July 2011

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Study Raises Doubts About Virus and Chronic Fatigue

A virus previously tied to prostate cancer and chronic fatigue syndrome (CFS) is unlikely to be responsible for either, new research shows. The virus, called XMRV, appears to have arisen in the laboratory. The link to human disease was probably due to contamination of samples.

XMRV is a mouse-related virus. It was first found in samples from a human prostate tumor in 2006. Then in 2009, a study found XMRV in the blood of nearly 70% of people with CFS. However, several research teams questioned the results. When they conducted their own tests, they couldn’t detect XMRV in samples from people with prostate cancer or CFS.

To take a closer look, a team of scientists led by NIH investigators looked for the origins of XMRV in human samples. Cancer researchers often study the biology of human tumors by growing them on mouse tissues in the laboratory. The NIH team suspected that XMRV might have originally come from the mice and then contaminated the human samples.

A series of experiments confirmed that the original samples of human prostate tumors didn’t contain XMRV. But the virus was found in tumor samples after they had been grown on mice and then regrown to make more tumor cells. XMRV seems to have infected the human cells while they were in mice.

A related study could find no link between XMRV and CFS, even in the same patients from the 2009 study. The scientists concluded that the earlier results likely stemmed from laboratory contamination.

“Taken together, these results essentially close the door on XMRV as a cause of human disease,” says study co-author Dr. John Coffin of Tufts University School of Medicine. Some evidence still suggests that these diseases may arise from viruses, but not from XMRV.