- 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.
- 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:
- Patients deteriorates further.
- 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.
- 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
- 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)
- 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