Cell That Destroys AIDS Virus Discovered

Researchers said Wednesday they have identified a type of cell in blood that seeks out the AIDS virus and destroys it, a discovery that may explain why some infected people go on to develop the disease while others do not.

The newly discovered killer cells, called cytotoxic T lymphocytes, may also aid in the development of a vaccine against the deadly disease, said doctors at Massachusetts General Hospital who made the discovery.

“We have yet to determine what role these (killer cells) play in the body,” said Dr. Bruce D. Walker, at a news conference held in the hospital. “We do know they can identify and kill cells expressing the AIDS virus.”

Walker said it appears the body manufactures the killer cells after being exposed to the HIV virus that causes acquired immune deficiency syndrome. In his study, eight patients known to have been infected with the AIDS virus were shown to have the killer cells in their blood while five others in a control group did not.

In response to viral infections of any type, the body normally produces both antibodies and killer cells to fight the invasion, doctors said.

In AIDS, researchers quickly identified the antibody to the virus but had trouble determining the presence of killer cells.

The researchers at Massachusetts General, in collaboration with scientists at the National Institutes of Health, finally discovered evidence of the killer cells by a roundabout process in which they took a smallpox virus and spliced into it genes from the AIDS virus.

In a laboratory, the researchers then mixed the new virus--which exhibited all the hallmarks of the HIV virus--with blood from AIDS victims and measured the ability of cells to identify and kill it.

The killer cells were found in all eight of the AIDS-infected study group, the researchers said. But some of the individuals had more killer cells than others.

“There is more (killer cell) activity in people who are healthier, but we don’t know which came first,” better health or more cells, said Dr. Robert T. Schooley, another researcher.

He said the doctors plan to follow the eight study subjects, measuring the amount of killer cells they have in their blood and watching to see which develop the disease.

Schooley said the new discovery will also help drug companies and private researchers who are attempting to develop an AIDS vaccine.

He said scientists will now be able to determine whether a potential vaccine has the ability to create the killer cells, as well as antibodies.

Human trials on potential vaccines are expected to begin as early as the end of the year, the researchers said.

The results of the study were published in the British science journal Nature.