A powerful "second-generation" anti-AIDS drug could be available within a decade, say scientists who helped identify the precise target where the AIDS virus latches onto cells it destroys.

The study by scientists at the California Institute of Technology here, Ortho Pharmaceuticals in Raritan, N.J., and the University of Alabama, Birmingham, was published Friday in the journal Science.The study's chief authors, Caltech molecular biologist Bradford Jameson and protein chemist Stephen B.H. Kent, discouraged excess optimism that their discovery would lead to a drug to treat or cure acquired immune deficiency syndrome, which cripples the body's disease-fighting immune system.

"We do not want to give people false hope," said Kent. Nonetheless, he said, a drug more effective than those now being developed could be available in 10 years.

However, Dr. Mathilde Krim, a founder of the American Foundation for AIDS Research, said Kent was exaggerating the time it would take to develop a drug using the new discovery.

"If things go very well, I'd say two years until it would be made available to people," Krim, whose organization funded the $120,000 study, said by phone from New York City.

"To my knowledge, it is the first time a binding site has been identified with such precision for any virus," Krim said. "It's a wonderful accomplishment."

Scientists previously knew the AIDS virus infects T4 white blood cells and certain other cells by attaching to CD4, a "receptor" protein on the cells' surface. T4 cells are the main immune-system cells destroyed by AIDS.

Using sophisticated analyses, Jameson identified the exact part of the CD4 protein to which the AIDS virus attaches, known as a "binding site."

In the next step, crude synthetic copies of the binding site were manufactured by Jameson, Kent and Caltech biology chairman Leroy Hood.

Alabama scientists found that in the test tube, the fake binding sites acted as decoys to overwhelm AIDS virus particles so they couldn't latch onto real binding sites on T4 cells.

If scientists can create more sophisticated versions of the fake binding site, those might work as a drug to treat or cure AIDS, or to carry virus-killing drugs to the AIDS virus, Kent said.