The severe Covid-19 complication in children known as PIMS, could be triggered by dormant EBV in their bodies. — dpa
Scientists have identified a possible explanation for the severe inflammatory reaction known as PIMS (Paediatric Inflammatory Multisystem Syndrome) in children.
PIMS, which can occur in rare cases several weeks after a Covid-19 infection, is potentially life-threatening.
According to the study, the inflammatory shock is linked to the reactivation of another pathogen: the Epstein-Barr virus (EBV).
EBV, known as the cause of glandular fever, often goes unnoticed during infection.
Around 90% of people contract the virus at some point in their lives, doctors estimate.
While it can cause flu-like symptoms and require weeks of recovery, the virus remains dormant in the body even after the acute infection has passed.
Study author Dr Tilmann Kallinich, a paediatric rheumatologist at Berlin’s Charité hospital, explained that the virus embeds itself in various cells and persists in the body for life.
“It can reactivate years after the initial infection, e.g. when the immune system is weakened,” he said.
This reactivation was observed in children with PIMS, as detailed in the journal Nature.
The researchers found that the children’s immune systems, disrupted by the Covid-19 infection, could no longer suppress the dormant EBV infection.
It remains unclear whether the children had previously experienced symptomatic EBV infections or if the virus had gone unnoticed, said Dr Kallinich and co-author Dr Mir-Farzin Mashreghi, an immunologist and deputy scientific director of the German Rheumatism Research Centre (DRFZ).
Children with PIMS typically develop symptoms such as heart failure, high fever and skin rashes four to eight weeks after a SARS-CoV-2 infection.
About half of the affected children require intensive care.
However, the researchers noted that the condition is highly treatable, with most children making a full recovery.
The study examined 145 children aged two to 18 years, who were treated for PIMS between 2021 and 2023 in hospitals in Germany, France, Italy, Turkey and Chile.
For comparison, the researchers also studied 105 children who had recovered from Covid-19 without developing PIMS.
In about two-thirds of the children with PIMS, the researchers detected B-cells infected with EBV in their blood.
These findings were absent in children without PIMS.
B-cells, a type of white blood cell, work alongside T-cells, another type of white blood cell, to adapt the immune system to new pathogens.
All children with PIMS showed an increase in EBV-specific T-cells, strongly suggesting that EBV reactivation was responsible for the condition, Dr Mashreghi explained.
Additionally, 80% of the children with PIMS had EBV-specific antibodies, indicating that their bodies had attempted to fight the virus, but failed.
The study found that the failure to combat the virus was linked to an unusually high level of a signalling molecule called TGFß, produced by the children’s bodies in response to the Covid-19 infection.
This molecule suppresses immune cell function, reducing the body’s ability to fight EBV.
As a result, the virus multiplies, prompting the body to produce more immune cells that remain ineffective.
“This ultimately leads to an extreme inflammatory reaction, which can damage organs and potentially be fatal,” Dr Mashreghi explained.
The findings could also be relevant for other Covid-19-related conditions, such as long Covid, which involves long-term health effects following a Covid-19 infection.
There is evidence that the reactivation of dormant viruses may play a role in long Covid.
“There may be parallels to the processes observed in PIMS, which would make TGFß inhibitors potential candidates for long Covid treatment,” Dr Mashreghi said. – By Mia Bucher/dpa
