Researchers find a new way HIV cripples immune system Discovery might lead to improvement in existing AIDS therapy

March 17, 1998|By Douglas M. Birch | Douglas M. Birch,SUN STAFF

Researchers at Baltimore's Institute of Human Virology have discovered another way that the virus that causes AIDS cripples the body's immune system.

In a paper in this month's Proceedings of the National Academy of Sciences, a group of scientists at the institute show, for the first time, how the human immunodeficiency virus can infect and disable an important component of the immune system, so-called "killer" T cells.

While the long-term implications of the finding aren't clear, Dr. Robert C. Gallo, director of the institute, said the discovery might lead to improvement in an existing therapy for acquired immune deficiency syndrome.

Killer T cells are equipped to attack viruses, both by destroying infected cells and by releasing chemicals in the blood. But HIV eludes them by making sure they aren't alerted to its presence. In part, it does this by attacking and destroying a type of immune cell called a "helper" T cell, which alerts the immune system about viral invaders.

Scientists already knew that the number of killer T cells declines in the latter stages of AIDS, but most blamed it on other factors, including the triggering of cell suicide.

Now, institute researchers have evidence that, as they become activated, killer T cells briefly sprout a molecule also found on the surface of helper T cells.

That molecule acts as a docking port for the free-roaming AIDS virus. And, researchers say, HIV seems to use the molecule as a port to infect killer T cells.

Gallo, one of the paper's authors, said there is no evidence that the killer cells need to sprout the molecule in order to do their job.

In one treatment strategy, doctors have harvested killer T cells from AIDS patients early in their infection, stored the cells and then injected them back in the same patients later in the disease.

But this strategy hasn't worked very well, perhaps because AIDS infects these cells as they become activated.

Using genetic engineering, "we may be able to manipulate" the killer T cells so they don't become vulnerable to HIV when they are activated, Gallo said.

Pub Date: 3/17/98

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