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XMRV Positive(Latent)Negative(Active)

Discussion in 'XMRV Testing, Treatment and Transmission' started by ldhunter, Dec 28, 2009.

  1. ldhunter

    ldhunter

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    I guess my question is: What does this mean? Help with the translation :)
    Thanks!
  2. _Kim_

    _Kim_ Guest

    Welcome to the forums ldhunter.

    Positive by culture, negative by PCR. It means that you have tested positive for XMRV.

    Remember though, that the test hasn't been FDA approved, validated or replicated yet.

    There are currently 3 other members here who received the same results as you as shown on the poll.

    Would you consider adding your results to the poll as well? With so little information coming out, this is one of the only ways that we know anything about XMRV testing and results.

    Above all, I would ask if you have some support right now to talk about your test results. Is there someone with whom you can share your feelings and reactions with? This could be a hard time, no matter what result you were 'hoping' for.

    Best of luck,
    Kim
  3. dsdmom

    dsdmom Senior Member

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    What I would like to know is what does it mean, exactly, if your infection is latent? Does that mean that it is not causing any symptoms/problems? I'm trying to wrap my head around this since there are plenty of folks on here that are testing positive for the latent infection and yet still are ill. So if the infection is latent, would you not take medication for it? (if there were some available?)
  4. Mithriel

    Mithriel Senior Member

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    I think the active part means it is actually in the process of replication in the blood sample, if it isn't it's latent.

    This doesn't mean it wouldn't have been replicating if the sample had been taken an hour later so it doesn't actually say anything about your illness beyond XMRV being present.

    I could be getting it all wrong though.

    Mithriel
  5. mentalist

    mentalist

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    Lurking and first post here.

    As explained to me by someone in regards to XMRV:

    Latent can mean two things with retroviruses, it can be incorporated into the DNA and silent or it can be expressing viral proteins, such as envelope protein or gag protein. It can be expressing other viral proteins and also influence other human DNA expression such as oncogenes that cause cancer.

    As it tries to replicate by forming viral proteins to assemble new viruses inside the cell, it might activate cellular RNase-L which keeps it from forming infectious virion but will make you sick from RNase-L activation.

    Latentcy, while not infectious, can be very active and has effects inside the cell and outside the cell as the body reacts to viral proteins that make it outside the cell and by the immune responses to the virus inside the cell and to the viral proteins on and outside the cell.
  6. Hi Mentalist (love the user name!!!).

    Two questions please:

    1)

    Would someone with RNase-L problems associated with ME/CFS be more likely to be XMRV positive do you think?

    I see the blood test for RNase-L is available from America on the VIP website.

    RNAA = RNase-L test.
    $475 - $795 with other assays included in the price.


    2) If XMRV can activate oncogenes that cause cancer, can people get a blood test for this yet?

    Thank you.
  7. mentalist

    mentalist

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    I think I read on this forum that not everyone had abnormal Rnasel that tested positive for XMRV in the study, but I have long stopped being able to find stuff on here, so I am not even positive about that. Good questions, but I do not know the answer to your other questions, but maybe someone will.
  8. gracenote

    gracenote All shall be well . . .

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    RNaseL

    Here's a quote from GMA:

    EXCELLENT OVERVIEW FROM GORDON MEDICAL ASSOCIATES
  9. natasa778

    natasa778 Senior Member

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    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.
  10. Mithriel

    Mithriel Senior Member

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    On the results forum, it says that active means XMRV has been found in the blood by PCR whereas latent means it has been found in the cell by culture.

    Some people get a positive result on both tests, others on one or the other.

    It's possible that latent and active are being used as a short hand for these tests, and being used in a rather loose manner.

    Active - positive PCR
    Latent - positive culture

    Mithriel
  11. Megan

    Megan Senior Member

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

    Hi, I posted this on another thread (the 36% one) but realised I should have put it here (don't know how to move it). It picks up on what Natasa was saying:

    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 "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. Maybe someone who has had the test knows? 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? Then again I am assuming the PCR is testing outside the cell, and now I am wondering if this is right?

    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, I think it would be better at this stage if we simply talked in terms of Culture+, PCR- and let go of the 'active' vs 'latent' tags.

    Regards,

    Megan.
  12. Sala

    Sala

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    I have yet another question:

    According to the Science paper, 67% tested positive for XMRV:
    "Studying peripheral blood mononuclear cells (PBMCs) from CFS patients, we identified DNA from a human gammaretrovirus, xenotropic murine leukemia virusrelated virus (XMRV), in 68 of 101 patients (67%) as compared to 8 of 218 (3.7%) healthy controls."
    http://www.sciencemag.org/cgi/content/abstract/1179052?ijkey=m3wzKT4yJqEyk&keytype=ref&siteid=sci

    By which test was this done? PCR (active)?

    After the study was done, the WPI informed:
    "Since the original Science paper was submitted, we have continued to refine our test for XMRV and
    have surprisingly found that 95 percent ME/CFS samples tested positive for XMRV antibodies in the
    plasma."

    http://www.wpinstitute.org/xmrv/docs/wpi_pressrel_100809.pdf

    Is this increase ((28%) due to the culture test (latent)?

    Or does the 67% result come from both PCR and culture tests, and there is an additional test to measure antibodies in the plasma? :confused:
  13. cfs since 1998

    cfs since 1998 *****

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    Postive PCR does not mean it's active, and negative PCR with positive culture does not mean it's latent. Whoever refers to the WPI/VIP tests as active and latent are simply using the wrong terminology, nothing more to it than that.
  14. Sala

    Sala

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    Thank you for clearing that. Can you please explain the terminology, and what each test means? :innocent1:

    Do you know which test will find XMRV antibodies in the plasma?
  15. I think it will be XMRV IgG Antibodies serology test from VIPdx.
  16. Sala

    Sala

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    Thank you. I found some information here:
    http://www.forums.aboutmecfs.org/showthread.php?940-xmrv-needs-4-tests-(Nov-09)

    To "link" XMRV to CFS, is it then enough to just take the PCR/culture test from VIP? Shouldn't one also take the antibody test? Perhaps no treatment is needed if just the antibody test is positive, but one will know if the virus may have been involved in the process? Some people are upset about their negative PCR/culture tests (which I can relate to), shouldn't an antibody test be a part of "the test package"? As long as this test adds another 28% to the XMRV connection, according to the WPI?
  17. sproggle

    sproggle Jan

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    I totally agree Sala. I don't see the point in only having two out of the three tests. If they're both negative your none the wiser! The antibody test is essential. Remember retroviruses are notouriously hard to detect they hide in your dna we need all the tricks of the trade to detect them. I also believe they will still be refining these tests and accuracy will improve over time.

    Having said that every test is expensive and so it would be prudent to pay for each in turn &you only need one to be positive.

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