A CMV-actin-globin hybrid promoter improves adeno-associated viral vector gene expression in the arterial wallin vivo

BACKGROUND: Adeno-associated virus (AAV) vectors are attractive tools for direct intralumenal arterial gene transfer in interventional cardiology or cardiovascular surgery, but clinical application has been constrained by poor gene expression in this setting. METHODS: To improve arterial wall gene expression, a hybrid promoter consisting of a cytomegalovirus (CMV) immediate-early enhancer, a chicken beta-actin transcription start site, and a rabbit beta-globin intron (CAG promoter) was substituted for the Rous sarcoma virus (RSV) promoter in an AAV type 2 vector with an alkaline phosphatase (AP) reporter gene. RESULTS: Intralumenal transduction of rabbit carotid arteries by an AAV2 vector containing a CAG promoter resulted in gene expression in a mean of > or = 80% of the lumenal area at 14 days following exposure, compared to < or = 25% gene-expressing area with the RSV promoter-based control vector. The high prevalence of gene expression was maintained at 3, 7, 14, and 28 days. Importantly, in carotid arteries transduced with the CAG promoter, gene product expression was readily visible by the third day following transduction whereas gene expression was rarely seen before day 10 using the RSV promoter in the same animal model. On histology, AP gene expression was predominantly in vascular smooth muscle cells although some endothelial cell expression was also present. CONCLUSIONS: Substituting the CAG for the RSV promoter results in widespread gene expression, demonstrating efficient arterial wall transduction by AAV2 vectors. This finding plus the early time to gene expression hold promise for AAV vectors as agents for direct intralumenal arterial wall gene delivery during cardiovascular interventions.