People who have had a bout of seasonal or common cold in the past may get some protection from COVID-19, according to a study which suggests that immunity to the disease is likely to last a long time -- maybe even a lifetime. The study, published in the journal mBio, is the first to show that the COVID-19-causing virus, SARS-CoV-2, 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, according to the researchers from the University of Rochester Medical Center (URMC) in the US.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.