Superior human hepatocyte transduction with adeno-associated virus vector serotype 7

Although therapeutic outcomes have been achieved in hemophilia patients after delivery of clotting factor genes to the liver using adeno-associated virus (AAV) vectors, it is well known that the preclinical results generated from hemophilia animal models have not been directly predictive of successful translation in humans. To address this discrepancy humanized mouse models have recently been used to predict AAV transduction efficiency for human hepatocytes. In this study we evaluated AAV vector transduction from several serotypes in human liver hepatocytes xenografted into chimeric mice. After systemic administration of AAV vectors encoding a GFP transgene in humanized mice, the liver was harvested for either immunohistochemistry staining or flow cytometry assay for AAV human hepatocyte transduction analysis. We observed that AAV7 consistently transduced human hepatocytes more efficiently than other serotypes in both immunohistochemistry assay and flow cytometry analysis. To better assess the future application of AAV7 for systemic administration in the treatment of hemophilia or other liver diseases, we analyzed the prevalence of neutralizing antibodies (NAbs) to AAV7 in sera from healthy subjects and patients with hemophilia. In the general population, the prevalence of NAbs to AAV7 was lower than that of AAV2 or AAV3B. However, a higher prevalence of AAV7 NAbs was found in patients with hemophilia. In summary, results from this study suggest that AAV7 vectors should be considered as an effective vehicle for human liver targeting in future clinical trials.