Cure for HIV: hopes raised by and limitations of stem cell transplant

Subject : Science and technology

Section: Biotechnology

Concept:

One more person infected with HIV (human immunodeficiency virus) has likely been cured after receiving a stem cell transplant for cancer, the sixth such known
The level of virus in his blood remained undetectable 20 months after his anti retroviral therapy was
However, one factor differentiates the Geneva patient, as he is being referred to, from the other five cured after stem cell transplant — his donor did not have the gene mutation that researchers had specifically selected in all the previous
The mutation is associated with lower risk of contracting the infection.

Stem Cell Transplantation

The treatment teams looked for donors with CCR5 delta 32 mutation.
HIV lowers immunity in infected individuals by attacking the CD4 immune cells.
However, to gain entry into these cells, it needs receptors on the surface. People who inherit the CCR5 delta 32 mutation from both parents do not form these receptors, essentially locking the virus out of the cells.
Those who inherit the mutation from one of the parents have fewer receptors and are less likely to get the infection.
Only 1% of the people in the world carry two copies of the CCR5-delta 32 mutation—meaning they got it from both parents — and another 20% carry one copy of the mutation, mainly those of European descent.

CCR5-delta 32 Mutation

Cysteine-cysteine chemokine receptor 5 (CCR5) is the main HIV co-receptor involved in the virus and cell-to-cell spread.
The CCR5 receptors on CD4 cells are used as a doorway by HIV. The CCR5-delta 32 mutation prevents these receptors from forming on CD4 cells, which effectively removes the doorway.
Only 1% of people worldwide have two copies of the mutation, and 20% carry one copy, mostly those of European descent. Those with the mutation are almost immune to HIV, although some cases have been reported.

Stem Cells

Stem cells are undifferentiated, or “blank,” cells. This means they’re capable of developing into cells that serve numerous functions in different parts of the body.
They can divide over and over again to produce new cells.
As they divide, they can change into the other types of cell that make up the body.
Cancer and cancer treatment can damage the hematopoietic stem cells. Hematopoietic stem cells are stem cells that turn into blood cells.

Types of Stem Cells

Stem cells are divided into 2 main forms. They are embryonic stem cells and adult stem cells.
Embryonic stem cells: The embryonic stem cells used in research today come from unused embryos. These result from an in vitro fertilization procedure. They are donated to science. These embryonic stem cells are pluripotent. This means that they can turn into more than one type of cell.
Adult stem cells: There are 2 types of adult stem cells.
One type comes from fully developed tissues such as the brain, skin, and bone marrow. There are only small numbers of stem cells in these tissues. They are more likely to generate only certain types of cells. For example, a stem cell that comes from the liver will only make more liver cells.
The second type is induced pluripotent stem cells. These are adult stem cells that have been changed in a lab to be more like embryonic stem cells. Induced pluripotent stem cells don’t seem to be different from embryonic stem cells, but scientists have not yet found one that can develop every kind of cell and tissue.

Bone Marrow Transplant

A bone marrow transplant is a medical treatment that replaces one’s bone marrow with healthy cells.
The replacement cells can either come from the person’s own body or from a donor.
A bone marrow transplant is also called a stem cell transplant or, more specifically, a hematopoietic stem cell transplant.
Transplantation can be used to treat certain types of cancer, such as leukemia, myeloma and lymphoma, and other blood and immune system diseases that affect the bone marrow.
Bone marrow transplants may use cells from the same person (autologous transplant) or from a donor (allogeneic transplant).