Challenges of γ9δ2TCR affinity maturation when using phage display

Background: Over the past years we showed that the efficacy of αβT cells engineered to express a defined γδTCR (TEG) depends on the functional avidity of the γ9δ2TCR. We hypothesized that functional avidity mediated through γ9δ2TCR in the TEG format could be further enhanced by increasing affinity of the γ9δ2TCR. Methods: We attempted to overcome limited affinity of natural occurring γ9δ2TCRs through affinity maturation by phage display using a library containing mutations in CDR1 and CDR2 of both TCR chains. Conclusion: Affinity maturation of γ9δ2TCR by using phage display was not successful. The largest hurdle was the periplasmic expression of γ9δ2TCR constructs in E.coli which is a prerequisite for successful phage display. The underlying reason for this lack of expression was the instability of the single chain (sc)TCR format. Expression of scTCR formats in HEK293F cells yielded only 15-20% correctly folded scTCR.

Periplasmic Expression of SpyTagged Antibody Fragments Enables Rapid Modular Antibody Assembly

Antibodies are essential tools in research and diagnostics. While antibody fragments can be rapidly produced in Escherichia coli, full-length antibodies with an Fc region or antibodies modified with probes are time and labor intensive in production.SpyTag/SpyCatcher protein ligation technology could covalently attach such functionalities to antibody fragments equipped with a SpyTag. However, we found that the necessarily periplasmic expression of such antibody fragments in E. coli led to rapid cleavage of the SpyTag by proteases.Here we show how this cleavage can be prevented, making the SpyTag technology accessible for E. coli produced antibodies. We demonstrate a modular toolbox for rapid creation of synthetic IgGs, oligomerized antibodies, and antibodies with different tags or enzymatic functionalities and measure their performance in a variety of immunoassays. Furthermore, we demonstrate surface immobilization, high-throughput screening of antibody libraries, and rapid prototyping of antibodies based on modular antibody assembly.

Characterization and High-Level Periplasmic Expression of Thermostable α-Carbonic Anhydrase from Thermosulfurimonas Dismutans in Escherichia Coli for CO2 Capture and Utilization

Carbonic anhydrase (CA) is a diffusion-controlled enzyme that rapidly catalyzes carbon dioxide (CO2) hydration. CA has been considered as a powerful and green catalyst for bioinspired CO2 capture and utilization (CCU). For successful industrial applications, it is necessary to expand the pool of thermostable CAs to meet the stability requirement under various operational conditions. In addition, high-level expression of thermostable CA is desirable for the economical production of the enzyme. In this study, a thermostable CA (tdCA) of Thermosulfurimonas dismutans isolated from a deep-sea hydrothermal vent was expressed in Escherichia coli and characterized in terms of expression level, solubility, activity and stability. tdCA showed higher solubility, activity, and stability compared to those of CA from Thermovibrio ammonificans, one of the most thermostable CAs, under low-salt aqueous conditions. tdCA was engineered for high-level expression by the introduction of a point mutation and periplasmic expression via the Sec-dependent pathway. The combined strategy resulted in a variant showing at least an 8.3-fold higher expression level compared to that of wild-type tdCA. The E. coli cells with the periplasmic tdCA variant were also investigated as an ultra-efficient whole-cell biocatalyst. The engineered bacterium displayed an 11.9-fold higher activity compared to that of the recently reported system with a halophilic CA. Collectively these results demonstrate that the highly expressed periplasmic tdCA variant, either in an isolated form or within a whole-cell platform, is a promising biocatalyst with high activity and stability for CCU applications.