XMRV: Raising the Issue of Contamination. (Brits try to debunk XMRV-CFS link, US objects)

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.

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.”

But John 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.”

Some scientists, mostly aligned with the UK National Health Service, have overstated their PCR analysis claiming that they have debunked the link between the newly discovered XMRV virus and both ME/CFS and prostate cancer.

Dr. John Coffin of the US NCI co-authored two of the papers and he says flat-out that his Brit co-authors have overstated their results. I'll go with Coffin.

http://home.ncifcrf.gov/hivdrp/Coffin.html

The UK studies published 12/20 were completed last summer and the contamination issues, though potentially serious, have been addressed and ruled out sufficiently for an FDA advisory panel last week to recommend that all CFS sufferers be excluded from blood/organ donations to to likelihood that CFS is caused by a retrovirus.

Is XMRV a laboratory contaminant?

21 December 2010

Since the first observations that the human retrovirus XMRV is associated with prostate cancer and chronic fatigue syndrome (CFS), new studies have been carried out to determine the role of the virus in these diseases.

http://www.virology.ws/2010/12/21/is-xmrv-a-laboratory-contaminant/

Xenotropic murine leukemia virus-related virus (XMRV retrovirus), first described in 2006, belongs to the virus family Retroviridae and the genus gammaretrovirus.

Livestock retroviruses have been found in humans. Google H-CAEV. CAE is an incurable retrovirus in goats, closely related to one in sheep, OPP. Both cause arthritis, lung damage and sometimes brain damage. Both are transmitted primarily thru milk to offspring. People drink goat’s milk and voila!

The finding of these retroviruses in humans - - mostly in Mexico - - were linked in some cases to disease in humans.
Doubtful that there could be lab contamination with goats!

Here is the response from Judy Mikovits of the WPI, one of the lead authors of the Science study:

http://wpinstitute.org/news/docs/WPIResponseToRetrovirology122010.pdf

Dr. Mikovits Responds The Lombardi et al. and Lo et al. studies were done using four different methods of detection. They were not simply PCR experiments, as were the studies by McClure et al. and others who have recently reported their difficulties with contamination. Experienced researchers such as Mikovits, Lombardi, Lo and their collaborators understand the limitations of PCR technology, especially the possibility of sample contamination. As a result, we and Lo et al. conducted rigorous studies to prevent and rule out any possibility that the results reported were from contamination. In addition to the use of PCR methodology, the Lombardi team used two other scientific techniques to determine whether, in fact, we had found new retroviruses in human blood samples. We identified a human antibody response to a gamma retroviral infection and we demonstrated that live gamma retrovirus isolated from human blood could infect human cells in culture. These scientific findings cannot be explained by contamination with mouse cells, mouse DNA or XMRV-related virus-contaminated human tumor cells. No mouse cell lines and none of the human cell lines reported today by Hue et al. to contain XMRV were ever cultured in the WPI lab where our PCR experiments were performed. Humans cannot make antibodies to viruses related to murine leukemia viruses unless they have been exposed to virus proteins. Therefore, recent publications regarding PCR contamination do not change the conclusions of the Lombardi et al. and Lo et al. studies that concluded that patients with ME/CFS are infected with human gammaretroviruses. We have never claimed that CFS was caused by XMRV, only that CFS patients possess antibodies to XMRV related proteins and harbor infectious XMRV, which integrates into human chromosomes and thus is a human infection of as yet unknown pathogenic potential "The coauthors stand by the conclusions of Lombardi et al. Nothing that has been published to date refutes our data."

Judy A. Mikovits

“XMRV and CFS – It’s not the end”
22 December 2010

By Vincent Racaniello

http://www.virology.ws/2010/12/22/xmrv-and-cfs-its-not-the-end/

(excerpt)

Upon re-reading three of the four Retrovirology papers it became clear to me that they show that identification of XMRV can be fraught with contamination problems, but they do not imply that previously published studies are compromised by these findings. Clearly any new studies done on XMRV should keep in mind the potential for contamination from PCR kits and murine nucleic acids.

I was initially more troubled by the fourth paper by Hue and colleagues. There are four major findings in this paper (gag PCR primers are not specific for XMRV; the virus is present in 5 human tumor cell lines; two XMRV isolates are nearly identical to a virus from the human prostate cell line and also contain an insertion from the murine retrovirus MoMLV; and there is more nucleotide diversity in viral sequences from 22Rv1 cells than in all the patient XMRV sequences). The fact that two XMRV isolates seem to be laboratory contaminants – judged by the presence of MoMLV sequences – was initially unsettling until it became clear that other XMRV isolates do not have this insertion. That leaves the fourth finding – that XMRV from 22Rv1 cells appears ancestral to, and more diverse than, all the human XMRV sequences. I decided that this result was less troublesome than I had originally believed, in part because it is not clear that the differences among the 22Rv1 viruses did not arise during PCR amplification.

My conclusion is that these four papers point out how identification of XMRV from human specimens can be complicated by contamination, but they do not mean that previous studies were compromised. They serve as an important reminder that future experiments to identify XMRV need to be appropriately controlled to ensure that the results are not compromised by contamination.

In other words, these four papers are NOT the beginning of the end of XMRV and CFS. Rather, research on the role of this virus in human disease must proceed, with large, case-controlled epidemiological studies, as suggested by others.

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