CCR5-delta32
Also called: CCR5-Δ32 · CCR5 delta 32 deletion
About 1% of people of Northern European descent carry two copies of a broken gene that makes them almost immune to the most common form of HIV. A bone marrow transplant from one such donor produced the first cure of HIV.
How common
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How it works
CCR5 is a protein on the surface of some immune cells. Most strains of HIV use it as a door. The virus attaches to CCR5 and pulls itself inside13. The delta32 variant is a deletion of 32 letters of DNA from the CCR5 gene. The shortened protein never reaches the cell surface1. With no door, the virus cannot get in.
A person with two copies of delta32 has no working CCR5 and is resistant to nearly all common HIV strains. A person with one copy has fewer doors, and infection progresses more slowly1. The protection is not total. Some rare HIV strains use a different protein, CXCR4, and can still infect13. Beyond HIV, the variant seems mostly harmless, though carriers may be more vulnerable to West Nile virus1.
How common it is
About 1% of people of Northern European descent have two copies, and 10% to 15% have one1. The rate falls towards southern Europe and is close to zero in Africa, East Asia, and the Americas before European contact1. HIV is too new to explain such a common variant. One hypothesis is that plague or smallpox in medieval Europe favoured carriers. Neither has been proven15.
Is it a problem?
No. Carrying one or two copies of CCR5-delta32 causes no disease and needs no treatment. It is a natural variant, not a disorder, and it happens to block a door that HIV uses to enter cells1. Carriers are not immune to every HIV strain, since some rare strains use a different receptor, CXCR413. The deletion has been linked to a slightly higher risk from West Nile virus, but that is a minor trade-off, not something to raise with a doctor1.
History and culture
In 2007, Timothy Ray Brown, an American living in Berlin, had both HIV and leukaemia. His doctor, Gero Hütter, chose a bone marrow donor with two copies of delta322. The transplant replaced his immune system with resistant cells. The virus never returned. His case was published in 2009 and he became known as the Berlin Patient, the first person cured of HIV2. He died of leukaemia in 20202. A few more people have since been cured the same way, including Adam Castillejo, the London Patient4. The procedure is too dangerous to use for HIV alone.
Sources and further material
- Wikipedia CCR5
- Wikipedia HIV
- Wikipedia Adam Castillejo
- doi.org Evaluating plague and smallpox as historical selective pressures for the CCR5-Δ32 HIV-resistance allele PNAS. Tests plague and smallpox as the force that made the variant common.
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