Coronaviruses are a group of different types of viruses. In humans, they are responsible for serious illnesses, such as Covid-19, but can also be just a simple cold. So is immunity the same for all forms of coronavirus?
- A new study reveals that patients who have not been infected have cells that react to the S protein contained in Sars-CoV-2.
- There would be cross-cellular immunity between Sars-CoV-2 and cold coronaviruses, but this does not guarantee the presence of antibodies.
Sras, MERS, colds, and more recently Covid 19… All these pathologies belong to the same viral family: coronaviruses. The panel is wide and the seriousness of the pathologies very different. The virus responsible for the Covid-19 disease is SARS-CoV2. But there are four other human coronaviruses, which have been present for a long time every winter. They are characterized by simple colds. Knowing that they are caused by viruses of the same family as SARS-CoV2, does the immunity induced by a cold protect us against Covid-19? Researchers believe that there could be cross-cellular immunity between different strains of coronaviruses of different lineages. In their study – which has been the subject of a pre-publication – they observe that patients who have not been contaminated nevertheless have cells which react to the S protein contained in Sars-CoV-2.
Immunity does not mean antibodies
To arrive at this result, the scientists compared a group of 18 people who had been infected with Sars-CoV-2 with another group of 18 people who tested negative. Their immune cells were tested in vitro with peptides composed of amino acids reproducing the sequence of the S protein of Sars-CoV-19. Thus, the researchers were able to detect whether the CD4 lymphocytes – which memorize a pathogen that they have already encountered – of the participants reacted to the S protein of Sars-CoV-2. Obviously, in the first group, they activated in the vast majority of cases. More surprisingly, this was also the case in 34% of Sars-CoV-2 seronegative patients: without having been sick, their CD4 lymphocytes reacted to the S protein of Sars-CoV-2. There would then be cross-cellular immunity between Sars-CoV-2 and cold coronaviruses. But immunity does not guarantee the presence of antibodies. Indeed, the group of seronegative patients were tested and all had antibodies against cold coronaviruses.
The researchers believe that their study could explain the different forms of Sars-CoV-2 in humans as well as the prevalence of this pathology in the elderly. The latter, throughout the year, protect themselves more from diseases than other age groups. Thus, they encounter less mild forms of the coronavirus and would have been less protected from Sars-CoV-2.
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