An antibody isolated from a patient who has recovered from SARS (severe acute respiratory syndrome) is shown to effectively block SARS-CoV-2 infectivity. This finding is reported in Nature today. Antibodies that can neutralize the virus could help in the development of anti-viral treatments or vaccines.
Antibodies are produced by the immune system in response to foreign material invading the body. Monoclonal antibodies can target one specific protein (antigen) on a pathogen. Identifying monoclonal antibodies that can bind to the spike protein found on SARS-CoV-2 and SARS-related coronaviruses, which facilitates entry into human cells, may aid efforts to treat or prevent SARS-CoV-2 infection.
Davide Corti and colleagues previously identified monoclonal antibodies, from a patient who recovered from SARS in 2003, that could inhibit SARS-related coronaviruses from both humans and animals. They investigated the potential for 25 of these antibodies to inhibit SARS-CoV-2 (an effect called cross-reactivity) and found eight antibodies that could bind to both the free virus and infected cells. One candidate, named S309, is shown to have particularly strong neutralizing activity against SARS-CoV-2. By solving the crystal structure of S309, the authors demonstrate how the antibody binds to the viral spike protein. They show that S309 can act in combination with another, less potent, antibody that targets a different site on the spike protein of the virus. This synergistic activity could enhance neutralization while reducing the chance of resistant mutations emerging, the authors suggest.
The proof-of-concept findings suggest that cocktails of monoclonal antibodies may be worth exploring to control SARS-CoV-2. However, no experiments were performed in humans in this study.
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