Technical Article: Detailed Guide to Phage Screening-Special Topic on Phage Display Technology-Tekbiotech-Yeast and Phage Display CRO, Expert in Nano-body and Antibody Drug Development

Technical Article: Detailed Guide to Phage Screening

In the previous article, we explained phage display technology and antibody library construction using M13 as an example. Why choose M13? First, let's understand the characteristics of the main phage types.

I. Phage Selection

1. M13

M13 phages are released from host bacteria (e.g., E. coli) via a budding process without killing the cells, which is favorable for large-scale production. Their structure is simple and well-defined, as detailed in the previous article. M13 exhibits good tolerance to temperature, pH, and various detergents, facilitating screening under various stringent conditions. It is commonly used for antibody library screening and protein-protein interaction studies.

Figure 1: M13 phage lifecycle ^[1]

2. T7

The T7 phage lifecycle, from infection to host lysis and release of progeny viruses, takes only 1-2 hours, shortening the screening cycle. This makes T7 well-suited for high-throughput screening. T7 primarily displays peptides/proteins on its capsid protein 10A and is used for rapid screening of cDNA libraries and rapid identification of interacting proteins. In short, its key feature is speed.

3. T4

T4 phage features a dual display system utilizing two small outer capsid proteins, SOC and HOC. These display sites do not depend on bacterial secretion pathways or signal peptides. T4 is primarily used in multivalent vaccine development, diagnostic reagents, and screening applications requiring high environmental tolerance.

4. λ Phage

The λ phage is a temperate phage, but it releases progeny viruses by lysing the host cell. It can display toxic proteins and, compared to M13, can accommodate larger, more complex proteins. It is commonly used for constructing cDNA expression libraries and displaying large enzymes or antigens.

Summary: For antibody screening or routine peptide library screening, filamentous phage (M13) is the first choice. For displaying more complex or larger proteins, λ phage is an option. For rapid results, T7 phage offers a significant advantage. For vaccine development or screening under extreme conditions, T4 phage has unique advantages.

Figure 2: Schematic of four phage types^[2]

II. Library Selection

Once the phage is selected, the next step is choosing the library type. Libraries generally fall into three categories: immune, na?ve, and synthetic.

1. Immune Library

An immune library is constructed from mRNA extracted from activated B cells of an immunized animal. The library capacity may be smaller than a na?ve library, but it has high specificity, screening efficiency, and antibody affinity. However, the sequences are often non-human and require humanization.

2. Nave Library

A na?ve library is constructed from mRNA extracted from tissues of non-immunized, healthy donors. The diversity is extremely high, representing a broad repertoire of antibodies the organism can produce. However, affinities are typically lower, often requiring in vitro affinity maturation.

3. Synthetic Library

A synthetic library is artificially constructed entirely via chemical DNA synthesis. Based on known antibody germline frameworks, designed random mutations are introduced into the complementarity-determining regions. The library is fully controllable and designable, primarily used for generating fully human antibodies with special properties.

III. Phage Screening Workflow

Binding: Incubate the phage library with the immobilized target molecule(s).

Elution: Wash repeatedly with buffer to collect phages with strong binding affinity to the target.

Amplification: Re-infect E. coli with the eluted specific phages.

Repetition: Subject the amplified phages to additional screening rounds; typically repeat for 3-5 rounds.

Identification: After screening, perform sequencing and validate affinity by ELISA.

Figure 3: Complete workflow of phage display technology, from library construction to screening ^[3]

TekBiotech , with its core expertise in phage display and yeast display antibody development services, is committed to providing high-quality technical services to scientists worldwide, including targeted antibody discovery, antibody humanization, ADC design and conjugation, cell killing assays, and animal model experiments. These services provide robust support for our clients' research projects and the development of monoclonal antibody therapeutics for refractory diseases.

References

[1] Kehoe JW, Kay BK. Filamentous phage display in the new millennium. Chem Rev. 2005;105(11):4056-72.

[2] Hess KL, Jewell CM. Phage display as a tool for vaccine and immunotherapy development. Bioeng Transl Med. 2020;5(1):e10142.

[3] Anand T, Virmani N, Bera BC, et al. Phage Display Technique as a Tool for Diagnosis and Antibody Selection for Coronaviruses. Curr Microbiol. 2021;78(4): (Reference incomplete in original).

Previous:Frontiers in Targeted Drug Development: Comparison and Application of Multiple Peptide Screening Methods Next:None!