The Advantages and Disadvantages of Phage Display Technology

Posted by Jerry Carter on May 24th, 2019

Phage display is a laboratory technique for the study of protein-protein, protein-peptide, and protein-DNA interactions. It makes use of bacteriophages (viruses that infect bacteria) to connect proteins with the genetic information that encodes them. Thanks to its various strengths, phage display technology has become a new research method and tool widely used in the study of protein structure. Nevertheless, it has its shortcomings, too. This article gives a brief introduction of its advantages and disadvantages.

First and foremost, through high-throughput screening, target molecules (antibodies) can be immobilized on the solid phase carrier. With the phage display peptide library (the number of phages may reach 1011 PFU), the antigen-antibody conjugated phages are adsorbed on the solid phase carrier due to the antigen-antibody specific affinity. Unbound phages remain left in the solution but can be removed by elution. Then, the specifically bound phages are eliminated also through elution. The repeated rounds of amplification and panning result in the detachment of useful genes from millions of phage clones.

Secondly, many studies have shown that the simulated epitopes can be obtained though phage display techniques. Screening the phage random peptide library by using the monoclonal antibody 9E10 leads to the acquirement of two positive clones, one of which is homologous with the natural sequence of antigens, while the other appears completely different (i.e. simulated epitopes). As such, simulated epitopes can trigger specific immune responses similar to natural epitopes. For example, mice immunized with the simulated epitopes of HBV can be induced to produce high-titer HBV antibodies.

Thirdly, the purification procedure of recombiant phages is so simple that it entails no expensive reagents or equipment. Instead, they can be purified under normal laboratory conditions. Phage vectors used for the identification of epitopes and receptors are 13 single stranded phages, which belong to mild phages. Since M13 phages do not lyse host bacteria, mature phages can be secreted into the culture medium. Many of the phage particles in the supernatant can be precipitated by centrifugation, and the addition of precipitants, which leads to the enrichment of recombiant phages containing exogenous gene products.

In addition to these appealing advantages, phage technology has its disadvantages, too. In the first place, the maximum capacity of the established peptide library can only reach 109. Thus, it’s tough to set up a large peptide library. Bacteriophage display involves bacterial transformation and phage packaging, and some display systems even require transmembrane secretion, which significantly limits the capacity and molecular diversity of the library.

Then, the diversity of the peptide library presents a great challenge. Once a phage display library is constructed, it will be hard to carry out effective in vitro mutation and recombination, thereby limiting the molecular genetic diversity of the library. Last but not the least, a few peptides cannot be displayed on the phage surface due to their strong hydrophobicity or their effect on the folding of outer membrane proteins.

As a new technology, phage display technology is confront with far more than the challenges mentioned above. However, in spite of these temporary problems, its huge application potentials can hardly be overlooked. With the improvement of phage display technology, it has played and will play an increasingly significant role in many basic and applied researches.