A patient with leukemia and aids had his bone marrow cells replaced 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.
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. Last year, AIDS killed two million people; 2.7 million more contracted the virus.
While cautioning that the Berlin case could be a fluke, David Baltimore, who won a Nobel prize for his research on tumor viruses, deemed it "a very good sign" and a virtual "proof of principle" for gene-therapy approaches. Dr. Baltimore and his colleague, University of California at Los Angeles researcher Irvin Chen, have developed a gene therapy strategy against HIV that works in a similar way to the Berlin case. Drs. Baltimore and Chen have formed a private company to develop the therapy.
About 1% of Europeans, and even more in northern Europe, inherit the CCR5 mutation from both parents. People of African, Asian and South American descent almost never carry it.
There is a potentially safer alternative: Re-engineering a patient's own cells through gene therapy. Gene therapy also faces daunting technical challenges. For example, the therapeutic genes are carried to cells by re-engineered viruses, and they must be made perfectly safe. Also, most gene therapy currently works by removing cells, genetically modifying them out of the body, then transfusing them back in -- a complicated procedure that would prove too expensive for the developing world. Dr. Baltimore and others are working on therapeutic viruses they could inject into a patient as easily as a flu vaccine. But, he says, "we're a long way from that."