From “Scicasts”, a life sciences research blog, 13 January 2o11
London, UK (Scicasts) – Last week (on Thursday, January 6th, 2011), we published the story: Chronic Fatigue Syndrome Not Caused By XMRV Virus, reporting the Wellcome Trust's research which stated that XMRV virus – previously thought to be associated with chronic fatigue syndrome – is not the cause of the disease. We received many comments and e-mails from our readers criticizing Wellcome Trust's conclusions and we have asked their leading scientists, who published the report, to respond to our readers.
Below, is the official statement that we have received from Professors Greg Towers and Paul Kellam:
On 20 December 2010, the peer-review journal Retrovirology published a series of papers relating to XMRV, a virus previously linked to CFS/ME. These included our paper,Disease-associated XMRV sequences are consistent with laboratory contamination by Hue et al at University College London (UCL) and the Wellcome Trust Sanger Institute, with funding from a number of organisations including the Wellcome Trust.
In our study, we showed that it is extremely unlikely that XMRV is a human pathogen or one which transmits between humans. There has been much discussion of what exactly we can and did conclude from our observations. We would like to take this opportunity to reiterate the following.
Comparison of XMRV found in patients and XMRV found in the prostate cancer cell line 22Rv1 tells us that patient-derived XMRV sequences do not contain sequence variation that invariably accompanies transmission of retroviruses between individuals. XMRV is like any other virus: it has a genome, which, when replicated during the process of infection, accumulates mutations, with the number of mutations acting as a counter for the number of replication events. XMRV is not able to replicate without variation and we showed this by determining the sequence variation of the virus in the 22Rv1 cells. Thus we can conclude that XMRV sequences from CFS samples are not from a virus that has transmitted between individuals and thus cannot be the cause of chronic fatigue syndrome or prostate cancer.
The Scicasts blog contains some criticism [from its readers] of our methodology and the fact that we addressed only one component of the research originally published in Science. We used established scientifically accepted and rigorous protocols that are in no way dependent on user bias. We, and the other papers in Retrovirology, did indeed address one component of the research originally published in Science, namely that of PCR assays. However, this type of assay is used in all XMRV and CFS studies, is the most sensitive and when coupled with sequence analysis the most specific. Therefore by showing that the original assertions that are made using this assay are flawed we conclude that those studies are compromised.
Our study did not address the issue of anti-MLV antibodies in CFS patients and we therefore cannot conclude anything about these observations. However, we would expect to see the description of anti-MLV antibodies in CFS patients to be reported in more than one laboratory before this technique was used diagnostically. To the best of our knowledge, no other peer-reviewed research has been able to provide evidence of anti-MLV antibodies in CFS patients.
We recognise that chronic fatigue syndrome/ME is a very real and distressing condition. It is important to recognize that we are not claiming that CFS/ME is not caused by a virus – this may well still be the case. It is still not clear what causes the condition and it is important that scientists explore all avenues of research to identify its cause or causes and enable better treatments.
We are committed to understanding and identifying virus causes of human disease. We are similarly committed to giving both the scientific community and lay audiences accounts of the findings of their work, and that was what motivated us to issue our joint press release.”