5 Adenovirus Vectors

Abstract

From a historical perspective, the murine retroviruses were the first recombinant viruses that were used in human gene transfer studies. As to be expected with any developing system, there were significant positive and negative aspects. Transduction of the target cells was done in an ex vivo manner that accommodated both biological and safety issues. In the ex vivo setting, it was possible to control the target cell population being transduced by methods of selection such as fluorescence-activated cell sorting, and expanding the cells in culture assured the requisite dividing cells necessary for retrovirus-mediated gene transfer. The in vitro environment excluded the presence of human complement that was known to inactivate retroviruses. While retroviral vectors integrate into the chromosomes of the targeted cells, thus developing a potential for long-term gene expression, the pattern of strictly random insertion raises the issue of insertional mutagenesis with its predisposition to oncogenicity.

To develop in vivo strategies for gene transfer that could target terminally differentiated cells, such as those in the respiratory tract or liver, it was necessary to consider the use of other viruses. It soon became obvious that adenoviruses had properties that were advantageous for in vivo gene delivery because they could transfer recombinant genes into a wide variety of dividing and nondividing cells. Because of their natural affinity for respiratory epithelium, adenoviral vectors were first used to study cystic fibrosis transmembrane conductance regulator (CFTR) gene transfer in patients with cystic fibrosis. Adenoviral vectors can be grown to much higher titers (10¹¹ pfu/ml)...