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 USA, led by Dr Vincent Lombardi at the Whittemore Peterson Institute for Neuro-Immune Diseases found evidence of a retrovirus known as XMRV in two-thirds of people with chronic fatigue syndrome compared to less than one in 20 controls. This strongly suggested a link between the virus and chronic fatigue syndrome.
However, in a study funded by the Medical Research Council (MRC), the Wellcome Trust and the CFS Research Foundation, researchers failed to replicate these earlier findings. This new study supports research published earlier this year in the journal 'PLoS One' which also failed to replicate Dr Lombardi's findings.
Researchers at the MRC National Institute for Medical Research and St George's University of London used a technique known as PCR to study 299 DNA samples from UK cohorts, including 142 samples from people 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 by Dr Lombardi and colleagues, the UK study failed to detect any traces of XMRV.
The researchers then analysed blood samples from this group and a further 28 samples from a second cohort (a total of 170 samples) to look for the presence of neutralising antibodies against XMRV. Detection of these antibodies would provide evidence of previous XMRV infection. Only one sample (less than 1 per cent) was able to neutralise XMRV.Although 25 out of 395 control samples (just over 6 per cent) 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.
Dr Kate Bishop, a Wellcome Trust Research Career Development Fellow who led the study, comments: "Our study failed to replicate the results of Dr Lombardi's 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."
Groom HC et al. Absence of xenotropic murine leukaemia virus-related virus in UK patients with chronic fatigue syndrome. Retrovirology 2010;7(1):10.
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