Ebola mutation increased infectivity

By Kate Bass, B.Sc.Nov 4 2016

New research finds a genetic mutation in the Ebola virus that enabled it to target human cells more effectively during the recent Ebola epidemic.

In 2014, West Africa experienced the largest outbreak of Ebola in history. The speed with which the virus spread overwhelmed medical facilities and the Ebola outbreak soon reached epidemic proportions. The virus was highly contagious leading to infection of many of the health workers who were caring for the sick, and the high fatality rate prompted a massive global intervention to contain the virus.

It was believed that the Ebola virus remained essentially the same, but a new study indicates that a natural mutation occurred in Ebola virus during the latest epidemic that enhanced its ability to infect human cells.

Analysis of the DNA sequences of Ebola virus isolated from over a thousand patients infected during the recent outbreak led to researchers identifying a mutation . It was present within the gene encoding the glycoprotein through which the Ebola virus binds to receptors on host cells. Further investigations revealed that this mutation specifically helps the virus infect primate cells.

Assistant professor, Kristian G. Andersen of The Scripps Research Institute commented:

This receptor binding domain of the virus has been the same since the first Ebola outbreak in 1976...This is the only time we've ever seen a mutation in this domain".

The mutation occurred early in the epidemic and gave rise to the exponential increase in the number of infections. It is estimated that the mutated version of the Ebola virus caused about 90 percent of infections in the recent outbreak.

Since previous outbreaks had been successfully contained within a couple of weeks there had not been so many Ebola samples available for analysis and so mutations were more difficult to identify. The researchers believe the size of the latest outbreak gave the virus opportunity to adapt to human hosts.

Research Associate Nathan Grubaugh of The Scripps Research Institute explained:

We think this shows that when you have large outbreaks, of Ebola or other viruses, you could have these events where they may evolve to become more successful in a new host".

Further research is needed to confirm how this mutation enhances the human infectivity of the Ebola virus, but it may lead to conformational changes that allow the glycoprotein to better fit receptors on the surface of human cells. Other mutations that arose during the recent outbreak will also be studied.

Although these mutations are unlikely to cause another outbreak, this study highlights how genome sequencing can allow a fast response to emerging epidemics and tailoring of therapies to increase efficacy against the specific active strain of a virus.