People with the delta 32 version of the CCR5 gene are more
resistant to HIV infection.
Doctors announced in Berlin that a man who received a bone marrow transplant for leukemia was now also free of his HIV infection. Looks like this patient’s luck is finally turning around!
Both leukemia and AIDS are diseases of the blood. Bone marrow transplants cure leukemia by permanently replacing the patient’s blood with the donor’s. This eliminates the cancerous blood cells and so cures the cancer.
One “side effect” of a bone marrow transplant is that the patient’s blood cells now have donor’s DNA. This sometimes makes for problems at crime scenes (and interesting CSI episodes). But here the doctor used it to the patient’s advantage.
Scientists have known for a long time that people with two copies of a certain version of the CCR5 gene, the delta 32 version, are much more resistant to HIV. Their AIDS symptoms also tend to progress much more slowly.
So the doctors reasoned that if the patient were going to receive a bone marrow transplant anyway, why not give him one from a donor with two copies of delta 32? And that’s just what the doctors did.
Over 20 months later, there is no sign of the patient’s leukemia. And no sign of HIV either.
We’ll still need to wait and see if this result holds up. But even if it does, this cure isn’t for everyone. It is expensive and very risky.
Around 1 in 4 patients dies from bone marrow transplants. I’m no M.D., but I would guess that patients at the later stages of AIDS would do even more poorly.
But if the result does hold up, then maybe scientists can figure out how to do something similar without the bone marrow transplant. Maybe they can find a medicine that can shut down the CCR5 gene and so get the same effects as the delta 32 version. Another possibility is gene therapy.
The idea would be to change the patient’s CCR5 gene into the delta 32 version. This would be really hard.
Gene therapy is pretty good at adding a working gene to a cell. It is not very good at changing a patient’s gene. This means it would not be easy to turn a CCR5 gene into the delta 32 version in a patient’s bone marrow cells.
But maybe there is another way. The CCR5 gene is not the only way to be resistant to HIV. Another way is by having extra copies of the CCL3L1 gene. Perhaps scientists could add extra copies of this gene to a patient’s bone marrow cells and help at least slow down HIV. This seems doable with gene therapy.