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Washington (AFP)
The emergence of coronavirus variants has raised concerns about their impact on vaccine effectiveness and whether people who were previously infected might be more likely to be re-infected.
But in the good news, a new study on Tuesday showed that a key player in the immune response, called a “killer T cell,” remained mostly unchanged.
The finding is encouraging because, while these white blood cells are not a first line defense against infection, they can help prevent serious illness.
Scientists at the National Institutes of Health and Johns Hopkins University analyzed blood samples from 30 people who had contracted and recovered from Covid-19 before variants emerged.
They published their findings in the Open Forum Infectious Diseases, a journal of Oxford University Press.
The team wanted to know if these cells, known by their technical name “CD8 + T cells”, could still recognize three variants of SARS-CoV-2: B.1.1.7, found for the first time in Great Britain, B.1.351, identified in southern Africa, and B.1.1.248, first seen in Brazil.
What makes each of these variants unique are the mutations they carry, especially in a region of the virus spike protein, structures that stud its surface and allow it to invade cells.
Mutations in this region of the spike protein have previously been shown to make some variants less recognizable to neutralizing antibodies – infection-fighting proteins produced by B cells of the immune system.
This appears to be particularly true, for example, of B.1.351, according to research on the impact of current generation Covid vaccines.
Neutralizing antibodies are custom designed to adapt to a specific antigen or structure of a pathogen.
In the case of the coronavirus, this is the spike protein, to which antibodies bind, preventing the virus from infecting cells.
Killer T cells, on the other hand, look for telltale signs of cells that have already been infected with pathogens they have already encountered, and then kill those cells.
In the new study, the researchers found that the responses of the killer T cells remained largely intact and could recognize virtually any mutations in the variants studied.
The researchers noted that larger studies are needed to confirm the results, but said it nonetheless demonstrates that killer T cells are less susceptible to mutations in the coronavirus than neutralizing antibodies.
Antibodies are still important in preventing infection in the first place – and the reduced effectiveness of variant vaccines seems to be proof of this.
But a T-cell killer response that comes in later and helps clear the disease helps explain why vaccines appear to be able to prevent serious illness and hospitalization, even though their effectiveness in stopping infection with variants is. scaled down.
© 2021 AFP
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