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Rare Blood Cells Found In Carriers Who Beat Aids

Fri., Nov. 21, 1997

Some rare patients infected for years with the AIDS virus without becoming ill make white blood cells of a type missing from most patients of the immune system disorder, researchers say.

An analysis of blood from a Boston man infected with HIV for 18 years but still healthy showed that he was protected by a large number of immune system cells, called helper T-cells, that specifically attack the AIDS virus.

Most patients with long-term HIV infection have a low supply of helper T-cells targeting the AIDS virus, which leaves the immune system defenseless against the virus, Dr. Bruce Walker of the Massachusetts General Hospital said. He is senior author of a study being published today in the journal Science.

“Our work provides an explanation of why a very small group of people have been able to avoid getting sick from this virus even though they are infected,” said Walker.

Helper T-cells direct the body’s immune system. A variety of the cells exist, and each type is primed to attack a specific virus or other invader. As these cells detect the presence of a target virus, they reproduce by the billions, flooding the bloodstream with defenders.

But HIV, the AIDS virus, has broken down this defense. For reasons not understood, helper T-cells specific for HIV often are at low levels in or absent from patients infected with the virus.

Experiments at Massachusetts General confirmed that high levels of HIV-specific T-cells may be essential for the body to hold the AIDS virus in check.

Walker said laboratory tests of blood from HIV patients found that those with the strongest T-cell response to the HIV antigen had the lowest amount of virus in their bloodstream, but those with weak T-cell responses had high virus loads.

The discovery suggested the body might be able to control HIV if helper T-cells that target the virus could somehow be protected.

To test this idea, researchers used powerful anti-viral drugs to treat patients recently infected with HIV. Walker said the drugs caused the virus load to drop quickly, and the patients’ immune systems then started producing T-cells that specifically attacked HIV.

Walker said the HIV-specific T-cells were not produced in the bodies of patients who had been infected with HIV for more than six months.


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