1. ¹Department of Pediatrics, University of Pennsylvania Medical Center and The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
2. ²Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA

Correspondence: Valder R. Arruda, Division of Hematology, 302F Abramson Research Center, The Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104, USA. Fax: +1 (215) 590 3660. E-mail: arruda@email.chop.edu

Received 23 March 2005; Revised 1 August 2005; Accepted 1 August 2005.

Abstract

Identifying factors that influence gene transfer efficacy is critical for a successful gene-based clinical study. Here we demonstrate that in vivo AAV-2-mediated gene transfer is efficiently inhibited by unfractionated heparin, but not by a heparin preparation containing mainly low-molecular-weight forms (LMWH). Surprisingly, inhibitors of thrombin or factor Xa (F.Xa) significantly reduced AAV-2 transduction in a dose-dependent manner. These effects were independent of the vector promoter, transgene, or strain of mice. Expression by alternate AAV serotypes 5 and 8 was not affected by anticoagulant drugs, which suggests an AAV-2-specific effect. Moreover, AAV-2-mediated gene expression was diminished in mice with deficiency in thrombin generation (factor IX deficiency) and enhanced in mice with procoagulant phenotype due to factor V Leiden. In addition, inhibitors of F.Xa diminished adenovirus-mediated gene expression. These results demonstrated that coagulation activity itself is critical to ensure optimal viral vector transduction. Since intravascular delivery of vectors often requires the use of anticoagulants, the use of LMWH appears to be safe. These observations are of relevance for approaches using AAV-2 or adenoviral vectors, especially in early phase studies designed to identify the minimum therapeutic doses.