According to a new study published Thursday, children infected with coronavirus produce weaker antibodies and fewer types of antibodies than adults, suggesting they clear the infection much faster.
Other studies have suggested that an overly strong immune response could be the cause in people who become seriously ill or die from Covid-19. Poor immune responses in children may paradoxically kill the virus before it has had a chance to wreak havoc on the body and may help explain why children most likely do not experience symptoms. a serious illness of Covid, a disease caused by the coronavirus. It may also show why they are less likely to spread the virus to others.
“They can be infectious for a shorter time,” said Donna Farber, an immunologist at Columbia University in New York who led the study reported in the journal Nature Immunology.
Other experts say having fewer and weaker antibodies does not mean that children are at greater risk of re-infection.
“You don’t really need an immune response that’s too strong and too strong to maintain protection for a while,” said Deepta Bhattacharya, an immunologist at the University of Arizona in Tucson. “I didn’t know that I would be particularly worried that children have slightly lower antibody responses.”
The study looked at children’s antibody levels at a single point in time and were too young to provide insight into how levels might change with age. But it may raise questions for certain antibody tests that might be missing in already infected babies.
Dr. Farber and her colleagues analyzed antibodies to the coronavirus in four groups of patients: 19 adults recovering well-recovered plasma donation from Covid’s disease without hospitalization; 13 adults hospitalized with severe Covid-induced acute respiratory distress syndrome; 16 children were admitted to the hospital with multisystem inflammatory syndrome, a rare condition affecting some of the infected children; and 31 infected children do not have the syndrome. About half of these last children have no symptoms.
The individuals in each group have antibodies, consistent with other studies showing that the vast majority of people infected with coronavirus have strong immune responses.
“This further emphasizes that the viral infection itself and the immune response to the virus are not different from what we would expect,” said Petter Brodin, an immunologist at Karolinska Institutet in Stockholm.
But the antibody range differs between children and adults. The babies mainly make an antibody, called IgG, that recognizes a protein spike on the surface of the virus. Adults, by contrast, make certain types of antibodies to spikes and other viral proteins, and these antibodies have a more potent antiviral effect.
“Children have less protective reactions, but they also have less antibody reactions,” says Dr Farber. “That’s because those kids didn’t have serious infections.”
Neither group of children has antibodies to a virus protein called nucleocapsid, or N, that is involved in the virus’s genetic material. Since this protein is found inside the virus and not on its surface, the immune system will only see it and produce antibodies to it if the virus is widespread in the body, she said.
“You don’t really see that in children, and it shows that there is actually a reduction in infection if these kids are infected,” she explains.
This finding could weaken the results from tests designed to acquire antibodies to the viral N protein. Many antibody tests, including those performed by Abbott and Roche and provided by Quest Diagnostics and LabCorp, are specific to N antibodies and can therefore miss children who have successfully eliminated the virus. . “That’s quite an interesting implication of that finding,” said Dr. Brodin.
Lower levels of the virus in the body will also explain why children are generally less effective at transmitting the virus than adults.
But experts recommend some caution in interpreting the results because they represent samples taken from people at a single point in time.
Samples from severely affected children and adults were collected within 24 to 36 hours of hospitalization or intubation for respiratory failure; children with mild or asymptomatic rash following medical procedures.
The type of antibodies produced by the body change over the course of the infection. This is a limitation of this study because researchers may have compared people at different points in their infection, Dr. Brodin said. “You risk comparing apples and oranges.”
Other experts warn that the study is too small to draw conclusions about how the immune response may differ in children of different ages. The children in the study ranged in age from 3 to 18 years, with an average age of 11. But some studies have suggested that adolescents may be as at risk of coronavirus as adults.
Dr. Maria L. Gennaro, an immunologist at Rutgers University, said: “It is very important to understand what happens in children,” the nature of their illnesses, as well as how they contribute to spread the virus in the community. But “to try and stratify by age, it’s going to be a bit stressful,” she says.
The researchers also cannot explain why children have more limited antibody responses.
“Having less antibodies seems to be a bad thing, but” having more antibodies is not necessarily a sign of a good thing, “Dr. Bhattacharya said. “It usually means something goes wrong early on in the response.”
At least one other study has suggested that children have a strong innate immune system, aimed at fighting the many new pathogens they encounter, and that this first line of defense could get rid of infections early. there is no need to rely on antibodies in the future.
Another possibility is that the babies have some protection – in the form of immune cells called memory T cells – from previous encounters with the common cold coronavirus.
“Are all innate? Or maybe there was some pre-existing memory? “Dr. Bhattacharya said.” I think both are possible. “