From Retrovirology, 22 February 2011.
Short report
Serologic and PCR testing of persons with chronic fatigue syndrome in the United States shows no association with xenotropic or polytropic murine leukemia virus-related viruses
Brent C. Satterfield , Rebecca A. Garcia , Hongwei Jia , Shaohua Tang , HaoQiang Zheng and William M. Switzer
Retrovirology 2011, 8:12doi:10.1186/1742-4690-8-12
Published: 22 February 2011
Abstract (provisional)
In 2009, a newly discovered human retrovirus, xenotropic murine leukemia virus (MuLV)-related virus (XMRV), was reported by Lombardi et al. in 67% of persons from the US with chronic fatigue syndrome (CFS) by PCR detection of gag sequences. Although six subsequent studies have been negative for XMRV, CFS was defined more broadly using only the CDC or Oxford criteria and samples from the US were limited in geographic diversity, both potentially reducing the chances of identifying XMRV positive CFS cases. A seventh study recently found polytropic MuLV sequences, but not XMRV, in a high proportion of persons with CFS. Here we tested blood specimens from 45 CFS cases and 42 persons without CFS from over 20 states in the United States for both XMRV and MuLV. The majority of CFS patients (31/45, 69%) had a minimum of 6 months of post-exertional malaise and a high degree of disability, the same key symptoms described in the Lombardi et al. study. Using highly sensitive and generic DNA and RNA PCR tests, and a new Western blot assay employing purified whole XMRV as antigen, we found no evidence of XMRV or MuLV in all 45 CFS cases and in the 42 persons without CFS. Our findings, together with previous negative reports, do not suggest an association of XMRV or MuLV in the majority of CFS cases.
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Danielson et al. used the same assay and proved that it does not work when calibrated to detect VP62 clone in a spiked sample. It didn’t matter how much DNA was used. This was used on the new CFS cohort.
Also, they could not get any assay based on the pol gene to work because of competition with human DNA sequences.
The RT-PCR assay to detect XMRV in plasma is untested. The origin of the plasma is not known.
They isolated RNA from 62ul of plasma and use 0.25ul of cDNA in their RT assay. The likelyhood of even one viral sequence being present was negligable
They then use a serology assay which has been shown to be 400% less sensitive than PCR in detecting XMRV antibodies in the blood of healthy people (qui et al.)
Pol 1 assay cycling conditions were used in last negative study by sattersfield (ref 14)
Pol 2 cycling conditions used by Switzer et al. in 2010, which could not detect XMRV in known positive in the Blood Working Group(ref9)
Gag 0.25 ug of DNA isolated from 0.62ul plasma using cycling conditions used in Switzer et al. 2010, which could not detect XMRV in DNA isolated from 2 x105 PMBC cells(ref 9)
Patients were recruited via an one line survey from primary care, and there was no objective evidence that they had PEM. They were not assessed by a specialist physician, nor did the patients satisfy the CCC criteria.