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 The findings, published on Thursday in the journal "Cell Stem Cell,"
are the first to look at whether Zika can attack the same kinds of
cells in adult mice that they do in fetal mice.
Experts cautioned that the findings are preliminary and may not have
any correlation to how Zika impacts human brain function, but they
suggest the need for follow-up research.
"This is one potential consequence we need to look at," said Dr.
Joseph Gleeson, an expert in pediatric brain disease at The
Rockefeller University in New York, who led the study.
Zika has already been shown to attack fetal brain cells known as
neural progenitor cells - a type of stem cell that gives rise to
various kinds of brain cells. The death of these cells is what
disrupts brain development and leads to the severe birth defects
seen in babies whose mothers were infected with Zika during
pregnancy.
U.S. health officials have concluded that Zika infections in
pregnant women can cause microcephaly, a birth defect marked by
small head size that can lead to severe developmental problems in
babies.
The connection between Zika and microcephaly first came to light
last fall in Brazil, which has now confirmed more than 1,600 cases
of microcephaly that it considers to be related to Zika infections
in the mothers.
Fetal brains are chock full of neural progenitor cells, which are
responsible for making cells that form key brain structures. Adults,
whose brains are fully formed, have far fewer and there are some
pockets remaining - including in the hippocampus, a part of the
brain involved in memory and learning.
Gleeson wanted to see if Zika could attack these cells in adult
mice. To find out, his team injected the virus into lab mice and
examined their brains for Zika infection.
In the hippocampus, Gleeson said "it lit up like a Christmas tree
and wiped out the stem cell population."
"Based on our findings, getting infected with Zika as an adult may
not be as innocuous as people think," he said.
There have already been signs that Zika affects adult nerve cells.
Several teams have published papers showing that in some patients,
Zika can cause serious brain and spinal cord infections - including
encephalitis, meningitis and myelitis - in people exposed to Zika.
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In rare cases, Zika has also been linked with Guillain-Barre
Syndrome, a post-infectious autoimmune disorder that can cause
temporary paralysis in adults.
"It's really unclear if this translates to human Zika infections,"
said Dr. Daniel Pastula, a neurologist and medical epidemiologist at
the University of Colorado Denver.
But if it does, it is not clear whether the effect is temporary or
lasting.
"Detailed neurological studies are needed in infected humans to
describe the effects of Zika virus infection on the brains of
adults," said Dr. Anna Checkley of the Hospital for Tropical
Diseases, part of University College London Hospitals.
Gleeson said the study needs to be replicated by other scientists,
and he wants to test other strains of Zika on adult mice at other
times during an infection to see if those viruses have the same
effect.
Since 2015, 66 countries and territories have reported evidence of
vector-borne Zika virus transmission, according to the World Health
Organization.
Earlier this month, researchers at Notre Dame University estimated
as many as 93 million people across Latin America and the Caribbean
could become infected with Zika in the current outbreak.
(Reporting by Julie Steenhuysen, editing by G Crosse)
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