Comparison of C-type Nanoantibody Produced in Different Expression Systems Implying Potential Clinical Applications

In the pharmaceutical industry, the Chinese hamster ovary cell, a type of mammalian cell, is extensively employed for the production of conventional full-length monoclonal antibodies. Nanobody is one of the most attractive directions for the development of next-generation antibody drugs. However, a suitable expression system for its manufacture has not yet been comprehensively evaluated. Previously, we proposed that the immunoglobulin constant CH2 domain could be a promising scaffold for developing C-type nanoantibodies (C-Nabs) as candidate therapeutics. Here, we used an antiviral C-Nab, which we identified previously (under review), as a model for investigation. We expressed C-Nabs without a tag in different systems, including a bacterium (C-Nab_bac), yeast (C-Nab_yeast), and mammalian cell (C-Nab_mam). After purification, the binding and neutralizing activities of C-Nabs from different expression systems are similar. Their secondary structures are rich in β-strand. The melting temperatures of C-Nab_bac (71.5 °C) and C-Nab_mam (70.2 °C) are similar, which are slightly higher than that of C-Nab_yeast (65.6 °C), while C-Nab_yeast and C-Nab_mam are more resistant to urea-induced unfolding than C-Nab_bac. C-Nab_yeast and C-Nab_mam demonstrate higher resistance to aggregation compared to C-Nab_bac. C-Nab_yeast exhibits greater resistance to enzyme digestion compared to C-Nab_bac and C-Nab_mam. Notably, when administered via intraperitoneal injection in mice, C-Nab_yeast shows superior pharmacokinetics. Overall, after comparing C-Nab proteins from various expression systems, we determined that yeast is the most suitable host for producing C-Nabs. This finding is beneficial for the production of nanobodies as potential drug candidates.