DNA AND CELL BIOLOGY Volume 23, Number 11, 2004 © Mary Ann Liebert, Inc. Pp. 742–752 A Library-Selected, Langerhans Cell-Targeting Peptide Enhances an Immune Response MICHAEL J. MCGUIRE, 1 KATHRYN F. SYKES, 1,‡ KAUSAR N. SAMLI, 1 LAURA TIMARES, 1,* MICHAEL A. BARRY, 1,† KATHERINE STEMKE-HALE, 1,‡ FRANK TAGLIAFERRI, 2 MARK LOGAN, 2 KIMBERLY JANSA, 2 AKIRA TAKASHIMA, 1,3 KATHLYNN C. BROWN, 1 and STEPHEN ALBERT JOHNSTON 1 ABSTRACT The ability to deliver antigens and immunomodulators specifically to Langerhans cells (LCs) in the skin could impact vaccine development. However, cell-specific targeting of therapeutic molecules remains a challenge in biomedicine. Using phage display technologies, we have developed a protocol that identifies peptides that me- diate uptake into target cell types. Employing this approach, we have isolated a 20-mer peptide that mediates specific uptake by immunopotent LCs. The peptide is functional outside the context of the phage and is able to deliver a nanoparticle to LCs in vitro. Although selected on cells in vitro, the peptide is able to direct anti- gens and genes to LCs in vivo. Liposomes bearing the LC targeting peptide are able to deliver a transcrip- tionally active gene to LCs in a mouse model. Furthermore, we demonstrate that a low-dose injection into mice of phage bearing the LC-targeting peptide yields faster and higher immune responses against phage-as- sociated antigens than control-phage injections. INTRODUCTION T HE NEED FOR cell-targeted delivery of biomolecules is ap- parent in many areas of medicine such as drug delivery, gene therapy, and vaccination. Directing therapeutic molecules specifically to the relevant cells in the body would have many medical advantages over undirected administration. Avoiding uptake by other cells should improve efficacy, since potentially interfering or antagonistic responses could be avoided. Unto- ward side effects and safety concerns should be alleviated if ef- fective doses could be reduced. The most common approach to cell targeting is to use a known ligand for a well-characterized cell surface molecule as a delivery vehicle and attach a bio- molecule that will have a desired therapeutic effect upon de- livery to the cell. The surface of a cell presents an array of macromolecules, which are both specific and common to dif- ferent cell types. This provides the cell with a molecular “ad- dress,” which can be used to direct cell-targeting ligands to a specific cell type. However, this approach requires previous knowledge of cell-type specific molecules or receptors (Brown, 2000). For instance, antibody-based targeting requires knowl- edge of a target-cell surface protein that is preferentially ex- pressed on the desired cell type (Forssen and Willis, 1998; Glen- nie and Johnson, 2000; Green et al., 2000). While these have been important advances, methods to rapidly isolate cell-tar- geting reagents for any cell type, regardless of the knowledge of the cell surface landscape, are still needed. One area of medicine that could be advanced by the avail- ability of robust targeting reagents is immunotherapy. Specific direction of vaccines, immunomodulating molecules, therapeu- tic drugs, and genes to immune cells could improve the effec- tiveness of these medicines. The earliest vaccines were attenu- ated versions of the pathogen itself (Plotkin and Plotkin, 1994). In this form, the vaccine targets the naturally infected cell type by definition. Since then, progress in immunology, molecular biology, and genetics has enabled the development of vaccines 1 Center for Biomedical Inventions, Department of Internal Medicine, and 3 Department of Dermatology, University of Texas Southwestern Medical Center, Dallas, Texas. 2 Valentis, Inc., The Woodlands, Texas. *Current address: Department of Dermatology, University of Alabama, Birmingham, Alabama. †Current address: Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas. ‡Current address: Macrogenics, Dallas, Texas. 742