What is gene therapy?

Replacing harmful genes in an organism with healthy genes is called gene therapy. Gene therapy is used to treat diseases such as cancer, heart disease, diabetes, haemophilia and AIDS.

The discovery of gene therapy

Gene therapy first emerged in the 1970s, when scientists began exploring the possibility of manipulating genes to treat genetic disorders. In 1972, Paul Berg and colleagues demonstrated the ability to insert foreign DNA into the genome of a bacterial virus.

First attempt

The 1980s saw the first attempts at gene therapy in animal models. In 1980, Martin Kline conducted the first human gene therapy trial, aimed at correcting a genetic blood disorder. But the result was not successful. In the late 1980s and early 1990s, the focus shifted to ex vivo gene therapy, where cells are genetically modified outside the body and then reintroduced.

First successful

The first successful clinical trial of gene therapy occurred in 1990, when Ashanti D’Silva, a four-year-old girl with severe combined immunodeficiency, was treated using ex vivo gene therapy.

Types of gene therapy

There are two types of gene therapy

1. Germ-line therapy

     2. Somatic cell therapy

Germ-line therapy

In germline gene therapy, DNA is inserted into reproductive cells in the human body, such as eggs or sperm. Germline gene therapy will modify the genetic makeup of a person’s reproductive cells and pass it on to future generations.

Somatic cell therapy

Somatic gene therapy involves the introduction of novel genetic material into somatic cells to express therapeutic gene products. This emerging technology holds great promise for the treatment of both inherited and acquired diseases.

What diseases is gene therapy used to treat?

Gene therapy is used only when conventional treatments have failed. Gene therapy is used as a last-minute treatment for inherited diseases, AIDS and cancer. Besides, gene therapy is used in cases of heart disease, diabetes, Alzheimer’s, arthritis, infectious diseases etc.

Application techniques

Gene therapy is a method used in the treatment of complex diseases in which the disease is cured by genetic modification of cells instead of drugs. In this procedure, the defective gene responsible for the disease is removed and the healthy gene is replaced. Gene therapy requires safe and effective carriers for gene delivery. Genetically altered viruses are currently a widely used vector that transports pure genes. This carrier virus is placed in infected cells. Carrier viruses deliver disease-causing genes to diseased cells. In this way healthy genes are replaced in diseased cells. As a result, the cells regain their normal state.

Benefits of using gene therapy 

Cystic fibrosis

Gene therapy is a process in which a new, correct version of the CFTR gene would be placed into the cells in a person’s body. Although the mutant copies of the CFTR gene would still be there, the presence of the correct copies would give cells the ability to make normal CFTR.

Alpha1

Gene therapy is a long-term strategy for the treatment of AATD-lung disease, where the approach is to express the WT allele to drive production of the normal human M-AAT gene into cells that will secrete the protein into the blood, ultimately augmenting the lung levels of AAT and preventing alveolar proteolytic.

Haemophilia

Gene therapy for haemophilia A is a one-time infusion that uses a vector to deliver a functional gene to replace the haemophilia patient’s own defective gene or a therapeutic gene to provide a missing protein. The result is better clotting factor activity, which protects against bleeding.

Thalassemia

The only FDA-approved gene therapy for beta thalassemia brings back normal red blood cells. It works by putting functional copies of the abnormal gene into a patient’s own blood stem cells. The red blood cells are then able to make normal or near normal levels of haemoglobin.

Sickle cell

Gene therapy may treat SCD by editing DNA in haemoglobin genes to stop the disease. It can be done by either fixing the faulty haemoglobin gene or turning on a different, healthy haemoglobin gene. Although gene therapy for SCD isn’t currently available for most people, this may change soon.

Cancer

Gene transfer is a new treatment modality that introduces new genes into a cancerous cell or the surrounding tissue to cause cell death or slow the growth of the cancer. This treatment technique is very flexible, and a wide range of genes and vectors are being used in clinical trials with successful outcomes.

Side effects of gene therapy

Genetic therapy holds promise for treating many diseases, but this treatment approach can have risks. Potential risks may include certain types of cancer, allergic reactions, or damage to organs or tissues if an injection is involved.

Recent advances have made genetic therapy much safer. The FDA has approved some gene transfer therapies for clinical use in the United States as a result of improved safety.

The National Institutes of Health, which includes the NHLBI, does not conduct or fund studies on genome editing targeting sperm, eggs, or embryos in humans. These changes will be passed on to the patient’s children and may have unexpected effects.

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