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 wide ly expressed in transplanted tissue would have important advantages in tran splantation, 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) compris ing a 15-amino acid moiety for targeting cellular integrins (derived from t he snake venom, molossin) and a 16-amino acid polylysine moiety for DNA-bin ding, has been evaluated. The 31-amino acid vector, as well as its separate 15-amino acid integrin binding and (lys),, components, were individually s ynthesized, and a monoclonal antibody was raised to the molossin peptide fo r 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 tha t the binding of polylysine-molossin and polylysine-molossin/DNA complexes involved both electrostatic and integrin-mediated interactions with the cel ls, with the electrostatic binding being sufficient for maximal binding. Ho wever, binding to cellular integrins was essential for successful gene tran sfer, Binding studies on frozen tissue sections of the rat and pig demonstr ated that the molossin peptide bound to many cell types of interest in tran splantation, but not to all. Among the negative tissues were vascular endot helium and pancreatic islets. Small species differences in tissue binding w ere noted between the rat and pig. Conclusions. This study defines the cooperative nature of the binding of th is vector system to target cells and establishes the cell types most likely to be effectively targeted for DNA transfer.