Volunteers were exposed to coronavirus as part of a scientific study
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By intentionally exposing people to the coronavirus that causes COVID-19, scientists have been able to understand why some people appear to be immune to infection.
As part of the first human COVID-19 challenge study conducted in 2021, an international group of researchers looked at 36 healthy people who had not tested positive for SARS-CoV-2 and had not been vaccinated.
The ancestral SARS-CoV-2 strain was sprayed into their noses. Nasal and blood samples were taken from 16 of the participants before exposure and then six to seven times over the next 28 days. All were also tested for SARS-CoV-2 twice daily.
Participants were split into three groups, team members said. Sarah Teichmann The study was conducted at the Cambridge Stem Cell Institute. In one group, six participants tested positive in both daily tests for more than two days and also had symptoms. In another group, three participants tested positive in one of two daily tests but not in the other and did not have symptoms, but for less than two days. In the final group, seven participants consistently tested negative for coronavirus.
In total, the researchers sequenced more than 600,000 blood and nasal cells across all subjects.
In the second and third groups, the researchers found that participants were producing more interferon (a substance that helps the immune system fight infection) in their blood in front of the nasopharynx (the top of the nose at the back of the throat where the nasal samples were taken). The interferon response was actually higher in the noses of participants in the second group than in the third group, Teichmann says.
These groups also did not have active infections within the immune cells T cells and macrophages, team members say. Marko Nikolic At University College London.
The results showed that high levels of gene activity HLA-DQA2 Exposure to SARS-CoV-2 helped prevent persistent infection.
Nikolic hopes that this discovery will improve understanding of the cellular responses involved in preventing COVID-19 and aid in the development of vaccines and treatments.
“With its carefully controlled design and real understanding of 'time zero' when infection occurs, this study will serve as a unique resource of previously uninfected SARS-CoV-2 participants to measure subsequent immune responses,” the study said. Jose Ordovas Montanez Harvard Stem Cell Institute
But most people have been exposed to “a true mosaic of SARS-CoV-2 variants,” not just the ancestral variant used in the study, so the results may not reflect cellular responses outside the testing environment, he says.
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Source: www.newscientist.com
