London, Apr 12 (IANS): In a first, Brazilian researchers have demonstrated the harmful effects of Zika virus on human brain, revealing that the virus reduces growth and induces cell death and malformations in neural stem cells.

Zika virus has been associated with a birth defect called microcephaly that causes brain damage and an abnormally small head in babies born to mothers infected during pregnancy.

"Since the virus has been gradually established as a direct cause of central nervous system malformations, this study helps elucidate the etiological nature of the recently increasing number of microcephaly cases in Brazil," the authors noted in a paper that appeared in the journal Science.

Scientists headed by Dr Stevens Rehen from the D'Or Institute for Research and Education (IDOR) and Federal University of Rio de Janeiro (UFRJ) differentiated human induced pluripotent stem (iPS) cells into neural stem cells, neurospheres and brain organoids.

Neurospheres and brain organoids represent excellent models to investigate developmental neuropathologies as they can outline, in vitro, several characteristics of the fetal brain formation.

The research team observed that the virus infects human-derived iPS neural cells, neurospheres and cerebral organoids causing cell death, malformations and reducing growth by 40 percent.

The researchers also compared these results with the ones generated with dengue virus.

Even though dengue virus infected the cells such as Zika virus, there were no damaging outcomes registered to the neural cells, neurospheres or organoids.

"These unique results may unravel some key features of Zika virus infection in the developing brain," said Dr Patricia Garcez, assistant professor at UFRJ and first author of the work.

Zika virus is a mosquito-borne disease that has been reported in 33 countries.

It also has been associated with the autoimmune disease Guillain-Barre syndrome, which can lead to temporary paralysis.