In this article we will discuss about Gene Therapy:- 1. Types of Gene Therapy 2. Demonstration of Gene Therapy 3. Drawbacks.
Types of Gene Therapy:
1. In Vivo Therapy:
The gene is inserted into an individual with the desire that it may find the appropriate target cell (thereby making it inefficient).
2. Ex Vivo Therapy:
The cell from patient is manipulated externally in cell culture and reintroduced into patient.
3. Somatic Cell Therapy:
Fixing of genetic malfunctions in somatic cells is restricted to patient only.
4. Germ Line Therapy:
Germ cells (sex cells) are modified by introduction of functional genes and passed on to future progeny. Genes directly introduced into a cell become non-functional; therefore, carriers known as vectors are genetically engineered to deliver the gene.
Genes are inserted via retroviruses, adenoviruses, adenoassociated viruses and herpes simplex viruses by removal of virulent gene or inserted via non-viral methods by naked DNA, oligonucleotides, lipoplexes and polyp lexes.
Use of genetic therapy is mainly directed towards oncology for eradication of tumour cells. In spite of its low success rate, it is hopeful that gene therapy may be used as an adjuvant therapy to cure diseases like cystic fibrosis, ADD, phenylketonuria and immunodeficiency syndromes.
Demonstration of Gene Therapy:
1. Adenosine deaminase is needed for maturation of white blood cells, and people without this enzyme have severe immune system deficiencies. A functional gene for adenosine deaminase was introduced via a viral vector into the white blood cells of a girl with a genetic deficiency of this enzyme.
Unfortunately, mature white blood- cells were used, and although they survived for a time in the girl and provided some therapeutic benefit, they eventually died, as is the normal fate of such cells. Further clinical trials have used stem cells, the bone marrow cells that constantly divide to produce white blood cells.
2. Hemophilia is a disease in which patients do not make enough of a blood clotting protein. Some cells from the skin of patients’ arms were removed and transfected with a plasmid containing a normal allele of the clotting protein gene. The cells were then reintroduced into the patients’ body fat, where they produced adequate protein for normal clotting.
Drawbacks of Gene Therapy:
Followings are the factors posing as obstacles for effective gene therapy treatment:
a. Short-lived nature of gene therapy.
b. Occurrence of severe immune responses.
c. Problems associated with viral vectors.
d. Ineffective treatment of multi-gene disorders.