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Do previous colds protect against Covid-19?

August 06, 2020 – 4:10 p.m.

T helper cells respond to coronavirus

Studies show that many people who have never had Covid-19 have immune cells that respond to the coronavirus. This is probably related to previous colds. Charité researchers now want to find out what effects this has when infected with Sars-CoV-2.

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Why do patients develop Corona to different degrees?

Scientists from Berlin are investigating why some Covid 19 patients survive the disease much better than others. The researchers at Charité and the Max Planck Institute for Molecular Genetics (MPIMG) found a possible answer for the T helper cells.

They found that in some patients these immune cells respond to the coronavirus even though they have never been in contact with it. This is the case with a third of the group in question, they write in a study published by “Nature”. The T or “killer” cells “memorize” the virus during a Covid 19 disease and initiate an immune response after recovery as soon as they recognize it. The question now is why the T cells of some non-sick people can do that too.

The experts suspect that this has to do with earlier, harmless colds. Other studies come to similar results, for example, a recently published research project led by the La Jolla Institute for Immunology in California or a study by the University Hospital Tübingen. Now the Charité researchers want to find out how such “cross-reactivity” affects a possible infection with Sars-CoV-2.

One third have cross-reactive immune cells

For their investigation, the Berlin scientists obtained immune cells from the blood of 18 Covid-19 patients and from 68 people who had been shown to have never come into contact with the new corona virus. They then compared the cells’ responses to artificially produced Sars-CoV-2 spike proteins with which the virus docks onto human cells. The result: The T helper cells reacted not only to the Covid 19 patients, but also to 24 healthy test candidates. After all, that’s 35 percent.

But it wasn’t exactly the same reaction. The researchers noticed that the T cells of the Covid 19 patients recognized the spike protein over its entire length, while the healthy immune cells were activated primarily by sections of the spike protein, the corresponding sections of the spike protein by resemble more harmless common cold corona viruses.

“This indicates that the healthy T-helper cells react to Sars-CoV-2 because in the past they had to deal with local cold coronaviruses,” says study director Claudia Giesecke-Thiel. “Because one of the properties of the T helper cells is that they can be activated not only by a precisely fitting pathogen, but also by sufficiently similar intruders.” In fact, the T cells of the healthy volunteers also reacted to various corona cold viruses and were therefore cross-reactive.

Negative effects are also possible

That T helper cells from healthy people respond to Sars-CoV-2 could be positive news, but it could be the opposite. “In principle, it is conceivable that cross-reactive T helper cells have a protective effect, for example by helping the body to produce antibodies to the novel virus more quickly,” explains Leif Erik Sander, also the lead author of the study. “In this case, recent coronavirus colds would likely alleviate the symptoms of Covid-19. However, it is also possible that cross-reactive immunity could lead to a misdirected immune response – with negative effects on the course of Covid-19. Know such a situation we, for example, at Dengue-Virus.”

In order to find out what the effects of cross-reactive immune cells are, the Charité has started a new study together with the MPIMG and the Technical University of Berlin. The scientists pay particular attention to groups of people who have had colds in the past. In parallel, the research team will monitor Covid-19 risk groups.

Subjects wanted

Specifically, it is planned to examine employees of kindergartens and pediatric practices as well as residents of nursing homes in the coming months. In addition to a PCR test for Sars-CoV-2, your blood should also be tested for antibodies against the virus and the reactivity of the T cells. If Sars CoV-2 infection occurs in some of the investigated, the researchers can relate the course of the disease to the immunological parameters.

In order to determine other possible factors that influence the severity of a Covid 19 disease, the Berlin scientists also want to examine the blood of at least 1,000 recovered patients. For this they are looking for subjects. They are also interested in examining people who have been shown to be infected with a common cold coronavirus in recent years. You can write an email to studie (at) si-m.org.

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