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The key points covered in this video include:
1. Introduction to Gene Therapy
2. Using Gene Therapy to Treat SCID
3. Method of Gene Therapy
4. Ethics of Gene Therapy
Introduction to Gene Therapy
Some genetic diseases in humans occur due to the presence of a faulty (mutated) version of a gene (allele). Scientists are looking at ways to replace the faulty allele with a healthy allele in a process known as gene therapy. Gene therapy is a mechanism by which genetic diseases are treated or cured by masking the effect of a faulty allele by the insertion of a functional allele.
Using Gene Therapy to Treat SCID
Viruses have been used for gene therapy to treat the genetic disorder known as severe combined immunodeficiency (SCID). One form of SCID can arise due to a defect in a gene that codes for the enzyme adenosine deaminase (ADA). This results in T cells being unable to proliferate which greatly weakens the immune system. Patients are currently treated with bone marrow transplants or injections of ADA. Scientists are starting to use gene therapy to treat SCID by inserting a healthy version of the allele that codes for ADA into T cells.
Method of Gene Therapy
The first step in using gene therapy to treat SCID is the isolation of the healthy ADA allele from healthy cell tissue. The ADA allele is then inserted into retroviruses which replicate by copying their DNA into host cells. The patient’s T cells are extracted from their blood and mixed with the retroviruses. The retroviruses inject a copy of the healthy ADA allele into the T cells. A small proportion of T cells successfully incorporate the ADA allele into their genome. These T cells are therefore able to produce the functional ADA enzyme. The T cells are reintroduced back into the patient’s blood where they are able to proliferate.Since most T cells do not live more than 6-12 months, this procedure must be repeated at regular intervals.
Ethics of Gene Therapy
Gene therapy has many ethical issues that must be considered. There are concerns about the potential impact that inserting the gene might have on the functioning of other genes. There is also a concern that the replacement of non-functional alleles with healthy alleles could be a slippery slope to designer babies. Designer babies could be made by replacing less desirable alleles for more desirable alleles in early stage embryos.
Summary
Gene therapy is a mechanism by which genetic diseases are treated or cured by masking the effect of a faulty allele by insertion of a functional allele
This is a form of genetic modification and can be achieved using viruses as vectors
Gene therapy has been used to treat SCID which is a genetic disease caused by the lack of the ADA enzyme in T cells
Retroviruses can be used to insert a functional allele of the ADA gene into T cells which provides a temporary treatment
Gene therapy raises some ethical concerns as the insertion of genes can affect the functional of other genes in ways that cannot be known
Using gene therapy to treat disease could also be a slippery slope towards genetically modifying early embryos to make designer babies