Zika virus can 'wreak havoc' on adult’s memory – study

A lab technician works at the "microinjection area" inside Sun Yat-Sen University-Michigan State University Joint Center of Vector Control for Tropical Disease, Guangzhou, China. © Bobby Yip
Much of the focus around the mosquito-borne Zika virus has been on pregnant women and brain abnormalities in fetuses, but now scientists think some adult brain cells could be vulnerable too. Infections may even be as destructive as Alzheimer’s disease.

By engineering mice to mimic the human Zika infection, and using fluorescent biomarkers to tag infection sites, scientists at the Rockefeller University and La Jolla Institute for Allergy and Immunology found that adult neural progenitor cells could be hijacked by the virus, leading to brain shrinkage and mental impairment.

“Our results are pretty dramatic – in the parts of the brain that lit up, it was like a Christmas tree,” said Professor Joseph Gleeson, head of Laboratory of Pediatric Brain Disease at The Rockefeller University, in a released statement about the new study. “It was very clear that the virus wasn't affecting the whole brain evenly, like people are seeing in the fetus.”

Gleeson said in healthy individuals, neural progenitor cells become fully formed neurons and are resistant to Zika, but for some people with weakened immune systems, they may be vulnerable to the virus.

The mature brain, Gleeson said, is learning, and memory that is impacted by Zika could bring about a cognitive decline that is normally associated with Alzheimer's disease or depression.

“In the adult, it's only these two populations that are very specific to the stem cells that are affected by virus. These cells are special, and somehow very susceptible to the infection,” Gleeson said. “Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think.”

Scientists still do not know to what extent the mouse model results apply to humans, or how permanent the brain damage is.

“Zika can clearly enter the brain of adults and can wreck havoc,” said Sujan Shresta, a professor at the La Jolla Institute of Allergy and Immunology. “But it’s a complex disease. It’s catastrophic for early brain development, yet the majority of adults who are infected with Zika rarely show detectable symptoms. Its effect on the adult brain may be more subtle, and now we know what to look for.”

But scientists said it raises the disturbing possibility of long term mental impairment in Zika-infected adults.

“The virus seems to be travelling quite a bit as people move around the world,” said Gleeson. “Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women.”

The epicenter of the current Zika epidemic is Brazil, where the Olympic Games are in full swing in Rio de Janeiro.

In February, the World Health Organization declared the outbreak a “public health emergency of international concern,” as evidence grew of Zika's association with birth defects.

The virus is chiefly spread by the Aedes aegypti mosquito, which is common throughout the tropical and subtropical Americas.

The new findings were published in Cell Stem Cell on August 18.