Cationic lipid formulations alter the in vivo tropism of AAV2/9 vector in lung

Physicochemical properties of gene transfer vectors play an important role in both transduction efficiency and biodistribution following airway delivery. Adeno-associated virus (AAV) vectors are currently used in many gene transfer applications; however, the respiratory epithelium remains a challenging target. We synthesized two cationic sterol-based lipids, dexamethasone-spermine (DS) and disubstituted spermine (D(2)S) for pulmonary gene targeting. Scanning and transmission electron micrographs (TEM) confirmed that AAV/lipid formulations produced submicron-sized clusters. When AAV2/9 or AAV2/6.2 were formulated with these cationic lipids, the complexes had positive zeta potential (zeta) and the transduction efficiency in cultured A549 cells increased by sevenfold and sixfold, respectively. Transduction of cultured human airway epithelium with AAV2/6.2-lipid formulations also showed approximately twofold increase in green fluorescence protein (GFP) positive cells as quantified by flow cytometry. Intranasal administration of 10(11) genome copies (GC) of AAV2/9 and AAV2/6.2 coformulated with lipid formulations resulted in an average fourfold increase in transgene expression for both vectors. Formulation of AAV2/9 with DS changed the tropism of this vector for the alveolar epithelium, resulting in successful transduction of conducting airway epithelium. Our results suggest that formulating AAV2/9 and AAV2/6.2 with DS and D(2)S can lead to improved physicochemical characteristics for in vivo gene delivery to lung.