Innate immunity responds rapidly to invading pathogens of all kinds
Scientists at Albert Einstein College of Medicine, Children’s Hospital at Montefiore (CHAM) conducted a study comparing the immune responses of adults and children with COVID-19. They detected key differences that may contribute to understanding why children usually have milder disease than adults.
The study published in Science Translational Medicine says that the findings also have important implications for vaccines and drugs being developed to curb COVID-19.
Scientists studied 60 adult COVID-19 patients and 65 pediatric COVID-19 patients (less than 24 years old) over a period of 3 months between March 13 and May 17, 2020. The study found 20 of the pediatric patients had the novel multi-system inflammatory syndrome (MIS-C). Their blood was tested for the presence of several types of immune cells, antibody responses, and the inflammatory proteins, known as cytokines, that immune cells produce.
- 22 adults (37%) required mechanical ventilation compared with only five (8%) of the pediatric patients.
- 17 adults (28%) died in the hospital compared with two (3%) of the pediatric patients. No deaths occurred among pediatric patients with MIS-C.
Children do better than adults
The findings suggest that children with COVID-19 fared significantly better than adults because their stronger innate immunity protects them against SARS-CoV-2.
People have two types of immunity—innate and adaptive.
Innate immunity is more robust during childhood in which immune cells respond rapidly to invading pathogens of all kinds.
Adaptive immunity—more specific and features antibodies and immune cells that target specific viruses or other microbes.
Compared with adult patients, pediatric COVID-19 patients possessed significantly higher levels of certain cytokines associated with the innate immune response. This suggests that young people’s strong and healthy response protects them from developing acute respiratory distress syndrome (ARDS)—the hallmark of severe and often fatal COVID-19 cases. One cytokine in particular, known as IL-17A, was found at much higher levels in pediatric patients than in adults.
“The high levels of IL-17A that we found in pediatric patients may be important in protecting them against progression of their COVID-19”, said Dr. Kevan C. Herold, M.D., C.N.H. Long Professor of Immunology and of Medicine at Yale School of Medicine.
The study found that both pediatric and adult COVID-19 patients make antibodies against the coronavirus’ spike protein, which the virus uses to latch onto and infect cells. These spike-protein antibodies include neutralizing antibodies, which block the coronavirus from infecting cells. It makes sense that neutralizing antibody levels in adult COVID-19 patients who died or required mechanical ventilation were higher than in those who recovered—and significantly higher than levels detected in pediatric patients.