An earlier study published in 2009 had claimed that a mouse virus was the cause of chronic fatigue syndrome. New evidence suggests that this assumption is wrong. According to latest evidence the earlier study findings were likely based on contaminated lab samples, US researchers said Tuesday.
Jay Levy of the University of California, San Francisco, senior author of the study to be published this week in the journal Science said, “There is no evidence of this mouse virus in human blood.” The university said in a statement that the mouse virus XMRV that was picked up in samples from chronic fatigue patients probably got there because “chemical reagents and cell lines used in the laboratory where it was identified were contaminated with the virus.”
It was claimed that the 2009 study was a breakthrough for the estimated one to four million Americans who suffer from the elusive but debilitating illness, and led to many being treated with antiretroviral drugs used against HIV/AIDS. The disease can last for years and cause memory loss, muscle pain, extreme tiredness and possibly insomnia. The 2009 study was conducted by researchers in Nevada and Maryland who found xenotropic murine leukemia virus-related virus (XMRV) in about two-thirds of blood samples taken from 101 patients with chronic fatigue syndrome.
Co-author Konstance Knox of the Wisconsin Virus Research Group in Milwaukee, Wisconsin said, “Individuals with Chronic Fatigue Syndrome need to know that taking antiretroviral therapies will not benefit them, and may do them serious harm… Physicians should not be prescribing antiviral compounds used in the treatment of HIV/AIDS to patients on the basis of a Chronic Fatigue Syndrome diagnosis or a XMRV test result.”
According to Levy, a prominent HIV/AIDS researcher, he was contacted by the original team to try to replicate its findings by examining blood samples from other chronic fatigue patients. Using similar procedures to examine the blood of 61 patients, “Levy and colleagues found no evidence of XMRV or any other mouse-related virus,” UCSF said. They also determined that it was highly unlikely that humans could become infected with the mouse virus in the first place, because “human serum quickly kills it.”
“With this extensive study, we could not confirm any of the results of the earlier papers,” Levy said. “Taken together, these results essentially close the door on XMRV as a cause of human disease,” said John Coffin of Tufts University School of Medicine in Boston, who worked on one of the studies with Vinay Pathak of the National Cancer Institute.
Pathak and colleagues studied human prostate cancer cells thought to contain XMRV, as well as tumors from these cells after they had been made to grow in mice, a common way to study new treatments that might not be safe to test in people. A careful study of these showed that the while the initial prostate tumors grown in mice contained no XMRV, later tumors derived from this tissue did - showing that the virus was not present in the original human tumor, as previously thought. Instead, the virus appears to have infected tumor cells while they were in mice.
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