An article by Nicolas Wade in the Saturday, April 19 issue of The New York Times reported that scientists have discovered the precise mechanism by which HIV penetrates the membranes of cells.

Teams of scientists at the Whitehead Institute in Cambridge, Mass., and Harvard University have reported their results in the last two weeks.

In 1982, a London medical researcher found that a protein of the influenza virus had to change its shape before the virus could fuse with its target cell, the Times reported.

Three years ago Don C. Wiley of Harvard University reported the discovery of a virus “harpoon” in a protein of the influenza virus, according to the article. The discovery that HIV uses the same harpoon mechanism was announced last week from Cambridge.

The article stated the influenza virus, HIV, and a mouse leukemia virus have been found to use the same mechanism to invade cells, and it seems likely that many other viruses will be found to do so, too.

According to the article “many viruses are known to manufacture a pair of proteins with properties similar to the harpoon proteins of influenza and HIV. These include the viruses that cause measles and mumps.”

Wade’s article explained the mechanism as follows: “Essentially the harpoon protein is squashed down like a jack-in-the-box until some event, probably contact with the target proteins on the host cell, triggers its release. Since its tip is repellent to water but attracted to the fat found in cell membranes, the harpoon protein is able, when released, to thrust itself deep into the surface of the cell membrane.”

Peter S. Kim and colleagues at the Whitehead Institute performed an X-ray analysis of the pair of protein molecules that make up the harpoon mechanism in HIV. Their results were published last Friday in the journal Cell.

At Harvard University, Don C. Wiley and his colleagues were reported to have independently discovered the same harpoon mechanism as Kim’s team and to have discovered information about the “bottom” end of the harpoon as well as its tip. Their results have been submitted to the journal Nature.

Dr. Min Lu of Cornell University Medical College is credited with having originally demonstrated how to grow crystals of the HIV harpoon protein in large enough quantities to facilitate the X-ray structural analysis.

The Times’ article also explains that a protein associated with the harpoon enables HIV to recognize targets on the surfaces of the immune system’s T cells and macrophages. Just how the harpoon is triggered is central to the infection process, and knowing precisely how it happens “should help researchers design chemicals that clasp the harpoon or its components and blunt its action,” stated the article.

Dr. Robert Lamb, a virus expert at Northwestern University, was quoted as saying the new understanding was “highly important.” He said that although biologists have understood much of the chemistry by which HIV proteins recognize target proteins on the surface of target cells for several years, the new studies are original in addressing the actual change in shape of the HIV protein as the virus begins fusing with its host cell’s membrane.