XMRV Controversy Continues: Contamination Issues

Ever since the news broke last year on XMRV, the ME/CFS world has been taken by storm by all of the media, controversy and politics surrounding this virus that is now believed to play a major role in ME/CFS.  As I have stated probably hundreds of times by now on this blog, I am not a medical professional and I admit that when I try to read a lot of the medical terminology in the reports dealing with XMRV, my head starts to spin and everything is a big blur.  It is very confusing to me but I try to put together bits and pieces of what I can understand in order to educate myself to the best of my ability on the subject. 

On December 20, 2010, four papers were published in the Retrovirology journal and an additional paper was published commenting on the the four published reports.  These reports state how easy it is for mouse contamination to interfere with lab experiments that involve XMRV.  According to the WSJ’s Health Blog:

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.” Tests used to detect XMRV are also able to detect mouse DNA, and even if a tiny bit of mouse DNA gets in a lab sample, the test can be positive even if the patient is not, he explained. He added that he was not intending to criticize the work of other scientists. ”They published their observations in good faith and we have simply reexamined their findings and made new observations and come to a more likely conclusion.”

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.”

Robert A. Smith, a research assistant professor at University of Washington in Seattle who wrote a commentary in Retrovirology summarizing the studies, told Health Blog that the possibility of contamination means that future studies must be done very carefully before conclusions about disease association are made. But he said he is unwilling to state that the reported link between XMRV and CFS or prostate cancer is no longer viable.

The papers focus on various problems associated with a specific kind of test used to detect XMRV but does not examine every method used to detect XMRV. Smith pointed out that some of the previous papers on prostate cancer found XMRV integrated into the patients’ DNA and ”I can’t come up with a mechanism where there would be contamination there.”

Judy Mikovits, who led the team of researchers that published the link between CFS and XMRV in Science last year, said her team was able to culture XMRV from the patients’ blood and show antibody responses indicating they had been exposed to XMRV at some point. ”You will not make an immune response to a lab contaminant,” she told Health Blog.

Dr. Coffin said the debate over XMRV will continue. ”This is not the end of XMRV,” Coffin said, ”but it is a warning we have to be very, very careful.”

To me, this whole XMRV controversy is extremely frustrating.  Everytime it appears that we are on the edge of getting an answer to ME/CFS, the politics surrounding it get in the way and it’s like we’re being fought tooth and nail to NOT have an answer.  Everything boils down to money and if a cause for ME/CFS is found, more money will have to be allocated toward research and I feel the CDC and government are going to do whatever they can so that doesn’t happen. 

Here are the links to the Retrovirology journal reports from December 20th:

An additional article was published on December 22, 2010:

After the above reports were released, the Whittemore Peterson Institute responded as to how they handled their XMRV testing.  Here is what they had to say:

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.

Then to add fuel to the fire, on December 20th, virologist Vincent Racaniello of Columbia University wrote in an email (see Studies Cloud Chronic Fatigue Research) in the Chicago Tribune article:

“These four papers are probably the beginning of the end of XMRV and CFS.  They don’t prove that XMRV (and related viruses) don’t cause CFS, but they go a long way to explaining many of the different findings in different labs.”

But then today, Racaniello RETRACTED his statement/email that was published in the Chicago Tribune and wrote his reasons for doing so on his website, Virology Blog.  He says in his post, XMRV & CFS – It’s Not the End:

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.

He went on to apologize for offending anyone and he was willing to admit that he had made a mistake, which I feel takes a lot of courage.  Here is another statement which really jumped out at me that he said:

If I had difficulties interpreting these papers, how would non-scientists fare?

He is right.  This is an educated man whose life work is researching and studying this sort of thing.  How are you and I, patients, just average, everyday people, ever supposed to comprehend what is happening in regards to our health?  We can educate ourselves, yes, but we can only understand to a certain degree.  All I know is this is another big mess but at least it is getting ME/CFS in the media and it is getting  a lot of attention right now.

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