Researchers discover how West Nile virus triggers memory loss

June 22, 2016, CU Anschutz Medical Campus
Electron microscopy of West Nile virus. Credit: PhD Dre, Wikipedia/CC BY-SA 3.0

Researchers at the University of Colorado Anschutz Medical Campus have discovered how the most severe forms of West Nile virus cause memory loss and mood disorders, opening the door to potential new treatments for the mosquito-borne illness.

The study, published in the journal Nature, says 50 percent of patients who survive the most damaging kind of West Nile infection often go on to develop memory loss, learning difficulties, a lack of concentration and irritability.

Exactly why this happens has been a mystery until now.

Researchers discovered that the virus doesn't kill off neurons but sparks inflammation that prunes synapses, the connections that carry messages between nerve cells.

"What we found in mice, and later confirmed in humans, is that it's not the death of cells that causes , it's the loss of ," said study co-author Kenneth Tyler, MD, chairman of the department of neurology at the University of Colorado School of Medicine. "The viral infection activates microglial cells and complement pathways which are helping to fight the infection but in turn end up destroying synapses."

Bette K. DeMasters, MD, professor and head of neuropathology at CU Anschutz, also co-authored the study.

The researchers found that mice infected with West Nile had a difficult time negotiating their way out of a maze that healthy mice figured out much faster. They later discovered that the infected mice suffered significant damage to their synapses. The scientists examined brain tissue from humans who had died from West Nile and found the same phenomenon.

Tyler said West Nile is the leading cause of acute viral encephalitis in the U.S. though still relatively rare. Only about one in 100 people infected with the disease develop the most severe form, he said.

West Nile appeared in the U.S. during the late 1990s and has remained a persistent threat. Last year, California had 730 cases, Texas 252 cases and Colorado 101cases.

In Colorado, that number included 57 neuro-invasive cases, the most serious kind, and two deaths.

"This discovery opens up the opportunity to test therapies and medications on as a precursor to humans," Tyler said. "We already have some drugs that might be good candidates for treating this condition."

The best way to avoid West Nile is to wear long sleeves, use mosquito repellant and steer clear of standing water. The mosquito that carries the virus is most active at dusk and dawn.

Explore further: What is West Nile Virus?

More information: A complement-microglial axis drives synapse loss during virus-induced memory impairment, Nature, nature.com/articles/doi:10.1038/nature18283

Related Stories

What is West Nile Virus?

September 9, 2014
Late summer brings excitement about college football and hopes that the weather will soon cool off, but it also brings a risk for West Nile Virus, a common infection, but one that is not frequently diagnosed.

West Nile virus claims first victim in Kosovo

September 19, 2012
A woman had died of the mosquito-borne West Nile virus in Kosovo as two more patients were suspected of being infected with the disease, a health official said on Wednesday.

Three dead in Serbian West Nile virus outbreak

September 8, 2012
Three people have died in the first ever outbreak of the West Nile virus in Serbia, in which 35 contracted the disease, health authorities said Saturday.

One dead in Serbian West Nile virus outbreak

September 4, 2012
An outbreak of the West Nile virus in Serbia has killed an elderly woman and infected 20 other people with the mosquito-borne disease, health officials said Tuesday.

Worst year ever for West Nile in Texas; 40 dead

September 5, 2012
(AP)—Health officials say it's the worst year ever for West Nile in Texas, which has seen nearly half the country's deaths from the virus this year.

Recommended for you

Scientists gain new insight on how antibodies interact with widespread respiratory virus

February 22, 2018
Scientists have found and characterized the activity of four antibodies produced by the human immune system that target an important protein found in respiratory syncytial virus (RSV), according to new research published ...

Study reveals how kidney disease happens

February 22, 2018
Monash researchers have solved a mystery, revealing how certain immune cells work together to instigate autoimmune kidney disease.

Past encounters with the flu shape vaccine response

February 20, 2018
New research on why the influenza vaccine was only modestly effective in recent years shows that immune history with the flu influences a person's response to the vaccine.

Building better tiny kidneys to test drugs and help people avoid dialysis

February 16, 2018
A free online kidney atlas built by USC researchers empowers stem cell scientists everywhere to generate more human-like tiny kidneys for testing new drugs and creating renal replacement therapies.

Expanding Hepatitis C testing to all adults is cost-effective and improves outcomes

February 16, 2018
According to a new study, screening all adults for hepatitis C (HCV) is a cost-effective way to improve clinical outcomes of HCV and identify more infected people compared to current recommendations. Using a simulation model, ...

Study suggests expanded range for emerging tick-borne disease

February 16, 2018
Human cases of Borrelia miyamotoi, a tick-borne infection with some similarities to Lyme disease, were discovered in the eastern United States less than a decade ago. Now new research led by the Yale School of Public Health ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

orlinbobchev
not rated yet Jun 23, 2016
I am really interested in the drug candidates.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.