Gene therapy is the use of DNA as a pharmaceutical agent to treat disease. It derives its name from the idea that DNA can be used to supplement or alter genes within an individual's cells as a therapy to treat disease. The most common form of gene therapy involves using DNA that encodes a functional, therapeutic gene to replace a mutated gene. Other forms involve directly correcting a mutation, or using DNA that encodes a therapeutic protein drug (rather than a natural human gene) to provide treatment. 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.

Types of gene therapy

Somatic gene therapy

In somatic gene therapy, the therapeutic genes are transferred into the somatic cells (non sex-cells), or body, of a patient.

Germ line gene therapy

In germ line gene therapy, germ cells (sperm or eggs) are modified by the introduction of functional genes, which are integrated into their genomes. Germ cells will combine to form a zygote which will divide to produce all the other cells in an organism and therefore if a germ cell is genetically modified then all the cells in the organism will contain the modified gene.

Vectors in gene therapy

Gene therapy utilizes the delivery of DNA into cells, which can be accomplished by a number of methods.

Viruses

All viruses bind to their hosts and introduce their genetic material into the host cell as part of their replication cycle.

Non-viral methods

Non-viral methods can present certain advantages over viral methods, such as large scale production and low host immunogenicity. Previously, low levels of transfection and expression of the gene held non-viral methods at a disadvantage; however, recent advances in vector technology have yielded molecules and techniques that approach the transfection efficiencies of viruses.