From the Wall Street Journal health blog, 24 October, 2011 (story by Amy Dockser Marcus).
A team of scientists led by the American Red Cross found no evidence of XMRV or related retroviruses in the blood of either donors or recipients — but the organization still says that people with a medical history of chronic fatigue syndrome should not donate blood.
There has been a swirl of controversy over whether people with CFS are more likely to carry XMRV and whether the retrovirus might play a role in the disease.
In August, the AABB, the umbrella group made up of centers and groups that collect most of the nation’s blood supply, recommended that until the scientific questions were worked out, people with CFS should be discouraged from giving blood. The Red Cross, which collects about 50% of the nation’s blood, bars patients with a medical history of CFS from donating.
But just last month, a federal Blood XMRV Scientific Research Working Group reported that nine labs testing for XMRV or evidence of XMRV infection in the blood of CFS patients and healthy donors either didn’t find the retrovirus or couldn’t reproduce their findings.
The authors of the 2009 paper that found a possible link between XMRV and CFS have partially retracted their findings, citing contamination in some of the blood samples.
The results of the new study, conducted with Abbott Diagnostics, Gen-Probe Inc., and Yale University School of Medicine, were presented on Saturday at the annual scientific meeting of the AABB.
The study sought to estimate the prevalence of XMRV or related retroviruses in a large number of blood donors. The researchers concluded that the prevalence was zero, says Susan L. Stramer, executive scientific officer of the Red Cross and one of the authors of the paper.
The researchers tested blood samples from 17,249 blood donors and recipients for evidence of antibodies to XMRV and related retroviruses, which would indicate a person had been exposed to the viruses at some point. They also tested 1,763 donors and recipients for XMRV RNA, which would indicate an active infection.
In order to test positive, donors or recipients must have antibodies to three specific proteins that comprise the virus. The selection of the proteins chosen for the antibody test was based on extensive prior work done by Abbott and other researchers studying XMRV in macaque monkeys, says John Hackett Jr., manager of emerging pathogens and virus discovery programs at Abbott and an author of the paper.
While a very small number of blood donors and recipients were positive for individual antibodies, no donor or recipient had all three XMRV antibodies present. And further testing for XMRV RNA showed no evidence of the retrovirus.
In the three recipients who tested positive for an individual antibody, the donors who gave the blood did not, leading the scientists to conclude that whatever the origin of the antibody, it did not come from the transfusion, says Roger Y. Dodd, vice president for research and development at the Red Cross and an author of the paper.
Still, the Red Cross is unlikely to change its current recommendation that those with CFS or a history of the disease should not give blood. Stramer tells the Health Blog that even if XMRV is not the cause of CFS, “we still have concern that CFS may have an infectious origin” and that therefore they should not donate blood.
Further studies are still in the works, including an NIH-led study looking at XMRV and related retroviruses and a study funded by the Chronic Fatigue Initiative looking at other pathogens that may be linked to the disorder.
When it comes to blood donation, CFS “needs to be considered in its own right, separate from the issue of XMRV,” Dodd tells the Health Blog.
None of the assay used in the blood working group were optimised to detect human gamma retroviruses. They were all optimised to VP62/XMRV, which does not exist in nature.
They therefore could not have detected the XMRV found in prostate cancer or the HGRVs discovered by Lombardi et al. and confirmed in Lo et al. A free floating clone that does not exist in nature requires different PCR conditions to a retrovirus that integrates into areas with high C:G content.
The host range of the viruses found in people with ME/CFS cannot be said to be VP62/XMRV, when the portion of the paper from Silverman in which the full length of the viruses was sequenced has been retracted. The host range is at this time unknown, but the gag sequences are the same as those found in Lo et al., that being polytropic.
Consequently all studies that have used the VP62 clone to optimise their assays are no longer relevant to the findings of Lombardi and Lo. HGRVs is a new field and the question should be when is the MRC going to fund research using validated assays looking for those viruses?