AUG 08, 2016 12:00 PM PDT

TSRI Scientists Pinpoint Ebola's Weak Spots

The Scripps Research team succeeded in showing how experimental therapy ZMapp targets the Ebola virus, here targeting the virus's GP protein. (Image courtesy of Andrew Ward and Jesper Pallesen.)

LA JOLLA, CA – August 8, 2016 – Scientists at The Scripps Research Institute (TSRI) now have a high-resolution view of exactly how the experimental therapy ZMapp targets Ebola virus.

The new study is also the first to show how an antibody in the ZMapp “drug cocktail” targets a second Ebola virus protein, called sGP, whose vulnerable spots had previously been unknown.

“This sGP protein is tremendously important,” said TSRI Professor Erica Ollmann Saphire, who co-led the study with TSRI Associate Professor Andrew Ward. “This is the roadmap we need to target the right molecules in infection.”

“Determining the proper balance in targeting these two Ebola proteins will be key to building improved therapeutics,” added Ward.

The study was published August 8, 2016 in the journal Nature Microbiology.
 

Zooming in on ZMapp


Scientists need detailed images of Ebola virus’s molecular structure. Like enemy reconnaissance, structures can show where Ebola is vulnerable and how medical treatments can neutralize it.

TSRI scientists are harnessing an imaging technique called cryo-electron microscopy (in which a sample is pelted with electrons) to create high-resolution, 3-D images of Ebola virus and the antibodies that fight it.

“We’re at the cutting edge of our ability to resolve high-resolution protein complexes,” said TSRI Research Associate C. Daniel Murin, co-first author of the new study with TSRI Research Associate Jesper Pallesen.

In the new study, the researchers used cryo-electron microscopy to see exactly how Ebola virus interacts with the three antibodies in the ZMapp experimental therapy produced by Mapp Biopharmaceutical, also a study collaborator.

The researchers had imaged these interactions at a low resolution in a 2014 study, but the new study revealed substantially more details, including the exact angles the antibodies use to approach the molecule on the surface of the virus, termed its surface glycoprotein (GP), and the individual amino acid contact points at which the antibodies bind GP. This information provides new clues to researchers trying to make the antibodies even more effective.

“The three components of ZMapp, now resolved at high-resolution, can be further engineered in a structure-based manner for improved potency,” said Ward.
 

Solving an Elusive Structure


Next, the researchers took a closer look at one of the three antibodies that make up ZMapp, called 13C6. This antibody is unique because it can also target the soluble Ebola protein sGP.

sGP’s role in infection is a mystery. Ebola virus makes the protein profusely, indicating that it is important, but then sGP appears just to float in a person’s blood serum. One theory is that sGP may be essential in the natural host “reservoir.”

“Eighty to ninety percent of what Ebola virus makes in infection is this shed molecule,” said Saphire. “It’s like a smoke screen, and we need to know where it is similar to our target GP and where it is different.”

To add to the mystery, Ebola makes GP and sGP using the same gene. A small difference in the way the gene is read changes how the molecules are shaped and changes their roles.

One obstacle to understanding sGP is that it is too small to be seen with cryo-electron microscopes. To solve this problem, the researchers added “bulk” by pairing sGP with antibodies, including 13C6. This allowed them to kill two birds with one stone—they could see sGP’s structure while also studying how antibodies interact with it.

The new image shows the binding sites, or “epitopes,” the antibody targets. “We can see hot spots on this virus that we can hit,” said Pallesen.

This study is the latest research from the Viral Hemorrhagic Fever Consortium, an international partnership of research institutes led by Saphire. The researchers said collaboration with the consortium was key to this study, allowing scientists to share samples and data, including viral genetic sequences isolated from patients in the most recent Ebola outbreak.

In addition to Saphire, Ward, Murin and Pallesen, authors of the study, “Structures of Ebola virus GP and sGP in complex with therapeutic antibodies,” were Natalia de Val, Christopher A. Cottrell, Kathryn M. Hastie, Hannah Turner and Marnie Fusco of TSRI; Kristian G. Andersen of TSRI and the Scripps Translational Science Institute; Andrew I. Flyak and James E. Crowe of Vanderbilt University and Larry Zeitlin of Mapp Biopharmaceutical.

This study was supported by the National Institutes of Health (NIH, grant R01 AI067927), the NIH’s National Institute of Allergy and Infectious Diseases (grant U19AI109762 and U19AI109711) and the National Science Foundation.

This article was originally published on Scripps.edu.
About the Author
  • The Scripps Research Institute (TSRI) is one of the world's largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs about 2,700 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists-including two Nobel laureates-work toward their next discoveries. The institute's graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see www.scripps.edu.
You May Also Like
SEP 25, 2020
Clinical & Molecular DX
Ray of Hope: Rare Cancer Biomarker Discovered
SEP 25, 2020
Ray of Hope: Rare Cancer Biomarker Discovered
Biliary tract cancer, or BTC, isn’t as talked about as breast or prostate cancers, probably because its incidence ...
SEP 27, 2020
Microbiology
New Insight Into An Old Bacterial Pathogen
SEP 27, 2020
New Insight Into An Old Bacterial Pathogen
There are many different strains of Escherichia coli bacteria, some of which live harmlessly in the human gut. But some ...
SEP 30, 2020
Cancer
Chemokines Could be the Key in Controlling Glioma Stem Cells
SEP 30, 2020
Chemokines Could be the Key in Controlling Glioma Stem Cells
The transformation of a healthy cell into a cancerous one often comes with a slew of cellular signaling changes.  T ...
OCT 03, 2020
Clinical & Molecular DX
Test Diagnoses Dementia While You Sleep by Estimating Your Brain Age
OCT 03, 2020
Test Diagnoses Dementia While You Sleep by Estimating Your Brain Age
Researchers at Harvard have discovered a novel diagnostic marker of dementia for identifying undiagnosed patients or tho ...
OCT 05, 2020
Immunology
Can't Shed Those Extra Pounds? An Inflammatory Gene Could Be to Blame.
OCT 05, 2020
Can't Shed Those Extra Pounds? An Inflammatory Gene Could Be to Blame.
  Australian scientists have zeroed in on a gene linked to an increased obesity risk: a regulator of inflammation c ...
OCT 06, 2020
Microbiology
Scarlet Fever 'Superclones' Pose Rising Public Health Threat
OCT 06, 2020
Scarlet Fever 'Superclones' Pose Rising Public Health Threat
More than 100 years ago, the world faced waves of scarlet fever epidemics; between around 1820 and 1880 there were sever ...
Loading Comments...