that promotes the coronavirus entry into cells.
It was able to neutralize SARS CoV-2 by engaging with a section of the spike protein near the attachment site to the host cell.
Through their cryo-electronmicroscopy studies and binding assays, the researchers learned that the S309 antibody recognizes a binding site on the coronavirus that is conserved across many sarbocoviruses, not just the SARS and COVID-19 viruses.
That is probably why this antibody, instead of being single-minded, is able to act against related coronaviruses.
Combining the S309 antibody with other, though weaker, antibodies identified in the recovered SARS patient enhanced the neutralization of the COVID-19 coronavirus.
The team says this multiple antibody cocktail approach might help limit the coronavirus’s ability to form mutants capable of escaping a single-ingredient antibody treatment.
The lead author of the study is David Veesler, assistant professor of biochemistry at the University of Washington School of Medicine.
The study is published in Nature.
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