Ex vivo and in vivo gene transfer to the skin using replication-deficient recombinant adenovirus vectors

The skin has the potential for a variety of gene therapy applications. In addition to local delivery, it is the largest organ of the body, and highly vascular, and thus is an ideal site for systemic delivery of gene products. To evaluate the potential for adenovirus-mediated skin gene transfer, the replication-deficient recombinant adenovirus vectors Ad.RSV beta gal (coding for Escherichia coli beta-galactosidase) and Ad alpha 1AT (coding for human alpha 1-antitrypsin) were used in both ex vivo and in vivo approaches. Following in vitro infection with Ad.RSV beta gal, murine keratinocytes expressed beta-galactosidase. Parallel in vitro studies with Ad alpha 1AT documented de novo synthesis and secretion of human alpha 1AT as shown by [35S]methionine labeling and immunoprecipitation. Quantification of human alpha 1AT in the culture supernatants demonstrated 0.1-0.3 microgram human alpha 1AT secreted/ml-24 h. Evaluation of the serum of mice receiving transplants (10(5) cells/mouse) of Ad alpha 1AT-infected syngeneic keratinocytes demonstrated human alpha 1AT for at least 14 d with maximum levels of 41 ng/ml. To demonstrate the feasibility of direct adenovirus-mediated in vivo transfer of genes to the skin, Ad.RSV beta gal or Ad alpha 1AT were administered subcutaneously to mice. Histologic evaluation after 4 d demonstrated expression of beta-galactosidase in various types of skin cells. Quantification of human alpha 1AT in serum of animals infected subcutaneously with Ad alpha 1AT showed levels of 53 ng/ml at day 4, with human alpha 1AT detectable for at least 14 d. These observations support the feasibility of ex vivo and in vivo gene transfer to the skin mediated by replication-deficient adenovirus vectors.