More than 300,000 snakebite cases occur in Africa annually, resulting in at least 7,000 deaths, as well as numerous amputations and injuries. Now, scientists have invented a new nanobody-based antivenom that shows promise against 17 dangerous African snake species.

Until now, the mainstays of treatment have been antivenoms created by exposing horses to particular venoms and then isolating protective antibodies from the animals’ blood. These traditional antivenoms can occasionally cause allergic reactions in patients, and they are effective against only one or a few of related snake species.

Now, in a study published in the journal Nature, scientists report creating an antivenom that targets most of Africa’s deadliest elapids, meaning cobras, mambas, and the rinkhals, also called ring-necked spitting cobras. Instead of horse serum, the antivenom uses eight engineered nanobodies that are essentially tiny antibody fragments designed to block key toxins in the snakes’ venoms.

Juan Calvete, director of the Evolutionary and Translational Venomics Laboratory at the Biomedicine Institute of Valencia, who was not involved in the study, said the new nanobody-based antivenom is “a remarkable advance in the development of synthetic antivenoms.” However, he noted that in its current form, the antivenom may be expensive to make, and thus challenging to use in poorer regions. To create the new antivenom, researchers exposed an alpaca and a llama to venoms from 18 African snakes, including cobras, mambas, and the rinkhals. These snakes’ venoms are potent and can cause serious problems, such as paralysis and tissue damage, and they also contain a diverse range of toxins.

The llama and alpaca exposed to the venoms produced special, tiny antibodies, known as nanobodies. The compact size of these nanobodies enables them to diffuse quickly through tissues and bind toxins at hard-to-reach sites in the body, the study authors noted.

The researchers collected the animals’ blood and used a technique to find nanobodies that stick well to various venom toxins. The nanobodies that latched on most effectively were then made in the lab and tested for their ability to block the venoms’ effects. Finally, eight of these engineered nanobodies were combined into a powerful mix to create the new antivenom.

In lab tests in mice, this nanobody serum prevented death from 17 of the 18 target snake venoms; the venom of the eastern green mamba (Dendroaspis angusticeps) was the only one not fully neutralized. Further analyses suggested that the antivenom neutralized seven toxin families found within the venoms and that it reduced tissue damage from venoms known to kill cells.