# Extracellular Vesicle Protein and MiRNA Signatures as Biomarkers for Post-Infectious ME/CFS Patients

## TL;DR

The study explores how proteins and miRNAs in extracellular vesicles from blood can help diagnose and understand ME/CFS, a chronic illness with unclear causes.

## Contribution

The study identifies novel EV protein and miRNA signatures, including hsa-let-7b-5p, as potential biomarkers for ME/CFS diagnosis and patient stratification.

## Key findings

- EVs from ME/CFS patients showed altered cargo proteins like hemoglobin subunit alpha and insulin-like growth factor-binding protein acid labile subunit.
- Post-COVID-19 ME/CFS patients had significantly reduced hsa-let-7b-5p in EVs compared to healthy controls.
- Lower hsa-let-7b-5p levels correlated with worse physical functioning, fatigue, pain, and immune activation in ME/CFS patients.

## Abstract

Post-infectious Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a chronic disease with unresolved pathophysiology and limited diagnostic options. Extracellular vesicles (EVs) carry disease-specific protein and miRNA signatures and may enable improved disease profiling. We aimed to identify novel protein and miRNA markers as potential biomarkers in plasma EVs from female ME/CFS patients, including post-COVID-19 ME/CFS and post-infectious ME/CFS of other origins, compared with healthy controls. EVs were isolated from plasma by size-exclusion chromatography and characterized for number, size, morphology, and surface marker expression. Flow cytometry showed that small EVs strongly expressed tetraspanins, with only minor differences between ME/CFS patients and healthy donors. Proteomic profiling of EVs from ME/CFS patients identified altered cargo proteins, including hemoglobin subunit alpha and insulin-like growth factor-binding protein acid labile subunit compared with healthy controls (n ≤ 10/cohort). Small RNA sequencing followed by qPCR revealed significant downregulation of hsa-let-7b-5p in EVs from post-COVID-19 ME/CFS patients (n = 12) versus healthy controls (n = 15). Reduced hsa-let-7b-5p expression correlated with impaired physical functioning and increased fatigue, pain, and immune activation. These findings indicate that EV cargo differences, particularly hemoglobin subunit alpha and insulin-like growth factor-binding protein acid labile subunit, as well as hsa-let-7b-5p, represent promising candidates for ME/CFS diagnosis and patient stratification.