Refolding of scFv mini-antibodies using size-exclusion chromatography via arginine solution layer

Evaluation of scFv protein recovery from E. coli by in vitro refolding and mild solubilization process

BACKGROUND

The production of therapeutically active single chain variable fragment (scFv) antibody is still challenging in E. coli due to the aggregation propensity of recombinant protein into inclusion bodies (IBs). However, recent advancement of biotechnology has shown substantial recovery of bioactive protein from such insoluble IBs by solubilization and refolding processes. In addition, gene fusion technology has also widely been used to improve the soluble protein production using E. coli. This study demonstrates that mild-solubilization and in vitro refolding strategies, both are capable to recover soluble scFv protein from bacterial IBs, although the degree of success is greatly influenced by different fusion tags with the target protein.

RESULTS

It was observed that the most commonly used fusion tag, i.e., maltose binding protein (MBP) was not only influenced the cytoplasmic expression in E. coli but also greatly improved the in vitro refolding yield of scFv protein. On the other hand, mild solubilization process potentially could recover soluble and functional scFv protein from non-classical IBs without assistance of any fusion tag and in vitro refolding step. The recovery yield achieved by mild solubilization process was also found higher than denaturation-refolding method except while scFv was refolded in fusion with MBP tag. Concomitantly, it was also observed that the soluble protein achieved by mild solubilization process was better structured and functionally more active than the one achieved by in vitro refolding method in the absence of MBP tag or refolding enhancer.

CONCLUSIONS

Maltose binding protein tagged scFv has shown better refolding and solubility yields as compare to mild solubilization process. However, in terms of cost, time and tag free nature, mild solubilization method for scFv recovery from bacterial IBs is considerable for therapeutic application and further structural studies.

Efficient production of anti-fluorescein and anti-lysozyme as single-chain anti-body fragments (scFv) by Brevibacillus expression system

Expression of scFv in Brevibacillus choshinensis was tested using combinations of three different promoters and four different secretion signals. Two model scFv constructs, i.e., His-scFvFLU and His-scFvHEL, were successfully expressed with some of the combinations. Ni Sepharose column and size exclusion chromatography resulted in fairly pure preparations of these two proteins. The purified His-scFvFLU inhibited fluorescence from fluorescein, while the purified His-scFvHEL inhibited lysozyme activity. Relatively high yield of His-scFvFLU (∼40%) and His-scFvHEL (∼30%) was achieved with the expression and purification system described here.

Overproduction of anti-Tn antibody MLS128 single-chain Fv fragment in Escherichia coli cytoplasm using a novel pCold-PDI vector

Overproduction of recombinant proteins in Escherichia coli is often hampered by their failure to fold correctly, leading to their accumulation within inclusion bodies. To overcome the problem, a variety of techniques aimed at soluble expression have been developed including low temperature expression and/or fusion of soluble tags and chaperones. However, a general protocol for bacterial expression of disulfide bond-containing proteins has hitherto not been established. Single chain Fv fragments (scFvs) are disulfide bond-containing proteins often difficult to express in soluble forms in E. coli. We here examine in detail the E. coli expression of a scFv originating from an anti-carbohydrate MLS128 antibody as a model system. We combine three techniques: (1) tagging scFv with thioredoxin, DsbC and protein disulfide isomerase (PDI), (2) expressing the proteins at low temperature using the pCold vector system, and (3) using Origami E. coli strains with mutations in the thioredoxin reductase and glutathione reductase genes. We observed a high expression level of soluble MLS128-scFv in the Origami strain only when PDI is used as a tag. The recombinant protein retains full binding activity towards synthetic carbohydrate antigens. The developed "pCold-PDI" vector has potential for overproduction of other scFvs and disulfide-containing proteins in the Origami strains.