Based on extensive experience and advanced technology platforms, Creative Biolabs devotes to providing a series of solutions for novel single domain antibody (sdAb) discovery and development. Currently, we are able to provide the antibody camelization service for our customers all over the world.
Introduction of Antibody Camelization
Single domain antibodies (sdAbs) are antibody fragments derived from camelids’ heavy-chain antibody (VHH) or cartilaginous fishes’ IgNAR (VNAR). However, the non-human nature of VHHs results in immunogenicity issues so that limits their use in human immunotherapy.
In the meantime, human VH is an ideal candidate for therapeutic applications because of the least immunogenicity. However, monomeric human VH derived from conventional antibody is tend to aggregation and thus difficult to generate.
Camelization refers to the approach that key solubilizing residues from camelid sdAb are introduced into human VH to generate monomeric human VH. Furthermore, the CDR3 codons of such a ‘camelized’ VH are then randomized to obtain a synthetic library from which to retrieve binders.
Fig.1 Ribbon drawings of the human Pot VH (left) and the camelid VHH, cAb-HUL06 (right).
Sites Mutation for Camelization
Antibody gene structure and sequence analysis showed that there are several amino acid residues in antibody framework region 2 involved in the interaction of VH/VL interface, while these residues are changed in sdAbs for better characterizations. Using this feature, the hydrophobic amino acid residues at positions of human VH FR2 region can be replaced with corresponding hydrophilic amino acids in sdAbs. Studies have shown that the ‘camelized’ VH not only maintains the specificity and affinity of the original antibody but also has greatly improved stability and solubility. In addition, the introduction of an additional disulfide bridge between CDR1 and CDR3 also increases thermal stability.
Synthetic Library for Camelization
CDR3 is the major contributor to most antigen-binding sites and the stability and solubility of antibody domains are dependent on CDR3 partly. According to the site mutation, a human VH can be reshaped in its framework 2 region to mimic the VHH. Meanwhile, the synthetic library based on randomized CDR3 codons is constructed to retrieve binders. While the exclusion of CDR1 and CDR2 randomization compromises library complexity, the design simplicity of CDR3 randomization remains an attractive choice.
Features of Camelized Antibodies
Fig.2 (A) From left to right the composition of a classical antibody (left), a heavy-chain antibody (middle) and a single domain antigen-binding entity derived from a heavy-chain antibody, the VHH or single domain antibody (right). (B) The sequence organization of the VH and VHH with framework and CDR’s is schematically represented at the top of this panel. Below is the folded structure of the VH (left) and VHH domain (right with its four β-stranded sheets (back) and the five β-stranded sheets in front).
Besides the common residues mutation and library construction, our service is built to meet the customer’s project and assay-specific requirements for antibody camelization. If you are interested in our service, please do not hesitate to contact us for more details.