A mouse virus linked to chronic fatigue syndrome may not be the cause of the disease, according to four studies that cast doubt on the basis of a U.S. move to ban sufferers of the energy-sapping illness from donating blood.
Researchers from the U.S., U.K. and Japan found that previous research linking the virus, XMRV, to chronic fatigue and prostate cancer may have used contaminated specimens and chemicals that led the scientists involved to draw the wrong conclusions. The studies were published yesterday in the journal Retrovirology.
The American Red Cross, the largest U.S. supplier of blood products, said Dec. 3 it would no longer allow donors with chronic fatigue syndrome, based on results of a study published last year that was the first to link the condition to XMRV. The U.S. Food and Drug Administration is considering banning blood donors with the illness.
“Our conclusion is quite simple: XMRV is not the cause of chronic fatigue syndrome,” Greg Towers, who led one of the four new studies at University College London, said in a statement. “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,” Towers said.
The U.K., Australia, Canada and New Zealand have decided to defer blood donations from people with chronic fatigue syndrome, according to the FDA.
XMRV, or xenotropic murine leukemia virus-related virus, is present in mouse DNA and can infect mice and humans. Mouse DNA is “ubiquitous” in laboratory specimens, creating potentially misleading experiment results, according to researchers led by Mark Robinson at Imperial College London, who wrote one of the studies.
XMRV was first identified in 2006 in tissue specimens from men with prostate cancer, according to the U.S. Centers for Disease Control and Prevention. It was linked to chronic fatigue syndrome in October last year by a study in the journal Science that found it in two-thirds of people with the disease. CDC researchers failed to find a viral link to the illness in a separate study published in July.
Chronic fatigue syndrome affects more than 1 million Americans, mainly women, according to the CDC in Atlanta. The illness, marked by exhaustion, joint and muscle pain, lacks a widely accepted cure or approved treatments.
Since the October 2009 study was published, some researchers studying chronic-fatigue patients found genetic material from mouse viruses not including XMRV, raising questions about whether XMRV was really the cause, Robert Smith, a research assistant professor of pathology at the University of Washington in Seattle, said in a commentary accompanying the studies.
In the latest four papers, two found trace elements of mouse DNA in prostate tissue samples and blood from patients with chronic fatigue, based on a more sensitive test than that used in the original research. That suggests the specimens were contaminated with mouse DNA in the laboratory, Smith wrote.
The third study identified viral DNA in a chemical used to conduct experiments, and the fourth found that tests used to detect XMRV can also detect related viruses that only infect mice, suggesting mouse DNA can contaminate human samples.
“It is premature to rule out XMRV or related viruses as factors in prostate cancer or” chronic fatigue syndrome, said Ian Lipkin, a professor of epidemiology at Columbia University who wasn’t involved in the research.
While the latest research highlights the hazards of contamination, rigorous trials are needed to prove or disprove the link between XMRV and the diseases, Lipkin said in an e-mail. The U.S. National Institutes of Health is conducting such a study, he said.