Incorporation of adenovirus into a ligand-based DNA carrier system results in retention of original receptor specificity and enhances targeted gene expression.

Adenovirus type 5 was modified by coupling an asialoglycoprotein-polylysine conjugate to the virus by reactions that activate carbohydrate residues. Wild-type virus modified in this manner had greatly decreased infectivity toward normally susceptible HeLa S3 (asialoglycoprotein receptor (-)) and SK Hep1 (asialoglycoprotein receptor (-)) cells leaving 91 and 86% viable, respectively, after 48 h. However, with Huh 7 (asialoglycoprotein receptor (+)) cells, modified virus retained its infectivity leaving only 19% of cells viable under identical conditions. Modified virus was complexed to DNA in the form of a plasmid, pSVHBV surf, containing the gene for hepatitis B surface antigen as a marker of gene expression. Huh 7, receptor (+), cells treated with modified wild type, and modified replication-defective d1312 virus complexed to DNA raised antigen levels by approximately 13- and 30-fold, respectively, compared with asialoglycoprotein-polylysine DNA complex alone. Competition with a large excess of an asialoglycoprotein blocked the enhancement by more than 95%. Using a beta-galactosidase marker gene, the number of cells transfected by modified virus was found to be 200-fold higher than complex alone. Yet, specificity was retained exclusively for asialoglycoprotein receptor-bearing cells. These data indicate that adenovirus can be chemically modified by coupling ligands resulting in targeted gene expression dictated specifically by receptor recognition of the attached ligand.