¹Department of Pediatrics, University of Pennsylvania Medical Center, and Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA

Correspondence: Weidong Xiao, 310 Abramson Research Center, Children's Hospital of Philadelphia, 3516 Civic Center Boulevard, Philadelphia, PA 19104, USA. Fax: (215) 590-9939. E-mail: wxiao@mail.med.upenn.edu

Received 15 May 2002; Accepted 8 January 2003.

Abstract

Although most animal experiments with recombinant adeno-associated virus (AAV) vectors have been based on AAV serotype 2, recent studies showed that AAV vectors based on AAV serotype 1 performed more efficiently in muscle and other tissues. On the other hand, AAV2-based vectors can be readily purified by heparin column. To combine the advantages of both types of vectors, we developed a strategy to generate chimeric vectors by using a mixture of AAV helper plasmids encoding both serotypes in the transfection process. Because the AAV packaging machinery cannot distinguish between closely related AAV1 and AAV2 capsid proteins, each packaged virion contains capsid proteins from both serotypes. As expected, the resulting chimeric vectors could be purified by heparin column. Neutralizing antibody assays showed that the chimeric vectors can be inhibited by either AAV1 or AAV2 antiserum. In vivo, the chimeric vectors direct levels of expression similar to those of AAV1 in muscle or AAV2 in liver; that is, they combine the best transduction characteristics of both parent vectors. In summary, this study provides a straightforward method for combining various properties of different AAV serotypes into one vector. Potential limitations of the chimeric vectors are also discussed.