α1-Antitrypsin (α1AT) deficiency is a genetic disorder causing emphysema if serum α1AT levels are <570 μg/ml. We have shown that intrapleural administration of an AAV5α1AT vector yielded persistent therapeutic α1AT serum levels. Since anti-AAV2 and -AAV5 antibodies prevalent in humans may limit the use of these common serotypes in gene therapy, we screened 25 AAV vectors derived from humans and nonhuman primates for α1AT expression following intrapleural administration to mice. The rhesus AAVrh.10 serotype yielded the highest levels and was chosen for further study. Following intrapleural administration, 77% of total body transgene expression was in the chest wall, diaphragm, lung, and heart. Intrapleural administration of AAVrh.10α1AT provided long-term, therapeutic α1AT expression in mice, although higher doses were required to achieve therapeutic levels in female mice than in male mice. Intrapleural administration of AAVrh.10α1AT produced the same levels in AAV2/AAV5-preimmune and naive mice. In mice administered with AAV5α1AT and subsequently "boosted" with the AAVrh.10α1AT vector, serum levels were increased by 300%. These data indicate that AAVrh.10 is the most effective known AAV vector for intrapleural gene delivery and has the advantage of circumventing human immunity to AAV.