Science: Retrovirus Detected In Patients With Chronic Fatigue Syndrome—But Does It Cause the Disease?

Electron micrograph of xenotropic murine leukemia virus-related virus (XMRV) as detected in the blood of a chronic fatigue syndrome (CFS) patient. XMRV was discovered in blood of known CFS patients by a team of scientists from the Whittemore Peterson Institute, the National Cancer Institute, and the Cleveland Clinic Foundation.

[Image courtesy of the Whittemore Peterson Institute]

As many as two-thirds of patients with chronic fatigue syndrome carry an infectious retrovirus in their blood cells, according to new research published in Science. But the study's authors say it's not clear whether the virus is the main cause or a co-conspirator in the disorder.

Chronic fatigue syndrome (CFS) affects 17 million people worldwide, attacking multiple organs and often disrupting the body's immune system. CFS's exact cause or causes are still unknown, but a number of researchers have suggested that a viral infection could be a potent trigger for the disease.

So when the retrovirus XMRV was discovered in human prostate tumors, Vincent Lombardi of the Whittemore Peterson Institute and colleagues decided to examine patients with CFS to see if the retrovirus might be lodged in their cells as well. They uncovered XMRV in 68 of 101 blood samples from people with CFS, while finding the virus in only eight of 218 samples taken from healthy patients.

The retrovirus can infect other cells and provoke an immune response, but there is no evidence yet that the virus is the cause of the disease. Since many people with CFS have compromised immune systems, the researchers noted, XMRV may simply be a “passenger virus” that has managed to breach the body's weakened defenses.

In a Perspective article related to the study, John M. Coffin and Jonathan Stoye discuss how similar retroviruses cause cancer and neurological diseases in animals from mice to koalas. XMRV's surprising prevalence among healthy people—nearly 4% of those examined in the Lombardi study—could mean that “hundreds of millions of people worldwide are infected with a virus whose pathogenic potential for humans is still unclear,” they conclude.

Becky Ham

8 October 2009