Le Monde XMRV article

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Le Monde article (September 3rd) on XMRV:

http://tinyurl.com/LeMondeAlter

Sometimes called myalgic encephalomyelitis, is chronic fatigue syndrome caused by a virus?

Work published at the end of August in Proceedings of the National Academy of Sciences (PNAS) suggests a close link between this enigmatic disease, for a long time considered psychosomatic, and retroviruses of the MLV (Murine Leukemia Virus) family - responsible in particular for leukaemias and neuropathologies in mice.

Led by Harvey Alter (National Institute of Health), this new study reinforces earlier work, published in autumn 2009, suggesting such an association. This very disabling disease, which combines a deep and lasting fatigue with muscular or joint pains and cognitive problems (confusion, loss of memory, etc), affects approximately a million people in the United States.

The question of a possible viral cause is not yet settled. "For now, everyone agrees that causality between MLV and this very disabling syndrome is not established" said Marc Sitbon, specialist in oncogenic retroviruses and Director of Research at the Institute of Molecular Genetics of Montpellier (University of Montpellier / CNRS).

In October 2009, American researchers, partially financed by a patient-organization, had found genetic sequences of XMRV (Xenotropic MLV-Related Virus) in 67% of a sample with "chronic fatigue". The virus was only found in a small proportion of healthy subjects.

Conflicting results:

This work has raised considerable interest. "Four European teams have sought to establish this link and none has succeeded," said Sitbon. Alter (a big name in virology) and his team achieved this result with extensive experimental precautions [to prevent contamination] that were praised by the scientific community. How to interpret these contradictory results? "I do not think this is due to a difference in the disease-definition on both sides of the Atlantic", argues Sitbon. "This may be due to technical problems during testing, or the fact that the virus has reached certain patient cohorts and not others in ways that remain to be determined."

One way to decide, says the researcher, is to essentially show that the viral gene sequences detected are indeed incorporated into the patient's DNA - a characteristic of retroviruses. Even, why not conduct a clinical trial of individuals with a particularly debilitating form of the disease, testing the effectiveness of antiretrovirals. Two recent studies suggest that some drugs used against HIV may be effective against XMRV.