
                         Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: TUESDAY, December 14, 1993                   TAG: 9312140064
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A6   EDITION: METRO 
SOURCE: Associated Press
DATELINE: WASHINGTON                                LENGTH: Medium

SCIENTISTS PROBE CAUSE OF RESISTANCE TO AIDS

Scientists studying why some people fight the AIDS virus better than others speculated Monday that these people have very specialized immune cells that can recognize the virus's disguises.

Research into these T-cells is in the very early stages, but it could explain why a very few people infected with HIV, the AIDS virus, have lived healthy lives for more than a decade while others succumb quickly.

"How you do depends on whether your T-cell recognizes what your virus shows it," said Dr. Robert Schooley, who is chairman of a national conference on AIDS and related viruses in Washington this week. "The tricky part is: Can we modify that somehow to boost your response?"

Cytotoxic T-cells are the body's killer cells - they attack disease as soon as they recognize it.

In a person infected with HIV, the virus enters a cell and waits until some still unknown mechanism triggers it to replicate, sending various proteins and peptides out of the cell.

Different strains of the virus emit different proteins in different people at different times. If the T-cells don't recognize them as a sign of disease, they won't attack.

But new research suggests some people have T-cells that specifically target certain HIV proteins, particularly those known as the envelope and gag proteins, and thus do better at fighting the disease.

Dr. Thomas Harrer of Harvard Medical School is studying HIV-infected people who have remained healthy for over 12 years without taking AIDS drugs. Ten of these people, the first with complete data, have high levels of immune cells that are HIV-specific in their blood, he said Monday.

Also, some T-cells specifically bind to certain epitopes, the coatings on cells to which peptides cling. Harrer is finding several unique epitopes in long-term HIV survivors.

So the question becomes: Do these people have genetically superior T-cells, or do those cells combine with certain epitopes to offer protection against full-blown AIDS?

There's not enough data to begin answering either question, Harrer emphasized. "We haven't even proven that T-cells are the only link to these people's survival. There could be other co-factors we don't know about," he said.

by CNB