Why children’s immune systems would be better equipped to fight the coronavirus

The little ones are just a little Percentage COVID-19 infections, a trend that has intrigued scientists. Now, a growing body of evidence suggests why: the immune system of children appears to be better equipped to clear SARS-CoV-2 than that of adults. “Children are highly adapted to respond and very well equipped to respond to new viruses,” says Donna Farber, an immunologist at Columbia University in New York. Even when infected with SARS-CoV-2, toddlers are more likely to experience mild or asymptomatic disease.

Another clue that children’s response to the virus differs from that of adults is that some develop COVID-19 symptoms and specific antibodies to SARS-CoV-2, but never positive for the virus on a standard RT-PCR test. In one study, children under the age of ten in the same family developed antibodies against SARS-CoV-2, and two of them even had mild symptoms, but neither tested positive for RT-PCR, although it was tested 11 times in 28 days while they were in contact with their parents, who tested positive.

An immune switch

The children’s immune system sees the virus and “generates a very rapid and effective immune response that stops it, before it has a chance to replicate to the point of testing positive on a diagnostic swab test.” illustrates Melanie Neeland, an immunologist who has studied family, at the Murdoch Children’s Research Institute in Melbourne, Australia.

Even in children who have experienced the serious but rare complication called multisystem inflammatory syndrome in response to SARS-CoV-2 infection, studies have reported that the rate of positive results ranged from only 29% to 50%.

Farber says that the types of antibodies children develop offer clues as to what is going on. ANDIn an article of 32 adults and 47 children aged 18 or younger, she and her colleagues found that the children mainly produced antibodies to the SARS-CoV-2 spike protein, which the virus uses to enter cells. Adults generated similar antibodies, but they also developed antibodies against the core protein, which is essential for viral replication. Farber says whatThe “core protein is generally only released in large amounts when a virus is disseminated in the body”.

The children lacked specific nucleocapsid antibodies, “suggesting that they are not suffering from a generalized infection,” says Farber. Children’s immune responses “appear to be able to clear the virus before it replicates in large quantities”, to confirm.

In fact, it suggests that the reason children can neutralize the virus is that celulas pig t fils relativamente frankly. “T cells are part of the body’s adaptive immune system, which learns to recognize pathogens it encounters throughout its life,” he says. Maintains that “Since most T cells in children are not fully developed, they may have a greater capacity to respond to new viruses., a phenomenon which is studied in more detail ”.

But other evidence suggests the situation is not that simple: A study of people with COVID-19 that included children and youth under the age of 24, as well as adults, found they had a stronger response of T lymphocytes to the virus. protein as children and youth. But Farber claims that “The study measured the responses of memory T cells, which are much less developed in children, rather than naive T cell activity.”

“The ability of children to neutralize the virus could also be linked to the fact that have a strong innate immune response from birth says Alasdair Munro, who studies pediatric infectious diseases at University Hospital in Southampton, UK. It has been suggested that the speed and magnitude of your innate immune response could protect you against the onset of infection. But this effect is difficult to study and this raises the question of why it is not seen with other viruses that can cause serious illness in children ”.

The little ones are also the main reservoir of seasonal coronaviruses that cause colds. Some researchers have suggested that antibodies to these coronaviruses “may confer some protection against SARS-CoV-2, but the evidence is mixed,” confirms Munro.

Meanwhile, there is evidence that when children are exposed to the virus, they are given a lower dose than adults because their noses have fewer ACE2 receptors, which the virus uses to gain access to cells. Munro says it’s unlikely there is a single explanation why COVID-19 appears to affect children less than adults. “Biology is rarely that simple”, concludes.

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