Covid-19: the mystery of naturally protected people finally solved?

A recent study finally helps explain why some people seem immune to Covid, even without a vaccine.

Its authors hope that these results will contribute to the development of additional vaccines and treatments.

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Covid-19: life with the virus

If vaccines help protect against serious forms of Covid-19, some of us would already have the resources to fight the disease, thanks to our genetic heritage. Advanced in 2021 in the midst of a health crisis, this avenue is now supported by science, and it is even possible to explain why. In the patients concerned, a particular immune response localized at the level of the nasopharyngeal mucosa would prevent the virus from spreading and causing a prolonged infection, detail the results of this work recently published in the journal Natureand relayed by the New Scientist.

“Not only will these findings have an important impact on the development of next-generation interventions against SARS-CoV-2, but they should also be generalizable to other future epidemics and pandemics,” points out Christopher Chiu of Imperial College London, who led the study among Nature.

High interferon response at the nasopharyngeal level

To achieve these results, the international team led by Imperial College London analyzed in detail the immune responses immediately after infection of 16 healthy volunteers with no history of SARS-CoV-2 infection or vaccination after inoculating them with the virus nasally. In detail, nasal and blood samples were taken before exposure, then six to seven times over the following 28 days and patients were tested twice a day during the experiment.

Verdict: Researchers have discovered specific immune response sequences never before observed. Among the 16 volunteers, six tested positive for more than 48 hours and presented symptoms, three tested positive during the first tests, but did not have symptoms and seven others tested negative despite exposure to the virus. and did not have any symptoms either. However, the researchers observed that the response to interferons was significantly higher at the nasopharyngeal level, which would have made it possible to prevent the infection from lasting long and deep.

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“This was a unique opportunity to see what immune responses look like upon encountering a new pathogen, in adults without a history of Covid-19, in a context where factors such as timing of infection and comorbidities could be controlled”, Rik Lindeboom of the Dutch Cancer Institute and co-senior author of the study further commented in a press release. By offering a better understanding of these responses, these results open the way to the possibility of developing new therapeutic or vaccine strategies, targeted in particular by T cells for both Covid and other infectious diseases.

Note, however, that the study only concerns the original strain of SARS-CoV-2 and therefore none of these new variants. These results may therefore not accurately reflect immune responses, as the majority of people are now exposed to different strains of the virus.


Audrey LE GUELLEC

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