What are the pointers to Gene Delivery

Appropriate methods to deliver DNA used in gene therapy are vital, as the targeted tissues must properly receive the appropriate genes. Gene therapy can be carried out using naked DNA delivered directly into the target cells. However, this procedure of introducing isolated DNA molecules has a very low efficiency rate. To increase the efficiency of DNA uptake by the target cells, special vectors have been engineered for gene transfer. Vectors are plasmids or viruses that are used to move recombinant DNA from one cell to another. A retrovirus is a special class of RNA viruses that can insert its nucleic acid into host cells. The viruses possess a gene for production of the reverse transcriptase, an enzyme that transcribes RNA in DNA in the host cell. Adenovirus, retrotransposons, and liposomes are other vectors used for gene transfer in gene therapy. They are all able to transfer and integrate genes into new cells. Retroviruses used in gene therapy are engineered so that any genes that are harmful to man are removed. Corrective genes are then added to replace the removed genes, and the new, modified retrovirus is then introduced into the patient.

One of the challenges for vectors is to survive the patient's immune system so they can transfer the corrective genes from their genome into the patient's cells. In general, the immune system of the human body contains molecules that immobilize viruses or other microorganisms that could infect the organism. Viruses that escape the immune system need to penetrate the cellular membrane, an additional barrier to infection. Finally, the infecting retrovirus must integrate its genome with that of the host, thereby moving the corrective genes into the genome of the infected cell. This integration happens in a random manner. It should occur in an area of DNA that is not essential to the host genome, or a risk of other complications might occur. Furthermore, the introduced gene must be transcribed and expressed for the production of the correct enzyme. With all these processes at the molecular level, gene therapy becomes a very complex procedure.

Another promising strategy, which has been used for the introduction of therapeutic genes in lung cancer treatment, is the direct injection of the corrective genes into the target area. Using this strategy, scientists have injected a drug containing the normal version of the gene, which suppresses cell tumor growth, directly into the patient's cancerous tumor. This technique bypasses the immune system reaction to the invading vector, a problem frequently associated with gene therapy. Many scientists believe that as gene therapy develops, it will be possible in the near future to easily introduce genes into patients through intramuscular injection, especially for cases of anemia, hemophilia, diabetes, and other diseases related to the circulatory system.


Tags: Bio Technology, Bio Genetics, Gene Therapy

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