Gene Therapy

A brief history of gene therapy

Gene therapy is one of the greatest wonders of genetics science.  Despite the fact that most of the genetic disorders cannot be completely cured , gene therapy can modify the seriousness and the consequences of mutant genes. By using gene therapies , one can treat or manage some of the associated signs and symptoms of a genetic ailment. The first attempt on the genetic therapy was made by Martin Cline but his efforts went unsuccessful. He was conducting a series of experiments on one of his patients to treat thalassaemia (a blood disorder). Later on, ( 14th of September 1990), Ashi De-Silva has successfully treated the disease ADA dependent SCID (Adenosine deaminase deficiency ). But the first somatic treatment that led to a permanent genetic change was noticed in the year 1993, the therapy was aimed at curing malignant brain tumours by using recombinant DNA.

 

What is gene therapy?

Traditionally, gene therapy was all about fixing the genetic problem at its source of the defect but in reality, it is one step ahead. In gene therapy, polymers are translated into proteins that interfere with target gene expression. Such interference can make genetic expressions of genes normal. Artificial genes are cultured outside the human body by using recombinant technology. The cultured gene is a polymer molecule packed safely within a "vector".  Vectors aid in transferring the recombinant molecule inside the target cells without harming themselves. Since 2006, there has been an array of successful therapies gained popularity in India. Some of the examples of genetic therapies in the past are the treatments against chronic lymphocytic leukaemia (CLL), acute lymphocytic leukaemia (ALL), multiple myeloma, haemophilia, Parkinson’s disease, retinal diseases, X-linked SCID, ADA-SCID, and adrenoleukodystrophy. Two major approaches of gene therapy are meant to either replace the defective gene completely or correct the defect. Depending upon which types of cells are to be treated, there are 2 types of gene therapies, namely, Somatic gene therapy and germ-line gene therapy. Somatic therapy is the transfer of a section of recombinant DNA to any cell of the somatic part (body part other than sexual part). Germ-line gene therapy is the transfer of a section of recombinant DNA to cells that produce eggs or sperm.

 

Gene therapy by using vectors

A gene cannot be inserted directly into the defective cell. A vector or mediator such as viruses are often used to transfer the recombinant DNA complex into the host. The viral vectors can be Retrovirus, Lentivirus, Herpes virus, Adenovirus plasmid, etc.  Apart from the viruses, stem cells and liposomes also found to be useful. During the process of transfer, vectors are modified in such a way that, they do not affect the host`s body, instead, they can just deliver the genome to the target cells. DNA of the vector cell is being used as a medium for integration of the artificially made genome outside the human body.  As a general rule, the whole DNA is not going to be inserted into the target cell, but only the specific piece of genome is injected  in order to prevent the contamination.

 

Method of gene injection

A sample of the patient's cells can be collected and exposed to the vector in a laboratory setting to identify any unavoidable reactions and the compatibility of the injectable gene. The vector is injected by the intravenous route through a probe directly into the target cell. Below is the image showing the example of Gene therapy using adenovirus.

Gene therapyGene therapy-Image-US National Library Of Medicine

 

Risks of gene therapy

A sample of the patient's cells can be collected and exposed to the vector in a laboratory setting to identify any unavoidable reactions and compatibility. The vector is injected by intravenous route by means of a  probe directly into a specific tissue -the target cell as shown in the image above. The virus is packed in a vesicle. As the viral unit enters the blood vessels, the acidic environment releases the Penton.m Gradually, the material come sin contact with the nuclear pore of the vector cell resulting in viral disassembly into the host`s DNA.

 

 

Read more

1      

Introduction to genetics and heredity

2

Gene mutation

3

Human genome project

4

Mendelian inheritance

 

 

Questions

  1. What is gene therapy?

  2. Briefly explain the history of gene therapy.

  3. What are the vectors used for gene therapy?

  4. Explain the method of gene injecction.

 

 



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