Doctors have succeeded in ridding a man of the HIV virus by giving him a bone marrow transplant in what they claim is the closest treatment yet to a cure for the disease.

The remarkable case gives new impetus to the development of gene therapy for HIV which could ultimately replace the need for expensive and toxic antiretroviral drugs. Instead of taking drugs for life, HIV sufferers might instead have a one-off treatment that would leave them virus-free.

The 42-year-old American had been infected with HIV for a decade. He was treated with antiretroviral drugs in Berlin, where he lives, for four years to hold the disease in check, but then developed leukaemia. Since being given a bone marrow transplant two years ago, he has not taken antiretroviral drugs to control HIV and has had no resurgence of either disease. He is believed to be the longest HIV-free survivor who was previously treated with antiretroviral drugs. Full details of the case are published for the first time today in The New England Journal of Medicine. An editorial in the journal says it "places further emphasis on gene therapies" for HIV, adding: "The case paves the way for innovative approaches that provide long-lasting viral control with limited toxicities for persons with HIV infection."

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The man's treatment began with a search by doctors at Berlin's Charité Hospital for a bone marrow donor with a genetic resistance to HIV. One of the strangest features of the disease is the way some people who have been exposed to the virus on many occasions remain uninfected. Twenty years ago, it was noticed that certain prostitutes in Nairobi remained uninfected despite exposure to the virus through thousands of sexual contacts.

It has since emerged that some people carry a mutation of a gene (CCR5) that confers protection against HIV. In Western populations an estimated one to three per cent have the mutation.

Dr Gero Hutter, a haematologist at the Berlin Charité Hospital, and colleagues tested 61 potential donors before they found one with the CCR5 genetic mutation, who agreed to the operation.

The American recipient of the transplant, who runs a holiday rentals business in the German capital, has undergone regular checks in the two years since the treatment. The doctors have tested his bone marrow, blood and tissues and found no sign of HIV. "For as long as the viral load remains undetectable, this patient will not require antiretroviral therapy," they say in the journal.

Speaking to The Independent yesterday, Dr Hutter said there had been several previous reports of patients being virus-free following treatment but none to compare with the latest case. "The difference is that in our patient we had a plan. It was not an accident," he added. "It is the longest time someone who has had antiretroviral therapy and stopped has lasted without the virus rebounding. Normally it rebounds within weeks. It is the closest we have come to a cure."

Dr Hutter said a bone marrow transplant would be too risky as a routine treatment for HIV and too difficult to find donors with the right genetic make-up. But a modification of the approach using gene therapy to render a patient HIV-resistant could work, he said.

Even a costly treatment could be worthwhile. The price of treatment with antiretrovirals in Europe is €70,000 to €80,000 (£63,000 to £72,000) a year compared with a one-off cost of €20,000 to €30,000 for a bone marrow transplant.

Dr Hutter said: "When I started in medicine, HIV was completely untreatable. Now the situation has changed completely. Perhaps our case is a glimpse of hope for the future."

Professor Jay Levy, an Aids specialist at the University of California, and author of the US journal's editorial, said claims that the patient had been cured of HIV would be premature because of the virus's capacity to hide in other parts of the body including the brain, gut, liver and lymphatic system, from which it could always re-emerge.

"Nevertheless, the results... provide further encouragement for those examining approaches to treatment that reduce CCR5 expression in persons with HIV infection," he writes.In 2007, an estimated two million people died from Aids and 2.7 million were newly infected with HIV.

25 years of research: The HIV virus

When the discovery of HIV was announced in 1984, US politicians predicted that a cure for Aids would be found within five years, but it is still a distant prospect.

Over the past 10 years, a cocktail of aggressive antiretroviral drugs has been developed to help keep the effects of the disease at bay. Eliminating it has proved far more difficult because of the virus's unique nature.

HIV integrates itself into an infected person's DNA and attacks the cells the immune system sends to attack it. Once infected, these T-cells take the virus deeper into the body. Gene therapy is a new approach that harnesses the natural resistance to HIV shared by 3 per cent of people.

Experts hope that by tweaking a sufferer's DNA, they can achieve "long-lasting viral control".