Synthetic libraries of shark vNAR domains with different cysteine numbers within the CDR3

Abstract

The variable domain of New Antigen Receptors (vNAR) from sharks, present special characteristics in comparison to the conventional antibody molecules such as: small size (12–15 kDa), thermal and chemical stability and great tissue penetration, that makes them a good alternative source as therapeutic or diagnostic agents. Therefore, it is essential to improve techniques used for the development and selection of vNAR antibodies that recognize distinct antigens. The development of synthetic antibody libraries offers a fast option for the generation of antibodies with the desired characteristics. In this work three synthetic antibody libraries were constructed; without cysteines (Cys), with one Cys and with two Cys residues within its CDR3, with the objective of determining whether the presence or absence of Cys in the CDR3 favors the isolation of vNAR clones from a synthetic library. The libraries were validated selecting against six mammalian proteins. At least one vNAR was found for each of the antigens, and a clone coming from the library without Cys in the CDR3 was selected with all the antigens. In vitro angiogenesis assay with the isolated anti-VEGF antibodies, suggest that these vNARs are capable of inhibiting in vitro angiogenesis. In silico analysis of anti-VEGF antibodies showed that vNARs from synthetic libraries could rival antibodies with affinity maturation by in silico modeling.