New hope in the fight against African horse sickness

Researchers from the Biopharming Research Unit (BRU) of the Department of Molecular and Cell Biology at the University of Cape Town (UCT) have created a promising new vaccine candidate to help prevent the devastating effects of African horse sickness, the producing in tobacco plants.

It is extremely immunogenic and also produces neutralizing antibodies when administered to healthy horses, said Professor Ed Rybicki, director of BRU. This means that even if the vaccine works really well during the first tests, it must be tested against a true outbreak of African horse sickness before it can be sold.

The results were published recently in the highly respected Veterinary research newspaper.

The need for an effective vaccine against African horse sickness is urgent. The disease is devastating, especially in Africa, where up to 90% of infected horses die in some homes.

The current commercial vaccine is what is called a live attenuated vaccine. Even though it remains effective, it carries some risks, according to Professor Alan Guthrie, director of the Center for Research on Horses at the University of Pretoria and former collaborator of the BRU. project.

Live vaccines, he warned, can occasionally cause epidemics.

"A live attenuated vaccine poses two problems: rebadorting the genome and returning to virulence," he said, adding that this could lead to epidemics, as was the case in Western Cape during three epidemics different from SHA in the last 15 years. in 2004, 2011 and 2014.

That's why the vaccine currently available is not being used in other parts of the world, said Guthrie, noting that it is an imminent threat, as climate change allows the gnat to transmit the virus spread to new parts of Europe and the United Kingdom.

"Very promising"

Sue Dennis, PhD candidate and lead author of the study, said the BRU herbal vaccine did not have any of these risks, making it usable worldwide.

"We used tobacco plants to produce four different viral proteins that automatically bademble to form a virus-like particle (VLP). It looks like the virus, but without any genetic material, so it can not replicate or infect horses with the disease, "she said.

This VLP is the vaccine that, when injected into an animal, induces the immune system to produce antibodies against the virus, able to protect itself from the disease, thereby protecting the animal from the disease.

"When we tested the vaccine produced from plants in healthy horses, we found an immune response at the same level as the live vaccine."

Dennis said the first results seemed very promising, but that there was still work to be done.

"When we tested the vaccine produced from plants in healthy horses, we found an immune response at the same level as the live vaccine," she said.

In the first trials of vaccines in live animals, the most important is to show that the health of the animal is not affected and that the immune system produces neutralizing antibodies – better indication that the vaccine will act against the live virus.

In both cases, the BRU study was a success.

"The presence of neutralizing antibodies is a strong indication that horses will be protected from the virus. But to confirm that the vaccine offers complete protection, we need what's called a real challenge, "said Dennis.

In addition, the VLPs produced by Dennis and his colleagues represent only one strain of African horse sickness virus (AHSV); they are currently working on the production of vaccines against other strains.

Tobacco vaccine

This success builds on more than 10 years of work at BRU, which produces VLPs and other proteins in tobacco plants. In particular, years of work on the bluetongue virus, which is linked to the AHS virus, have contributed to this advance.

The next step is to test the protective power of the vaccine in horses against a challenge posed by living AHSV virus (the living challenge) alive to determine if this promising candidate vaccine can withstand the live virus.

If this is happening as well as the current live attenuated vaccine, BRU researchers believe that they will be well on the way to a new global vaccine against African horse sickness.

This research was funded in part by the Agency for Technology Innovation and Associated Intellectual Property (IP) was protected by UCT's Department of Research, Contracts and Innovation, which benefits from a handover from the National Office of Intellectual Property Management of the Department of Science and Technology (DST). (NIPMO) to support patenting.