A part of the AIDS virus that was considered vulnerable to attack can camouflage itself by changing shapes, according to a new study that helps show why HIV is so hard to target and kill. HIV uses a protein on its surface called gp120 to latch onto and infect immune system cells. In 1998, scientists announced that they had figured out much about the structure of gp120 and hoped that finding a vulnerability in it could lead to vaccines against HIV. Some scientists believed that the best hope was in targeting an area of gp120 common to all strains--a vulnerable region where the protein must expose its core in order to bind to a T cell.
But new research shows that this region is more elusive than previously thought, because it is composed of very flexible parts that let it take on different shapes that camouflage gp120 against antibodies launched by the immune system as a defense. "There's a lot of mobility within the protein. It's a blurry, moving structure that is very difficult for the immune system to deal with," said researcher Jospeh Sodroski of Boston's Dana-Farber Cancer Institute in the December 12 issue of the journal Nature. Theodore Jardetzky, a Northwestern University molecular biologist, called the findings surprising. "How big a deal this is, we're going to have to wait and see," he said. "They've pointed us in a new direction."