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COVID-19: Nasal cell differences may contribute to milder COVID-19 in children
Epithelial and immune cells in the noses of children are primed for the detection of viruses, which may result in stronger early immune responses to SARS-CoV-2 infection than in adults, suggests a paper published in Nature Biotechnology. These findings may help to explain why children have a lower risk of developing severe COVID-19 symptoms.
Compared with adults, children have a reduced risk not only of developing severe COVID-19 but also of being infected by SARS-CoV-2 in the first place. However, little is known about the molecular mechanisms that might be responsible for this protection.
Roland Eils and colleagues investigated how the expression of genes in cells of the upper airways of patients with COVID-19 might vary between adults and children. Nasal swabs were taken from 45 patients who tested positive for SARS-CoV-2, of whom 24 were children (median age of 9 years; 10 female, 14 male) and 21 were adults (median age of 39 years; 12 female, 9 male). These were compared with samples from a control group of 42 healthy individuals who tested negative for SARS-CoV-2, of whom 18 were children and 23 were adults. Single-cell sequencing revealed that the children in this study had higher baseline levels of certain RNA-sensing receptors that are relevant to SARS-CoV-2 detection — such as MDA5 and RIG-I — in the epithelial and immune cells of their noses. This differential expression resulted in stronger early immune responses to SARS-CoV-2 infection in children than in adults. The nasal samples from these children were also more likely to possess distinct subpopulations of the immune cells known as T cells — for example, KLRC1 cytotoxic T cells, involved in fighting infection, and memory CD8+ T cells, associated with the development of long-lasting immunity.
The authors conclude that these findings may take us one step closer to understanding why children have a higher capacity for controlling the initial stages of SARS-CoV-2 infection than adults
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