Exposure to harmless coronaviruses boosts immunity to COVID-19

Strong antibody responses against harmless coronaviruses also partially protect against SARS-CoV-2.

Novel coronavirus infections and vaccination lead to strong antibody responses against SARS-CoV-2. Immune responses to other human coronaviruses, most of which only cause harmless colds, also offer some protection against SARS-CoV-2. This cross-immune response is an important piece of the puzzle of how to achieve full immunity against coronaviruses, researchers from the University of Zurich have shown.

The immunity of the population against SARS-CoV-2, achieved either by infection or by vaccination, is crucial to overcome the COVID-19[female[feminine pandemic. A team of researchers led by the University of Zurich (UZH) has now discovered another component that contributes to immunity against SARS-CoV-2 – previous antibody responses to other harmless coronaviruses. “People who have had strong immune responses to other human coronaviruses also have some protection against infection with SARS-CoV-2,” says Alexandra Trkola, director of the Institute of Medical Virology at UZH .

In their study, the researchers used a specially developed test to analyze the levels of antibodies against four other human coronaviruses in 825 serum samples collected before the emergence of SARS-CoV-2. They also examined 389 samples from donors infected with SARS-CoV-2. Combining these analyzes with computer models allowed the team to accurately predict how well the antibodies would bind to and neutralize the invading viruses.

Cross-reactivity reduces the severity of infection

Researchers were able to show that people who caught SARS-CoV-2 had lower levels of antibodies to the coronaviruses that cause common colds than people without the infection. Additionally, people with high levels of antibodies to harmless coronaviruses were less likely to have been hospitalized after contracting SARS-CoV-2. “Our study shows that a strong antibody response to human coronaviruses increases the level of antibodies against SARS-CoV-2. Thus, a person who has acquired immunity against harmless coronaviruses is therefore also better protected against serious infections with SARS-CoV-2, ”explains Trkola. This type of immune response is called cross-reactivity and also occurs with T cell responses, the immune system’s additional line in defense against infection.

Strong antibody responses against harmless coronaviruses

Strong antibody responses against harmless coronaviruses also partially protect against SARS-CoV-2. Credit: University of Zurich

People are not fully protected against SARS-CoV-2 until soon after recovering from an infection or receiving an effective vaccination. This is when the antibody levels against the virus are still very high. As these levels decline over time, infection is no longer prevented, but immunological memory quickly reactivates the body’s defenses, antibody production as well as T cell defense. “Good Of course, immune responses targeting SARS-CoV-2 that are mounted by memory cells are much more efficient than cross responses. But even if the protection is not absolute, the crossed immune responses shorten the infection and reduce its severity. And that is exactly what is also achieved through vaccination, just much, much more effectively, ”says Trkola.

Towards comprehensive protection against coronaviruses

It is not yet clear whether this cross-reactivity also works in the opposite direction. It remains to be seen whether immunity against SARS-CoV-2 – achieved through vaccination, for example – also offers protection against other human coronaviruses. “If immunity against SARS-CoV-2 also provides some degree of protection against infection with other coronaviruses, we would take a further step towards achieving full protection against other coronaviruses, including any new variant, ”explains the virologist. This idea is also supported by the fact that the cross-reactive protection is not only based on antibodies, but most likely also on T cells.

Reference: “Multifactorial seroprofiling dissects the contribution of pre-existing human coronavirus responses to SARS-CoV-2 immunity” by Irene A. Abela, Chloé Pasin, Magdalena Schwarzmüller, Selina Epp, Michèle E. Sickmann, Merle M. Schanz , Peter Rusert, Jacqueline Weber, Stefan Schmutz, Annette Audigé, Liridona Maliqi, Annika Hunziker, Maria C. Hesselman, Cyrille R. Niklaus, Jochen Gottschalk, Eméry Schindler, Alexander Wepf, Urs Karrer, Aline Wolfensberger, Silvana K. Rampini, Patrick M. Meyer Sauteur, Christoph Berger, Michael Huber, Jürg Böni, Dominique L. Braun, Maddalena Marconato, Markus G. Manz, Beat M. Frey, Huldrych F. Günthard, Roger D. Kouyos and Alexandra Trkola, November 18, 2021, Nature Communication.
DOI: 10.1038 / s41467-021-27040-x

The study was funded by the University of Zurich’s Pandemic Fund, the Swiss Red Cross, the University Hospital of Zurich, the Swiss National Science Foundation and Gilead.

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