New nanobody antivenom offers broad protection against Indian cobras

Snakebite is a neglected tropical disease, causing hundreds of thousands of deaths and disabilities each year. India alone reports nearly 50,000 deaths every year, the most by snakebite in the world.

Each snake species produces a distinct cocktail of toxins that attack nerves, blood, or tissues, making it difficult to develop a unified treatment. Current animal-derived antivenoms also have drawbacks such as batch-to-batch variability, side effects, and limited species coverage. Their production is costly and outdated, relying on venom milking and animal immunisation, with low yields of active antibodies.

To solve this problem, Kartik Sunagar, Associate Professor at CES, collaborated with Andreas Laustsen, Professor at DTU, to engineer antibodies that would work against venom produced by various cobra species in India.

Unlike conventional antivenoms, these recombinant antibodies can be manufactured using microbial and humanized expression systems without repeatedly immunising animals like horses. Additional antibody components can be added to expand protection to other medically important snakes, allowing future recombinant antivenoms to be tailored for different regions or species.

"Antivenom treatment has virtually not changed for over 100 years," Sunagar says. "This is the only next-generation antivenom we have now, which could tackle India's snakebite problem."

In a previous study, Laustsen and colleagues used the blood of camelids (like alpacas and llamas) immunized with venom from various African snake species, extracted antibodies produced against the venom, and used microbial cells to mass-produce these antibodies in the lab. They then displayed the antibodies on bacteriophages, exposed them to venom from various snake species, and isolated specific antibody fragments that could bind to and neutralize the toxins in the venom.

"This work provides a blueprint for how recombinant antivenoms can be tailored to different regions of the world by targeting the toxin families that drive disease in local snake species," says Laustsen.

Antibodies are usually Y-shaped with both heavy and light-chain proteins. The researchers used a portion at the tip of the Y shape, which is made up of light-chain proteins that can specifically bind to the venom toxins. Sunagar and colleagues isolated a cocktail of five such antibody fragments called nanobodies that could bind to toxins in the various cobra species they tested. They found that this cocktail could neutralize venom activity and prevented the venom from binding to its target receptor.

The team then tested the antibody cocktail in mice injected with venom and found that it protected the animals against toxins from spectacled cobras, monocled cobras, and both Indian king cobra species. It was also able to save mice from death even 30 minutes after venom injection. "Even mice that were paralysed or had typical neurotoxic symptoms would revert to a completely asymptomatic state," Sunagar says.

Previously, researchers have often required relatively large amounts of monoclonal antibodies to neutralize snake venom in mice, raising concerns about the doses that might ultimately be needed in humans, Sunagar explains. "Here, we showed that it is possible to neutralize venom using very small amounts of carefully selected and engineered antibodies. This could potentially help address some of the cost and safety concerns associated with administering large quantities of antibodies," he adds.

"This project combined expertise in toxinology, antibody engineering, and protein science across several countries," says co-author Anne Ljungars, a senior researcher at DTU. "Solving a global health problem like snakebite requires exactly this kind of interdisciplinary collaboration."

Source:

Indian Institute of Science (IISc)

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