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Scientists have discovered that some antibodies, created by the immune system during infection with the common cold coronavirus, can also attack the Covid-19 that causes SARS-CoV-2 and can confer some degree of protection against the new virus.
The researchers, including those at the Francis Crick Institute in the UK, explained that, in response to a viral infection, the immune system creates antibodies to help fight it, which remain in the blood for a period of time and prevent reinfection.
In the new study, published in the journal Science, scientists found that some people, especially children, have reactive antibodies to the novel SARS-CoV-2 coronavirus in their blood, despite never having been infected with the virus.
They said these antibodies are likely the result of exposure to other coronaviruses, which cause a common cold and have structural similarities to SARS-CoV-2.
Using highly sensitive antibody tests for Covid-19 that the researchers developed, they compared the blood of patients with the new coronavirus infection with patients who had not had the disease. The scientists found that some people who had not been exposed to SARS-CoV-2 had antibodies in their blood that would recognize the virus. To confirm their findings, they analyzed more than 300 blood samples collected before the pandemic, between 2011 and 2018.
Almost all of the samples had antibodies that reacted with the common cold coronaviruses, which was expected given that all have been exposed to these viruses at some point in their lives, the study noted. However, a small fraction of adult donors – about one in 20 – also had antibodies that cross-reacted with SARS-CoV-2, and this was not dependent on a recent infection with a common cold coronavirus, he said.
According to the researchers, these cross-reactive antibodies were found much more frequently in blood samples taken from children aged six to 16 years.
“Our results show that children are much more likely to have these cross-reactive antibodies than adults,” said Kevin Ng, lead author of the study from the Francis Crick Institute in the UK. “More research is needed to understand why this is so, but it could be because children are more frequently exposed to other coronaviruses,” he added.
Scientists believe that these higher levels seen in children may also explain why they are less likely to become seriously ill with Covid-19. In the lab, scientists tested the antibodies they found in the blood of uninfected people to confirm that they can neutralize SARS-CoV-2. They found that cross-reactive antibodies target the S2 subunit of the spike protein on the surface of the virus, which it uses to enter host cells.
“The S1 subunit allows the virus to adhere to cells and is relatively diverse among coronaviruses, while the S2 subunit allows the virus to enter cells and is more similar among these viruses,” explained George Kassiotis, lead author of the Francis Crick Institute study. .
“Our work shows that the S2 subunit is similar enough between the common cold coronaviruses and SARS-CoV-2 that some antibodies act against both,” Kassiotis said.
While previous studies hinted that only antibodies to S1 could block infection, the researchers said there is “good evidence now” that some antibodies to S2 “may be just as effective.” “This is exciting, as understanding the basis for this activity could lead to vaccines that work against a variety of coronaviruses, including strains of the common cold, as well as SARS-CoV-2 and any future pandemic strains,” Kassiotis said.
However, the scientists said that several study questions remain unanswered and require further investigation. “For example, exactly how is immunity to one coronavirus modified by exposure to another? Or why does this activity decrease with age? It is not the case that people who have recently had a cold should think they are immune to Covid-19, “Kassiotis added.
(This story was posted from a cable agency feed with no text changes. Only the title was changed.)
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