Daily Telegraph

Berlin, Nov 13: The man, a 42-year-old American living in Berlin, has shown no trace of the virus in the nearly two years since Dr Gero Huetter, a haematologist, gave him the operation - a standard treatment for leukaemia, from which the patient was also suffering.

The breakthrough gives hope for cutting-edge gene therapies to tackle the disease that killed 2 million people worldwide last year and infected another 2.7 million.

Working on a hunch, Dr Huetter selected a bone marrow donor who had a genetic resistance to most strains of HIV in the hope that the transplanted marrow would produce HIV-resistant cells in his patient.

It appears to have worked, and yesterday Dr Huetter declared his patient ''functionally cured''.

The patient has taken no anti-retroviral drugs, the standard treatment for AIDS, since the transplant.

"HIV has an Achilles heel,'' Dr Huetter told a press conference in Berlin.

That "Achilles" heel is a molecule that sits on the outside of a human cell and acts as a doorway to let HIV invade the body.

People with the genetic resistance have a mutation which blocks the production of the molecule, giving carriers a life-long resistance to most strains of HIV.

About 1 per cent of Europeans have the mutation, but people of African, Asian and South American descent almost never carry it.

Though bone marrow transplants are not an effective therapy, since they are expensive and kill up to 30 per cent of recipients, it offers hope that AIDS patients' cells could be re-engineered using gene therapy.

US expert David Baltimore, who won a Nobel prize for his research on cancer viruses, described the breakthrough as "a very good sign'' and virtual "proof of principle'' for gene therapy cures, while cautioning the case could be a fluke.

Though the case has provoked great excitement, most experts are likely to remain wary until it is published in a peer-reviewed journal.

Will Nutland, from the Terrence Higgins Trust, said: "This give researchers a new avenue to explore but it should be remembered that we do not know what will happen to this patient in the long-term and that this has only been tried in one person.

"Also, if it is a breakthrough it will be a breakthrough in decades rather than years."

He added that HIV could remain in the body at undetectable levels for years.

Around 60,000 people in Britain are thought to be infected with HIV, including an estimated 20,000 who have yet to be diagnosed with the virus.