- Our immune systems have innate and adaptive responses, which include the production of antibodies
- Researchers have found that children's immune systems respond differently to Covid-19 than adults
- This might affect the way vaccines and treatments are targeted in the future
Early in the Covid-19 outbreak, evidence showed that children are likely to experience milder Covid-19 symptoms than adults.
A study published in Science Translational Medicine is the first to compare the immune responses of children and adults. This new research detected some key differences to explain the phenomenon.
What did the research entail?
For the research, scientists from the Albert Einstein College of Medicine, Children’s Hospital at Montefiore and Yale University investigated cases of 60 adult Covid-19 patients and 65 child patients (all younger than 24 years) between 13 March and 17 May 2020.
The scientists tested the patients’ blood for several types of immune cells, antibody responses and cytokines produced by immune cells.
The children’s immune responses looked significantly better than those of the adults. Twenty-two adults needed ventilation, in comparison with only five children, and 17 adults died compared to just two of the paediatric patients.
"Our findings suggest that children with Covid-19 do better than adults because their stronger innate immunity protects them against SARS-CoV-2, the novel coronavirus that causes the disease," said co-senior author Dr Betsy Herold, chief of infectious diseases and vice chair for research in the department of paediatrics at Einstein and CHAM.
What are the differences in the immune systems?
The authors explain the difference between our innate and adaptive immune systems. The innate immune system is responsible for fighting any invasive viruses or bacteria immediately, while the adaptive immune system builds up a long-term memory of pathogens and functions.
According to the authors, it seems like the innate immune systems of children are more robust than those of adults and thus protect them against the dire respiratory outcomes of Covid-19 – which may lead to death in severe adult cases.
One cytokine in particular, known as IL-17A, was found at much higher levels in paediatric patients than in adults, the researchers said. This may be an important protective mechanism against severe Covid-19.
Both children and adults with Covid-19 develop a level of antibodies, including spike-protein antibodies that fight the SARS-CoV-2 spike protein, as well as neutralising antibodies that try to block the virus from latching on to cells.
The researchers found that the levels of neutralising antibodies were higher in adults who died or required breathing assistance while in hospital.
"These results suggest that the more severe Covid-19 disease seen in adults is not caused by a failure of their adaptive immunity to mount T-cell or antibody responses," said Dr K. Herold from Yale School of Medicine, who co-authored the study. "Rather, adult patients respond to coronavirus infection with an over-vigorous adaptive immune response that may promote the inflammation associated with ARDS.”
How does this research benefit future Covid-19 treatment?
The findings of this study could be important for Covid-19 therapies and vaccines, said Dr Betsy Herold.
"Our adult Covid-19 patients who fared poorly had high levels of neutralising antibodies, suggesting that convalescent plasma, which is rich in neutralising antibodies, may not help adults who have already developed signs of ARDS. By contrast, therapies that boost innate immune responses early in the course of the disease may be especially beneficial," she stated.
Many of the vaccine candidates for SARS-CoV-2 are currently focusing on boosting neutral antibody levels, but with these insights, it may be vital to look at other ways to boost immunity, such as focusing on the innate immune response.
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