How the common cold could potentially protect you against Covid-19

• While Covid-19 is better understood than at the beginning of the year, researchers are still investigating immunity
• There are coronaviruses that cause seasonal colds
• Memory B cells could cross-target both coronaviruses and SARS-CoV-2

Common colds can make us feel lousy, but according to a new study from infectious disease experts at the University of Rochester Medical Centre, the colds we’ve had in the past could potentially play a role in protecting us against Covid-19.

The study was published in mBio and is the first to show that SARS-CoV-2, the virus that causes Covid-19, induces memory B cells – immune cells that last for a long time and detect and destroy pathogens.

These clever cells also remember some pathogens, so that they can destroy them next time, before infection even starts. Memory B cells are said to last for decades and researchers are still investigating whether those who have had Covid-19 will be protected by these cells.

The study reported that memory B cells can cross-react, which means that those cells that attacked your common cold might be clever enough to recognise SARS-CoV-2.

Memory B cells target the same component in spike protein

As some common colds are also caused by coronaviruses, there is the possibility that there could be pre-existing immunity against SARS-CoV-2 in some people. And according to the researchers, this is nearly all of us.

"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, PhD, research professor of Microbiology and Immunology at URMC in a news release.

The team of researchers looked at blood samples from 26 patients who were recovering from mild to moderate Covid-19 and 21 healthy people who donated samples between six and ten years ago. The researchers then measured the levels of memory B cells and antibodies that could target the spike proteins that exist in all the coronaviruses.

While the spike proteins differ in each type of coronavirus, they have a component that is the same in all of them – and that can be recognised by memory B cells. According to the researchers, this was the case in a subclass of coronaviruses called betacoronaviruses, which cause colds, SARS, MERS and SARS-Cov02.

No level of protection known yet

The researchers are still planning to see what level of protection the cross-reactive memory B cells provide and what this means for patient outcomes.

"That's next," stated David Topham, PhD, the Marie Curran Wilson and Joseph Chamberlain Wilson Professor of Microbiology and Immunology at URMC. "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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