Researchers have designed a protein that can inhibit HIV infection by blocking the virus's entry into cells. This protective protein, known as 5-Helix, binds to a vulnerable region of an HIV coat protein called gp41, thus preventing the virus from fusing with membrane of the cell it is attacking and infecting it. What's more, 5-Helix appears to effectively thwart a wide range of HIV strains. As such, it may serve as the basis for developing a new class of anti-HIV drugs. Alternatively it could be used in prophylactic treatments (say, after an accidental needle prick in a hospital), or perhaps as a vaccine. A team led by Peter S. Kim of the Whitehead Institute for Biomedical Research describe their discovery in a report that appears today in Science.

Kim and his colleagues have been investigating gp41 for years, knowing that this HIV protein plays a critical role in enabling the virus to fuse its membrane with that of its target cell. With that in mind, they fashioned 5-Helix, which binds to specifically and tightly to gp41. Another so-called entry inhibitor, T-20, showed promise, but large quantities were required to achieve positive results in patients. 5-Helix, in contrast, seems effective even in low concentrations. The new protein may even pave the way to combating other viruses like Ebola, human respiratory syncytial virus (HRSV) and the flu--all of which employ a fusion strategy similar to that of HIV.

Having determined that 5-Helix inhibits HIV in cell culture, researchers must now ascertain whether it works in an animal model. If so, they could then begin to develop it for humans. "Current therapy is working," Kim observes, "but sexual transmission of virus that is resistant to treatment has been documented, making it important to continue to find new targets and therapies for stopping HIV."