In a revolutionary discovery, scientists at the Washington University School of Medicine have uncovered the way in which viruses avoid detection by the body’s immune system. Such a development presents exciting potential for treatment development against viral infections.
It has long been known that viruses can slip past the immune system by stealing a molecular identification badge, preventing them from being recognised. Now scientists have learnt that viruses also contain a structure that blocks the immune system protein that checks for such identification badges. The discovery of this structure, called a stem loop, is the first time that scientists have found an immune-fighting mechanism built directly into the genetic material of a virus.
Identifying such a mechanism means that research can now begin on methods to disable it, in addition to searching for similar mechanisms in other disease-causing microorganisms. It is hoped that this discovery can be used to tackle viruses such as the influenza virus and yellow fever. These viruses are particularly problematic as they are able to encode their genes directly in RNA.
Researchers at the university studied alphaviruses, a group of RNA viruses that cause infectious arthritis, fever and encephalitis. Through their work, it was shown that a single letter change in the RNA of the alphavirus strengthens the stem-loop. When this structure was stable, the immune system protein was unable to bind to the virus and the infection remained unchecked. It was only when the stem-loop is unstable that the infectious process is disabled by the immune system.
“When the stem-loop is in place and stable, it blocks a host cell immune protein that otherwise would bind to the virus and stop the infectious process,” said senior author Michael Diamond. “We found that changing a single letter of the virus’s genetic code can disable the stem-loop’s protective effects and allow the virus to be recognized by the host immune protein. We hope to find ways to weaken the stem-loop structure with drugs or other treatments, restoring the natural virus-fighting capabilities of the cell and stopping or slowing some viral infections.”
He also added: “Knowing about this built-in viral defence mechanism gives us a new opportunity to improve treatment of infection. To control emergent infections, we must continue to look for ways that viruses have antagonized our natural defence mechanisms and discover how to disable them.”