Just one in 10 babies exposed to the Zika virus during pregnancy get the brain damage that causes microcephaly聽鈥撀燼bnormally small heads. Now there鈥檚 a first clue about what stops this from happening in the rest 鈥� their gene activity.
Blood samples were taken from three pairs of non-identical twins in Brazil. In each of these pairs, one baby had brain damage and the other didn鈥檛. Stem cells were then made from their blood cells, and matured into brain cells, allowing researchers to see how the brain cells naturally differ between the twins.
They found that, in the babies that developed microcephaly, the brain cells seem to innately make less of three particular proteins. The genes that encode these proteins are all known to be involved in normal neural development.
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When the team exposed these brain cells to Zika virus, they were also more susceptible to infection than ones made from the blood of their twins.
Spreading to the US
It may be possible to use this finding to develop a test for pregnant women that will tell them if their fetuses are particularly susceptible to Zika infection and microcephaly, says of the University of S茫o Paulo in Brazil.
Zika began causing an epidemic of brain damage in South America after it spread to the continent from Asia in 2013. But cases in Brazil dropped sharply last year, perhaps because most people there are now immune.
The virus has now spread to the most southerly parts of the US, with some areas seeing about a in the second half of 2016, the Centers for Disease Control and Prevention reported last week.
