Researchers at the Francis Crick Institute and University College London have found that some antibodies, produced by the immune system during infection with the common cold coronavirus, can also target. SARS-CoV-2 and may provide a level of protection against new strains.
In response to a viral infection, the immune system produces antibodies to help fight the virus. These antibodies remain in the bloodstream for a while after infection, and in the event of a re-infection, they may destroy the virus again.
In their article, published in Science Today (Friday, November 6, 2020), scientists discovered that some people, especially children, have antibodies that react to SARS-CoV-2 in their blood, though have never been infected with a virus. These antibodies may result from exposure to other coronaviruses, which cause the common cold, and are structurally similar to SARS-CoV-2.
Researchers made this discovery while developing highly sensitive antibody assays for COVID-19. To see how well their laboratory tests were working, they compared the blood of patients with COVID-19 with those without the disease. Surprisingly, they found that some people not exposed to SARS-CoV-2 had antibodies in their blood that could recognize the virus. To confirm their findings, they analyzed more than 300 blood samples collected before the pandemic, between 2011 and 2018.
Nearly all of the samples showed antibodies that react to the common cold coronavirus, which is thought to be caused by people who have been exposed to these viruses at some point in their life. However, a small fraction of adult donors, approximately 1/20, also have cross-reactive antibodies to SARS-CoV-2 and this is independent of recent infection with a common cold coronavirus.*
Notably, such cross-reactive antibodies were found much more frequently in blood samples taken from children 6 to 16 years old.
“Our results show that children are more likely to have these cross-reactive antibodies than humans,” said Kevin Ng, lead author and graduate student at the Retrovirus Immunology Laboratory at Crick. big. More research is needed to understand why this is the case, but it may be because children are frequently exposed to other coronaviruses.
“The higher levels we observed in children may also help explain why they are less likely to get seriously ill with COVID-19. However, there is no evidence that these antibodies prevent the infection or spread of SARS-CoV-2 ”.
In the lab, researchers tested the antibodies they found in the blood of uninfected people to confirm that they could inactivate SARS-CoV-2. They found that cross-reactive antibodies targeting the S2 subunit of the protein spike on the surface of the virus.
“This coronavirus surge is made up of two parts or subunits, doing different jobs,” said George Kassiotis, senior author and team leader at the Retrovirus Laboratory of Immunology at Crick . The S1 subunit allows the virus to attach to cells and is relatively diverse among coronaviruses, while the S2 subunit allows the virus to enter cells and are more similar between these viruses. Our research shows that the S2 subunit is similar enough between the common cold coronavirus and SARS-CoV-2 for some of the antibodies to act against both.
“It was previously thought that only antibodies to S1 could stop infection, but now there is good evidence that some antibodies to S2 may be as effective. This is interesting because understanding the rationale for this activity could lead to vaccines that work against a wide range of coronaviruses, including common cold strains, as well as SARS-CoV-2 and any future pandemic strains.
“But it is important to emphasize that there are still many unknowns that need further study. For example, exactly how is immunity to one coronavirus modified by exposure to another virus? Or why does this activity decline with age? Not the case that people who have recently caught a cold should think that they are immune to COVID-19 ”.
A large study is currently underway in collaboration with researchers now Royal University London and University College London, to explore the role of various antibodies and other immune defense measures in protecting against COVID-19 and the severity of illness.
* Researchers found that:
- Of the samples taken from 50 pregnant women in May 2018, 10% had cross-reactive antibodies.
- 21 out of 48 blood samples taken from children 1 to 16 years of age between 2011 and 2018 contained these cross-reactive antibodies.
- One more cohort of 13 adult donors was recently infected with other coronaviruses, with only one tested positive for these cross-reactive antibodies.
Reference: “Pre-existing humoral immunity and immunity to human SARS-CoV-2” by Ng, K et al., November 6, 2020, Science.
DOI: 10.1126 / science.abe1107