Phylogenetic analysis of murine leukemia virus sequences from longitudinally sampled chronic fatigue syndrome patients suggests PCR contamination rather than viral evolution.
Katzourakis, Aris, Hué, Stéphane, Kellam, Paul et al. · Journal of virology · 2011 · DOI
Quick Summary
This study examined whether a virus called XMRV, found in some ME/CFS patients' samples over 15 years apart, could have naturally evolved within patients' bodies. Using genetic analysis, the researchers found that the virus sequences were actually different types of mouse viruses, not the same virus changing over time. This suggests the virus detections were likely due to laboratory contamination rather than evidence of an actual persistent infection.
Why It Matters
This study addresses a critical concern in ME/CFS research regarding the validity of XMRV findings, which generated significant attention and debate in the field. By providing rigorous evidence against true viral persistence and evolution, it clarifies that previous XMRV detections in CFS samples were contamination artifacts, helping redirect research efforts toward more reliable etiological investigations. Understanding what did not cause ME/CFS is as important as identifying what did.
Sequences from first and second time points represented distinct endogenous murine retroviruses rather than variants of the same virus.
The genetic relationships were consistent with laboratory contamination from mouse cell lines rather than human viral infection.
No evidence of XMRV persistence or adaptation over the 15-year sampling interval.
Inferred Conclusions
Previous XMRV detections in longitudinal CFS samples resulted from PCR contamination rather than persistent viral infection.
The 22Rv1 prostate cancer cell line likely served as the contamination source in earlier studies.
XMRV should not be considered a validated etiological agent in ME/CFS based on available molecular evidence.
Remaining Questions
What was the original source of XMRV-like sequences in initial CFS patient samples that appeared to be amplified?
How should laboratories modify their protocols to prevent similar contamination events in future ME/CFS virology research?
What alternative viral or infectious agents should be investigated in ME/CFS given that XMRV has been ruled out as a persistent pathogen?
What This Study Does Not Prove
This study does not prove that no virus is involved in ME/CFS, only that XMRV specifically is not a persistent, evolving infection in these patients. The findings refute the longitudinal XMRV persistence hypothesis but do not address whether other viruses might contribute to ME/CFS pathogenesis. The study also does not explain why initial XMRV amplifications occurred or what role viral contamination in research samples played in prior conflicting results.