Inflammatory syndrome in children is not caused by a special strain of coronavirus

The world’s first genetic study of coronavirus from children with inflammatory syndrome PIMS-TS, led by researchers at the UCL Great Ormond Street Institute of Child Health (ICH), suggests characteristics of the human host, rather than of the virus itself, are likely to make children more susceptible to the syndrome.

While children rarely experience severe COVID-19 symptoms, a small number develop paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) after infection with the virus. In rare cases, this syndrome can be life-threatening.

Researchers believe PIMS-TS may represent an overreaction of the immune system to the virus, but the exact cause remains unclear. A vital piece of the puzzle is understanding whether the syndrome is caused by a particular strain of coronavirus, or the result of a ‘normal’ coronavirus interacting with particular characteristics in the body.

In their study published in Pediatrics, ICH researchers solve this mystery by showing that there is no ‘mutant’ strain of the virus causing the syndrome.

‘Our study reinforces the likelihood that factors already present in the patient’s body, are responsible for PIMS-TS’ says Project Lead Professor Judith Breuer, virology researcher and consultant at the ICH and Great Ormond Street Hospital (GOSH). ‘It rules out suggestions that some COVID-19 coronavirus strains are more likely to cause PIMS-TS, and further underlines the need for research into host factors to improve our understanding of the causes of this syndrome in young patients.’

Inside the SARS-CoV-2 virus, there is a sequence of genetic information that determines how the virus grows and functions – just like our DNA. The sequence can change over time, gradually creating noticeable differences between different populations of people. Sequencing or ‘reading’ this genetic information in lots of different versions of the virus can reveal how it is changing and spreading.

As part of the COVID-19 Genomics UK Consortium (COG-UK), the ICH sequences viral samples from across London. This work has already helped us understand how the virus reached the UK, and that some strains may be more transmissible than others. Now, it provides useful new information on the viruses causing PIMS-TS.

The ICH team studied samples from 61 children hospitalised with COVID-19 in London between late-March and mid-May 2020, including 26 patients diagnosed with PIMS-TS. They performed genetic analyses to ‘read’ the entire viral genome in five children with PIMS-TS, comparing these with sequences from eight children without the syndrome.

They found no significant differences between the genetic signature of the virus in patients with or without PIMS-TS, suggesting that a ‘PIMS-TS’ strain of coronavirus does not exist.

This provides crucial information for clinicians, particularly over the coming months as we prepare for a potential second wave. Ruling out a mutant viral ‘PIMS-TS’ strain allows clinicians and researchers to focus their efforts on understanding the inherent factors putting certain children at higher risk of developing the syndrome.

‘There may be genetic factors that make some children more vulnerable to developing PIMS-TS,’ says Professor Breuer. ‘There is a lot of work happening worldwide to investigate this. By showing that the virus itself does not carry specific genetic instructions that cause the syndrome, our findings support clinicians to continue with current approaches to management and treatment of PIMS-TS.’