XMRV & Blood Supply -More Study Needed

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March 7, 2011,

XMRV and the Blood Supply:

More Study Needed.

By Amy Dockser Marcus

In the ongoing effort to understand XMRV and

related retroviruses, a key concern has been

assessing whether a risk exists to the nation's blood

supply. In separate reports published online in the

journal Transfusion, two task forces working on the

issue say there's still no conclusive answer.

The task forces were set up in the wake of a study

published in 2009 in the journal Science that found

the retrovirus XMRV in 67% of 101 patients with

chronic fatigue syndrome. XMRV was also found in

around 4% of the healthy people in the same study,

raising the possibility that people who had the virus

but were not sick might donate blood. Subsequent

studies have led to conflicting results, with some

labs not able to find XMRV or related viruses in

either CFS patients or healthy controls.

The task forces charged with assessing risk to the

blood supply face a particularly difficult challenge.

The science is still uncertain, questions have been

raised about whether some samples could have been

contaminated with mouse DNA, the virus's origins

and life cycle are still being worked out and

scientists continue to debate almost every aspect of

the retrovirus.

Amid all of this, blood collectors and federal public

health officials have to make decisions without a lot

of clear information. They don't want to exclude

donors who don't need to be excluded, and they

don't want to expose recipients to pathogens that

might make them sick.

In December, the blood products advisory committee

to the FDA recommended that people with a CFS

diagnosis be barred from donating blood. The FDA

has not yet ruled on this recommendation. The

American Red Cross decided last year to bar people

with CFS from donating blood.

In a report published online last week, the HHS

Blood XMRV Scientific Research Working Group said

that its members evaluated both published and

unpublished data to gauge whether transfusion was

associated with the development of either CFS or

prostate cancer. XMRV was originally discovered in

2006 in prostate cancer patients.

The working group concluded that so far there is no

convincing evidence that transfusion is associated

with either disease. But because the data are

sparse, especially for CFS, the report recommended

that additional epidemiologic studies looking for any

possible association between transfusion and the

two diseases be conducted.

Conducting such studies will be difficult, though,

says Shurin, acting director of NHLBI, the NIH

agency that is organizing and coordinating the task

force.

There is still no agreed-upon test that could be used

to screen blood donors, and not enough is

understood about the family of retroviruses. " There

are too many things we haven't worked out yet, "

Shurin tells the Health Blog.

With many viruses, not everyone who is exposed

gets sick. Teasing out the subtle immune

deficiencies that might make one person more or

less susceptible is very difficult to do in an

epidemiological study, she adds.

Efforts to try to get a better handle on the

prevalence of XMRV and related viruses among blood

donors continue to move forward. There are plans to

test blood from approximately 300 blood donors and

depending on the results, more studies might be

needed. Among the possible studies: evaluating

donors in a larger, more geographically diverse group

and studying blood samples stored in federal

repositories to look at XMRV in donors over time.

The second task force — set up by the AABB, whose

members collect most of the nation's blood supply —

reached a similar conclusion. In June, AABB advised

its members that people with a diagnosis of CFS

should not give blood until more is known.

The AABB interorganizational XMRV task force

report, which was recently published online, also

concluded that more studies are needed.

Harvey Klein, chair of the task force, tells the Health

Blog that the group " remains concerned there may be

a transmissible agent. " The task force, which also

includes two representatives from Canada's blood

services, holds teleconferences every six to eight

weeks to review both published and unpublished

data.

Klein says the constant monitoring will allow blood

collectors to act quickly if they decide it is necessary.

In the meantime, Klein says, *We just don't know

yet.*