In summary, the analysis of specific immune cell-derived EV subsets may provide a method to monitor disability accumulation, disease activity, and axonal injury in MS, while also providing insights into the pathophysiology and cellular/molecular mechanisms that influence progression.

Given the limitations associated with implementing and acquiring novel and emerging imaging biomarkers in routine clinical practice, the discovery of biofluid biomarkers may offer a more simple and cost-effective measure that would improve accessibility, standardization, and patient care. Extracellular vesicles (EVs) are nanoparticles secreted from cells under both homeostatic and pathological states, and have been recently investigated as biomarkers in MS. The objectives of this study were to longitudinally measure levels of specific immune cell-derived EVs in MS and provide evidence that EV sub-populations may serve as biomarkers of disease activity, axonal injury, and/or clinical disability.

Our results demonstrate that the rate of clinical disability in MS negatively correlates with changes in circulating CD3+ EVs within the plasma. Additionally, numbers of CD4+ EVs decrease in individuals with increasing pNfL levels overtime whereby the magnitude of the pNfL increase negatively correlates with changes in plasma CD4+ and CD8+ EVs. Finally, when applying NEDA-3 criteria to define active versus stable disease, individuals with active disease had significantly elevated CD4+ and CD8+ EVs compared to stable disease.