Zika, the mosquito-borne virus linked to miscarriage and severe microcephaly in the fetuses of infected women, just lost a little bit of its edge to researchers. On Thursday, a Purdue University team published the virus's structure for the first time in the journal Science.
By outlining the physical structure of the virus in near-atomic detail, they have made it possible for scientists to determine the unique properties that make Zika so dangerous — and how those abilities might be knocked out with vaccines and treatments.
Zika is a flavivirus — a member of the same family as other mosquito-borne illnesses, such as dengue, West Nile and yellow fever — and its strong similarity with those better-understood viruses was confirmed in the study. But scientists are most interested in what makes Zika different.
In an interview with the Washington Post, Purdue's Michael Rossmann, who co-led the team with Richard Kuhn, said their examinations with an electron microscope had found significant changes to the Zika virus' surface.
It shares a basic structure with all flaviviruses: Genetic info in the form of RNA is surrounded by a fatty membrane, then encased in a protein shell with a 20-sided face. The protein shells are made of 180 copies of two different proteins, each composed of chains of different amino acids. Once inside a target cell, the virus breaks apart and forces the host to do its bidding, replacing the instructions coded into the cell's DNA with those programmed by viral RNA.
Zika differs most from other flaviviruses at a spot thought to be crucial to the cellular break-in. At this site, a carbohydrate molecule — made of different sugars — sits on the virus's protein shell. The so-called glycosylation site where Zika differs actually protrudes from the shell of the virus. In other viruses, similar protrusions act like strangers offering candy, tricking the human cell into binding with the invader. Like other flaviviruses, Zika seems to have a unique smattering of amino acids around that area.
"That makes it very different in a very important respect," Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told the Post. While the findings don't begin to explain how or why these changes might allow Zika to have such disastrous effects on fetal brain development, he said, "it provides a very plausible explanation for why we're seeing Zika do things these other flaviviruses don't do."