L Advanced Drug Delivery Reviews 38 (1999) 279–289 Application of membrane-active peptides for nonviral gene delivery Ernst Wagner Institute of Biochemistry, Vienna University Biocenter, Dr. Bohrgasse 9 /3, A-1030 Vienna, Austria Abstract A variety of membrane-modifying agents including pH-specific fusogenic or lytic peptides, bacterial proteins, lipids, glycerol, or inactivated virus particles have been evaluated for the enhancement of DNA–polycation complex-based gene transfer. The enhancement depends on the characteristics of both the cationic carrier for DNA and the membrane-modifying agent. Peptides derived from viral sequences such as the N-terminus of influenza virus haemagglutinin HA-2, the N-terminus of rhinovirus HRV2 VP-1 protein, and other synthetic or natural sequences such as the amphipathic peptides GALA, KALA, EGLA, JTS1, or gramicidin S have been tested. Ligand–polylysine-mediated gene transfer can be improved up to more than 1000-fold by membrane-active compounds. Other polycations like dendrimers or polyethylenimines as well as several cationic lipids provide a high transfection efficiency per se. Systems based on these polymers or lipids are only slightly enhanced by endosomolytic peptides or adenoviruses. Electroneutral cationic lipid–DNA complexes however can be strongly improved by the addition of membrane-active peptides.  1999 Elsevier Science B.V. All rights reserved. Keywords: Polylysine; Polyethylenimine; Receptor-mediated gene transfer; Endosomal release; Amphipathic peptides; Transfection Contents 1. Introduction ............................................................................................................................................................................ 279 2. Nonviral gene delivery systems ................................................................................................................................................ 280 2.1. Naked DNA .................................................................................................................................................................... 280 2.2. Lipofection and polyfection .............................................................................................................................................. 280 2.3. Receptor-mediated gene transfer ....................................................................................................................................... 280 3. Membrane barriers in gene delivery .......................................................................................................................................... 281 4. Membrane-active peptides in polycation-based gene transfer ...................................................................................................... 282 4.1. Polylysine-based gene transfer .......................................................................................................................................... 282 4.2. Other polycations ............................................................................................................................................................. 284 5. Membrane-active peptides in lipid-based gene transfer ............................................................................................................... 285 6. Conclusions ............................................................................................................................................................................ 285 Acknowledgements ...................................................................................................................................................................... 286 References .................................................................................................................................................................................. 286 1. Introduction vices for the delivery of nucleic acid into the target cells. A gene transfer particle has to serve at least Gene therapy depends on efficient and safe de- two major delivery functions: to deliver the gene 0169-409X / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0169-409X(99)00033-2