Experimental mRNA vaccine targets Ebola’s three hardest threats

broad-spectrum mRNA – A research team reports an experimental mRNA vaccine that protected rodents against three Ebola-family viruses—Zaire, Sudan, and the Bundibugyo strain now causing an outbreak in the Democratic Republic of the Congo and Uganda. The approach mixes mRNA for each

On a day when health workers are still trying to contain the Bundibugyo Ebola outbreak in parts of the Democratic Republic of the Congo, a different kind of weapon is emerging in the lab: an experimental mRNA vaccine designed to aim beyond a single strain.

More than 600 people are thought to have been infected with Bundibugyo virus in the Democratic Republic of the Congo, and there have been two confirmed cases in Uganda. The World Health Organization has declared the outbreak a public health emergency of international concern.

Bundibugyo is one of the orthoebolaviruses—the Ebola-family group that also includes Zaire virus. the most common form of Ebola. and Sudan virus. All three can cause severe disease in humans. While Bundibugyo outbreaks have historically been rare compared with Zaire. the scale of Zaire has been devastating: Zaire infected over 28. 000 people between 2014 and 2016. Two vaccines have been approved for the Zaire virus. but there are no approved vaccines for the Bundibugyo or Sudan viruses.

In a new paper, Yanfeng Yao at the Wuhan Institute of Virology in China and colleagues say they have developed a vaccine that works in mice to protect against all three viruses.

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

Their hurdle was biological—and specific. Each virus carries different compounds called glycoproteins that are essential for infection. But they also share the same nucleoproteins that package the virus’s genetic material. The team built a single mRNA formulation by combining mRNA encoding the glycoproteins of each virus. plus the shared nucleoprotein. inside one lipid nanoparticle. Lipid nanoparticles are spheres of fat molecules designed to protect the mRNA vaccine until it can reach the body’s cells.

The researchers administered the vaccine to mice and monitored immune responses before exposing the animals to all three viruses. All immunised mice gained complete protection against infection by the Zaire and Sudan viruses. and they were “conferred ‘strong’ protection” from Bundibugyo. Hamsters exposed to Sudan virus were also afforded complete protection by the vaccine.

The team says the results show a broad-spectrum mRNA vaccine that can effectively defend against Zaire, Sudan, and Bundibugyo vaccines. But the caution is just as clear: the work has only been tested on rodents so far, and much more is needed to prove safety and effectiveness in humans.

Robert Cross at the University of Texas Medical Branch said he is “glad to see more creative next-generation [Ebola] vaccines being explored.” Still. he warned that testing in non-human primates is the gold standard for predicting how well a vaccine will work in humans. and that approval will be difficult for a vaccine targeting multiple pathogens.

“It’s hard enough to get a vaccine approved for a specific virus. Getting to license with a multivalent vaccine has an arguably more complex path to approval,” Cross said.

Adrian Esterman at Adelaide University in Australia called the preclinical study promising. but pointed out the limitation that the findings only apply to rodents. He added that it is “probably too early to give a firm timeframe for clinical use. ” and said moving from this stage to human trials would usually take several years. Further animal work—such as primate testing—plus manufacturing development and safety testing would still be required, he said.

mRNA vaccine Ebola Bundibugyo Zaire virus Sudan virus orthoebolaviruses lipid nanoparticle Wuhan Institute of Virology non-human primates preclinical study