ABLATION OF E2A IN RECOMBINANT ADENOVIRUSES IMPROVES TRANSGENE PERSISTENCE AND DECREASES INFLAMMATORY RESPONSE IN MOUSE-LIVER

First-generation recombinant adenoviruses that lack E1 sequences have shown tremendous promise in animal and human models of gene therapy. I mportant limitations of these vectors are that recombinant gene expres sion is transient and inflammation occurs at the site of gene transfer . Our hypothesis for generating vectors with increased persistence is that present recombinant adenoviruses express viral proteins that stim ulate cellular immune responses leading to destruction of the infected cells and repopulation of the organ with non-transgene-containing cel ls. This model predicts that further crippling of the virus will impro ve persistence and diminish pathology. We describe in this report seco nd-generation recombinant adenoviruses harboring a beta-galactosidase- expressing transgene in which a temperature-sensitive mutation has bee n introduced into the E2A gene of an E1-deleted recombinant. At nonper missive temperature, this virus fails to express late gene products, e ven when E1 is expressed in trans. The biology of this recombinant was studied in vivo in the context of mouse liver, a setting that is perm issive for adenovirus type 5 replication. Animals that received the se cond-generation virus expressed the transgene for at least 70 days, wh ereas expression of the first-generation virus was no longer than 14 d ays. In addition, the inflammatory response, as measured by infiltrati on of CD8(+) T cells, was blunted and delayed in livers infected with second-generation virus. These studies illustrate that modifications t hat disrupt structural protein expression in recombinant adenoviruses may be useful in enhancing their utility for gene therapy.