732. A Novel Double-Pseudotyped Viral Vector for Gene Therapy

Abstract

A major goal of gene therapy is to achieve highly efficient and specific delivery of therapeutic genes into target cells. While current gene delivery vectors have been successful in many cases, there are still some barriers. These include low titer, low specificity, short-term expression, inconvenient vector design for different targets and inefficient targeting of certain tissues due to the lack of known receptors. For retroviral-based vectors, one limitation is the low flexibility in modifying the viral envelope glycoprotein to achieve the desired tropism since the receptor binding domain (SU) and the fusion domain (TM) are coupled. In an attempt to improve some of these aspects, we have designed a novel two-molecule targeting system that employs a lentiviral-based double-pseudotyped vector in which two different proteins are incorporated into the viral membrane to separate the receptor binding and membrane fusion functions. The first molecule, a mutant form of influenza hemagglutinin (HA) deficient for intrinsic receptor-binding function, supplies the membrane fusion machinery. The second molecule, a modified cellular surface protein that encodes two copies of the IgG-binding domain from staphylococcal protein A, binds to specific receptors on target cells through antibodies used to coat the virus. Specificity of the vector can be readily altered by employing a different antibody.