Covid-19
DELIBERATELY exposing people to the coronavirus behind covid-19 in a so-called challenge study has revealed why some people seem to be immune to catching the infection.
As part of the first such work using the SARS-CoV-2 pathogen, which was carried out in 2021, a group of international researchers looked at outcomes for 16 people. All had no known health conditions and hadn’t tested positive for the virus or been vaccinated against it.
To try to deliberately infect them, Sarah Teichmann at Cambridge Stem Cell Institute in the UK and her colleagues sprayed the original variant of SARS-CoV-2 up their noses. The researchers took nasal and blood samples before this and then six to seven times over the 28 days after. SARS-CoV-2 tests were done twice a day.
Following exposure to the virus, the participants fell into three groups, says Teichmann. In one, six people tested positive in both of their daily tests for more than two days, while also having symptoms. In another, three participants tested positive in one of their twice-aday-tests, but not the other, for no more than two days, without symptoms. In the final group, seven people consistently tested negative for the coronavirus.
In total, the researchers also looked at more than 600,000 blood and nasal cells taken from all the individuals. Teichmann and her colleagues found that in the second and third groups, the participants produced interferon – a substance that helps the immune system fight infections – in their blood before it was produced in their nasopharynx, the upper part of the nose behind the throat. This is the place where the nasal samples were taken from.
16 Number of people deliberately exposed to SARS-CoV-2 virus
7 This many of them consistently tested negative for the v
