A small Dutch study found zero evidence of XMRV in chronic fatigue syndrome patients. In some ways it was the weakest study of the bunch; it used quite old samples and a watered down criteria but it did use the same primers and a similar amount of nucleic acid as the original study. They searched for sequences on two of the viruses three genes. While not a replication attempt an editorial accompanying paper nevertheless asserted that the methods should have been sufficient to detect the virus if it was there -something that analyses by the ME Association and the CFIDS Association appeared to agree with.
The ME Association believes this third study considerably darkens XMRV’s potential for being a major factor in chronic fatigue syndrome stating “these three negative studies now place a very serious question mark over the proposition that XMRV is present in a significant proportion of the ME/CFS population and that the infection plays a significant role in most cases of sporadic ME/CFS.” With regards the different procedures used by the different studies they stated “the various laboratory investigations for finding XMRV have been carried out in very reputable microbiological research centres and involved retrovirologists of international repute.”
They believe the problem lies not in different cohorts or different geographical spread of the virus but in the laboratories doing the testing and urged that the same samples be sent to and tested by the variety of different lands. They also stated that “the MEA Ramsay Research Fund is very willing to consider funding high quality research proposals”.
CFIDS Association’s Response: The CFIDS Association posted their response a couple of hours after the ME Association. Dr. Vernon stated that with three negative studies under our belts it’s was getting much harder to pin the problem on any one methodological error. Instead Dr. Vernon turned to the question of the patients in the original cohort. Were they from an infection cluster (or clusters) as was originally reported? Did they have the immune abnormalities reported or, as was later reported, not?
Dr. Vernon is suggesting that the reason these studies are turning up negative is that none of the patients in them were similar to the patients in the original study; i.e. she believes the original cohort contained a very unusual type of patient.
Since requests for more information on that original group have not been fulfilled Dr. Vernon looked at various bits of evidence from the CFSAC meeting and elsewhere and concluded that least five of the 32 patients she could get information on had had cancer – something that could affect their test results.
Dr. Vernon’s worry is that if XMRV is only found in the blood of a very specific type of patient that unless researchers search for XMRV in this particular set of patients, the search for XMRV will soon be over. She and others have implied that research enthusiasm for continuing the hunt may be waning in the face of these negative results. The fact that it now appears that XMRV is more readily found in the organs than in the blood suggests less ill patients could carry it without showing it in the blood. If that’s true finding it in them will take more digging but for the research community to commit to doing that they’ll have to find it in the blood first.
Whereas they may at times take some flak for doing so both the ME Association and the CFIDS Association of America should be acknowledged for their willingness provide their analysis of what’s going on to the patient population while other groups (MERUK?, IACFS/ME) have hung back. Remarkably, our biggest (but admittedly most amorphous) professional research organization (IACFS/ME) has contributed little or nothing to the discussion on XMRV.
Ongoing ‘Study’ Continues to Find XMRV – one fact that is not being mentioned is that one group has been and continues to find XMRV – daily; the VIP Dx labs.
I had heard that they were no longer able to find XMRV using PCR so I asked them about that. This is their answer.
[QUOTE]No way did VIP Dx stop testing for XMRV using PCR. The culture is done by a PCR method. We streamlined the testing to avoid the high costs that doing both the first run PCR and then the extraction and culture had. We still extract and then grow cells for culture and run the culture test. By streamlining our processes, we have developed a test method that gives higher sensitivity at a cost savings that has been passed on to our patients. Our license agreement with WPI includes consultations and quality assurance by their researchers that we are running the best and most sensitive test available at this time. This high sensitivity method is producing good results in detecting the virus.[/QUOTE]We also know that about half of the people completing the Phoenix Rising Forums poll tested positive using either PCR or culture.
How is little VIP Dx labs able to find XMRV when these larger research labs are not? It seems that there can be only two answers to this question; their culturing technique is in fact critical to finding the virus or the lab has somehow become contaminated with the virus.
A Laymen’s Conclusion: The fact that zero of several 100 people with CFS have tested positive for the virus is alarming. The groups reportedly used more sensitive techniques than WPI investigators did. Even if there are problems with the cohorts or some methodological issues it’s difficult to account for zero results.
Dr. Mikovits believes the fact none of the groups cultured the virus first is critical given how low viral levels are. The fact that, even after culturing the virus, the WPI often had to search several times in different samples to find indicates how low the viral levels are. The other researchers would disagree that they wouldn’t be able to find it. Somebody is obviously wrong.
We’re at a real conundrum. Aside from an unpublished Japanese study that found XMRV antibodies in blood, WPI is the first group, to my understanding, to ever find XMRV in the blood of humans. Their internal validation studies were done by their partners at the Cleveland Clinic and at the National Cancer Institute. These were all small ‘studies’ but they were done at highly reputable labs.
Other XMRV Tests – The WPI also did other tests to confirm the presence of the virus; in particular they did antibody tests and grew the virus in specialized cells. The antibody tests are intriguing because they indicated the patients bodies were responding to the virus; something that would not be happening simply if their samples had become contaminated. The scientific community appears to be focusing on PCR because it provides more or less definitive evidence but the antibody tests are another pillar of the WPI’s argument. A negative PCR result has no effect on the efficacy of a positive antibody result – it just makes it harder to explain.
We have yet to have a US research group publish. There’s no really good reason to suppose that their results should be different yet there has been a considerable divide between the ‘continent’ and the US in XMRV study results.
Dr. Mikovits reported that she’s not worried about these validation attempts; as soon as someone uses the WPI’s methods she expects they’ll get the same results. She also noted that the National Cancer Institute should have some CFS/XMRV studies out fairly soon.
The next step will hopefully be for the WPI and other laboratories to share samples and in a blinded test reveal what they found. If the WPI can distinguish CFS patients from controls using this process their techniques will likely be validated and the other labs will presumably go back to square one.
Good News - As we deal with more negative results we can note that XMRV is pulling its weight elsewhere just fine. Researchers at the San Francisco Retrovirus conference reported that XMRV can quickly infect primates and spread throughout their bodies. They found XMRV in the primates lungs, lymph nodes, spleen, gastrointestinal regions and reproductive areas – an important finding that widened XMRV’s potential impact considerably. Because the study was initiated prior to the CFS study they didn’t search for the virus in the central nervous system but, most intriguingly, they also found it in the smooth muscles lining the blood vessels – a very nice fit for CFS patients with orthostatic intolerance. They were also able to determine that XMRV uses different immune cells to infect different parts of the body.
Again, we’ll close with this illuminating statement
Discrepancies between labs are common, says David Griffiths, a virologist at Moredun Research Institute in Midlothian, United Kingdom, who has studied previous claims for retroviruses as the cause of chronic diseases. He also notes that he cannot find serious flaws with any of the published studies: ‘All the people involved are doing things exactly as they should be.’ For the time being, then, the XMRV results will remain frustratingly ambiguous. As Griffiths says, ‘There must be an explanation for why disparate results are showing up, but it may not be an easy thing to turn up.