Doctors in Berlin said a man was cured of AIDS after he received bone marrow transplant from a donor naturally resistant to HIV virus.   The man had been negative for HIV for nearly two years ever since the treatment.

But the experts quickly warned that the treatment is not feasible for most AIDS patients or HIV carriers because for one thing donors with the genetic mutation that may be responsible for the miraculous cure are rare.    Only one in every 1,000 Europeans and Americans may carry the desirable mutation.

Other obstacles to successfully receiving the procedure are high risk of dying from the procedures itself.   Studies showed 20 to 30 percent of patients die from bone marrow transplant because the sick bone marrow needs to be killed by high doses of radiation and or medications.

Even if some people can find a HIV-resistant donor and be able to survive the procedure, bone marrow transplant is too costly for millions of HIV carriers and AIDS patients who live in Africa where the disease is most commonly seen.

The 42-year-old man suffered both leukemia and HIV.   Ever since he received the transplant at Berlin's Charite clinic two years ago, he had been free of HIV virus as tests on the man's bone marrow, blood and other organ tissues had been all clear.

Scientists believe the mutated gene of concern, called Delta 32, prevents HIV from attaching itself to cells by blocking a receptor called CCR5.  

But doctors are not so sure if the man was cured because of the genetic mutation in the donated bone marrow.   But theoretically, knocking out the receptor by a gene therapy may be a future treatment for AIDS, Professor Andrew Sewell, University of Cardiff, was cited by BBC as saying.

This German case is an exceptional, said a health observer. Previous reports showed that bone marrow transplantation could be more likely to spread HIV than cure AIDS.

One report published in the Aug 1993 issue of Bone Marrow Transplantation says a 41-year-old woman who underwent autologous bone marrow transplantation for non-Hod.gkin's lym.phoma ended up found HIV positive. After treatment, she was complicated by a series of infections and required to receive prolonged blood product support.

Unfortunately she was found seropositive for anti-HIV about 6 months later after transplantation. The blood donors were screened for HIV antibody and HIV antigen. Jootar S and colleagues , authors of the report, from Ramathibodi Hospital of Mahidol University in Thailand suspected that HIV spread through the donated bone marrow.