Peter Green MRCVS shares news of an encouraging development in the battle against African horse sickness
African horse sickness (AHS) is a serious, often fatal virus disease of horses in the southern hemisphere, which may well spread to Europe as a result of climate change.
The current live vaccine against AHS is not risk-free: it can revert to its dangerous state and it can cause deformities in foals if pregnant mares are vaccinated. In addition, there is currently no way to distinguish between horses infected with the disease and those that have been vaccinated.
However, scientists in South Africa, where AHS is endemic, have been working hard on this problem with the help of tobacco plants and have just reported some encouraging results.
Plants and animals can suffer diseases caused by the same kinds of germs, since both are composed of cells that share many of the same internal structures. This similarity can be used to great advantage when it comes to tackling animal diseases, such as AHS.
The AHS virus itself is not a complicated structure: it has a core of proteins and several layers of protein capsule. These compounds can be separated.
The scientists took just a few of the proteins and introduced them into a well-known and well-studied plant virus before infecting tobacco plants with this virus. They then harvested the tobacco leaves and were able to extract the AHS proteins, which the plant virus had manufactured as it infected the leaves.
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The researchers had used proteins from several strains of AHS and were able to bundle all these up together into what they called ‘virus-like particles’. These were purified, made into a vaccine and tested on horses.
The plant-derived vaccine generated a detectable immunity to AHS in the horses and there were no side effects. This is really encouraging because these virus-like particles are dead proteins and so cannot cause disease.
Although the research is in the early stages, using plants to produce a safe animal vaccine is an exciting prospect.
