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Some people already have antibodies that recognize Covid-19, thanks to the common cold



A health care worker in Washington DC is holding a blood sample collected to check for antibodies to SARS-CoV-2.

A health care worker in Washington DC is holding a blood sample collected to check for antibodies to SARS-CoV-2.
Photo: Won McNamee (beautiful images)

A new study shows that a small portion of the population carries antibodies that react to the coronavirus behind covid-19 without becoming infected.— Antibodies from previous episodes with a common cold caused by a related virus.

The latest research indicates that some people may have a preexisting level of immunity to coronavirus. But while it is possible that these findings could help explain some pandemic trends, such as children being less vulnerable to serious illness, it is not yet clear about this borrowed immunity. really like.

New research, published in the Science journal on Friday, tested blood samples collected from adults and children in the UK before the start of the pandemic in December 2019, as well as from those early in the pandemic ending. The test results were negative for SARS-CoV-2, the coronavirus responsible for covid-19. These samples were compared with covid-19 confirmed individuals.

As expected, most confirmed cases have a diverse group of antibodies in response to the virus’s mutant protein, used by viruses to infect cells. They come from all three types of antibodies that fight viral infections (IgG, IgM, IgA). But in some uninfected patients, including those confirmed to be recently infected with the common cold coronavirus, researchers also found antibodies that appear to react to SARS-CoV-2. “Our results from multiple independent trials have demonstrated the presence of existing antibodies that recognize SARS-CoV-2 in uninfected individuals,” the researchers wrote.

The antibodies found in uninfected individuals differ markedly from those in covid-19 patients. They are mostly IgGs, the most common type of antibody produced by the immune system. They are also found only in a small percentage of adults. In samples from 302 adults, only 16 (5.26%) carried these antibodies. However, that’s not true for children: Researchers found these antibodies in 21 out of 48 samples (44%) collected from children between the ages of 1 and 16.

The authors speculate that higher levels of cross-reactive antibodies seen in children may help explain why they appear to be less susceptible to covid-19 than the general population, or why they are common. get sick much less. Children always have mild colds, and they found evidence that more frequent human coronavirus infections may explain higher antibody levels in children.

This study appears to be the first to find these cross-reactive antibodies in humans. However, other research has show that some people also carry T cells – another important part of the immune system – borrowed from earlier common cold infections that may react to SARS-CoV-2. Together, these studies indicate that some people may indeed have a pre-existing immune response to covid-19. But there is reason to be cautious in interpreting the results.

“We still don’t know anything about protection, although some groups show cross-reactivity. Epidemiology shows that cross-reactivity is unlikely to prevent infection or spread – it can at best alter symptoms, ”said lead author Kevin Ng, graduate student and virologist at the Francis Crick Institute in London, said.

There are those who have argued that T-cell studies show that many people around the world have been protected from the pandemic, often to justify their stance against aggressive actions aimed at curbing infection. spread of viral diseases. However, the scientists behind the study have made a claim speak out about these statements. They note that there is still much uncertainty about how these cross-reactive T cells may influence a person’s response to infection and it is unlikely that having these cells will significantly inhibit a person’s response to infection. a person who has or spread covid-19 to another person. In other words, these T cells do not receive we are called faster herd immunity.

Another reason for caution: It does Feasibility that having cross-reactive antibodies may actually increase the risk of more serious illness in some cases, which is known to have happened with the original SARS virus.

In any case, more research will have to be done to be sure of anything. Besides helping to explain why certain groups of people may be less vulnerable to covid-19 in some way, the researchers speculate that understanding the basics of the immune system borrows. This borrowing could one day lead to better vaccines against both current and future coronavirus.

“We are currently working to figure out why some people create cross-reactive antibodies and some don’t,” Ng said. “If we can find that out, we could use that information in vaccines to theoretically stimulate an immune response that targets all coronaviruses.”


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