Common cold could protect from COVID-19

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New research suggests past common colds may provide some protection from the novel coronavirus (COVID-19), according to new research by infectious disease experts at the University of Rochester Medical Center published in the journal mBio.

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 study authors 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 the viruses. Memory B cells can't tell the difference between the Spike S2 subunits of the different coronaviruses, and attack indiscriminately. At least, the study found that was true for betacoronaviruses, a subclass that includes two cold-causing viruses as well as SARS, MERS, and SARS-CoV-2.

The research showed SARS-CoV-2, the virus that causes COVID-19, induces memory B cells, long-lived immune cells that detect pathogens, create antibodies to destroy them and remember them for the future. The next time that pathogen tries to enter the body, those memory B cells can hop into action even faster to clear the infection before it starts. Since memory B cells can survive for decades, they could protect COVID-19 survivors from subsequent infections for a long time, but further research is needed, the authors said.

The study also reported cross-reactivity of memory B cells, meaning B cells that once attacked cold-causing coronaviruses appeared to also recognize SARS-CoV-2. The researchers said they believe this could mean that anyone who has been infected by a common coronavirus may have some degree of pre-existing immunity to COVID-19.

What this study doesn't show is the level of protection provided by cross-reactive memory B cells and how it impacts patient outcomes.

"That's next," said David Topham, PhD, the Marie Curran Wilson and Joseph Chamberlain Wilson Professor of Microbiology and Immunology, who runs the lab that conducted this work, in a statement. "Now we need to see if having this pool of pre-existing memory B cells correlates with milder symptoms and shorter disease course, or if it helps boost the effectiveness of COVID-19 vaccines."

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