Aditi Tandon

Tribune News Service

New Delhi, July 10

The immune systems of children are better placed to fight Covid-19 due to the nature of the antibodies they produce, a new research has found.

Published in PubMed, the digital repository that archives work published in the world’s leading journals, the study shows that distinct antibody response children develop to Covid-19 explains the mild nature of illness they experience as against adults who tend to progress to severe Covid.

The study reveals that children produce antibodies aimed at the spike protein the virus uses to enter human cells, while adults develop antibodies to what is called the nucleocapsid protein, which is key to viral replication in the body.

The nucleocapsid protein is released when the virus has replicated enough in the body and is widely prevalent. Children don’t produce antibodies to nucleocapsid protein which indicates their immune system’s ability to fight the virus before it replicates. This could answer why children get mild and asymptomatic Covid.

“Clinical manifestations of Covid-19 are associated with age. Adults develop respiratory symptoms, which can progress to acute respiratory distress syndrome in the most severe form, while children are largely spared from respiratory illness but can develop a life-threatening multisystem inflammatory syndrome. We see distinct antibody responses in children and adults after SARS-CoV-2 infection,” the researchers say.

They find that adult Covid-19 cohorts have anti-spike antibodies as well as anti-nucleocapsid antibodies, while children with and without MIS-C predominantly generate antibodies specific to spike protein but not the N-protein. “The results suggest a distinct infection course and immune response in children,” the study notes, explaining in part why children, even with antibodies to Sars-Cov2, do not turn up RTPCR positive. They don’t have enough viral load to be caught by an RTPCR test.

Commenting on the new evidence that explains why children’s immune systems are better trained to respond to Covid, paediatric expert Vipin Vashishtha says the reason children can neutralise the virus is also that their T cells are relatively naive and untrained and may have a greater capacity to respond to new viruses.

Response to novel viruses

• Children’s immune systems can ward off the virus before it replicates, which explains why they get mild disease unlike adults
• Their T cells are relatively naive and untrained and may have a greater capacity to respond to new viruses
• Among Covid-positive children, 3-4% are less than 10 years old