Types of Antibody Fragments
Conventional antibodies derived fragments:
- The ~50 kDa segment known as Fab (antigen binding fragment) is made up of the heavy chain VH and CH1 domains chemically attached to the Ab light chain (VL + CL) by a disulfide bridge, ensuring monovalent and monospecific binding. A major advantage of the various Fab is that linker engineering is not required, which saves time and resources. Fabs are typically conjugated as targeting ligands for therapeutic or diagnostic tool.
- The variable domains of an Ab's heavy (VH) and light (VL) chains are joined by a linker peptide to form the single chain variable fragment, or scFv. Because of their small size, scFvs have a short half-life of roughly 0.5-2.0 hours. Similar to Fabs, scFvs are employed in the production of drug conjugates and targeted cancer imaging tracers.
Camelid heavy-chain antibodies derived fragments:
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Single domain antibody (sdAb) or heavy-chain variable (VHH), Nanobody (Nb) is the minimum known inartificial antigen-specific binding functional fragment, weighing only ~15 kDa. Nbs are highly stable, durable, and soluble. Furthermore, because of their small size, Nbs can bind epitopes that full-size Abs cannot reach by entering small cavities. Furthermore, Nbs are easily genetically modified to create multivalent and multispecific tools that are effectively expressed on a wide scale using various expression platforms.
Fig 1. Structure of Conventional and Camelid heavy-chain mAb derived fragments
Yaohai Bio-Pharma Offers One-Stop CDMO Solution for Antibody Fragments
Reference:
[1] Alonso Villela SM, et al. Production of recombinant scorpion antivenoms in E. coli: current state and perspectives. Appl Microbiol Biotechnol. 2023 Jul;107(13):4133-4152. doi: 10.1007/s00253-023-12578-1.
[2] Khilji SK, et al. Smaller size packs a stronger punch - Recent advances in small antibody fragments targeting tumour-associated carbohydrate antigens. Theranostics. 2023 May 15;13(9):3041-3063. doi: 10.7150/thno.80901.
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