Young nose cells may help children fight off Covid
Children are less likely than adults to develop severe Covid, because cells in their nose are better at fighting off the virus, a study suggests.
Lab tests show ageing adult nose cells contain 100 times more virus in the first few days after an infection.
The lab discovery could explain why older adults are hit worst by Covid and children are rarely very ill.
Anti-viral treatments should be tailored to different age groups, the UK researchers say.
The nose is the first place Covid enters the body - so scientists wanted to look in detail at what happens inside this so-called viral production factory.
Researchers analysed cells from the nose lining of healthy people from three different age groups - under-12s, 30-50 year olds and over 70s.
They then grew the nasal cells in lab dishes, infected them with coronavirus, and watched closely.
Three days later, viewed under a microscope, the nasal epithelial cells - as they are known - taken from children were quick to defend against the virus and reduce viral load.
But this protective effect was less obvious in middle-aged adults. And in nose cells from the over-70s, there was more virus, more shedding and more damage.
Dr Claire Smith, study leader and associate professor from University College London, said age affected the balance of cells in the nose, leading to a "detrimental, dysfunctional repair" process in older people.
This could be because they have had greater exposure to viruses over time and more infections.
The risk of being dangerously ill with Covid rises with age, which is why over-75s - as well as everyone in an adult care home or with a weakened immune system - is offered a vaccine in the UK.
Dr Smith said the findings, in Nature Microbiology, highlighted how important it was to take ageing into account when looking at treatments and therapies.
The research team now wants to look at how the body - and the nose - responds to other viruses, such as flu and respiratory syncytial virus (RSV).
"Understanding the cellular differences at the initiation of infection is just the beginning," Dr Smith said.
"We now hope to investigate the long-term implications of these cellular changes and test therapeutic interventions using our unique cell culture model."
The nose cells were sampled in February 2020, during the first wave of Covid - so how the body's reaction to the initial strain of the virus compares with the current circulating variant, Omicron, remains unclear.
The researchers said more work was needed to discover whether the level of infectious virus in the nose cells affected the spread of Covid.
The research, by UCL and the Wellcome Sanger Institute, was funded by UK Research and Innovation, the NIHR Great Ormond Street Hospital Biomedical Research Centre and the Chan Zuckerberg Foundation.
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