Common cold in past may give protection from Covid-19

New York, Sep 30 (IANS) In a big breakthrough, researchers have found that people who have had a bout of seasonal or common cold in the past may get protection from Covid-19.The study, published in the journal mBio, also suggests that immunity to Covid-19 is likely to last a long time -- maybe even a lifetime.The study showed 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.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 bear that out, the researchers said.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. Study authors 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 lead study author Mark Sangster from the University of Rochester in the US.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, 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 of the viruses. Memory B cells can't tell the difference between the Spike S2 subunits of the different coronaviruses, and attack indiscriminately. The study found that was true for beta coronaviruses, a subclass that includes two cold-causing viruses as well as SARS, MERS and SARS-CoV-2. "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," the authors wrote.
--IANS bu/dpb/in