UCSD Professor Finds Causal Link Between the Zika Virus and Microcephaly


Photo courtesy of Dr. Alysson Muotri.

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Dr. Alysson Muotri, associate professor in the Department of Pediatrics/Cellular and Molecular Medicine at UCSD, and his lab recently found a causal link between the Zika virus and microcephaly. Microcephaly is a condition where the brain doesn’t develop normally, often leading to smaller than average head size.

Prior to the study, there was no direct evidence that the virus was responsible for causing the condition. “People were blaming pesticides and other potential factors that were associated with the Zika virus” explained Dr. Muotri. “Proving causation was the first step.”

Carrying out the experiment presented its own challenges. Muotri’s team had to first isolate the virus in Brazil, which wasn’t an easy task because there are many strains of the virus. Additionally, none of them had been linked to a birth defect before. After isolating a strain from a deceased microcephalic baby, they infected two different types of pregnant mice. One line yielded pups with growth arrest and microcephaly. In the other, the virus couldn’t cross the placenta barrier. “We could conclude that the Brazilian Zika virus is sufficient to cause birth defects and the susceptibility of fetus infection is dependent on a robust and functional immune system” said Dr. Muotri.

The second step of the experiment was to show that virus could affect humans. To do so, Muotri’s group infected human cerebral organoids with different strains of the virus. “The Brazilian version was more aggressive” added Muotri. “The virus infected and very efficiently kills neural progenitor cells (fast dividing, proliferating cells in the developing brain responsible for the cortex formation)”. The effects of the Brazilian virus on the organoid mirrored what was found in the microcephalic brains of affected Brazilian babies.

Globally, the implications of this discovery have a huge impact. Drugs and vaccines can now be created to prevent the virus infection. Locally, the impact of the discovery is also significant because the mosquito carrying the virus is predicted to arrive in the US by summer and San Diego is a potential hot-spot for the virus, according to Muotri.

Muorti’s group and his colleagues are currently testing available drugs on the Zika virus, but in the meanwhile, there are steps that we can take to avoid the mosquito. Muotri advises, “The mosquito likes to put eggs on water, so you should empty and scrub, turn over, cover or throw out any items that hold water (such as vases and flowerpot saucers) near your house. Use of repellent during the day time is also recommended (but do not use in babies, prefer a net)”.

Natalie Lam is a contributing news writer for The Triton. She can be reached at nplam@ucsd.edu.

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