A new study published online by Science links chronic fatigue syndrome to a possibly contagious rodent retrovirus, XMRV or xenotropic murine leukaemia virus-related virus, which has also been implicated in an aggressive form of prostate cancer recently. Related work by the authors also suggests CFS might best be treated with AIDS drugs.
The XMRV virus is a retrovirus, like the HIV virus that causes AIDS. As with all viruses, a retrovirus copies its genetic code into the DNA of its host but uses RNA – a working form of DNA – instead of using DNA to do so.
Known formally as xenotropic murine leukaemia virus-related virus, XMRV has also been found in some prostate tumours and is also known to cause leukaemia and tumours in animals.
Researchers found the virus in the blood of 68 out of 101 chronic fatigue syndrome patients. The same virus showed up in only 8 of 218 healthy people, they reported on Thursday in the journal Science.
Judy Mikovits of the Whittemore Peterson Institute in Nevada and colleagues at the National Cancer Institute and the Cleveland Clinic emphasized that the finding only shows a link between the virus and chronic fatigue syndrome, or CFS, and does not prove that the pathogen causes the disorder.
Much more study would be necessary to show a direct link, but Mikovits said the study offers hope that CFS sufferers might gain relief from a cocktail of drugs designed to fight AIDS, cancer and inflammation.
Previously a number of viruses, including herpes viruses, Enteroviruses, Coxsackie viruses and Epstein-Barr virus have been suggested as triggers for chronic fatigue syndrome. But these have only been found in a small minority of people with the disorder.
However, CFS researchers have long had their eyes on retroviruses. A number of the symptoms, including fatigue and cognitive dysfunction, can occur when the immune system is dealing with a viral infection, and the disease is often preceded by a flu-like illness. Although a number of retroviruses have been hypothesized to play a role in CFS, none has ever been confirmed.
About three years ago Robert Silverman, a biologist at the Cleveland Clinic Foundation in Ohio and a co-author of the new study, discovered a previously unknown retrovirus, XMRV, while searching for a pathogen that might contribute to prostate cancer. The retrovirus was very similar to MLV, a group of viruses that can cause cancer and neurological and immunological diseases in mice. Silverman found XMRV in a subset of prostate tumours, and more recent research found a stronger correlation between XMRV and aggressive prostate tumours.
Mikovits believes the association may be even stronger than the present work indicates. DNA sequencing only picks up active infections, she says, so she wants to study CFS exposure to the virus more broadly. In an unpublished investigation, she and her colleagues analyzed blood cells in about 330 CFS patients and found that more than 95% expressed antibodies to XMRV, whereas about 4% of healthy controls did.
Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome
Vincent C. Lombardi, Francis W. Ruscetti, Jaydip Das Gupta, Max A. Pfost, Kathryn S. Hagen, Daniel L. Peterson, Sandra K. Ruscetti, Rachel K. Bagni, Cari Petrow-Sadowski, Bert Gold, Michael Dean, Robert H. Silverman, Judy A. Mikovits
Science Published Online October 8, 2009, DOI: 10.1126/science.1179052