Chicago Tribune (CT) - THURSDAY, June 29, 1995 Edition: NORTH SPORTS FINAL Section: NEWS Page: 14 Word Count: 533
Anita Srikameswaran, Tribune Staff Writer

Using advanced techniques for analyzing the condition of human cells, researchers believe they now can tell how many cells in a patient are infected with the human immunodeficiency virus that causes AIDS.

And, they said, doctors don't need a specialized lab to do it.

"We have never been able to easily measure it before," said Dr. Bruce Patterson, a Northwestern physician and virologist who led the team. "This is the first time it has been done."

In light of their work, published recently in the Journal of Virology, it may be necessary to establish new treatment guidelines for HIV-positive patients.

Patterson and colleagues reported using a combination of methods from genetics and immunology to identify and count cells infected with the AIDS virus, thus measuring what scientists call the viral burden of HIV.

HIV primarily attacks T4 cells, a type of infection-fighting white blood cell, by attaching to areas on the cell surface called CD4 receptors. Once inside, the virus makes itself part of the human DNA. Eventually, the infected cell dies.

Because T4 cells are essential in defending the body against other infections, the patient's ability to fight off diseases plummets as these cells perish.

Doctors currently monitor the danger of HIV by counting how many cells with CD4 receptors are left because the viral level cannot be measured directly. The problem, explained Patterson, is that not all cells with CD4 receptors are infected with HIV. Two patients may have the same cell counts but have varying numbers of infected cells, he said. If they have different symptoms, it could be the result of differing viral levels.

Now, according to the Northwestern researchers, it is possible to accurately assess the spread of the virus in each patient, how compromised an individual's immune system is and, thus, who is in imminent danger of getting sick.

In their technique, the researchers poke holes in T4 cells that are soaking in a broth of radioactively tagged DNA fragments. If HIV particles are present inside the cell, the bits of DNA bond with them.

The solution glows when passed through the laser eyes of a machine called a flow cytometer. Researchers measure the glow to determine the degree of infection.

Experts predicted that the impact of the Northwestern technique would be considerable.

"It's very potent because it can be easily used by even unsophisticated labs," said Dr. Roger Pomerantz, infectious disease specialist at Philadelphia's Thomas Jefferson University.

He recommended that past studies be repeated using the new measuring stick to evaluate the efficacy of drug therapy.

Drug management should be based on the patient's viral level, rather than on the traditional T4 cell count, Pomerantz said. Science now may have a way to determine that level.

A re-examination of studies also could explain why patients do not suffer identical rates of deterioration after HIV infection, Pomerantz said.

While the assault on the body's defenses remains to be overcome, the new lab technique "will mean better anticipation of immune system compromise and better care for HIV-positive patients," according to Northwestern's Patterson.

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