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Zurich – Infections with seasonal coronaviruses, which are partly responsible for the frequent colds of small children in the first years of life, could protect against infection with SARS-CoV-2 and severe courses of COVID-19.

The protective effect of cross-reactive antibodies, which has been discussed by researchers for some time, is shown in a study in Nature Communications (2021; DOI: 10.1038 / s41467-021-27040-x) confirmed.

SARS-CoV-2 is not the only coronavirus. At least 4 relatives regularly cause epidemics worldwide. OC43, HKU1, NL63 and 229E do not trigger public health measures as they only cause harmless colds. Children in the first years of life are particularly affected. Immunity later sets in that protects adults from diseases that may be more severe for them.

A team led by Alexandra Trkola from the University of Zurich has now examined the influence of this immunity on the risk of infection from SARS-CoV-2 and the risk of developing COVID-19.

With a specially developed test procedure, the researchers examined the amount of different antibodies against the 4 other seasonal coronaviruses in the blood serum of 825 blood donors from the time before the occurrence of SARS-CoV-2. 389 samples from donors infected with SARS-CoV-2 were later analyzed.

It showed that the patients who were infected with SARS-CoV-2 had lower levels of antibodies against the cold coronavirus in their blood. Conversely, Trkola concludes that a previous infection with OC43, HKU1, NL63 and 229E could temporarily protect people from infection with SARS-CoV-2. The mechanism could be a cross-resistance. Since the antibody titers decrease rapidly after an infection with coronaviruses, children in the first place could benefit from it.

The researchers also found that SARS-CoV-2 infected people with high antibody levels against the harmless coronaviruses had to be hospitalized less often because of COVID-19. According to Trkola, this could mean that cross-immunity also protects against severe courses.

According to Trkola, it is still unclear whether the cross-reactivity also works the other way round. So whether immunity against SARS-CoV-2 – for example through a vaccination – also protects against the seasonal coronaviruses. In this case, children who were vaccinated against SARS-CoV-2 would be less likely to get a cold, at least in the next season. This protection would probably only show itself in smaller children, for whom, however, no vaccinations are currently planned.

The question of cross immunity has also preoccupied other scientists since the beginning of the pandemic. In October last year, US researchers reported in the Journal of Clinical Investigation (2020; DOI: 10.1172 / JCI143380) that previous infections with seasonal coronaviruses weakened the course of COVID-19. They could not prove any protection against infection with SARS-CoV-2.

British researchers found that children after colds have cross-reactive antibodies in their blood that could prevent the virus from entering cells (Science, 2020; DOI: 10.1126/science.abe1107).

Conversely, in children who had survived an infection with SARS-CoV-2, antibodies were detected that also recognize relevant epitopes on the coronaviruses that are responsible for seasonal colds (Cell Reports Medicine, 2021; DOI: 10.1016/j.xcrm.2020.100189).

But there were also negative studies that found no protective effect of the antibodies against seasonal coronaviruses against SARS-CoV-2 (Cell, 2021; DOI: 10.1016 / j.cell.2021.02.010). © rme / aerzteblatt.de

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