7. DELIVERY SYSTEMS TO THE APPROPRIATE TISSUE

One major step for gene therapy relies upon methods of introducing the desired genes into the target cells. This can be achieved by using a vehicle for delivering these genes. The choice of a specific vehicle depends on a number of factors, among these factors are the following:

-   It must be efficient in delivery to the target cell

-   It must be delivered to the specific target cell

-   Whether the vehicle affects the dividing or non-dividing target cell

-   Whether the vehicle will stimulate the immune system

-   The size of the DNA that can be carried

-   The stability and longevity of the gene in the target cell.

-   The expression of the introduced gene and its rate of expression

Two main types of delivery systems are currently used.  These are viral and non-viral vectors.