Severe combined immunodeficiency [Ref KDT 6m/e p. 843, 8441 Gene therapy Gene therapy refers to introduction of functional genetic material usually D.N.A. into target cells to replace or supplement defective genetic material. In contrast to all other therapies or drugs, gene therapy impas, new functions to a cell. Gene defects result in.fallure to synthesize a functional protein or in the synthesis of a dysfunctional protein. Equipping the cell with a normal copy of the defective gene would overcome the deficieny at the site where it is needed on a long term. Approaches in gene therapy :? Gene therapy tries to either modify or transfer the genes. Gene modification This involves correction of the defective poion of a genomic sequence or removal of the whole defective gene and its replacement by a normal copy. Gene transfer This involves introduction of genes without removing or altering the existing ones. Gene transfer is carried out in the following ways? i) Injection of naked D.N.A. ii) Transfer of generic material using virus as a carrier with D.N.A. incorporated into its genome. iii) Transfer of D.N.A. encapsulated within a liposome Applications of Gene therapy (where genetherapy is being considered) :? Cystic fibrosis (inseion of CFTR gene into respiratory epithelial cells) Severe combined immunodeficiency disease (introducing genes for adenosine deaminase) Growth hormone deficiency Familial hypercholesterelimia Lysch Nyhan syndrome Parkinsonism Alzhiemer's disease, Huntington's chorea. Familial amyotrophic lateral sclerosis, Gaucher's disease Stroke, head injury, multiple sclerosis Duchenne muscular dystrophy Prevention of restenosis of grafted coronary vessel Anemia Sickle cell anemia Haemophilia HIV infection Cancers Current status of Gene therapy (www.Fda.gov/Biologic.s bloodvaccines/cellular gene therapy) The food and drug administration has not yet approved any human gene therapy product for sale. - Current gene therapy is experimental and has not proven very successful in clinical trials. - Clear cut success in gene therapy has been achieved in Severe combined immunodeficiency (adenosine deaminase deficiency). - But there were repos that children treated with gene therapy in severe combined immunodeficiency developed leukemia. - Based on current data, the efficacy of gene transfer, .for severe combined immunodeficiency is convincing there have been no complications in the six children treated on this protocol, but longer term follow up will be required to determine whether this approach is sufficiency safe to he used in place of pegylated form of the enzyme adenosine deaminase.