Much thorough hunt for a mouse retrovirus called XMRV in people who have chronic fatigue syndrome (CFS ) -including in patients who tested positive for the virus in other laboratories, came away empty, further deflating the hope that the cause of this puzzling disease has been found. "I urge people to spend rather than keeping their hopes hung on the link between XMRV and CFS," says Ila Singh, a virologist at the University of Utah in Salt Lake City, who led the new study.
the link between XMRV, which means the virus named imperfectly linked to the virus murine leukemia xenotropic and CFS has sparked debate since it was first reported in a study published online 8 October issue Science 09 . Singh's study is the latest of several that have failed to find XMRV in CFS patients. It is also the first to analyze samples from patients who were part of the original study. as Singh and colleagues reported online in the May 4 Journal of Virology , they analyzed blood samples from 100 CFS patients, including 14 who tested positive in Science Report and 0 healthy controls. The team looked for evidence of XMRV in many ways, including fishing for viral sequences with the ultrasensitive PCR test, trying to develop an infectious virus in cell cultures, and scrub the blood of antibodies directed against viral proteins . (Anterior XMRV was linked to prostate cancer, the current study does not address Singh this link.)
"Singh leaned back to try to use the same tests as published, allowing him dropping what I consider to be a true man of straw, but that was still there, "said retrovirologist John Coffin of Tufts University in Medford, Massachusetts. Coffin initially supported the Science report, but then concluded, along with many others, that XMRV is a contaminant. In a recent study, it has provided evidence that the virus accidentally origin in mouse laboratory experiments.
Singh said she and her colleagues also had contamination problems. When we used a PCR test that was used in the original report Science , they found 5% of both CFS and control samples tested positive for XMRV. "He was very confused until we thought it was contamination," says Singh. Specifically, they pointed to a PCR reagent, the enzyme Taq polymerase, as the source of the sequences of the mice, they detected. they also found that one of the machines they used to test samples were also contaminated with XMRV in studies they had done months before the current analysis. "All the world working with mice a mouse retrovirus contamination in the lab, "said Coffin." I have probably in my pool house. "
The lead author of the disputed Science paper retrovirologist Judy Mikovits of the Whittemore Peterson Institute for Neuro-Immune Disease in Reno, Nevada, does not convince the inability of Singh group to detect any XMRV. "I'm amazed when I leaned that Ila [Singh] has not," said Mikovits. "These are good scientists."
Mikovits said she is confident that the 14 CFS patients she selected for the Singh group have XMRV in their bodies. "These people are infected," says Mikovits. "This study says nothing. We have confidence in all the bits of the results in Science paper. We do not think this is wrong. There is no evidence of contamination in our lab, and we are commanded that all along. "
Mikovits Singh noted that the group did not use the same protocols for each analysis, and stresses that the differences between their labs may also reflect his own conclusion that the levels vary XMRV in patients daily . Singh contends that although some differences protocols exist, they worked closely with the team Mikovits to reproduce the original work. Singh said the fact they do not find XMRV in any of these patients is important. "She [Mikovits] we made towards patients she had repeatedly tested positive," Singh said. "We would have found at least one that was positive. Not all of them went negative on the day a phlebotomist meeting with them. "
Mikovits warns that his Science report did not state that XMRV causes CFS but only claimed to have detected XMRV in CFS patients. But the great community of CFS patients, who are often faced with a medical institution that challenges the very existence of their disease, pounced on this finding, and some even began taking antiretroviral medications to treat their XMRV infections assumed.
laboratory Singh previously reported that antiretroviral drugs only work against XMRV in test tube studies. But it sets now guard CFS patients that their decision is unjustified and even dangerous.
XMRV saga is far from over. Unlike Coffin and many other skeptics, Singh argues that similar to XMRV virus does infect the man, and his own work supports prostate cancer connection. "There is still a lot of data supporting the link with prostate cancer that can not be easily explained by contamination," she said. "More work needs to be done before this matter can be resolved."
the question whether XMRV infects humans and is linked to the promises of the disease to come to a head later this year, when two different studies sponsored by the US National Institutes of Health are completed. the studies involve both Mikovits and several other independent laboratories test the same samples. Mikovits said if all samples in these studies are negative, including in his own laboratory, the day might come when she changes her mind. "But I do think that to get to this day, "she said.
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