While the potential role of the Zika virus on brain development in fetuses has raised fears among pregnant mothers worldwide, new research suggests certain adult brain cells may be vulnerable as well. A team of researchers at the Rockefeller University and La Jolla Institute for Allergy and Immunology has found that the Zika virus targets neural progenitor cells leading to loss of the brain's ability to form neurons. In developing infants, this can result in microcephaly leading to smaller than normal heads and numerous developmental disabilities.
Adult brains have previously been assumed to be less susceptible to the Zika virus due to being fully developed though the researchers have found this isn't necessarily the case. Even in mature brains, certain niches exist containing neural progenitor cells. Believed to be vital in learning and memory, lead researcher Joseph Gleeson, an adjunct professor at Rockefeller University, and his co-researchers used fluorescent biomarkers to demonstrate that adult neuroprogenitor cells could be infected by the virus as well.
"Our results are pretty dramatic -- in the parts of the brain that lit up, it was like a Christmas tree," says Gleeson in a press statement released by Rockefeller University. "It was very clear that the virus wasn't affecting the whole brain evenly, like people are seeing in the fetus. In the adult, it's only these two populations that are very specific to the stem cells that are affected by virus. These cells are special, and somehow very susceptible to the infection."
Healthy adults are usually able to fight off infection but people with compromised immune systems may be vulnerable. New neurons formed by neural progenitor cells are vital in neuroplasticity which allows the brain to change over time. “In more subtle cases, the virus could theoretically impact long-term memory or risk of depression,” says Gleeson, “but tools do not exist to test the long-term effects of Zika on adult stem cell populations.” Zika may also be linked to Gullain-Barre syndrome in which the immune system attacks parts of the nervous symptom leading to loss of motor functioning and paralysis in many cases. Though the cause remains unclear, Gleeson and his colleagues suggest that the disease can occur due to Zika attacking neuronal progenitor cells in the brain.
While more research is still needed to measure the subtle effects that Zika can have on adult brain functioning, the public health risks are alarming. Already widespread in Central and South America, the Zika virus seems poised to spread worldwide. “The virus seems to be traveling quite a bit as people move around the world,” says Gleeson. “Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women.”