For nearly 20 years, scientists have labored under the assumption that the influenza virus comprises only 10 protein molecules that form its structure and carry out its activities. However, this week in Nature Medicine researchers report finding a new, "hidden" influenza virus protein. This protein may kill immune system cells that fight the virus, thereby contributing to the virus's potency, the researchers say.
"We believe this is a groundbreaking finding, although we're not yet sure how deep the ground is," says Jonathan Yewdell, M.D., Ph.D., a viral immunologist who led a team of scientists at the National Institute of Allergy and Infectious Diseases (NIAID). "This might be the 'grand canyon' of the flu, in terms of understanding this virus's virulence, or perhaps only a narrow side ravine."
The scientists turned up this new protein by accident, while sifting through bits and pieces of "junk" peptides. Junk peptides are short protein molecules the virus creates once it infects a cell and begins replicating. They form when the process that translates viral genes into proteins goes awry, Dr. Yewdell explains. In other words, junk peptides result from genetic mistakes.
"We weren't looking for new proteins at all. We assumed the 10 known influenza proteins were all there were," Dr. Yewdell says. "We just wanted to know if immune system cells had learned to recognize any of these junk peptides. We thought that was an interesting question."
The immune system cells of mice, in fact, did recognize one of the peptides. When the scientists examined the gene encoding this peptide more closely, they noticed it was "suspiciously long" for mere junk. Wondering if this molecule might be a bona fide protein, Dr. Yewdell's team decided to see how much of it was created in cells infected with the flu virus. If it were junk, there should be only a few random copies of the peptide here and there. If it were a protein, large qu
Contact: Jeff Minerd
NIH/National Institute of Allergy and Infectious Diseases