Bengaluru: Scientists in India and Denmark have developed an experimental antivenom that protected mice against venom from several Indian cobra species, including two species of king cobra.
The research was carried out by scientists at the Centre for Ecological Sciences at the Indian Institute of Science in Bengaluru, in collaboration with researchers at the Technical University of Denmark. The study was published in Science Translational Medicine on September 9.
The experimental antivenom uses five engineered antibody fragments called nanobodies. The researchers selected the nanobodies to target important toxins found in cobra and king cobra venom.
These include alpha neurotoxins, cytotoxins and phospholipases A2, which are among the major toxin groups responsible for the harmful effects of cobra venom.
The researchers tested the antivenom against venom from different geographical populations of spectacled cobras and monocled cobras. They also tested it against venom from the two Indian king cobra species, Ophiophagus hannah and Ophiophagus kaalinga.
In experiments involving mice, the five nanobodies worked together to neutralise the effects of the venom and protect the animals from lethal exposure.
The researchers also carried out rescue experiments after venom had already been injected. The Indian Institute of Science reported that the treatment was able to save mice even when it was given 30 minutes after venom injection.
The findings are significant because snake venom can vary between species and between snake populations in different parts of a country. Such differences can affect how well existing antivenoms work against particular venoms.
Conventional antivenoms are generally produced using antibodies obtained from animals such as horses that have been immunised with snake venom. The new approach uses recombinant technology to produce engineered antibody fragments.
Researchers say this approach could eventually help address some limitations of existing antivenoms, including differences in venom between snake species and populations and variation between batches.
The research builds on earlier work by the Danish team on nanobodies that can target snake venom toxins. The scientists found that some important toxin families are shared by different venomous snakes, allowing antibody fragments developed against certain toxins to be tested against other snake venoms.
India has one of the world's largest snakebite burdens. The Indian Institute of Science estimates that nearly 50,000 people die from snakebite in the country each year.
The wider global burden is also severe. The World Health Organization estimates that between 81,000 and 138,000 people die from snakebite envenoming around the world each year. Millions more are bitten, with hundreds of thousands developing serious illness.
Existing antivenoms remain the specific treatment for snakebite envenoming. However, access to effective antivenom and differences in venom composition remain important challenges in many parts of the world.
The World Health Organization has also identified engineered antibody biologics as an area for the development of new snakebite treatments.
The new research could help guide the development of antivenoms that are more consistent and able to target toxins shared by several snake species. Researchers could potentially add other antibody components in the future to target additional medically important snakes.
However, the new antivenom is still at the experimental stage. The researchers tested it in mice, not humans, and it has not been approved for use in people.
It also cannot yet be described as a universal antivenom for all cobras, king cobras or other venomous snakes. Further research and clinical studies will be needed to determine whether the approach is safe and effective for treating human snakebite victims.
The study represents an important step in the search for more consistent and broadly effective snakebite treatments, but the experimental antivenom remains some way from possible use in human medicine.