Zika attacks and destroys human brain cells development, demonstrated in laboratory researchers, establishing the first scientific evidence of a link between the virus and the fetal microcephaly, according to research published on Friday .
Hitherto, the relationship of cause and effect had not been scientifically proven. The virus, however, was strongly suspected of being behind many cases of microcephaly, observed particularly in Brazil where the epidemic exploded.
This malformation, severe and irreversible, characterized by an abnormally small skull and brains of newborns. The researchers worked with human stem cells grown in vitro, and the result was published in the journal Cell Stem Cell .
Destruction of neuronal cells progenitor
They determined that the virus selectively infects the stem cells that form the cerebral cortex preventing them from dividing normally to form new cells resulting in their destruction.
“Studies in fetuses and newborns suffering from microcephaly in geographic areas affected by the infection of Zika had revealed abnormalities in the cortex and the virus was also found in fetal tissue, “noted in a statement Guo-li Ming, professor of neurology at the Institute for cell engineering at Johns Hopkins University in Maryland, co-author of the study.
For these experiments, scientists exposed three types of human cells to Zika virus. The first, called neural progenitor cells, are critical to the development of the cerebral cortex of the fetus. Damage caused by Zika virus to these cells, which are differentiating to become neurons, correspond to the defects observed in the brain resulting in microcephaly, researchers found these. The other two types of cells exposed to Zika in this experiment are stem cells and neurons.
As expected, the Zika virus attacked human progenitor neuronal cells and after three days, 90% were infected and nearly a third were destroyed. Some infected cells were also used by Zika to produce new copies of itself. In addition, genes that normally are mobilizing to combat viral agents invaders did not work which is very unusual, say these scientists.
In contrast, the other two types of human cells tested in this laboratory experiment (stem cells and neurons) have largely been spared the Zika virus.
583 cases of microcephaly in Brazil
“Our results clearly show that Zika can directly infect human neuronal progenitor cells in vitro … with high efficiency,” the study concludes.
“Now that we know how these neural cells forming the cerebral cortex are vulnerable to Zika, they could also be used for rapid screening of the infection and the development of potential new therapies,” says Hongjun Song , also a researcher at the Institute for Cell Engineering and co-author of the study.
Outside the fetus, Zika himself, most often transmitted through the bite of a mosquito, does not present a danger, causing the worst cold symptoms or mild flu, passing sometimes unnoticed. But with its rapid spread in more than forty countries, especially South America and the Caribbean, it is suspected to be responsible for the unusually high number of cases of microcephaly and other severe syndromes, especially syndrome Guillain-Barré syndrome, which attacks the nervous system.
To date in Brazil, the country most affected by the epidemic, 583 cases of microcephaly were confirmed in October 2015, four times the historical annual average. Friday, Colombia scientists announced the first case of microcephaly linked to Zika, according to British magazine Nature .
“Many other necessary research”
the result of the study the two researchers was welcomed by many scientists.
“This is a big step in the right direction,” Judge Mark Schleiss, Director of the Division of Infectious Diseases and Immunology at the University of Minnesota.
“Much more research is needed to understand the link between Zika and microcephaly”, however believes Amelia Pinto, molecular microbiology professor at the University St Louis (Missouri).
The virus is spread mainly by mosquitoes but recent cases also suggest sexual transmission.