Successful transgene expression with serial doses of aerosolized rAAV2 vectors in rhesus macaques

Bronchoscopic microspraying of recombinant adeno-associated viral (rAAV) vectors targets high doses of vector directly to pulmonary epithelium. Single-dose endobronchial gene therapy trials have been accomplished in cystic fibrosis patients; however, repeated dosing strategies are likely essential for lifetime correction. These studies address whether serial redosing with rAAV2 vectors results in an antiserotypic response and, furthermore, whether it triggers an inflammatory response prohibitive to transgene expression. Serial redosing of 9 × 1011 infectious units of aerosolized rAAV2 vectors to rhesus macaques resulted in successful gene transfer by quantitative PCR (1.43 × 109 copies/g tissue) and transgene expression. Additionally, confocal microscopy and immunohistochemical analysis demonstrated in situ expression localized to the pulmonary epithelium. Although serial redosing did induce a heightened anti-neutralizing antibody response in sera, gene transfer prevailed with resultant expression. This study is the first to demonstrate successful gene transfer subsequent to repeated aerosolized doses of rAAV2 in immunocompetent nonhuman primates without associated inflammatory responses prohibitive to transgene expression.