Topic : The Aspects of Gene Therapy Learning Objectives At the end of this topic, students will be able to: Describe gene therapy and its related processes; Compare and contrast vectors of gene delivery; Enumerate the pros and cons of gene therapy in the society. Presentation of Contents Gene therapy has become an increasingly important topic in science-related news. The aim of gene therapy is the successful integration of corrected, therapeutic DNA into the genomes of cells to alter gene expression and, in turn, protein synthesis to correct genetic diseases. Two Types of Gene Therapy 1. Somatic gene therapy, which involves introducing a "good" gene into targeted cells to treat the patient — but not the patient's future children because these genes do not get passed along to offspring. 2. Germline gene therapy, involves the introduction of corrective genes into reproductive cells (sperm and eggs) or zygotes, with the objective of creating a beneficial genetic change that is transmitted to the offspring. Vectors for 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 Vectors for Gene Delivery Fig: 11.1 Structure of Adenovirus Adenoviruses - are a group of common viruses that infect the lining of your eyes, airways and lungs, intestines, urinary tract, and nervous system. They're common causes of fever, coughs, sore throats, diarrhea, and pink eye. Source: www.andrew.cmu.edu Fig: 11.2 Structure of Retrovirus Retrovirus is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Source: http://m.wikipedia.org Fig. 11.3 Structure of Adeno-associated virus Adeno-associated virus (AAV) - is a non-enveloped virus that can be engineered to deliver DNA to target cells, and has attracted a significant amount of attention in the field, especially in clinical-stage experimental therapeutic strategies. (Source: https:// study.com) Fig. 11.4 Structure of Herpes Simplex Herpes simplex type 1 causes sores around the mouth and lips (sometimes called fever blisters or cold sores). HSV-1 can cause genital herpes, but most cases of genital herpes are caused by herpes type 2. In HSV-2, the infected person may have sores around the genitals or rectum. Source: library.open.oregonstate.edu Fig. 11.5 Structure of Naked DNA Naked DNA refers to DNA that is not associated with proteins, lipids, or any other molecule to help protect it. Naked DNA is the result of release of genetic information into the surrounding environment, such as from bursting cells. Bioethical Issues of Gene Therapy The first death associated with gene therapy occurred on September 18, 1999, at the University of Pennsylvania. Jesse Gelsinger was participating in a clinical trial, a biomedical experiment for evaluation of safety and efficiency of a therapy for a disease. Gelsinger, who was 18 years old at the time of the treatment, had a deficiency of ornithine transcarboamylase, an important enzyme in the metabolism of ammonia. Patients with this rare metabolic disorder must maintain a lowprotein diet and take a series of medicines to avoid ammonia poisoning in the blood stream. The gene therapy Gelsinger took triggered a chain reaction in his immune system, resulting in hepatic and respiratory failure, and consequently, his death four days after being treated. Effects on the Environment Although the positive impacts of gene therapy could be enormous, there are many questions raised that needs to be answered. New organisms created by genetic engineering could present an ecological problem. One cannot predict the changes that a genetically engineered species would make on the environment. The release of a new genetically engineered species would also have the possibility of causing an imbalance in the ecology of a region just exotic species would do. An accident or an unknown result could cause several problems. An accident in engineering the genetics of a virus or bacteria for example could result in a stronger type, which could cause a serious epidemic when released. This could be fatal in human genetic engineering creating problems ranging from minor medical problems, to death. Effects on Human Looking at the fact that genetic engineering employs viral vector that carries functional gene inside the human body; the repercussion are still unknown. There are no clues as to where functional genes are being placed. They may even replace the important genes, instead of mutated genes. Thus, this may lead to another health condition or disease to human. Also, as defective genes are replaced with functional gene, then it is expected that there will be a reduction in genetic diversity and if human beings will have identical genomes, the population as a whole will be susceptible to virus or any form of diseases. Antibiotic Resistance Genetic engineering often uses genes for antibiotic resistance as "selectable markers." Early in the engineering process, these markers help identify cells that have taken up foreign genes. Although they have no further use, the genes continue to be expressed in plant tissues. Most genetically engineered plant foods carry fully functioning antibiotic-resistance genes. The presence of antibiotic-resistance genes in foods could have lethal effects. Therefore, eating these foods could reduce the effectiveness of antibiotics to fight disease when these antibiotics are taken with meals. More so, the resistance genes could be transferred to human or animal pathogens, making them impervious to antibiotics. If transfer were to occur, it could aggravate the already serious health problem of antibiotic resistant disease organisms Ethical and Social Issues "Playing God" has become a strong argument against genetic engineering. Several issues have also been raised as regards the acceptance of this technology. These concerns range from ethical issues to lack of knowledge on the effects genetic engineering may have. One major concern is that once an altered gene is placed in an organism, the process cannot be reversed. The production of medicines through the use of genetically altered organisms might develop extremely infectious forms that could cause worldwide epidemics. Activity 1: Vector Voyage Direction: complete the table below. Retrovirus Disease it cause How the vector carries the genetic material Adenovirus Adenoassociated Virus Herpes Simplex Virus Naked DNA Activity 2: GENETIC DISORDERS Direction: Complete the table below. List down ten common genetic disorders. Genetic Disorder Gene/ Defect Clinical Features Activity 3: Pros and Cons Direction: Enumerate the Pros and Cons of gene therapy in human health and society Pros Human Health Society Activity 4: What does the picture show? Write a short explanation to the picture you see below Cons
