Researchers Find Positive Evidence Zika Causes Fetal Brain Defects

A new study conducted in a lab with cell cultures is more evidence the Zika virus slows down and stop neural cell growth. REUTERS/Nacho Doce

A group of researchers say they've taken a critical step in proving the Zika virus is most likely the cause of a rising number of microcephaly cases in Brazil. An investigation conducted on lab cultures, led by Hengli Tang, a professor of biological science at Florida State University, has shown that the virus destroys certain brain cells, which leads to serious birth defects.

To conduct the study, the team grew the Zika virus in mosquito cells and then infected certain human brain stem cells, called cortical neural progenitors, with the viral mosquito cells. Tang said it only took three days for the infection to spread to the whole culture dish. Shortly after that, Tang and his team—in collaboration with researchers at Johns Hopkins University and Emory University—found several changes to the stem cells that appear to be consistent with the pathological features of microcephaly.

"We found the cell's growth was slowed down and we found some defects in cell cycle progression," says Tang. Additionally, they found the virus replicates using this type of cell.

Tang and his team have for some time studied dengue fever, another mosquito-borne virus that is in the same category as Zika. His colleagues at Johns Hopkins University were already growing the neural stem cells, while the team at Emory had the resources to conduct RNA sequencing of the cultures. But this particular project has really only just begun; the investigation was launched in January.

Meanwhile, in Brazil, the outbreak of the Zika virus appears to match the trend of a growing number of infants born with microcephaly, a condition in which a baby has an abnormally small skull and incomplete brain development. Physicians and researchers have found evidence of the virus in amniotic fluid, cord blood, placenta and tissue samples of stillborns. But experts say a handful of case reports aren't enough to state definitively that the Zika virus is the cause behind Brazil's more than 4,000 cases of microcephaly in the country.

Likewise, Tang says that while his team's findings do demonstrate a high possibility that there is a causal link, it is not positive proof. However, he does believe this preliminary research will be useful to scientists studying the Zika-microcephaly link in humans since it provides information on which types of neural cells to study.

Next the team, hopes to conduct similar studies on brain organoids, as well as a more extensive investigation of why the virus targets this type of neural cell.