Because memory B cells can survive for decades, they could protect COVID-19 survivors from subsequent infections for a long time, but further research will have to confirm this.
The study is also the first to report cross-reactivity of memory B cells -- meaning B cells that once attacked cold-causing coronaviruses appeared to also recognise SARS-CoV-2.
The researchers believe this could mean that anyone who has been infected by a common coronavirus -- which is nearly everyone -- may have some degree of pre-existing immunity to COVID-19.
"When we looked at blood samples from people who were recovering from COVID-19, it looked like many of them had a pre-existing pool of memory B cells that could recognise SARS-CoV-2 and rapidly produce antibodies that could attack it, said study lead author Mark Sangster, a research professor at URMC.
The findings are based on a comparison of blood samples from 26 people who were recovering from mild to moderate COVID-19 and 21 healthy donors whose samples were collected six to 10 years ago -- long before they could have been exposed to COVID-19.
From those samples, the researchers measured levels of memory B cells and antibodies that target specific parts of the Spike protein, which exists in all coronaviruses and is crucial for helping the viruses infect cells.
The Spike protein looks and acts a little different in each coronavirus, but one of its components, the S2 subunit, stays pretty much the same across all of the viruses.
Memory B cells can't tell the difference between the Spike S2 subunits of the different coronaviruses and attack indiscriminately, the researchers said.
They found that was true for beta-coronaviruses, a subclass that includes two cold-causing viruses as well as SARS, MERS and SARS-CoV-2.
What this study doesn't show is the level of protection provided by cross-reactive memory B cells and how it impacts patient outcomes, according to the researchers said.
(Only the headline and picture of this report may have been reworked by the Business Standard staff; the rest of the content is auto-generated from a syndicated feed.)
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