Some people who have never contracted CoViD-19 have immune defenses capable of activating against SARS CoV-2 – perhaps because they retain memories of a past encounter with other coronaviruses, responsible for common colds. This is indicated by a study conducted by the University of Berlin and the Max Planck Institute for Molecular Genetics, which has not, however, made it possible to determine whether these immune defenses can play a protective role at the different stages of the disease. . The research has been published in Nature.
This virus is familiar … Why do some people develop very severe covideal symptoms while others get mild or asymptomatic disease? The question is complex and does not have a straightforward answer, but over time it has raised suspicion that certain immune responses to CoViD-19 could be what experts call cross-reactions. In practice, the body retains the memory of something that looks like SARS-CoV-2 (but it isn’t) and organizes its defenses accordingly.
The results of the new study confirm this hypothesis, which has yet to be clinically tested. Coronaviruses are a large family of viruses that cause infections ranging from the common cold to more serious respiratory illnesses and potentially more serious illnesses like SARS, MERS, and CoViD-19. In Germany, where the study was conducted, less aggressive coronaviruses are responsible for up to 30% of seasonal colds.
Precious memories. The team isolated immune cells from the blood of 18 patients with covariectomy and 68 healthy blood donors. In the laboratory, the cells were stimulated with synthetic fragments of the SARS-CoV-2 spike protein. The researchers wanted to see if stimulation with this antigen could activate helper T lymphocytes, white blood cells that trigger the release of cytokines, proteins that regulate the immune response. As expected, in 15 of 18 patients, helper T cells answered the call, busting up to defeat the virus: after all, they did the same in patients’ bodies.
More surprising was the discovery that – in healthy patients – the memory cells of T helper lymphocytes, i.e. lymphocytes destined to survive for a long time, were able to recognize fragments of SARS CoV-2 ( although, theoretically, they never met him). In 24 out of 68 patients, there was activation: it was not the full length of the spike protein that was recognized, but only the sections that showed similarities to the spike proteins of cold coronaviruses. In healthy patients, T-auxiliaries reacted in this way precisely because of previous exposure to harmless coronaviruses.
What’s the point ? Further studies already planned by the same research group should examine the role of the cross-reaction in the course of the disease and the possibility of infection. The long-remembered T-auxiliaries may have a protective effect because they help the body to produce antibodies and, for example, promote a milder manifestation of symptoms; but the reverse could also occur, that is to say a badly directed immune reaction, with a more serious development of the infection.