Scientists at Washington University School of Medicine have identified a way that some viruses protect themselves from the immune system’s efforts to stop infections. The finding may make possible new approaches to treating viral infections. The study was recently published in Science Express.
Viruses can slip past the immune system by faking or stealing a molecular “identification badge” that prevents a cell from recognizing a virus. The researchers found that some viruses have another trick: they can block the immune system protein that checks for the identification badge. The blocking structure is called a stem-loop, found at the beginning of the virus’s genetic material. This is the first time scientists have found an immune-fighting mechanism built directly into the genetic material of a virus. They are looking for ways to disable it and searching for similar mechanisms that may be built into the genetic material of other disease-causing microorganisms.
The researchers studied alphaviruses, RNA viruses that cause fever, encephalitis, and infectious arthritis. They showed that a single-letter change in the RNA of an alphavirus strengthened the stem-loop. When the structure was stable, a key immune system protein called Ifit1 was blocked from binding to the viral RNA and the infection continued unchecked. But when the stem-loop was unstable, Ifit1 would bind to the viral RNA and disable it, stopping the infectious process.
“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,” says senior author Michael Diamond, MD, PhD. “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. Read the abstract.
