‘Researchers stand by findings linking XMRV to chronic fatigue syndrome’, Los Angeles Times health blog, 11 May 2011

From the Los Angeles Times, ‘Booster Shots' blog, 11 May 2011. (Story by Trine Tsouderos of the Chicago Tribune).

Researchers who remain convinced that a retrovirus is linked to chronic fatigue syndrome say they have proof their findings are correct, dismissing a recent comprehensive study that found no evidence of the link.

That paper, published last week in the Journal of Virology by a team led by University of Utah researcher Dr. Ila R. Singh, is just the latest in a long line of studies conducted by scientists who have looked for evidence of the retrovirus XMRV in the blood of chronic fatigue syndrome patients but failed to find any.

The scientific community’s consensus is that the original findings, reported in the journal Science in 2009, likely were the result of lab contamination, not a real infection in people.

But researchers from the Whittemore Peterson Institute for Neuro-Immune Disease, which led the team that published that report, say they are confident of their findings.

One reason, they stated in a written response posted online Monday, is that they have isolated XMRV from one chronic fatigue syndrome patient and decoded its genetic sequence. That sequence, they write, is different from the genetic sequences of two known XMRV samples.

Those differences indicate they found something growing — and changing — in a person, not the same lab contaminant over and over again, they say. “Sequence data demonstrates that this virus is clearly distinct,” the researchers wrote in their statement.

But the three sequences — published in a federally maintained genetic database known as GenBank — are nearly identical, several retrovirologists pointed out. The differences among the sequences amount to very few bases among more than 8,000.

“That’s about the amount of difference I would expect to accumulate during one or two tissue culture passages,” wrote Tufts University retrovirologist John Coffin. “Given what we now know about this virus, I don't see how it can be anything but cross contamination of cell cultures.”WPI also stated that many of the patients tested positive for “antibodies to a XMRV … indicating that these patients had an immune response to a XMRV.”

But virologist Vincent Racaniello of Columbia University said that can’t be true. “There is no way they can say that the antibodies are specific for XMRV,” Racaniello said.

In an email, retrovirologist Jonathan Stoye suggested that if the methods described in the original paper don’t hold up, it should be retracted.

“Sooner or later they are going to have to face up to the fact that [their] paper is almost certainly flawed beyond repair,” wrote Stoye, head of the Division of Virology at the UK Medical Research Council's National Institute for Medical Research. “What is more, WPI cannot simply blame others for failing to reproduce their protocols.”

“Rather they must ask themselves whether the protocols they have described, if followed to the letter, can yield the data they have reported,” he wrote. “If not, the original paper should be retracted.”