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Objective:To prepare camel-derived nanoantibodies that can bind to the recombinant protein VirB12 antigen with high affinity and lay the foundation for further research.Methods:Xinjiang Bactrian camels were immunized six times with VirB12 recombinant protein, total RNA was extracted from lymphocytes isolated from peripheral blood, and the VHH gene fragment was amplified by nested PCR to construct a phage VHH display library. ELISA solid-phase affinity and enrichment methods were used for screening. After three rounds of affinity screening, the clones enriched in the second and third rounds were randomly picked out, and the binding of a nanoantibody with soluble expression to VirB12 was analyzed by ELISA. After sequence determination and multiple alignment, repetitive sequences were removed, and finally five non-redundant sequences were obtained, which were named D1, E6, H8, H9, and H10. The five identified nanoantibody genes were transformed into the WK6 strain, and the soluble expression of an intercellular substance was carried out at 16 °C. After purified expression of Ni-NTA, the binding ability and thermal stability of nanoantibodies and the antigen VirB12 protein were detected by Western Blot and ELISA.Results:Five strains of nanoantibodies were expressed in WK6 bacteria in soluble form. SDS-PAGE showed that the purity of five anti-VirB12 nanoantibodies was close to 90%, and they had high antigen-binding activity and obvious antigen-antibody concentration dependence. All four strains of nanoantibodies showed high thermal stability, and after being treated at 90 ℃, they could still retain more than 60% binding activity.Conclusions:In the study, a VHH phage display library with a capacity of 2.8×10 8 cfu/ml was constructed from Xinjiang Bactrian camel lymphocytes immunized with VirB12 recombinant protein. Five anti-VirB12 nanoantibodies with high affinity and thermal stability were obtained through solid-phase screening and enrichment and soluble monoclonal ELISA detection. These results laid the foundation for further development of VirB12 nanoantibodies.
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@#Nano-antibodies (Nbs) were first discovered in the peripheral blood of alpacas. Compared with traditional antibodies, Nbs have the characteristics of small volume, good stability, strong tissue permeability, and easy production through microbial systems, etc. They are currently the smallest known functional antigen-specific binding fragments. Therefore, Nbs have been considered as valuable proteins in recent years and widely used in many fields, such as basic research, new drug development, disease treatment and so on. This article reviews the structural and biochemical properties of Nbs and the research progress on Nbs in the fields of tumor diagnosis and treatment, as well as their application prospect.