In contrast to conventional antibodies (comprising the four subtypes IgG1, IgG2, IgG3, and IgG4), Camelid Antibodies include only three types: IgG1, IgG2, and IgG3. Among these, IgG1 is structurally similar to conventional antibodies, consisting of two heavy chains and two light chains. IgG2 and IgG3 lack the CH1 and light chain domains, hence known as heavy-chain Antibodies (hcAb), as illustrated in Figure 1.

Figure 1. Schematic Structures of Conventional Antibodies versus Heavy-chain Antibodies.

(a) Conventional aAntibodies and their Fab/scFv Antibody Formats

(b) Heavy-chain Antibodies and their VHH Antibody Formats

Heavy Chain Antibodies (Single Domain Antibodies) account for approximately 40-50% of the antibodies in alpaca serum and 60-75% in camel serum. This significant difference gives Camel VHH Antibody Libraries an inherent advantage.

Camel Antibody Libraries primarily utilize the variable region sequences of camel heavy chain antibodies, known as VHH, to construct VHH Antibody Libraries. VHH Antibodies (Single Domain Antibodies) are characterized by containing only the antigen-binding domain of the heavy chain antibody, as shown in Figure 2.

VHH Antibodies are approximately 110 amino acids (AA) in length, with SDS-PAGE indicating a molecular weight of about 15 kDa (significantly smaller than the 150 kDa of conventional antibodies), and exhibit good stability, including resistance to low pH environments. Furthermore, VHH Antibodies demonstrate high adaptability for humanization, readily meeting the requirements for engineering and sorting immune cells such as in CAR-T cell therapy.

Figure 2. Structural Schematics of Camel Heavy-chain Antibodies and VHH Antibodies.

KMD Bioscience has extensive experience in the field of Antibody Discovery and provides clients with high-quality Camel VHH Antibody Library Construction Services. Our scientists design and prepare Camel VHH Antibody Phage Display Libraries, adhering to stringent human vaccine-grade standards, following the QbD (Quality by Design) principles of biopharmaceuticals, and respecting ICH guidelines. Our service offers clients an one-stop traceability system and comprehensive documentation support, covering key stages including Antigen Design, Animal Immunization, Library Construction and Screening, and Functional Validation.

For the Camel VHH Antibody Library, we have designed a series of human immune checkpoint proteins expressed as fusions to the Fc region of camel antibodies. Combined with our mature suspension expression platforms, Freestyle 293F and Expi CHO cells, we enable clients to progress from Gene Synthesis and Vector Construction to Gram-scale Protein Expression within a short turnaround time (Visit our Protein Expression Platform for more services). 

Furthermore, our experimental results demonstrated that immunizing with target proteins directly fused to a human Fc fragment yielded superior outcomes compared to fusions with a camel Fc fragment (Contact our Technical Team for specific experimental data).

KMD Bioscience’s camels are sourced from Europe. We provide non-immunized, mature camels (24-36 months old) for Antigen Immunization. Following a standard immunization protocol, each project receives 5 to 6 immunization shots. Concurrently, we offer ELISA titer determination services during the immunization period. We ensure PBMC isolation is performed only after confirming the antiserum ELISA titer meets qualification standards.

KMD Bioscience employs the pIII protein of M13 phage for VHH Antibody Surface Display. Our scientists have constructed a phage display vector featuring dual tags (Flag and 6*His) and prepared highly competent TG1 and XL1-Blue host cells with a transformation efficiency of 10⁸. After 2 to 3 rounds of transformation and amplification, we deliver high-quality VHH Display Libraries with a functional diversity of 10⁸ to 10⁹ clones and a packaged library size of 10¹³-10¹⁶ particles/ml.

Utilizing an antigen-driven panning strategy, just 3 rounds of library screening yield 20 to 30 high-affinity phage clones. Simple IPTG induction enables the production of substantial antibody expression within 1-2 weeks, readily meeting client requirements for downstream applications such as FACS and cell activity assays.

Notes:

1. Client provides cells (camel peripheral blood lymphocytes, lymph node cells, or spleen cells): VHH Library Construction starts from step 2, requiring only 3 to 4 weeks. (Cells should be preserved in solutions like RNA later to prevent RNA degradation and shipped on blue ice).

2. Cell Lysates are prepared using TriZol solution and shipped on dry ice.