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Mouse models show how Zika infects a fetus during pregnancy

Researchers at Washington University in St. Louis (WashU) have established the first models of Zika virus transmission from a pregnant mouse to her fetus. The infected mice, described in Cell, demonstrate Zika virus invasion and damage to the placenta, and then infection of the mouse fetus, leading to many of the same conditions observed in human infants. The new mouse models can also be used as a tool to develop treatments or vaccines.

“There have been questions regarding whether in utero transmission of Zika virus actually causes disease in the fetus. While the evidence has been mounting, our data confirms that Zika virus can cause congenital problems, including fetal death,” says Michael Diamond, a viral immunologist at WashU.

Creating even a general mouse model of Zika virus infection has been a challenge because mice aren’t normally susceptible to the virus. To get around the animals’ immune defenses and study viral transmission during pregnancy, Diamond and his colleagues, including post-doctoral fellow Jonathan Miner, developed two models. In one, the female mice were genetically wired to have a defective immune system, creating a model of severe disease when infected with Zika. In the second model, the female mice were genetically normal, but received injections of an antibody that partially prevented their immune systems from functioning.

fluorescent image shows the Zika virus inside a trophoblast
This fluorescent image shows the Zika virus (green) inside a trophoblast (nuclei labeled in red)
Image Credit: Bin Cao