Gene Theraphy Introduction, Peripheral, Epigenetic aspects, Anti-tumour function, Cells, Lymphocytes, Cytokine genes

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Gene Theraphy
Gene Theraphy Introduction
Human Diseases Targeted for Gene Therapy
Some Human Diseases Targeted for gene therapy
Vectors and Other Delivery Systems for Gene therapy
Viruses as vectors
Retrovirus (RV) as a vector
Adenovirus (AV) as a vector
Adeno associated virus (AAV) as a vector
Lentiviruses as a vector
Non-viral DNA delivery systems
Synthetic particles as vectors
Transient Expression for gene therapy
Splicesome mediated trans-RNA splicing (SMART)
Ex Vivo vs In Vivo Gene Therapy
Target Tissue of Choice for Gen-Delivery System

	Biotechnology in Medicine Gene Therapy During the last two decades of the 20th century (1980-2000), more than 200 genes responsible for a variety of genetic. .disorders in human beings were identified. The causes of disorders in the form of specific mutations in these genes have also been elucidated. Therefore, if the known defects in genes are rectified, or if the defective gene in each case replaced by a normal healthy gene, then the corresponding genetic disorder may be corrected. Such a treatment of human genetic disorders are described as gene therapy. However, gene therapy need not always be targeted at either the correction of the defective gene or suppression of its expression or even introduction of a normal healthy gene, but may also be targeted to peripheral or even epigenetic aspects of the pathogenesis pathway.
For instance, while applying gene therapy to cancer, one may not like to correct the oncogene or introduce the cancer suppressor gene, but may only introduce either the genes having anti-tumour function in cells (e.g. tumour-infiltrating lymphocytes or TILs) or introduce cytokine genes into the tumour cells, thus indirectly suppressing tumour growth. In other (BC-41 ) words, gene therapy involves treatment of genetic disorders by insertion of a gene into the body of an organism, in order to correct the disorder. This sometimes involves, replacement of the defective gene by the normal gene in a functional sense, but not in a physical sense. The healthy gene is introduced into the appropriate cells of the patient, a process that is technically described as gene delivery. Effective systems of gene delivery have been developed in many cases involving retroviruses and a variety of other viral and non-viral vector systems. More recently, nanotechnology has also been utilized for transfer of genes in particles that measure <500nm in diameter.
More important than the above gene correction method is the gene augmentation method, where normal foreign gene sequences for the defective gene are introduced. A number of efficient methods for this purpose are already available, where a number of copies of the desired gene are introduced in the cell and arc made to express at high level. Expression and transfer vectors, in the form of a number of viruses are now available to achieve this goal. In view of this, maximum progress in the area of gene therapy has been achieved through the above gene augmentation model involving vector mediated DNA delivery system.
Once the gene correction or gene augmentation has been achieved at the cellular level (in the cells obtained from the affected organ depending upon the disease), the modified cells can be implanted into a suitable region either in an organ of the patient or in the embryo. Direct delivery of the DNA (carried by the vector) into the living cells of the body has also been suggested in several cases, so that both in vitro and in vivo introduction of corrected gene has been suggested. Therefore, gene therapy can be used at the following two different levels: (i) embryo therapy, in which the genetic constitution of embryo at the post-zygotic level is altered, so that the inheritance will also be altered, and (ii) patient therapy, in which cells with healthy gene may be introduced in the affected tissue, so that the healthy gene overcomes the defect without affecting the inheritance of the patient. It is believed that in future, gene therapy of both types will be possible.
	Research in gene therapy, as a biomedical discipline, started in mid 1980s and the first gene therapy experiment was conducted in 1990 on a human patient {a four - year old child suffering with adenosine deaminase (ADA) deficiency, which had wiped out her immune system, crippling her ability to fight infectious diseases}. During 1990-2000, hundreds of approved clinical trials, involving more than a thousand patients have been conducted in pilot phase I experiments, so that opportunities in gene therapy are attracting interest not only from research organizations in the public sector, but also from both small and large pharmaceutical companies. Different aspects of gene therapy including its possibilities and limitations