Antibody neutralizes SARS and COVID-19 coronaviruses
An antibody first identified in a blood sample from a patient who recovered from severe acute respiratory syndrome in 2003 inhibits related coronaviruses, including the one that causes COVID-19. This antibody, called S309, is now being developed and fast-tracked for testing at Vir Biotechnology as the next step towards potential clinical trials.The S309 antibody
"We still need to show that this antibody is protective in living systems, which has not yet been done," said principal investigator Dr. Veesler. "At this time, there are no approved tools or approved therapies to control the coronavirus that causes COVID-19," he added. If this antibody proves effective against the new coronavirus in humans, it could become part of the arsenal to fight this pandemic.
Dr. Veesler said his laboratory is not alone in its search for antibodies that neutralize COVID-19. What makes this antibody different is that his research was not done on people with COVID-19, but on someone who was infected 17 years ago during a SARS outbreak. "That's what allowed us to move so quickly compared to other groups," Veesler said.
Scientists identified several monoclonal antibodies from the SARS survivor's B-cells. B cells are formed as a result of an infectious disease. Their lineage can last, sometimes a lifetime. They usually remember a pathogen, or similar agent, that the organism eradicated in the past, and launch an antibody defence against reinfection.
Many of the B-cell antibodies of SARS survivors are directed against a coronavirus protein structure. This structure is essential to the ability of coronaviruses to recognize a receptor on a cell, fuse to it and inject their genetic material into it. This mechanism of infectivity is located in the spikes of the coronavirus.
It can target and deactivate the protein in the spike.
The S309 antibody is particularly powerful in targeting and deactivating the spike protein that promotes coronavirus entry into cells. It was able to neutralize SARS CoV-2 by attacking a section of the spade protein near the site of attachment to the host cell.
Through their cryo electron microscopy studies and binding tests, the researchers learned that the S309 antibody recognizes a coronavirus binding site that is conserved by many sarbecoviruses, not just SARS and COVID-19. This is probably why this antibody is able to act against related coronaviruses.
The combination of the S309 antibody with other, albeit weaker, antibodies identified in the SARS patient resulted in better neutralization of the COVID-19 coronavirus. This multiple antibody cocktail approach could help limit the ability of the coronavirus to form mutants that could escape treatment with single-ingredient antibodies, according to the researchers.
Using this antibody
Scientists have indicated that they hope these initial results will pave the way for the use of S309 antibody, alone or in combination, as a preventive measure for people at high risk of exposure to the COVID-19 coronavirus or as post-exposure therapy to treat severe cases.
