E2 ModerateModerate confidencePEM unclearCross-SectionalPeer-reviewedReviewed
No evidence for xenotropic murine leukemia-related virus infection in Sweden using internally controlled multiepitope suspension array serology.
Blomberg, Jonas, Blomberg, Fredrik, Sjösten, Anna et al. · Clinical and vaccine immunology : CVI · 2012 · DOI
Quick Summary
Researchers tested blood samples from ME/CFS patients and healthy blood donors to see if they had been infected with a mouse virus called XMRV, which had been proposed as a possible cause of ME/CFS. Using a sensitive new testing method that looked for multiple signs of XMRV infection, they found no difference in viral markers between the two groups, suggesting XMRV is not associated with ME/CFS.
Why It Matters
This study addresses a significant controversy in ME/CFS research, helping to clarify whether XMRV—a purported infectious agent—plays a role in disease pathogenesis. The robust serological methodology provides evidence against a major hypothesized viral etiology, allowing the field to redirect research efforts toward other potential causes while also demonstrating a reusable multiplex platform for future retroviral screening.
Observed Findings
- No significant differences in IgG seroreactivity to XMRV env and gag proteins between ME/CFS patients and blood donors
- No differences in antibody responses to 38 gammaretrovirus epitope-derived peptides between the two groups
- Animal control sera (positive and negative) performed as expected, validating assay sensitivity and specificity
- Degenerate peptides covering murine leukemia virus variation did not generate higher background than non-degenerate controls
Inferred Conclusions
- XMRV infection is not associated with ME/CFS in the Swedish population studied
- The multiplex serological suspension array is a valid and practical tool for large-scale retroviral screening with built-in quality control
- Previous findings linking XMRV to ME/CFS were not corroborated by this more comprehensive serological investigation
Remaining Questions
- Could XMRV infection occur in ME/CFS patients from geographic regions other than Sweden?
- Might cell-mediated immune responses (T-cell responses) to XMRV exist in ME/CFS patients despite absent or minimal antibody responses?
- What other infectious agents should be systematically evaluated as potential ME/CFS etiologic factors?
What This Study Does Not Prove
This study does not prove that ME/CFS has no infectious cause—it only rules out XMRV specifically. The lack of XMRV-positive human controls limits the positive predictive value of the assay. Additionally, serological absence does not exclude persistent viral infection in tissues or compartments where antibody responses may be minimal.
Tags
Biomarker:AutoantibodiesBlood Biomarker
Method Flag:Weak Case DefinitionSmall Sample
Metadata
- DOI
- 10.1128/CVI.00391-12
- PMID
- 22787191
- Review status
- Editor reviewed
- Evidence level
- Single-study or moderate support from human research
- Last updated
- 12 April 2026
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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