By Julie Steenhuysen
CHICAGO (Reuters) - Scientists have retracted part of a 2009 study from the journal Science linking chronic fatigue syndrome with a mouse virus as evidence continues to mount against the virus as a cause of the mysterious disease.
In addition to the partial retraction, Science published on Thursday new research that cast doubt on the theory. A U.S.-backed study found no trace of the XMRV virus, and a related mouse virus, in blood samples taken from healthy people and those with chronic fatigue syndrome.
The disease causes muscle pain, memory loss and overwhelming fatigue. While the XMRV research had offered some hope of identifying its cause, and therefore a treatment, scientists say the link was likely the result of contaminated lab samples.
Initial research from 2009 claimed to have found XMRV in the blood of two-thirds of patients with chronic fatigue syndrome.
But last May, Science ran two reports refuting the 2009 study along with an "editorial expression of concern" and said that the validity of the original chronic fatigue study by research teams in Nevada and Maryland "is now in question.
One of those studies by the National Cancer Institute suggested the finding was the cause of contaminated lab samples. That followed a study done by a team at University College London, the Wellcome Trust Sanger Institute and Oxford University that said cell samples from patients in earlier studies were likely contaminated.
Those concerns appear to have borne out with at least one method of looking for the virus.
Dr. Robert Silverman and Jaydip Das Gupta of the Cleveland Clinic, who were co-authors on the original 2009 paper in Science, double-checked their experiments and found some of the samples from chronic fatigue patients were contaminated with a laboratory form of XMRV genetic material that could not have been present in people.
The team has retracted tables and figures from the study that were based on the contaminated data.
Silverman was not available for comment, but an e-mailed statement from the Cleveland Clinic said the authors no longer believe XMRV plays a role in chronic fatigue syndrome.
According to Science, the study's main authors still believe other data in the paper support their original conclusions. The journal said it stands by its May "editorial expression of concern," and plans to discuss the next steps in light of the new findings.
NO THREAT TO BLOOD SUPPLY
Reports that XMRV and a related mouse virus known as P-MLVs were circulating in the blood of humans had raised worries over the safety of the blood supply.
That prompted scientists at the U.S. Department of Health and Human Services to conduct tests to see if they could detect XMRV or P-MLVs in blood samples taken from healthy people and 14 patients with chronic fatigue syndrome who had previously tested positive for XMRV or P-MLV. They also included a sample from a person who had XMRV but did not have chronic fatigue syndrome.
The samples were blinded and sent to nine different labs including those at the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration as well as those from Abbott Laboratories Inc, GenProbe Inc, and the Whittemore Peterson Institute in Reno, Nevada, the lab run by one of the original authors of the 2009 XMRV study.
Two labs, which previously had reported the link between XMRV and chronic fatigue syndrome, found XMRV in some samples. But these labs reported them in samples from healthy donors and from chronic fatigue patients not infected with XMRV.
Dr. Simone Glynn of the National Heart Lung and Blood Institute, which led the effort, said these were likely false positive results.
"I think these data are very reassuring," Glynn said in a telephone interview.
In June 2010 the nonprofit U.S. blood banking association known as AABB recommended that collection centers discourage people with chronic fatigue syndrome from donating blood.
"We do not think blood donor screening is warranted at this time for these viruses," Glynn said.
Chronic fatigue syndrome strikes an estimated 1 million to 4 million Americans. There is no cure. Patients are treated with drugs to address their symptoms including antidepressants and anti-anxiety medications.
(Editing by Michele Gershberg and Xavier Briand)