(See Corrections & Amplifications item below.)

The startling case of an AIDS patient who underwent a bone marrow transplant to treat leukemia is stirring new hope that gene-therapy strategies on the far edges of AIDS research might someday cure the disease.

The patient, a 42-year-old American living in Berlin, is still recovering from his leukemia therapy, but he appears to have won his battle with AIDS. Doctors have not been able to detect the virus in his blood for more than 600 days, despite his having ceased all conventional AIDS medication. Normally when a patient stops taking AIDS drugs, the virus stampedes through the body within weeks, or days.

"I was very surprised," said the doctor, Gero Hütter.

The breakthrough appears to be that Dr. Hütter, a soft-spoken hematologist who isn't an AIDS specialist, deliberately replaced the patient's bone marrow cells with those from a donor who has a naturally occurring genetic mutation that renders his cells immune to almost all strains of HIV, the virus that causes AIDS.