An imposing obstacle to gene therapy is the inability to transduce all of the necessary cells
in a target organ. This certainly applies to gene transfer to the brain, especially when one
considers the challenges involved in scaling up transduction from animal models to use in
the clinic. Non-neurotropic viral gene transfer vectors (eg, adenovirus, adeno-associated
virus, and lentivirus) do not spread very far in the nervous system, and consequently these
vectors transduce brain regions mostly near the injection site in adult animals. This indicates …