We're really tinkering with pretty murky processes

Dr James Marion, Mount Sinai School of Medicine, New York

Research suggests that people with defective CCR5 are less likely to become infected with HIV, and take longer to develop Aids if they do.

Doctors already inject patients with manufactured antibodies to treat diseases such as psoriasis, arthritis and Crohn's disease.

But the body clears these antibodies within hours or weeks, so people need repeated injections.

The new technique overcomes this problem by stimulating the body to manufacture antibodies against itself.

The researchers used a virus particle "decorated" with the macaque monkey form of CCR5.

It stimulated the production of fairly high levels of antibodies against the monkeys' own CCR5.

The next step is to try infecting the monkeys with an HIV-like virus to see if the CCR5 antibodies will protect them.

Lead researcher Dr John Schiller said: "If we can do it in macaques, then the chances that it won't work in humans are small."

However, Dr James Marion, a physician at the Mount Sinai School of Medicine, New York who has used antibodies to treat Crohn's disease, is wary about the chances of success.

He said: "My concern would be if you knock [CCR5] out, there might be a price to pay. We're really tinkering with pretty murky processes."