Xenotropic murine leukemia virus-related virus in monozygotic twins discordant for chronic fatigue syndrome.
Jerome, Keith R, Diem, Kurt, Huang, Meei-Li et al. · Diagnostic microbiology and infectious disease · 2011 · DOI
Quick Summary
Researchers tested whether a virus called XMRV was present in people with ME/CFS by comparing identical twins where one had the illness and one didn't. They looked for the virus in blood samples using multiple sensitive tests. They found no evidence of XMRV in any of the people with ME/CFS, suggesting this virus is not likely a cause of the disease.
Why It Matters
Earlier reports suggesting XMRV involvement in ME/CFS raised hope that antiretroviral treatments might help patients. This study's negative findings cast doubt on that hypothesis and demonstrate the importance of rigorous validation before pursuing treatment implications based on initial viral association reports.
Observed Findings
Zero PBMC samples positive for XMRV DNA across three separate PCR assays in both CFS-affected twins and unaffected co-twins
One plasma sample from an unaffected co-twin showed transient XMRV RNA positivity by RT-PCR
Serum from the same day as the positive plasma sample was negative for XMRV RNA
Follow-up plasma sample obtained 2 days after the initially positive specimen tested negative
Inferred Conclusions
XMRV is not associated with ME/CFS in this twin cohort
The transient plasma detection in an unaffected individual likely represents a false positive or environmental contamination rather than true viral infection
The validated assays successfully detected XMRV but found no meaningful prevalence in the study population
Remaining Questions
Why did the single plasma sample show transient positivity if not true infection, and could this represent contamination?
Have other tissue types or cell populations beyond PBMCs been systematically tested for XMRV in ME/CFS patients?
Could XMRV involvement be limited to specific ME/CFS subtypes not captured in this twin cohort?
What This Study Does Not Prove
This study does not exclude other viral pathogens from potential involvement in ME/CFS, nor does it rule out XMRV in other patient populations or tissue types not tested. A single negative study cannot definitively rule out viral associations, and subsequent research has since questioned the validity of XMRV detection methods themselves.