Thursday, July 28, 2011

XMRV - The case against contamination

by Bob on July 2011,


I’ve collected together some of my posts from the forum about XMRV and contamination.
The numbers in brackets, e.g. (1), point you towards the 'references' at the bottom of the page, for further info.

In this blog, I discuss the evidence that I believe demonstrates that each of the contamination theories relating to XMRV is not based on conclusive evidence, or even based on the balance of evidence.

With such an overwhelming number of negative XMRV/CFS studies published, it is easy to assume that XMRV in CFS patients is just a case of contamination, and that the WPI's research is just plain wrong.

I am not trying to argue that contamination isn’t an issue to be taken seriously, but I am presenting the evidence to show that the case for contamination has not been proven, and that there is still a lot more research to be carried out before we gain a good knowledge about XMRV, and any related viruses.

I've avoided detailed analyses of the specifics of individual studies, but I've provided links for further information, in the 'references' section.

I'm not going to cover all the issues, but I'm going to try to explain why our total knowledge about XMRV is still in its infancy and why it is far from proven that the XMRV discovered in CFS patients is due to contamination.


Although there have now been a large number of negative XMRV studies, there has also been a handful of positive XMRV studies (14), mostly unrelated to CFS. On top of this, there are a large number of ongoing investigative XMRV studies (14), which, for example, look at the cellular action of XMRV. There is still only one published positive study that shows a convincing association between XMRV and CFS, but there are reportedly a number of positive XMRV/CFS studies in the pipeline (15).

The Alter & Lo study which detected P-type MLV-related viruses hasn't satisfied everyone, in terms of it being an XMRV validation study, but the results of the Alter/Lo study are interesting in their own right, and have probably given added impetus to the XMRV reseearch.

There is a great deal of ongoing scientific investigation into XMRV, and unfortunately it's probably going to be a long time before there are any firm conclusions about if, and how, XMRV affects ME/CFS patients and the rest of the population.

It has been stated by various people, that XMRV is a contaminant, or that XMRV is not a real virus, or that there is no association between XMRV and CFS/ME, or that XMRV is not a human virus. The CFS community has also been told that “it’s a bust”, and that we should forget about XMRV and not worry ourselves about it.

But all of these statements and conclusions are currently just opinions because there is no scientific consensus, as the many published research papers offer conflicting results and evidence. There is so much that we don't know about XMRV that it is far too early to draw any conclusions from the relatively tiny amount of research that has been carried out so far.

Contamination theories

These are the contamination theories that we have to date:

Theory 1. Detection of XMRV is due to false PCR readings (i.e. cross reactivity).
Theory 2. XMRV is not a virus but only mouse DNA contamination.
Theory 3. XMRV is purely a mouse virus.
Theory 4. XMRV is DNA contamination from a cell line.
Theory 5. XMRV is purely a cell line virus (Purely a lab artifact).
Theory 6. XMRV is a wild human virus but doesn't exist in CFS patients.

The WPI’s research and the original Science paper have been accused of all of these.

There seems to be a general scientific consensus that the first 4 have now been disproved, and that XMRV is actually a real virus. That doesn’t make the WPI’s research immune from the first 4 contamination theories, but the strength of the WPI’s original Science paper is such it is hard for these theories to stick.

So let’s go through each of these theories in turn... Read more>>

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