A German doctor says one of his patients, who suffered from leukaemia and was infected with the immunodeficiency virus that causes AIDS, appears to have been cured of AIDS by a bone marrow transplant from a donor who had a genetic mutation known to help the body resist AIDS infection.

Dr. Gero Hutter and Thomas Schneider of the Clinic for Gastroenterology, Infections and Rheumatology of the Berlin Charite hospital said the man, a 42-year-old American living in Berlin, has shown no sign of either disease since the transplant which was performed two years ago.

The German team selected a bone marrow donor who had a genetic resistance to most strains of HIV – the mutations affects a receptor, CCR5, that the AIDS virus uses to get into the cells it infects – in the hope that the procedure would result in more HIV-resistant cells in their patient. He underwent the transplant and since then, he has taken no anti-retroviral drugs.

The German doctor targeted the “Achilles” heel of HIV, which acts like a doorway that the AIDS virus uses to get into the body.

“More than 20 months after the successful transplant, no HIV can be detected in the patient,” Berlin’s Charite hospital said in a statement.

“We performed all tests, not only with blood but also with other reservoirs,” Dr. Thomas Schneider of the Clinic for Gastroenterology, Infections and Rheumatology of the Berlin Charite hospital told a news conference.

Bone marrow is the flexible tissue found in the hollow interior of bones. Bone marrow contains three types of stem cells: hematopoietic stem cells, mesenchymal stem cells, and endothelial stem cells. Bone marrow stem cell transplants are dangerous, as they require the patient to have his own bone barrow completely destroyed using drugs or radiation.

This procedure puts a patient at high risk of infections, sepsis, and septic shock because they may go for several weeks without an important number of white blood cells. Practically, patients risk death because they have no immune system until the stem cells grow and replace the missing ones. Transplantation from one person to another is performed in severe cases of disease of the bone marrow. The first physician to perform a successful human bone marrow transplant was Robert A. Good. Many receipients of stem cell transplantation are leukaemia patients or those who suffer from severe forms of cancers who would not benefit from prolonged treatment with chemotherapy.

Two million people die of AIDS each year. About 33 million people worldwide are infected with the virus and 2.7 million new cases were reported in 2007, according to UNAIDS. Over three quarters of these deaths occurred in sub-Saharan Africa, which remains the epicenter of the global malady. Researchers believe the virus originated in this region during the twentieth century. There is currently no vaccine or cure for HIV, but the search for a more effective antiretroviral therapy that could prolong people’s lives many years continues.

Bone marrow transplant could one day, however, help boost the immune system of those already infected, helping them destroy the virus and extending their lifetime.