New research shows virus previously linked to chronic fatigue syndrome is a lab contaminant

A virus previously thought to be associated with chronic fatigue syndrome is not the cause of the disease, a detailed study has shown. The research shows that cell samples used in previous research were contaminated with the virus identified as XMRV and that XMRV is present in the mouse genome.

XMRV was first linked to chronic fatigue syndrome — also known as myalgic encephalomyelitis (ME) — in a study published in October 2009, where blood samples from chronic fatigue syndrome patients were found to have traces of the virus. XMRV had also been identified previously in samples from certain prostate cancer patients.

The new study, published in Retrovirology, identifies the source of XMRV in chronic fatigue syndrome samples as being cells or mouse DNA rather than infection by XMRV. The research does not rule out a virus cause of chronic fatigue syndrome – it is simply not this virus.

The research team developed improved methods to detect XMRV against the genetic noise of other sequences and make recommendations for future study of virus causes of human disease.

“Our conclusion is quite simple: XMRV is not the cause of chronic fatigue syndrome,” says Professor Greg Towers, a Wellcome Trust Senior Research Fellow at University College London (UCL). “All our evidence shows that the sequences from the virus genome in cell culture have contaminated human chronic fatigue syndrome and prostate cancer samples.

“It is vital to understand that we are not saying chronic fatigue syndrome does not have a virus cause — we cannot answer that yet — but we know it is not this virus causing it.”

The team, from University College London, Wellcome Trust Sanger Institute and University of Oxford, showed clearly that the experimental design of previous studies would pick up sequences that resembled XMRV; however, in this improved study, they could prove that the signal was from contamination by a laboratory cell line or mouse DNA. The sequences from the contaminated cell line and chronic fatigue patient samples were extremely similar, contrary to the pattern of evolution expected during the infectious spread of a virus in a human population.

They also showed that the existing methods would indicate that one in fifty human cell lines they examined were infected with XMRV-related viruses: they showed that contamination of human tumour cells with XMRV-related viruses is common and that a principal prostate cancer line used is contaminated.

“When we compare viral genomes, we see signs of their history, of how far they have travelled in space or time,” says Dr Stéphane Hué, Post Doctoral Researcher at UCL. “We would expect the samples from patients from around the world, collected at different times, to be more diverse than the samples from within a cell line in a lab, where they are grown under standard conditions. During infection and transmission in people, our immune system would push XMRV into new genetic variants.

“Viral infection is a battle between the virus and the host and XMRV does not have the scars of a virus that transmits between people.”

Together the results demonstrate that XMRV does not cause chronic fatigue syndrome or prostate cancer in these cases. The team’s methods suggest ways to ensure that virus contamination does not confound the search for a cause of disease in future work.

The authors propose that more rigorous methods are used to prevent contamination of cell and DNA samples. They also suggest that consistent and considered standards are needed for identifying viruses and other organisms as cause of a disease.

“Increasingly, we are using DNA-based methods to accelerate our understanding of the role of pathogens in disease,” explains Professor Paul Kellam, Virus Genomics group leader from the Wellcome Trust Sanger Institute. “These will drive our understanding of infection, but we must ensure that we close the circle from identification to association and then causation.

The strongest lesson is that we must fully use robust guidelines and discriminatory methods to ascribe a cause to a disease.”

The research paper can be found online at

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7 thoughts on “New research shows virus previously linked to chronic fatigue syndrome is a lab contaminant”

  1. Eric Klein, Cleveland Clinic: ” We have reported XMRV integration in fresh frozen prostate tissue taken directly from patients at radical prostatectomy that has never been put in tissue culture and believe this is solid evidence of authentic human infection . See Dong et al PNAS 2007 and Kim et al. J Virol 2008″

  2. funinco at 6:03 PM December 21, 2010

    Here is a quote from Europe’s most noted CFS doctor, Prof. Kenny De Meirleir

    “The contamination by mouse material was excluded in our study, that of Lo and that of Lombardi et al. We are not using PCR as a basis of the test but human prostate cancer cells that do not express RNase L so the virus from patient’s blood can grow in it. We also sequence the virus and I can assure you it is not mouse material. Governments and insurance companies are horrified by the idea that there is a new retrovirus out there that has infected 10 times more people than HIV up to date. My preliminary data show that the virus does not grow in culture anymore after Nexavir + GcMAF although the procedure was identical to the pretreatment culture. In the next months more will come from our side. A study with healthy blood donors, ME patients who got ill immediately after blood transfusion and ME patients who gave blood after they got ill will be published in the first half of 2011. What these 5 are doing to the patients is a crime against humanity. — Kenny De Meirleir”

  3. Here is a quote from the bigwig NIH viral-hunter, Ian Lipkin:

    “These papers emphasize the pitfalls of molecular assays and raise concerns. Nonetheless, it is premature to rule out XMRV or related viruses as factors in prostate cancer or CFS. Links have also been made based on serology and the presence of viral proteins as well as of viral sequences. Thus, we still need appropriately powered, rigorous blinded studies of well characterized patients and controls. One such study is underway under the auspices of the National Institutes Health.

  4. It is difficult to describe the pain one feels but findrxonline article I think is practical.

    Chronic pain is constant or recurrent and is caused by a long-term condition (arthritis) or to progressive illness (cancer). Chronic pain lasts for months – and it may last a lifetime. Chronic pain takes a psychological as well as a physical toll. It can lead to anxiety, anger, depression, and insomnia. Chronic pain sufferers may find it difficult or impossible to work hard to do the things they and eleven enjoyed. Chronic pain can even disrupt a person’s relationships with family and friends.
    What do you think you about chronic pain…?

  5. Nice title – way to overstate the findings. Why not “New research shows virus previously linked to prostate cancer is a lab contaminant.”

    I suggest you read the WSJ article and John Coffin’s comment (he co-authored two of the articles):

    WSJ – But John M. Coffin, a retrovirologist and a co-author of another of today’s Retrovirology papers, told Health Blog that while his group’s study demonstrated that mouse DNA is everywhere in labs, none of today’s published papers ”definitively show that any prior study is wrong.”


    Dr. Coffin said the debate over XMRV will continue. ”This is not the end of XMRV,” Coffin said, ”but it is a warning we have to be very, very careful.”

    Perhaps a better title for your article would be “Blogger overstates findings as indicating that pathogen is not linked to CFS – patients yawn!”

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