Gene Therapy: Meaning, Types, Advantages and Disadvantages

In this article we will discuss about Gene Therapy:- 1. Meaning of Gene Therapy 2. Types of Gene Therapy 3. Vectors 4. Advantages 5. Disadvantages.

Meaning of Gene Therapy:

Gene therapy is the use of DNA as a pharma­ceutical agent to treat diseases. It was first conceptualized in 1972, with the authors urg­ing caution before commencing gene therapy studies in humans. The first FDA-approved gene therapy experiment in the United States occurred in 1990, when Ashanti DeSilva was treated for ADA-SCID.

Since then, over 1,700 clinical trials have been conducted using a number of techniques for gene therapy. In gene therapy, DNA that encodes a therapeutic pro­tein is packaged within a “vector”, which is used to get the DNA inside cells within the body. Once inside, the DNA becomes expressed by the cell machinery, resulting in the produc­tion of therapeutic protein, which in turn treats the patient’s disease.

Although early clinical failures led many to dismiss gene therapy as over-hyped concept, yet the clinical successes in the recent years have induced new optimism in the promise to make gene therapy a successful approach to treat diseases.

These include successful treat­ment of patients with the retinal disease, X- linked SCID, ADA-SCID, adrenoleukodystrophy, and Parkinson’s disease. Recent break­through using gene therapy is a mouthwash that promises good results for those with oral cancer. This mouthwash wards off oral cancer by destroying suspicious growths in the mouth before they become malignant.

Types of Gene Therapy:

Somatic Gene Therapy:

In somatic gene therapy, the therapeutic genes are transferred into the somatic cells, or body, of a patient

Germ Line Gene Therapy:

In germ line gene therapy, Germ cells, i.e., sperm or ovum, are modified by the introduction of functional genes, which are integrated into their ge­nomes. This would allow the therapy to be heritable and passed on to later generations.

Preventive Gene Therapy:

Preventive gene therapy is the repair of a gene with a mu­tation associated with a progressive disease, prior to the expression of a medical condition, in order to prevent that expression.

Vectors of Gene Therapy:

Gene therapy uses the concept of delivering of the DNA into cells, which can be accomplished by a number of methods. The two major meth­ods are those that utilize recombinant viruses also called biological nanoparticles or viral vectors and those that utilize naked DNA or DNA complexes that are referred to as the non- viral methods.

Viral Vectors:

All viruses bind to their hosts and introduce their genetic material into the host cell as part of their replication cycle. A number of viruses have been used for human gene therapy, in­cluding retrovirus, adenovirus, lent virus, her­pes simplex virus, vaccinia, pox virus, and adenoassociated virus

Non-Viral Vectors:

There are several methods for non-viral gene therapy, including the injection of naked DNA, electroporation, the gene gun, nonoperation, magnetofection, and the use of oligonucleo­tides, lipoplexes, dendrimers, and inorganic nanoparticles.

However, non-viral methods can present certain advantages over viral methods, such as large scale production and low host immunogenicity.

Advantages of Gene Therapy:

1. Gene silencing is a concept that in itself is self-efficient for management of many dis­eases.

2, Gene therapy has the potential to elimi­nate and prevent hereditary diseases, such as cystic fibrosis, and is a possible cure for heart disease, AIDS and cancer.

3. Gives an advantage to a person born with genetic disorder to live life in a normal way by replacing non-functional gene with a functional one.

Disadvantages of Gene Therapy:

1. Irregular immune responses.

2. Viral vectors may introduce toxicity, as well as immune and inflammatory re­sponses.

3. Multi-gene disorders such as heart disease, high blood pressure, Alzheimer’s disease, arthritis, and diabetes cannot be treated through this therapy as conditions or dis­orders that arise only from mutations in a single gene are the best candidates for gene therapy.

4. Religious concerns.

5. Chances of inducing iatrogenic (physician induced) tumours in human beings.

6. Short-lived nature of gene therapy.