Zika targets fetus' developing brain cells, study shows

TALLAHASSEE — Four professors have uncovered evidence that the Zika virus specifically targets developing brain cells, leading to stunted brain development.

Their findings, which eventually could identify drugs that treat the virus when it first infects, were published Friday in the scientific journal Cell Stem Cell. They found that the virus affects neural stem cells, which develop into much of the nervous system in fetuses, slowing their growth.

“It’s significant because we’re literally the first people in the world to know this, to know that this virus can infect these very important cells and interfere with their function,” said Hengli Tang, a Florida State University biology professor. “Research is rewarding in general, but when you have something this timely and this clinically relevant, it’s extra satisfying because we’ll be helping people in the long run.”

Tang is lead author of the study. His co-authors are Guo-li Ming and Hongjun Song, both neuroscientists at Johns Hopkins University School of Medicine in Baltimore, and Peng Jin, a geneticist at Emory University Hospital in Atlanta.

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Cell Stem Cell, based in Cambridge, Mass., publishes research around the world related to stem-cell science.

Researchers found the virus targets a cell type called human embryonic cortical neural progenitors in as little as three days after being exposed to the virus. They also discovered that those infected cells replicate the Zika virus, posing potential treatment problems, and that the virus is directly interfering with cell growth and function.

“We answered some specific questions about the cell type the virus can infect and also the potential effect the virus has on these cells,” Tang said. “This enables drug screening in these important cells. By targeting the very cells that are important for brain development, the Zika virus can directly affect brain development."

Doctors have suspected that the virus can lead to a condition called microcephaly, which causes babies to be born with unusually small heads and improperly developed brains.

“This is a very short study," he said. "The follow-up is a long-term study to determine the long-term effect on brain development.”

The research did not identify how the virus is transmitted to the brain, Tang said.

Florida leads other states in reports of people infected with the Zika virus. As of Thursday, three new cases were reported in Miami-Dade County, bringing the state total to 47 with 22 in Miami-Dade.

On Feb. 3, Dr. John Armstrong, Florida's state surgeon general and secretary of the state Department of Health, declared a public health emergency for the 11 Florida counties where cases have been confirmed.

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Health officials are particularly concerned about pregnant women.

Brazil and other South American countries hard hit by Zika also have seen a dramatic increase in microcephaly. The World Health Organization has declared an international public health emergency.

“It was a little known virus prior to the World Health Organization public health emergency,” Tang said. Zika virus first was identified in 1947, but concerns have escalated because of an increase in cases of microcephaly, which generally occurs in 2 to 12 babies out of 10,000 born in the United States.

The virus is very similar to dengue, which is included in Tang's research financed by the National Institutes of Health, he said. Both viruses are transmitted through mosquito bites and have been found in tropical areas such as South America and the Caribbean.

“Because we were studying a similar virus and the World Health Organization declared a public health emergency, we started studying it (Zika), just last month,” he said.

Tang said he reached out to Johns Hopkins University’s School of Medicine colleagues who have expertise in brain development. Emory University School of Medicine researchers were brought on board because of their previous research collaborations with Johns Hopkins.

“The collaboration between us, who study the Zika virus and those two labs was the right combination to study any potential effect of Zika on brain development,” said Tang who attended graduate with the two Johns Hopkins University neuroscientists. “We didn’t waste any time. We worked quickly.”

Florida State already had the virus stored in its lab, Tang said. A research team from Johns Hopkins visited last month, bringing neural stem cells.

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Tang infected them with Zika. His team then sent the infected cells to Emory, where they were evaluated.

Some of the cells died after being infected.

This could be a critical finding, said Ming, the Johns Hopkins neuroscientist.

“Potentially, this could explain why there is a link to microcephaly, but there is a lot more work needed to show the direct causal effect,” she said. “The significance is we provide the first biological evidence that Zika can infect neural stem cells very efficiently. We can speculate that it will spread in the brain.”

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The goal was to find or disprove any link, Tang said.

“Our data is consistent and it supports that hypothesis, but it is not definitive proof,” he said, agreeing that more research must be conducted. “We are adding critical information to build the case, but the case is still being built.

The next steps include screening for drugs that will block the virus or be used for treatment and further study to determine the long-term effect of the virus on neural stem cells and brain development, Tang said.

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The goal is to find a way to stop its effects.

“We hope this will open up more research,” Tang said. “This information will be of interest not just to scientists but to government agencies and clinicians, for sure, and the general public.”

Follow Byron Dobson on Twitter: @byrondobson

Areas across the USA with reported Zika cases

In the United States, 153 cases of Zika virus disease have been reported from Jan. 1 to Wednesday. All were in people who had traveled to areas where mosquitoes that carry Zika are prominent. In U.S. territories, the causes are reversed: 107 cases were acquired locally and one came from travel to another area.

Source: Centers for Disease Control and Prevention

About Zika

The virus generally causes a mild illness, and some people do not know they are infected.

Symptoms of Zika may include low-grade fever, rash, joint pain, pink eye, body aches, headache, eye pain and vomiting.

The virus has no treatment and symptoms generally end within a week.

Avoiding mosquito bites in tropical areas is the best way to prevent Zika:

• Use mosquito repellent applied to bare skin or clothing.
• Cover skin with long-sleeved shirts and long pants.
• Apply a permethrin repellent directly to clothing or purchase pre-treated clothing. Do not apply directly to the skin.
• Choose lodging with air conditioning or screens on windows and doors.
• Sleep under a mosquito bed net when outside or in an unscreened room.

Source: Florida Department of Health