Our body develops an immune memory that allows it to cope with the common cold Coronaviruses to which we are exposed since childhood. A strategy that could also prove useful to fight Covid-19 by mimicking the same mechanism through which the immune system builds its defenses against the Coronaviruses of the cold. Scientists from the La Jolla Institute for Immunology are investigating this possible strategy and recently published in the journal Cell Host & Microbe a new study starting from the observation that in adults, antibodies and T cells are stably activated to fight the flu coronaviruses probably thanks to multiple exposures during childhood. Thanks to this army of immune cells, coronavirus infections of the adult cold tend to be rare and mild.
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Challenges for the immune system
With the Omicron 5 sub-variant on the loose, more and more people become infected and reinfections are also on the rise. “Everyone is wondering where we are going to end up: should we continue to receive boosters or modify vaccines?” Says the professor. Alessandro Sette of the Center for Infectious Disease and Vaccine Research at La Jolla Institute. These questions have prompted Sette and her colleagues to question whether Coronaviruses pose ‘special challenges’ to the immune system. Sars-CoV-2 has been around for just two years and has continued to evolve throughout this time, but researchers have been examining the long-term immune memory of common cold coronaviruses to better understand what lies ahead.
Research
In order not to confuse the data, the researchers needed to analyze samples from people never exposed to Sars-CoV-2. Fortunately, they had taken blood samples for a previous study launched at the La Jolla Institute before the pandemic. The patients in this group were all young adults and it was safe to assume that they had been exposed multiple times to the common cold coronaviruses.
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The ‘memories’ of immune cells
As anyone with young children knows, colds hit them over and over again throughout childhood. These childhood diseases require strong immune memory. As children face the challenge of nursery germs, their immune systems are also educated. In fact, the researchers found that adults have stable immune memory and tend to contract cold coronaviruses only about every eight years. “The immune response is extraordinarily stable and long-lasting,” he says Ricardo Da Silva Antunes who co-directed the study with Professor Sette.
What do coronaviruses have in common?
Sars-CoV-2 is different from the common cold coronaviruses, but there are many structural similarities, and previous work at the La Jolla Institute suggests that the immune system recognizes these similarities between different coronaviruses. In this new study, the researchers also showed that antibodies and T cells from the healthy adult group could cross-react with Sars-CoV-2. This cross-reactivity may actually help protect against severe Covid-19, and the finding reinforces the idea that the immune system ‘sees’ common cold coronaviruses and SARS-CoV-2 in a similar way.
Towards mass immunity
If the observed pattern in common cold Coronavirus immunity also holds for Sars-CoV-2, as immunity builds up in the population, reinfections should become less frequent over time and Covid-19 symptoms should be less severe. . The arrival of new variants can complicate the immunity-building process, but “there’s certainly reason to assume this will eventually be the end result, but we’re not there yet,” says Sette.
Don’t let your defenses down
There’s a good chance Sars-CoV-2 is here to stay. A pathogen that maintains a constant level in a community and does not cause everyday problems is called ‘endemic’, but this unfortunately does not mean that it is less dangerous. Influenza, for example, is endemic, and while most people are not life-threatening, the flu virus still killed 53,544 Americans in 2020 alone (and that was fewer than usual). In Italy, the flu affects about 5/6 million people every year and accompanies the death of almost ten thousand every winter. Not only. The La Jolla researchers point out that the endemic SARS-CoV-2 would still be severe and for this reason they agree that the best strategy right now is for people to keep getting vaccine boosters.