Mystery Anti-HIV Factor Unmasked?

Sixteen years ago, in the relatively early days of the AIDS epidemic, virologist Jay Levy of the University of California (UC), San Francisco, proposed an answer to one puzzle about the AIDS virus and created another. He had tantalizing evidence that immune system cells secrete a chemical that can stop HIV, and he suggested that HIV- infected people who have high levels of this factor could live for decades without damage to their immune systems. This would explain in part why HIV kills at such disparate rates. But just what is the mystery factor? Legions of AIDS researchers have searched for this treasure, unearthing half a dozen different candidates, none of which has been completely convincing. Now a team led by Linqi Zhang and David Ho of the Aaron Diamond AIDS Research Center in New York City claims to have the elusive factor in hand. But other researchers who have been digging for answers and have seen the new data say they're not throwing away their shovels.