A recombinant antivenom made from five small antibody fragments protected mice from lethal cobra and king cobra venom, offering a potential new approach to a treatment that has remained difficult to standardize and broadly deploy.

Snakebites kill thousands of people every year, with India accounting for roughly half of these deaths. The main treatment is antivenom made by immunizing horses or other large animals and collecting antibodies from their blood.

These treatments have saved countless lives. But they have an important limitation: snake venom varies widely between species and between different populations of the same species. An antivenom made using venom from one region may work poorly against a snake from another.

Instead of relying on antibodies collected from animals, a new study uses five antibody fragments called nanobodies. Each nanobody targets a different major toxin found in cobra and king cobra venom. Together, the five nanobodies formed a new antivenom that protected mice from the lethal venom of several medically important snakes across India.

The Problem with Traditional Antivenom

Conventional antivenoms are made by repeatedly exposing horses to snake venom. The animals produce many different antibodies against the venom, which are then collected and purified to make the final treatment. Because the resulting product contains a mixture of antibodies, its composition can vary from one production batch to another. More importantly, it does not necessarily neutralize every toxin found in every snake population.

This is a particular problem in India. Commercial antivenoms are primarily produced against the country’s “big four” snakes: the Indian cobra, common krait, Russell’s viper and saw-scaled viper. Other medically important snakes, including king cobras, may receive little or no protection from these products.

Five Nanobodies, Five Targets

Nanobodies are small fragments of antibodies originally found in camelids such as llamas and camels. Their small size gives them several useful properties: they are highly stable, can be produced in bacteria, and can potentially be manufactured at large scale without relying on animals.

The researchers selected five nanobodies that recognize major toxin families found in Indian cobra and king cobra venoms. Two of the nanobodies target different types of neurotoxins, which can interfere with the nervous system and cause paralysis. Two others target cytotoxins, which can damage cells and surrounding tissue. The fifth targets a group of toxins that can damage cell membranes. Rather than one antibody designed to neutralize every component of venom, these five nanobodies were combined into a single cocktail that aimed to cover many related toxins at once.

One Cocktail, Multiple Snakes

The nanobodies were first tested to verify that they could recognize venoms from different regions of India. The cocktail bound to venom from five populations of spectacled cobra, two populations of monocled cobra and two species of king cobra. The results showed that the same five nanobodies could recognize venom despite substantial geographic variation.

In a following experiment, when venom was mixed with the nanobody cocktail before being injected into mice, all treated animals survived exposure to venom from spectacled cobras, monocled cobras and both Indian king cobra species tested. In contrast, untreated animals died rapidly.

In a situation designed to better mimic an actual snakebite, mice were first injected with venom under the skin and then received the nanobody treatment five minutes later. Again, all treated mice survived the 24-hour observation period.

Protection Even After a Delay

Real snakebites are not treated immediately. A victim may need to travel to a hospital before receiving antivenom. Therefore, the treatment was also tested after a delay.

In one experiment, the nanobody cocktail was given five, 10 or 20 minutes after venom exposure. Even when administered to mice 20 minutes after the venom was injected, the treatment continued to provide complete protection, suggesting that the nanobodies can do more than prevent toxins from acting before exposure. They may also be able to neutralize venom after it has entered the body.

However, the study found one important caveat: the cocktail did not protect against common krait venom, which is dominated by different toxins that were not targeted by the five-nanobody formulation.

A More Flexible Antivenom

Since the recombinant antivenom is made from a defined set of components, new nanobodies could be added to target toxins from additional snake species. Future directions include antivenoms tailored to particular regions or designed to cover major venom families across larger geographic areas. The nanobodies can also be produced in bacteria, potentially allowing more consistent and less animal-dependent manufacturing.

Though additional work is needed to understand how the nanobodies behave in larger animal, the study demonstrates a fundamentally different way to build an antivenom. Rather than producing a broad mixture of antibodies in an animal and hoping it covers the venom, scientists can identify the toxins that matter, select antibodies against them and combine those components into a defined treatment.

That could make future antivenoms more precise, more adaptable and easier to manufacture, all while potentially extending effective treatment to the many snakebites that current antivenoms still struggle to cover.