The findings suggest why children tend to experience milder symptoms compared to older adults.
Researchers from University College London (UCL) and the Wellcome Sanger Institute have revealed how specific nasal cells differ in children and elderly people when protecting against COVID-19.
Published in Nature Microbiology, the study used cells donated from healthy participants from Great Ormond Street Hospital, University College London Hospital and the Royal Free Hospital.
Researchers focused on the early effects of the SARS-CoV-2 infections using the human nasal epithelial cells (NECs) gathered from children aged up to 11 years, adults aged 30 to 50 years, as well as elderly people aged over 70 years.
After using specialised techniques to regrow these cells into the different types usually found in the nose, researchers used single-cell RNA sequencing to identify the genetic networks and functions of thousands of individual cells to identify 24 epithelial cell types.
The cell cultures from each age group were then either mock-infected or infected with SARS-CoV-2.
After three days, the NECs of children responded rapidly to the virus by increasing interferon, the anti-viral defence in the body, which restricted viral replication.
As the age of people increased, researchers observed that this early anti-viral effect became less apparent – not only did NECs from elderly individuals produce more infectious virus particles, they also increased cell shedding and damage, potentially linking to the greater severity of disease typically observed in older adults.
The team suggests that the strong antiviral response in the NECs of children could explain why younger people tend to experience milder symptoms, while underscoring the importance of age in research and the treatment of infectious diseases.
Dr Claire Smith, associate professor at UCL and Great Ormond Street Institute of Child Health, said: “Our research… could be crucial in developing effective anti-viral treatments tailored to different age groups.”
She added: “We now hope to investigate the long-term implications of these cellular changes and test therapeutic interventions using our unique cell culture model” to research how ageing can impact the body’s response to other viral infections.