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XMRV, VIPDx Labs and CFS: the 36% Solution


Senior Member
Why say culture test shows latent virus or refers to white blood cells?

Maybe I have missed something along the line (very possible!), but I dont undestand why we keep referring to the culture test as detecting 'latent' vs. PCR showing 'active' virus? Or that the culture test shows it is confined to white blood cells? I think this is very misleading on several counts:

1) In Dan Peterson's presentation he referred to the 33 people who tested negative on PCR and said "and 30 of 33 had transmissible virus in plasma" (taken from the transcript on this site). To my knowledge plasma does not contain white blood cells. This would indicate the virus was present outside white blood cells in this culture test. I have looked at the VIPdx site and there is nothing there to indicate that the culture test is using only white blood cells. If anyone knows more about exactly what the culture test is culturing then I would appreciate if you could post the information or link explaining this. There seems to be much confusion about this issue on this site. If they are culturing from plasma, then I would have thought the most important question is why are they finding it by culture and not by PCR from the same sample?

2) Even if the culture test did show that the virus was confined to white blood cells at the time of the test, my understanding is that we can't assume this does not mean active disease as we do not yet know enough about this virus. The use of the term latent is therefore very confusing as it implies no active symptoms.

3) As someone else pointed out above, we don't know if a negative PCR on one day could subsequently be followed up by a positive one on another occasion. I wonder about the suggested slow replication rate of XMRV suggested by John Coffin in the CFSAC meeting, postulated on the low level of XMRV genetic variation between patients. Could this mean that the virus only replicates intermittently and could thus only be at high enough levels to be detected by PCR at those times?

4) Though most of us dont want to acknowledge it, it has not yet been proven that the virus is 'active' in terms of causing symptoms in anyone, even in the WPI study. They have merly officially confirmed an association.

As others have suggested on other threads, I think it would be better if we simply talked in terms of Culture+, PCR- and let go of the 'active' vs 'latent' tags.




Senior Member
Hi Megan,

I posted this last night in another thread, just reposting here as fits with what you are saying:

Could someone be so kind and explain why talk about active versus latent test results.

Asking because one of the scientists involved in original XMRV study, the one published in Science :) , stated recently in private correspondence that tests CANNOT distinguish between latent or active infection. The person didn't get a chance to probe further, but the answer was very straightforward, not something that would leave room for discussion anyway.

Can someone shed some light please! (btw I do understand active versus latent infection, just not why everyone talks about tests distinguishing the two when this person was so adamant that science cannot at this point tell what the virus is doing...). Confused.