What is gene therapy and what are its benefits and ethical issues?
Our body is made up of trillion of cells which are building blocks of all living things. There are thousands of genes within our cells that provide the necessary information required for production of specific proteins and enzymes.
Genes are physical and functional unit of heredity. The genes are located on chromosomes and they contain specific sequence of bases that encode instructions on how to make protein. Protein performs most of the cell functions and many cell structures are made up of protein. When there is any alteration, it causes dysfunction of the protein because encoded protein can’t carry out their normal functions. Genetic disorders occur due to mutation in the genome. Genes play very important role in our body. The defective genes can make us vulnerable to diseases.
Gene therapy is a technique which is used to correct defective genes that are responsible for disorder. In gene therapy, working or therapeutic gene copy is transferred into specific cells of individual to repair the faulty gene.
A gene is not directly inserted into a cell because it will not function. Instead, a carrier known as vector is genetically produced to deliver the gene at desired location. Normally specific type of viruses are used as vectors. They infect the cell and deliver the gene. These viruses are modified and their ability to cause disease is removed, so that they can’t spread diseases in humans. The examples of such viruses are retroviruses and adenoviruses. The retroviruses incorporate their genetic material into chromosome of the cell. The adenoviruses, incorporate their DNA into nucleus of the cell.
There are two ways of introduction of new genes in the body. The vector can be injected intravenously directly into desired specific tissues in the body. These are then taken up by localized individual cells. In another way, the sample of patient’s cells are removed and put in laboratory controlled environment where it is exposed to vectors. The cells are given time to multiply in the laboratory. Then the cells along with vectors are replanted to the patient, where they continue to multiply and produce the desired results. The new gene starts working properly if everything is done correctly.
There are two types of gene therapy. Somatic cell gene therapy and Germline gene therapy. In somatic cell gene therapy, the new genes are transferred into any cell other than germ cell. The modifications are restricted to the patient only and are not transferred to next generation. On the other hand, in Germline gene therapy, germ cells are modified by transferring the functional genes into genetic system. This modification is heritable and is passed on to next generations. This type of therapy is prohibited in Canada, Australia, Israel, Germany and Switzerland for applications in humans due to ethical reasons.
However there are some hurdles in gene therapy which can’t be ignored:
• The new genes which are introduced into target cells have short-lived nature. These must remain functional and stable. Rapidly multiplying nature of cells make it difficult to achieve long term results.
• When foreign and modified gene is transferred into human body, our immune system becomes alert to attack the invader. Therefore it reduces the effectiveness of gene therapy.
• Some viruses that are used as vector carry the risk of inflammation, harmfulness and targeting issues.
• Some disorders like high blood pressure, diabetes, heart diseases are affected by changes in genes; therefore gene therapy becomes complicated.
• Some gene therapies are very expensive and can’t be afforded.
Researchers are continuously evaluating the gene therapy to determine its safety before treating the disease. Because it is relatively new technique, some of its risks may be unpredictable. Therefore, medical researchers are working to make sure that gene therapy is as safe as possible.
The U.S. Food and Drug Administration (FDA), regulates all gene therapy practices in USA. The researchers who want to start clinical tests must obtain written permission from the FDA. The FDA has authority to accept or reject therapy tests if it thinks is not safe for patients. In the past, there were some deaths reported due to gene therapy, although some of them couldn’t be linked with it.
In Somatic cell gene therapy, the characteristics are not passed to next generation. However, the use of germline gene therapy is controversial. It can affect the development of a fetus in unusual ways and it can have long term effects also. Due to these ethical issues, US Government has concerns in using research funds on germline gene therapy.
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