On average, the number of age-standardized deaths from venomous animal contact per year is 100.000 people. Unfortunately, for residents of north-east Queensland, their chance of not being in this 100.000 is low thanks to Comana monomorpha also known as the electric caterpillar. Its sting, typically received while tending to lilly-pillies in gardens, is excruciatingly painful. This little creature's venom causes a nasty welt and a rash that can last a week. It’s so painful that some victims have had to spend a whole night in emergency departments. Some health professionals who have treated victims of this green devil have seen swelling, blood-filled boils, and welts. However, they could not find anything to help ease the pain. Luckily, scientists have succeeded and believe they can use its toxin to heal such damages.
Andrew Walker is a molecular entomologist at the University of Queensland’s Institute for Molecular Bioscience and has characterized the venoms of some of the world’s least-studied venomous animals including centipedes, assassin bugs, and several caterpillars. Along with Walker, Glenn King, an affable biochemist leading the Institute’s “bugs and drugs” group has collected venom from more than 500 species, building an unrivaled collection of animal toxins. “This is by far the biggest invertebrate venom library in the world – probably the biggest venom library in the world,” King said. Given that it includes venoms from Australian tarantulas, a Brazilian caterpillar, and the lethal funnel-web spider, it might even be considered the most deadly library in the world. However, researchers like King and Walker aren’t interested in venom’s ability to kill: Instead, they want to use it to heal.
To achieve this, scientists identify key molecules in venom that interact with ion channels in the body which allow specific inorganic ions (primarily Na+, K+, Ca2+, or Cl) to diffuse down their concentration gradients across the lipid bilayer. By doing this, they hope to uncover molecules that can target those channels, ultimately leading to the creation of target therapies. A venom library supercharges this process, allowing researchers to screen hundreds of venoms at once and identify promising candidate molecules. “We can apply [the library] to virtually any human disorder where we think an ion channel might be involved in the disease.”, King said.
Using the venom library, scientists have characterized the venom of a subspecies of the funnel-web spider, discovering a peptide with potent physiological effects. Known as Hi1a, the protein blocks a signaling pathway that orders cells to die when there’s a lack of oxygen. When given to patients who have suffered a heart attack or stroke, Hi1a could protect against extensive, lasting damage. “My idea was that, if you went to a different group of animals that had evolved venom independently, then you would start to see very different types of molecules,” he stated.
Walker’s work with caterpillars is at a much earlier stage than the group’s funnel-web studies. Spiders are generally much larger than caterpillars, therefore producing a lot more venom. The typical amount after milking a spider can be measured in microlitres, while venom extracted from caterpillars is measured in nanolitres (a microliter is 1000 times a nanoliter). King said it would have been impossible to study this amount of venom if technological advances had not enabled researchers to identify peptides from minuscule volumes. This research has resulted in a few surprises: For instance, caterpillar venoms were predicted to contain simple peptides and proteins because they’re used purely for defense. However, Walker’s studies have shown that the molecules produced in caterpillar toxins are much more complex than expected. In the case of the asp caterpillar (a moth larva that looks like a toupee), Walker found that it may have acquired its toxic capabilities via gene transfer with bacteria that existed many millions of years ago. In research yet to be published, he suggests that the electric caterpillar may have undergone a similar process. Both species contain venoms that are rich in molecules and are able to punch holes in a cell membrane, causing an attacking animal to feel pain.
These proteins offer the potential for developing new insecticides and therapeutics. Similar molecules have been used to protect crops from pests, and some are being explored as drug delivery systems into cells. While the electric caterpillar may not produce such significant results, Walker emphasizes that understanding its venom composition has immediate benefits, especially for residents of north-east Queensland.