A virus that was believed to be the cause of chronic fatigue syndrome, also known as ME, has turned out to be a laboratory contamination that could not have caused an infection in humans, scientists said yesterday.
The discovery will embarrass the American scientists who said in 2009 that they had found convincing evidence to link the virus, called XMRV, with chronic fatigue syndrome, the debilitating condition that affects about three in every 1,000 people.
British researchers, led by Professor Greg Towers of University College London, believe that the DNA techniques used in the US research were so sensitive that they inadvertently picked up laboratory contaminants that had been in contact with XMRV, which normally infects mice.
"Our conclusion is quite simple: XMRV is not the cause of chronic fatigue syndrome. Our evidence shows that the sequences from the virus genome in cell culture have contaminated human chronic fatigue syndrome samples," Professor Towers said.
"It is vital to understand that we are not saying chronic fatigue syndrome does not have a virus cause – we cannot answer that yet – but we know it is not this virus causing it."
The study, involving scientists from the Wellcome Trust Sanger Institute in Cambridge and the University of Oxford and published in the journal Retrovirology, showed that the "virus" detected by the American researchers, led by Judy Mikovits of the Whittemore Peterson Institute in Reno, Nevada, was actually a contamination probably arising from growing laboratory reagents in mouse cells infected with the XMRV virus.
The researchers also showed that as many as one in 50 "cell lines" used by scientists in laboratory experiments are infected with XMRV, which significantly increases the prospect of inadvertent contamination of samples taken from patients with chronic fatigue syndrome.
In addition, the scientists found that the DNA sequence of XMRV found within the samples indicated that it was not an actively replicating virus, but one that was being passed on passively, further supporting the idea that it is a laboratory contamination rather than a genuine infection.