A Replication-Incompetent Adenovirus Vector with the Preterminal Protein Gene Deleted Efficiently Transduces Mouse Ears

Abstract

Adenoviruses offer great potential as gene therapy agents but are limited by the strong inflammatory response that occurs in response to the recombinant virus. Since the degree of inflammation correlates in part with the potential of the viral vector for replication, we constructed a preterminal protein (pTP) deletion mutant adenovirus type 5 vector, Ad5 dl 308 ΔpTP β-gal, that is replication incompetent due to deletion of the pTP gene and that has the E1 genes replaced by the Escherichia coli lacZ reporter gene under the control of the cytomegalovirus major immediate-early promoter. This virus was compared with a first-generation, replication-defective adenovirus vector, Ad5 dl 308β-gal, that is isogenic except that it contains a wild-type pTP gene. To examine transduction efficiency and induction of inflammation, we developed a novel system involving intradermal injection of BALB/c mouse ears. Mouse ears can be accurately measured to determine the degree of edema as an indirect measurement of inflammation. Edema and inflammation were induced in a dose- and time-dependent manner by both viruses and correlated well. LacZ activity correlated inversely with edema and inflammation. The pTP-defective vector Ad5 dl 308 ΔpTP β-gal transduced mouse ears much more efficiently and induced edema and inflammatory cell infiltration approximately 10-fold less efficiently than the first-generation vector Ad5 dl 308β-gal. The diminished inflammatory response and increased efficiency of transduction observed with Ad5 dl 308 ΔpTP β-gal indicate its promise as a gene therapy agent for other tissues. The results also demonstrate that the mouse ear model offers potential for the study of adenovirus-induced inflammation because of the ready access of the ears, the relative ease of continuous measurement, and the sensitivity to adenovirus transducing vectors.