Researchers at the University of Cambridge and the University of Oxford have discovered a new molecule that plays a key role in the immune response that is triggered by influenza infections.
The molecule, a so-called mini viral RNA, is capable of inducing inflammation and cell death, and was produced at high levels by the 1918 pandemic influenza virus.
The findings appear in Nature Microbiology.
Influenza is one of the main infectious diseases in humans.
Seasonal influenza viruses account for about 650,000 deaths per year, whereas pandemic strains such as the 1918 H1N1 virus have been linked to 50-100mn deaths worldwide.
Highly pathogenic avian influenza viruses such as the H5N1 and H7N9 strains have a mortality rate of about 50% in humans.
The reasons for difference in disease severity and lethality caused by seasonal influenza viruses on the one hand, and a pandemic and highly pathogenic avian influenza virus on the other hand, is still poorly understood.
Previous research has indicated that in infections with the 1918 pandemic virus or infections with an H5N1 avian virus, a powerful immune response is established that leads to death.
This led Professor Ervin Fodor and his colleagues Dr Josh Long and Dr David Bauer of the University of Oxford, and Dr Aartjan te Velthuis of the University of Cambridge, to ask what viral molecule can trigger this powerful immune response.
The British groups first looked to how viruses are detected by the cell.
Normally, an infected cell spots the presence of a virus by sensing the genetic material of the virus, RNA in the case of flu.
Work by Prof Richard Randall, a collaborator on the manuscript from the University of St Andrews, has shown that influenza viruses are good at hiding their RNA.
This observation prompted Fodor and his colleagues to look for flu RNA that the virus was not able to hide from the cellular pathogen sensing system.
What they found was truncated pieces of the viral genome that the virus had produced in error.
The researchers called these pieces mini viral RNAs.
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