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Of: Elle kari karlsson
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A new German study shows that more than 80 percent of the population may have a T-cell response to COVID-19, called cross-immunity. The discovery is important for future research, but does not imply any herd immunity according to experts.
More than 80 percent of the population may have a T-cell response to COVID-19, that is, the so-called cross-immunity. It shows a new German study, published in the scientific journal Nature Immunology.
By analyzing blood from donors who have recovered from COVID-19, researchers have managed to identify the so-called T-cell epitopes that are behind the T-cell response to COVID-19. This made it possible to detect T-cell responses in 100 percent of the 180 study volunteers. This was also true for the volunteers who did not show any antibodies during the test.
The study also looked at donor blood samples collected before the pandemic broke out. Surprisingly, small amounts of Covid-19 targeted T cells, thus recognizing viral components, in 81 percent of these unexposed donors.
T cells generally work to recognize a virus-infected cell and kill it. In this way, you can generate early control of the virus. However, cross-immunity does not necessarily mean that one is immune to COVID-19, and the effects of existing T cells should be investigated in further studies.
– It is not true that 80 percent are completely immune and cannot get sick, this is not how cells work. Its role is to slow the course of the disease, says Marcus Buggert, associate professor at the Karolinska Institutet Center for Infectious Diseases.
Marcus Buggert, an assistant professor at the Karolinska Institutet Center for Infectious Diseases.
The new study shows to some extent the same as a Swedish study that was published this summer. Then, researchers from the Karolinska Institute and Karolinska University Hospital found that immunity to COVID-19 may be higher than antibody tests show. Many in the study showed so-called T-cell immunity to the coronavirus, and the researchers found that the T-cell response was on par with what can be measured after vaccination with approved vaccines against other viruses. Those that were milder weren’t always able to show antibodies on a test, but they still showed a significant T-cell response, according to the study.
According to Marcus Buggert, this likely means that there have been other coronaviruses circulating, to which virtually everyone has been exposed. The old coronaviruses are probably similar enough to the new ones that the old T cells recognize the new virus. T cells may not provide the same sterile protection as antibodies, but they can recognize infected cells.
– It can generate an early control of the virus. It is probably the case that people who have a T-cell response like this have a milder variant of the virus. However, I do not think that cross immunity gives rise to herd immunity. For a cell to be activated, a certain degree of infection is required, and if so many people have these responses, we would already have a herd immunity in society now, says Marcus Buggert.
According to research leader Juliane Walz, the discovery of epitopes is not only important for research and diagnosis of immunity to COVID-19, but can also form the basis for vaccine development.
Photo: Johan Nilsson / TT / TT NEWS AGENCY
Blood samples are tested for antibodies.
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