The novel coronavirus and vaccination lead to a strong immune response against SARS-CoV-2. SARS-CoV-2 protection can also be achieved through immune responses to other human Coronaviruses. These viruses are generally harmless and rarely cause serious illness. This immune system response that is cross-reactive is an essential element of how to attain a comprehensive coronavirus immunity, scientists at the University of Zurich have shown.
To combat the COVID-19 pandemic it is crucial that the population is protected to SARSCoV-2. This immunity can be achieved via vaccination or infection. A group of researchers under the direction of the University of Zurich (UZH) has discovered a second component that plays a role in the SARS-CoV-2 immune system prior antibodies to other harmless coronaviruses. “People who have been able to show strong immune responses to other human coronaviruses also have some protection against SARS-CoV-2 infection,” says Alexandra Trkola, head of the Institute of Medical Virology at UZH.
The researchers developed a custom assay to test for antibodies against four other human coronaviruses. They examined 825 serum samples prior to when SARS-CoV-2 was identified. They also examined 389 samples from people who were infected by SARS-CoV-2. Combining these analyses with computer-based models allowed the team to accurately predict how the antibodies would bind to and neutralize invading viruses.
Cross-reactivity can reduce the severity of the infection
The researchers were able prove that those who contracted SARS-CoV-2 had lower levels of antibodies against coronaviruses that trigger common colds compared to uninfected people. In addition, those who had high levels of antibodies against harmless coronaviruses were less likely to be hospitalized following the onset of SARS-CoV-2. “Our study indicates that a strong immune response to human coronaviruses boosts the level of antibodies against SARS-CoV-2. Thus, a person who has acquired immunity to harmless coronaviruses is more protected from severe SARS-CoV-2 infection,” says Trkola. This type of immune response is known as cross-reactivity. It also occurs in combination with T cell reactions which are the additional line of defense against infections.
The majority of people are protected from SARS-CoV-2 when they have recovered from infection or have received a successful vaccination. This is when antibody levels against the virus remain extremely high. These levels decrease over time and infection cannot be prevented. However the immune memory rapidly restores your body’s defenses allowing for the production of antibodies and T cell defense. “Of course, immune responses targeting SARS-CoV-2 that are mounted by memory cells are far more effective than cross-reactive responses. Cross-reactive immune responses can lessen the severity and increase the duration of the disease even though they aren’t 100 100%. Trkola states that vaccination is also effective in decreasing the severity of infection.
Towards comprehensive protection against coronaviruses
It is not known whether this cross-reactivity occurs in the reverse direction. It isn’t certain if immunity to SARS CoV-2 – obtained through vaccination, for example can also protect against other human coronaviruses. The virologist stated that if the immunity conferred by SARS-CoV-2 offers some protection against infection by other coronaviruses, it would be a major step closer to achieving total protection against all coronaviruses. This idea is also supported by the fact that cross-reactive immunity is not solely based on antibodies, it is also likely to be based on T cells.
Abela, I.A., Abela, I.A.. (2021) Multifactorial seroprofiling delves into the role of human coronaviruses that are already present to SARS-CoV-2 immunity. Nature Communications. doi.org/10.1038/s41467-021-27040-x.
