Breakthrough could help create vaccines and antivirals to prevent or treat infections linked with microcephaly and Guillain-Barré syndrome.

The Zika virus has been revealed to have a structure similar to viruses such as dengue and West Nile.
Scientists have worked out the structure of the Zika virus in a breakthrough that will aid the development of treatments to combat infection.

As well as aiding the design of vaccines and therapeutic drugs, scientists hope that the discovery will help develop better diagnostic tests for the virus, and throw light on the way the virus infects cells.

“This complete picture of the virus is really a blueprint for us, and many other groups, now to go in and determine how it works,” says Professor Richard Kuhn, an author of the study from Purdue University, Indiana.

Now present in 33 countries and territories in the Americas, the mosquito-borne virus has been linked to cases of microcephaly in babies, a condition resulting in smaller than usual heads and potential neurological damage, although scientists have yet to prove that Zika causes the condition.

– Brazil has so far confirmed more than 900 cases of microcephaly. In adults, the virus has been linked to the neurological condition, Guillain-Barré syndrome, which can cause temporary paralysis and, in some cases, permanent damage. The World Health Organisation now believes [pdf] that there is a strong scientific consensus that both conditions can be caused by the Zika virus.

Experts say the Zika blueprint, published in the journal Science, could provide the necessary insights for the development of vaccines and anti-virals to prevent and treat infections.

“The structure is a powerful platform for designing those kinds of preventative and therapeutic strategies,” said Professor Yorgo Modis from the University of Cambridge.

Using a strain of the virus from an outbreak in French Polynesia that began in late 2013, a team of scientists led by researchers at Purdue University used a technique known as cryo-electron microscopy to study its structure in near-atomic resolution.

Their results showed that the Zika virus has a structure similar to other flaviviruses, including dengue and West Nile viruses, with a core of genetic material in the form of RNA, encased inside a fatty membrane. This sits within an 20-sided protein shell covered in carbohydrates, known as glycans.

But these glycans and their surrounding amino acids differ between the flaviviruses – and Zika, the scientists discovered, is no exception.

Crucially, these are thought to play a role in enabling such viruses to attach to specific types of cells. “The question that obviously arises is, is that the reason why [the] Zika virus is neurotropic – namely it has a tendency to infect cells of the nervous system, particularity in the foetuses?” said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “We don’t know that yet, but the structure that was just published provides at least a plausible explanation.”

Insights from structure could also be essential for the development of vaccines to guard against infection, and for therapeutic drugs to fight the disease, as well as helping scientists to develop better ways to test for the infection.

“Showing at the very sensitive structural level this distinct difference between Zika and other flaviviruses can be very important in anything from figuring out why it has some special effects that the other viruses don’t have – but also can help you with diagnostics and therapeutics,” said Fauci.