Scientists Identify Protein that Blocks HIV Entry into Immune Cells
Scientists from the Massachusetts Institute of Technology and the Howard Hughes Medical Institute have developed a protein called 5-Helix, which blocks HIV from latching onto healthy immune cells, the Guardian reports (Radford, Guardian, 1/12). Led by MIT biologist Peter Kim, who was recently selected to head Merck & Co.'s research division, the researchers report in Science that the discovery may be used as a "last-chance therapy" against HIV for patients who are resistant to currently available treatments, the Wall Street Journal reports. HIV uses a "trio of hairpin-like extensions" to grab onto white blood cells (Regalado, Wall Street Journal, 1/12). The 5-Helix protein "jam[s]" the "grappling hook[s]" that HIV uses to invade healthy cells, and if HIV cannot fuse with the cell's outer wall, it cannot enter the cell and "hijack its machinery" in order to replicate itself (Guardian, 1/12).
A New Class of Treatment?
Trimeris Inc. and Hoffman-La Roche have already developed the compound T-20, which is able to block the adhesion to immune cells of the "hairpin molecule" gp41 and is in human clinical trials in the United States, Europe and Australia. The companies have received FDA "fast-track" status and expect the drug to be on the market by mid-2002 if the trials are successful. Dr. Kim said that 5-Helix may be "more effective" than T-20 and other "fusion inhibitors" that represent "salvage therapy" for patients who are resistant to current antiretroviral drugs or cannot handle drug side effects (Wall Street Journal, 1/12). T-20 is synthetically created through a chemical process, while 5-Helix was developed by "manipulating" bacterial genes to produce the protein. Proteins are cheaper to produce and "more resistant to degradation" than synthetics once they have entered the body (Associated Press, 1/12). T-20 is also a "relatively large" molecule and must be injected into the bloodstream. But 5-Helix is a "much smaller molecule," which might be able to be produced in a "cheaper and easier" pill form (BBC News, 1/12). However, Reuters Health reports that "due to the nature of the protein ... any such drug would have to be injected" (McKinney, Reuter's Health, 1/11). The protein has yet to be tested in animal trials, but if successful, "the difficult and arduous process of developing it for humans could take place," Kim added. 5-Helix drugs may prove effective against other viruses such as Ebola and flu, which use similar strategies to infect cells as does HIV (Guardian, 1/12).