Five years ago, a retrovirus resembling a murine leukemia virus (MLV) was found in patients with prostate cancer (1), and last year, a similar gammaretrovirus was identified in patients with chronic fatigue syndrome (CFS) (2). The agent was named xenotropic MLV-related virus (XMRV), because its env gene was nearly identical to that of xenotropic MLV, an infectious endogenous MLV that preferentially infects cells from foreign species, including humans (Fig. 1A) (3). The two reports struck a common chord, because the viral sequences found in prostate cancer and CFS were nearly identical. A second common theme emerged in reports from Europe that XMRV was rarely found, if at all, in prostate-cancer samples or patients with CFS; however, other investigators confirmed the presence of XMRV in prostate-cancer samples from North America (4). Although a recent report from the Centers for Disease Control and Prevention (CDC) did not find a link between XMRV and CFS (5), distinct MLV-related sequences are found in serial samples collected from the mid-1990s to 2010 from patients with CFS reported in the study by Lo et al. (6) in PNAS. However, the reasons for the current geographical restriction and the source of the infection are baffling.
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Comment on: Detection of MLV-related virus gene sequences in blood of patients with chronic fatigue syndrome and healthy blood donors. [Proc Natl Acad Sci U S A. 2010]
Source: Courgnaud V1, Battini JL, Sitbon M, Mason AL. Mouse retroviruses and chronic fatigue syndrome: Does X (or P) mark the spot? Proc Natl Acad Sci U S A. 2010 Sep 7;107(36):15666-7. doi: 10.1073/pnas.1007944107. Epub 2010 Aug 23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2936611/ (Full article)