Selection of cell specific peptides in a rat carotid injury model using a random peptide-presenting bacterial library

Cell specific peptides are possible candidates to enable targeted delivery of drugs and therapeutic genes in vivo. This study explores the utility of using a peptide-presenting bacterial library (pFliTrx) for the selection of new cell specific peptides, which bind to vascular cells of perfused tissues or organs. The balloon-injured rat carotid artery served as a model. Following perfusion of injured vascular segments with pFliTrx, 36 single clones could be identified. In radioligand binding studies, one of them, peptide P36, binds predominantly to perfused injured versus control vessel segments. It was additionally found that P36 binds with a 700-fold higher affinity in vitro to endothelial cells stimulated by treatment with LPS and TNF-alpha compared with unstimulated endothelial cells. The amino acid sequence of P36 reveals high homology to alpha(4)beta(1)-integrin, which mediates leukocyte migration from the vasculature at sites of inflammation via binding to cellular adhesion molecules, such as VCAM. In summary, this study demonstrates, that high specific peptides directed against injured vascular cells can be selected using a random peptide-presenting bacterial library.