Variations in proteins on the outer shell, or "envelope," of the
virus may explain how Zika enters human cells and suggests new ways
to fight the virus with drugs or a vaccines, said Dr. Anthony Fauci,
director of the U.S. National Institute of Allergy and Infectious
Diseases, which funded the study published in the journal Science.
Zika is very similar to other members of the flavivirus family such
as dengue, Yellow fever and West Nile, Fauci said, with one key
"There was one very discreet stretch of the protein on the envelope
that is really different than the other flaviviruses," Fauci said.
"That is like a big red flag."
Fauci said the important structural difference from similar viruses
may explain the link between the mosquito-borne Zika virus and two
disorders, the birth defect microcephaly and the paralyzing
autoimmune ailment Guillain-Barre Syndrome.
To better understand why Zika behaves so differently from related
viruses, Richard Kuhn, Michael Rossmann and colleagues at Purdue
University created the picture of a mature Zika virus particle with
a technique that provides a very high resolution image of the
The difference in Zika's structure compared to similar viruses was
seen in a region of the envelope protein that flaviviruses may use
to attach to some human cells.
This protein is also a key target of the immune system's response to
the virus, making it potentially useful in vaccine development.
"They haven't proven it yet, but it is a very important first clue,"
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Zika is spreading rapidly in South and Central America and the
Caribbean, and has been linked in Brazil to thousands of cases of
microcephaly, a disorder marked by small head size and
underdeveloped brains in babies. The World Health Organization in
February declared the Zika outbreak a global health emergency.
Scientists believe Zika is neurotropic, meaning it specifically
attacks nerve cells. It is the only mosquito-borne virus ever linked
to a birth defect.
Zika has not been proven to cause microcephaly, but there is
mounting evidence suggesting it does. Brazil, hardest hit by the
virus, has confirmed more than 900 cases of microcephaly, and it
considers most cases to be related to Zika infections in the
mothers. Brazil is investigating nearly 4,300 additional suspected
cases of microcephaly.
(Reporting by Julie Steenhuysen; Editing by Will Dunham)
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