Contrary to previous findings, no link appears to exist between chronic fatigue syndrome and xenotropic murine leukemia virus-related virus or polytropic murine leukemia virus, according to a study.
Previous reports that patients with chronic fatigue syndrome carried these two viruses were wrong, according to the new study, and there remains a lack of evidence for an infectious cause behind chronic fatigue syndrome.
“The bottom line is we found no evidence of infection with XMRV and pMLV,” Columbia Universitys Ian Lipkin, MD, a study coauthor, said in a news release. “These results refute any correlation between these agents and disease.”
Chronic fatigue syndrome, also known as myalgic encephalomyelitis, is a disabling condition that causes persistent and unexplained fatigue and a host of associated problems that may include muscle weakness, pain, impaired memory and disordered sleep. Medical treatment for CFS/ME costs as much as $7 billion a year in the U.S.
The possible causes of CFS/ME have been argued and researched for years with no success. Results from separate studies in 2009 and 2010 that reported finding retroviruses in the blood of patients with CFS/ME created a sensation among patients and in the medical community and offered hope that a tractable cause for this disease had been found. Since then, other investigators have been unable to replicate the results of those studies, casting doubt on the idea that XMRV and pMLV could be behind CFS/ME.
For the latest study, researchers recruited 147 patients with CFS/ME and 146 people without the syndrome. The researchers tested blood drawn from these subjects for the presence of genes specific to the viruses XMRV and pMLV, much in the way the earlier studies had done. But in this study, the researchers said, they took extra care to eliminate contamination in the enzyme mixtures and chemicals used for testing, which may have been the source of viruses and genes detected in the earlier studies.
XMRV and pMLV commonly are found in mice, the researchers said, but there never has been a confirmed case of human infection with these viruses
The authors of the new study included many of the authors of the original papers that reported finding XMRV and pMLV in the blood of CFS/ME patients. Research on the causes of CFS/ME will continue, Lipkin said. “The controversy brought a new focus that will drive efforts to understand CFS/ME and lead to improvements in diagnosis, prevention and treatment of this syndrome.”
The study appeared Sept. 18 in mBio, the online open-access journal of the American Society for Microbiology. The study abstract and links to the full study are available at http://mbio.asm.org/content/3/5/e00266-12.