Plasmid DNA and recombinant adenoviruses as vectors for foreign gene transfer to the heart

Abstract

The ability to deliver genes efficiently into the cardiovascular system would be very useful for research purposes and for therapeutics. My thesis work has focused on the development and characterization of two methods of in vivo gene transfer, injection of naked plasmid DNA into cardiac muscle and gene transfer using recombinant adenoviruses. When plasmid DNA is injected into muscle it is taken up and expressed as an episome in a stable form. However, gene expression is limited to a 2mm region surrounding the injection site in a cardiac muscle. And, only {dollar}\sim{dollar}0.01% of the cardiac myocytes of the heart express the injected transgene. We have therefore turned to the use of recombinant adenoviruses to achieve high efficiency gene transfer.;We have shown that adenovirus is a highly efficient delivery system both in vitro and in vivo. The most efficient route for widespread gene transfer is by direct intracardiac injection of adenovirus. While expression from adenovirus vectors is stable when introduced into neonatal animals, it is transient in adults. We have implicated the immune system as the major cause of this phenomenon. Antibodies to adenovirus are generated as early as 5 days after infection in adult animals, while antibodies are not generated in neonates. These antibodies prevent a serotype specific block to re-administration of virus in adult animals.;By administering adenovirus to the neonatal rat, we have shown that a second injection of the same virus into the heart of the adult animals can result in stable gene expression. In order to define which components of the immune system are responsible for transient gene expression, we have used mutant mouse strains for time course studies. These studies have suggested a role of multiple components of the immune system, including antibodies and T cells in the clearance of adenovirus.;Defining the role in the immune response to adenovirus should enable us to develop new delivery systems for gene therapy. The use of both naked plasmid DNA and adenovirus will continue to enhance our ability to study whole animal gene regulation and produce phenotypic modifications in a number of organisms.