It sounds like a cheapjack Harry Potter potion, but slime from this colorful little frog could help people fight the flu.
A chemical compound in the skin-secreted mucus of this South Indian frog can kill the H1 strain of the human influenza virus, as shown by a new study published in the journal Immunity.
The compound is a peptide, a short chain of amino acids, that the researchers named “urumin” after a traditional south Indian sword. They obtained urumin, along with a few other potential compounds, by heading down to Kerala in southern India and gently zapping Hydrophylax bahuvistara frogs with a mild electric shock. This frog species itself was only discovered by science in 2015.
"Different frogs make different peptides, depending on where their habitat is. You and I make host defense peptides ourselves," flu specialist and study co-author Joshy Jacob of Emory University said in a statement. "It's a natural innate immune mediator that all living organisms maintain. We just happened to find one that the frog makes that just happens to be effective against the H1 influenza type."
When they took the skin secretions back to the lab, they isolated 32 peptides and discovered that four had “flu-busting abilities”. They work by targeting the surface protein called hemagglutinin, aka the H in H1N1, which acts a bit like a key to get into our cells and infect us. By binding this, it ruins the integrity of the virus, rendering it useless while leaving the cell intact.
"I was almost knocked off my chair," added Jacob. "In the beginning, I thought that when you do drug discovery, you have to go through thousands of drug candidates, even a million, before you get 1 or 2 hits. And here we did 32 peptides, and we had 4 hits."
The scientists put these four peptides onto human red cells and watched what happened under an electron microscope. Annoyingly, three proved to be toxic to human cells, but the fourth – urumin – left them totally unaffected. Further tests showed that unvaccinated lab mice given a dose of urumin were protected against lethal doses of some flu viruses.
Current antiviral drugs are susceptible to drug resistance, so finding new antivirals is essential, the study notes. But as cool as this discovery is, there’s still a lot of work to be done until it is fine-tuned into a viable drug. It’s worth noting that it doesn’t kill all strains that are a bother to humans, such as H3N2.
Nevertheless, this optimistic story underpins a very real need for us to maintain the world’s biodiversity. After all, you never know which frog you'll need in the coming years of antibiotic-resistant superbugs.