Hormone clue to mystery of Aids

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What happens if you put male mice in a cage with female mice? If you are researchers into HIV, the virus that causes Aids, then you come up with clues to a potential treatment for the infection. And, bizarre though it might sound, it also involves pregnant women.

According to Robert Gallo, one of the world's leading Aids researchers, the clues to the new treatment came about by accident - "or, as my colleague said, good observation of an inadvertent experience".

In an experiment in which mice were injected with malignant cells from Kaposi's sarcoma, a skin cancer common in Aids patients, a researcher accidentally put male and female mice in a cage together. Subsequently, he found that female mice which were in the early stages of pregnancy when they were inoculated with the malignant cells did not develop tumours.

Dr Gallo, director of the Institute of Human Virology, said that his team - which had carried out the Kaposi's experiment - then tried to find a hormone produced in women at the same stage of pregnancy, and discovered one which kills malignant Kaposi's cells without affecting pregnancy or being toxic, yet also promotes bone-marrow growth. It also has an antiviral effect, killing virus cells, which would make it effective against HIV.

The hormone, human chorionic gonadotropin (HCG), has now been used effectively in trials as a skin treatment against Kaposi's sarcoma. But Dr Gallo told the American Association yesterday that his team is still unsure exactly how the hormone works, though they are closing in on the precise part of the protein that performs the functions.

He was also downbeat about the progress of research into cures and treatments for Aids and HIV, saying that any sort of vaccine could be years away.

And he warned that recent progress with mixtures of drugs, called protease inhibitors, and the discovery of people who appear to be naturally resistant to HIV infection, was not a definite indication that we are at the "beginning of the end" of Aids.