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.
The development suggests a potential new therapeutic avenue and comes as the search for a cure has adopted new urgency. Many fear that current AIDS drugs aren't sustainable. Known as antiretrovirals, the medications prevent the virus from replicating but must be taken every day for life and are expensive for poor countries where the disease runs rampant. Last year, AIDS killed two million people; 2.7 million more contracted the virus, so treatment costs will keep ballooning.
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.
Back in 1996, when "cocktails" of antiretroviral drugs were proved effective, some researchers proposed that all cells harboring HIV might eventually die off, leading to eradication of HIV from the body -- in short, a cure. Those hopes foundered on the discovery that HIV, which integrates itself into a patient's own DNA, hides in so-called "sanctuary cells," where it lies dormant yet remains capable of reigniting an infection.
But that same year, researchers discovered that some gay men astonishingly remained uninfected despite engaging in very risky sex with as many as hundreds of partners. These men had inherited a mutation from both their parents that made them virtually immune to HIV.
The mutation prevents a molecule called CCR5 from appearing on the surface of cells. CCR5 acts as a kind of door for the virus. Since most HIV strains must bind to CCR5 to enter cells, the mutation bars the virus from entering. A new AIDS drug, Selzentry, made by Pfizer Inc., doesn't attack HIV itself but works by blocking CCR5.
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.
Dr. Hütter, 39, remembered this research when his American leukemia patient failed first-line chemotherapy in 2006. He was treating the patient at Berlin's Charité Medical University, the same institution where German physician Robert Koch performed some of his groundbreaking research on infectious diseases in the 19th century. Dr. Hütter scoured research on CCR5 and consulted with his superiors.
Finally, he recommended standard second-line treatment: a bone marrow transplant -- but from a donor who had inherited the CCR5 mutation from both parents. Bone marrow is where immune-system cells are generated, so transplanting mutant bone-marrow cells would render the patient immune to HIV into perpetuity, at least in theory.
Wednesday, November 12, 2008
A Cure for AIDS?
A new case report out of Germany seems to have found a potential cure for AIDS. Yes, I said 'cure.' The doctor, a hematologist-oncologist, was treating an HIV positive patient for leukemia. Here's how he came upon the potential cure for AIDS:
Sounds interesting, but given the mortality rate of bone marrow transplants, it probably won't be a widespread treatment for a while.