Optimization of transgene expression at the posttranscriptional level in neural cells: implications for gene therapy

Gene delivery vectors need to fulfill several efficacy and safety criteria before they can be used in humans. Successful clinical application requires effective transgene expression with a minimum of vector-associated toxicity. We describe the use of posttranscriptional regulatory elements in plasmid and lentiviral vectors coding for luciferase. These constructs allow high-level gene expression in both neuronal and glial cells. Of the several elements that we tested, WPRE gave the highest level of expression. Further enhancements were obtained when WPRE was combined with sequences corresponding to the 3' or 5' untranslated regions (UTR) of eukaryotic mRNAs (tau 3'UTR, TH 3'UTR, and APP 5'UTR). In neuronal cells, WPRE and both tau 3'UTR and APP 5'UTR had an additive effect on expression. The combination of the three elements increased the basal level of expression by up to 26-fold. In glial cells, WPRE and APP 5'UTR had additive effects on expression, and their combination increased expression up to 10-fold. These results provide important information regarding the development of optimal CNS gene transfer vectors not only for gene therapy but also for the study of gene function.