Adenoviral Vector Genome Evaluation after Intravitreal Administration

Abstract

Abstract: : Purpose: Preclinical data has indicated that expression of PEDF from an adenoviral vector has promise as an experimental treatment for ocular neovascular disease. Expression of many genes under the direction of the CMV promoter in an adenoviral vector has been reported to be transient in nature lasting approximately 2 weeks after administration into the vitreous of the eye. The loss of expression could be due to the clearance of vector genomes from the eye or the shut off of expression from the vector genomes. To address these possible mechanisms we measured the presence of vector genomes after intravitreal delivery. Methods: In this study, replication-deficient adenovirus deleted of E1, E4 and partially of E3 was delivered into the eyes of mice and the amount of vector genome was quantitated using a sensitive and specific quantitative PCR assay. A dose response for the genome in vitro and in vivo showed the sensitivity and reliability of the qPCR assay. Using this assay adenoviral vector genome was quantitated as a function of dose and time post administration. Results/Conclusions: Our findings indicate that the level of vector genome in the eye at 1-day post administration correlated directly with the amount of vector particles administered. Interestingly, these data showed the amount of vector genomes remained remarkably constant for 28 days post administration while expression dropped rapidly. From these studies the transient nature of expression from adenoviral vectors appears to be due to expression shut off. These data suggest that adenoviral vectors may provide a means to deliver proteins to the eye requiring longer-term expression for the treatment of ocular disease.

Keywords: gene transfer/gene therapy • adenovirus • gene/expression