• Gene Therapy is the introduction of DNA into a patient to treat a genetic disease
  • Using a vector, typically a bacteriophage, a gene is deliver to the target cell
  • The cell reads the gene and uses the information in the gene to build RNA and protein molecules
  • The proteins (or RNA) can then carry out their job in the cells.

Viral Vectors

  • Viruses can be used to deliver DNA to cells for gene therapy
  • The utilisation of viruses uses their own biological mechanisms and requires not further processing
  • Transduction: Delivery of genes by a virus
  • Transduced: the infected cells

Advantages of viral vectors:

  • Highly accurate
  • Easily embeds DNA into cell
  • Some target specific types of cells.
  • They can be modified so that they can’t replicate and destroy cells.

Disadvantages of viral vectors:

  • Carries a limited amount of genetic material. Some genes may be too big to fit into some viruses.
  • May result in immune responses in patients, leading to:
    1. Patients deteriorates further.
    2. Patient’s immune system may block the virus from delivering the gene to the patient’s cells, or it may kill the cells once the gene has been delivered.

Non-Viral Vectors

  • Some of the limitations of viral vectors can be overcome through the use of non-viral vectors
  • A common non-viral vector is the use of plasmids
  • Bacteria typically use plasmids to transfer genes among each other
  • Gene therapy plasmids can be packaged into liposomes (small membrane-wrapped packets)
  • Liposomes deliver the plasmids by fusing with cell membranes

Advantages of non-viral vectors

  • carry larger genes,
  • Most don’t trigger an immune response.

Disadvantages of non-viral vectors

  • much less efficient than viruses at getting genes into cells.
  • Virosomes are liposomes covered with viral surface proteins, they can a high carrying capacity and immune advantages of plasmids with the efficiency and specificity of viruses#
  • Viral proteins interact with proteins on the target-cell surface, helping the virosome fuse with the cell membrane and dump its contents into the cell

Somatic Therapy

  • Copies of corrected gene are inserted directly into the somatic (body cells) of the carrier
  • It does not allow disease to be passed onto future generations
  • Therapy must occur frequently (due to short term effectiveness)

Germline Therapy

  • The targeting of genes towards the egg and sperm cells (germ cells), however, which would allow the inserted geneto be passed to future generations.
  • Corrected gene is inserted into fertilised egg (via IVF)
  • IF successful, all cells of the embryo will contain the corrected gene when cells divide by mitosis
  • Germ cell therapy is permanent and also ensures offspring inherited corrected gene