French experts find key molecule in AIDS research Discovery spurs hopes of vaccine


Discovery of a natural molecule that the AIDS virus uses like a trapdoor to invade white blood cells was reported by French researchers, who hope it will lead to vaccines or treatments for AIDS.

According to a report released yesterday by the Pasteur Institute at a news conference in Paris, virologist Ara Hovanessian's research team isolated a co-receptor that the AIDS virus uses in tandem with the well-known CD4 receptor.

The CD4 cells -- white blood cells bearing CD4 surface molecules -- are the major target of the AIDS virus. It has been known that the virus needs to find CD4 molecules so it can anchor itself to blood cells. But it was not known what happens next, exactly how the virus worms its way into the cell to cause disease.

Dr. Hovanessian's find -- a molecule called CD26 -- apparently answers that question. It is an enzyme that opens a portal so the virus can slip inside.

Virologist Max Essex, head of the Harvard AIDS Institute in Boston, said the discovery "sounds both interesting and important. It's been known by everyone for a long time that CD4 was necessary, but not sufficient," for the AIDS virus to infect cells. "But no one had come up with a clear reason why," Dr. Essex said.

Dr. Essex and other American scientists would not say more because they had not yet read the French team's report. A formal report on Dr. Hovanessian's work is to be presented today at a special AIDS meeting in Versailles, France.

Dr. Hovanessian said that using inhibiting molecules to block activity of the new CD26 receptor might be a way to keep the virus from binding properly. Laboratory experiments showed this might work, he said. "We have done a series of experiments using inhibitors and antibodies specific to the CD26 molecule."

Immune system molecules called antibodies can also be used to prevent proper contact between the virus and the cell's receptors, similar to filling the glove before the hand can get in.

However, neither of these approaches worked when researchers tried it with the better-known CD4 molecules.

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