The linings of children’s noses are better at inhibiting SARS-CoV-2 infections than adult noses, researchers report.
That might be one reason why children’s immune responses have so far proven more effective at avoiding and fighting COVID-19, says Kirsty Short from the School of Chemistry and Molecular Biosciences at the University of Queensland.
“Children have a lower COVID-19 infection rate and milder symptoms than adults, but the reasons for this have been unknown,” Short says.
“We’ve shown the lining of children’s noses has a more pro-inflammatory response to the ancestral SARS-CoV-2 than adult noses. But we found it’s a different ball game when it come to the Omicron variant.”
The researchers exposed the samples of nasal lining cells from 23 healthy children and 15 healthy adults to SARS-CoV-2.
The results show the virus replicated less efficiently in the children’s nasal cells, as well as a heightened antiviral response. Short says there are a number of theories why.
“It could be an adaptation to the increased threats of ‘foreign invaders’ such as viruses or bacteria observed in childhood,” she says.
“It’s also possible that increased exposure to these threats in childhood ‘trains’ the nasal lining in children to mount a stronger pro-inflammatory response. Or alternatively, metabolic differences between children and adults could alter how virus-fighting genes express themselves.”
The researchers found the Delta COVID-19 variant was significantly less likely to replicate in the nasal cells of children compared to adults. But the trend was markedly less pronounced in the case of Omicron.
“Taken together, it shows children’s nasal lining supports lower infection and replication of ancestral SARS-CoV-2, but this may be changing as the virus evolves,” Short says.
“Future clinical studies will be needed to validate these preliminary findings in a larger population and to determine the role of other factors, such as antibodies in protecting children from SARS-CoV-2 infection.”
The research appears in PLOS Biology.
Source: University of Queensland