Phage in Display

Abstract Phage display is a process by which a peptide or a protein is expressed as an exterior fusion to a surface protein of a phage particle. The peptide or protein sequence can be deduced from its encoding DNA sequence that resides in the phage particle or in a transductant. Amplification of the DNA of interest can take place by phage/transductant propagation or by polymerase chain reaction (PCR). By producing large populations of phage particles, each expressing a unique peptide or protein, peptide/protein libraries can be obtained. Peptides or proteins, interacting with defined molecular targets most often proteins can be isolated from such libraries by enrichment through repeated cycles of panning. Hence, phage display can be thought of as a ‘‘search engine’’ of protein^target interactions. The pioneering work of Smith (113) first demonstrated surface display of peptides in filamentous phage fd. This innovation was extended to peptide libraries of fd and M13 (19, 22, 108) and phagemid display was introduced (6). The display of proteins such as antibody domains and combinatorial antibody libraries soon followed (5, 59, 75). From the beginning of the 1990s phage-display-related publications have grown exponentially (128). Several reviews (some general, e.g., 58, 125; and many specialized) are available. There are numerous reports and several laboratory manuals (4) describing development and use of filamentous phage display in identification of peptide or protein interactions with simple organic compounds, antibodies, receptors, etc. Phage display is also a useful tool in protein engineering and directed evolution (44). Then there is the large sector of phage antibody display (64) and the more recent field of immune profiling and its implication for vaccine development (15, 112). Furthermore, complex targets such as cells (92) and whole tissues/organs (91) have been subjected to phage display analysis. These studies explore novel approaches for in vivo homing in gene/drug delivery (78), cancer surveillance/treatment (2, 86, 103), and imaging (127).