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Responses to Retrovirology XMRV articles
Friday 24 December 2010
The recent reports published in Retrovirology (see yesterday's news item) have prompted numerous – and occasionally vehement – responses.
Here are just a few...
WPI Statement Regarding Retrovirology Article
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
Yesterday the Chicago Tribune published my reaction to the four papers on the retrovirus XMRV published this week in the journal Retrovirology. I was quoted as saying ”These four papers are probably the beginning of the end of XMRV and CFS”. I wish to retract this statement and explain my reasons for doing so.
Early Monday a reporter for the Chicago Tribune, Trine Tsouderos, sent an email asking for my thoughts on four XMRV papers that had just been released (paper one, two, three, four). I read all four papers and decided that they raised serious concerns about the role of XMRV in human disease. Specifically, the four papers demonstrated different ways that assays for XMRV could be subject to contamination with murine viral sequences. I wrote an email to Ms. Tsouderos outlining my summary of the papers, and later that day her article was published. My statement was reproduced exactly from the email I had sent her, so I was not misquoted.
I then set out to write about the papers for my blog about viruses. I read the papers over again, and began checking XMRV sequences in Genbank. I also began an email correspondence with authors of three of the four papers, and spoke with my virology colleagues here at Columbia. As a consequence of this additional research I decided that my initial impression of the papers was incorrect, which is evident in my post entitled ‘Is XMRV a laboratory contaminant?‘. Almost immediately after publishing the piece readers began to ask why my comments to the Chicago Tribune had such a different tone. I concluded that a retraction and explanation were necessary.
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.
I would like to apologize to anyone who was offended, angered, or disappointed in any way by my statement to the Chicago Tribune. It is my goal to educate the public about virology, and clearly I did not do that very well.
There are at least two lessons that you can take away from this incident. First, that I make mistakes, and that I’m willing to admit it. Everyone does, including scientists. Second, if I had difficulties interpreting these papers, how would non-scientists fare?
Norwegian blogger Merutt with comment from Meirleir on contamination papers
Governments and insurance companies are horrified by the idea that there is a new retrovirus out there that has infected 10 times more people than HIV up to date. My preliminary data show that the virus does not grow in culture anymore after Nexavir + GcMAF although the procedure was identical to the pretreatment culture.
In the next months more will come from our side. A study with healthy blood donors, ME patients who got ill immediately after blood transfusion and ME patients who gave blood after they got ill will be published in the first half of 2011.
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