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Current Affairs

SARS antibody neutralises COVID-19

Date: 22 May 2020 Tags: Miscellaneous

Issue

One antibody, called S309, taken from a SARS survivor from 2003, has been shown in the lab to neutralise SARS-CoV-2.

 

Background

In the continuing hunt for antibodies that could fight the novel coronavirus SARS-CoV-2, researchers have mostly looked at people who have already contracted Covid-19. 

 

Details

  • The other antibody, called CR3022, was first isolated from a SARS survivor of the early 2000s. CR3022 may hold clues to the vulnerability of SARS-CoV-2.

  • Scientists isolated antibodies from a SARS survivor’s “memory B cells” Memory B cells form after an infectious illness, and usually remember the pathogen (or a similar one) that it had fought it back earlier. If a new infection happens, these cells launch an antibody counterattack again.

  • From the SARS survivor’s memory B cells, the scientists identified a number of monoclonal antibodies. Several of these antibodies target a protein structure on coronaviruses (SARS and Covid-19 are caused by different but related coronaviruses).

  • This protein structure is located in the spikes in the crown, the “corona” of the virus. The spike is a crucial tool in infection; this is what attaches to human cells.

  • Among the antibodies, S309 was found to be particularly potent at targeting and disabling the spike protein. It was able to neutralise SARS CoV-2 by engaging with a section of the spike protein near the site where it attaches to the host cell.

  • The scientists noted that they hope these initial results will pave the way for using S309, alone or in a mixture, as a preventive measure for people at high-risk of exposure to SARS-CoV-2 or as post-exposure therapy.

  • The antibody’s binding site was found highly similar between the two coronaviruses. However, the antibody binds much less tightly to SARS-CoV-2 than it does to the SARS virus.

  • The takeaway is that the binding site, as identified, is a site of vulnerability for SARS-CoV-2. Other antibodies binding it more tightly would plausibly succeed in neutralising the virus.