Module 1: Introduction

Lecture 1: Introduction (Part I)

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Gene therapy is a process that involves introduction of genetic material into a person's cell to cure or prevent the disease condition. Researchers around the world are studying gene therapy for a number of diseases, such as cystic fibrosis, hemophilia , cancer , and even influenza, through a number of different approaches.

Some facts:

 

Human genome project has completed in the year 2003. Human genome contains about 3 billion nucleotides. The entire genome contains more than 35,000 genes.

Basic process of gene therapy involves one of the followings

•  Introducing a new specific gene into the body to combat a particular disease.

•  Interchanging a disease causing gene with a healthy copy of same gene.

•  Inactivating, or “knocking out,” of an impaired gene that is not carrying normal function using engineered nucleases such as zinc finger nucleases, engineered I- Crel homing endonucleases or the nucleases obtained from TAL effectors. One of the best examples of gene-knockout mediated gene therapy is the knockout of the human CCR5 gene in T-cells to control HIV infection.

The method of gene transfer and its expression is termed as transduction. A gene can be transferred to an individual using a carrier known as a “ vector ”. Despite the fact that the principle of gene therapy is quite simple but the outcome depends mainly on the vehicles or vectors through which the gene transfer is carried out. Practically gene transfer vectors can be divided either into synthetic or virus based gene transfer systems. With the passage of time many gene transfer vectors have been introduced. Viruses such as adenovirus, adeno-associated virus, and lentiviruses are the most common types of vectors used in gene therapy. The viruses are altered in order to make it safe before using them as a vector for gene therapy. However some risks still exist with gene therapy. The method is still in its inception, but it has been used with varying degree of success.

Facts:

 

The first gene therapy experiment was conducted on a 4-years-old girl at National Institute of Health, USA in 1990. She was suffering from a genetic disease having deficiency of adenosine deaminase enzyme required for the proper metabolism of purine. Any malfunctioning of adenosine deaminase leads to severe combined immunodeficiency in affected patients. The white blood cells of the girl was taken out and corrected with a human gene using retrovirus as a vector.