Gene therapy principles, methods, and clinical applications

Gene Therapy

The concept of gene therapy first emerged in 1972 when the scientists were too cautious about the insertion of a foreign gene in the genomics of an individual. The use of genes for the treatment of medical conditions is known as gene therapy. The main pharmaceutical agent being used in this case is the DNA. The main principle of gene therapy is based on the fact that the genes can be supplemented or altered within the genomic makeup of an individual to make sure that the medical condition is treated at a molecular level (Li, and Huang, 2007, p. 32).

One of the most common kinds of gene therapy involves the usage of a mutated or a functional gene that replaces the nonfunctional gene being the cause of a certain medical condition. The second kind of gene therapy involves the correction of the mutated gene in which the inserted DNA or gene produces a functional protein of therapeutic importance.

After great studies, the first gene therapy experiment was approved by FDA in 1990 in U.S. when the patient named as Ashanti DeSilva suffering from Adenosine deaminase deficiency/severe combined immunodeficiency (Niidome, and Huang, 2002, p. 1648). Since her successful treatment a number of successful clinical trials have been conducted that have proven the success of gene therapy.

The current approach adopted by the scientists has focused on gene therapy being used for the diseases or conditions that are caused by single gene defects. These defects include sickle cell anemia, cystic fibrosis, muscular dystrophy, and hemophilia. Gene therapy has not been an easy target as there are a number of issues involved. The delivery of larger sections of DNA to the correct site on the genome of the individual is one of the most important issues. These days the gene therapy is mainly targeted in the correction and the treatment of genetic or hereditary defects.

Kinds of Gene Therapy

There are two major kinds of gene therapy.

1. Somatic Gene Therapy

In this form of gene therapy, the genes are inserted in the somatic cells or in some cases, the body of the effected individual. In this case, any effects that are experienced by the patient will remain restricted to the patient and will not be inherited in the future generations. Somatic gene therapy is the main kind of gene therapy that is currently being used in the clinical research where the mRNA is inserted in the body of an effected individual.

2. Germ Line Therapy

This kind of gene therapy involves the germ cells as the main target of gene therapy. The functional genes are introduced in the germ cells of the individual, which are thereby integrated in the genomes (U.S. Food and Drug Administration 2012). This therapy as compared to the somatic cell therapy can be passed on to the later generations. This therapy has been argued to be the most important kind as it can promise in combating all hereditary and genetic disorders.

Problems and Issues with Gene Therapy

One of the most important laws that explain the safety level of gene therapy is the Weismann barrier. According to Weismannism, the flow of hereditary information is always from genes to the other cells of body and not the other way round. Some lobbies who are against the principle of gene therapy have argued that the effects of inserted gene can be seen on the somatic cells of the human body as well, referred to as Soma to germline feedback. It has been argued that Weismannisem can be breached in case where the gene, instead of being inserted in the somatic cells gets inserted in the germline cells. Some of the main problems of the gene therapy include the following;

1. One of the main problems with gene therapy includes its temporary existence. For the gene therapy, to have its permanent existence is based on the fact that the cells must be rapidly dividing. As the cells rapidly divide so the long-term effects of gene therapy cannot be seen.

2. Because of the introduction of the foreign gene in the system, the immune system is evoked. Because of the fact that the immune system is activated, the possibility of gene therapy having lesser efficiency is a major possibility (Dobson, 2006, p. 284).

3. Viral vectors present many problems for the patients already suffering from various kinds of medical conditions. Some of the main issues in these cases include inflammatory responses, toxicity, gene control as well as gene targeting issues. The second important fact in these cases is that once inside the host, the virus may gain the ability to cause infection.

4. Defects and hereditary conditions that are caused by single genes can be treated by gene therapy but the defects that are based on malfunction of multiple numbers of genes cannot be treated by gene therapy. Some of these conditions include heart conditions, Alzheimer's, diabetes, and arthritis.

5. Gene therapy can cause of insertion mutagenesis. If the genes are inserted at the wrong place, for instance, at the place of tumor suppression genes, the DNA can be the cause of induction of the tumors.

Preventive Gene Therapy

The repair of defective or mutated gene being the cause of a medical condition is referred to as preventive gene therapy. There are a number of issues in association to the preventive gene therapy. One of the main issues is that as the gene identified is defective but the disease is still asymptomatic, thereby the complications cannot be expected.

Recent Upgrades in Gene Therapy

2009 is the year that marked the beginning of the delivery of genes packed in nanoparticles. In London's School of Pharmacy, the treatment of torpedo cancer has been devised based on the delivery of the therapeutic gene packed in nanoparticles. School of Ophthalmology in UCL London has successfully tested gene therapy for the treatment for inherited eye blindness. In 2007, University of Texas conducted an experiment in which a combination of two tumor suppressing genes was delivered packed in nanoparticles made of lipid. These genes have played important roles in the reduction of human lung tumors. The clinical reports have mentioned that the gene therapy has also been used to treat patients with nonfunctional myeloid cells. When these cells behave in an abnormal manner, it can lead to acute myeloid leukemia. Various gene therapy-based tests have been conducted on the guinea pigs as model animals. The gene therapy-based experiments have shown that deafness can be cured with the help of gene therapy. One of the main reasons of the deafness is the destruction of hair cells in the cochlea. A gene that has been known to stimulate hair growth in the cochlea is Atoh1 and this gene has been tested by being delivered through adenovirus. When the gene was delivered with the adenovirus, the hair regrowth in the cochleae was triggered based on which more than 80% regrowth of the hearing was repaired. New experiments are being conducted on the delivery of genes that can repair errors in the messenger RNA because of the presence of defective and nonfunctional genes. Using this technique, cystic fibrosis, thalassemia and various kinds of leukemia can be treated (Wells, 2004, p. 1365).

Conclusion

The technique of gene therapy has great potential. There are a wide scope of medical disorders and conditions that have been treated by gene therapy. These include various forms of cancer. There is no doubt about the fact that the technique of gene therapy is very expensive but the scope that the technique has is unmatched.