Experimental mRNA vaccine may protect against multiple Ebola viruses

A novel mRNA vaccine has been created, potentially offering long-term protection against the deadliest Ebola-related viruses, including the Bundibugyo strain currently spreading in two African nations.

It is estimated that over 600 individuals have contracted the Bundibugyo virus in the Democratic Republic of the Congo, with two confirmed cases in Uganda. As a result, the World Health Organization has declared this outbreak a public health emergency of international concern.

The Bundibugyo virus is part of a group of viruses known as orthoebolaviruses, which also includes the Zaire and Sudan viruses. All three are capable of causing severe illness in humans.

Historically, outbreaks of the Bundibugyo virus have been less frequent compared to the Zaire strain, which affected over 28,000 people from 2014 to 2016. While there are two vaccines approved for the Zaire virus, no vaccines exist for the Bundibugyo or Sudan viruses.

Researchers, led by Yanfeng Yao at the Wuhan Institute of Virology in China, report that they have developed a vaccine in mice that offers protection against all three viruses.

“The development of a broad-spectrum vaccine has the potential to efficiently mitigate outbreaks caused by multiple orthoebolaviruses,” the researchers state in their study.

The challenge for scientists in creating a vaccine for these Ebola-family viruses is that each virus contains different glycoproteins necessary for infection. However, they all share the same nucleoproteins that package the virus’s genetic material.

To create their vaccine, Yao and his team combined mRNA encoding the glycoproteins of each virus, along with the shared nucleoprotein, into a single lipid nanoparticle. This nanoparticle—a sphere of fat molecules—protects the mRNA until it reaches the body’s cells.

Mice received the vaccine and were monitored for immune response before being exposed to all three viruses. The vaccinated mice showed complete protection against the Zaire and Sudan viruses and strong protection against Bundibugyo. Hamsters exposed to the Sudan virus also gained complete protection.

The researchers assert that their trials demonstrate the development of an effective broad-spectrum mRNA vaccine against the Zaire, Sudan, and Bundibugyo viruses. However, they caution that further research is needed to confirm its safety and efficacy in humans, as it has only been tested on rodents so far.

Robert Cross from the University of Texas Medical Branch expresses optimism about exploring more creative next-generation Ebola vaccines.

Nevertheless, he notes that testing in non-human primates is considered the gold standard for predicting human efficacy, and approval for a vaccine targeting multiple pathogens will be challenging.

“It’s hard enough to get a vaccine approved for a specific virus. Securing approval for a multivalent vaccine involves an arguably more complex path,” Cross states.

Adrian Esterman from Adelaide University in Australia views the study as promising but highlights the limitation that the findings are based solely on rodent models.

“It is likely too early to establish a firm timeline for clinical use, as transitioning from this stage to human trials typically requires several years due to additional animal studies, manufacturing development, and safety testing,” he explains.