Gene Therapy

Gene Therapy: The techniques of molecular genetic technology can be used to treat some genetic disorders

GMO: an organism that has undergone generic engineering; it is a Genetically Modified Organism.

Liposome: Small spheres of lipid bilayer containing a functioning allele (an artificial vesicle).  They can pass through the lipid bilayer of cells and can therefore act as a vector to carry the allele into the cell.

Transgenic: An Organism that has recieved an allele of a gene from another organism, often a different species.

Gene Therapy by Adding Genes (Augmentation)

Some conditions are caused by the inheritance of faulty alleles leading to the loss of the functioning product.  This would add a copy of a functioning gene into the relevant cells so the cell functions normally.

Gene Therapy by Killing Specific Cells

Cancers can be treated by eliminating certain cells.  Using genetic techniques to make cancerous cells produce certain proteins such as cell surface antigens) that make the cell vulnerable to attack by the immune system and lead to targeted cacer treatments.

Each cell of an early embryo is a stem cell, called a germline cell as it could potentially develop into a whole new human being.  By engineering a gene into the sperm or egg you ensure that the organism grows with every cell containing a copy of the engineered gene. 

Some transgenic organisms have been genetically engineered and the finctioning allele they have recieved may be passed onto their offspring.

SCID - Severe Combined Immunodeficiency

One form is caused by the presence of a defective gene for adenosine deaminase (ADA)., leading to the build up of metabolites toxic to T Lymphocytes so complete loss of T Lymphocites occurs.  This form is a recessive inheritance pattern.

Gene Therapy trials began in 1990:

• A retrovirus, which is capable of transferring its DNA into eukaryotic cells is engineered to contain the normal human ADA gene.
• Bone marrow, containing T cells, is rmoved from the patient and exposed to the retrovirus in cell culture.  Viral infection leads to uptake of ADA gene.
• The transgenic cells formed are placed back into the patient's bone marrow where they establish a line of cells of ADA.

Trials are still on-going, but it is hoped that gene therapy wil replace bone marrow transplants as then treatment fof ADA-linked SCID.  SCID patients are also given daily injections of the enzyme adenoisine deaminase.