A substance isolated from the skin of a frog can potently destroy influenza virus particles, scientists in the US have discovered.
Appropriately dubbed urumin, after the Indian word "urumi", which means a whip-like sword, the new agent slices, dices and deactivates flu.
Together with his colleagues, David Holthausen, from Emory University in Georgia, has been screening molecules known as "host defence peptides" - HDPs for short - secreted onto its skin surface by Hydrophylax bahuvistara, a species of red, black and yellow striped frog native to southern India.
The role of HDPs is to protect the animal by neutralising a range of microbial threats. Holthausen and his team isolated 32 different HDP molecules which they set about screening for anti-flu activity.
Four of the chemicals potently destroyed flu, although three of them were also highly toxic to human cells. But one of the agents - urumin - which comprises a string of 27 amino acid building blocks, showed powerful anti-flu activity but was also apparently harmless at the same dose to human blood cells.
The Emory team tested the substance against 12 different flu strains representing the common circulating types of the virus, including 8 forms of H1N1 and 4 isolates of H3N2 collected during the last 75 years of flu circulation.
While only marginally effective against H3N2 viruses, urumin nevertheless produced a 60-90% inhibition of the growth of all 8 strains of H1N1.
Mice given a lethal dose of flu followed by an intranasal dose of urumin were significantly protected, with 70% of the animals surviving compared with 20% of controls.
Studies on the animal's lungs also showed that treated mice subsequently had 80-90% lower virus activity in their respiratory tissues compared with untreated mice.
At the moment the researchers do not know precisely how urumin works, but microscope studies show that contact causes viral particles to disintegrate.
The peptide binds to part of the viral coat known as the HA in a region that is very heavily conserved across time, as evidenced by the fact that even viruses that were infecting people 75 years ago remain susceptible to its effects.
This broad spectrum of activity, say the researchers in their paper published in the journal Immunity this week, means that urumin "therefore has the potential to contribute to first-line anti-viral treatments during influenza outbreaks."
The next steps will involve deducing exactly how urumin is working. What's exciting is that it appears to be killing flu in a way that is entirely novel to science.
So, once the mechanism is understood, it is likely to reveal new therapeutic avenues that researchers can pursue to make a range of novel anti-influenza drugs.
Isn't nature incredible...
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