New Doubts on XMRV as Chronic Fatigue Syndrome Cause
Studies Suggest Contamination of Lab Samples May Have Influenced Earlier Research
Study Researchers Respond
In a written response, study researcher Judy A. Mikovits, PhD, director of Research at the Whittemore Peterson Institute in Reno, Nev., defended her 2009 paper. She called the journal's expression of concern "premature" and said its publication "would have a disastrous impact on the future of this field of science."
A government-sponsored trial is under way to see if the XMRV virus can be detected in patients with CFS, and researchers pledged that it would go on, even in light of the negative findings of the new studies.
Failure to Replicate Findings
Since the publication of the original paper in 2009, at least 11 groups have tried, and failed, to find XMRV in chronic fatigue patients, while one group found evidence of related viruses called murine leukemia viruses in about 87% CFS patients compared with only about 7% of healthy patients.
Study researcher Jay A. Levy, MD, head of the Laboratory for Tumor and AIDS Virus Research at the University of California at San Francisco, who was one of the first scientists to identify XMRV, says he became suspicious when he noticed how similar the virus appeared to be between samples.
"They were so identical that it did not make sense," Levy says. "When the virus replicates it always changes."
Additionally, he says, studies have shown that XMRV is rapidly deactivated by the body's defenses and doesn't survive for long in blood.
So he approached the same medical practice that tested patients for the original 2009 paper and retested 43 patients who had been told they tested positive for XMRV and 18 more that had a diagnosis of CFS.
Using multiple ways to look for traces of the retrovirus, they found no evidence of its presence in any of the patients they tested.
"We were able to cover everything in the Lombardi paper, and even more so," Levy says. "The evidence does definitely look like contamination."
Levy, who has also studied chronic fatigue syndrome, says he believes it is an autoimmune disease. He thinks something that sets off the immune system in patients with CFS, and that it fails to quiet down after the initial insult, leading to long-term illness.
He says patients with CFS shouldn't be discouraged by the latest findings, which he says amounted to a distraction in the search for a cure.
"Patients have to realize that this doesn't mean, yet again, they aren't going to get any attention. If anything, it puts attention on this syndrome and says, 'Find the real reason. Find the real solution,'" he says.