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06 Jan 2015

Stem Cells to Resist HIV in Mice: Opens Possibility for Human Trials

The contribution of stem cells in search of HIV cure shows some positive results in mice and opens up new avenues for human clinical trials. The researchers from University of California conducted a study using genetically modified human stem cells to fight off HIV infections in mice. This improved gene therapy strategy showed promising results in animal model and secured approval from the US Food and Drug Administration to begin human clinical trials.

Creating HIV-resistant Immune System

Joseph Anderson and his colleagues modified the human hematopoietic stem cells by inserting three HIV resistant genes in their genome through genetic engineering technique and transplanted these cells into immune deficient mice. Later, the mice showed resistance to HIV infection and maintained a healthy immune system. This modified immune response has created a possibility for applying the same strategy in humans.

How does the therapy works?

The hematopoietic stem cells are responsible for producing various blood cells including the immune cells in humans. To achieve a HIV resistant immune system, the mutant genes (responsible for HIV resistance) should be included with the genome of these stem cells.

The genes that are involved in modifying the genome of the hematopoietic stem cells include: one gene that prevents the HIV genetic material from exposing, another prevents the function of the viral protein which helps in HIV gene expression and third stops the HIV from attaching to the normal cells. These 3 genes, if present in the blood cells can prevent the HIV infection from affecting the body. By using viral vectors, these genes were successfully inserted in to the genome of the stem cells. The vectors also had a gene to tag the HIV resistant stem cells which will identify a pure population of modified stem cells for transplantation. These stem cells were then introduced into the mice model and left to develop. Following this, they were exposed to HIV infection and observed for change in the CD4+ cell levels.

CD4+ is a glycoprotein found on the surface of WBCs which sends signal to immune cells to attack infectious antigens. If the CD4+ level falls low in the blood, individual becomes susceptible to infections that are characteristic of AIDS. After the stem cell transplantation, the CD4+ levels did not drop and there was no evidence of HIV virus in the animal model which proves a healthy immune response.

How is it different from previous researches?

There were previous attempts to bioengineer the stem cells with HIV resistant genes but the results were not satisfactory. This is due to the unavailability of a pure population of modified stem cells, leading to poor resistance in human trials and thus considered unsuccessful.

In this study, the researchers used a tagging gene to identify the pure HIV resistant stem cells. Thus, a nearly pure population of genetically engineered stem cells (94% pure) was used in the transplantation to achieve maximum outcome. The principal investigator of the research, Anderson said, “Developing a technique to purify the population of HIV-resistant stem cells is the most important breakthrough of this research… We now have a strategy that shows great promise for offering a functional cure for the disease”.

As the virus is not detectable and doesn’t cause any infection, this strategy can be considered as a viable therapy for AIDS. In the human trials, autologous (self) stem cells from the bone marrow of the patients will be used to avoid the risk of graft vs. host rejection. This brings us a step closer in finding a viable treatment option for HIV affected patients.



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