The IMEA (International ME Association):
It has been proposed that XMRV was generated from two mouse viruses, called PreXMRV 1 and 2, during in vivo passages through a human prostate cancer cell line. That the later generation of this cell line called 22Rv1, now infected with XMRV, then contaminated the samples found positive for XMRV in the prostate cancer studies.
However, it is not known if the mice "potentially" used to create 22Rv1, which contain these two viruses, already contained XMRV. Alternatively, XMRV could have been already present in the prostate cancer tissue, but at a level too low for an unvalidated PCR assay to detect. Subsequent passages of the cell line where XMRV was detected were injected with testosterone, which would dramatically increase levels of the virus that the PCR assay could detect.
Therefore, it is not possible to claim that 22Rv1 is the source of XMRV or that any possible contamination has taken place. A new hypothesis for the positive results must also explain the observations recorded by Kim et al (2008), which Garson et al (2011), was unable to do. These issues must first be addressed if one wishes to argue differently. Read more>>