Vectors
Vectors are the delivery vehicles used to carry new, working copies of the missing or nonworking genes into the right cells in the body. These delivery vehicles are typically made from naturally occurring viruses. Viruses are used because they are very good at getting inside of cells. However, scientists remove the DNA of the virus so that it won’t make people sick when used as a vector.
Viruses commonly studied for use as viral vectors in gene therapy include retroviruses, adenoviruses, adeno-associated viruses (AAVs), and lentiviruses. AAVs have been approved for use in gene therapy. AAVs are not to be confused with adenoviruses, a similar group of viruses, some of which can cause illness. AAVs were first discovered in 1965. These vectors are used because they can get inside many different types of cells. AAVs are not known to cause illness in people and have demonstrated safety in clinical trials.
Other viruses are also being researched as possible vectors for use in gene replacement. Because each of these viruses has a unique set of characteristics, some may be better suited than others to use as vectors for particular diseases.
Integrating viral vectors could be important for genetic diseases that occur in cells that frequently copy themselves. This would enable the new cells to keep producing the genetic information with the intended effect.
Nonintegrating viral vectors could be better suited for use in cells that don't copy themselves often. They have a reduced risk of genotoxicity and could allow for the expression of the introduced gene for a long period of time.
Current gene therapies are the cumulative result of nearly a century of genetics research.