XMRV -Raising the Issue of Contamination

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* December 20, 2010, 5:24 PM ET

XMRV: Raising the

Issue of Contamination

By Amy Dockser Marcus

Four papers published today in the journal

Retrovirology - and a fifth one commenting on the

papers - demonstrated how easy it is for mouse

contamination to skew lab experiments involving the

virus XMRV.

But they are unlikely to resolve the debate over

whether XMRV is linked to diseases like chronic

fatigue syndrome or prostate cancer, especially

since the authors of the papers disagree on the

interpretation of their data.

XMRV has been the topic of much debate since a

paper was published last year in Science, linking the

virus to chronic fatigue syndrome.

The virus was also found in smaller numbers of

healthy controls, raising the possibility that the

blood supply might be infected.

XMRV had previously been linked to prostate cancer.

But some other groups have not been able to find

XMRV in either CFS or prostate cancer patients or in

healthy people.

Greg J. Towers from University College London, a

senior author of one of the papers, told the Health

Blog that his group's findings indicate that " XMRV is

not a human pathogen. "

Tests used to detect XMRV are also able to detect

mouse DNA, and even if a tiny bit of mouse DNA

gets in a lab sample, the test can be positive even if

the patient is not, he explained.

He added that he was not intending to criticize the

work of other scientists. " They published their

observations in good faith and we have simply

reexamined their findings and made new

observations and come to a more likely conclusion. "

But M. Coffin, a retrovirologist and a co-author

of two of today's Retrovirology papers, told Health

Blog that while his groups' studies demonstrated

that mouse DNA is everywhere in labs, none of

today's published papers " definitively show that any

prior study is wrong. "

A. , a research assistant professor at

University of Washington in Seattle who wrote a

commentary in Retrovirology summarizing the

studies, told Health Blog that the possibility of

contamination means that future studies must be

done very carefully before conclusions about disease

association are made.

But he said he is unwilling to state that the

reported link between XMRV and CFS or prostate

cancer is no longer viable.

The papers focus on various problems associated

with a specific kind of test used to detect XMRV but

does not examine every method used to detect

XMRV.

pointed out that some of the previous

papers on prostate cancer found XMRV integrated

into the patients' DNA and " I can't come up with a

mechanism where there would be contamination

there. "

Judy Mikovits, who led the team of researchers that

published the link between CFS and XMRV in Science

last year, said her team was able to culture XMRV

from the patients' blood and show antibody

responses indicating they had been exposed to XMRV

at some point.

" You will not make an immune

response to a lab contaminant, "

she told Health Blog.

Dr. Coffin said the debate over XMRV will continue.

" This is not the end of XMRV, " Coffin said, " but it is

a warning we have to be very, very careful. "

Update: This post has been updated to clarify

information on one of the papers' authors.