Study: Zika virus targets fetus brain cells

Researchers caution the results may not translate outside of the lab

A new study suggests that Zika virus may destroy cells in the brain cortex of developing fetuses.

The study, published in Cell Stem Cell on Friday, may explain why some infants who contract the virus in-utero are born with microcephaly, a rare neurological condition characterized by an unusually small head and incomplete brain development.

WHO: Zika virus 'spreading explosively' in the Americas

For the study, researchers exposed neural stem cells to the virus in laboratory dishes. Within three days, the dishes became "virus factories" for Zika, and the cells died more quickly than normal, the researchers said.

Hengli Tang, the lead author of the study and a professor at Florida State University, says the study shows the virus can affect "very important cells" in the brain. Study co-author Hongjun Song, a professor at Johns Hopkins University School of Medicine, says the cells that form the cortex were "the target of the virus."

But Tang cautions that the study doesn't show that Zika actually reaches of the brain cells of Zika-infected fetuses. What it does show, he says, is that the virus can "do a lot of damage" if it reaches the cortex.

Context for the findings

Independent experts praised the research as an important step toward understanding how the virus may cause harm, but also cautioned it was far from conclusive. "This paper points to a mechanism that's plausible and makes sense," explains Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. "It gives us a clue as to why the virus inhibits the brain growth of a fetus."

On Zika's trail in Brazil

Zika is strongly suspected to cause microcephaly, but the link is not yet proven. Brazil, a major epicenter of the Zika outbreak, has confirmed 640 cases in recent months—with more than 4,000 suspected cases overall.  

The study bolsters the case for a connection between Zika and microcephaly, and some officials are confident the link is real. Lyle Petersen, director of the division of vector-borne diseases at CDC CDC, says, "I don't think there is any question about [a link] any longer."  

However, Catherine Spong, the acting director of the National Institute of Child Health and Human Development, notes that the study involved examining Zika's effects on cell cultures in a lab—which may be different that its effect in the outside world.

Researchers tell the New York Times that a World Health Organization (WHO) study of about 5,000 pregnant women who were infected with Zika early in their pregnancies likely will provide more definitive information about the link between the virus and microcephaly. WHO says the results will be avaliable in June at the earliest (Saint Louis, New York Times, 2/4; Sun/Dennis, "To Your Health," Washington Post, 3/4; Seaman, Reuters, 3/4).

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