Enhanced expression of transgenes from adeno-associated virus vectors withthe woodchuck hepatitis virus posttranscriptional regulatory element: Implications for gene therapy

The woodchuck hepatitis virus posttranscriptional regulatory element (WPRE) evolved to stimulate the expression of intronless viral messages. To deter mine whether this ability to enhance expression could be useful in nonviral and heterologous viral gene delivery systems, we analyzed the ability of t he WPRE to elevate the expression of a cDNA encoding the green fluorescent protein (GFP) in these contexts. We find that the WPRE can stimulate the ex pression of GFP when the gene is delivered by transfection or transduction with recombinant adeno-associated virus (AAV). Enhancement occurred both du ring transient expression and when the gene is stably incorporated into the genome of target cells. This enhancement required that the WPRE be located in cis within the GFP message, and was observed in both transformed cell l ines and primary human fibroblasts. These results demonstrate that the WPRE will be an effective tool for increasing the long-term expression of trans genes in gene therapy.