Murine leukemia viruses (MLV), including xenotropic-MLV-related virus (XMRV), and the related polytrophic murine leukemia viruses (P-MLVs) were looked for in blood samples of healthy donors who were previously known to not have the viruses.

In a recent study, blood samples were taken from healthy donors and from 14 patients with chronic fatigue syndrome (CFS) who had previously tested positive for XMRV or P-MLV, and samples from another person who had tested positive for XMRV but who did not have CFS. The study also used blood samples from healthy volunteers whose blood tests previously had shown no signs of XMRV/P-MLV. The scientists used 11 nucleic acid, five antibody, and three culture assays to determine the assays’ abilities to detect XMRV/P-MLVs. The study also checked for evidence of contamination with mouse DNA, because XMRV or its predecessors may be present in some mouse strains and cell lines. The MLV have been controversially linked to CFS.

The samples were blinded with no indication as to their source, and sent to nine laboratories. The study involved laboratories supported by several US governmental agencies along with Abbott Laboratories (Abbott Park, IL, USA), GenProbe, Inc. (San Diego, CA, USA), and the Whittemore Peterson Institute (WPI; Reno, NV, USA). The laboratories reported similar rates of finding XMRV in samples from patients with chronic fatigue syndrome and from healthy donors who were known to not have XMRV. Additional tests run in the same and other laboratories on the same samples did not find XMRV, strongly suggesting that these persons were negative for XMRV/P-MLVs. This would be a sign that the few observed positive results represented false-positives, which means the results indicated the condition was present when it actually was not.

Susan B. Shurin, MD, from the US National Institutes of Health (Bethesda, MD, USA), said, “The results of this study, along with other recent findings, reassure us that these viruses do not pose a threat to the safety of the nation’s blood supply. These data add to the mounting evidence that there is no need to screen blood donors for them at the present time.”

The report was published on September 22, 2011, in the journal Science Express.

Related Links:
Abbott Laboratories
GenProbe
US National Institutes of Health