Study Finds Zika May Have Impact on All Adults, Not Just Pregnant Women
Scientists have discovered that certain brain cells found in all adults are affected by the disease
Zika first came to the attention of the public at the beginning of 2016 when it emerged in Latin America. Anxiety began to rise when it was linked to microcephaly, a birth defect that had previously occurred only rarely but began to become more and more common this year.
Scientists and researchers have since been working hard to learn as much as possible about the Zika virus in order to figure out how to prevent it and protect the public. These efforts are now even more crucial with the discovery by researchers from The Rockefeller University and La Jolla Institute for Allergy and Immunology that Zika may be extremely dangerous to everyone, not just pregnant women.
Using mice models, the researchers conducted a study that found that the virus targets certain brain cells in adults linked to learning and memory. Although the long-term effects on those cells are not yet known, scientists now know that it is possible that Zika could lead to depression or the development of Alzheimer's.
"This is the first study looking at the effect of Zika infection on the adult brain...Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think," said Joseph Gleeson, one of the researchers.
Scientists believe that it is the progenitor cells that are most impacted by Zika. These cells are effectively the brain's original stem cells. When humans are developing in the womb, their brains are formed almost entirely of progenitor cells that eventually form the neurons common in health adult brains.
Although researchers currently believe that fully-formed neurons become resistant to the virus, progenitor cells remain susceptible to it. This partly explains why unborn children develop birth defects when exposed to Zika while adults do not seem affected. However, some of these cells stay in adult brains even after they have fully developed. The scientists believe that these cells have much to do with learning and memory and may still be negatively affected by Zika.
"Zika can clearly enter the brain of adults and can wreak havoc...But it's a complex disease -- it's catastrophic for early brain development, yet the majority of adults who are infected with Zika rarely show detectable symptoms. Its effect on the adult brain may be more subtle, and now we know what to look for," said professor Sujan Shresta.
As part of the study, the researchers infected mice models with what ConsumerAffairs terms a "mimic" of the virus and then scanned their brains to track activity. These scans were intended to highlight parts of the brains that were most affected by the virus, and the two sections where progenitor cells were located lit up.
"Our results are pretty dramatic -- in the parts of the brain that lit up, it was like a Christmas tree...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," said Gleeson.
At this time, not enough far-reaching data has been collected for scientists to know the exact consequences possible for adults infected by the virus. However, Gleeson warns that memory and learning problems are a definite possibility, as are conditions such as depression and Alzheimer's disease.
"In more subtle cases, the virus could theoretically impact long-term memory or risk of depression, but tools do not exist to test the long-term effects of Zika on adult stem cell populations," he said.
Though the scientists believe that healthy adults should be able to combat Zika effectively, they caution that the elderly and those whose immune systems are weak may be at a greater risk than previously believed. They suggest that public health officials should take note of the study and begin to monitor it on a larger scale.
"The virus seems to be traveling quite a bit as people move around the world. Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women," said Gleeson.
For now, it will most likely function as an opening look into the effects of Zika on adult brains. Researchers will need to conduct further investigations to determine whether or not progenitor cells can recover from damage caused by the virus, whether it causes any lasting biological consequences, and the degree to which the adult brain is impacted.