Everyone is familiar with the “novel Sars-CoV-2” coronavirus, which is currently raging – after all, it is the cause of a pandemic. But it is by no means the first and only. Contact with more harmless coronaviruses, some of which just cause a simple cold, can, however, help the immune defense against the more dangerous, more recent ones, shows a study from Switzerland.
Coronaviruses are not new at all. They were first described in the mid-1960s, over half a century ago. They can cause infectious diseases in all four classes of terrestrial vertebrates – mammals, birds, reptiles, amphibians. Seven types of coronavirus are important in humans. The spectrum of diseases that they can trigger is wide: it ranges from mild respiratory infections (colds, flu-like infections) to “severe acute respiratory syndrome” (English: Severe acute respiratory syndrome, abbreviation: Sars), which has existed since the beginning of the The current pandemic has claimed more than 100,000 deaths in Germany alone.
Vaccination and recovery: Strongest protection against Covid-19
The immune protection of the population against Sars-CoV-2, which is particularly dangerous within the coronavirus family, is crucial for coping with the Covid-19 pandemic. It can be built up in two ways: either by vaccination; or through a contagion and a happy infection.
Contact with other coronaviruses: Third type of immunity
A research team led by the University of Zurich (UZH) has now identified another component that contributes to Sars-CoV-2 immunity: existing antibody reactions against other, harmless coronaviruses with which one has come into contact before. The most important result in advance in one sentence: “People who have pronounced immune responses to human coronaviruses are also protected to a certain extent from infection with Sars-CoV-2,” says Alexandra Trkola, head of the Institute for Medical Virology at UZH .
In their coronavirus project, the researchers analyzed two things with a specially developed test method: First, the amount of different antibodies against the four other currently circulating human coronaviruses. To do this, they examined the blood serum of 825 donors from before the occurrence of Sars-CoV-2. Second, they analyzed 389 samples from donors who had become infected with Sars-CoV-2 in the course of the pandemic. “Combined with computer-aided modeling, this analysis enables precise predictions of how well the antibodies bind to invading viruses and neutralize them,” says a statement from the University of Zurich.
Antibodies against harmless coronaviruses protect against severe cases and hospital
The researchers were able to show: Those test subjects who were infected with Covid-19 only had lower amounts of antibodies against the cold coronavirus in their blood – i.e. less contact with them in the time before. Second, it was shown: Covid-19 patients who had high antibody levels against the harmless coronaviruses did not have to be treated in hospital as often.
“Cross-reaction”: Immunity to one virus can protect against another
“According to our results, a stronger antibody reaction against human coronaviruses also leads to higher amounts of antibodies against Sars-CoV-2,” says microbiologist Trkola. “A person who has immunity to harmless coronaviruses is thus better protected against severe courses in the event of a Sars-CoV-2 infection.” In science, this is referred to as a “cross reaction”. This also occurs in the immune reaction of T cells, the second pillar of the human immune system.
Shortened course of the disease, milder symptoms
How are the current findings from Switzerland on corona immunity to be classified? People have the best protection against Sars-CoV-2 directly after an infection or after an effective vaccination. Then the levels of antibodies against the virus are still very high. If their concentration drops over time, infection is no longer prevented, but the memory cells quickly reactivate the immune system – both the production of antibodies and the T-Zellabwehr. “Specific immune reactions directed against Sars-CoV-2, which originate from memory cells, are of course far more effective than cross-reactive ones,” says virologist Trkola. “But although the protection is not complete, shorten it Cross reactions the course of the disease and alleviate its severity. And that’s exactly what we achieve with vaccinations, only much, much more efficiently. “