A comparison of human and murine cytomegalovirus promoters on gene expression in adult rat ocular tissues

Purpose. The present study was undertaken to evaluate the possible role of the promoter on the efficiency and duration of gene expression in adult rat ocular tissues following adenovirus gene transfer. Methods. Replication-defective adenovirus expressing beta-galactosidase (lac Z) under control of either the 0.8 kb human cytomegalovirus (HCMV) or the 1.41.b murine cytomegalovirus (MCMV) promoter were injected into the anterior chamber, vitreous cavity, or subretinal space of adult Lewis and Long Evans rats. Lac Z expression was assessed histochemically in enucleated eyes from 5-19 days after injection using the beta-galactosidase assay. Results. Expression of lac Z was noted at day 5 in the corneal endothelium, iris, trabecular meshwork, ciliary body, photoreceptors, and pigment epithelium in eyes injected with the MCMV-lac Z construct. By comparison, only the pigment epithelium demonstrated an appreciable level of lacZ expression at day 5 utilizing the HCMV-lac Z construct. MCMV promoter-driven lac Z expression was detectable in the corneal endothelium and trabecular meshwork through day 19 after anterior chamber injection. Conclusion. Marked differences in the distribution and duration of expression in the adult rat eye appear to be correlated with the type of promoter utilized. Studies currently are underway to determine the duration of MCMV-directed expression.