Detection of murine leukemia virus or mouse DNA in commercial RT-PCR reagents and human DNAs.
Zheng, HaoQiang, Jia, Hongwei, Shankar, Anupama et al. · PloS one · 2011 · DOI
Quick Summary
Scientists tested commercial laboratory reagents and DNA samples commonly used in medical research and found that many contained mouse virus sequences (MLV). These contaminations appear to come from the manufacturing process and could produce false-positive test results if not properly identified. This discovery is important because earlier ME/CFS studies reporting MLV detection may have been affected by these contaminated supplies rather than finding a real virus in patients.
Why It Matters
This study provides crucial methodological context for interpreting previous ME/CFS studies that reported XMRV detection, many of which showed conflicting results. By identifying widespread contamination in commercial reagents and DNA samples, it offers a plausible explanation for some positive findings and emphasizes the importance of rigorous quality control in viral detection research, directly affecting how earlier ME/CFS studies should be evaluated.
Observed Findings
Reverse transcriptase enzymes from six commercial suppliers contained MLV polymerase DNA sequences but not gag or mouse DNA sequences
Commercial human DNA samples from leukocytes, brain tissues, and cell lines contained mouse DNA and MLV sequences
Pyhlogenetic analysis showed contaminating MLV sequences were highly related to Moloney MLV
Platinum Taq polymerase was confirmed as a source of contamination (mouse DNA)
Patterns suggested contamination originated from RT-containing plasmids used in enzyme manufacturing
Inferred Conclusions
Commercial PCR reagents and DNA specimens are significant, previously unrecognized sources of MLV contamination
Residual plasmid contamination during manufacturing of recombinant RT enzymes introduced MLV sequences into widely distributed reagents
False-positive MLV PCR results in prior studies may have resulted from contaminated commercial supplies rather than true viral detection
Systematic pre-screening and validation of commercial reagents and specimens is essential for studies investigating MLV associations with human diseases
Remaining Questions
How many historical ME/CFS studies reporting XMRV were actually affected by these specific contamination sources?
What This Study Does Not Prove
This study does not prove that all previous XMRV findings in ME/CFS patients were false positives, nor does it definitively establish whether XMRV is or is not associated with ME/CFS. It identifies one potential source of contamination but cannot retrospectively determine which specific prior studies were affected by contaminated reagents.
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 →