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Common cold viruses can cause a response to the coronavirus, San Diego researchers report

Your chances of getting COVID-19 may depend in part on how your body reacted the last time you caught a cold, according to a study published this week by researchers at the La Jolla Institute for Immunology.

SARS-CoV-2, the virus that causes COVID-19, may be the latest coronavirus, but it is not the first. There are four other coronaviruses that can cause colds. The new study shows that some people who have never been infected with SARS-CoV-2 have an immune response to it because they have been exposed to what are essentially older cousins ​​of the new coronavirus.

Researchers still know exactly what all this means. But it is possible that people with immune responses to the common coronavirus may be less likely to get COVID-1

9, says Alessandro Sette, one of the study’s older authors.

“This can give you an edge,” Sette said. “If you have a head start, you can get a faster response or a stronger response. You may not get as sick. “

Sette and colleagues published their results on Tuesday in the journal Science, but their discovery began with a puzzling observation months ago. That was when Sette’s team discovered immune responses to the new coronavirus in blood samples collected before the COVID-19 pandemic – which meant that there was no way these samples came from people who had been exposed to the virus.

This finding has since been confirmed by studies from people from the United States, the United Kingdom, the Netherlands, Germany and Singapore. These reports showed that between one-fifth and one-half of those who have never been exposed to the new coronavirus may have an immune response to it.

But why? Sette’s team suspected that the four common coronaviruses were the answer. Perhaps some people’s immune systems had already seen parts of the common coronavirus that were almost identical to the new virus.

To test this theory, researchers tested blood collected from San Diego before the pandemic. They found all areas of the coronavirus targeting their immune system and looked for regions in the four common coronaviruses that were almost identical.

When researchers used these matching viral regions to stimulate the cells of uninfected humans, their immune cells revamped, suggesting that some of these cells could respond to both the previous coronavirus and the new virus.

The results, based on studying cells in a dish, do not prove that exposure to previous coronavirus protects against COVID-19. But in that case, it would help explain why COVID-19 is fatal to some while others recover with hardly any symptoms (age and previous conditions are clearly still important factors).

This kind of thing has happened before, says Daniela Weiskopf, a researcher at La Jolla Institute for Immunology and students with parenting. She cites the 2009 swine flu pandemic, in which adults 65 and older were less likely to get sick; Some researchers believe that older adults benefited from an pre-existing immune response to a similar influenza virus from decades earlier.

“It’s provocative and interesting,” said Dennis Burton, an immunologist at Scripps Research who is not involved in the study. “There is still a step missing because you have to show that this is important for immunity.”

Sette and Weiskopf believe that data from ongoing COVID-19 vaccine trials can help address the missing piece by measuring T cells, immune cells that activate the parts of an antiviral response that kills infected cells and that produce antibodies, proteins that can grab the surface of a virus and prevent infection.

Both researchers say that studies of T-cell responses before and after a COVID-19 vaccine can help researchers interpret all the variations between people in how well a vaccine works. It is possible, says Weiskopf, that those who respond best to a vaccine will do so because they already have T cells to bypass the coronavirus that are ready to launch a rapid counterattack.

“It’s something we’re very interested in and we’re looking at.”

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