A component of the skin mucus secreted by a frog species found in India can be harnessed to kill influenza viruses, new research has found.

In their experiment, the researchers found that when delivered intranasally, one of the antiviral peptides found in skin secretions from the Indian frog Hydrophylax bahuvistara can kill H1 variety of influenza viruses that can affect humans. The research, carried out by researchers from Emory University in the US and Rajiv Gandhi Centre for Biotechnology in Thiruvananthapuram, also showed that the compound can protect unvaccinated mice against a lethal dose of some flu viruses. 

The researchers believe that the compound has the potential to contribute to first-line anti-viral treatments during influenza outbreaks. Frogs' skins were known to secrete "host defense peptides" that defend them against bacteria.  The new finding, published in the journal Immunity, suggests that the peptides represent a resource for antiviral drug discovery as well.

Anti-flu peptides could become handy when vaccines are unavailable, in the case of a new pandemic strain, or when circulating strains become resistant to current drugs, said senior author Joshy Jacob, Associate Professor of Microbiology and Immunology at Emory Vaccine Center and Emory University School of Medicine in Atlanta, Georgia, US.

Jacob and his colleagues named the antiviral peptide they identified urumin, after a whip-like sword called "urumi" used in southern India centuries ago.  Urumin was collected for the study after mild electrical stimulation of the frog. Peptides are short chains of amino acids, the building blocks of proteins. Some anti-bacterial peptides work by punching holes in cell membranes and are thus toxic to mammalian cells, but urumin was not.

Instead, urumin appeared to only disrupt the integrity of flu virus, as seen through electron microscopy.  It binds the stalk of hemagglutinin, a less variable region of the flu virus that is also the target of proposed universal vaccines, the study said. This specificity could be valuable because current anti-influenza drugs target other parts of the virus, Jacob said. Urumin was specific for H1 strains of flu, such as the 2009 pandemic strain, and was not effective against other current strains such as H3N2, the study pointed out.