High-res image of Ebola virus reveals how it evades the immune system

27 Jun

By creating the highest resolution image of the Ebola virus to date, researchers from The Scripps Research Institute in La Jolla, CA, have identified a viral protein that helps the virus escape attack from the immune system, shedding light on how Ebola infection could be prevented.
High-resolution image of the Ebola virus
From a high-resolution image of the Ebola virus, researchers discovered how a viral protein called VP35 helps shield the virus from the immune system.
Image credit: TSRI

Senior study author Erica Ollmann Saphire, director of the Viral Hemorrhagic Fever Consortium and professor at The Scripps Research Institute (TSRI), and colleagues publish the details of their findings in the journal Cell Reports.

As of 21st June, the World Health Organization (WHO) state there have been 27,479 confirmed cases of Ebola virus disease (EVD) worldwide in the 2014-15 outbreak and 11,222 deaths from the condition. The vast majority of cases have occurred in Guinea, Liberia and Sierra Leone.

While the rate of infection has reduced dramatically – with Liberia declared free of Ebola transmission back in May – researchers continue to work toward ways of treating the infection and preventing future Ebola outbreaks.

Past research from Ollmann Saphire and colleagues in 2012 revealed how a viral protein called VP35 plays a part in protecting both the Ebola virus and the Marburg virus – both of which belong to the Filoviridae virus family – from the immune system.

The team found that VP35 assists another viral protein, helping it coil and form a protein shell, known as a nucleocapsid. The nucleocapsid wraps around the genetic material of the virus, preventing immune cells from attacking it.

However, the mechanisms underlying this process were unclear, until now.

VP35 stops the nucleocapsid assembling incorrectly

Using X-ray crystallography to produce a high-resolution image of the Ebola virus, Ollmann Saphire and colleagues were able to see how VP35 helps the other viral protein build its defense.

They found that VP35 stops incorrect assembling of the nucleocapsid. What is more, the high-resolution image allowed them to see “side chains” – which they describe as atoms and structures important for drug design against a virus.

“This higher resolution is critical for design of much-needed antiviral therapeutics,” says Ollmann Saphire. “These structures provide the blueprints that we need to see key vulnerabilities to attack.”

Not only could these findings open the door to Ebola prevention and treatment strategies, the team says they could help tackle a number of other viruses. “The structure we revealed is likely conserved across all the filoviruses: Marburg, Sudan, Bundibugyo, Reston and Ebola,” says Ollmann Saphire.

First author Robert Kirchdoerfer, a research associate at TSRI, adds that the viral assembly information uncovered in this study could also be applied to Mononegavirales – an order of viruses that include rabies, measles and mumps.

In May, Medical News Today reported on a study published in mBio in which researchers claimed to have identified an “Achilles’ heel” for Ebola virus infection.

Study leader Kartik Chandran, of the Albert Einstein College of Medicine at Yeshiva University, NY, and colleagues found that the Ebola virus is unable to infect cells without attaching to a protein called Niemann-Pick C1 first.

Written by Honor Whiteman