Delineation of the origin of the retrovirus known as XMRV from the genomes of laboratory mice indicates that the virus is unlikely to be responsible for either prostate cancer or chronic fatigue syndrome in humans, as has been widely published. The virus arose because of genetic recombination of two mouse viruses. Subsequent infection of lab experiments with XMRV formed the basis of the original association.
Reporting in Science, Vinay Pathak, Ph.D., and his research team from the National Cancer Institute (NCI), part of the National Institutes of Health, in collaboration with other researchers, described experiments that provide an understanding of when and how XMRV arose and explain the original, incorrect association. XMRV stands for xenotropic murine leukemia virusrelated virus.
This study is being reported in the same issue of Science as another study of XMRV (Knox et al.) that finds a lack of association between the virus and CFS even in the same patients from a 2009 study. "Taken together, these results essentially close the door on XMRV as a cause of human disease," said John Coffin, Ph.D., special advisor to the NCI director, and professor at Tufts University School of Medicine, a coauthor of the paper with Pathak.
Murine leukemia viruses are retroviruses that cause cancers and other diseases in mice. They are divided into different classes, one of which is xenotropic murine leukemia viruses. Although viruses in this class cannot grow in or infect cells from most mice, in the laboratory they can infect cells from other species, including human cells.
XMRV was first reported in samples from a human prostate tumor in 2006, and has been reported to be present in 6 percent to 27 percent of human prostate cancers. Later research reported XMRV in the blood of 67 percent of people with CFS.
The assertion that XMRV is circulating in the human population has been challenged by several studies t
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