16 December 2010

"Lucky Tim": AIDS can be cured by stem cell transplantation

Stem cells cured HIV infection
Andrey Velichko, Computer

Timothy Brown, a US citizen living in Berlin (Germany), was helped by the transplantation of stem cells from the bone marrow of a donor who had a natural resistance to the immunodeficiency virus.

The operation was carried out in 2007; with its help, doctors hoped to cure acute myeloid leukemia (a type of blood cancer), with which Timothy Brown was infected. The previous course of chemotherapy caused significant damage to his immune system. The harm was compounded by immunosuppressive drugs necessary to avoid rejection of donor stem cells.

In such conditions, the immunodeficiency virus, also present in the patient's blood, could lead to his death. However, this did not happen.

Doctors explain this as follows: the stem cell donor inherited from both parents a rare genetic mutation that occurs in about 1% of Caucasians living in the northern and western parts of Europe. When HIV attacks CD4 cells (T helper cells), which are a type of lymphocytes and are responsible for strengthening the body's immune defense, it uses the receptors of these CCR5 cells to "latch on" to them. Fortunately, a receptor mutation known as CCR5-delta32 prevents the immunodeficiency virus from doing this.

For 38 months now, after stem cell transplantation and antiretroviral therapy, which stopped the reproduction of HIV, doctors have not found any traces of infection in the patient's body. Donor CD4 cells with this mutation completely replaced the "native" lymphocytes in Brown's body and, thereby, contributed to the destruction of the virus.

An additional evidence of recovery, the researchers call the fact that CD4 cells remained vulnerable to the mutant form of HIV, using a different type of receptors for "attack". If the infection had remained in the body, the cells would have been re-infected, but this did not happen.

Now Timothy Brown is recognized as healthy, although the severe course of the disease has led to disorders of the nervous system, temporary blindness and memory problems. The main thing for doctors was the proof of the ability of stem cells with the CCR5-delta32 mutation to eliminate HIV. A paper on this topic (Kristina Allers et al., Evidence for the cure of HIV infection by CCR5delta32/delta32 stem cell transplantation) was published in the journal Blood.

The further task of the researchers will be to detect potential donors with the mentioned mutation. It is not necessary to use bone marrow for this — for example, cells from the umbilical cord of newborns would be suitable.

In addition, with the help of genetic engineering, it is possible to artificially obtain stem cells with HIV resistance. This method is very expensive and, obviously, will be used in cases where other methods of treatment are ineffective.

Prepared based on Aidsmap materials: Stem cell transplant has cured HIV infection in 'Berlin patient', say doctors

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