Monday , January 18 2021

After hope for cross-immunity: Cold viruses do not protect against cobid-19

Who is infected with cold coronavirus, better protected from Sars-CoV-2 infection? At least that’s what some experts suspect. However, researchers from Kyle are now finding out: Cold viruses do not provide better protection against the immune system. On the contrary: they may even be harmful.

Coronaviruses were already circulating before the Sars-CoV-2 epidemic. For example, they may cause colds. Therefore, experts suspected that previous contact with these cold viruses could lead to better immune protection against Sars-CoV-2 infection. Researchers from Kyle have now refuted this idea in the study: People who have not yet been infected with Sars-CoV-2 will actually have certain immune cells, so-called T-memory cells, which also recognize Sars-CoV-2 as foreign bodies. tin. However, these memory T cells are not particularly effective because they only bind the virus weakly.

In their study, Kiel researchers tested the blood cells of blood donors who had no previous association with Sars-CoV-2. They found that people without previous contact with the virus actually have these memory cells that also identify Sars-CoV-2 as a foreign body. “However, contrary to expectations, younger people with colds have a greater number of these cells,” says Alexander Schpold of Schleswig-Holstein University Medical Center. In addition, only a small proportion of these also respond to corona cold viruses.

“It seems to be more the case that during life the repertoire of memory cells against many different pathogens increases, and so is the probability that there are those who recognize Sars-CoV-2 by chance,” explains Schepold. Therefore this repertoire of memory cells, which grows with each infection, can also be called the “immune age”, which actually increases with the biological age.

However, although these memory cells are present in everyone, they are obviously not involved in protection against Sars-CoV-2 infection. This is probably due to their quality: “Although these T-cells detect Sars-CoV-2 viruses, they do not do it very well. As a result, they are apparently unable to guarantee that the virus fights successfully,” says first author Petra Bachar of Kill University. .

Immunological age as a risk factor

The research team found T cells in the blood of Cubid 19 sufferers with a mild course, which identify the virus well. “It can be based on an immune response based on naive T cells, that is, the T cells that support the immune response against the virus here can be derived from naive T cells and not from memory cells,” Bachar explains.

This was particularly interesting for the researchers because in patients with a severe course of the disease, the T cells recognize Sars-CoV-2 just as poorly as the “existing” memory T cells. “This may indicate that these immune cells in the severe coboid cases originate from poorly existing memory T cells,” says Bacher.

This can provide a simple explanation as to why older people are at higher risk of developing the disease more severely. “In many cases they are also of a higher immunological age and therefore more likely that the immune system will use these ‘incompetent’ memory cells,” says Bachar.

Colleague Fuld says: “Our work shows that previous colds with coronaviruses do not offer effective immune protection against Sars-CoV-2.” In addition, it provides important evidence that immunosuppressive age may favor a severe course of Covid-19 disease. “Further investigations are needed to examine a direct link between immune age and severe Covid-19, and to analyze the effect of existing memory cells on the immune response against Sars-CoV- 2 “, said Fold.

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