Scripps Research scientists have discovered antibodies that protect against many deadly snake venoms. Scientists at Scripps Research have developed an antibody that could block the effects of deadly toxins in the venom of various snakes found in Africa, Asia and Australia.
An antibody that protects mice from often-fatal snake venom, including black mambas and king cobras, is described in a recent paper published in the journal. Science Translational Medicine . The new study used laboratory-grown forms of the toxin to screen billions of different human antibodies and determine which ones could block the toxins’ activity. This is a big step towards creating a universal anti-venom that is effective against the venom of all snakes.
“This antibody works against one of the major toxins found in many snake species that causes tens of thousands of deaths each year,” said senior author Joseph Jardine, an associate professor of immunology and microbiology at Scripps Research. “This could be incredibly valuable for people in low- and middle-income countries that bear the greatest burden of snakebite deaths and injuries.”
Impact on global health
More than 100,000 people die from snake bites each year, mostly in Asia and Africa, making it deadlier than most forgotten tropical diseases. Modern antivenoms are produced by inoculating animals with snake venom, and each is usually effective against only one species of snake. This means that many different antidotes must be produced to treat snake bites in different regions.
Jardine and colleagues had previously studied how broadly neutralizing antibodies to human immunodeficiency virus (HIV) might work by targeting regions of the virus that do not mutate. They realized that the problem of finding a universal antidote was similar to the search for a vaccine against HIV; Just as the rapidly evolving proteins of HIV have small differences among themselves, different snake venoms have enough diversity that an antibody that binds to one will generally prevent it from binding to others. But like HIV, snake toxins have conserved regions that do not mutate, and an antibody targeting them could work against all variants of this toxin.
antibody science
In the new study, researchers isolated and compared venom proteins from various elapids, a large group of venomous snakes such as mamba, cobra and krait. They found that a type of protein called three-finger toxin (3FTx), found in all elapid snakes, contains small regions that appear similar across species. Additionally, 3FTx proteins are thought to be highly toxic and responsible for whole-body paralysis, making them an ideal therapeutic target.
To discover an antibody that blocks 3FTx, the researchers created an innovative platform that inserted genes for 16 different 3FTx into mammalian cells and then produced the toxins in the laboratory. The team then consulted a library of more than fifty billion different human antibodies and tested which ones bound to the 3FTx protein from multibanded krait (also known as Chinese krait or Taiwanese krait) that was most similar to other 3FTx. squirrels This narrowed their search to about 3,800 antibodies. They then tested these antibodies to see which one recognized the other four 3FTx variants. Among the 30 antibodies identified in this analysis, the one with the strongest interaction of all the toxin variants stood out: an antibody called 95Mat5.
“We were able to raise a very small percentage of antibodies that cross-react against all these different toxins,” says Irene Halleck, a member of Scripps Research and first author of the new paper. “This was only possible thanks to the platform we developed to screen our antibody library against multiple toxins in parallel.”
Laboratory success and future directions
Jardine, Khalek and colleagues tested the effects of 95Mat5 on mice injected with toxins from the banded krait, Indian spitting cobra, black mamba and king cobra. In all cases, mice simultaneously injected with 95Mat5 were protected not only from death but also from paralysis.
When the researchers examined exactly how 95Mat5 blocked 3FTx variants so effectively, they discovered that the antibody mimicked the structure of a human protein to which 3FTx normally binds. Interestingly, the broad-spectrum HIV antibodies that Jardine has previously worked on also work by mimicking the human protein.
“It’s incredible that the human immune system has found a very similar solution to two completely different problems,” Jardine says. “It was also interesting to see that we were able to make an effective antibody completely synthetically; we did not vaccinate animals or use snakes.”
Although 95Mat5 is effective against the venom of all elapids, it does not prevent the venom of vipers, the second group of poisonous snakes. Jardine’s group is currently seeking neutralizing antibodies against two viper toxins as well as another elapid toxin. They suspect that combining 95Mat5 with these other antibodies could provide broad protection against most or all snake venoms.
“We believe that a cocktail of these four antibodies could potentially work as a universal antivenom against any medically relevant snake in the world,” says Khalek.