Breakthrough in AIDS cure

Gene therapy is in the frontline of the cure for AIDS. Will it lead to further interesting cases like the german patient who after a bone marrow transplant was cured from AIDS?

The 42-year-old American living in Berlin is currently recovering from the leukaemia treatment, but he seems to have defeated AIDS. Normally, if the AIDS treatment stops, the viral levels increase abruptely. But, despite having interrupted the patient's AIDS treatment, because of the bone marrow transplant, they haven't detected the virus in his blood for more than 600 days.

The breakthrough appears to be that Dr. Hütter, a 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 AIDS virus. 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.

Most researchers believed some HIV still lurks in the patient but that it can't ignite a raging infection, most likely because its target cells are invulnerable mutants. The scientists agreed that the patient is "functionally cured."

The current treatment methods are merely paliative, and very expensive, mainly because they must be taken every day until the end of one's life.

In 1996, when antiretroviral drugs were proved effective, some researchers proposed that all cells harboring HIV might eventually die, leading to eradication of HIV from the body. 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.

That very year scientists found people who had inherited a mutation from their parent that made them immune to HIV. The mutation prevents the coreceptor CCR5 from appearing on the surface of cells. Since most HIV strains must bind to CCR5 to enter cells, the mutation bars the virus from entering. New AIDS drugs, don't attack HIV itself but blockCCR5.

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.

The transplant treatment itself, given only to late-stage cancer patients, kills up to 30% of patients. While scientists are drawing up research protocols to try this approach on other leukemia and lymphoma patients, they know it will never be widely used to treat AIDS because of the mortality risk.

Gene therapy faces daunting technical challenges currently. 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.

At City of Hope cancer center in Duarte, Calif., John Rossi and colleagues actually use HIV itself, genetically engineered to be harmless, to deliver to patients' white blood cells three genes: one that inactivates CCR5 and two others that disable HIV.

Are we starting a new chapter in the AIDS history? Only time will tell...

Watch the video: http://www.youtube.com/watch?v=2TIXQfo7WHY

Adapted from The Wall Street Journal

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