Sara Landeras-Bueno, Ph.D.

Combating emerging Ebola virus threats with affordable cures

FUNDED BY: the generosity of Rachel & Bob Perlmutter, Raydene &
Peter St. Clair, and 2019-20 Various Donors

Outbreaks of Ebola virus are occurring with greater frequency. During the last seven years, six outbreaks swept through populations on the African continent without any warning where or when it would strike, killing between 50 and 90 percent of infected people. The 2013–2016 epidemic occurred more than 1,000 miles from any previously known location of Ebola virus, and spread from one infected toddler to nearly 30,000 people across four African countries, North America and Europe. The current 2018-2019 outbreak in Africa has now persisted into its second year poised to become the second largest in human history.

Despite the global attention and frequent occurrence, we still lack any FDA-approved drugs to treat Ebola virus infection. There are candidate vaccines, but vaccine coverage is inadequate, and vaccinated medical workers are still dying of Ebola virus. Antibody therapies have shown some promise but are expensive, difficult to administer on an outbreak scale, and less effective once the disease has been established. Further, we now know that the virus hides and persists in immune-privileged sites such semen and the central nervous system. We urgently need inexpensive, potent antivirals that can reach these immune privileged sites and clear an established infection.

Such antivirals have been successfully developed for herpesviruses or influenza viruses, cured previously incurable hepatitis C infections and enabled HIV-infected people to enjoy a normal lifespan. What these effective antivirals have in common is that they target the same viral component: the viral polymerase. These findings suggest that Ebola virus polymerase, a central component for the multiplication of the virus, may be an ideal target for the design of effective antivirals.

The mission of this project is to purify and visualize the Ebola polymerase at subatomic level. I will use new technology now available at LJI to overcome previous technical hurdles that have prevented others from obtaining and stabilizing enough material for visualization. The structures determined here, the first ever for this high-value target, will open the door to needed antiviral therapies.

Six-Month Project Update

The Ebola viruses cause hemorrhagic fever with up to 90% lethality and limited FDA-approved treatments against these viruses are available. High-resolution structures of key proteins involved in Ebola virus replication can accelerate identification and characterization of effective drugs to treat Ebola virus infections. The Ebola virus polymerase governs replication of viral genetic material and is a prime target for therapeutic interventions. I aim to generate the first near-atomic resolution structure of the Ebola virus polymerase to reveal conserved and essential atomic features that will guide design and improvement of antiviral drugs against Ebola virus. To produce this structure, I first explored techniques to stabilize this dynamic polymerase to facilitate imaging studies. I applied these techniques to express full-length polymerases of key pathogenic Ebola virus species (Zaire, Sudan, Reston, Mengla) and the related Marburg virus. The polymerase expression levels of the various ebolavirus polymerases differed significantly among virus strains. I identified the virus strain that expresses the most stable polymerase complex, which I am now successfully purifying on a larger scale to use in structural analyses with our stateof-the-art Titan Krios microscope at LJI. From these analyses, I will visualize structural details and vulnerabilities of Ebola virus polymerase.