MRC National Institute for Medical Research, London
Science for Health
Retrovirus not found in chronic fatigue syndrome patients
15 February 2010
Chronic fatigue syndrome – also known as myalgic encephalomyelitis (ME) – is estimated to affect around 250,000 people in the UK. It can be a debilitating condition, with symptoms including chronic, often severe, mental and physical exhaustion, muscle and joint pain and cognitive difficulties. The causes of chronic fatigue syndrome are unclear and the theories have often provoked controversy. A 2009 study in the US found evidence of a retrovirus known as XMRV in two-thirds of chronic fatigue syndrome sufferers compared to less than one in twenty controls. This strongly suggested a link between the virus and chronic fatigue syndrome.
Kate Bishop (pictured) and her group in NIMR's Division of Virology worked with Jonathan Stoye, also in NIMR's Division of Virology, and colleagues in London and Glasgow to look at the same issue. They used a technique known as PCR to study 299 DNA samples from UK cohorts, including 142 samples from patients with chronic fatigue syndrome. PCR is a highly sensitive method used to detect and amplify minute traces of DNA for analysis. Despite using a very sensitive PCR technique similar to that applied in the earlier US study, the UK study failed to detect any traces of XMRV in the patients.
The researchers also analysed blood samples from these patients and a further twenty-eight samples from a second patient cohort (a total of 170 samples) to look for the presence of neutralising antibodies against XMRV; detection of these antibodies would provide evidence that the patients had previously been infected with XMRV. Only one patient (less than 1%) was able to neutralise XMRV. Although twenty five out of 395 control samples (just over 6%) were also able to neutralise the virus, in many cases, this seemed to be a broadly acting, non-specific response suggesting that serological studies may overestimate XMRV frequency.
Our study failed to replicate the results of the US study despite using what we believe to be a more sensitive test. We found no association between XMRV and chronic fatigue syndrome. However, chronic fatigue syndrome may encompass a spectrum of different conditions providing a possible explanation for this discrepancy.
Chronic fatigue syndrome affects a large number of people and our findings are likely to be very disappointing to these patients, their families and their friends. It is important that we keep an open mind about new scientific discoveries which point to possible causes of this often very serious condition. Replication is an important part of the scientific method and, as the initial findings have not yet been replicated, I think it will be important to develop standardised samples and assays for XMRV that can be rapidly tested by different laboratories around the world.
Kate Bishop
Original article
The research findings are published in full in:
Harriet C T Groom, Virginie C Boucherit, Kerry Makinson, Edward Randal, Sarah Baptista, Suzanne Hagan, John W Gow, Frank M Mattes, Judith Breuer, Jonathan R Kerr, Jonathan P Stoye and Kate N Bishop. (2010)
Absence of xenotropic murine leukaemia virus-related virus in UK patients with chronic fatigue syndrome
Retrovirology, 7(1):10. Publisher abstract
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