Is gene therapy using retrovirus safe? What are the pros and cons?

Question

Im specifically looking at the use of gene therapy in melanoma patients.

Answer 1

Generally, cons are possible.

The vector introduced into the tissue might be recognised as a foreign particle and stimulate the immune system to mount an attack.

Secondly, the virus may mutate and regain its virulence in the patient's body

Answer 2

Gene therapy isn't safe, but you have no choice. Actually, it has no cons. All other treatments are terrible.

Answer 3

There are safety issues that have not yet been resolved, so in most cases, the answer is no, not at this time. However, the safety issues will hinge on the particular disease and on the particular retroviral vector being used to treat the disease, so these treatments will be on a case-by-case basis for the near future.

In retroviral gene therapy, the main pros are that a gene can be introduced into a retroviral vector and then the retrovirus will carry the gene into the host and integrate the gene into the host genome.  So, the cells that are infected will have a copy (or copies) of the gene integrated into their genomes and theoretically produce a normal gene product to compensate for the abnormal gene product that is being produced by the defective gene.  So, you don't have a gene floating around in the cytoplasm that can be lost.  Also, as the cell divides, the good gene is carried into all the daughter cells.

The main cons are the flip-side of the issue of integration of the retrovirus into the host genome:  1) you don't know in most cases where the retrovirus will integrate into the host genome, so this can inactivate other genes, activate other genes that shouldn't be active in a particular tissue, or even cause a cancerous cell and result in a tumor, 2) there may be multiple copies of the gene incorporated into a single cell (and more gene product production isn't always good), and these integrations may be at multiple sites in a single cell and at different sites in different cells, 3) in tissues with cells that are being lost (say, for instance, the intestinal lining), the gene may be integrated and work fine until the cells are eventually sloughed off at which point the gene will be lost, so that therapy will have to be re-done, 4) the retrovirus will infect a number of tissues and some of those tissues may not be where you want the gene product produced.

Answer 4

Using retroviruses can be done safely, it requires removing the viral nucleic acid and replacing it with genes of choice. However, right now the big up and comer in cancer is micro RNA's. It seems to me they will be easier to produce and use as well as being more specific. Exciting stuff. :)