Thursday, January 13, 2011

Sato et al failed to offer evidence of XMRV contamination and here is why

By Isabel Greenwood, (12 January 2011) PA institute:

A number of retrovirologists have expressed a belief that the recent discovery of MLV related viruses in people with Myalgic Encephalomyelitis also called Chronic Fatigue Syndrome (ME/CFS) and Prostate Cancer Patients are in fact contaminants. Four studies were posted simultaneously in this journal in Dec 2010 where the authors offered their interpretation of their findings as evidence in support of their hypothesis. Others have argued that alternative explanations of their findings are readily available. They argue that even without other lines of evidence, not considered in these studies, an alternative interpretation argues against the advocates of contamination argument. This letter focuses on a critique of one of these papers namely the one authored by Sato and others (1).


This analysis will now focus on two extracts from the abstract which form the foundation of the entire study.

“We purchased four one-step RT-PCR kits from Invitrogen, TaKaRa, Promega and QIAGEN in Japan. To amplify the partial gag gene of XMRV or other MLV-related viruses, primer sets (419F and 1154R, and GAG-I-F and GAG-I-R) which have been widely used in XMRV studies were employed.”

Sato et al point to the fact that these primer sets have been widely used in XMRV studies. They do not state however that these primer sets used in a one step RT-PCR or a single round PCR have never been able to detect even population levels of XMRV (3, 4) or any other MLV related viruses.

Indeed Danielson et al (5) demonstrated that primer sets which could readily detect XMRV sequences in vitro could not do so in a patient sample known to be infected, by a PCR assay targeting the env gene, or serological methods. Thus these primers in studies could not have detected this RNA sequence because they could not detect a MULV sequence of any kind.

“We also determined the nucleotide sequence of a partial env region of the contaminant and found that it was almost identical (99.6 %) to the PmERV.”

Sato and others relate that they partially sequenced the env region. One must ask why they did not sequence the entire env region which would then have enabled the virus to be identified. This is most unfortunate. In fact no region of the virus which would have enabled unequivical identification of the virus was sequenced at all.

The PCR assays used by Sato could not have detected a contaminant in any XMRV study because when they were used no MLV or MLV related virus of any kind was detected.

The authors here have not taken any of the available opportunities to identify the virus. It is therefore difficult so see why this study has been presented as offering evidence in support of those who argue contamination when it clearly does no such thing.

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