Doctors have long had only limited means of saving people bitten by venomous snakes. Venom differs by species, so it is hard to counter every type with a single antivenom. Now scientists in India and Denmark have offered new hope: they have made an antivenom that can work against the venom of various Indian cobra species. The researchers believe that if the treatment succeeds, snakebite deaths worldwide could be cut sharply.

The study was published on Saturday (12 September) in the US journal Science Translational Medicine. It says the new antivenom is made of five kinds of small antibody fragments, or nanobodies. In tests it was highly effective in blocking the venom of the spectacled cobra, the monocled cobra and two species of Indian king cobra.

In India alone about 50,000 people are thought to die of snakebite every year, the highest number in the world. Venom differs by species: some attack the nervous system, others damage the blood or body tissues. That makes it hard to produce one antivenom against all venoms.

Antivenom used in hospitals also has limitations. Batches made at different times may differ in effectiveness, it has side effects, and it does not work equally well against every species.

In the conventional method, animals such as horses are repeatedly injected with venom so that their bodies make antibodies against it. Those antibodies are then collected from the animal's blood to make antivenom. The method is expensive and yields relatively few of the antibodies needed.

The new method is different. The researchers injected the venom of various cobra species into camelids such as llamas and alpacas, then tested the antibodies in their blood to see which could neutralise the venom's harmful components. The scientists see the potential to identify those antibodies and produce them in the laboratory using microbes.

From these antibodies the researchers chose five nanobodies and combined them into a mixture, or cocktail. The antibodies bind to the harmful components of cobra venom and stop the venom reaching particular cells or tissues.

In tests the cocktail succeeded in blocking the venom's effects. In some cases it saved mice from death even 30 minutes after they were envenomed. Mice that had become paralysed or showed signs of nervous-system poisoning also recovered, with no further symptoms of envenoming.

Karthik Sunagar, one of the study's authors, said there had been no major change in antivenom treatment for almost 100 years, and that the new method could play an important role in tackling India's snakebite problem.

Andreas Laustsen, a scientist at the Technical University of Denmark and another author, said the study showed a way to make a new kind of antivenom. By targeting the components of local snake venom that do the most harm, it should be possible to make separate antivenoms for different regions of the world.

It is also thought that adding more components to the new antibodies could extend their effectiveness to other important venomous snakes. But the researchers say more testing is needed before it can be used to treat people.

Source: Jagonews24. First published in Bengali on The Agro News.