Azerbaijan National Academy of Sciences

Frog mucus is loaded with molecules that kill bacteria and viruses, and researchers are beginning to investigate it as a potential source for new anti-microbial drugs. One of these "host defense peptides," courtesy of a colorful tennis-ball-sized frog species (Hydrophylax bahuvistara) from southern India, can destroy many strains of human flu and protect mice against flu infection, researchers report April 18 in the journal Immunity.

This peptide is far from becoming an anti-flu drug, but this is the first evidence of its flu-killing ability. It seems to work by binding to a protein that is identical across many influenza strains, and in lab experiments, it was able to neutralize dozens of flu strains, from the 1934 archival viruses up to modern ones. The researchers named the newly identified peptide "urumin," after the urumi, a sword with a flexible blade that snaps and bends like a whip, which comes from the same Indian province, Kerala, as the frog.

"Different frogs make different peptides, depending on where their habitat is. You and I make host defense peptides ourselves," says flu specialist and study co-author Joshy Jacob of Emory University. "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."

Practically all animals make at least a few anti-microbial host defense peptides as part of their innate immune systems, and researchers are only beginning to catalog them. However, frogs have drawn the most attention as a source of host defense peptides, because it's relatively easy to isolate the peptides from their mucus. Researchers can simply give the frogs a small electric shock or rub a powder on the frogs to make them secrete their defense peptides, which can then be collected.

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