Gene Therapy’s Potential in Curing Genetic Disease
Gene Therapy’s Potential in Curing Genetic Disease PRG211
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Date Created: 11/11/15
Biology 100 Section 005 November 25 2013 Gene Therapy s Potential in Curing Genetic Disease Gene Therapy s Potential in Curing Genetic Disease The completion of the Human Genome Project has opened the doors leading to seemingly unlimited scienti c possibilities With a correct understanding of DNA scientists can identify speci c sections that code for positive or negative results they can enhance or duplicate the positive sections and try to remove the 39errors Genetically modi ed organisms GMO typically refer to animals or food but soon it could become commonplace for it to refer to humans Scientists have had great success in using genetics to improve the quality and often the quantity of food that humans eat on a daily basis Although controversial many advocate using this same technology on humans particularly to cure them of disabling genetic diseases Despite the dangers posed by human genetic modi cation gene therapy has the potential to cure the genetic diseases that plague humanity This report will cover the history of human gene therapy its potential for curing disease and the dangers presented by germline gene therapy Human application of gene therapy was conceptualized in the early 1970s by Theodore Friedmann and Richard Roblin 1 They recognized the potential of gene therapy but cautioned that they did not have enough information to begin human testing They proposed that more research be done to make this a safe and effective treatment and also advocated quotformulating a complete set of ethicoscienti c criteria to guide the development and clinical application of gene therapy techniquesquot 1 It was almost twenty years later that the FDA approved the rst gene therapy case in the United States Dr William French Anderson oversaw the treatment of a four yearold girl Ashanti DeSiIva with ADASCID Severe Combined Immunode ciency this genetic disease leaves its host with either a severely compromised or completely absent immune system The effects of which were often almost always fatal The procedure was a success and her immune system was partially restored gene therapy produced the needed changes but did not result in the body naturally creating new healthy cells 2 This showed that gene therapy was a viable option but that progress still needed to happen in order to achieve the maximum bene t from gene therapy Over the following years scientists continued to make advancements in gene therapy to re ne the process and nd the best possible method of administering the therapy Scientists could use many different vectors to carry the modi ed genes often modi ed viruses as knowledge of gene therapy increased scientists were able to identify which vectors were most advantageous in certain circumstances One of the biggest breakthroughs in gene therapy was the curing of Sickle Cell Disease SCD in mice Temporary treatments xes for human SCD existed as this point but this treatment was unique in that it permanently cured the mice of SCD 3 The defect in mice causing SCD is very similar to the human defect so this study showed great potential for human application However the scienti c community also experienced several setbacks the greatest being the tragic death ofJesse Gelsinger in 1999 Jesse was 18 years old and was participating in an gene therapy trial for liver problems he died four days into the trial after his body violently rejected the gene carrier 4 Also two young patients in France developed leukemia after being treated successfully for ADASCID 4 Sometimes accidents like these are the result of negligence on the part of the researcher but that does not prevent it from placing a black mark on the science as a whole In response to these tragedies the United States FDA reevaluated the procedures and protocols of gene therapy and clinical trials resumed followed the evaluation In the ensuing decade the scienti c community made great advancements in gene therapy and success has followed success The gene therapy currently in operation is referred to as somatic gene therapy as opposed to germline therapy Somatic gene therapy xes the genetic defect in the patient but does not prevent the disease from being passed on hereditarily Germline gene therapy would allow the disease to be cured in the patient and also allow the patient to pass on healthy genes to its children However currently germline gene therapy is mostly theoretical it will be discussed in greater detail later in this report Gene therapy is not hard to understand on a basic level in order to cure a genetic disease you replace a faulty gene with a working one However in practice it is much more dif cult The most troublesome aspect is having an effective vector due to their reproductive nature modi ed viruses are the ideal solution As the science has progressed different variations of viruses are discovered as being both a safer and more effective means of gene therapy After a successful treatment Dr lnder Verma stated quotAt last the successes are beginning to be more than the failures all of the hard work has come to a point where gene therapy could become a more routine modality of medicinequot 5 ADASCID was the rst disease treated by gene therapy and recent successes with the disease mark an important milestone for gene therapy Over the past two years ve young children have been treated for ADA SCID and their results are more than just a partial recovery Due to the improved SCID processes all ve patients are showing signs of full recovery without additional sessions of gene therapy 5 In 2010 a study on ADA SCID discussed the positive effect of gene therapy quotSince 2000 more than 30 ADASCID patients have been treated with gene therapy worldwide with successful outcome in most cases consisting of progressive immune reconstitution ef cient systemic detoxi cation and longterm multilineage engraftment New approaches using safer integrating vectors are being developed which may lead to safer and effective gene therapy for ADASCID and other genetic disordersquot 6 Many other diseases have been treated as well In 2011 six people were treated for hemophilia using a new type of vector AAV adeno associated virus their treatment was also a success and they are still producing the appropriate blood clotting factor 5 Another treatment combined a lentiviral vector LV with Hematopoietic Stem Cells HSC to prevent the progression of Metachromatic leukodystrophy MLD a fatal neurodegenerative lysosomal storage disease which primarily affects children The scientists found that their gene therapy protocol quotallowed stable engraftment of transduced HSCs at high levels and without evidence of vectorinduced genotoxicityquot 7 Further they suspect that their unique LV gene transfer can be used to treat multiple diseases Gene therapy has also been used to treat cancer particularly leukemia David Porter an oncologist at the University of Pennsylvania Medical Center in Philadelphia infused genetically modi ed immune cells T cells into a 65 year old leukemia patient As a result of the T cells attacking the cancer cells the patient was hospitalized after two weeks due to severe fever and fatigue One week later his bone marrow was completely free of detectable disease 8 In response he said quotWhen I was a young scientist like many I m sure I dreamed that I might make a discovery that would make a difference to mankind I never imagined that I would be part of the experimentquot 8 T cells are not a novel idea for years researchers have tried to use them to kill cancer but a main obstacle was that the T cells would quickly die off having little impact quotPorter39s group is one the rst to report results from a generation of chimeric receptors that include both an antibody to target the cancer and part of a receptor that ampli es the Tcell responsequot 8 Since this initial experiment several more patients have used this treatment with quotfabulous responsequot The National Cancer Institute has made plans to use this latest generation of T cells in trials against pancreatic cancer glioblastomas a type of brain tumor and mesothelioma a rare lung cancer 8 As the science has improved successes in gene therapy have rapidly increased Currently there are more than 700 clinical trials involving LV gene therapy in place 5 Behind this wall of success though is another problem Many of these genetic diseases are hereditary and will be passed on to the victim s children Solving this problem and curing future generations from disease is the aim of germline gene therapy In theory germline gene therapy would function similarly to somatic gene therapy except it would target the faulty genes in sex cells This is legal in the United States but many nations have prohibited human application of germline therapy due to technical and ethical concerns 9 While ideal from a medical perspective this type of gene therapy has many obstacles In practice quotgermline gene therapy is far more technically difficult than somatic cell therapy Interactions between genes and their genetic repressors and activators are complex depending in part on their precise location within a particular chromosome Technical breakthroughs are thus needed before gene replacement or repair becomes practicalquot 10 Because of this lack of technology there are great safety risks with germline therapy If done incorrectly the effects would be severe possibly lethal and would harm future generations as well as the original patient 11 Unlike somatic gene therapy germline therapy presents a serious ethical dilemma While the original intentions are to cure disease the technology can easily be used for other means It is likely that genetic enhancement will soon become the goal creating numerous social problems The rich families would have access to the exclusive technology and could use it to increase the athleticism musicality and even intelligence of their children supposing those things were at least partially affected by genes Class distinctions would arise and become entrenched in society as generations of 39superhumans were born 10 Germline gene therapy seems to be the natural extension of somatic gene therapy It would be a great scienti c and medical discovery to cure future generations from debilitating diseases However before that can happen technical obstacles need to be overcome and ethical issues need to be resolved Gene therapy as a science is still very young the processes will become more advanced and re ned and will be applied to more and more genetic diseases Somatic gene therapy is already being used to cure many terrible diseases There are still risks associated with this type of gene therapy but advances in and vector processes have lowered them substantially These advances have also lowered the controversial nature of somatic gene therapy as more and more of the public are becoming aware of its bene ts As the technology increases and becomes widespread scientists and doctors could potentially cure the world of genetic disease REFERENCES Friedmann T Roblin R Gene therapy for human genetic disease Science 197217594955 LifeSciencesFoundationorg California The rst gene therapy c2013 cited 2013 Nov 25 Available from httpwwwifesciencesfoundationorgevents The rstgenetherapyhtm TheScientistcom Murine gene therapy corrects symptoms of Sickle Cell Disease updated 2002 Mar 18 cited 2013 Nov 25 Available from httpwwwthescientistcomarticesviewarticleNo13916titleMurine GeneTherapyCorrectsSymptomsof SickIeCelDisease MedPageTodaycom Death prompts FDA to suspend arthritis gene therapy trial updated 2007 Jul 27 cited 2013 Nov 25 Available from httpwwwmedpagetodaycomGeneticsGeneraGenetics6275 NewScientistcom Bubble kid success puts gene therapy back on track updated 2013 Oct 30 cited 2013 Nov 25 Available from httpwwwnewscientistcomarticemg22029413200bubeekidsuccess putsgenetherapybackontrackhtmUpTUYMSTg5n Francesca F mmacoata B Alessandro A Update on gene therapy for adenosine deaminasede cient severe combined immunode ciency Current Opinion in Allergy amp Clinical Immunology 20101065516 Bif A Montini E Lorioli L Cesani M Fumagalli F Plati T Baldoli C Martino S Caabria A Canae S Benedicenti F Vaanti G Biasco L Leo S Kabbari K Zanetti G Rizzo W Mehta N Cicalese M Casiraghi M Boel ensJ Del Carro U Dow D Schmidt M Assanei A Neduva V Di Serio C Stupka E GardnerJ von Kalle C Bordignon C Ciceri F Rovelli A Roncarolo M Aiuti A Sessa M Naldini L Lentivira Hematopoietic stem cell gene therapy bene ts Metachromatic eukodystrophy Science 20133415879 Naturecom Cell therapy ghts leukaemia updated 2011 Aug 10 cited 2013 Nov 25 Available from httpwwwnaturecomnews2011110810fullnews2011472htm GeneticsampPublicPolicyCenterorg Human genetic modi cation c2010 cited 2013 Nov 25 Available from httpwwwdnapoicyorgpoicyinternationalphp actiondetaiampawsid38 Sade RM Khushf G Gene therapy ethical and social issues Journal South Carolina Medical Association 1998949406410 9 11 National Human Genome Research Institute Germline gene transfer updated 2006 Mar cited 2013 Nov 25 Available from httpwwwgenomegov10004764 10
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