The Associated Press - Wednesday, September 13, 1989

About 300 researchers from federal, university and commercial laboratories met at the National Academy of Science headquarters to discuss what "markers" -- or characteristics in the blood of AIDS patients -- could be used to gauge how fast the disease is infecting the immune system, and how well new AIDS drugs are fighting the virus.

If an agreement is reached and approved by the Food and Drug Administration, experts said that it could lead to the use of a laboratory blood test that would swiftly determine progress of the AIDS virus infection in a patient. This, in turn, would help measure the effects of drugs to combat the disease.

Stages of infection by HIV, the human immunodeficiency virus that causes AIDS, are now measured by clinical effects, such as the development of opportunistic infections, or wasting, or by chronic lymph node enlargement. These are called "clinical end points," and they often can take months or years to develop.

But Dr. Samuel Broder, director of the National Cancer Institute and a leading AIDS drug researcher, said that scientists are becoming confident enough about their knowledge of AIDS to consider using a test that could be performed long before the clinical end points appear. A marker in such a test would be called a surrogate, or substitute, end point.

A number of investigators believe that the progress of AIDS can be accurately measured by testing the blood for the number of CD4 lymphocytes. These cells -- often called T-4 cells -- are part of the immune system, but they also are the primary target of the AIDS virus.

Normally, humans have 800 or more CD4 cells per cubic millimeter of blood. But once the AIDS infection becomes active, this number begins to drop. CD4 cell counts of less than 200 reflect an immune system that is in serious trouble.

Dr. Tony Fauci, director of the National Institute of Allergy and Infectious Diseases, a lead agency in the federal war on AIDS, believes that the CD4 blood test should be used as a marker for progress of the disease.

"I've made my position pretty clear," said Fauci. "I believe it is quite a good surrogate marker. But we don't operate alone."

Fauci said a committee of the Institute of Medicine, which is chartered by the National Academy of Science, will develop a recommendation to the Food and Drug Administration for a possible surrogate end point lab test for AIDS.

The FDA, however, would have to approve the recommendation before drug researchers could use the surrogate end point in drug testing.

A spokesman at the Institute of Medicine said a report from the committee will take about six months.

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