HERV activation segregates ME/CFS from fibromyalgia while defining a novel nosologic entity

Area of Science:

• Immunology
• Genetics
• Chronic Illness Research

Background:

• Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM) are chronic illnesses with unknown etiology and frequent co-occurrence.
• Human endogenous retrovirus (HERV) activation has been observed in ME/CFS and FM, but its diagnostic and prognostic value remains unexplored.

Purpose of the Study:

• To investigate the diagnostic potential of HERV expression profiles in ME/CFS and FM.
• To explore the relationship between HERV expression, immune cell profiles, and symptom severity in these conditions.

Main Methods:

• Utilized HERV-V3 high-density microarrays to analyze HERV and immune gene expression in peripheral blood mononuclear cells.
• Included female patients with ME/CFS, FM, co-diagnosed ME/CFS-FM, and healthy controls (n=43).
• Applied hierarchical clustering to HERV expression profiles for participant classification.

Main Results:

• HERV expression profiles accurately distinguished between ME/CFS, FM, co-diagnosed, and healthy groups.
• Identified unique HERV-immune gene modules for each group, noting decreased γδ T cells and increased CD4 memory T cells in ME/CFS correlating with symptom severity.
• Observed HERV activation linked to epigenetic silencer binding sites in ME/CFS, suggesting a mechanistic basis.

Conclusions:

• HERV expression profiles serve as potent biomarkers for differentiating ME/CFS and FM.
• Co-diagnosed patients represent a distinct nosological entity with minimal epigenetic impact from HERVs.
• Findings offer insights into diagnosis and potential therapeutic strategies for these prevalent chronic illnesses.