some comments on replication possibilities
Dr Peterson answers this very concern as follows:
http://aboutmecfs.org/Rsrch/XMRVPeterson.aspx
Garcia,
I thought Dr Peterson's answer was about direct mouse contaminants, and not about the possibility of MLV contaminants in media, or direct from humans running the test, or already present in the blood of the test subjects. Maybe he has addressed these other issues as well, but I have not heard of that.
But regardless, this issue can not be settled by careful analysis of what WPI has stated, or how they defend their work verbally. Only replication studies can confirm or disprove the WPI findings.
Kurt,
Nobody, least of all me, has assumed that the German study is a mis-measurement. My take on it is a guess, not an assumption. Everything is speculation at this point. My guess is based on the finding of ZERO XMRV in a population where you would expect to find at least some. Thats a red flag.
Repeat, XMRV has been found in other German studies, although at a rate less than in the US. If thier methods were correct, it follows that the German study should have found at least some XMRV. Or not. With the pros arguing among themselves, how are we lay folk to know more that they do? There is really nothing much to discuss without follow up studies, I agree with you on that point.
As for bias, I am on record here stating that I personally do not wish to be found to be infected with this cancer causing retrovirus. So if I have a bias, it runs in the opposite direction.
Levi,
Sorry if I misunderstood your viewpoint, these quick reads and posts are sometimes misleading, and who has time to go back and read every poster's history to understand their mindset... Anyway, I agree, the disparity in the German studies MAY be a red flag. But for what? Which side is in error?
And I agree with you, I would rather the pathogenesis of CFS not include a dangerous retrovirus. At this point I believe XMRV is a very unlikely explanation for CFS, for many reasons that I have posted previously (sorry, just no time to recount here). But unlikely does not mean impossible, again, we must wait.
Kurt, there was speculation here if there is xmrv in ticks, mainly because ticks feed on mice first (not deer...)
Several lyme patients have asked that question.
Also, some lyme patients wonder if the reason for treatment resistant lyme is XMRV (from ticks that feed on mice first)
Can you ask your friend to test some ticks?
Can he develop a more sensitive PCR test for lyme? (there is a lab in Poland that has a new real-time PCR test for borrelia, and some patietns have tried it and it detected borrelia DNA but after they took some grape seed extract that butst cysts. Discussion found on lymenet when searching pcr poland)
Nora,
That is actually an interesting idea that I will run by my contact, testing ticks. I know that HIV has been proven to persist for a short time in one species of African tick. But they must know what they are looking for, PCR requires a specific DNA sequence for the target, it is not a scan.
And yes, I believe he could develop a Lyme test so sensitive it would detect a single spirochete in a sample. I don't know about the cyst busting, but believe that can be done in the lab also, should not have to rely on the patient for that. I have mentioned this to him already, that there should be more sensitive Lyme testing, and a computational real-time PCR could definitely accomplish that.
Here and elsewhere it was clearly stated that the XMRV found in the CFS patients was not identical to that found in the prostate cancer samples and not identical to that found in mice. The question of lab contamination via mice was brought up when the study came out and it was settled then. These retroviruses are different! I wish to put to rest the fears about mice and the rumor/belief that XMRV is part of the Lyme from ticks business.
I have also read, via the media links thread, that XMRV is a very simple, primitive retrovirus which replicates and changes very slowly.This is the opposite of HIV which replicates and changes so fast, the drugs have to keep changing too. Because of the slow replication rate, it is thought that anti-retrovirals won't work so well for XMRV because the current design of those drugs goes after the virus while replicating. At the same time, it will be easier to develop a vaccine because of the stability of the virus, it was said.
Cecelia
Cecelia,
According to what WPI has said, the differences between the XMRV versions are very, very minor. A good computational RT-PCR test will account for that, as the newer computational tests (which WPI is not using) can predict possible mutations and scan for them. This can be done because some areas of the genome are known to be more and less stable, so that can be taken into account.
As far as contamination, there may be other MLV species that are similar to XMRV genetically that can contaminate media. There is some evidence this can happened, a study in Germany found an engineered virus in a different lab from where it had been supposedly secured. So some of these viruses can get around and cause contamination through some other vectors, perhaps even through humans. So no mice are required for contamination to occur, there can be other causes of viral contamination. Therefore ruling-out mouse involvement does not rule out contamination.
As far as slow replication, I read that as an inference to explain the lack of variation in the bug in different samples. So maybe there is an alternate interpretation for that phenomenon, some type of contamination.
A PERSONAL COMMENT - I am a little conflicted about the CDC and some other labs that already have data and have not shared that yet. On the one hand I wish they would spill the beans so we could move forward, but on the other I appreciate that they must be really, really certain before they say what they have found. I am fortunate to know an insider, and have been able to learn a lot quickly about PCR testing and what is happening with some of the replication studies. Hopefully they are working fast and furious on their write-ups and we will see some results in the next month or two. Waiting is hard.