HERV activation segregates ME/CFS from fibromyalgia while defining a novel nosologic entity.
Giménez-Orenga, Karen, Martín-Martínez, Eva, Nathanson, Lubov et al. · eLife · 2025 · DOI
Quick Summary
This study looked at special genetic materials called human endogenous retroviruses (HERVs) in the blood cells of women with ME/CFS, fibromyalgia, both conditions, or neither. The researchers found that the pattern of which HERVs were active could perfectly distinguish between these four groups—suggesting this could become a reliable blood test to diagnose these conditions. The study also found that ME/CFS patients had specific changes in immune cells that matched how severe their symptoms were.
Why It Matters
ME/CFS lacks objective diagnostic tests, making diagnosis difficult and causing patients to wait years for recognition. This research provides evidence that HERV expression patterns could become a biomarker for diagnosis and may reveal important differences between ME/CFS alone versus co-occurring with fibromyalgia. Understanding the immune changes in ME/CFS could eventually lead to better treatments targeted to the actual biological causes of the disease.
Observed Findings
HERV expression profiles achieved perfect hierarchical clustering classification into four groups: ME/CFS, fibromyalgia, co-diagnosed, and healthy controls.
ME/CFS patients showed decreased γδ T cells and increased plasma and resting CD4 memory T cells, with these changes correlating with symptom severity.
Transcription factor binding sites for SETDB1 and TRIM28 (known HERV epigenetic silencers) were enriched in ME/CFS samples.
Co-diagnosed patients displayed minimal HERV perturbation compared to single-diagnosis groups.
Differentially expressed HERV-immune gene modules were unique for each of the four study groups.
Inferred Conclusions
HERV expression profiles have substantial potential as a biomarker to differentiate ME/CFS, fibromyalgia, and co-diagnosed conditions.
Specific immune cell alterations in ME/CFS correlate with symptom severity, suggesting immune dysfunction as a key disease mechanism.
Co-diagnosed ME/CFS and fibromyalgia represents a distinct nosologic entity with minimal epigenetic disruption, requiring different diagnostic and treatment approaches.
Remaining Questions
Can HERV expression profiles predict diagnosis in larger, ethnically diverse populations and in males with ME/CFS?
What This Study Does Not Prove
This study does not prove that HERV activation causes ME/CFS—it only shows they occur together. The small sample size and cross-sectional design cannot establish whether HERV changes happen before symptoms develop or result from them. The findings need validation in larger, independent patient populations before HERV testing could be used clinically in medical practice.