Protein and ligand interactions drive multiple biological processes. Phage display allowed researchers the possibility to study and interfere with these interactions in a controlled environment leading to the development of countless applications. Today, the most successful applications of phage display rest on its use as an antibody discovery, engineering, and epitope mapping tool. Check our frequently asked questions (FAQs) page about phage display. for a complete overview of all steps of this robust process for antibody generation.

Essential applications of phage display

The phage display technology was created by scientist Georg Smith in the mid-1980s with the purpose of studying protein-ligand interactions. The technique was first applied to small peptide display and later optimized for the study of larger molecules like antibodies.

In its essence, phage display is a screening methodology adapted both to liquid-phase and semi-solid phase environments against solubilized or immobilized ligands, respectively. Since phenotype is linked to genotype in phage display, the technology can be used to quickly build, amplify, and screen vast libraries of proteins (up to 1010 different clones).

Because protein/ligand interactions are essential to every biological system, the applications of phage display are numerous. But on a general level, phage display is mostly used to isolate proteins with novel or improved properties, select peptides to functionalize other molecules, or generate whole phage particles to be used directly in applications such as biosensors (e.g. for pathogen or toxin detection).

Essential applications of phage display

With the advent of molecular biology techniques, the antibody repertoire of countless host species became accessible to scientists. Following protocols of mRNA isolation, cDNA synthesis, and antibody gene amplification (VL, VH, and VHH), massive antibody repertoires could be built in vitro in very short timeframes. But only after the boom of display technologies, did the exploitation of these repertoires became feasible.

The most important applications of antibody phage display include:

  • Antibody discovery
  • Antibody engineering (i.e. affinity maturation, monoclonal and bispecific lead optimization, among others)
  • Epitope mapping

 
The most conventional application of antibody phage display is the field of lead discovery. Drawing from the high diversity of naïve antibody repertoires or from the high selectivity of their immune counterparts, phage display achieves the enrichment of binders with novel properties and high affinity towards a specific antigen.

Applications that benefit from the versatility of phage display

The unique strengths of antibody phage display in comparison to in vivo methods of antibody discovery (i.e. hybridoma, transgenic mice, etc.) include:

  • Possibility to generate novel antibodies against toxic and non-immunogenic molecules – particularly relevant for the development of anti-venom treatments or biosensors
  • Ability to refine epitope-specificity or cross-reactivity – vital for the development of sensitive diagnostic tools like Sandwich ELISA tests or complex treatment strategies like antibody cocktails against infectious diseases (where antibody pairs or mixtures need to recognize non-overlapping epitopes of the same antigen)
  • Ability to create fast response platforms – due to the short development times of antibody phage display using naïve libraries, this technique became invaluable to create fast diagnostics and detection platforms as quickly as possible
  • No limitations regarding host species – unlike the hybridoma technology, restricted to mouse and rabbit species, phage display can be used to tap into the antibody repertoire of different species like humans (invaluable for biotherapeutic development) or camelids (invaluable for biotherapeutics and diagnostic tools development)

 
In general, phage display applications extend the boundaries imposed by more conventional antibody discovery techniques like hybridomas. Hybridoma development is a time-consuming technique and the hybrid cell lines themselves can often be rather unstable.

On the contrary, phage display can be used to eliminate the need to immunize animal hosts (naïve libraries) or to perform antibody sequencing, since the sequences can be easily obtained by amplifying antibody-encoding genes from the most promising phages.

Future applications of phage display

In recent years, scientists have continued optimizing the use of phage display for alternative applications. One of the most successful of these recent applications has been the use of this technology for antibody engineering.

Affinity maturation by phage display is a well-established antibody engineering approach. It allows researchers the possibility to screen large and complex antibody mutant libraries to increase the affinity, stability, and developability of weak antibodies. However, recently some scientists have been taking this one step further by engineering biospecific antibodies.

Since phage display is driven by the principle of protein-ligand interactions, scientists have begun applying it to improve bispecific antibody assembly in vitro. Bispecific antibodies have been considered for many years as extremely challenging to produce. Because the two sets of antibody chains (VH and VL) need to be expressed and assembled in the same organism, production batches consist of mixtures of bispecific and misassembled variants.

To guide the assembly of these antibodies, scientists have ingeniously been using phage display to increase the affinity of VH and VL chains towards each other. By using this approach, it is possible to ensure that the bispecific variant with the proper VH/VL pairing is favored during expression in recombinant systems.

  1. Marintcheva, B. Phage Display. Harnessing the Power of Viruses. 2018; 133-160. doi: 10.1016/B978-0-12-810514-6.00005-2
  2. Luthra, A. et al. Human Antibody Bispecifics through Phage Display Selection. 2019; 58(13): 1701-1704. doi: 10.1021/acs.biochem.9b00037

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