Question

In gene therapy, a defective gene is replaced using a virus to insert a normal gene. What will make the treatment successful?

Answer 1

No immune reaction and successful recombination of the gene.

Explanation:

Engineered viruses are a promising 'tool' for gene therapy. We make use of the natural ability of viruses to introduce DNA into a cell of the host. The pathogenic DNA of the virus is replaced by the desired gene. The virus can be used as a vehicle to transport this DNA into a host cell.

To be successful, the introduced 'good gene' will have to replace the 'defect gene' in the host cell. This can happen through homologous recombination. If that process goes right, the gene is embedded into the genetic information of the cell and can be passed on to next generations of cells.

A very nice and promising technique, but there are many challenges :

• prevent an immune reaction that might kill the cell in which the DNA is introduced
• direct the virus to the right cell type; introduction into reproductive cells is for example usually not desired
• recombination has to occur at the right location in the genome. If incorporated at the wrong place it can knock down (inactivate) other genes
• after recombination the gene should also be active, but not too active i.e. product has to be generated in the right amount