In a new study from the University of Washington, researchers have discovered an antibody that may lead to more effective treatments against a wide range of sarbecoviruses, the family of viruses that includes the coronavirus SARS-CoV-2 and their variants.
The antibody neutralizes SARS-CoV-2, SARS-CoV-2 variants and other sarbecoviruses in the lab, protects against infection in animal studies, and appears to be able to thwart the virus’ attempts to evade it through mutation.
The antibody, designated S2K146, was isolated from the antibody-producing B-cells of a patient who had COVID-19 and recovered.
Like other antibodies induced by SARS-CoV-2 vaccines and used in monoclonal antibody treatments, S2K146 targets the viral spike protein.
One way that antibodies to SARS-CoV-2 prevent infection is by binding to the spike protein receptor-binding domain so it cannot latch onto ACE2.
Over time, however, variants, like omicron, acquire mutations that change the amino acid sequences of the spike protein’s receptor-binding domain so that it is no longer recognized by many antibodies against it. This is called immune evasion.
For the virus, there’s a potential drawback with this strategy: the changes in the receptor-binding domain that allow it to escape the antibody may also impair the ability of the spike protein to bind to its target on the cell, ACE2, and initiate infection.
The SARS-CoV-2 spike protein, however, has proved to be highly adaptable and variants have emerged with mutations that allow the receptor-binding domain to escape existing antibodies against it.
Many researchers did not think antibodies targeting it would be broadly neutralizing viruses as different as SARS-CoV-2 and SARS-CoV.
S2K146 appears to be different. The area uses to bind to and block the spike protein receptor-binding domain is almost identical to the region recognizing the ACE2 receptor.
As a result, any change in the viral spike that reduces the ability of the antibody to bind to it also appears to reduce the ability of the virus to bind to ACE2 and infect cells.
In one experiment, the team exposed a surrogate virus that carries the SARS-CoV-2 spike protein to S2K146 to see if escape mutants would emerge.
They did this ten times, and only one escape mutant emerged. But its ability to bind to ACE2 was so poor it could not outcompete the original virus.
The finding suggests it will be very difficult, though not impossible, for variants to emerge that can both evade S2K146 and remain fit.
The study shows the antibody is a very good candidate for clinical development as monoclonal antibody treatment.
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The study is published in Science. One author of the study is David Veesler.
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