In a previous blog in 2009 XMRV - the third infectious human retrovirus I reported that a connection had been detected between Chronic Fatigue Syndrome (CFS) and a mouse-linked retrovirus XMRV, according to a paper in Science.
About 10 months later, in Mouse Wars I reported that these results had been replicated four times but also not replicated four times, and commented that one might expect a mixed bag of results, since different populations (and different methods, and mutually exclusive definitions of CFS) were being used.
Now a further 10 months down the track and there is more news. The initial paper in Science had used three different assay methods (and used different labs) to reach its findings: they really tried to get it right it seems. However, one of the labs has now concluded that its tests were contaminated and the authors have published a partial retraction in Science.
In our 23 October 2009 Report, "Detection of an infectious retrovirus, XMRV, in blood cells of patients with chronic fatigue syndrome," two of the coauthors, Silverman and Das Gupta, analyzed DNA samples from chronic fatigue syndrome (CFS) patients and healthy controls. A reexamination by Silverman and Das Gupta of the samples they used shows that some of the CFS peripheral blood mononuclear cell (PBMC) DNA preparations are contaminated with XMRV plasmid DNA.
The authors have not yet retracted the rest of the paper, based on two other assay methods, however some are also contributors to a further paper: A nine-lab study ... found that none of the labs could reproducibly detect XMRV or relatives of the virus in blood samples distributed under a blinded code. (False Positives)
More specifically, current assays do not reproducibly detect XMRV/MLV in blood samples and that blood donor screening is not warranted. It is not just that the samples in question did not contain XMRV when re-tested: it turns out that the tests themselves are not good enough yet.
There seems no shortage of non-XMRV theories still to be explored.