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Understanding Gene Therapy

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Introduction

Genes are the basic physical and functional units that enhance heredity. They are capable of encoding instructions that guide processing of proteins by the body (Yashon & Cummings, 2012). The processed proteins facilitate most of the life functions and form a better percentage of the cellular structures. When genes are altered, the encoded proteins are rendered ineffective and unable to function normally. This is what causes genetic disorder in a person. According to studies that have been conducted, almost everybody unconsciously carries some defective genes (Giacca, 2010). Lately, there has been increasing attention to the treatment of genetic metabolic diseases. These are diseases that develop as a result of defective genes that cause enzymes to be either absent or generally ineffective and inefficient. Enzymes function in the human body to catalyze metabolic reactions (Giacca, 2010). When these enzymes are ineffective, metabolic processes are slowed down or just fail to take place. This paper seeks to discuss gene therapy, illustrate examples of this treatment approach, discuss the risks and complications, associated with it, and outline some of the ethical principles that guide gene therapy as a method of treatment of genetic disorders.

Definition and Understanding of Gene Therapy

Gene therapy has been developed to help treat the genetic disorders that result from dysfunctional enzymes. Gene therapy is, thus, a treatment approach that involves replacement of faulty or absent genes with working ones so that the body is able to effectively process and produce correct enzymes or proteins and consequently be able to deal with the root cause of a genetic disease (Kelly, 2007). It is a process that involves introduction of normal and functional genes into the cells of a person, which carry the defective genes so as to enhance reconstitution of the missing protein product. It is a medical treatment process that helps in the correction of a deficient phenotype so that the normal amount of gene products is synthesized by the body. The first gene therapy trial was performed by French Anderson and R. Michael Blaese on a four year old girl in 1990  (Kelly, 2007). In order to perform gene therapy, somatic cells are modified by transferring desired gene sequences into the genome. However, for this to succeed, somatic cells are required to ensure that the genes that are inserted to correct the disorder are not carried down to the following generations. 

Examples of Gene Therapy

Gene therapy has been applied widely in the treatment of genetic disorders. This is because almost all cells in the human body contain genes. This makes genetic therapy feasible in virtually all cells of the human body. Gene therapy has been performed in the cells of the body and the ovum or sperm cells. There are, thus, two broad examples of gene therapy; the somatic cell gene therapy and the germ line cell therapy.

Somatic Cell Gene Therapy

Somatic cell gene therapy entails introduction of genes into body cells or tissues in order to treat a disease in an individual that has been medically diagnosed to have genetic associations or origin (Wintrobe & Greer, 2009). This enhances expression of an exogenous functional gene into another person’s somatic cells. This genetic therapeutic approach is considered to be non-reproductive since somatic cells, where it is involved are not reproductive cells. There is consensus that this gene cell therapy is safer than other approaches because it only has influence on the targeted cells in the patient. The introduced cells are not, therefore, passed down to the future generations. The effects of a somatic cell gene therapy end with the individual who is treated. This implies that the genetic disorders that are treated through the application of somatic cell gene therapy do not have a bearing on the children of the patient.

Somatic cell gene therapy is used to correct errors, relating to metabolism. For example, phenilketonuria has been treated through somatic cell gene therapy. This disorder results from the body’s inability to metabolize phenylalanine. The therapy facilitates elimination of the amino acid. Although this therapy is applicable, it does not address all inborn errors, related to metabolism (Kelly, 2007).  In the case of a disorder resulting from abnormal alleles for an essential enzyme that leads to deficient metabolic functions, somatic cell gene therapy has been successfully applied as a treatment strategy. In this treatment practice, a copy of gene, capable of expressing the essential enzyme and enhancing the required metabolic function, is introduced. The cloning genes that are involved in the genetic metabolic dysfunction/disorder are identified. The normal genes are, then, introduced into the prover cell within the body, especially in the area, where metabolism is required, while controlling the expression of the gene within the limits of the therapeutic and safe levels (Brown, 2010).

There are two sub-examples of the somatic cell gene therapy; the ex vivo and the in vivo. The in vivo method involves changing of the cells within the body of the patient. The genes are transferred to cells within the body of the patient. This transfer of desired genes inside the patient’s body led to the derived name of this method. The ex vivo somatic cell gene therapy involves exterior-focused therapeutic approach (Benigni & Remuzzi, 2008). The cells of the body are modified outside the body before they are transferred back into the body again. In some therapeutic trials, the cells from the patient’s own blood or even the bone marrow are removed, grown in the laboratory for some time before they are transplanted back. During this process, the cells are exposed to the virus that carries the targeted gene. The entry of the virus into the cells enhances insertion of the target gene into the DNA of the cell. The cells are, then, given time to grow in the laboratory before they are again transferred into the body of the patient through venal injection (Kelly, 2007). This example of somatic cell gene therapy is referred to as ex vivo because the cells are treated outside the body.

Germ line Gene Therapy

Germ line gene therapy is a treatment approach that involves delivery of gene to sperm or egg or directly into the cells that are responsible for their production. This example of gene therapy might help in preventing defective genes from being transferred to the subsequent generations. The act of modifying genes at the initial stages of embryonic development is also preferred since it serves as a way of correcting defective genes both in the germ line and within the cells of the body (Wintrobe & Greer, 2009).  In cases when the germ line gene therapy is carried out in the early embryologic stages like during pre-implantation diagnosis and in the vitro fertilization, genetic transfer could be affected in every cell within the developing embryo. However, there are reservations with the germ line gene therapy. This is because of its risks, especially with the possibility of a permanent therapeutic effect that may affect the following generations through genetic inheritance.

Risks, associated with Gene Therapy

The risks, associated with gene therapy, are various. These risks relate to the way, in which the genes are delivered. The normal genes that replace defective ones, in a gene therapy process, are usually delivered through carriers, which are normally vectors. Most of these vectors are viruses, which researchers use due to their unique ability to carry genetic material into the cells of a gene (Hutter, 2010). This poses a great potential for risks. To begin with, since gene therapy involves introduction of new foreign cell into the system, the body is bound to react through its immune system. The virus that is introduced into the body through gene therapy may cause the immune system to react and attack the new cell in the same way it reacts to other pathogenic and disease-causing organisms or cells. Such immune responses may not only cause complications in the body’s immunity but also lead to other medical and health complications such as inflammation, toxicity and organ failure in some extreme instances.

Gene therapy can also lead to viral spread. The process involves use of viruses to transfer the desired gene into the body. Hutter (2010) cited that since viruses have the capability of affecting more than one type of body cells, there is a possibility that viral vectors that are used in genetic transfer may end up infecting cells other than the targeted cells. All the cells that contain mutated or missing genes may, thus, be affected. This can be a very unfortunate occurrence since even the healthy cells may end up being affected by the vector-carrying virus. Thus, gene therapy may lead to viral spread, which, in turn, might cause other health complications and spread diseases or illnesses including cancer (Hutter, 2010).

Perhaps, one of the greatest risks, associated with gene therapy, is the possibility of the virus to reverse to its original form. Viruses are used to transfer the required genes into the body cells to replace the defective ones that are causing enzyme and other somatic dysfunctions. However, the viruses that are used as vectors or carriers of the desired gene may recover their initial viral and infection ability and cause diseases, once they are introduced into the body through gene therapy (Abraham, 2008). This possibility is quite unfortunate given that gene therapy in itself is originally meant to be a treatment method, which should not lead to the spread of other diseases in the process of treating another disease.

The risks of gene therapy have been registered, especially with regard to the ability of the virus to spread and induce tumor formation within the genome (Kelly, 2007). Scientists and researchers have registered their reservations and concerns that if the new genes get inserted or introduced in the wrong spot within the genome, there are chances that the insertion may cause tumor formation (Kelly, 2007). This has been observed by geneticists and scientists in some of the laboratory clinical trials. Besides, the new DNA that is introduced into the body during treatment through gene therapy may end up affecting the reproductive cells of the patient, especially where germ line gene therapy is involved. This may cause changes in the genetic composition and affect the children that are born after one is treated through gene therapy.

Complications with Gene Therapy

Although trials of gene therapy have significantly been successful, there are a few reservations that have been reported. The few complications that scientific and genetic researchers have realized with gene therapy relate to the medical and health issues that gene therapy as a treatment procedure might cause in a patient. For example, gene therapy has been associated with T-cell leukemia (Abraham, 2008). When the retroviral vector was inserted inappropriately near the proto-oncogene LMO2, the result was a proliferation of uncontrolled mature T cells, which causes T-cell leukemia in a patient. This complication is caused by the lack of both the B and T cells (Gibbs, 1996). Such a complication that result from gene therapy may expose a patient to further medical complications, including the use of bone marrow transplant that is retrieved from a histocompatible sibling of the patient. Unfortunately, this is often not easy to secure or procure. Thus, gene therapy may lead to other complications, some of which are very severe and can even be fatal.

Gene therapy may lead to interruption of important genetic sequence and harm the cell instead of resolving the genetic and cellular defects that the treatment targets. This is because the retroviruses that penetrate the immune defenses into the target cells often affect the cells in an unpredictable manner. Abraham (2008) cited that the retroviruses may even insert the therapeutic gene at unpredictable position within the cell’s DNA. This is what might lead to interruption of very important genetic sequences that might have been going on within the cell’s DNA. Even in the cases, where gene therapy succeeds, the new genes always end up in the dormant parts of the cell’s DNA (Brown, 2010). In the dormant stretches, the new genes often do not get switched on as frequent enough to be able to make the much required genetic difference in the patient who is undergoing treatment (Gibbs, 1996).

Ethical Concerns, surrounding Gene Therapy

Gene therapy is a medical treatment involving alteration of the body’s set of basic genetic messages. Since it touches on the very processes that guide life and its characteristics, this treatment approach has raised and continues to raise various ethical issues. One of the ethical concerns that gene therapy is raising is its fairness in terms of the use of the genetic information that is disclosed during the diagnosis and treatment procedures. There are concerns, relating to the use of the genetic information (Cummings, 2009). For example, many people are in a dilemma with regard to the person who should be entitled to the access to the personal genetic information of the patient and how such information will be used. There are concerns about the privacy and confidentiality of the genetic information that is retrieved in the course of gene therapy. Since it is private and personal information, pressure is piling on the need to keep genetic information very private and confidential under all circumstances.

Genetic therapy is often associated with stigmatization. The psychological impact that is created by a person’s genetic difference should, thus, be well taken care of before gene therapy is approved. For example, there are concerns about the perceptions of the society towards an individual who undergoes gene therapy. The members of the minority communities are particularly vulnerable to social stigma, associated with gene therapy. Besides, being a complex procedure that has great potentials for risks and complications, there is need to seek adequate informed consent from the patient and the family members before gene therapy is carried out on a patient. This is because gene therapy has very close link and relationship to the reproductive aspects of an individual (Cummings, 2009). The healthcare personnel, thus, need to carefully counsel the patient and the family members about the risks, the limitations and the implications of gene therapy. This ethical aspect is very essential given the clinical issues, uncertainties, complications and risks that are associated with gene therapy.

Conclusion

Gene therapy is increasingly becoming acceptable and a popular method for treatment of genetic disorders and gene-related diseases and illnesses. Although germ line gene therapy exists, it is still outlawed in most states like the entire European Union because of its implications. Somatic cell gene therapy is, however, acceptably practiced as a treatment method. However, the complications and risks that are associated with gene therapy still limit its use considerably. Thus, there is a need for scientists to evaluate further the safe, effective and efficient ways of using gene therapy as a treatment procedure for genetic disorders giving careful attention to the ethical concerns that this procedure raises. 

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