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Chronic Fatigue Syndrome Linked to Infectious Retrovirus XMRV

Two-thirds of patients with chronic fatigue syndrome were found to carry a retrovirus known as xenotropic murine leukemia virus-related virus (XMRV) in their peripheral blood cells, compared with just 4% of unaffected individuals, according to a report in the October 8, 2009 advance online edition of Science. If further research confirms that XMRV contributes to CFS, antiretroviral drugs may one day be used to treat the condition.

Chronic fatigue syndrome, is characterized by a variety of symptoms including debilitating exhaustion and chronic pain. Its cause is poorly understood -- it has been attributed to everything from to chemical sensitivities to chronic Lyme disease to psychosomatic illness -- though it is increasingly recognized as being associated with immune dysfunction. Many patients have been frustrated by the lack of a clear cause or definitive treatment, and the suggestion that it's "all in their head."

In the present study, Vincent Lombardi and colleagues examined peripheral blood mononuclear cells (PBMCs) -- immune cells such as T-cells and B-cells -- from about 100 patients with CFS and 200 healthy control subjects. They found that cells from 68 of 101 CFS patients (67%) harbored DNA from XMVR, compared with just 8 of 218 unaffected individuals (3.7%).

The researchers further determined in cell culture experiments that XMRV derived from patients' cells was infectious, and could be transmitted through both cell-associated and cell-free transmission methods. They observed secondary XMRV infections in initially uninfected lymphocytes from healthy subjects after exposure to activated T-cells, B-cells, or plasma from CFS patients.

XMRV is classified as a human gammaretrovirus. Like HIV (a lentivirus), it is part of the same broad family of family of retroviruses -- viruses that use the reverse transcriptase enzyme to convert their genetic material from RNA to DNA -- but it is more closely related to a group of viruses that cause cancers such as leukemia. Another recent study linked XMRV to prostate cancer.

In conclusion, the study authors wrote, "These findings raise the possibility that XMRV may be a contributing factor in the pathogenesis of CFS." The results also help explain the observed tendency of chronic fatigue to affect multiple members of social networks.

If further studies confirm that this is the case -- which would be a paradigm shift similar to the discovery that bacteria, not psychological stress, is the primary cause of gastric ulcers -- antiretroviral agents (though not necessarily those now used against HIV) may some day play a role in CFS treatment.

Reference

V Lombardi, FW Ruscetti, J Das Gupta, and others. Detection of an Infectious Retrovirus, XMRV, in Blood Cells of Patients with Chronic Fatigue Syndrome. Science. October 8, 2009 (epub ahead of print). (Abstract).

Other source

K Harmon. Retrovirus Linked to Chronic Fatigue Syndrome, Could Aid in Diagnosis. Scientific American online. October 18, 2009.

B Ham (AAAS). Science: Retrovirus Detected In Patients With Chronic Fatigue Syndrome-But Does It Cause the Disease?News release. October 8, 2009.