Gene therapy using an Adenovirus vector. A new gene is inserted into a cell using an adenovirus. If the treatment is successful, the new gene will make functional protein to treat a disease. Uploaded from English Wikipedia: original source was National Library of Medicine
Gene Therapy is one
of the most promising techniques in the fight against diseases where causes are
genetic or genetically determined. Interest in this therapeutic modality is
based upon its’ potential for treating and curing some of the most malignant
and devastating diseases affecting humans. The following information wass based
on many sources; I had them listed in the reference section.
Definitions:
Gene therapy
as defined by the Human Genome Project is a technique for correcting defective
genes responsible for disease development. Researchers may use one of several
approaches for correcting faulty genes. The American cancer society defines it
as a new type of treatment in which defective genes are
replaced with normal ones; the new genes are delivered into the cells by
viruses or proteins.Techniques:
In most gene therapy studies, a normal gene is inserted into the genome to replace a disease-causing gene. In order to deliver the gene to the target cell we need a vehicle, a vector, which is most commonly a genetically altered virus with an evolved way of encapsulating and delivering their genes to human cells in a pathogenic manner. In order to be used, the viruses should be genetically modified through the removal of their pathogenic genes, and the insertion of the desired human genes “therapeutic genes”.
Hypothetically, the target cells like patients’ liver or lung cells would be infected with a viral vector, the viral vector then unloads its’ genetic material containing the therapeutic human gene into the target cell. The generation of a functional protein product from the therapeutic gene restores the target cell functionality to a normal state.
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A normal gene may be
inserted into a non-specific location within the genome to replace a
non-functional gene. This approach is most common.
An abnormal gene could be
swapped for a normal gene through homologous recombination.The abnormal gene could be
repaired through selective reverse mutations, which return the gene to its
normal function.The regulation (the degree
to which a gene is turned on or off) of a particular gene could be altered. Some of the
different types of viruses used as gene therapy vectors include Retroviruses, Adenoviruses, Adeno-associated viruses,
and Herpes simplex viruses. Besides virus-mediated gene-delivery systems, there are several non-viral
options for gene delivery, e.g.: direct introduction of therapeutic DNA into
the target cell and the creation of an artificial lipid sphere with an aqueous
core. Therapeutic DNA also can be put inside target cells by chemically linking
the DNA to any molecule that binds to specific cell receptors. Researchers are
also experimenting with introducing a 47th (artificial human) chromosome into
target cells. That chromosome would exist autonomously alongside the standard
46; not affecting their workings or causing any mutations.
Possible Areas:Include cancer gene therapy, haematological disease gene therapy, immunological disease gene therapy, degenerative disorders gene therapy and heart disease gene therapy: An example would be the treatment of heart failure and coronary heart diseases.
Possible limitations:
Seeing all the possible benefits from the gene therapy, it appears to be the magical treatment of the future for most of the fatal and disturbing diseases for humans. There are currently many limitations, which lead us to think more and more about it, those limitations include: Short-lived nature of gene, body immune response, problems with viral vectors and multi gene disorders - Conditions or disorders that arise from mutations in a single gene are the best candidates for gene therapy. Unfortunately, some the most commonly occurring disorders, like heart disease, high blood pressure, Alzheimer's disease, arthritis, and diabetes are caused by the combined effects of variations in many genes. Multigene or multifactorial disorders such as these mentioned would be especially difficult to treat effectively using gene therapy.
References:
Reindal SM., Disability, gene therapy and eugenics- A challenge to John Harris, 2006, J Med Ethics, 26: 89-94 Selkirk SM., Gene therapy in clinical medicine, 2004, Postgrad. Med J, 80: 560-70
