Virology:
Chronic Fatigue and Prostate Cancer: A Retroviral Connection?
Sam Kean
As if chronic fatigue syndrome (CFS) hasn't caused enough brawls, a new study published online by Science (
www.sciencemag.org/cgi/content/abstract/1179052) links the disease to a possibly contagious rodent retrovirus, XMRV, which has also been implicated in an aggressive form of prostate cancer. Related work by the authors also suggests that CFS might best be treated with AIDS drugs. Even the lead author, Judy Mikovits of the Whittemore Peterson Institute for Neuro-Immune Disease in Reno, Nevada, says she understands why linking CFS to a retrovirus and to prostate cancer has already drawn skepticism.
In 2006, an unrelated paper found an association between XMRV, which originated in mice, and a deadly prostate cancer exacerbated by a deficient enzyme. Mikovits and colleagues had seen the same deficiency in CFS cases. When they investigated further, the team discovered XMRV in the white blood cells of two-thirds of CFS patients but only 4% of control subjects. Intriguingly, Mikovits says XMRV does major damage in natural killer (NK) blood cells, which attack tumor cells and cells infected by viruses, and other studies suggest people with CFS suffer from high rates of cancer. Unpublished work, Mikovits adds, has found blood serum antibodies for XMRV in 95% of CFS patients.
All previous attempts to nail down a cause for CFSincluding many links to viral infectionshave foundered or been retracted, and many doctors remain doubtful that it's a coherent disease. Mikovits says her work "proves beyond a shadow of a doubt that CFS is a real disease." But some of her peers find the report of a viral link premature.
Joseph DeRisi, a molecular biologist at the University of California, San Francisco, who co-discovered XMRV, was not satisfied with details in the paper: He wanted to know more about the viral load in CFS patients and how the demographics of the control group matched that of CFS patients. And the Mikovits team didn't do enough to rule out contamination, he says. "One has to be very careful about making claims about such a sensitive and emotionally charged issue as CFS, where many claims have been made in the past." At the least, a double-blind study where a third-party lab searches for XMRV in CFS patients and in controls is vital, he says.
Other CFS specialists, including Jonathan Kerr at St. George's University of London, are convinced that the Mikovits team discovered something important. "The fact that the virus was actually grown from the blood cells of CFS patients strongly suggests some sort of role in the pathogenesis of the disease." But exactly what they discovered remains unclear, given that the group is not claiming to have identified a cause.
John Coffin, a molecular biologist at Tufts University in Boston, analyzed the Mikovits paper in a separate "Perspective" also published online by Science (
www.sciencemag.org/cgi/content/abstract/1181349). Coffin was highly skeptical of the paper at first, but the team found enough independent lines of evidence for XMRV to convert him. "They will be celebrating in the clinics where these people [with CFS] are being treated," he now says.
Even if the finding of a link to XMRV holds up, treatment suggestions are bound to attract controversy. No one knows how easily XMRV spreads, although Mikovits says transmission can occur via bodily fluids, including saliva. Mikovits also says unpublished preclinical data hints that scientists can treat XMRV with AIDS drugs such as AZT, although AZT itself might prove too toxic. Kerr remained cautious about this: "With present public knowledgewhat is described in this paperfurther work would be necessary before antiretroviral drugs could be recommended."