A Swiss study examined the immunity that arises after contact with coronaviruses that are already endemic. At least temporarily, this should also protect against Covid-19.

6 a.m., November 25, 2021

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Endemic coronaviruses already cause colds and runny nose. They could also help protect against Sars-CoV-2 © (c) Terovesala – stock.adobe.com

There is apparently a close connection between coronaviruses, which have long been known to cause coughs, runny nose and hoarseness, and SARS-CoV-2. An infection with the harmless seasonal known coronaviruses should at least temporarily protect against Covid-19. A Swiss team of scientists has now found new evidence for cross-reactive antibodies.

SARS-CoV-2 is not the only coronavirus that occurs in humans. Four similar viruses – OC43, HKU1, NL63 and 229E – are classic causative agent of seasonal colds. “Children in the first years of life are particularly affected. Later, an immunity sets in that protects adults from diseases that may be more severe for them,” wrote the German medical journal about the scientific results.

Cross-active antibodies

The corresponding study by Zurich scientist Alexandra Trkola was in a few days ago “Nature Communications” appeared. In it, the influence of immunity against the “old” coronaviruses on the risk of infection from SARS-CoV-2 and the risk of disease from Covid-19 was examined. The team of authors from the University of Zurich used a specially developed test to examine the amount of different antibodies against the long-known, seasonal coronaviruses found in humans in the serum of 825 blood donors from the time before the occurrence of SARS-CoV-2. They were compared with 389 samples from donors who were infected with Covid-19.

“The researchers were able to show that people who deal with SARS-CoV-2 had lower levels of antibodies against the common cold coronavirus. In addition, SARS-CoV-2 infected people with high antibody levels against the harmless coronaviruses had to be hospitalized less frequently, “said a broadcast from the Swiss university.

Stronger antibody response

Study author Trkola commented on the results as follows: “According to our results, a stronger antibody reaction against human coronaviruses also leads to higher amounts of antibodies against SARS-CoV-2. A person who has immunity against harmless coronaviruses is therefore also better off from severe courses of SARS -CoV-2 infections protected. ” This cross-reactivity does not only occur with antibodies as part of the immune response. The same apparently also applies to the T cell immune response zu, the second pillar of the human immune system. Immune cells that act specifically against coronavirus-infected cells also fight SARS-CoV-2.

Do not rely on this immune response

However, one should by no means rely on such an immune reaction. The Covid-19 vaccination works much better here. the Antibodies against the harmless corona viruses are disappearing again. “But although the protection is not complete, cross-reactions shorten the course of the disease and alleviate its severity. And that is exactly what we achieve with vaccinations, only much, much more efficiently,” emphasized the scientist.

It is open whether this Cross reactivity also works the other way around. So whether an immunity to SARS-CoV-2 – for example through a vaccination – protects against other human coronaviruses. “If SARS-CoV-2 immunity also offers a certain protection against infection from other coronaviruses, we would come a big step closer to comprehensive protection against coronaviruses, including newly emerging variants,” the Zurich virologist was quoted as saying by her university. In any case, this assumption is supported by the fact that a cross-reactive protective effect is not only based on antibodies, but very likely also on T cells.

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