Steifman et al. (2026)
- Authors: Carly B. Steifman, Belen Alvarez-Carcamo, S. Verma, Michael B. VanElzakker, Lael M. Yonker
- Institutes: Mass General for Children, Boston, MA, USA, Harvard Medical School, Boston, MA, USA
- Publisher: Pediatric Research
- Link: DOI
Summary
This research identifies a clear biological mechanism for the cardiovascular symptoms often dismissed in younger Long COVID patients. By linking the SARS-CoV-2 Spike protein to neutrophil-driven vascular damage and microclots, it provides measurable biomarkers that could lead to targeted anti-inflammatory or anti-clotting therapies. It shifts the clinical focus from subjective symptoms to objective endovascular pathology in the pediatric population.
What was researched?
This study investigated the biological mechanisms behind debilitating endovascular and cardiovascular symptoms in children and young adults with Long COVID. Researchers specifically examined the relationship between fibrin amyloid microclots, neutrophil activation, and the presence of the SARS-CoV-2 Spike protein.
Why was it researched?
Vascular symptoms are common and severe in Long COVID, yet the underlying causes remain poorly understood, especially in pediatric and young adult populations. Identifying specific biomarkers and mechanisms is crucial for developing objective diagnostics and effective treatments for these patients.
How was it researched?
The study enrolled 84 participants aged 25 and younger from the U.S. and Canada, including 61 with Long COVID and 23 healthy controls. Researchers analyzed blood samples for microclots, endovascular cytokines, and cell-free DNA as a marker for neutrophil extracellular traps (NETs). They also performed laboratory assays to observe how Spike protein-immune complexes interact with immune cells and blood vessel linings.
What has been found?
Long COVID patients showed significantly higher levels of microclots and markers of vascular remodeling, such as FGF-2, compared to healthy controls. The study found elevated cell-free DNA, indicating increased ‘NETosis,’ a process where white blood cells release traps that can damage vessel linings. This neutrophil activation was directly triggered by Spike-containing immune complexes and positively correlated with microclot components like serum amyloid A. Conversely, certain markers involved in normal immune cell movement were found to be reduced.
Discussion
The findings suggest that persistent viral proteins may be driving a continuous cycle of immune-driven vascular injury. A limitation of the study is the relatively small sample size, although the use of age-matched pediatric controls provides high-quality comparative data. The results highlight NETosis as a primary driver of the endovascular pathology seen in these patients.
Conclusion & Future Work
The researchers conclude that intravascular neutrophil activation and microclot formation are central features of Long COVID in young people. These results warrant further clinical evaluation of therapies targeting these specific pathways to alleviate vascular symptoms.