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Gene therapy; Introduction

               Gene therapy

A technique used for improving defective genes responsible for the development of disease is known as Gene therapy.  
                                                                                                                           
Introduction
Genes are the heredity’s functional unit that are composed of specific sequences and makes proteins by encoding instructions.  Genes are the proteins that get a lot of attention and perform many of the life functions. Genetic disorders may results when genes are altered and normal functioning is not performed by the encoded proteins. As medicines the use of genes which is known as Gene therapy is principally to correct genetic disorders that results due to the defective genes by one of the following approaches.  (DA, 1992) (Verma IM, 2005)

For the correction of faulty genes some of the approaches can be used by the researchers:
  1. •     Within the genome, at a nonspecific location a normal gene could be implanted to replace the non-functional gene. It is the most common approach.
  2. •         For a normal gene homologous combination an abnormal gene could be exchanged.
  3. •         Through the selective reverse mutation an abnormal gene could be renovated.
  4. •         The degree to which a gene is turned off or on (regulation) of a specific gene could be changed.

In Europe and United states, trials of majority of gene therapies are being conducted with only an uncertain number in other countries e.g. Australia.  The scope and potentials in treatment are broad in the diseases that are caused by the single gene recessive disorders (e.g. haemophilia, cystic fibrosis, sickle cell anaemia, muscular dystrophy etc.), certain viral infections e.g. AIDS and acquired genetic diseases such as cancer.  (Knoell DM, 1998) (EK, 2000)(DA, 1992)


Gene therapy history and future
Gene therapy was revealed in 1980’s few years after the segregation of genes from DNA (T, 1992) . On 14th September, 1990 the girl was treated at the National Institutes of Health’s Clinical Centre, Bathesda, Maryland. At the health centre, DR. French Anderson and his colleagues carried out the proceedings. The extraction of WBC from the body is done by them. After the establishment of genes that forms ADA, the cells were relocated back to the body of the girl. Significant improvement in the girl’s immune system was noticed. The trials on various diseases continued with gene therapy. By the means of gene therapy, the patients with melanoma, skin cancer were cured.  (Urnov F.D et al., 2010)


For the treatment of primary immunodefiencies (PID), Haematopoietic stem cell transplantation (HSCT) is now broadly used. For patients with significant disorders (adenosine deaminase deficiency (ADA)-SCID, severe combined immunodeficiency (SCID)-X1, Xchronic granulomatous disease (CGF) and Wiskott-Aldrich Syndrome (WAS), who deficient in a suitable human leukocyte antigen- HLA- matched donor, an important gene therapy has offered in alternative treatment options. (Qasim W et al., 2009) For use in applications of gene therapy, Artificial chromosomes (ACs) are highly promising vectors. (Isman O et al., 2008)




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