Is This Why Some People Have Milder Coronavirus Symptoms?

Man with coronavirus immunity
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One of the strangest things about COVID-19 is how it impacts people in such different ways. Some patients become gravely ill — and even die — while a majority of those infected experience minor symptoms, or none at all.

Now, a study investigating why the coronavirus disease has a mild impact on so many people might make you grateful for an illness most of us love to hate: the common cold.

Researchers at La Jolla Institute for Immunology say memory helper T cells — which recognize common-cold coronaviruses — also recognize matching sites on SARS-CoV-2, the official name of the particular coronavirus that causes COVID-19, according to a new La Jolla Institute study.

“Memory” T cells essentially remember the viruses they have seen previously, which helps the body’s cells recognize and fight repeat invaders. And this function may help prevent people from getting as sick with COVID-19, says Daniela Weiskopf, a La Jolla Institute research assistant professor who co-led the new study:

“We have now proven that, in some people, pre-existing T cell memory against common cold coronaviruses can cross-recognize SARS-CoV-2, down to exact molecular structures. This could help explain why some people show milder symptoms of disease while others get severely sick.”

Weiskopf says having a more robust T cell response might help your body mount a quicker, stronger response to the coronavirus that is at the root of today’s pandemic.

The new findings seem to support an earlier paper from the institute reporting that 40% to 60% of people who never had been exposed to SARS-CoV-2 nonetheless had T cells that reacted to the virus. In effect, their immune systems recognized fragments of the virus despite never having seen it before.

The upshot of the new research is that fighting off a common cold coronavirus might teach your body’s T cell compartment to recognize some parts of SARS-CoV-2. Still, the researchers caution that their findings amount to “speculation” and say much more data is needed before reaching any definite conclusions.

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