Phage Display Technology for Antibody Discovery: Workflow, Libraries, and Key Advantages
I. Overview
Antibody heavy-chain (H) and light-chain (L) genes are amplified from plasma cells and assembled into an antibody library. Antibody fragments are then genetically fused to phage coat proteins and displayed on the surface of bacteriophages, generating a phage display antibody library.
Three major types of antibody libraries are commonly used:
scFv library: Composed of the variable heavy-chain domain (VH) and variable light-chain domain (VL), which are connected by a linker to form a single-chain polypeptide.
Fab library: Contains the VH-CH1 and VL-CL domains, which are associated through disulfide bonds to form a functional Fab fragment.
VHH library: Consists of the variable domain of heavy-chain-only antibodies derived from camelids.
An appropriate biopanning strategy is designed according to the characteristics of the target or screening source. After 3–4 rounds of enrichment, positive clones are identified, and their antibody sequences are determined by DNA sequencing.
II. Advantages of Phage Display Compared with Traditional Antibody Discovery Platforms
| Parameter | Immunized Serum | Hybridoma | Phage Display |
|---|---|---|---|
| Antibody Type | Polyclonal antibodies | Monoclonal antibodies | Recombinant antibodies |
| Antibody Formats | N/A | IgG (with a small number of other formats) | IgG, scFv, Fab, VHH, and others |
| Species | Multiple animal species | Mainly mice and rats | Humans and multiple animal species |
| Host Cells | N/A | Hybridoma cells | Bacteria, HEK293, CHO, etc. |
| Library Diversity | N/A | ≤10³ | 10⁷–10¹¹ |
| Typical Timeline | Several months | Several months | Several weeks |
| Workflow Complexity | Simple | Complex | Relatively simple |
| Immunization Required | Yes | Yes | Not necessarily |
| Human Antibodies | N/A | N/A | Yes |
| Production Potential | Limited | Limited | Highly scalable through recombinant expression |
| Genetic Information | N/A | Requires recloning followed by sequencing of hybridoma clones; genetic information may be lost during the process | Directly accessible by sequencing |
| Reproducibility | Limited | Limited | Highly reproducible when the original library is preserved |
| Development Potential | Limited | Limited | Broad |
III. Antibody Sources and Species
1. Camelid Antibodies
Camelids produce both heavy-chain-only antibodies (HCAbs) and conventional antibodies. In alpacas, for example, both single-domain heavy-chain antibodies (such as IgG2b and IgG2c) and conventional IgG1 antibodies are present.
In many antibody discovery programs using alpacas, the focus is primarily on heavy-chain-only antibodies, while conventional IgG1 antibodies may be overlooked.
The major immunoglobulin subclasses reported in these camelid species include:
Alpaca: IgG1a, IgG1b, IgG2b, IgG2c
Llama: IgG1a, IgG1b, IgG2b, IgG2c
Camel: IgG1a, IgG1b, IgG2a, IgG2c, IgG3
| Characteristic | Camel | Alpaca | Llama |
|---|---|---|---|
| Proportion of Single-Domain Antibodies | ~70% | ~25–45% | ~25–45% |
| Intramolecular Disulfide Bonds | ~80% | ~35% | ~20% |
| Reported Humanization Potential | 65–70% | >80% | >80% |
2. Shark-Derived Antibodies
IgNAR (immunoglobulin new antigen receptor) is a unique antibody-like molecule found in sharks. Its heavy chain contains one variable domain and five constant domains. The variable domain is connected to the constant region through a hinge-like structure.
A flexible region connects framework regions FR2 and FR3. Unlike conventional antibody structures, this region does not appear to provide substantial structural support for CDR1 and CDR3.
3.The antibody of Human
Major Antibody Classes in Humans
Humans primarily produce four major antibody classes: IgM, IgG, IgE, and IgA. IgD is also an immunoglobulin isotype, but it is present at very low levels in serum and has a less clearly defined role as a circulating antibody.
IgM is the primary antibody produced during an initial immune response. It provides a rapid and broad response to newly encountered antigens, although its individual antigen-binding affinity is generally lower than that of IgG.
IgG is the most abundant antibody class in serum. It generally has high antigen affinity and performs a wide range of immune functions, including activating immune effector cells and mediating other antibody-dependent immune responses. IgG can also cross the placenta and provide passive immune protection to the fetus.
IgE is primarily associated with immune responses to parasites and allergens. Its antiparasitic activity is particularly important against helminths and other multicellular parasites, while its dysregulated activation is also involved in allergic reactions.
IgA is the major antibody class associated with mucosal immunity. It is found in mucosal secretions and helps protect tissues and organs such as the respiratory and gastrointestinal tracts. IgA is also abundant in breast milk, where it contributes to immune protection of infants whose immune systems are still developing.
IV. MiaolingBio: Key Advantages & Resources
Established antibody library construction platform
We have a mature antibody library construction system capable of generating scFv, Fab, and VHH libraries.Customized library construction
We can construct different types of antibody libraries from multiple species according to specific customer requirements and research objectives.Comprehensive biopanning platform
We have established a complete biopanning workflow and can design customized panning strategies based on the characteristics of the target antigen or screening source.Large-scale natural antibody libraries
We maintain proprietary large-scale antibody libraries, including a natural human recombinant antibody library with a diversity of approximately 10¹¹ and a natural nanobody library with a diversity of approximately 10¹⁰.
V. QC and Characterization of the Natural Human Antibody Library
More than 600 individual monoclonal clones were randomly selected from the completed library for sequencing. The resulting sequences were analyzed and summarized, yielding the following results:
