Tissue-binding properties of a synthetic peptide DNA vector targeted to cell membrane integrins - A possible universal nonviral vector for organ and tissue transplantation

Background. Gene delivery through a nonviral, receptor-mediated system widely expressed in transplanted tissue would have important advantages in transplantation, where gene delivery is performed ex vivo, Integrins are widely expressed cell surface receptors and can be targeted for gene delivery. Methods. A synthetic 31 amino acid DNA vector (Polylysine-molossin) comprising a 15-amino acid moiety for targeting cellular integrins (derived from the snake venom, molossin) and a 16-amino acid polylysine moiety for DNA-binding, has been evaluated. The 31-amino acid vector, as well as its separate 15-amino acid integrin binding and (lys),, components, were individually synthesized, and a monoclonal antibody was raised to the molossin peptide for these studies. Binding to cell lines and tissue sections and capacity for gene delivery were examined. Results, Flow cytometric studies with the ECV304 cell line demonstrated that the binding of polylysine-molossin and polylysine-molossin/DNA complexes involved both electrostatic and integrin-mediated interactions with the cells, with the electrostatic binding being sufficient for maximal binding. However, binding to cellular integrins was essential for successful gene transfer, Binding studies on frozen tissue sections of the rat and pig demonstrated that the molossin peptide bound to many cell types of interest in transplantation, but not to all. Among the negative tissues were vascular endothelium and pancreatic islets. Small species differences in tissue binding were noted between the rat and pig. Conclusions. This study defines the cooperative nature of the binding of this vector system to target cells and establishes the cell types most likely to be effectively targeted for DNA transfer.