Uptake and intracellular fate of phage display vectors in mammalian cells

Receptor-mediated endocytosis is exploited in experimental systems for sele ctive delivery of genes and drugs into specific cells. To improve targeting efficiency of delivery vectors,we have used phage display technology to is olate novel ligands for endocytosed receptors. We show here that phage vect ors internalized by mammalian cells via integrin-mediated endocytosis can b e rescued by cell lysis and quantitated by infection of bacteria. Immediate ly following uptake, phage enter an intracellular compartment where they re main intact, with phage titer unaffected by the addition of chloroquine. Ph age are then translocated to a second intracellular compartment in which th ey are inactivated and their titer affected by chloroquine. Immunofluoresce nce microscopy showed an association of the second compartment with supranu clear organelles. The ability to recover internalized phage in an infectiou s form from two distinctive intracellular compartments provides a means to select novel ligands from phage libraries for targeted delivery of macromol ecules into mammalian cells. (C) 1999 Elsevier Science B.V. All rights rese rved.