MLV related viruses - a simpler explanation
For a more in-depth discussion of MLV-related viruses, please see my previous blog entry, here: MLV-related viruses - an explanation
MLV = Mouse Leukaemia virus
MLV's are mouse retroviruses that cause cancer in certain mice.
Judy Mikovits and Harvey Alter have discovered a variety of MLV-related viruses in ME/CFS patients.
These MLV-related viruses are not MLV's (mouse viruses) but they are closely related to them.
The only difference between Alter's viruses and Mikovits' viruses are that they are related to slightly different types of MLV's.
Judy Mikovits' viruses are related to Xenotropic MLV's, and so they are 'Xenotropic MLV-related viruses'.
Whereas Alter's viruses are related to Polytropic MLV's and so they are 'Polytropic MLV-related viruses'.
So the only difference between them is the use of the terms 'Xenotropic' and 'Polytropic'.
The terms 'Xenotropic' and 'Polytropic' indicate a slightly different behaviour of a virus.
XMRV = 'Xenotropic MLV-related virus':
X = Xenotropic
M = MLV (Murine Leukaemia Virus)
R = Related
V = Virus
Alter's viruses are 'Polytropic MLV-related viruses', and so he could have named them 'PMRV' (instead of XMRV). He hasn't named them PMRV, yet. Instead, he refers to them as Polytropic MLV-related viruses, or just MLV-related viruses.
All of the viruses found so far in the two papers, are MLV-related viruses, and they are Human Gamma Retroviruses (HGRV's), which is an umbrella term.
'Xenotropic' means that a virus cannot infect, or exist as a complete, replicating virus in its original host species (i.e. mice), but it can jump to another species (i.e. humans) where it can become a whole, complete, replicating virus.
'Polytropic' means that a virus can infect both its original host species (i.e. mice) and it can jump to another species (i.e. humans).
The difference in the meaning of the two terms is why the new viruses that Alter has detected cannot be called XMRV. Alter's viruses are related to Polytropic MLV's, not Xenotropic MLV's.
It remains to be seen how all of these new viruses, or variants, will be labelled and categorised.
XMRV's (more than one variant of XMRV has now been detected by Judy Mikovits) are clearly a subset of a larger group of viruses (MLV-related viruses and Human Gamma Retroviruses).
We might end up with a new collective name for all of these MLV-related viruses.
[UPDATE: It was reported, from the 1st International XMRV Conference, that Judy Mikovits suggested the name Human-MLV-Related-Virus (HMRV) to encompass Xenotropic and Polytropic MLV-Related Viruses.]
Are Alter's viruses and Mikovits' viruses different variants of the same virus, or are they totally different viruses?
Obviously there are differences, but the similarities seem to be more significant than the differences.
Alter says that these differences are exactly what he expects to see in a retrovirus, so these observed virus mutations support the type of human retrovirus infection that Mikovits' XMRV research indicated.
Alter says that the Hep C and HIV viruses exhibit the same pattern of variants as this new type of human retrovirus that Alter and Mikovits have found in ME/CFS patients.
Indications from Alter are that all these viruses might be referred to as variants of a single disease associated virus, just the same as the multiple Hep C virus variants are often referred to as the Hep C virus (singular).
Of course, it might turn out that these retroviruses are also associated with other diseases, such as Fibromyalgia, Gulf War Syndrome, MS and Autism.
It has recently been reported that Judy Mikovits has also now found polytropic MLV-related viruses in some of the samples from her original Science study. This means that Mikovits is finding more than one virus type in individual patient samples.
See here for a diagram, extracted from the Alter & Lo paper, of a 'phylogenetic tree' (i.e. a virus family tree) of MLV-related viruses... Specifically, the diagram shows the relationship of viral gag gene sequences, taken from blood samples of CFS patients and blood donors in Alter's paper, with other MLV's:
One other interesting thing to note is that the 'commentary' in PNAS says that:
So I believe that whether these new viruses are related to either polytropic, or xenotropic MLV's, is not clear-cut and is not particularly significant... It's just a case of wording, and possibly an unfortunate case of using an 'X' in the naming of XMRV.
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MLV related viruses - a simpler explanation
Blog entry posted by Bob, Aug 30, 2010.