Gene therapy
What is gene therapy?
Genes, which are carried on chromosomes, are the basic functional units of heredity. Genes are specific sequences of bases that encode instructions on how to make proteins. Gene therapy is a technique for correcting defective genes responsible for disease development.
Several approaches for correcting faulty genes:
- Through direct replacement.
- Through homologues recombination.
- Through selective reverse mutation.
How does gene therapy work?
A carrier molecule called a vector is used to deliver the therapeutic gene to the patient’s target cells. The most common vector is a virus that has been genetically altered to carry DNA.
Target cells are infected with this viral vector. The vector then unloads the therapeutic gene into the target cell. This restores the target cell to normal state.
Different viruses used as gene therapy vectors:
- Retroviruses: Human immunodeficiency virus (HIV) is a retrovirus.
- Adenoviruses: The virus that causes the common cold is an adenovirus.
- Adeno-associated viruses
- Herpes simplex viruses: A human pathogen that causes cold sores is HSV.
There are several nonviral options for gene delivery. . The simplest method is the direct introduction of therapeutic DNA into target cells. It can also be done through chemical means . Researchers also are experimenting with introducing a 47th (artificial human) chromosome into target cells.
What is the current status of gene therapy research?
The Food and Drug Administration (FDA) has not yet approved any human gene therapy product for sale .Current gene therapy is experimental and has not proven very successful in clinical trials. In 1999, gene therapy suffered a major setback with the death of 18-year-old Jesse Gelsinger.
What factors have kept gene therapy from becoming an effective treatment for genetic disease?
- Short-lived nature: .Problems with therapeutic DNA and the rapidly dividing cells prevent gene therapy from achieving any long-term benefits.
- Immune response: The immune system’s response to therapeutic DNA is a major risk for genetherapy.
- Problems with viral vectors: They present problems like: toxicity, immune responses, etc.
- Multigene disorders: Multigene disorders such as heart disease, diabetes are difficult to treat effectively using gene therapy.