Stem Cell Gene Therapy To Treat Chronic Granulomatous Disease!
A collaborative study by the researchers from the National Institutes of Health (NIH), National Institute of Allergy and Infectious Disease (NIAID) and The Johns Hopkins University School of Medicine has revealed a technique that involves the usage of gene therapy on stem cells in the laboratory to correct the gene defects in chronic Granulomatous Disease (CGD), an inherited, rare immune disorder.
CGD is a condition where the neutrophils, a type of white blood cells of the immune system are prevented from making hydrogen peroxide, the chemical that acts as a defense agent against fungal and bacterial infections. A mutation on X chromosome results in a type of CGD known as ‘X-linked CGD (X-CGD).’
Gene therapy is a technique that involves the manipulation of defective genes responsible for the development of disease using stem cells and genetically engineered viruses.
In the current study, gene therapy without viruses was used. Adult stem cells were extracted from X-CGD patients’ bone marrows and were reprogrammed to become induced pluripotent stem cells (iPSCs). iPSCs have the capacity to grow indefinitely and regenerate into any cell type including Hematopoietic Stem Cell (HSC) just like embryonic stem cells.
iPSCs do not express the disease traits, even though they have the mutated gene. The researchers succeeded in differentiating the iPSCs into neutrophils that have lost the capability to make hydrogen peroxide in the laboratory for the first time.
After recreating the disease in the laboratory, the team went on to correct the genetic defects. To do this, synthetic proteins known as zinc finger nucleases (ZFNs) were used to target a corrective gene specific to X-CGD iPSCs.
Following this, the iPSCs were screened to identify the cells containing a single copy of the corrective gene. It was also observed that the iPSCs that were gene corrected could differentiate into hydrogen peroxide producing neutrophils.