Over-expression in Escherichia coli of the ToxA51 llama single domain antibody targeting Clostridium difficile enterotoxin A

Abstract

Single domain antibodies (sdAb) have emerged as a family of novel antibodies that have vast applications. Of particular relevance, ToxA5.l, a sdAb capable of binding to, and therefore neutralizing, Clostridium difficile toxin A (TcdA) has been developed. The antibiotic resistant version of C. difficile bacterium is of major health concern worldwide, particularly in hospital settings, causing severe gastrointestinal disorders. In this study, we investigated various parameters affecting the expression of the ToxA5.1 sdAb in E. coli TG1 and optimization of culture conditions revealed that temperature and medium buffering are critical parameters affecting small-scale expression of this recombinant protein. Large-scale expression was achieved in bioreactor at 503 mg/L of recombinant protein. Protein quantification was performed using SDS-PAGE densitometry while binding activity against TcdA was assessed via Biacore. Our studies also led to medium simplification for small-scale expression, shorter expression time and simpler purification process without impairing on the quality of the expressed recombinant protein.