The ALS Association

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Carrie Munk
The ALS Association
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A Retrovirus is Toxic and is Elevated in Some ALS Cases, Study Shows

Washington, D.C. (October 2, 2015) — Some cases of ALS may be linked to a human retrovirus, according to a new study showing that the level of the virus is increased in some people with ALS, and that the virus can be toxic to motor neurons.

ALS is a progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord. Eventually, people with ALS lose the ability to initiate and control muscle movement, which often leads to total paralysis and death within two to five years of diagnosis. For unknown reasons, veterans are twice as likely to develop ALS as the general population. There is no cure, and only one drug approved by the U.S. Food and Drug Administration (FDA) modestly extends survival.

The study looked at human endogenous retrovirus K (HERV-K), an ancient virus which, over human evolution, has become copied and inserted in many places in the genomes of every human. Most copies of the virus are silent and do not reproduce. The study researchers, including Wenxue Li, Ph.D., and Avindra Nath, M.D., of the National Institute of Neurologic Disorders and Stroke, showed that the level of active virus was higher in the central nervous systems of a small sample of people who had died of sporadic ALS, compared to people without the disease. Working in cell culture and animals, they showed that increasing the amount of a HERV-K coat protein was specifically toxic to motor neurons. They also showed that the viral DNA sequence is a target for TDP-43 protein, a protein that appears to play a role in the ALS disease process.

“The results of this study suggest that this virus could play a role in some cases of sporadic ALS,” said Lucie Bruijn, Ph.D., M.B.A., Chief Scientist for The ALS Association. “If that is the case, it may be beneficial to explore whether antiviral treatments could be therapeutic. However, there is still much we don’t know about the link between the virus in this study and sporadic ALS, including whether the virus is truly contributing to the disease, or whether its elevation instead is a consequence of the disease process.”

Dr. Bruijn also noted that while the virus implicated in this study is a retrovirus, there is no link between ALS and another retrovirus, HIV, which causes AIDS.

The study’s findings were published in Science Translational Medicine:

About The ALS Association
The ALS Association is the only national non-profit organization fighting Lou Gehrig’s Disease on every front. By leading the way in global research, providing assistance for people with ALS through a nationwide network of chapters, coordinating multidisciplinary care through certified clinical care centers, and fostering government partnerships, The Association builds hope and enhances quality of life while aggressively searching for new treatments and a cure. For more information about The ALS Association, visit our website at

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